Last updateThu, 15 Mar 2018 4pm



How to Improve Control Valve Performance with Positioners

As the final control element in most process control and automation systems, control valves are part of a complex system-within-a-system in which the valve positioner can be an integral component.

The control valve is made up of four principal sub-systems:

  • The valve body, which includes the bonnet and piping inlet and outlet connections.
  • The valve trim, plug, stem, cages, retainers and disc, used to control the flow through the valve body.
  • The actuator, used to provide power to move the valve stem or shaft.
  • The positioner, used to control the position of the valve stem and provide linearization.

VMA Technical Event: Engineering Valves in the Extreme

While much the 2017 VMA Technical Seminar, held March 2-3 in Nashville, focused on numbers, statistics and specifications, attendees were reminded in a highly charged, emotional presentation by safety awareness speaker Brad Livingston just why it is important to be so vigilant when engineering valves in the extreme.

In “Just a Second Ago” Livingston recounted the events of 1991 when he nearly lost his life because of decisions he and a co-worker made to shave a few moments off a welding job on a natural gas pipeline. According to Livingston, the two explosions—which were 100% preventable—happened because standard safety procedures were ignored. He blamed himself for not speaking up and insisting they be followed, and his plea to those gathering for this event was: “Consider, what is it worth?”

How to Improve Reliability and Safety of Solenoid Valves

In an industrial setting such as a chemical plant, oil refinery or a deep-sea oil rig, there are safety instrumented systems in place that are designed to promptly bring about a safe shutdown of a process if certain hazardous conditions are detected. Such safe shutdowns frequently involve isolating a process fluid flow, often accomplished using an ESD (emergency shutdown) valve. If the ESD fails dangerously, when a hazardous condition necessitating a shutdown occurs and the ESD does not perform its function when required, the worst-case consequences can be catastrophic.

ESD valves often include a solenoid valve in the ESD design with the solenoid valve energized in an open position while the process operates normally and with the solenoid valve moving to the closed position to initiate a safe shutdown of process fluid flow. Solenoid valves can fail (be unable to close on command) due to several different conditions. However, the failure mode contributing most significantly to the dangerous failure rate of the solenoid valve is that of sticking or adhesion.

Improving Valve Sealing Performance and Reliability

From time to time, we are re-posting well-received or particularly valuable articles that have previously run on VALVEMagazine.com so that those who might have missed them will be able to catch up on the best of the best. This article, “Improving Valve Sealing Performance and Reliability” initially ran on November 17, 2014.

Approximately 300,000 tons of fugitive emissions are released each year in the United States, according to the Fluid Sealing Association, and regulations put in place to lower that number are being added every year.

Combine that regulatory pressure and the stresses of today’s economic environment, and it is obvious that original equipment manufacturers (OEMs) and end users are increasingly seeking solutions that not only reduce emissions but also result in a permanent and noticeable increase in the service life of their products and equipment. Performance, value, reliability, repeatability and safety are all factors that are taken into account when developing and purchasing products to perform in this environment.

The Science Behind Steam Assisted Flares

Flares are a common site in petrochemical plants. They are used to safely incinerate products that need to be disposed. Ideally, the load on a flare would be very light. However, there are times where there is a large amount of product that cannot be stored and incineration is the most practical solution. High loads on flares will normally occur during an upset condition such as a safety valve opening or a unit being out of service that would normally process the product being sent to the flare.

When incinerating these products, combustion efficiency is of paramount importance as well as the avoidance of “smoking” or releasing carbon that can be seen. To accomplish both of these goals, flares often use steam or air for the flaring process.



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