It’s a jungle out there, so the saying goes. Unfortunately, that jungle extends to and includes your work environment. And if you are responsible for some part of a chemical processing facility, the vines and beasts of that jungle wrap around and through the pipe racks, instrument panels and valves you call home every workday. If this sounds familiar to you then you probably won’t turn down a little survival help.
As an engineer or technician you probably have to deal with valves everyday. Depending upon your job description, you may have to specify, maintain, install, operate or repair any number and type of valves. That is a lot of responsibility. And if you don’t know all the answers, you have to get some help. But whom do you ask? Where do you look?
If you had a tough valve application questions 10-20 years ago, there was probably someone in your organization that held the unofficial title of ‘valve guru’, and he would have the answers based on his years of experience and focused interest. Sadly, the gold watches have taken their toll, and most of these guys have transitioned to the back nine or the back bay.
So where do you turn? Fortunately there is a lot of good information out there. Hopefully this article will give you a few insider tips, as well as point you in the right informational direction.
Everyone involved with the chemical processing industry is concerned about safety. Two of the guiding principles of the CMA Responsible Care Initiative are: “To make health, safety and environmental considerations a priority in our planning for all existing and new products and processes”. And “To operate our plants and facilities in a manner that protects the environment and the health and safety of our employees and the public”. To this end, the quality, integrity and suitability of the valves in the process line must be considered.
OSHA 1910.119 “Process Safety Management of Highly Hazardous Chemicals” loudly echoes the spirit of the CMA initiative. The purpose of section 1910.119 is stated as follows: “This section contains requirements for the preventing or minimizing the consequences of catastrophic releases of toxic, reactive, flammable, or explosive chemicals.” As a valve owner or a person responsible for valve integrity in your plant, that puts a huge burden on you to make the right valve decisions. You have to know that the valve is the right valve for the application and that the materials are suitable for the service media, pressure and temperature.
Additional Testing- Added Insurance
For many generic processes, ample history and application data is available, but some critical services require a measure of added insurance. This can take the form of additional testing requirements for the valves you purchase.
For example, say your operating conditions require a shut-off valve to function at –320oF. This temperature dictates the use of a cryogenic valve with a gas column to shield the stuffing box or packing area from the sub-zero cold and possible icing, which could render the valve inoperable. You must be sure that the valve of choice actually functions as required at the –320oF temperature.
You have two choices. You can trust the judgment of everyone in the supply chain or you can ask to see the cryogenic test results for the valve you are considering. You would learn by reviewing the test data, that valves don’t always perform the same at cryogenic temperatures as they do at room temperature.
Fugitive emissions issues are at the forefront today and valves have been identified as some of the primary culprits. If you have any concerns about the integrity of a valve’s seals and gaskets, ask the manufacturer for copies of fugitive emissions test reports performed on the valve you would like to purchase. The most common fugitive emissions testing procedure performed today is ANSI/ISA 93.00.01-1999, “Standard Method for the Evaluation of External Leakage of Manual and Automated On-Off Valves”. If the report references this specification, you can be comfortable with the scope of the tests.
In addition to this qualification testing, you can have the manufacturer or a valve service company perform fugitive emission testing with either helium or methane on a production basis. There are extra charges for these tests, but if the service is critical, the cost can be easily justified.
When the highest valve component integrity is required, additional nondestructive testing (NDE) can be specified. NDE, including radiography (RT), magnetic particle (MT), ultrasonic inspection (UT) and dye Penetrant examination (PT) is useful for detecting flaws and defects in castings, forgings and wrought materials. If material identification is a concern, a positive material identification (PMI) can be performed on key valve components to confirm their identity.
Special Service Cleaning
Some media, such as oxygen, require that all piping and components be totally free of oil and other contaminates. To achieve this clean state, valves must be completely disassembled and cleaned, utilizing special chemicals, equipment and inspection techniques. Following disassembly and individual parts cleaning, each part is checked with a black light and reassembled in a dust and oil free environment.
After assembly, the valves are usually tested again with either nitrogen or helium. The cleaned and tested valves are then packaged in a heavy plastic bag that is sealed for shipment to the customer. Valve cleaning is very often used for other services, such as chlorine and ethylene oxide, that require an absolutely pristine valve.
