Last updateThu, 06 May 2021 8pm


Misconceptions Regarding Control and Isolation Valve Standards

All on/off isolation valve standards are not created equal and cannot be applied unilaterally to all valves. This article references two types of valves: 1. Control valves, which are defined as manipulating a flowing fluid to keep process variables as close as possible to the desired set point; and 2. Isolation or shutoff valves, which have one primary function—to provide tight shutoff to ensure fluids don’t pass downstream.

There are several different standards organizations across process industries, some of the common ones are: API, ASME, ISO, MSS, EN, BS and JIS. Each of these standards will vary with defined criteria and many will defer to other standards for components of a valve’s design such as wall thickness, fire ratings, fugitive emissions or shutoff classifications, to name a few.

High-Pressure Test Enclosures for Valve Assemblies

As drilling operations explore ever greater depths and pressures, operating pressures for new valve assemblies are going beyond traditional limits. The service-duty requirements for new valve designs push the limits of material strengths, in what can be a highly-corrosive and challenging environment. Some testing requirements may reach 50,000 psi (3450 bar) working pressure or higher, with a 1.5 safety factor. Adding to these requirements are new American Petroleum Institute recommendations for testing components under API 598, RP591 and others.

Intermediate Class Valves, the Forgotten Classification

These days, piping designers use automated systems that default to standard classifications such as pressure classes of 150 to 2500 for valves and associated equipment. The identification and use of an intermediate class would require a manual intervention by the designer, and the creation of a specific project level piping class. However, the cost savings can be significant.

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