Engine Room Department

Our amazing Lip seal and stern tube lubrication | An InGenious arrangement

2020-08-08T15:14:00.002+05:30

What's that red color thing?

Why there are fins in the Bottom most platform?

Why seawater isn't getting into our engine room through the gaps of the "propeller shaft" and hull?

Or to make it a heart-pumping question, (usually heart pumps at 0.14 bar)

WHAT IF your stern tube starts leaking when you are on your night-watch 1000 Kms far away from Home?

What's inside these? or which part of the machinery should I be looking out for?

Instead of saying curse words at midnight, What should be my action?

Have a look at this excellent Lip seal and stern tube lubrication

Our simple Stern Tube and lip seal arrangement

If you have tried to push an empty bucket into the water, then you know the upthrust

exerted by the bucket.

Imagine that if you drilled a hole in the side of this bucket,

trying to push it down,

the water rushes into this bucket.

and remember, the depth of the bucket is just 0.25 meters.

And now imagine our big ship, resting on the water with her cargo. Having a draft of 20 meters.

Pic showing the aft sealing arrangement - so that the water doesn't get in

Here the Green color thing called lip seal is pressed against the shaft (or liner)

The whole black color thing that holds the green color seal is called seal housing.

In our case, its called aft seal housing. as it holds aft seal.

Yes. Super easy.!

The orange line drawn here is the chrome liner.

This liner is something similar to the shaft sleeve. Called chrome liner.

And an important part of our sealing arrangement.

Why chrome liner?

we don't want any grooving on the shaft right? and its easier to replace this chrome liner.

The less known information on this is that,

The aft chrome liner is fitted on to the propeller boss.

Where is this Hollow stern tube located?

As you know, this stern tube is a simple hollow like structure

and is located at the aft end of the ship's hull.

forward part of the stern tube is supported by aft peak bulkhead and
aft end of the stern tube is supported by stern frame of the ship

Picture of aft side of the ship

Stern tube arrangement is inside a cooling water tank.

Which is always filled with seawater.

There is a filling connection as well as an overflow connection.

and we should always ensure there is enough cooling water in this water tank.

Using the sounding pipe.

2 purpose of a stern tube

Stern tube supports the stern tube bearing and holds the seal-housing arrangement.

The stern tube has to do 2 jobs

A) Withstand the load

The bearing inside the hollow stern tube (a.k.a stern tube bearing ) takes the weight of the propeller

just like all the bearings in the world.

to make it more clear, have a look at this.

Our Enormous Propeller hangs in the

↓

Stern tube bearing

↓

Stern tube bearing rests in the hollow stern tube

↓

Our hollow stern tube is supported by a stern frame arrangement in the aft.

The shaft is supported by the two bearings inside the stern tube.

Note the size of the aft bearing in the above diagram

As you can see here,

the aft bearing bush is the border one.

As it has to take the majority of propellers and his shaft's weight.

B) Holds the aft sealing housing

There is a sealing arrangement in both the ends of the stern tube.
For sealing purposes and to keep things apart.

If you have not heard about lip seal, it's just a sealing arrangement to avoid the moment of liquid into the bottom platform through the rotating shaft.

Lip seal is pressing against the shaft to prevent the entry of seawater

The shape of the seal is to be noted. It might be needed for answering questions. Or at the time of seal assembly.

And in order to avoid grooving in the shaft. we have inserted a liner on to the shaft.

This seal is held around the shaft by a spring called garter spring.

As you can see in the below diagram, the whole aft seal housing is underwater.

and the forward seal housing is in Our engine room.

Diagram shown here is the simplest sealing arrangement on a typical ship.

Just a few seals, 2 chrome liner, and header tanks.

Diagram showing of both the seals and oil flow arrangement

The only point to note here is

The aft seal housing arrangement is bolted on to the stern tube.

And the forward chrome liner is bolted to clamp ring.

(Clamp ring is just a ring which is clamped on to the shaft in the forward part)

If you ever happened to open up the line diagram in the ECR,

and turned to the Stern tube line diagram,

You could only see 6 Black dots representing these seals.

Thankfully, now you have this smart information on the stern tube and seals.

No one could takeout your dignity by asking these silly questions on

"stern tube and sealing arrangements"

Not even your CEO.

Here, only the Shaft, Propeller, and the chrome-liner are rotating.

And the lip seal and lip seal housing are stationary.

As you could see in this video down below,

The lip seal is sandwiched in between these golden colour rings. (exactly at 1:25 )

Have this video to have a complete understanding of lip seal and stern tube arrangement.

Exactly at 1:38, you can see they are fitting the whole lip seal arrangement on to the chrome liner.

Now, For your information,

The seals are numbered in order from the propeller as 1, 2, 3, 3S 4, and 5.

the "S" in the 3S stands for a supplementary seal.

( Markings in the diagram below )

If the seal 3 is leaking, oil to the seals between 2 and 3 should be shutoff.

Stern tube lip seal lubrication oil system

And one should open the Lub oil line between 3 and 3s.

So that we can keep continuing to till the next dry dock.

Or in the worst situation,

fill the gravity tank with a more viscous fluid.

There is a separate grade of oil which can maintain the lubricity even when the oil is contaminated with 40% of the seawater.

We could replace the entire stern tube oil with this high viscous oil.

So we could avoid any ingress of seawater into the engine room.

A great piece of information for you: the propeller drop is measured using a poker gauge,

It's easy-

Insert the stylus (stick) of the pocket gauge in between the lip seals 1 and 2.

by opening the plug just above it. And measure the depth.

Yes. You visualized it correctly. As the stern tube bearing gets thinner, Shaft goes down.

The readings are written on the poker gauge box as well as in the logbook.

Hope you got a Solid foundation about our stern tube and some valuable information

on this compact article.

Please do a small share if you liked the diagram and explanations

that helps me a lot in producing more awesome content.

Keep smiling. and

Have a nice day.

Comment down your thoughts.

Ciao for now!

Overhauling your favorite centrifugal pump | 6 Checks and common problems

2020-07-24T16:22:00.005+05:30

Chances are, you have seen it many times.

Unable to deliver it when, overhauling steps are asked on demand.

Here you will have the step-by-step overhauling and 5 checks to do afterwards.

Stripping down a centrifugal pump is easier than you think.

All you need is a cardboard to lay it down and some obvious tools.

And you are ready to overhaul any centrifugal pump in your Amazing professional career.

Any time You need.

Before overhauling centrifugal pump

As a thumb rule,

before dismantling or overhauling any onboard pumps, it's a good idea to check the standby pump's working condition.

and the availability of spares onboard. Like the gaskets and bearings.

The diagram below shows the cut section of the typical centrifugal pump.

Here the pump bearing is oil-cooled (oil bath) and oil is filled through an opening - red cap.

and one more thing that you could notice is the mouth ring and wear ring.

and the sealing arrangement of the pumps. whether it's a mechanical seal or has got a gland packing.

The most important step on any Pump overhaul:

If you try to open any centrifugal pump without securing it or isolating it,

you could see the Big Raging eyeballs of your second engineer. Pointed right at you.!

Especially if its the high pressure fuel line.

This same goes for cleaning your filters.

YOU need to secure the valves. both inlet and outlet. And should lock it if needed.

and never ever forget the "MEN at WORK" tag in the ECR pannel

This is the most important step to do - for yourself, your juniors your friends, and for your family.

These are the safety measures related to the overhaul of a centrifugal pump.

Steps to overhaul a centrifugal pump:

1. Yes, as we discussed, isolate the pump Electrically and Mechanically.

Switch off, close, and lock suction and delivery valve, and tag it, MEN at WORK

2. CRACK OPEN.! Yes. it should not be opened fully. the flanges should be cracked open.

In case if the valves are not holding.

If it's a huge main seawater line or any high-pressure line. it would be uncontrollable.

A) Lifting the motor Away:

3. Ensure the SWL (safe working load) of the lifting block and check shackles.

Hang the chain block above the pump and hook into the i-bolt.

4. Make markings in the coupling so that the mating surfaces still MATES after boxing back.

5. Remove motor supply cables and apply insulation tapes.

6. using chain block, hook the motor, and keep it aside.

care should be taken to avoid any banging on mating surfaces.

7. Remove external fittings from pump casing like the pressure gauges and cooling pipes to sealings

B) Going Inside the Pump Casing:

8. Remove the top cover of the casing and scrap off the gasket

9. Check mating-surfaces. And replace the gasket.

C)Removing impeller and the shaft:

10. Now the pump shaft and impeller unit can be easily removed out.

An easy overhauling video of a typical Centrifugal pump.

11. Remove impeller nut which holds the impeller on to the shaft.

12. Pull off the impeller ( from the shaft )

13.Takeout the key which holds the impeller and the shaft together.

