Isolation valves are required to block the media from another section of the piping system, usually immediately downstream from the valve. One might expect that the quality of the isolation should be perfect, i.e. when the valve is fully closed, there will be no flow past the closed valve. One might also expect to experience no leakage of the contained media out of the stem, body or bonnet joints; and one may expect this quality of closure to be repeatable.
Incredibly, this requirement is seldom met. Often the end-user or buyer has actually requested a valve that leaks significantly because the standards that industry has used for years have not been explained or understood. Oftentimes these standards work well for general purpose and/or fit-for-purpose valves but do not always take into account the extreme, rigorous, and sometimes dangerous properties that certain severe service applications employ today.
To properly understand allowable valve leakage rates, you must understand the varying standards used to describe leakage in isolation valves. Each of these standards uses an array of pressure tests that all have different allowances for pressure, media, and test duration. This article will review the most cited standards in North America – MSS Standard SP-61, API Standard 598, and ISO 5208. It will also highlight the shortfalls in using these standards for severe service applications where the pressures, media, and cycle times would need a have their own, much higher standard to ensure safety and efficiency of operations.
Over the years, the industry has demanded better tools to help improve and control their investments and the valve industry has seen engineering and architectural firms use increasingly detailed specifications that attempt to remove ambiguity. The valve industry in turn has responded with better compliance through design, materials, and quality control. Many Severe Service Valve manufacturers have created their own specifications for testing that hold their valves to a higher standard though most of these are not recognized on a global scale.
One must be careful, however, to substantiate and quantify claims and expressions that appear to be clear. Class VI, Tight Shut-Off, Bubble-Tight, and Zero Leakage all evoke positive isolation abilities in performance, however, without more details, many valve users may be disappointed if they rely on valves sold with these buzzwords. These “designations” don’t have defined objective metrics to delineate them and are often used as marketing terms.
Valve leakage may be viewed from four discrete sources: 1) Seat Seal, 2) Stem Seal, 3) Body Seal, and 4) Pipe Connection, in order of potential of leakage or fugitive emissions. Each of these areas will have different criteria for their design, execution, and testing.
Test standards have been established to provide uniformity, however there is no uniformity between the different standards and therefore decisions must be made by the manufacturers as to which one(s) are adopted for use. The end-user or specifying engineer must also decide which tests he wants as the guardian of his concerns.
Once the standard or standards are chosen, the minimum test requirements must be considered for the intended application. In addition, the verification of the standard by the manufacturer of each new valve and the continuing conformance while in service must be addressed.
There are three test standards that are typically used in North America. These include:
Last Revised in 2019 this test from the Manufacturers Standardization Society is to be used for “fully-open” or “fully-closed” valve service. This test is not intended for use with control valves. It uses four tests to establish leakage allowances:
Test
Production Pressure Test
Shell Leakage Test
Seat & Closure Member Test
No Visible Leakage Test
Reason
Check valve pressure containment ability
Check valve pressure containment ability of the external body
Check the performance of the closure mechanism
Check for visible leakage or bubbling
Allowable Media Requirements: air, inert gas, or liquid such as water, kerosene, or other fluid with viscosity not greater than that of water.
Available for purchase here. (Manufacturers Standarization Society, 2019)
This standard (10th Edition), released in 2016 from the American Petroleum Institute provides industry standards for valve ratings and leakage.
This standard covers inspection, examination, supplementary examinations, and pressure test requirements for resilient-seated, non-metallic-seated (e.g. ceramic), and metal-to-metal-seated valves of the gate, globe, plug, ball, check, and butterfly types. It divides valves into two categories to better test their pressure capabilities.
Allowable Media Requirements:
You can purchase a complete copy of API 598 from their website. (American Petroleum Institute, 2016)
Test
Visual Examination
Shell Leakage Tests
Backseat Tests
Closure Tests
Reason
Visually assure compliance with standards for all components of the valve
Check valve pressure containing structures meet standards
Used to verify leakage past the stem or shaft to bonnet seal
Check for leakage through closure mechanism
Valves: DN (NPS) ≤ DN 100 (NPS 4) and ASME Class ≤ 1500
DN (NPS) > DN 100 (NPS 4) and ASME Class ≤ 600
Valves: DN (NPS) ≤ DN 100 (NPS 4) and ASME Class > 1500
DN (NPS) > DN 100 (NPS 4) and ASME Class > 600
Allowable Media Requirements:
You can purchase a complete copy of API 598 from their website. (American Petroleum Institute, 2016)
This standard from the International Organization for Standardization specifies the tests that manufacturers of valves must undergo to authenticate the metallic pressure containing structures of their valve. This test also dictates the degree of valve closure tightness and the allowable leakage. ISO 5208:2015 is intended to be used in conjunction with product standards.
