It's a jungle out there," as the saying goes. Unfortunately, that jungle can extend to and include your work environment. And if you are responsible for some part of a chemical processing facility, the vines and beasts of that jungle can 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 will not turn down a little survival help.
As an engineer or technician you probably have to deal with valves everyday. Depending on your job description, you might have to specify, maintain, install, operate and/or repair a number of different valves. If you do not 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 question 10 or 20 years ago, someone in your organization holding the unofficial title of "valve guru" probably would have had the answers, based on his experience and focused interest. Sadly, the gold watches have taken their toll, and most of these gurus have transitioned to the back nine or the back bay.
Fortunately, a lot of good information currently is available and accessible. This article aims to provide you with a few insider tips, as well as to point you in the right direction for additional information.
Everyone involved with the chemical processing industry is concerned about safety. Two of the guiding principles of the American Chemistry Council's (ACC) 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 process-line valves must be considered.
The U.S. Occupational Safety and Health Administration's (OSHA) Section 1910.119, "Process Safety Management of Highly Hazardous Chemicals," loudly echoes the spirit of the ACC initiative. This section "contains requirements for preventing or minimizing the consequences of catastrophic releases of toxic, reactive, flammable or explosive chemicals," according to OSHA.
As a valve owner or a person responsible for a plant's valve integrity, you are expected to make the "right" valve-related 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.
For many generic processes, ample history and application data are 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, if your operating conditions require a shut-off valve to function at -320 Degrees F, the valve must meet certain criteria. 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 the valve of choice actually functions as required at the required temperature.
You have two choices. You can trust the judgment of people in the supply chain or you can ask to see the cryogenic test results for the valve under consideration. A review of the test data would indicate that valves do not 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 emission test reports performed on the valve. The most common fugitive emissions testing procedure performed today is the American National Standards Institute/Instrumentation, Systems and Automation Society (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, you can ask the manufacturer or a valve service company to perform fugitive emission testing with either helium or methane on a production basis. These tests cost extra, but if the service is critical, the cost can be justified easily.
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.
Installing and repairing
What about valve installation? That should be fairly straightforward, right? Actually, if you take care and follow all the manufacturer's installation procedures and recommendations, you should be fine. However, if the manufacturer does not provide installation procedures, you might need 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 valve types.
Cryogenic testing is performed to verify valve operation at cryogenic temperatures.
Users of higher alloys must pay attention to the weldability of the material for socketweld connections. Because of their microstructure and chemistry, wrought and forged materials are generally very weldable. However, the same materials in the cast condition might not weld so easily as a result of 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, the plant should perform a PT inspection after welding the valve into the pipe run.