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Last updateFri, 23 Sep 2016 2pm

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An Alternative Basics Education: Valve Ed Comes to You!

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Pentair Valves & Controls Hosts Customer Appreciation Training Event

2 DAYS AGO
Pentair Valves & Controls Hosts Customer Appreciation Training Event

More than 200 representatives from Houston’s refinery, chemical and petrochemical industries joined Pentair Valves & Controls on Sept. 15 at its Pasadena, TX facility for a customer appreciation BBQ and training event . The presented seminars are a part of Valves & Controls’ Pentai...

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Mueller Water Products Recognized for Best Smart Water Solution

3 DAYS AGO

Mueller Water Products, Inc. received the 2016 Best Smart Water Solution award at the third annual Smart Water Summit in Palm Beach Gardens, FL. Mueller Water Products, who won this award for the second time, was recognized for smart technology solutions offered through its Mueller Co., Mueller System...

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Senate Overwhelmingly Passes Water Resources Development Act

2 DAYS AGO

The U.S. Senate recently passed the Water Resources Development Act (WRDA) of 2016 with a broad bipartisan vote of 95 to 3. This legislation not only authorizes critical U.S. Army Corps of Engineers projects that drive investment in navigation, flood management, and ecosystem restoration, it provides ...

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Alaska Railroad Prepares First U.S. Shipments of LNG

2 DAYS AGO

The Alaska Railroad (ARRC) will demonstrate its ability to safely transport liquefied natural gas (LNG) in intermodal LNG ISO containers from southcentral to interior Alaska during a month-long operational performance project in early fall 2016.

ARRC is the first railroad in the country to obtain permi...

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Manufacturing Growth Eases Again in September

1 DAY AGO

At 51.4 in September, the seasonally adjusted Markit Flash U.S. Manufacturing Purchasing Managers’ Index (PMI) was down from 52.0 in August and pointed to the weakest improvement in overall business conditions since June. The latest PMI reading marked seven years of continuous growth across the ...

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Leading Economic Indicators Down Slightly in August

2 DAYS AGO

The Conference Board Leading Economic Index (LEI) for the U.S. declined 0.2% in August to 124.1, following a 0.5% increase in July, and a 0.2% increase in June.

“While the U.S. LEI declined in August, its trend still points to moderate economic growth in the months ahead,” said Ataman Ozy...

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PSV Inspection: Test Only, or Full Inspection and Overhaul?

In today’s ever-changing, fast-paced world, uptime is at a premium, while remaining in compliance with governmental and plant regulations is a requirement. With increasing demands placed on plants to produce, it is necessary to look at different ways to perform inspections on pressure relief devices and minimize plant downtime. Many plants in the United States have opted to modify their plant PSM (process safety management) programs to allow a “test only” on each pressure relief device in lieu of a complete disassembly and “VR” overhaul. The intent of this article is to explain the pro’s and con’s of both methods, while balancing additional demands of productivity, cost, safety and environmental issues.

Test Only

A “test only” can be performed by two different methods: (1) “In-situ” online testing while the valve is still in service; or (2) bench testing—removing the valve and sending it to a local repair/test center for verification of relief pressure and seat leakage testing.

In-situ testing

PRO’S: In-situ testing gives the end user an economical advantage over other methods as it allows the plant to keep the process unit running while testing is being performed. While this type of testing is typically more expensive on a per-valve basis than bench testing, it is much more economical for the end user in the total overall cost of performing the test.

CON’S: In-situ testing produces very little results regarding the total functionality of the valve. While it does provide a start-to-discharge point (the pressure in which the valve actually starts to lift), it does not put the valve into lift, does not provide any type of external joint leakage testing (back pressure test), does not allow for a visual inspection of the inlet and outlet, and typically cannot accurately inspect for seat leakage. In addition, in-situ testing can become very time-consuming depending on the location of the valve and the process it is in. In some cases, the valves will be located in a “fresh air” application or in an area that requires the equipment to be intrinsically safe.