What about valve installation? That should be fairly straight forward, right? Actually if you take care and follow all manufacturers installation procedures and recommendations, you should be fine. However, if there are no installation procedures provided by the manufacturer, you could use a little help. The Manufacturers Standardization Society of the Valve & Fitting Industry, otherwise known as MSS, publishes a document called the “MSS Valve User Guide” (MSS SP-92). This document has a wealth of information concerning installation operation and maintenance of various types of valves.
For users of higher alloys, attention must be paid to the weldability of the material for socketweld connections. Due to their microstructure and chemistry, wrought and forged materials are generally very weldable. However the same materials in the cast condition may not weld so easily due to cracking in the heat affected zone of the weld. Alloys such as CN7M (Alloy 20), M35 (Monel) and CY40 (Inconel) have suffered from this condition. As a precaution, a PT inspection should be performed after welding the valve into the pipe run.
Like any other mechanical device, valves eventually need repair or replacement. The frequency of this R&R depends upon the severity of the operating conditions, the design of the valve and the preventive maintenance that has been performed. There are documented cases where valves originally installed at the turn of the century are still operating fine. There are also cases where the environment is so severe, that valves only last a couple of weeks before they need to be repaired.
Although complete replacement sounds like the easiest method, it may not be the best choice. First of all, the cost will be high and second, if the valve is not a commodity type valve, the delivery from the manufacturer may be long.
In addition to a few OEM’s that repair their own products, there are quality independent valve repair companies in most parts of the United States. Many companies say they repair valves, but with the complexity of some of today’s quarter turn products, you need to be sure the company you are dealing with is qualified to handle the job. The Valve Manufacturers Association of America (VMA) created The Valve Repair Council (VRC) 12 years ago to provide a network of OEM authorized and audited valve repair facilities. The 30 members of the VRC are the cream-of-the-crop when it comes to valve repair. So when you are looking for a valve repair facility, look for the VRC authorization.
What does it cost to repair a valve? There is no common answer due to the differences in valve types, however a good rule of thumb for most valves is that the repair will cost anywhere between 40% and 60% of the cost of a new valve.
When specifying new valves it is often important to consider the repairability of a particular type or brand. Oftentimes, that temptingly cheap valve may be difficult or impossible to repair due to design flaws or the high cost and/or lack of availability of parts. When considering a new valve purchase you should look at the total cost of ownership, not just the original purchase price.
Press F1 For Help
Most valve manufacturers and distributors are usually glad to offer valve application or operation assistance. However you must consider that the salesman may not have the engineering background to answer specific technical questions. Due to liability concerns, even some manufacturers are hesitant to go out too far on that informational limb. It is also very unlikely that one manufacturer will give you much information about a competitor’s product. If you have several different brands from different distributors, your information search may turn into more of a scavenger hunt.
More survival help can be found in the publications of the various standards making organizations. Virtually all valves are built to both material specifications and one or more industry codes or standards. There are standards and specifications covering virtually every type of valve from plastic industrial ball valves to instrument valves. While the primary purpose of these documents is to produce standardized products, there is a wealth of general information contained in their pages. These documents and the organizations that publish them are a good starting point.
For control valves, the primary organization is The Instrument Society of America (ISA). ISA has a number of standards that deal with control valves, from end-to-end dimensions to testing requirements. The organization also offers control valve training courses at various sites around the country.
The oldest valve standards-making organization in the United States is MSS. Their first standard was published in 1924 and the organization estimates that it has distributed over 50,000 standards documents during its 78-year history. The MSS inventory currently includes 72 valve related standards.
The American Petroleum Institute (API) publishes several valve standards. Gate valves, ball valves, corrosion resistant gate valves and valve inspection & testing are some of the topics covered by their standards.
The American Society of Mechanical Engineers (ASME) has a long history of standards creation and stewardship. The most important ASME valve document is B16.34, “Valves- Flanged, Threaded and Welding End”. The heart of the document is the 60 page pressure-temperature ratings section. These tables cover virtually all of the common valve materials in use today including stainless steels and nickel alloys. B16.34 also contains design information and non-destructive inspection procedures.
The American Society for Testing & Materials (ASTM) does not publish valve standards, but they do produce the material specifications used for the manufacture of the valve components.
Historically, valve standards have been dominated by the above-mentioned standards making bodies, however the landscape is changing. Increasing international participation, combined with decreasing US participation has opened the door to ISO valve standards acceptance worldwide. In some cases US standards have been adopted verbatim, but the current trend is to totally new documents created from scratch by European dominated committees.