Test
Shell Test
Optional Backseat Test
Closure Tests
Reason
Validate the strength of the valve pressure-containing and retaining structures
Used to verify leakage past the stem or shaft to bonnet seal
Validate leakage through a valves closure mechanism
Allowable Media Requirements: water, that may contain a corrosion inhibitor, kerosene or other appropriate liquid having a viscosity not greater than that of water, or air or other suitable gas
Available for purchase here. (Industrial Organization for Standarization, 2015)
Many valve manufacturers have started using helium or nitrogen as a medium in testing as they are smaller, non-flammable molecules. MSS has accepted the task of writing new Standard Practices for Severe Service Valves and is working on publishing a new standard within the next 18 months. This allows for a much more rigorous testing standard for valves operating in severe service applications. While these testing standards are not globally recognized quite yet, the end-users can be confident the same tests are being used but are being held to a higher standard.
American Petroleum Institute. (2016). API 598 Valve Inspection and Testing. Retrieved from https://www.api.org/Standards/
Industrial Organization for Standarization. (2015). ISO 5208:2015 Industiral Valves – Pressure Testing of Metallic Valves. Retrieved from https://www.iso.org/standard/65111.html
Manufacturers Standarization Society. (2019). SP-61-2019 Pressure Testing of Valves. Retrieved from http://msshq.org/Store/Details.cfm?ProdID=2241&category=6
This article published by IPP & T, introducing the new Gas Liquid Intelligent Metering Sytem (GLIMS) discusses exactly why the need for dedicated multiphase metering devices has been steadily increasing in recent years and how GLIMS intends to fill that gap.
You can read the full published article in IPP & T’s Flow Measurement Handbook here.
2020 started off with a bang for CGIS. In efforts to expand our brand further into Central and Eastern Canada, and with the end goal of giving customers that same, customer-centric service they see in the West, we’ve joined forces with the like-minded valve repair shop DHB Valves!
CGIS is a highly reputable valve distributor headquartered in Vancouver, BC that specializes in Severe Service Valves (SSVs). We have 40 years of experience working in major industries like oil and gas, mining, pulp & paper and many more. Our business is built on a customer-centric foundation that prioritizes getting the right valve for the application, ensuring the maximum possible return on investment for our customers.
DHB Valves has a similar story. The valve repair, reconditioning, and sales organization is based out of Montreal, QC. They’ve been fixing valves since 1982 and are coming up on 40 years in business. By building strong working relationships with a number of local and national brands DHB has established themselves as a trusted name for valve repair and sales in eastern Canada, handling everything from marine and metric valves to severe service valves and safety valves.
The partnership between DHB and CGIS is designed to grow both brands market potential across the nation. With a combined 80 years of knowledge and experience, customers of DHB and CGIS will see highly tailored, quality solutions. The combination of resources will offer customers first-rate products and services without compromising on quality of service.
CGIS President, Dave Friesen is “very excited to join forces with an organization like DHB who has such a long and impressive commitment to client satisfaction. CGIS believes and has proven that a profound understanding of the customer’s application is the key to long term, reliable valve and automation performance. By partnering with DHB we have expanded our knowledge of the total life-cycle cost which solidifies our ability to help our clients to enhance sustainability, work safer and improve bottom line performance.”
Besides a focus on customer-oriented outputs and service, the collaboration of the two brands will bring the addition of new product lines and a reach into new industries.
DHB president, Marcello Lisi explains he is “extremely pleased to partner with CGIS. This partnership is an opportunity to better serve our customers with the combined strengths of DHB and CGIS. DHB’s policy is to consistently provide quality services that exceed customer expectations. By partnering with CGIS we believe we can serve our customers in a much greater capacity and offer complete turnkey valve solutions.”
DHB Valves and CGIS complement each other not only in the products and services they offer in their respective geographical regions but also in their company values. The partnership of these two brands is set to succeed and their customers will be the ones who reap the benefits.
When it comes to pressure ratings there are many different classifications, both imperial and metric; and while some are easily interchangeable, some are not. Generally, pressure can be defined as the force that is applied on a certain unit of surface area. Regarding valves, pressure classification is the maximum allowable pressure at a specified temperature that can be applied to the body of a valve.
This article has been purposed to provide you with the most up-to-date and accurate information regarding these classifications with respect to valves and pipelines in North America. For starters, we use ASME B16.34 as the North American standard for gauging safe pressure specifications. While this is our standard, many valve manufacturers, distributors, resellers, and end-users see valves that have been imported from various locations around the world. This, along with inadvertent mistakes made when requesting or classifying the valves based on Maximum Allowable Working Pressure (MAWB) has caused a lot of extremely detrimental consequences – for both worker safety and profitability.
Some of the ratings you will see used to describe MAWB:
PSI: Pounds per Square Inch – psi measures the pressure as a one-pound force applied on an area of one square inch. It is important to note that psi should be written as either psig (psi gauge) or psia (psi absolute). When dealing with valves, you can assume you are using psig.
PSIG: Pounds per Square Inch Gauge – They take away the atmospheric pressure (wherever you are) and calibrate the pressure to only represent what your measuring
PSIG = PSIA – 1 atm (where atm is atmospheric pressure)
PSIA: Pounds per Square Inch Absolute – it includes both the atmospheric pressure as well as the pressure of what you are measuring. Atmospheric pressure at sea level is 14.70psi.