Bench testing

PRO’S: Bench-testing allows a full functional test to be applied to each valve by putting the valve into lift (lift may vary based on volume of test equipment). It also allows the valve to blow down and reseat and allows for a seat leakage test. In addition, the valve is back-pressure tested to inspect for any external leakage from bolted or threaded joints. While this is usually the most economical of all PSV inspections on a per-valve basis, the end user typically experiences internal costs such as loss of production, use of plant manpower to remove and install the valves, additional materials required for the installation, and any other peripheral safety concerns dictated by the location of the valve.

CON’S: Bench testing is typically known as the “norm” for test-only inspections; but it also has its own pitfalls. While it does provide both a full functional and seat leakage test, it does not provide the end user with a dimensional and visual examination of the PSV’s internal working components. All manufacturers of ASME-certified PSV’s provide dimensional tolerances, clearances and visual inspection points that are required to maintain the valve’s integrity and ensure that it is in “like new” condition. Additionally, a “test only” does not provide an internal visual inspection for corrosion and/or erosion of the body and bonnet cavities, internal parts, bearing points and spring—all of which can affect the valve’s performance and its total life in service.

Full Inspection and Overhaul

A process involving a pretest, full disassembly, internal inspection and functional test is the only true way to ensure that your PSV is in the best possible condition. The pretest is performed before the PSV is disassembled. The results from the pretest are used to help gauge whether a valve would have relieved in service and at what pressure, whether it would have reseated and whether it had seat leakage. By performing a pretest and then an entire overhaul and inspection, each part of the PSV is cleaned, inspected, reused/repaired/replaced, assembled, tested and returned to service.

A certified “VR” overhaul performed by a certified repair company authorized by the National Board of Boiler and Pressure Vessel Inspectors1 is the common industry standard followed and accepted by the majority of regulatory agencies and end users throughout the United States. In some cases, end users will accept a non-VR repair as long as it meets certain criteria spelled out within their own PSM program. While the “VR” is the preferred method, plant specific repair criteria may be acceptable with some end-users. A listing of all authorized “VR” stamp holders can be found in the National Board’s NB-182.

PROs: As stated above, a full inspection and overhaul is the only true method of determining the condition of a valve. When a valve is disassembled and inspected, it gives you a full view of the internal condition of the valve, a full visual and dimensional inspection of all internal parts, verification of the spring number and range, any potential visual corrosion or erosion, and a full functional test demonstrating consistent, repeatable performance. Coupled with the pretest results, this is the only accurate way to predict frequency of inspections required to comply with plant PSM requirements.

CONs: There are two main downsides to a full inspection and overhaul; additional time and cost of repair. To properly overhaul any PSV, there are certain requirements that must be followed in order to provide a “VR’d” valve. This method can take 3-4 times longer (time may vary based on the size and condition of the valve) than that of a test only. Additionally, there are additional labor costs for the repair, as well as costs associated with transportation, plant labor (for removal and installation) and unit downtime. These factors need to be taken into consideration along with production schedules to maintain a true and accurate PSM program.

PSV Management Software

Determining the methods and frequencies of inspection is not an easy task. As stated, there are many factors—not just the “pop-point” of a PSV—that affect whether inspection frequencies should be shortened, extended or maintained.

Managing all of this information can be a daunting task. Having an internal database or using a repair/testing facility that is equipped with the proper database is essential to a successful PSV program. The ability to manage this information, help predict frequencies of repair, and assist in tracking history and total life cycle cost for each PSV is a critical component of the PSM process.

Summary

There are many methods of PSV inspection that are used to meet end-user PSM requirements. Determining which method is the safest and most practical is not to be taken lightly. Although cost will always be a factor in the decision, safety, quality and efficiency considerations should play an equal (if not greater) role in determining PSM frequencies and methods.

A PSV is a plant’s last line of defense when it comes to protecting life and property. A properly maintained PSV will ensure that the end user, the community and the environment will not be exposed to equipment failure resulting in a catastrophic situation.


Bart Collins is the General Manager for Precision Services, Inc. of Louisville, KY and Corporate Operations Manager for its parent company, Precision Pump and Valve Service, Inc. (http//ppvs.com) of Charleston, WV. Reach him at 502.499.8250 or This email address is being protected from spambots. You need JavaScript enabled to view it..


1 National Board of Boiler and Pressure Vessel Inspectors; “NBIC” www.nationalboard.org

2 National Board of Boiler and Pressure Vessel Inspectors; “NB-18” www.nationalboard.org

 

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