D) Removing the mechanical sealing arrangement

14. Remove the spring and the rotating part of the mechanical seal.

The easiest working and diagram of a mechanical seal arrangement by Sriram sir

This is the easiest mechanical seal. This can be drawn easily if asked.

E) Bearing cover and bearing removal

15. Removing the bearing cover and Bearing Lock arrangement

16. Pull off that Stubborn - Bearing with the help of bearing puller.

6 Checks for your centrifugal pump:

It's nothing like a big boiler inspection. But a boiler inspection day can be beautiful too.

If you smile just after exiting from a carbon filled furnace.

Okay, It's easy.
Pump overhauling and checks can be completed just before lunch if we have to.

1. Wear ring and Impeller ring

Have a look at this short video. A bit of information on WEAR RING.

wear ring in centrifugal pump wears out and protects the casing

Not to confused this wear ring and mouth ring;

Wear ring: It is fitted into the casing to protect the casing.

Some people may also call this as casing ring.

Mouth ring: Mouth ring is fitted on the impeller to protect the impeller.

And wear ring clearances are measured using feeler gauges

And speaking of these rings,

there is a beautiful term in our merchant navy called "Lantern Ring".

comment down if you know about this. Let them know.

2. Check the trueness of the shaft and threads on it.

How do you check the trueness of the shaft?

Keep the shaft of the lathe, and turn it

the deflection should not be more than 0.05 mm

3. No Pitting marks or corrosion in the shaft.

4. No Erosion or Pitting marks on Impeller or Impeller's seating surface.

5. Check the Keys, Mechanical seal. And casing.

keys should be snug fit on the shaft.

6. Replace sealing, bearings, and gaskets (consumables)

A beautiful infographic designed for you.

Enter parts renewed and date of the overhaul in the pump maintenance log.

Procedure to start the pump after overhaul

1. Open inlet and outlet valves (centrifugal pumps can be also started with closed valves)

2. Open the air cock and purge out the air. And check for leakages

3. Turn the shaft by hand and check the freeness.

4. Reconnect motor. then remover men at work tags.

5. Reconnect cooling water.

6. Check for discharge pressure and amperage.

5 Common Problem and Answers for your pump

EEEh.!

Is your fitter trying to fix your bottom-most pump?

for the 7th time?

And if you are running up-and-down, consider scanning this.

Sure, life can be ups and downs.

but better to avoid running astronomical heights when you are onboard.

Inform these below reasons to your second engineer, for an easy appraisal.

Pumps not delivering any liquid

Primary Causes:

1. Pump not primed

2. Pump speed low

3. Chocked suction/discharge valve

4. Change in impeller direction

5. Leak in the suction line

6. Damage in Mechanical seal spring or sealing surface. Usually, The spring.

Reduced pumping rate or Lesser discharge pressure

Causes:

1. Suction line leaky

2. Low pump speed

3. Suction lift too high

4. Impeller dirty

5. Worn out mouth ring or casing ring (aka wear ring)

6. Stuffing box or mechanical seal is worn out.

Pump Fails to deliver after Running smoothly

Causes:

1. Suction line leaky

2. Leakage in sealing arrangement

3. High temperature in liquid or liquid getting heated up after a while

4. Suction side liquid gets empty

Pump overheated and draws too much power

Causes:

1. Misalignment of the pump and motor

2. Bend in Shaft

3. Stuffing box packing too tight or no cooling water for sealing arrangement

4. Too much clearance in wear rings

Excessive Vibration

Causes:

1. Loose foundation

2. Misalignment in any of the 3 axis

3. Unbalanced impeller or clogged impeller

4. Bearing Worn out

5. Bendy Shaft

If you are wondering about "misalignment in the axis" or new to pump alignment,

here is a video for you.

A simple video explaining Shaft alignment

Thanks so much for your feedback and shares.! Hope you got valuable contents on

Centrifugal pump on-a way to your bright future.

Share If you like it and More awesome articles are lined up for you.

Have a great day. Ciao for Now.!

3 Powerful priming arrangements Of all time | Onboard Centrifugal pump

2020-07-16T13:06:00.000+05:30

Is Priming Necessary in Centrifugal pumps?

Removing air out of the suction line and letting water in. That's Priming.

When you hear "SUCK" You might Recall our green educator pump on the Bottom platform.

Well, we use a similar method to SUCK out the air from the centrifugal pump casing.

"All Centrifugal pumps mounted above the level of the liquid needs to be primed"

Now, one of your one juniors comes from behind and asks you this:

Sir, Why are we priming Bilge pump? it's a Positive Displacement pump; right?

We could answer like this:

Son, Listen Up; and Inject your refined knowledge on Centrifugal pumps. Awesome.!

1. Central priming system

There is a vacuum pump

Which maintains vacuum in the vacuum chamber (Check the diagram below)
This vacuum chamber is connected to different pumps by the solenoid valve.
Whichever pump is not taking suction - when started; the solenoid valve opens and sucks the air out.

And once the pressure is developed, the Solenoid valve closes.

Each pump has an individual solenoid valve.

A self-explanatory diagram showing a vacuum pump and vacuum tank.

2. Self priming centrifugal pump

Priming With the help of a liquid ring pump.

Check the diagram below for the Liquid ring pump which is driven by the motor-

through a friction clutch arrangement.

This liquid ring pump attached here is a positive displacement pump that sucks vapor from our main centrifugal pump along with water from its own water tank.

The basic arrangement of a self-priming arrangement that's seen onboard

In short,

As long as there is water in the discharge side of the pump,

the air extraction pump isn't rotating.

Self priming arrangement of the centrifugal pump by Sriram sir

As he beautifully explains the air extraction pump and priming arrangements.

The Float check valve and filter should be always clean from marine growth, fishes, and sea monsters.

As seawater has plenty of it.

Here is another compact diagram.

This one flows easily out of memory. Consider Pinteresting this.!

An easier self priming arrangement for Centrifugal pumps

It's always a good idea to check the water level in the tank while taking rounds.

So that

Even if you have to start EM'CY fire pump from ECR, You have a peace of mind.

How Exactly Does a liquid ring pump work? What's the secret?

Working of liquid ring pump which removes air from our main centrifugal pump

3. Priming centrifugal by air Ejector

Everything works similar here,

If the pump is started, and if there is no pressure in the pressure transmitter,

The 2 Solenoid valve opens (Check the diagram below)
7 bar air keeps flowing through the air eductor
Eductor creates vacuum and takes out air from our pump casing.

And water floods into the pump casing.

then pressure transmitter senses this pressure and the solenoid valve closes.

So, why do we prime bilge our pump, which is a positive displacement pump?

- It should not run dry.

Since its a progressive cavity pump,

the rubber stator may get heated up - even if it's dry for a minute.

Do share- if you like this article

If you are having any snippets of information on priming centrifugal pump,

feel free to add them in the comment section.

Have a nice day and Thank you. Ciao for Now.!

5 Brilliant starting air line safeties to avoid an Explosion

2020-07-07T23:58:00.007+05:30

Safeties in air starting line:

In ancient times, when people refuse to listen to their storyteller at night, guess what happens?

They become lunch for the lioness.

It's important. to pay attention to the "air starting line safety" in preparatory classes. Since this could potentially turn into a serious hazard- if left unattended.

Like what happened in 1960.

Capetown Castle took the lives of 7 men as a result of starting air line explosion.

Have this short post on a way to become a reliable engineer.!

How Can the Air starting Line Explode?

Before we dive into the essential safeties, let's fire up your air starting line neurons in case if it's inactive for the last 230 days. Or if it's overwritten by your favorite song.

A simple air starting diagram for easy understanding.

Understanding this simple air start line diagram can help you at the time of manoeuvering. Or when you look up to the actual manoeuvering diagram in the future.

Now, From our fire triangle,

Fuel, air, oxygen are needed for a fire.

1. Oil carried from air compressor air acts as fuel

2. And we have plenty of oxygen from incoming air

3. And the third side is completed if the air start valve on the cylinder is leaky.

And yes. If all the ratios are correct, then there is a chance of fire or air starting line explosion.

Causes of starting airline explosion on ships

1. Leaking start air valve or air start valve stuck in an open condition.

2. Oil particles carried along with the air compressor stick to the internal surface of the pipe which has the potential for combustion.

3. If starting air valve leaks, flame or hot gases vapourize the oil and sets the oil mist on fire.

Air start valve on the cylinder

Prevention of starting air line explosion.

Here are the little things you need to do for avoiding air starting line explosions.

1. Maintenance and overhaul of air start valve.

2. Air starting valve leakage test before manoeuvering.

3. Regular draining of air bottle and air starting system.

4. Minimum cylinder lubrication to air compressor if there is a setting.

5. Regular maintenance of air compressors especially air compressor valves.

Essential air starting line safeties

1. Flame arrester in air starting line

Difference between flame arrester and a flame trap?

Flame trap: It traps flame.

Flame arrester: It traps and quenches. ie; dissipates heat by absorbing. With its high specific heat material which is copper

A typical flame arrester and dissipation of heat.

