Once upon a time, most large refineries and chemical plants had their own valve shops, complete with a full compliment of experienced valve repair technicians. These service departments took care of most of the plants repair needs, although oftentimes valves were simply replaced rather than refurbished.
During the boom times of the 50’s and early 60’s the valve repair industry took root and blossomed, as end-users began to divest themselves of most valve repair functions. The emergence of dozens of small to medium sized valve repair companies all across the country helped fill the vacuum left by the closing of the plant owned valve repair shops. A few manufacturers such as Crane and Pacific got in on the repair action by establishing their own service centers at select locations around the country.
It was actually easier to repair valves back then. The basic design of steel valves manufactured in the United States changed little for the first 75 years of the 20th century. Due to their over-engineering, in the days before finite element analysis (FEA), many of these “tanks” held up to decades of service, as well as many repair cycles. Ask virtually any long-time valve repair hand, and most will choose to repair a 40 year-old cast steel gate valve, rather than one of the newer designs.
Inexpensive imports began replacing the domestic products as the 70’s turned into the 80’s. During this period, some of the major valve manufacturers saw the advantage of authorizing independent valve shops to repair and modify their products. These authorized facilities helped provide an ever-improving level of service for the end-user community. Finally, a repair facility could get information that was previously considered proprietary, yet was necessary to correctly service a manufacturers product. The net result was better service to the end-users.
As the quantity of valve repair and service increased, so did the level of bogus and fraudulent valve work and product misrepresentation. Valve repair companies with only a desire to make a quick buck proliferated through the 80’s. The “bogus valve” epidemic culminated in several successful lawsuits, as manufacturers sought to regain some of their lost prestige. Prestige lost at the hands of crooks who made valves new again merely by attaching a new fraudulent tag.
In 1990, the Valve Manufacturers of America (VMA) established the Valve Repair Council (VRC) to help protect its members and customers from the hazards of improperly repaired bogus and counterfeit valves. The formation of the VRC helped end-users to choose quality valve repair facilities. To be a member of the VRC, a valve shop has to be sponsored by a VMA member as well as submit to an independent quality audit.
Repair Standards & API RP 621
Traditionally, the repair standard or specification was provided to the repair shop by the end-user. This resulted in repair shops maintaining an inventory of many different valve repair documents. While the standards were different, they had many points in common. In an effort to try to standardize their valve repair specifications and thus lower valve repair costs, end-users and valve repair shops established an ad-hoc committee charged with creating a common valve repair standard. Companies such as Exxon, Shell, Dow and others initially agreed to a basic common repair document. This basic document was then presented to API for possible conversion into an API standard. An API work group was formed and the document, API Recommended Practice 621 “Reconditioning of Metallic Gate, Globe and Check Valves”, was created.
Adoption of API 621 was not easy. There was a very real battle between the end-user community and the valve manufacturers. The primary concern voiced by the manufacturing community was the increased liability that such a document might create for them, since deviations from original manufacturing dimensions are allowed in the document. Key areas of deviation include: valve end-to-end dimensions, flange thickness, shell wall thickness and stem diameter.
Another manufacturer concern was that valve refurbishers would use the document in order to sell more rebuilt product to end-users. Although the document states in its scope: “This RP does not cover reconditioning or remanufacturing of used or surplus valves intended for resale. The only intent of this RP is to provide guidelines for refurbishing an end-user’s (Owner) valves for continued service in the Owner’s facility.” To gain increased legitimacy of his product, the potential rebuilder/seller could say that his valves were rebuilt in accordance with API RP 621. If this does occur and the valves were rebuilt in accordance to the guidelines of RP 621, at least the valves would have been rebuilt to a baseline standard where none existed before.
Now for the first time, there is a standardized procedure for the repair of gate, globe & check valves. This should streamline the valve repair quotation process, as well as elevate the overall quality of valve repair. RP 621 will also help separate the “wheat from the chaff” when it comes to specifying a valve service provider. The standard contains requirements that cannot now be met by some of the lower end valve repair companies. These companies will have to add additional equipment and/or expertise in order to repair valves to the new specification. As RP 621 becomes adopted by more and more end-users, the net result should be a distinct increase in the quality of valve repair.
The “Valve” Information Age
Today, the valve repair/service function can provide much more than properly repaired valves. It can provide valuable product information and feedback. Today’s state of the art valve repair programs are designed to record, through a series of visual inspections and measurements, valuable data on how a particular valve performs in service over time. Some of the more common measurements include: valve end-to-end dimension, flange thickness, stem diameter, stuffing box diameter and wall thickness at multiple locations. By comparing the data after each repair “turn”, the repair facility can provide valuable cost saving data to the end-user/owner on how particular valve brands, sizes and types perform. For example, armed with this data, the end-user can weed out valve manufacturers from its Acceptable Manufacturers List (AML) whose valves are consistently unrepairable, or due to design idiosyncrasies are just too expensive to repair. All top-notch valve repair facilities have shop floor computer systems to easily gather and collect this information.
