Oil and Gas Inspection

FITTING PIPE METHOD OF THE DEEP

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• PIPE LAYING - LAY BARGE METHOD (S & J-LAY-LAY)

- Welding pipe above the Barge

- High Cost (lay barge daily rate)

- Open Sea (open sea locations)

- Relative Sea Within

• RENTIS - TOWING METHOD

- Welding pipe in the ground and then pulled out to sea

- Relatively cheaper than conventional means

- Suitable for closed locations (in the dock)

• REEL BARGE METHOD

- Method of horizontal & vertical

PLANTING PIPE METHOD OF THE DEEP

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PRE-trenching

- Excavation Before the pipe in the title

- The condition of the hard ground

POST trenching

- Excavation of the pipeline was held

- Soft soil conditions

CRUDE DISTILLATION UNIT (CDU)

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Crude Distillation Unit (CDU) operates with the basic principle of separation based on boiling point of the constituent components. CDU column produces LPG, naphtha, kerosene, and diesel by 50-60% the volume of feed, whereas the other products of 40-50% by volume of atmospheric residue feed.

Atmospheric residue at the old refinery, which does not have a Vacuum Distillation Unit / VDU, usually only used as a fuel oil which is its very low value or sold to other refineries for further dioleh on the VDU. Whereas in a modern refinery, the atmospheric residue is sent as feed Vacuum Distillation Unit or as a feed Residuel Catalytic Cracking (after some in-treating in Atmospheric Residue Hydro Demetalization unit to eliminate the metal content of atmospheric residue).

Process Variable Crude Distillation Unit

Some process variables that affect the CDU operation are as follows:

1. Flash Zone Temperature

The higher flash zone temperature, the more the yield of product produced, and conversely the less yield bottom-CDU. But flash temperatue zone should not be too high because it can result in thermal decomposition / cracking bait. Temperature of thermal decomposition / cracking depends on type of bait. In general, temperatures of thermal decomposition / cracking of crude is around 370 ° C (385 ° C mentioned UOP). Flash zone temperature is regulated indirectly, ie by setting the Combined Outlet Temperature / COT-fired heater.

2. Top Column Temperature CDU

CDU column top temperature is set to restore some of naphtha which has been condensed as reflux back to the top column of the CDU. If flash zone temperature is raised, then the reflux rate should be raised to keep the temperature fixed top. Temperature is one of the top column naphtha endpoint directions. To obtain endpoint products of lower overhead then the top temperature should be lowered by increasing the number of top reflux.

3. Top Column Pressure CDU

Although the column top pressure never varied, but the small changes in the top column pressure will produce large changes in temperature at a fixed feed composition. If the column top pressure can not be kept fixed and CDU operations rely solely on quality control of products simply by setting tray temperatures / temperature draw off, then the product composition will change significantly. Pressure swing very often will make the CDU operation becomes unstable. To maintain the stability of the column top pressure mounted temperature controller that in-cascade with top reflux flow.

4. Steam Stripping

The amount of stripping steam (superheated) is inserted into the bottom of each side cut product steam stripper used to remove dissolved in the product lighter, which will determine the flash point products. Stripping steam can also be inserted into the bottom / bottom column reboiler with the CDU as a replacement for similar functions, ie removing the existing light fraction in the column bottom product CDU.

Weldability of a Metal

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● Metallurgical Capacity

Parent metal will join with the weld metal without formation of deleterious constituents or alloys.

● Mechanical Soundness

Joint will be free from discontinuities, gas porosity, shrinkage, slag, or cracks.

● Serviceability

Weld is able to perform under varying conditions or service (e.g., extreme temperatures, corrosive environments, fatigue, high pressures, etc.).

INSPECTION FOR SPECIFIC TYPES OF CORROSION AND CRACKING

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Each owner/user should provide specific attention to the need for inspection of piping systems that are susceptible to the following specific types and areas of deterioration (API RP 570) :

a. Injection points.

b. Deadlegs.

c. Corrosion under insulation (CUI).

d. Soil-to-air (S/A) interfaces.

e. Service specific and localized corrosion.

f. Erosion and corrosion/erosion.

g. Environmental cracking.

h. Corrosion beneath linings and deposits.

i. Fatigue cracking.

j. Creep cracking.

k. Brittle fracture.

l. Freeze damage.

RISK BASED INSPECTION

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Identifying and evaluating potential degradation mechanisms are important steps in an assessment of the likelihood of a piping failure. However, adjustments to inspection strategy and tactics to account for consequences of a failure should also be considered. Combining the assessment of likelihood of failure and the consequence of failure are essential elements of risk-based inspection (RBI).

When the owner/user chooses to conduct a RBI assessment it must include a systematic evaluation of both the likelihood of failure and the associated consequence of failure, in accordance with API RP 580. The likelihood assessment must be based on all forms of degradation that could reasonably be expected to affect piping circuits in any particular service. Examples of those degradation mechanisms include: internal or external metal loss from an identified form of corrosion (localized or general), all forms of cracking including hydrogen assisted and stress corrosion cracking (from the inside or outside surfaces of piping), and any other forms of metallurgical, corrosion, or mechanical degradation, such as fatigue, embrittlement, creep, etc. Additionally, the effectiveness of the inspection practices, tools, and techniques utilized for finding the expected and potential degradation mechanisms must be evaluated. This likelihood of failure assessment should be repeated each time equipment or process changes are made that could significantly affect degradation rates or cause premature failure of the piping.

Other factors that should be considered in a RBI assessment conducted in accordance with API RP 580 include: appropriateness of the materials of construction; piping circuit design conditions, relative to operating conditions; appropriateness of the design codes and standards utilized; effectiveness of corrosion monitoring programs; and the quality of maintenance and inspection Quality Assurance/Quality Control programs. Equipment failure data and information will also be important information for this assessment. The consequence assessment must consider the potential incidents that may occur as a result of fluid release, including explosion, fire, toxic exposure, environmental impact, and other health effects associated with a failure of piping.

It is essential that all RBI assessments be thoroughly documented in accordance with API RP 580, clearly defining all the factors contributing to both the likelihood and consequence of a piping failure. (API RP 570)

RELATIVE RISK VS. ABSOLUTE RISK

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The complexity of risk calculations is a function of the number of factors that can affect the risk. Calculating absolute risk can be very time and cost consuming and often, due to having too many uncertainties, is impossible. Many variables are involved with loss of containment in hydrocarbon and chemical facilities and the determination of absolute risk numbers is often not cost effective. RBI is focused on a systematic determination of relative risks. In this way, facilities, units, systems, equipment or components can be ranked based on relative risk. This serves to focus the risk management efforts on the higher ranked risks.

It is considered, however, that if a Quantitative RBI study is conducted rigorously that the resultant risk number is a fair approximation of the actual risk of loss of containment due to deterioration. Numeric risk values determined in qualitative and semi-quantitative assessments using appropriate sensitivity analysis methods also may be used to evaluate risk acceptance. (API RP 580)