2. A safety relief valve in air starting manifold

Okay. I understand. A relief valve doesn't need an intro.

Anyway, this relief valve in air starting manifold vents to the atmosphere. Check the Diagram Below

A diagram showing internal parts of a relief valve on the air start manifold.

3. Bursting disk (Material - copper) in the air start valve

If the valve leaks, the pressure increases, and the bursting valve bursts.

ie; if the cylinder head valve is leaky, the firing pressure acts on the branch pipe. and depending upon the class. each bursting disk is located at the branch pipes. See the diagram down for better understanding

For example, let's say, for Japanese class, 1 bursting disk on the manifold and 6 flame arresters on each branch pipe. for a 6 cylinder engine

and in the case of Lloyd's, there are each bursting disks and one flame arrestor on the manifold.

Actions to be taken when bursting disk burst while running:

We could hear a sound of the leaking air coming out if the bursting disk bursts.

And we can identify in every upward and downward stroke of the piston. We can hear the sound through the burst out bursting disk which comes from the leaky cylinder head valve. Gotcha.!

Some might say that by checking at the air bottle pressure we could know, but the automatic air starting valve will close - while the engine is running.

PS: Not to confuse with Automatic air start valve and air start valve on the cylinder.

What action will you take if Bursting disk Bursts?

Lock the bursting disk

1. Slacken the butterfly nut.

2. Turn the perforated cover.

3. A perforated cylinder Inside the perforated cover so that holes get covered.

If you are in the middle of the manoeuvering, replacing the air start valve is not possible. so, cut-off fuel pump to that specific unit.

Slacken the wing nut. There are holes in the cylinder as well. so when you turn, there is a mismatch between holes and the cover. so that the air will not come out. ( ie, Turn the perforated cover on the perforated cylinder)

You still can continue manoeuvering but reduced load.

4. Non return valve in air starting line

Non return valve is incorporated in the Automatic air start valve.

All 4 safety devices shown in the air starting diagram.

5. Thermal patch in air starting line

It's just a sticker on the branch pipe to the cylinder head valve line.

When starting air valve becomes leaky, the branch pipe becomes hot hot hot and colour of thermal patch changes. so that you don't have to touch and feel it. Just by looking itself, one can understand that the air starting valve is leaky.

PS: Turning gear interlock and reversing interlock aren't safeties for the air starting line. these are safeties for the engine.

How do you test air starting valve for leakage?

1. While running - Air leakage test

By touching the nearer pipe or by the thermal path that we discussed earlier.

2. While stopped condition - Air leakage test

Shut the valve to the air distributor (valve shown near to the relief valve in the above diagram)

if you do this, no pilot air opens the air start valve. and all the air start valve remain closed position.

At this point, I highly recommend you to watch this video by Sriram sir. As he beautifully explains air starting valve working.

Video explaining how air starting valve worksNow, as we were discussing,
1. Shut the valve to the air distributor so that all the air start valves on the cylinder head remain closed.
2. Open all the indicator cocks.
3. Disengage the turning gear.
4. Give an air kick.
5. If air leaks through the indicator cock, it is leaky. Change the air starting valve.

Air starting valve is a great friend. It helps in starting the main engine and crash stopping.

I'm working on a detailed Man B&W Manoeuvering diagram for you.

Comment down if you still got any doubts. And as always, We are happy to help you.

I hope you got a complete understanding of the starting air line and its safeties.

Share if you like this content among your friends. That helps me a lot.

Thank you and have a nice day.!

A quick guide on filing refrigerant | Onboard Essentials

2020-07-03T23:51:00.009+05:30

Refrigerant Filling onboard:

Ever wondered what your second engineer does with your refrigeration plant? With a special spanner?

Yes. Refrigerant charging.! Have this quick and short step-by-step guide for refrigerant charging.

One day you might have to fill some refrigerant just before the Lunch break. Read on.

Liquid refrigerant charging is done through a liquid charging valve at the high-pressure side.
as it is the faster method.

And this refrigerant charging valve is located at the bottom of the drier connection.
check the Basics of a refrigeration diagram for an easy understanding.

Basic Refrigeration diagram showing a filling valve.

Refrigerant filling is a simple process and easy to understand.

3 Things to keep in mind-

1 Initial purging into recovery bottle ( since there shouldn't be any air in the refrigerant line)

2. Collecting all the refrigerant into the receiver

3. Letting the compressor suck out the fresh refrigerant from the refrigerant bottle to the system. And pump it to the condenser

If you keep these simple steps in mind, it's impossible to forget.

Liquid refrigerant filling - Onboard.

Refrigeration Filling is another evergreen question that one should always have the answer inside.

steps are as follows:

1. Shutoff receiver outlet valve

By doing this all the refrigerant is collected in the receiver and finally, compressor cuts off in LP

2. Pump down the entire refrigerant into the receiver

3.Weigh the Refrigerant bottle

4. Purging out the refrigerant

Connect the outlet of the refrigerant bottle to the purge bottle/recovery bottle

since air should not let in and it also causes Ozone depletion.

5. Shut the valve to the recovery bottle

When frosting appears in the recovery bottle valve, its the indication that all the air in the line has moved out.

6. Fully Open the filing connection to the drier.

At this moment, the refrigerant starts flowing into the system and the suction pressure starts to increase and compressor cuts in.

7. Charge till the required amount

Bonus info:

Ideally, charge till the bottom of the condenser sight glass.

As if the condenser is full of liquid refrigerant, then there is no space for the vapor refrigerant to condense inside the condenser which comes from the compressor.

if your system has a receiver unit then, then even if you fill your receiver fully, there is no problem.

8. Shut the refrigeration filling valve connections

Infographics on refrigeration filling:

Everything you need to know about refrigerant filling:

Disclaimer: This is an ancient video from Our youtube channel

when we were teenagers in the editing industry.

All we had was the passion for teaching.

it's super slow but it does the job of simple explanation. Enjoy.

Refrigeration Filling Explained
Hope you enjoyed this article on refrigerant charging procedure. Do share if you like it. That's a great motivation for bringing more articles for you. Hope I fixed most of your refrigeration doubts.
Have a great day and thank you.
Comment down: Why a spanner is always used to operate these valves?

Back pressure valve in refrigeration - Explained !

2020-06-16T16:14:00.011+05:30

What's the function of a Back pressure valve?

Back pressure valve prevents the evaporator pressure from falling below a set value.

Even if the compressor suction pressure is lower.

Back pressure valve simply is to ensure that the minimum temperature is always maintained.

When the refrigeration system uses more than one evaporator which operates at different temperatures.

ie: if there are multiple refrigerating rooms with different temperatures, then there is a requirement of Back pressure valve.

If you have been around with the refrigeration for a while, then you know the 4 components of refrigeration by heart: Evaporator, condenser, compressor, Expansion valve.

Back pressure valve is an essential component in the refrigeration system. and this cannot be Omited.

Read on for a clear understanding.

If the above sentences are unclear, consider scanning this: 3 Essential refrigeration basics that one should know

What's a Back pressure valve in refrigeration?

Back pressure valve is a special non-return valve that is connected to the outlet of the evaporator. It's a spring-loaded valve. More like a relief valve.

As you might know, that the pressure inside an evaporator coil decides the room temperature.

as the boiling point changes with the pressure.

(Check out this 3 Essential refrigeration basics that one should know for more info on this)

To make things more clear,

Consider a simple real-life example: where you have 2 evaporator coils in your ship.

Back pressure valve is fitted at the end of the evaporator coil of higher room temperature.
Example refrigerant: (R134a)

Remember - Maximum heat is absorbed when there is a phase change ie, Boiling.

Meat and fish room Evaporator coil: is at -15°C (1.6 bar pressure)

Veg room evaporator coil: is at 5°C ( 3.5 bar pressure)

Since veg room refrigerant is at 3.5 bar, veg-room refrigerant starts to boil off at a higher temperature

( 5°C )

simply put,

If you maintain higher pressure in the veg-room evaporator coil, it starts to boil off at higher temperature and only a less amount of heat is absorbed.

and cannot maintain -15°C.

This is achieved by keeping a back pressure valve at the end of veg room evaporator coil.

Or else, the compressor keeps on sucking refrigerant from the veg room evaporator coil, and finally reduces the pressure to 1.6 bar which is the same pressure as that of the meat room evaporator coil.

And starts to boil at -15°C.

where ever there is a pressure drop across the system, this won't get affected

This dries up all the water content in Tomatoes/vegetables. and now this can be only used for making dried tomato chutney.

How a Refrigeration back pressure valve Works?

It’s this simple, From the left side, refrigerant comes from the evaporator and goes into the chamber

when pressure of the refrigerant gas exceeded the spring bellow pressure, it lifts up.

And lifts the needle up. This needle/valve remains open until the refrigerant gas falls below the set spring pressure.

