06282017Wed
Last updateWed, 28 Jun 2017 5pm

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Lubricants: Always Important—Sometimes Essential

Lubricants: Always Important—Sometimes Essential

Most valve professionals take more notic...

Why Air Valves are Needed in Water Applications

Why Air Valves are Needed in Water Applications

Air valves are hydromechanical devices d...

Achieving Profitability Through Maintenance Management

Achieving Profitability Through Maintenance Management

One of the distinctions between maintena...

Control Valve Positioner Performance Diagnostics

Control Valve Positioner Performance Diagnostics

There has been discussion for some years...

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Industry Headlines

U.S. Crude, Petroleum Exports Have More than Doubled Since 2010

Wednesday, 28 June 2017  |  Chris Guy

U.S. crude oil and petroleum product gross exports have more than doubled over the past six years, increasing from 2.4 million barrels per day (b/d) i...

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Industry Headlines

Emerson in Talks to Acquire Software Company Paradigm Ltd.

1 DAY AGO

According to Bloomberg , Emerson is in talks to acquire software company Paradigm Ltd. for approximately $1.5 billion.

“Paradigm specializes in seismic data interpretation and imaging equipment to help oil and gas companies know where to drill. The logic of such a deal seems sound and will help Eme...

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VMA Members Lead MDM Top Industrial PVF Distributors List

2 DAYS AGO

Modern Distribution Management (MDM) recently published its Top Distributors list for 2017. Four of the top 5 distributors in the Industrial PVF category ; MRC Global, NOW Inc., Wolseley Industrial Group and FloWorks International; are currently VMA members.

“While oil & gas markets have start...

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U.S. Crude, Petroleum Exports Have More than Doubled Since 2010

3 HOURS AGO

U.S. crude oil and petroleum product gross exports have more than doubled over the past six years, increasing from 2.4 million barrels per day (b/d) in 2010 to 5.2 million b/d in 2016. Exports of distillate, gasoline, propane, and crude oil have all increased , but at different paces and for different...

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Mountain Valley Pipeline Gets Environmental Approval

1 DAY AGO

The Federal Energy Regulatory Commission (FERC) determined that construction and operation of the Mountain Valley Pipeline would result in some adverse environmental impacts, but the majority of these impacts would be reduced to less-than-significant levels. This determination is based on a review o...

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IMF Lowers Forecast for U.S. Growth to 2.1%

5 HOURS AGO

According to the newest forecast from the International Monetary Fund (IMF), growth in the U.S. is expected to rise 2.1% both this year and next, driven by continued solid consumption growth and a cyclical rebound in private investment. In its last forecast the IMF predicted 2.3% growth this year an...

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U.S. Durable Goods Orders Fell the Most in 18 Months

1 DAY AGO

New orders for manufactured durable goods in May decreased $2.5 billion or 1.1% to $228.2 billion, the U.S. Department of Commerce announced. This decrease, down two consecutive months, followed a 0.9% April decrease. Excluding transportation, new orders increased 0.1%. Excluding defense, new orders...

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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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