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Human Factors Can Cause a Disaster—or Prevent One

Human Factors Can Cause a Disaster—or Prevent One

Process industry plants are complex and ...

Improving Valve Sealing Performance and Reliability

Improving Valve Sealing Performance and Reliability

From time to time, we are re-posting wel...

A Primer on Fugitive Emissions

A Primer on Fugitive Emissions

Fourscore and seven years ago, no one ha...

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Industry Headlines

Industry Headlines

Emerson Expanding Mississippi Facility

1 HOUR AGO

Emerson plans on delivering $500,000 in new equipment to its facility in Sherman, MS. Because of this investment , and its promise of new jobs for the region, the Sherman Economic Development Corp. has approved $150,000 in grants for Emerson.

"We have a relatively new Fisher product that will be reloca...

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REXA and CCC Form Joint Initiative

1 HOUR AGO

REXA and Compressor Controls Corporation (CCC) have formed a joint initiative to modernize steam turbine controls for enhanced performance based upon each company’s core competency.

There are more than 10,000 turbomachinery trains worldwide powered by CCC. By upgrading mechanical and hydraulic go...

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Chevron and Pembina Sign Deal to Build Pipelines, Other Facilities

-1 DAYS AGO

Calgary-based Pembina Pipeline Corp. has signed a 20-year deal with Chevron to build natural gas pipelines and processing facilities for a potential production operation in northwest Edmonton, Alberta. The infrastructure developed over the term of this agreement has the potential to represent a multi-...

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U.S. in Midst of Biggest Drilling Surge Since 2012

-1 DAYS AGO

“U.S. drillers pushed ahead on the biggest surge in oil drilling since 2012 as companies take advantage of oil prices that have held steady above $50 for almost three months,” Bloomberg reports .

“Drilling is booming in a few shale plays -- led by the Permian Basin in West Texas and Ne...

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U.S. Private Sector Growth Slows from January’s 14-Month Peak

1 HOUR AGO

At 54.3 in February, the seasonally adjusted Markit Flash U.S. Composite PMI Output Index dropped from 55.8 in January but remained above the 50.0 no-change value for the twelfth consecutive month. The latest reading signaled that private sector output growth moderated from the 14-month high recorded ...

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NAM Kicks Off Tour at Emerson Innovation Center in Austin

1 HOUR AGO

The National Association of Manufacturers (NAM) kicked off the 2017 State of Manufacturing Tour at Emerson Innovation Center in Austin, TX—a “hotbed of modern manufacturing.” The event is the first in a series of stops in six states throughout the next week, including a visit with Pr...

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Safety-Relief Valve FAQ

Our company routinely receives inquiries from end users about their safety-relief valves.

Here are some of the most frequently asked questions...


Q:  What is the proper way to install a safety or safety-relief valve?

A: Safety and safety-relief valves should be installed vertically with the drain holes open or piped to a convenient location. All piping must be fully supported.

 

Q:  How often should I test/ inspect my valve?

A: Maintenance should be performed on a regular basis. An initial inspection interval of no longer than 12 months is recommended. The user must establish an appropriate inspection interval depending on the service conditions, the condition of the valve and the level of performance desired.

The ASME Boiler and Pressure Vessel Code does not require nor address testing installed valves. The only thing the code states are design and installation requirements, such as some valves must have a lifting lever. For instance for Section VIII:

“Each pressure relief valve on air, water over 140° F, or steam service shall have a substantial lifting device which when activated will release the seating force on the disk when the pressure relief valve is subjected to a pressure of at least 75% of the set pressure of the valve.”

Q: What mounting orientation should be used to install a safety valve?

A: Installing a safety valve in any position other than with the spindle vertical and upright may adversely affect performance and lifetime.

Q:  Why is there a hole in the valve body?

A: This drain hole is required on some models by the ASME Boiler and Pressure Vessel Code. It is intended to prevent any condensate from accumulating in the body that may freeze or corrode internal valve parts and prevent the valve from opening. The drain hole should be piped away to safely dispose of any discharge or condensate.

Q: Which end should be connected for vacuum valves?

A: This is often a confusing topic. The correct installation often looks backwards from what appears to be correct. A paper instruction tag illustrating the proper connection is attached to each valve. Vacuum valves should have the NPT threads that are cast integral to the body attached to the vacuum source. See the assembly drawing for additional clarification.

Q:  What set pressure should the valve be set to open?

A: Typically, the valve should be nameplate set to open at the MAWP (Maximum Allowable Working Pressure) of the vessel the valve is intended to protect. There is a tolerance to actual set pressure, which means a valve set at 100 psig nameplate may open slightly above or below 100 psig. Consult the current ASME Boiler and Pressure Vessel Code for tolerance classes and special situations when the set pressure may be different than the MAWP.

Q:  Why is my valve leaking?

A: It is normal for spring-operated safety valves to exhibit leakage or simmer/warn, as the system operating pressure approaches the nameplate set pressure, typically in the 80%-90% range of nameplate set pressure. The ASME Boiler and Pressure Vessel Code does not require a specific seat tightness requirement. A certain level of leakage is allowed per manufacturers’ literature and API-527 Seat Tightness Performance Standards, both of which can be found in the Technical Reference Catalog and in the Data Supplement, summarized as follows:

  • Factory Standard Seat Tightness Performance: No visible (no audible for air service) leakage for 15 seconds (30 seconds for liquid or Section IV steam service) at 20% below nameplate set, or 5 psig below nameplate set, whichever is greater. EXCEPTION: Section IV steam service is checked at 12 psig.
  • API-527 Standard Seat Tightness Performance: A Functional Test Report (FTR) is automatically provided for valves ordered to API-527. See API 527 for complete details.

At very low set pressures, the ratio of the downward spring force as compared to the upward pressure force is very small. In these cases it may be impossible to achieve seat tightness.

Use soft seats for superior seat tightness, assuming the application falls within the soft seat temperature limitations. Although soft seats will typically provide a higher degree of seat tightness than metal seats, Factory Standard does not ensure bubble-tight seats, regardless of seat material.

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