Its works like a relief valve, and a certain pressure is always maintained.

Back pressure valve always maintain a constant pressure

Main application of a back pressure valve in refrigeration.

A few may say " back pressure valve is fitted so that high-pressure refrigerant in the veg room evaporator coil won't go into low-pressure meat room evaporator".

If there is no back-pressure vale, its not possible to have a pressure difference

or the temperature difference in the first place.

And even though there are a few application for this back pressure valve, This is the most important one,

Permits two or more evaporators, working at different temperatures, which works with the same compressor.

I highly recommend you to know the difference between temperature and heat in order to take full advantage of any refrigeration topic available on the internet.

Same goes for the Term Enthalpy.

for simplicity, let us say,

Temperature: The degree of heat.

Heat: Heat is the total energy.

Enthalpy: Enthalpy tells how much heat and work was added or removed from the substance.

Refrigeration: The process of removing heat.

Air conditioning: temperature, humidity, ventilation, and air cleanliness are maintained to our desired conditions.

You could find more specific molecular level definitions on the wiki.

But for the understanding of simple refrigeration onboard, plugging these to your vocabulary will eliminate most of your doubts. Puff.!

I hope you enjoyed this Short article on back pressure valve and share if you like this article on the back pressure valve.

comment down if you got any burning doubts on refrigeration topics.

3 Refrigeration basics that you should know | Onboard Refrigeration

2020-06-09T17:16:00.018+05:30

Essential words for any Refrigeration system:

Getting Chills when someone says Saturation Temperature? Probably you are not the only one. And I am here to help you.

You can find the most useful information you need to know in our quick refrigeration article, so that refrigeration and air conditioning becomes a piece of cake for you.

People may say, there are no free biryanis in this world. But this one is for you. Enjoy.

What is this Saturation Temperature?

Here is a snippet from Wiki

Saturation temperature means boiling point. Saturation temperature is the temperature for a corresponding saturation pressure at which liquid boils into its vapor.

Yes. its just boiling temperature!

Saturated steam and Superheated Steam

Saturated Steam is the steam

that is in direct contact with water from which it was produced.

Once water is heated to its boiling point, it gets vapourised and turns into Saturated steam.

And if all the moisture is removed, then we get dry steam.

At the Boiling point, it can Exist at both Liquid And Vapour.!

And in other words, If you have to produce superheated steam, heat the Liquid above the saturation temperature.

Always keep in mind that Superheated steam means no water content!

What's the Temperature of Normal Steam?

Say we take a bowl of water and we heat it, and the temperature of the water starts rising. Now the basic question is if you continue heating, what could happen?

Yes. It boils at 100°C at 1 atm.

Now steam is being formed. And the temperature of this steam cannot go above 100°C.

If you continue heating until all the water turns in to vapor, it will be still at 100°C.

Or as long as the boiling takes place, Temperature remains at 100°C this is an important basis for your understanding.

Subcooling and superheating in refrigeration

Simply put, subcooling means, Cooled below its boiling point.

Suppose if the boiling point of the water is 100°C and if the water is at 94°C,

Then its called "6 degrees of subcooling"

If the temperature of the steam is 105°C then it is called "5 degrees of superheating"

4 Components in any refrigeration :

As you might be knowing, the purpose of refrigeration is to remove heat from an Enclosed region. and that's done with the help of these 4 parts.

High-pressure side is on the left and Low-pressure is on the right

1. Evaporator

Purpose of the evaporator is to cool the enclosed space (cabin/diary room). by absorbing heat from the room and the refrigerant starts to boil. It might be fitted with a fan behind the evaporator for increasing the circulation.

2. Condensor

This is to liquify the gaseous refrigerant and then to subcool it.

(subcooling means cooling below its boiling point)

3. Compressor

If you read any first line of a compressor explanation, it will be written like this "To raise the saturation temperature of the refrigerant".

That simply means the compressor raises the boiling point of our refrigerant so that when it gets into the condenser, the heat is given off to the cooling water instead of absorbing heat from the cooling water.

And it also circulates the refrigerant. Probably this is the most asked question by seniors.

They may ask in this way "Ok why do you want to increase the temperature of the refrigerant again?

A Dedicated video on compressor

Note: The compressor slightly increases heat and it mostly increases the temperature

(For increasing the boiling point of ref)

4. Useful information on TEV that you should know.

It regulates the flow of refrigerant from the high-pressure side of the system to the Low-pressure side

and it creates pressure drop which reduces the boiling point (saturation temperature) of the refrigerant so that it can be boiled at a lower temperature.

The amount of the liquid refrigerant flow is determined by the spring-loaded valve which is determined by the pressures on the diaphragm.

The sensing bulb is filled with the same refrigerant and it is connected to chamber C and the vapor pressure in the bulb (yellow) is determined by the evaporator outlet.

Higher temperature in the evaporator outlet means- it opens more and more liquid flows to the evaporator coil

Lower the temperature in the evaporator outlet means- it opens little and lesser liquid flows to the evaporator coil

Inlet pressure together with the spring tries to close the orifice and the pressure in the refrigerant chamber B is determined by the refrigerant pressure in the evaporator

Bonus info: The screw connected here is called the superheated screw and this is to make sure that the temperature leaving the evaporator is 2 to 9 degrees above the boiling point. So that no liquid goes in tho the compressor. And if you tighten the superheat screw, Compression of the spring increases orifices closes a bit and now only lesser refrigerant flows into the evaporator.

And "degree of superheat" increases (more superheated gas comes out from the evaporator) -

Usually, nobody goes near this screw. this is factory set for a particular length of the evaporator coil
TEV is to control the flow of refrigerant when there is a load change.

For an easy understanding and memorizing, consider this everyday example:

Suppose there are 8 people sitting in a room and say refrigerant of 4L/hr is circulating through the system.

and for boiling this 4 L/hr refrigerant, some amount of heat is being absorbed

such that refrigerant in the outlet of the evaporator is slightly superheated

Now, suddenly 10 people enter into the same room, and heat in the room goes up.

If still the same quantity of refrigerant is passing through it, then more superheat is produced.

Superheat production starts early. so the problem with more superheat production is that now in the evaporator coil only lesser liquid is available for heat absorption (Boiling).

So the Expansion valve opens up more and brings back the superheat to the original place (see diagram below)

Now we have more liquid refrigerant available inside the evaporator for boiling.!

TEV is to control the amount of refrigerant going to the evaporator so that the evaporator is always filled with saturated mixture of vapor and liquid so that the entire surface area of the Evaporator is utilized for absorbing heat.

Tev valve is pushed down and the orifice is opened more - letting more refrigerant to flow into the evaporator

TEV makes sure that the liquid completely boils off at the end of your evaporator. This superheat is also provided for safety purposes. in case if all of them suddenly leave the room and there is no heat generation and there is no boiling of the liquid refrigerant. And this goes into compressor.!

Apart from this, having an Expansion valve that the rate of drop of temperature in the room is faster,

And if instead if we are using just a capillary tube for expansion, the room temperature gets cooler, but it takes a lot of time and that adds more compressor running hours.

Is there a TEV in our Domestic Refrigerator? A Side Quest for young Readers

How does your Refrigerant Flow?

Now for the purpose of oral exams or for living onboard, One must definitely now the 5 thermodynamic states.

1. High-temperature high-pressure Superheated Vapour [ HT HP SV ]

After the adiabatic compression (no heat transfer) by the compressor, Temperature of the Refrigerant rises up to 70°C (approx)

and then it passes through Condensor for cooling either by seawater or by air. and then it becomes

High-temperature high-pressure Saturated Mixture [ HT HP SM ]

and this gets cooled further and becomes High-temperature high-pressure Subcooled Liquid

[ HT HP SCL ] Even though the subcooling is really less. And on some ships, the liquid refrigerant leaves the condenser just above that of the seawater temperature.

If this is seawater cooled then this will be close to seawater temperature. The pressure on the low-pressure side is dependent upon the seawater temperature.

Say, seawater temperature is 28°C and the refrigerant cools to 26-25°C

and further, it is subcooled to 24-25°C.

Extra info on condenser: in some of the ships, the outlet of the evaporator is made to exchange heat by evaporator outlet. so that no liquid goes to the compressor

Now, when it passes through the expansion valve, it forms Low-pressure low-temperature saturated mixture [ LP LT SM ]

And as there is a little bit of flashing off and thus saturated mixture is formed

finally, when it passes through the evaporator and boils off by absorbing heat from your Mutton, it changes to Low-temperature Low-pressure Superheated vapor [ LP LT SHV ]

Additional info: The low-pressure side is decided by the setting in the LP cutoff switch and lower the pressure that you set, the liquid boils at even lower temperatures by taking more heat away from your food.

