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All aspects of valve design, functionality, inspection and testing are covered in dozens of ASME, API and MSS documents. This dizzying amount of codes, standards and specifications can make the specification and procurement of valve products a job for only a seasoned valve engineering expert. Unfortunately, gold plated watches and summer retirement homes have taken their toll, by drastically reducing the number of experienced valve trained personnel familiar with valve specifications and standards.
This situation puts more responsibility on both the manufacturer and valve purchaser/specifier. A good understanding of the primary standards affecting these products is paramount. I recommend that anyone involved in specifying or purchasing valves have current copies of all the valve standards that apply to the products being purchased.

Here are capsule summaries of some of the more common valve specifications used in the petrochemical & refining industry today.

Gate Valves

For users of gate valves, API 600 is the key document. It details all design and material criteria. API 600 also lists important dimensions such as stem diameter minimums, wall thickness and stuffing box size.

Small carbon steel gate valves such as the forged 150#, 300#, 600#, 800# & 1500# class valves manufactured by several companies worldwide are covered by API 602. This specification covers the same details small forged gate valves that API 600 does for larger valves. API 602 further gives dimensions for extended body valves which are used extensively in industrial facilities.

Another important gate valve specification is ASME B16.34. This document gives extensive details on valves built to ASME boiler code pressure temperature ratings. One important area in which API 600 differs from ANSI B16.34 is minimum wall thickness. API 600 requires a heavier wall for a given pressure rating than does ASME B16.34. API 602 also requires a heavier wall for 150#, 300# & 600# classes than does B16.34.

Testing

Valve testing specifications have come a long way since the early days of the steel valve business. Looking through valve manufacturers' catalogs of the 40's and 50's you see a multitude of pressure ratings and test pressures listed. Part of the problem was indeed lack of standardization. Many products were rated with working pressures (i.e.. 800 psi WOG - which meant 800 psi working pressure for water, oil or gas service), instead of the pressure classes we are accustomed to today. Standardized ASME/ANSI pressure classes have alleviated this confusion as to pressure/temperature ratings and test pressures for most steel valves.

The defacto test specification today is API 598 "Valve Inspection & Test". First drafted in 1974, this document lists all of the test parameters and procedures to be followed for production testing of valves. Most metallic seated valves larger than ANSI 2" size have an allowable leakage rate; this is listed in API 598 as well. Some valve types such as bronze gate, globe & check valves are usually not tested per API 598. These are normally tested per MSS SP-61 "Pressure Testing of Steel Valves".

Occasionally the chemical or refinery valve specifier will see reference to API 6D - "Pipeline Valves". This document is a thorough standard covering the design, materials and dimensions of valves for pipeline service. The most common reference for non-pipeline use are the testing requirements which differ slightly from API 598. The primary difference being 6D's zero allowable leakage on closure tests. Since most of the valves built to API 6D are resilient seated, this is no problem, however when the test standard is applied to metallic seated wedge gate, globe or check valves, compliance can be difficult.

What about globe & check valve standards? Conspicuous in their absence are the steel globe and check valve standards. There is always some talk at valve industry gatherings about globe valve specifications, but so far there has been no action. Due to the inroads that quarter turn valves have made in a field once dominated by globe valves, there probably won't be any specification in the near future. Most designers and specifiers will use ANSI B16.34 as far as applicable for their globe and check valve specifications. Great Britain's British Standards Institute does have two standards that address globe valves: BS 1873 "Steel Globe Stop and Check Valves For The Petroleum, Petrochemical and Allied Industries" and BS 5352 "Steel Wedge Gate, Globe and Check Valves 50mm (2") and Smaller For The Petroleum, Petrochemical an Allied Industries.
NACE MR0175

While not a standard, but a recommended practice, the National Association of Corrosion Engineers (NACE) specification MR-01-75, "Standard Material Requirements for Sulfide Stress Cracking Resistant Metallic Materials For Oilfield Equipment" is almost treated as a standard in many industries. MR-0175 was first published to help solve problems with material failures caused by the presence of hydrogen sulfide (H2S) in oil well equipment and gathering facilities. Although created as an "upstream" equipment document, MR0175 has been adopted by numerous industries and agencies. MR0175 lists materials (by UNS number) and fabrication techniques.

