level measurement

Vibratory Level Sensor and Heavier Dry Materials

2011-09-26T16:43:55-05:00

Recently one of our Application Engineers was asked if a vibratory style level sensor could be used to detect heavier bulk solids materials such as metal shot blast media.

Our Application Engineer responded by mentioning that a vibratory type level detector can indeed be used to detect shot media. However, due to the nature of the vibratory technology, this type of sensor would require a protective baffle to be installed if it is employed where heavier materials are stored or in a dynamic process where the material may be shifting en mass (see baffle examples above). Most designs for the vibratory type level detectors contain a sensing element, that if bent as a result of mishandling or exposure to excessive process dynamics the sensor can be rendered ineffective. Of course, the heavier the target media the greater the chance of the sensing probe suffering damage.

Heavier powder & bulk solids materials like metal shot blasting media may be even better served by a bin level indicator which is more rugged. Monitor's model MK-2 R.F. Capacitance level detector is recommended. This instrument is designed with a sensing probe constructed of a solid T316 SS and even if deflected will continue operating. It is very rugged.

For more detailed information on the best application uses for vibratory sensors, please check out our blog entitled How Many Figs does it take to Equal 150 Newtons?

DC powered rotary paddle level switch uses AC motor to ensure functional reliability and long operational life

2011-04-06T10:31:00-05:00

Does your installation require low voltage (12 or 24vdc) and you still want the reliability that rotary paddle level indicators provide? You don’t have to settle for a lesser rotary product… check out a practical solution that Monitor offers in their rotary paddle level indicator line.

Most manufacturers of rotary paddle indicators do not offer a highly-reliable 12 or 24vdc option. Monitor does. Monitor Technologies implemented a design change in the 12 and 24vdc rotary paddle bin monitors. The change dramatically improved the performance of these models and made them a viable solution for process oriented systems requiring a low voltage power source, minimal installation cost, and frequent level cycling.

Rotary paddle bin level monitors use a small motor to rotate a paddle that protrudes inside a silo or bin. As material surrounds the paddle, its rotation is halted. Within the bin monitor, the motor continues to rotate creating an internal cam action which actuates the output switch. In addition, the motor is shut off through the actuation of a second switch within the bin monitor.

Typically when specifying a rotary paddle bin level switch, the operating source of the sensor (115vac, 230vac, 24vdc, etc.) matches the operating requirements of the internal motor. This results in AC powered bin monitors using AC motors, and DC powered bin monitors using DC motors.

Economical DC motors are not designed to run continuously, and therefore their use in rotary paddle indicators result in compromised longevity. These motors use internal brushes and commutators which physically wear as the motor rotates. Life expectancy is only 5,000 hours (e.g. six months of continuous operation) depending on application load and temperature. (Figure 1 shows a DC motor).

Economical AC motors can be sourced that have a long operational life. The permanent magnet synchronous AC motor uses technology that has no physical wear characteristics. Applications have operated successfully using this motor within the Monitor Model KA rotary paddle bin monitor for over 20 years. (Figure 2 shows an AC motor).

The internal construction of Monitor’s 12/24vdc powered KA and KAX bin monitors is different. Instead of compromising the design with a lower-life DC motor, the Monitor rotary paddle bin monitor includes electronics that converts the 12/24vdc power source to 6vac energy that is used to operate a 6v AC motor. The Monitor 12/24vdc powered rotary paddle bin monitor is designed to save cost without the sacrifice of product performance and life expectancy.

So if you’ve been inconvenienced by poor performing low voltage rotary paddle indicators, or you’ve been told that all low voltage systems will work equally well, buyer beware! Look into Monitor’s practical 12/24vdc solution and rest well.

Visit www.monitortech.com or contact one of our Application Engineers at fred@monitortech.com.

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Figure 2

Flexar® can provide dependable continuous level sensing in the production of activated carbon

2011-01-06T14:48:51-06:00

Figure 1

Figure 2

Activated carbon, also known as activated charcoal, is a carbon product that has been put through a process to make it very porous. It is then used in the purification of air and water, the cleanup of environmental spills and the capturing of volatile compounds. For example, activated carbon is used in mercury emission control systems for coal-fired power plants. Activated carbon can be derived from a variety of raw materials including coal, lignite, coconut shells, nutshells, wood and other agricultural by-products. The Flexar® guided wave radar level sensor (see Figure 1) has been used to provide continuous inventory management for most of these raw materials. The Flexar has also been used to control inventory on the finished forms of activated carbon such as granular, pelletized, and powdered states. Figure 2 shows an original material (nutshells) on the left and the activated carbon product that is made on the right. Flexar sensors were chosen to provide real-time continuous level control in the storage for both of these items. Flexar is very versatile because it is unaffected by dust, bulk density, temperature and other properties. It can also be used for a variety of liquid applications.

Monitor Technologies’ Flexar^® guided wave radar sensor is a continuous level measurement system using TDR (time domain reflectometry) principles where radar pulses are focused down to the material surface by the unit's wave guide (a heavy duty cable) and the time-of-flight of the pulse reflection back to the instrument electronics is directly related to the empty distance in the vessel and the material level.

Benefits of Flexar^® include no moving parts for less wear and tear, easy installation and setup with minimal to no field calibration required, a universal power supply for high or low voltage options and a choice of RS-485 or analog 4-20mA output. It can also be interfaced with the SiloTrack inventory management software. For more details on Flexar guided wave radar please visit www.flexar.info

Technorati Tags: level sensor level measurement bin level indicator level control solids level indicator

Auxiliary Output Enclosure (AOE) Satisfies Input Needs for other Plant Systems

2010-10-26T16:43:39-05:00

When choosing a continuous level measurement system, in addition to an operator interface, sometimes a customer also wants to have an output to some other type of control system such as a PLC or DCS. Available outputs include both relay contacts and analog outputs. To fulfill these requirements, Monitor developed an auxiliary output enclosure (AOE) capable of housing as many as four output cards containing either relay outputs, analog outputs or a combination of both. When controlled by our HMI2 operator interface, each SiloPatrol® SMUse level sensor can drive one analog and up to two relay outputs. If SiloTrack Inventory Management Software is the operator interface, the number of analog outputs assignable remains at one analog output per sensor but there can be up to four relay outputs per sensor. RS-485 communication wiring consists of a twisted pair that is shielded and installed in a daisy chain fashion. Since the auxiliary output enclosure is also an RS-485 driven device, the AOE can be placed anywhere along the RS-485 communication network. Placement of the AOE in close proximity to a PLC or DCS reduces the amount of additional wiring necessary to connect the AOE outputs to the inputs of these other devices. This will significantly reduce the amount of interface wiring that would normally be required by standard analog output sensor wiring practices.

Flexar® guided wave radar level sensors that are used in conjunction with SiloTrack Inventory Management Software can also drive an auxiliary output enclosure as previously described.

Auxiliary output enclosures are available in either two or four output card configurations. (Two card version shown above.) The two types of output cards can be mixed or matched. Flexar® guided wave radar and SiloPatrol® SMUse sensors may not currently coexist on the same RS-485 communication network. Consult Monitor's Technical Support group for selection of the correct SiloTrack product offering if your over-all sensor system design requires the use of both SiloPatrol SMUse and Flexar guided wave radar sensors.

Technorati Tags: level sensor level measurement bin level indicator level control solids level indicator