Real-life example: Imagine, you are in your cabin and you want to set your room temperature at 16°C for a great sleep. So adjust the pressure corresponding to the saturation pressure at 16°C

At 5 bar, refrigerant R134a boils at 16°C

Now, the compressor keeps on running and pressure lowers till 5 bar and your refrigerant can

Boil-Off even at 16°C.! Isn't that nice?

Whenever boiling takes place, maximum heat is absorbed and maximum heat rejection takes place while condensing. [ie Change of State].

Or in other ways,

If you need to set the room temperature at 16°C, You need to boil off your refrigerant at 16°C, So, in order to do that set the pressure accordingly. (LP setting)

Pssst. Not to use this idea for freezing higher rank officers. That's Isn't Cool.

What's Flashing-Off in refrigeration?

Temperature of the liquid refrigerant going into the low-pressure side is higher than the boiling point. and it flashes off

The refrigerant has 20°C in the high pressure side (left side) and when it moves to the low pressure side (right side), it boils off. As at 4 Bar, the refrigerant can boil at 12°C.

Low-pressure is on the right side and the high-pressure is on the left.

What happens when refrigerant flashes off?

As it flashes off, the temperature is absorbed from the "refrigerant-vapor-mixture".

and some of the liquid boils off taking its heat (latent heat) from the remaining liquid refrigerant.

Why does the Seawater temperature in the condenser decides the discharge pressure of the refrigeration plant?

An evergreen question that makes you feels like a pro (professional) when you have the answer.

For beginners:

The condensing temperature is the temperature at which a cooling medium changes phases from a gas to a liquid

The condensing pressure is the pressure at which the refrigerant is phase changing from a gas to a liquid.

Easier Explanation: The quantity of heat can be removed depends on the seawater temperature.higher the inlet temperature of the seawater into the condenser, then less heat can be removed from the refrigerant.

The condensation rate varies as seawater temp varies. Hence the refrigerant pressure at the condenser inlet also varies.

The same pressure acts as back-pressure to the compressor and hence compressor discharge pressure varies. Thereby increasing the compressor delivery pressure.

Compressor will keep on pumping till the Vapor refrigerant reaches its condensing pressure and if the seawater temperature is more, then the condensing pressure of the vapor refrigerant is also high.

If you go to colder regions the discharge pressure reduces to 10-12°C

and if your ship is near the equator region, it goes up to 20°C [changes with refrigerant]

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Thank You and have a nice day. Comment down if you still have doubts.

8 Checks to do In your purifier | Purifier Routine Checks

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A simple Infographics for you. Enjoy!

13 Basic Purifier questions that Every Junior Must Read.

2020-05-28T22:51:00.000+05:30

I am Sure At least one of these questions may come handy While you are in the purifier room or in any MMD.

A Closer Look at Frequently Asked Questions on Purifier

13. What are the purifier safeties?

Brake
Emergency stop
Vibration monitor
HT alarm
Metal sheeting on I/O pipes
Overload trip
Lower backpressure alarm

12. What is the importance of measuring the vertical height?

To avoid rubbing of pairing disk on pairing chamber

11. Which Component takes the vertical vibration and which component takes the horizontal vibration?

Spring inside bottom bearing case takes the vertical vibration
Buffer springs around neck bearings - they take radial vibration

10. What will be your action if you see the purifier vibrating when it is being stopped?

Apply the brakes immediately.

9. What is alcap purifier?

Its a centrifugal seperator no gravity disk or sealing water. But has a water outlet which stays most of the time closed clean oil is continuously being monitored if water comes in, It is desludged.

8. Reasons for the vibration of the purifier?

Sludge accumulation on one side during desludging or Sludge on one side got sticky
Bearing wear
Loose foundation Bolts
At the time of starting, Bigger gear Drives the Smaller gear and at the time of stopping, The reversal of action takes place ie, the smaller gear drives the bigger gear which is not suitable worm and gear arrangement and vibration may occur. and further, the gear arrangement may break due to stress.
Bearing Failure
Uneven wear of friction clutch
Motor speed too low or too high

7. What happens if the E/O has given the purifier motor connection the wrong way?

Friction Clutch won't be able to maintain the correct speed.
Locknut holding bowl onto spindle will come loose which is otherwise self-tightening
Pairing Disk (A.K.A) Cannot develop Enough Head.

6. What are the Purifier Overflow reasons?

Low RPM and Wrong Direction
Leaking 3-way valve
Excessive Back Pressure or service tank valve is in closed condition
If bowl opening water is leaky or opened by mistake
The Teflon sealing ring is not sealing properly
Bowl is not properly closed
Sealing water is insufficient
Excessive sludge deposit inside the bowl
No Operating water (A.K.A bowl closing water)or leaky
Incorrect Gravity Disk size
Operating water Filter Chocked
Bowl is not properly Sealed
Feed oil Temperature High or low
High Throughput
Worn out Orings near the Plug or Nozzle
The orifice plate is installed in the wrong way

Related Read: Purifier Overflow Reasons and causes Basics

5. What Should be your action if the Purifier is overflowing?

Check the operating water filter- It should not be Dirty
Check Oil Feed Temperature
Check The Feed Rate
Check RPM
Check All valves position closing and opening condition
Check For position Of 3 way Valve
Check Gravity Disk

4. How separation is done in a purifier?

Thin strata separation

Flow is laminar maximum at center, Minimum near boundaries,Zero at Boundary

Centrifugal Force on Heavier particles is more than upward force at the boundaries.

Related read: Purifier Principle

3. How will you come to know if the purifier disk stacks have lost its compression?

While assembling, Locknut will Align with O - O Mark Without any Effort, By tightening, it crosses too much

2. How to know the friction pad of the purifier is worn out?

Longer time to Build up RPM

1. Why purifier RPM is not attaining its rated speed?

Break Pad is not in Normal Position
Too much Sludge accumulation
Single Phasing
Bearing problem
Sump Oil Level Is Too high
Shafts are out of alignment
Bowl is Not in the correct position

Related read: Purifier starting procedure

Hope you enjoyed this Quick QnA. Have a nice day and, Use our Navigation Bar For More Interesting Information.

How do you start a purifier without destroying it ? | A Step-by-Step Guide

2020-05-23T20:04:00.007+05:30

PIC: A Cool 4th Engineer reads about purifier.

Introduction :

Eeeh.! Does a Busy marine engineer needs to read an intro?

Have a look at this if you are a trainee: Purifier principle

Down below, you can find how to start a Purifier and purifier lineup basics. from start to finish. Decorated with colorful line diagrams for serving your visual memory. Plus adding more beauty to our purifier explanation.

Next time when you hear something about starting a purifier or anything that's even related to a purifier, you could deliver this with a smile.

Essential basics - Purifier Parameters

1. Temperature of the oil - viscosity needs to be reduced before purifying so we heat the oil using heater

2. Rpm of the rotating bowl - For efficient separation and to keep the interface within the limit for that correct rpm should be maintained

this could be obtained either by revolution counter or by ampere ( approximate)

3. Oil Feed (throughput) - as you might be knowing there should be a balance between maximum, and minimum throughput.

2 Pre-checks in your Purifier :

After Line up check,

brakes
Lube oil

If your purifier has an attached pump and purifying sequences are set in the controller,
pressing "Auto-start" button on the controller does everything for you.

1.Bowl closing
2.Desludging
3.Sealing water
4.Feed inlet

But anyway it's necessary to know the manual starting and stopping of purifiers.
in case if there is any Emergency/malfunction or troubleshooting. or just for the sake of showing off to your junior.

You could even spook your 4th if you say these to him. (give it a try)

An easy Line diagram - purifier starting steps :

1. Skeleton of any purifier diagram.

PIC: showing line diagram of a typical purifier

2. With feed pump started and heater started

PIC: Showing Line diagram with Feed Pump started

PIC: With steam in and out

The 3-way valve makes sure that the settling tank oil goes to settling tank back without entering the purifier.

3. Open bowl closing water. [ also called as operating water ]

PIC: Opening Bowl closing water

Bowl Closes

PIC: Bow Goes up and closes

2. Open sealing water until it overflows from the water outlet.

PIC: Opening sealing water

Related Read: Gravity disk in purifiers - A mystery?

3. Slowly Open Feed valve by letting the "3-way valve" to the purifier.

You could see the oil displaces some amount of the sealing water through the water outlet gauge glass.

The feed should be open slowly else there is a chance that the closing bowl might get opened up.

PIC: 3-way valve directed to purifier

4. Adjust the backpressure by throttling the outlet valve of your purifier or by adjusting feed.

~~Purified oil flows into service tank~~

Adjust the Back pressure to your recommended settings.

Related Read: What's the difference Between Purifier and clarifier?

Enjoy the infographic

Check these while a purifier is running:

1. Check the Fuel Oil Temperature - If it goes above the boiling point of water, okay,
you know what happens next. yeah. "purifier Overflows.!

2. Inlet Pressure of Purifier. which shows the condition of the feed pump filters. If the pressure is less that indicates the feed pump filters are dirty).

