Tag Archives | Valves

The-Tao-of-Measurement-07-03

Q&A with Co-Author of ISA Book The Tao of Measurement

Q. Why do you believe the book is a “must-read” for all those involved in instrumentation or process control? A. This book provides indispensable information for anyone involved in instrumentation or process control. It explains the principles of operation pertaining to all the main types of temperature sensors, pressure sensors and transmitters, and flowmeters. It […]

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Sectional view of a variable resistance diffuser (a control valve would have been attached to the smaller flange). Valve upstream pressure moves the piston against a spring force and the downstream pressure of the fluid emanating from the control valve. Thus, the combination spring plus control valve downstream pressure less the upstream pressure defines the low pressure drop across the conventional control valve. The balance of the upstream pressure is reduced by the perforated passages. Note, all holes move in unison, hence the short travel.

What are the New Innovations in Control Valve Technology?

After the hectic activity of the 1980s and 1990s, especially on the international level through the International Electrotechnical Commission (IEC), efforts to either refine or create new standards have slowed considerably. Past activities led to a spate of standards yielding more accurate sizing, due to a better understanding of fluid dynamics, as related to valves, […]

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Colorful pipes

Use Signal Characterization in the DCS to Linearize the Installed Flow Characteristic of a Valve

Signal characterization to linearize valve installed flow characteristic has a bad reputation due to some practical implementation problems. These problems can be addressed today by doing the characterization in the distributed control system (DCS), but the stigma remains. With pneumatic positioners, signal characterization was done by the use of a cam. Standard cams were based […]

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oil valve

How to Use Valve Position Control to Optimize Process Efficiency and Capacity

There are many opportunities for process optimization by valve position control (VPC). Table 1 summarizes common examples of the use of VPC for increasing process efficiency and capacity. Efficiency is increased by reducing energy and raw material costs for a given production rate. Capacity is increased by increasing feed rates for a given efficiency. Table […]

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101 Tips for a Successful Automation Career

The Importance of Using Tuned Positioners on All Control Valves

I was encouraged to omit positioners in one of my first projects in the 1970s as lead instrument engineer. A former power system maintenance technician taking a new career path in instrument maintenance decided that positioners would add unnecessary complexity and aggravation. Fortunately, the request that valves not have positioners occurred after the project was […]

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101 Tips for a Successful Automation Career

How to Use High Rangeability Flowmeters and Valves to Increase Plant Turndown

I became sensitized early in my career to flowmeter and valve rangeability when I inherited the responsibility of solving pH control problems from the late Vernon Trevathan. The 0-14 pH measurement scale covers 14 orders of magnitude of hydrogen ion concentration (14 orders of magnitude of strong acid or strong base concentration). Standard practice in […]

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101 Tips for a Successful Automation Career

How to Eliminate Split Range Oscillations in Process Control

Just as split personalities cause mental instability, split ranged loops cause process control instability. Actually, the situation is worse for split ranged loops because valve stiction is particularly bad near the closed position, and the transition between fluids (e.g., between water and steam) may involve changes in phase besides changes in dynamics. If you have […]

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