Industrial Plug Valves

Plug valve diagram showing
plug shape and orifice.

There are common components to be found on almost every process system that involves fluid control. Regardless of the operation's scale, pumps, piping, tanks and valves are likely to be part of the system.

Valves, of which there are many types, provide control over the flow rate, direction and routing of fluids in a processing operation. Flow can be started, stopped or modulated between zero and full rate using a properly sized and configured valve. Some valves enable media flow to be diverted to a selection of outlets, in lieu of a single inlet and outlet pair. Specialized valves regulate inlet or outlet pressure, or prevent fluid flow from going in an undesirable direction. All of these capabilities are packaged into differing valve product offerings that present a very large selection array to a process designer or engineer.

Industrial flow control valve types are generally classified according to the structure or arrangement contained within the valve body that provides obstruction to fluid flow. Some of the common types are ball, butterfly, gate, globe, and plug. Surely, there are more valve types, and this article is not intended to list them all. Some of our previous blogs have discussed selection considerations for gate, ball and butterfly valves. This article will focus on one of the oldest valve types, the plug valve.

Plug valves, like ball and butterfly valves, span from fully open to fully closed positions with a shaft rotation of 90 degrees. The “plug” in a plug valve is installed in the flow path within the valve body and rotated by means of a stem or shaft extending to the exterior of the body. Plugs are often tapered toward the bottom and are fitted to a seating surface in the valve body cavity that prevents fluid from bypassing the plug. An opening through the plug, the port, can be shaped to provide particular flow characteristics. There are numerous variants of the basic plug valve which may make it suitable for particular applications. One common variant is the lined or sleeved plug valve, with an insert or interior lining of material that creates an isolating barrier between the valve body and the media. This allows use of less expensive materials for the body construction that may be otherwise subject to corrosion by exposure to aggressive media.

Plug valve advantages:

• 90 degree rotation from open to closed provides fast operation.
• With proper configuration, can be well suited for frequent operation.
• Availability of corrosion resistant liner may provide comparative cost savings because valve body can be constructed of less expensive material.
• Design is simple and employs a low parts count.
• Valve can be serviced in place.
• Generally, low resistance to flow when fully open.
• Reliable leak-tight service due to tapered plug wedging action, replaceable sleeve, and injection of lubricant in some variants.

Plug valve disadvantages:

• Higher friction in the plug closure mechanism may require comparatively higher operating torque than other valve types.
• Without a specially designed plug, generally not well suited for throttling applications.
• Rapid shutoff delivered by plug design may not be suitable for some applications where hammering may occur.

Share your fluid control application challenges with a valve and automation specialist. Leverage your own knowledge and experience with their product application expertise to develop an effective solution.

Contact Thompson Equipment (TECO) for all your valve automation and valve repair needs.

https://teco-inc.com
800-528-8997

What Are Orifice Plates?

Fig. 1 - Orifice Plates

The orifice plate is the simplest of the flowpath restrictions used in flow detection, as well as the most economical. Orifice plates are flat plates 1/16 to 1/4 inch thick. They are normally mounted between a pair of flanges and are installed in a straight run of smooth pipe to avoid disturbance of flow patterns from fittings and valves.

Three kinds of orifice plates are used: concentric, eccentric, and segmental (as shown in Figure 1).

The concentric orifice plate is the most common of the three types. As shown, the orifice is equidistant (concentric) to the inside diameter of the pipe. Flow through a sharp-edged orifice plate is characterized by a change in velocity. As the fluid passes through the orifice, the fluid converges, and the velocity of the fluid increases to a maximum value. At this point, the pressure is at a minimum value. As the fluid diverges to fill the entire pipe area, the velocity decreases back to the original value. The pressure increases to about 60% to 80% of the original input value. The pressure loss is irrecoverable; therefore, the output pressure will always be less than the input pressure. The pressures on both sides of the orifice are measured, resulting in a differential pressure which is proportional to the flow rate.

Segmental and eccentric orifice plates are functionally identical to the concentric orifice. The circular section of the segmental orifice is concentric with the pipe. The segmental portion of the orifice eliminates damming of foreign materials on the upstream side of the orifice when mounted in a horizontal pipe. Depending on the type of fluid, the segmental section is placed on either the top or bottom of the horizontal pipe to increase the accuracy of the measurement.

Eccentric orifice plates shift the edge of the orifice to the inside of the pipe wall. This design also prevents upstream damming and is used in the same way as the segmental orifice plate.
Orifice plates have two distinct disadvantages; they cause a high permanent pressure drop (outlet pressure will be 60% to 80% of inlet pressure), and they are subject to erosion, which will eventually cause inaccuracies in the measured differential pressure.

Contact TECO with any process flow question or requirement. You can find them by visiting https://teco-inc.com or by calling (504) 833-6381.

Industrial Control Valve Design and Operation

The design and operation of industrial control valves  is very important to understand if you work as a process engineer, a plant maintenance person, or if you design process control loops.