3. Back Pressure should remain the same - If back pressure decreases, That indicates oil overflow through the water side or through the sludge side ( leakage )

4.Water overflow through the sludge port.

5. Check for excessive vibration in your purifier.

Related Read: Purifier Overflow reasons and causes

How Desludge a purifier?

1. Close the feed - Direct the oil to settling tank.

2. Supply sealing water - to save the oil which is left in the purifier.

3. Supply desludging water - at the time of deslugde Amps go high and comebacks to normal (if it's not, then it indicates the bowl has not opened properly).

4.Provide sealing water and repeat the initial steps for further purifying

Putting a purifier to sleep:

1. Set the 3-way valve position to the feed pump's suction.

2.Shut the steam inlet and outlet to the heater

3. Stop the feed pump to the purifier

4. Open the sealing water to displace the oil left in the purifier to service tank.
and when the sealing water overflows through the water outlet, and shut sealing water.

5.Deslugding:

why you need to desludge your purifier while stopping ? -

For Removing the deposited fuel particles or sediment. so that the sliding bowl can slide easily for the next cycle.

6. Stop the purifier motor

7. Shut the operating water valves, fuel valves, valve to the sludge tank if needed.

Have a nice day. and,

Share this with your juniors if you Liked this piece of article.
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Still have a burning question ? Drop Em in the comment box.

Best ways to select purifier gravity disk | A Complete Guide

2020-05-14T19:24:00.005+05:30

Why Gravity disk?

How do I select gravity disk for Purifier?

Gravity Disk in Purifier alters the location of the oil-water interface. And further, Interface can be shifted inwards or outwards with the correct selection of the gravity disk in your purifier. And With the proper selection of the gravity disk, the efficiency of the separation can also be improved.

In a nutshell, choosing a larger gravity disk of bigger diameter causes oil flowing out of the purifier Through the water outlet, And choosing a Smaller Gravity disk may result in lesser purifying efficiency. As the outer periphery of the disk stacks are left unused.

The Gravity disc can be chosen from the set of discs that are provided by the manufacturer. Every bit is super-simplified for you and easy to remember.

With the end of this article, you can easily select a gravity disk

1. When the specific gravity of the oil at 15 ℃ is known.

2. When the specific gravity of oil at a certain temperature is known.

And must-have information on purifier (It's so easy)

Understanding Gravity Disk basics:

An important thing to keep in mind is that the diameter if the gravity disk is the innermost circle diameter and water flows it through the inside.

The Gravity Disk Diameter is the inner circle diameter. This is important.

Water Flows as shown in the figure. And directed to a stationary impeller just like oil impeller
(Note: Nobody calls this as the "impeller". its called a "pairing disk").

Sometimes there may be 2 impellers (AKA pairing disks). If you have SAMGONG purifier manual nearby have a look at page the 19.
You could see "IMPELLER 1" and "IMPELLER 2".

A discussion with My fellow mate, he said he didn't had any impeller for collecting water. he just had one impeller for taking that oil out.

PIC: Shows the cross-section of a gravity disk.

How the gravity disk actually works? how interface is maintained? Can you create this in your own backyard?

Yes. Consider an empty container

An Empty container

adding water to the container

stir the water and till it forms a shape like this

Now try a different container shaped in this manner

Add water to the new beaker fo this shape

Now stir again, you could see a shape like this
and all the water would be thrown out.

Now you have a the air-water interface

Attach a disk [gravity disk] to the mouth of the beaker

Now with reduced mouth opening than shown in the picture (7/10)

You can see the interface getting inside, lesser the dia of the Gravity disk,
The interface moves further inwards

Consider our classic Example :

Oil and water in a normal beaker or in a settling tank.

Make it vertical with aided with centrifugal force

Oil and water in a Vertical beaker
if it's in a vertical position
And rotated (or applied a centrifugal force)

Fix a top Disk on it

Approximating a Purifier model for better understanding

These images will help you understand easily

Can you alter this interface?

Yes. of course.
As you have seen in the above diagrams, changing the mouth diameter changes interface. And here is a little explanation of the 2 major parts if you haven't Gained it already.

PIC: Showing Purifier Disk stacks and Top disk

Note: gravity disk dia means inner dia
(can't stress this anymore. it's that important for an easy understanding)

PIC: Purifier and Gravity disk and e-line representation.

To gain the fullest advantage of the disk stacks, E-line should be located outside of Disk stacks.

if there are holes in the disk stacks, the e-line should be located inside the holes. (More citations needed on this one)

PIC: Showing Flow of oil in ideal Condition With the correct selection of gravity Disk

And on the other hand, If the E-line is located outside of the top disk, Oil flows out to the waterside.

What happens if my gravity disk diameter is too large?

Yes, Overflow! A larger gravity disk of bigger diameter causes oil flowing out of the purifier Through the water outlet. have this diagram for better understanding.

PIC: Interface moves out leads to oil overflow

Note: Water impeller section is also called a heavy liquid chamber and Oil impeller section is called a Light liquid Chamber.

Oil flows out from the waterside.
As the interface moves out of the top disk.

What if Gravity disk is small?

Smaller Gravity disk may result in lesser purifying efficiency as the outer periphery of the disk stacks is left unused. See the diagram for better understanding

PIC: Showing a Less Efficient Way to purify

The outer periphery of the disk stacks are unused, Further leads to lesser efficiency

Gravity Disk Selection - Nomogram method

Pulled this out from google search query for you:

Nomogram:

A diagram representing the relations between three or more variable quantities by means of a number of scales, so arranged that the value of one variable can be found by a simple geometrical construction, e.g. by drawing a straight line intersecting the other scales at the appropriate values.

Nomogram Construction: Lines and Curves

What are the 4 Lines represented in a nomogram? (important)

1.Rising Curve
2.Falling Curve (Represented in red)
3.Horizontal line
4.vertical line

Figure 1: A simplified diagram that shows the Feed rate, temperature, and gravity disk diameter that has to be selected.

PIC: Showing Inside diameter, Temperature, and The feed rate

Figure 2: Added with vertical lines.

PIC: Purifier nomogram with Falling curve and with Vertical line

(End of Nomogram basics)

Related read: Ultra basics of Purifier and the two equations

Example 1: The specific gravity of the oil at 15°C is known

Specific gravity of oil   :  0.925 at l5°C
Treating temperature   : 70°C
Feed rate   :  3000 L/h

Step 1: locate the specific gravity of oil in the extreme left line. (0.925)

Step 2: Draw a curved line along until it touches the vertical axis of 70°C [ line 1 ]

Step 3: From the 70°C line, Draw a Horizontal line until it touches 100°C line
[ represented as bold vertical line]

PIC: Showing Steps 2 and 3

A zoomed image for a clear understanding. For mobile device

Purifier nomogram zoomed lines 1 and 2

Step 4: Connect the right end of line 2 [horizontal - dotted - pink] and point it to
the feed scale using a straight line ( 3000 L / h )

Purifier nomogram pointing to feed scale line from 100 C vertical line

Gravity disc inside diameter is obtained from the gravity disk diameter scale. here in our case, it's 79 mm [ as the pink bold line passes through section 79 ]

(Thanks to Samgong purifier manual. Extracted exact values from it)

Nomogram diagrams are different for different types of purifier models from the same manufacturer.

For example:

Samgong Purifier [ Model SJ20 G/GH ]
Samgong Purifier [ Model SJ30 G/GH ]
Samgong Purifier [ Model SJ50 G/GH ]

Has different charts (nomograms) for selecting a gravity disk

All the Nomogram Charts you can find it in your Purifier Manual labeled Under
"Gravity disc selection procedure"

I suggest you have a glimpse this "Nomogram" in this Wiki link and familiarize with the rarely used word: Nomogram

Related Read: Purifier - Clarifier and its difference

Example 2: The specific gravity of oil at a certain temperature is known.

Specific gravity of oil : 0.944 at 50 °C
Treating temperature : 98°C
Feed rate :1250 L / h

PIC: Purifier nomogram with Up curve lines

Step 1: Follow the rising curve from the specific gravity line 0.944 till the vertical line of 50°C [line 4]

PIC: converting to a specific gravity at 15"C

[Now follow the same steps - as shown in example 1]

Step 2: Draw line 5 with the falling curve till the line of 98°C

PIC: locating in the operating temperature- line 5

Step 3: Draw horizontal line until it touches the vertical line of 100 °C

PIC: A zoomed Image for mobile device

Step 4: From the right end of the horizontal line draw a line pointing it to feed rate scale
1250 L/ h

PIC: Pointing to Feed Scale

Step 5: Selection of the gravity disk from the gravity disk diameter scale

PIC: Selecting a Great gravity Disk.

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Happy Mother's Day.!