Designed to lessen the likelihood of H2S induced cracking, "NACE" trim as it is often called, is specified quite often for use in refinery processes. The most common "NACE" trim materials used in valve construction today are 316ss, Monel and Stellite.

ASME Codes

Although not valve standards as such, there are three important ASME documents that are important to fabricators welding valves into piping components and manufacturers utilizing welding in the manufacturing process.

First is ASME B&PVC, Section IX "Welding & Brazing Qualifications". This document addresses welding procedures, welding procedure qualifications and welder certifications. Most, if not all, pressure vessel welding codes specify Section IX as part of their process.
The other two are "construction" codes. ANSI/ASME B31.3 "Chemical Plant And Petroleum Refinery Piping", details the fabrication, assembly and nondestructive testing of piping systems, which include valves. Many valve manufacturers utilize B31.3 for their in-house fabrication procedures. The other construction code is Section VIII, "Rules For The Construction of Pressure Vessels - Division 1", of the B&PVC. Code. Section VIII also details fabrication, assembly and nondestructive testing requirements. There are additional construction codes used for pipeline, power and refrigerated piping industries.

Several non-domestic standards organizations publish valve standards, including the British Standards Institute (BSI), International Standards Organization (ISO) and The Canadian Standards Organization (CSA). BSI publishes several standards covering areas that U.S. valve standards writers have ignored such as: globe valves - BS 1873 & BS 5352, cryogenic valves - BS 6364 and steel check valves - BS 1868 & BS 5352. These documents are excellent starting points for persons needing guidance in these particular areas.

The Future For U.S. Valve Standards

What does the future hold for United States valve standards? As more and more valve production moves to foreign soil, unfortunately so does some of the power to direct and control valve standards. During the past several years there has been cooperation between the International Standards Organization (ISO) and US valve standards makers, however some domestic standards making bodies have justifiably been reluctant to give up total control of documents they have invested much time, effort and expense in creating, for a return of relatively nothing.

The biggest dark cloud over the horizon for domestic standards organizations is the debate over metrification. If future valve and fitting standards take on more of an ISO flavor, the costs could be considerable. Metrification can be either "soft" or "hard" in terms of change from our imperial measuring units. Soft metrification merely changes the current unit of measurement to metric while maintaining the actual measurements. Hard metrification on the other hand, will not only change units of measure, but actually change dimensions. Obviously hard metrification is a major economic factor to be faced by valve manufacturers and end-users currently using or manufacturing valves and fittings.

All of the specifications listed in this article can be ordered from the sponsoring agencies, but there are other sources as well. Information Handling Services (IHS) in Englewood, Colorado offers many standards packages on CD ROM. There are many advantages to having the specification on computer, such as the ability to look up subjects by key word. However the biggest advantage has to be the automatic yearly update service, which insures you always have the latest copy of each cataloged specification. This update service helps meet the "most current document" requirements of ISO 9000 quality programs.

Two technical bookshops that carry extensive inventories of standards and specifications are Brown Book Shop in Houston, TX and Global Engineering Documents in Englewood, CO. Global also has a large inventory of obsolete and out-of-date specifications.
Over seventy-five years of valve standards have helped the refining and petrochemical industries grow and prosper throughout the world, with assured interchangeability of products by different manufacturers, as well as timely design changes. The committees that formulate these standards are hard working volunteers who care a great deal for their industries and the people affected by them. Standards committee meetings sometimes take on the air of a hearty democrat vs. republican congressional debate, but as the manufacturers state their case and the end-users theirs; the end result usually ends in acceptable compromise.

As long as these concerned, motivated industry representatives are writing the standards we must all work with, the industry can feel secure that present and future valve specifications will reflect the changing needs of the industry and the general public.