Control valves are used extensively in power plants, pulp and paper mills, chemical manufacturing, petro-chemical processing, HVAC and steam distribution systems.

There are many types, manufacturers, body styles, and specialized features, but the they all share some basics operating principles. The video below explains components, operation, and fundamentals.

TECO designs automated control valve systems for all major industries including chemical, pulp and paper, petro-chemical, power generation, and water treatment.  TECO’s experience and engineering background make them a uniquely qualified partner for your next automated valve requirement.

https://www.teco-inc.com
800-528-8997

ABB Rotameters Quality and Performance a Legacy of Fischer and Porter Roots

The Fischer & Porter Company, founded in 1937, was a well-known and respected manufacturer of
process instrumentation. The Fischer and Porter brand has long been associated with an industry-leading range of flow measurement products. The legacy is strong though, and despite the F&P brand being shelved, their rotameter (variable area flowmeter) line is still referred to by some old-timers as "Fischer and Porter Rotameters" or "F&P Rotameters".

In 1994, Fischer & Porter was acquired by Elsag Bailey Process Automation as a strategic union to blend Elsag Bailey's expertise in distributed systems with Fischer & Porter's expertise in process instrumentation. In 1999 ABB acquired Elsag Bailey and moved the F&P products in to a larger portfolio of ABB process instrumentation and the Fischer and Porter line of rotameters became known as ABB rotameters.

Today, Fischer & Porter products are fully integrated into the ABB portfolio of process instrumentation products which include variable area flowmeters (rotameters), magnetic flow meters, vortex shedding meters, and mass flow meters.

In 1947 Thompson Equipment (TECO) was the first firm ever appointed to represent and sell the Fischer & Porter Rotameter line.  TECO proudly continues that relationship today and specifies, services, and sells ABB Rotameters nationwide.  TECO also maintains a large inventory ready for same-day shipment. For more information, visit https://teco-inc.com/ABB or call 800-528-8997 for immediate service.

Thermo Scientific Belt Scale Maintenance

Thermo Scientific Model 10-14, 10-17, 10-20, 10-30, and 10-101 Belt Conveyor Scales

Belt conveyor scales have become an important part of most bulk material handling facilities. However, being relatively unobtrusive in most conveyor systems, they are often overlooked or ignored after their initial installation. Lack of simple maintenance will potentially cause significant reduction in the accuracy capabilities of these instruments. Most belt conveyor scales are capable of providing reliable results within ±0.50% of their full-scale rating. Belt conveyor scales that have been certified via the National Type Evaluation Program (NTEP) are capable of providing results that meet the criteria of the National Institute of Standards and Technology (NIST) Handbook-44, which is 0.25%. This is defined as being within 0.25% of actual material load and repeatable within a 0.25% bandwidth.

Regardless of the accuracy capability of the scale design, it is unlikely that these devices will perform as promised if simple maintenance procedures are not strictly adhered to. Every scale installation will develop its own set of operating characteristics; therefore it is absolutely necessary to monitor the scales performance and provide routine maintenance as required. It is generally advised, throughout the belt scale industry, that calibration checks be made frequently during the weeks after initial installation, then to increase the time frame between calibrations as statistical results are obtained. While this is a simple suggestion to follow, all too frequently the increase in time between calibration verifications defaults to only whenever a problem is suspected. By then it is too late, incorrect weighments have been made, processes have been interrupted and inventory levels need other means of verification.

Establishment of a routine inspection procedure, including not only the belt conveyor scale, but the entire material handling system, will result in an increased confidence in the scale and ultimately greater control of the accuracy it is providing. It is important to remember that the entire conveyor that the belt scale is installed in becomes part of the “weighing system,” and that any changes that occur or are performed within this conveyor can and probably will affect the performance of the scale. Therefore, in addition to a routine scale maintenance procedure it becomes imperative that any and all maintenance performed on the conveyor be reported to the individual or department responsible for the scales performance.

Verification of the basic mechanics of the conveyor system itself is an integral part of the scale maintenance procedure.

Please see Thermo Scientific Belt Conveyor Scale Maintenance Check List below.

Download the PDF version of Thermo Scientific Belt Scale Maintenance here.
 

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Happy New Year from Thompson Equipment

With 2017 coming to a close, all of us at Thompson Equipment wanted to reach out and send our best wishes to our customers, our vendors, and our friends! We hope that 2018 holds success and good fortune for all of you.

TECO: A Stocking ABB Rotameter National Distributor

TECO's relationship with ABB rotameters dates back to 1947 as the first firm to represent and sell the Fischer & Porter Rotameters (as they were known back then). TECO is your best source for rotameters, with many models in stock, and decades of application assistance. ABB rotameters are simple, low cost, and maintenance free. TECO's specialty is helping customers choose the right instrument for their application. TECO offers standard flow ranges as well as custom flow ranges sized to our customer’s unique flow environment.

Download the latest ABB Rotameter brochure here, or view the embedded version below.

ABB Rotameter / Variable Area Flowmeters from Thompson Equipment Company