2020-05-10T12:56:00.004+05:30

All love begins and ends there ~~ Robert Browning

7 greatest overflow Reasons of all time | An Overflowing Purifier

2020-05-06T18:42:00.004+05:30

What is meant by purifier overflowing? -

"Oil coming out from the waterside"

Afraid of the term "purifier overflow ?" or the actual situation?
Well, this article is constructed just for you.

By the end of this article, you will have understood about gravity disk in purifier, interface, top disk, along the way.

And that one special purifier question and answer regarding a diesel oil purifier-
(An Evergreen Question).

Purifier Overflows again

7 reasons for the oil to flow out through the waterside
(A.K.A purifier overflowing)

Before stating those reasons, one should upgrade the understanding of the 3 things that are involved in this topic, or else this article may give you little value or leave the readers less satisfied.

1. Interface
2. Top disk
3.Gravity disk

1. Purifier Interface

The boundary between the Separating layer of 2 liquids. The boundary should be always within the top disk (inside)

The interface between air and oil

The interface between oil and water

2.Purifier Top disk

The topmost bigger disk (not the disk stack)

PIC: Purifier Top Disk

The Interface should be always within the top disk (it should be inside the top disk) or else,

The oil will move out of the top disk and the oil will come out through the waterside.

If the interface starts moving out gradually, it will come out of the top disk, and the oil starts to go through the waterside.

3. Purifier Gravity disk and why does it exists? Where is this gravity thing?

Consider an empty container

Empty container

Now add water to the container

Now, stir the water and it forms a shape like this

Now take a different container shaped in this manner

Add water to the new beaker

Now stir again, you can see a shape forming like this
and all the water would be thrown out
through the mouth of the beaker and forms a shape like this.

Now you have got the air-water interface

Attach a disk (gravity disk) to the mouth of the beaker

With reduced mouth opening than shown in the picture (7/10)

You can see the interface is getting inside and, The lesser the dia of the Gravity disk, the interface moves further inwards

note: "The diameter of the gravity disk means the innermost circle"

Purifier Overflow Reasons

1.Incorrect gravity disk (larger)

2.Higher back pressure (service tank valve closed)

3.High throughput (Excessive feed rate)

4.Oil Temperature height (sealing water gets evaporated)

5.Low temperature (density of oil increases and moves out)

6.Sealing Ring Leaky (lesser quantity of sealing water)

7.Reduced Rpm or Wrong direction
8.Leaking three-way valve

9.Excessive sludge deposit inside the bowl.
10. Sealing water low.

The following conditions should be satisfied to keep the interface within the top disk or to avoid overflowing of the purifier.

Here is a self-explanatory easy to remember chart.

Related read: What's the difference Between Purifier and clarifier, How to change from Purifier to Clarifier?

Easy to memorize with Logo.

Related read: What is the principle of purifier?

Note: With this information, you can answer "which gravity size disk will you use the HFO to DO or vise versa. if your purifier is running in DO (less dense) and change it into HFO (denser) then we have to put gravity size of lesser diameter
Since the density of the HFO is more and tends to move away (interface).

PIC: Purifier Interface with water and oil outlet

And in order to pull the interface back in, the lesser diameter gravity disk is used (or else it will go out of the top disk). and vise versa.

Comment down, Why nobody is talking about Clarifier Overflow?

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3 Big differences between Purifier and a Clarifier | Series and parallel

2020-05-04T23:43:00.004+05:30

The main difference between clarifier and purifier is as follows and It's better to answer the main purpose of the clarifier first which is to separate finer solid impurities from the oil. then starting with the difference in the individual parts

Clarifier

1.No gravity disk

2. Water outlet sealed

3.Bottom disk with no holes (Blind disk) [to increase the surface area of disks]

4.Sealing water not required

5.Only clean oil Outlet

Purifier

It can separate contaminants like water and solid impurities from liquids having different densities.

like sludge, water, aluminum. up to certain limits.

1.Gravity disc on top

2.Sealing water is required

3.Water outlet and Clean oil Outlet

4.Removes water + Suspended solids

PIC: Purifier and clarifier Comparison chart

How to change your Purifier to a clarifier?

3 Easy to remember Steps

1. Place the blind disc at the bottom of the disc stack.
2. Block the water outlet by a seal on the gravity disc.
3. Shut the sealing water inlet line.

The bottom part of the hole is covered to increase the surface area in order to let all the oil pass along with the slanted surface of the disk stacks or else it will just take a short cut through the holes and the surface area outside of the disk stacks are not utilized this is to improve the efficiency.
It will still work as a clarifier even if we don't take this step.

PIC: Need for clarifier

A clarifier works as a backup system if one feels that the purifier didn't remove all the dissolved solids so that the fuel injector and fuel plunger won't get affected

A quick overview of the general arrangement

For better cleaning purpose the purifiers on board can be arranged in both series and parallel way

Parallel arrangement

Purifier and clarifier with 50% capacity reduction

PIC: 2 Purifiers from settling tank to service tank

Series arrangement

The purified oil is given to Clarifier for further removal of solids

PIC: A simplified arrangement showing purifier with a clarifier

Note:

Even though there are questions and discussions regarding clarifier, some CE says that they have never used clarifier in series. Comment down your experience with a clarifier.

What's the principle of this purifier ?

2020-05-04T01:10:00.001+05:30

Purifier working and is there any equation for it?

Principle: A purifier works on the difference between the specific gravity of two different liquids/Stoke’s law

And it can't separate salt out of seawater. Why? Comment down.

High Centrifugal Forces are developed and Heavier particles move towards the outer side of the Bowl

Oil and Water (liquids with Different Densities)

The Force of separation Equation:

separation by gravity

ω = Angular velocity
r = Effective radius
ρw = density of water
ρo = density of oil
Fs= seperation force

The Force of separation can be increased if we keep this in a rotating cylinder. This is called a centrifuge. Then the "g" changes to ω² r

Fs = (pi/6) x D3 (ρw-ρo) * ω² r

Separation just by centrifugal force.

Settling Velocity Equation:

PIC: Equation showing Settling Velocity

where

v = Settling velocity (m/s)

rω² = Acceleration in centrifugal Feild (m/s²)

d = Diameter of the particle (m)

ρp = Density of Particle (Kg/m

³)

ρl = density of Liquid medium (Kg/m

³)

μ

= viscosity of the medium kg/(m.s)

A Must Watch Video For Beginners:

A Cartoon Showing Purifier Setting Speed to shape Formation

Further reference :

Stoke's law Settling Velocity (Derivation not needed for Exam) Note: If you are a trainee then watching all the youtube videos about purifiers might confuse you initially. Alcap, clarifier, purifier, hi-dens, Alfa Laval, and some videos may include different desludging mechanisms each video is different.

4 Important Non return Valves in any Fresh Water Generator

2020-05-03T02:06:00.001+05:30

Where can I find non-return Valves in a Fresh Water Generator ? and how many of them are there?

Another most asked question in the olden days.

4. There are 4 non-return valves present in a freshwater generator.

here you can find it.

1.Before Air ejector (swing check valve)
2.Before Brine Ejector (swing check valve)
3.After Distillate pump (swing check valve)
4.And of course, Overboard Valve (swing check valve/check valve with spring)
5.It could be also present in the chemical injection unit line. (check valve with spring)

Note: The type of check valve is not important for examination purposes.

See the attached diagram for better understanding.

PIC: Diagram Showing location and number of non-return Valves in A Fresh Water Generator

Bonus info:

Whats 90% vacuum? - its 0.1Bar.!

What will you do if your Ejector pump Suddenly stopped working one day? is there a line from fire and GS pump or fire and Bilge pump? Comment Down. Share your thoughts.

How to easily remember starting a procedure of a freshwater generator?

How to start Fresh Water generator With love? Shell and Tube.

2020-04-30T01:06:00.001+05:30

Here is a FWG's self-explanatory overview.

An Easy to remember Flow chart for FWG starting procedure

note: If it re-circulates into the shell, then the Brine ejector Will Take it out.

Actual scenario and General practice

A Calculator for checking saturation temperature (Boiling point)

Boiling Point Calculator

Engine Room Department Upgrades to new Domain with a Soft Logo.

2020-04-27T00:39:00.002+05:30

How do you like the New soft logo for you? Comment On it.

ERD team Upgrades to a Bigger Domain with a Soft colored Logo thank you for All your supports. And this blog just reached 2000+ visitors in its first 27 days.

thank you for all your supports. wish, we could deliver you with premium Contents and tutorials in the near future.

The tiny lubrication path in our Air Compressor!

2020-04-20T12:46:00.001+05:30

How the air compressor is lubricated.?

And

Lubricator? is that even installed on my air compressor?

let's dive into this intro less topic. straight away.

where do we plug the Lub oil pipe onto the piston?

( to the piston which is moving !!?)

If you too had this thought while walking around the engine room/or while taking a shower, you are a bit awesome. read on.

without much decoration, let me give this to you.

PIC: Lube oil Flow for a typical v type air compressor.