Much like squirrels storing acorns for the winter, most engineers seem to store information (books, reports, pamphlets, etc.) for possible later reference. When it comes to valves, there are some excellent volumes available to help keep that bookshelf firmly anchored to the floor. During the past 20 years eight excellent valve books have been published.
Control Valve Selection and Sizing, by Les Driskell, Instrument Society of America, ISBN 0-87664-628-3. This is the control valve bible. Virtually everything you need to know about these valves is there from sizing to trim types and applications.
The Valve Primer, by Brent T. Stojkov, Industrial Press, ISBN 0-8311-3077-6. This little book (4.5” x 7”) is not only easy to carry around, but is the best basic valve book available.
The Chemical Engineering Guide to Valves, by Richard Greene & Chemical Engineering Magazine, McGraw-Hill, ISBN 0-07-024313-1. This book is a compilation of various reprints from Chemical Engineering magazine. Highlights include excellent articles on valve installation and selecting and specifying valves for new plants.
Valve & Actuator Technology, by Wayne Ulanksi, McGraw-Hill, ISBN 0-07-019477-7. While containing a lot of basic valve information, Ulanski’s book focuses much of its attention on valve actuation.
Valve Handbook, by Philip Skousen, McGraw-Hill, ISBN 0-07-057921-0. This handbook almost takes two hands to lift. Its 726 pages cover virtually all valve subjects. A complete reference work, although slightly heavy on the control valve material.
The Valve Book, edited by Pirjo Sparig, Neles-Jamesbury, As you might expect from ball valve giant Neles-Jamesbury, this book is heavy on quarter-turn valves. Highlights include much data on seat construction and operation, including offset types.
Lyon’s Encyclopedia of Valves, by Jerry Lyons & Carl Askland, Van Nostrand Reinhold, ISBN 0-442-24961-6. The Lyon’s book is truly a reference work with most of its pages devoted to a valve terminology glossary and fluid power symbols.
Valve Selection and Specification Guide, by Ronald C. Merrick, Von Nostrand Reinhold, ISBN 0-442-31870-7. Merrick’s book is different from the other texts in that he gives extra attention to valve specifications and procurement. The volume also contains a good basic valve overview, with a focus on construction details.
Although not valve books per se, there are two excellent general corrosion books available, to help you make sound material selections. Corrosion Control in The Chemical Process Industries, by C.P. Dillon and published by the Metals Technology Institute of the Chemical Process Industries, is a great overview of chemical process corrosion and materials. Corrosion in the Petrochemical Industrypublished by ASM International is probably the best overall chemical and petrochemical corrosion book. Its 500 pages cover materials, case histories and forms of corrosion.
Since the valve book market is small, most of the above mentioned books are not always available at technical bookstores. However they are usually easily located on the Internet used book marketplace at sites such as www.bookfinder.com.
It would be nice if all the valve information we were searching was available on-line. But so far there is only a smattering of easily obtainable data. Most of what is there is available on manufacturers websites. Many of these sites now offer PDF catalog and document downloading.
Reference books and documents will never replace practical valve experience, but the combination of the two might help create the next “valve guru” in your organization. If there is a local valve service facility, call and get acquainted, these guys are the front lines of valve technology and most are glad to offer assistance or even have you come into their shop for some hands-on experience.
Armed with a good attitude and the right survival gear you can brave the valve jungle. Don’t be afraid to ask when you don’t know and remember that it is your responsibility to care about the valves under your control.
|Useful Web Addresses|
|Web address||Organization notes||Notes|
|www.mti-link.org||Materials Technology Institute||Books and information materials and procedures in the chemical industry|
|www.api.org||American Petroleum Institute||Standards Making Organization|
|www.mss-hq.com||Manufacturers Standardization Society||Standards Making Organization|
|www.isa.org||Instrument Society of America||Control Valve Information|
|www.nace.org||NACE International||Prime source for corrosion information|
|www.global.ihs.com||Global Engineering Documents||One stop source for all standards purchases|
|www.chemicalprocessing.com||Chemical Processing Magazine||Information and archived articles on the Chemical Processing Industry|
|www.bookfinder.com||Bookfinder Search Engine||Used book search engine|
|www.abebooks.com||Abebooks Search Engine||Used book search engine|
|www.powells.com.||Powell’s Search Engine||Used & new book search engine|