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Introduction to Pressure Relief Devices - Part 1

Introduction to Pressure Relief Devices - Part 1

When the pressure inside equipment such ...

Is Your Company Ready for The New Reality?

Is Your Company Ready for The New Reality?

Since August, 2015, when VMA’s 201...

Offshore Oil Extraction and Transportation

Offshore Oil Extraction and Transportation

Offshore oil facilities come to the fore...

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Industry Headlines

MRC Global Signs Agreement to Sell OCTG Business

1 HOUR AGO  |  Chris Guy

MRC Global Inc. has entered into a definitive agreement to sell its U.S. Oil Country Tubular Goods (OCTG) business to Sooner Pipe, LLC, a subsidiary o...

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Industry Headlines

MRC Global Signs Agreement to Sell OCTG Business

1 HOUR AGO

MRC Global Inc. has entered into a definitive agreement to sell its U.S. Oil Country Tubular Goods (OCTG) business to Sooner Pipe, LLC, a subsidiary of Marubeni-Itochu Tubulars America, Inc., for $48 million, subject to certain adjustments.

MRC Global's U.S. OCTG sales were approximately $305 milli...

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PM International Suppliers Joins VMA

1 DAY AGO

This week VMA welcomes PM International Suppliers, LLC as our newest associate member (distributor/channel partner), our 2nd new member of 2016 so far.

PM International supplies pipe and fittings, tubing, valves, flanges, bars, sheet and forgings with numerous worldwide sources for a wide variety o...

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IHS: North American Drillers Need Billions More in Cuts

21 HOURS AGO

The depressed oil price environment is painting a gloomy outlook for North American exploration and production (E&Ps) companies, and further, significant CAPEX cuts are needed in order for the group to demonstrate real financial discipline and align spending more closely with cash flow, accordin...

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Energy Sector Bracing for More Bankruptcy Filings in 2016

21 HOURS AGO

“In 2015, the energy sector accounted for more than one-half of all public company bankruptcy filings, including eight of the 10 largest filings. Current oil prices and bond values indicate that 2016 will be another active year,” according to McGuireWoods Consulting.

“To account f...

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U.S. Job Openings Climb to Second-Highest Level on Record

2 DAYS AGO

The number of job openings increased to 5.6 million in December, the second highest number ever recorded, the U.S. Bureau of Labor Statistics reported today. Hires and separations were little changed at 5.4 million and 5.1 million, respectively. Within separations, the quits rate was 2.1%, and the l...

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Machine Tool Orders Rose in December, Down in 2015

2 DAYS AGO

The U.S. Manufacturing Technology Orders report for December 2015 showed that order values grew 20.4% compared to the prior month, according to The Association for Manufacturing Technology (AMT). For all of 2015, the year’s total orders were down 17.4% compared to 2014.

While the month-to-mon...

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A Case for Mechanical Temperature Control

vmwnt12_beyond_valves_fig1Instrument, mechanical or project engineers may see a multitude of temperature applications cross their desks. Their immediate reaction might be to employ a temperature control loop. But could a mechanical, self-operated temperature regulator be a better solution for the valve application?

When approaching a temperature control application, the engineer usually considers:

  • The degree of accuracy needed
  • Whether the application requires feedback (Are limit switches/output signals used?)
  • Whether the application needs to be controlled through a DCS, PLC or other type of controller
  • The budget for the application.

The answer to whether a mechanical temperature regulator might be a cost-effective and reliable solution for the application depends on those considerations.

In almost any process facility, a variety of temperature control applications can be found. As with any controlled variable, both the accuracy and criticality of those applications can vary widely. Often, non-critical temperature applications become instrumented control loops even when a self-operated or mechanical regulator could provide the desired accuracy along with a substantial cost savings.


WHAT’S CONSIDERED

vmwnt12_beyond_valves_fig1Figure 1. Temperature regulatorA typical temperature control loop ­(Figure 1) requires:

  • a temperature sensor
  • wiring and conduit
  • connection to a controlling device
  • a control valve (and sometimes a positioner and/or I/P converter, and an air-filter regulator)
  • plant air

A self-contained temperature regulator requires no power, no air supply or other expensive compo­nents to operate. Representative costs based on a 1-inch line size would be:

  • Temperature transmitter: $300-1,000
  • Temperature controller: $400-1,000
  • Control valve and actuator: $1,500-3,000
  • I/P converter: $200-350
  • Air set regulator: $100-150
  • Positioner: $500-2,000
  • Control loop total: $3,000-7,500
  • Temperature regulator: $500-2,500

Although designs may vary from manufacturer to manufacturer, most temperature regulators operate on the same principle. A premeasured amount of “fill” is drawn into the thermal system filling the upper diaphragm chamber, the capillary tube and most of the bulb. As the controlled temperature increases, the fill in the sensing bulb begins to vaporize and creates pressure on the sealed system. This pressure drives the valve stem, closing direct-acting valves or opening reverse-acting valves. By using different fill fluids, many different temperature control ranges can be offered for both cooling and heating applications—temperature ranges are readily available from -20° F (-29° C) to 500° F (260° C).

Applications for which these devices might be ideal include tank farms, large heat exchangers, heat exchangers with slow temperature changes, area heating/cooling (warehouse/maintenance shops) and steam tracing.

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