Lubricator?

In a tandem type air compressor, we have got "one gudgeon pin" and "two pistons"

PIC: A Tandem Type Air compressor.

First stage liner Cannot be lubricated by squeezing oil through the gudgeon pin.
It's done by lubricator (a separate gear pump or a plunger pump arrangement).

Video: Lubricator For Main Air Compressor: How To Adjust Feed Rate Credits: Devanand Sir
Just like quills, a groove arrangement is given to the liner

Comment down: how your generator is lubricated.

Checking Performance Of your Compressor | Old school method

2020-04-16T21:28:00.002+05:30

Okay here you go:

How to check the Efficiency/ performance of our Air compressor

How To be an alpha male when it comes to Air compressors.

check the followings given below:

Time taken to fill the air bottle (universal method)

No-load amps of the motor (Drain/Unloader in open condition) + lube oil pressure

Normal working amps + pressure at both the stages+ Lube oil Pressure

Time taken from cut-off from cut-in pressure

I have seen some corporate videos where they used to say that they have saved 3 to 4 lakhs just by plugging after doing some leakage tests.

And
When it comes to a 30KW Air compressor, it Is our job to keep that machinery well polished.

we ("Engineers") could easily save 2 to 3 lakhs for our company if we make sure that our valves are not leaky and if well maintained. Or even if you start your own industry after 5 years.

Extras

Check master drain valve whether the oil is present or not

Sound and vibration up to a certain level

Intercooler, aftercooler outlet temperature should not be high.

Oily air mixture should not come out from the breather pipe

Low Lube oil consumption

No escape of air from the suction filter

Please note it has been seen that efficiency was found to be better while sailing at lower room temperature.

Comment Down How much is your Air compressor's consumption.

Without much effort, we can save 3 to 4 lakhs for our company. A simple Energy efficiency help from your side. big deal right?

Video review about Air compressor efficiency checks.
They kept on saying about pressure setting optimization too.

The only job of an unloader in air Compressor!

2020-04-13T17:03:00.002+05:30

Air compressor unloader has got only one job to do. which is to unload the air compressor.

Pic: The unloading of the air compressor or simply put, compressor unloader.!

It's a small valve attached to an air compressor which saves our effort.
this valve is automatically operated

for

Starting (wich most of the people knows about)

Stopping

For intermediate discharging of moisture (say every 20 to 30 minutes)

Most of the air compressors have one automatic unloader and manual unloading valve (solenoid drain and hand drain)
(manual Unloader is provided if the automatic unloader doesn't operate)

Q1) Why unloader at the starting time?

For the beginners let me give it to you in the simplest. shortest way

The motor should pick up some initial momentum for compressing air or else if induction motor if started with a full load it draws high current and it also requires heavy torque.

Q2) Why at Unloader at the Stopping time?

For a smooth stop, or else the compressor will oscillate due to the high-pressure air which is trapped inside the cylinder. And proper hydrodynamic lubrication won't take place.

At the same time, a non-return-valve prevents the whole air bottle from draining.
and unloader of an air compressor is activated at regular intervals for the draining of moisture.

This is the sssssssshhhh sound that you can hear when the compressor stops.

Question: My relief Valve Lifts.!

2020-04-11T14:42:00.000+05:30

Relief valve Lifts.!?
say no more.

Pic: Relief valves are located in between the delivery valve and the cooler

Things to check for: If 1st stage relief Valve Lifts.

1. If the second stage suction valve is leaky, High-pressure air from the second stage leaks through the suction valve and acts on to the first stage relief valve and what happens next? yes. the relief valve lifts.!!

2. If the Second stage suction valve is stuck in the closed position then there is an accumulation of air from the first stage which keeps on building up and finally lifts up the first stage relief valve.!

4.water inside the compression chamber if there is a cylinder crack

5.Relief valve's spring malfunctioning. and thus lifts at a lesser pressure
6.intercooler chocked (comment below: how intercooler gets chocked.?)

Bonus Info:

Overhauling second stage discharge valve will ensure no pressure accumulation in the second stage

As long as the second stage suction is holding, then first stage relief valve will never lift.

And the Unforgettable Mistake.

2020-04-10T01:19:00.001+05:30

What's Your Biggest Unforgettable Mistake

you did onboard. Share With us

we would like to know.

Biggest mistake as a junior?

That you want to Give to Your beloved Juniors. So that they won't Close another valve to Scavenge Drain Tank. And make Engine room Dirty.

Comment down if you have got the spine.
If it reaches 10 we Will make a video out of it.

With your First name on it

ERDeparmtnet Team.

12 Things a Junior/Trainee Marine Engineer Shouldn’t Do When New to Ship

2020-04-09T00:57:00.000+05:30

New to the ship? it's okay.

Air compressor level 2 || Brushing up || Meo || MMD

2020-04-08T00:47:00.004+05:30

Air compressor level 2 || Brushing up || Meo || MMD

air compressor actual diagram adiabatic compression capacity how to start from dead ship overhaul of air compressor valve safety in air bottle parts in air compressor valves volumetric efficiency for valve dia:https://erdepartment.blogspot.com/2020/04/the-parts-of-air-compressor-valve.html

Engine Room Department

Our amazing Lip seal and stern tube lubrication | An InGenious arrangement

Our simple Stern Tube and lip seal arrangement

Where is this Hollow stern tube located?

Picture of aft side of the ship

2 purpose of a stern tube

A) Withstand the load

B) Holds the aft sealing housing

There is a sealing arrangement in both the ends of the stern tube. For sealing purposes and to keep things apart.If you have not heard about lip seal, it's just a sealing arrangement to avoid the moment of liquid into the bottom platform through the rotating shaft.

Overhauling your favorite centrifugal pump | 6 Checks and common problems

Before overhauling centrifugal pump

The most important step on any Pump overhaul:

Steps to overhaul a centrifugal pump:

A) Lifting the motor Away:

B) Going Inside the Pump Casing:

C)Removing impeller and the shaft:

D) Removing the mechanical sealing arrangement

E) Bearing cover and bearing removal

6 Checks for your centrifugal pump:

1. Wear ring and Impeller ring

2. Check the trueness of the shaft and threads on it.

3. No Pitting marks or corrosion in the shaft.

4. No Erosion or Pitting marks on Impeller or Impeller's seating surface.

5. Check the Keys, Mechanical seal. And casing.

6. Replace sealing, bearings, and gaskets (consumables)

Procedure to start the pump after overhaul

5 Common Problem and Answers for your pump

Pumps not delivering any liquid

Reduced pumping rate or Lesser discharge pressure

Pump Fails to deliver after Running smoothly

Pump overheated and draws too much power

Excessive Vibration

3 Powerful priming arrangements Of all time | Onboard Centrifugal pump

Is Priming Necessary in Centrifugal pumps?

1. Central priming system

2. Self priming centrifugal pump

Self priming arrangement of the centrifugal pump by Sriram sir

How Exactly Does a liquid ring pump work? What's the secret?

3. Priming centrifugal by air Ejector

5 Brilliant starting air line safeties to avoid an Explosion

Safeties in air starting line:

How Can the Air starting Line Explode?

Causes of starting airline explosion on ships

Prevention of starting air line explosion.

Essential air starting line safeties

1. Flame arrester in air starting line

2. A safety relief valve in air starting manifold

3. Bursting disk (Material - copper) in the air start valve

Actions to be taken when bursting disk burst while running:

4. Non return valve in air starting line

5. Thermal patch in air starting line

How do you test air starting valve for leakage?

1. While running - Air leakage test

2. While stopped condition - Air leakage test

A quick guide on filing refrigerant | Onboard Essentials

Refrigerant Filling onboard:

3 Things to keep in mind-

Liquid refrigerant filling - Onboard.

1. Shutoff receiver outlet valve

2. Pump down the entire refrigerant into the receiver

3.Weigh the Refrigerant bottle

4. Purging out the refrigerant

5. Shut the valve to the recovery bottle

6. Fully Open the filing connection to the drier.

7. Charge till the required amount

8. Shut the refrigeration filling valve connections

Infographics on refrigeration filling:

Everything you need to know about refrigerant filling:

Back pressure valve in refrigeration - Explained !

What's the function of a Back pressure valve?

What's a Back pressure valve in refrigeration?

How a Refrigeration back pressure valve Works?

Main application of a back pressure valve in refrigeration.

3 Refrigeration basics that you should know | Onboard Refrigeration

Essential words for any Refrigeration system:

What is this Saturation Temperature?

Saturated steam and Superheated Steam

What's the Temperature of Normal Steam?

Subcooling and superheating in refrigeration

4 Components in any refrigeration :

There is a sealing arrangement in both the ends of the stern tube.
For sealing purposes and to keep things apart.

If you have not heard about lip seal, it's just a sealing arrangement to avoid the moment of liquid into the bottom platform through the rotating shaft.