PSIA = PSIG + 1 atm
Bar: Metric unit of pressure used to measure the force applied perpendicularly on a unit area of a surface. While it is its own measurement (bar) it is often calculated and remembered in terms of kilopascals kPa (for lower pressures) or megapascals MPa (for higher pressures). It is legally recognized and used in the European Union, and commonly used in Canada as well.
1 bar = 100 kPa = 0.1 MPa
Lbs. or pounds: This measurement is a unit of weight, it sometimes gets used interchangeably with psig or Class (which is a label, not a value), which it should not. If you see this being used, you should double-check the actual working pressure needed. As a general rule of thumb, pounds should not be used as a measurement of pressure.
Cold Working Pressure (CWP) – CWP dictates the MAWP for valves (and other such instruments) that do not meet or comply with ASME B16.34. Many valves do not need to have a pressure rating as high as those recommended in this standard for the applications they will be used for. When this is the case they typically just value the MAWP as psig. For instance, you may have a small, threaded valve that has a MAWP rating of 1500 or 2500 psig, it would be easy to confuse this valve as being Class 1500 or 2500, which would actually need to have a psig of 3705 or 6170 psig*, respectively.
Class: The valve class is a label** based on the material of the valve and temperature of the application. The MAWP is then presented as a function of this as psig for each temperature range. Materials in this standard are rated as either Standard, Special or Limited. You can find all information on valve classes in ASME B16.34, North American Standard here. The original version of this standard uses imperial units since the US was a large influence during its creation, but there is a second iteration that has been converted to metric.
It’s important to know the difference between all of these ratings and measurements as many distributors and industrial plants source equipment from locations all over the world and the wrong attribution of them can cause costly ramifications.
A common test for valves is the Hydrostatic Test Standard, this tests valves at 150% of their MAWP, to ensure they have a safety margin when in operation. The test involves filling the vessel with a liquid – usually water with a coloured dye (to help spot leaks) and bringing the valve to the specified test pressure. When valves go over their MAWP in operation, they can fail causing leakages to atmosphere or worse yet, explode – a huge factor in worker safety.
*For the purpose of examples in this article we have referenced the psig values for B16.34 Group 1.1 Materials (A – Standard Class)
**Valve Classes are labels not “numbers” they don’t have a numerical value in relation to the maximum allowable pressure – ie. Psig.
We’re excited to announce that 2020 marks 40 years of business for CGIS. We’ve built our foundation on the values of Excellence, Team Work, Integrity, Initiative, Fun and Humour, and Continuous Learning and we see our team demonstrating these each and every day. We’re proud of how far we’ve come and excited about where we are going! Here is to another 40 years working hard with and for clients, suppliers, vendors and employees!
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Kevin Niebergall tackles the problem of check valves failing in operation by uncovering why they are failing in the first place and how we can fix it. Kevin’s example of a LNG gas treatment plant in Northern BC is just one instance of this very common issue. This article was published in LNG Industry in October 2019. Read the full article here.
CGIS is very excited to announce that EBRO Armaturen has received their NSF-61/ANSI-61 certification for drinking water applications! Not familiar with NSF/ANSI-61? It’s a set of national standards relating to potable water treatment. It enforces stringent requirements for the equipment that comes in contact with the water – ensuring it’s safe for all to drink.
With such a strong contender in the water and water treatment business, CGIS will be diving into this sector, as we find Severe Service Valve solutions for all of our prospective and current clients.
Interested in EBRO Valves? Check out our product focus video here: EBRO Product Focus.
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CGIS is proud to announce the promotion of Dave Friesen from VP Sales North America to President of CGIS. Mr. Friesen becomes the 3rd president in the company’s history and is reflective of the confidence the board has in his abilities to lead the organization onto greater success while further promoting the Severe Service Valve (SSV) message to the industry.
Through Dave’s 20 years with the organization he has used his abilities and skills to align CGIS with the world’s best manufacturers and solidify our position as the recognized leader in the selection of Severe Service Valves. In this new role, Dave will use his experience and commitment to understanding the application to further shape and grow CGIS as an organization that ensures our customers always get the right valve, well before a dollar is spent.
Dave has been an integral part of CGIS’ current strategy and positioning and we welcome his further leadership and vision for continued long-term growth.
Read more in the Oil Bulletin.
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In water treatment plants all around the world, Sodium Hypochlorite decomposition is an issue. It often starts leaking from the joints of the PVC Piping and fittings used during construction of these plants, creating an unsightly and unsafe mess. Chemline’s ChemFlare system is the ultimate solution to this, eliminating the need for the gluing process for PVC valves in sodium hypochlorite systems. Read our case study here to see how CGIS was able to incorporate this efficient system into the Regional District of North Okanagan Water Treatment Plant.
EBRO’s new impeller valves are great for dry bulk food handlers and food production. Their design eliminates your typical problems of clogging, coagulation, compressing and sticking all while reducing the crushing of the granules. These precision engineered valves help manufacturers improve efficiency and reduce downtime. Read about all the EBRO Impeller Valve features here.
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