The general economic rule of thumb for the repairability of a valve is not to exceed 50% of the new valve replacement price. For “commodity” type gate, globe & check valves, the repair costs on the Gulf Coast run anywhere from 40% to 75% of new valve costs, depending upon size, material and pressure class. With today’s influx of inexpensive imports, the cost of repairing the smaller (2” – 6”) plain carbon steel valves exceeds the 50% rule more often than not. However, due to corners cut in manufacturing, these inexpensive valves are scrapped rather than repaired at a much higher rate. The end result is that after a period of years the inexpensive valve may have to be replaced more often than the more heartily built valve with a higher original cost. Other factors such as stem-to-wedge guiding, seat geometry and shell design make certain valves more expensive to repair than others.
Choosing a Repair Facility
If your company is considering a valve repair program, the first consideration is choosing the right repair facility. In years past, many valve repair contracts were let to the company that was either the lowest bidder or had the biggest bass boat. Fortunately the “Bubba” era of valve repair facility selection is just about gone, having been replaced by quality, capability and OEM authorizations.
The first criteria for choosing a valve service vendor should be membership in the Valve Repair Council (VRC). By choosing a VRC member you are getting a pre-qualified service company that has been recognized for its quality and service level. For example, there are 55 valve repair companies listed in the Greater Houston Yellow Pages; only four are members of the VRC. They are: United Valve, Paradigm Valve Services, Crane-Groth Valve Services & Kirksey Machine. These member companies provide varied services on virtually every type of valve and actuator.
The next consideration for choosing a valve service provider should be factory authorizations and alliances with the manufacturers of predominant or key valves in your plant. These authorizations ensure the best possible flow of spare parts and engineering support between the manufacturer and the valve service provider, which is so important with today’s high performance quarter turn products. Improper repair of some of these highly engineered valves can be catastrophic.
Virtually every reputable valve shop will have a well-documented quality program. Some may even have ISO 9000 certification. At the very least the valve service provider should demonstrate that they have the following quality system components:
Valve Shop Equipment
Equipment and facilities are important criteria when choosing a valve service provider. A clean well-lit shop environment not only makes a good first impression, but is a good indicator that the facility takes pride in its workmanship. Since valve repair often involves machining and welding operations, this equipment should be inspected for service suitability and capacity. If you have large (NPS 24” and up) diameter valves that need repair, look for a facility with large boring mills and lathes, as well as a good five ton or better overhead crane system. If your valves are not large, say NPS 6” and smaller, the large machines and cranes are obviously not necessary. Newer lathes, milling machines and CNC machining centers are a good sign that the valve shop strives for the highest quality from its machining department.
The weld shop should contain a variety of welding machines, fixtures and positioners to allow the welding to be done in the most productive manner. The presence of welding processes such as submerged arc welding (SAW), Tungsten Inert Gas (TIG) and flux-cored arc welding (FCAW) usually denote a fully capable and equipped welding shop. There should also be digital temperature measuring devices or heat sensitive crayons present to confirm preheat and interpass temperatures.
Many welding procedures require a post weld heat treatment (PWHT) following welding. This requires furnaces of adequate size, or in some cases, localized stress relief equipment. Welding of Chrome/Moly valves or valves for NACE MR0175 sour service require PWHT in almost every case. The best-equipped shops will have their own ovens to perform this process in-house.
Cleaning and assembly areas should be spacious and not encroach upon the machining and welding areas. Shot and sand blasting generate dust and debris that can damage finished machined surfaces. These operations should be separated from other areas of the shop. The assembly areas should have cranes sufficient to handle the largest valves worked on in the facility.
Nondestructive evaluation (NDE) and inspection equipment is now standard fare for quality valve service companies. This equipment ranges from the very basic dye penetrant kits to in-house x-ray radiography. Here are some NDE and inspection items present in valves shops today:
1) Portable Rockwell hardness test machine
2) Bench type Rockwell or Brinell hardness test machine
3) Granite surface plate
4) Dye Penetrant (PT) testing kit
5) Ultrasonic “D meter” for wall thickness measurement
6) Positive Material Identification (PMI) machine for alloy verification
1) Magnetic Particle (MT) yokes
2) Electronic surface roughness indicator
3) Electronic hardness tester
1) Ultrasonic flaw detector
2) Radiographic facility
3) Helium or Methane leak detector for fugitive emissions testing
Following reassembly, all valves need to be pressure tested. The well-equipped shop should have a variety of valve testing machines to handle valves of all types and pressures. In valve testing, one size test machine does not fit all. If the shop will be testing buttweld valves, special mechanical or hydraulic ram type machines with multiple end adapters are required. While in some cases a valve may be tested by bolting flanges on, this is a very time consuming and costly method of production testing of repaired valves.
The Future of Valve Repair
If you have been in the valve business for any length of time, you know the one constant you can count on is change. The once dominant list of domestic valve manufacturers has now shrunk to a precious few, while their customers, the end-users, have shrunk themselves through the mergers and acquisitions of the last 10 years or so. The valve repair industry is also in a state of change. “Merger Mania” has hit the industry during the past two years and shows no signs of letting up.
In the past, repair programs were usually local in nature, with the local plants contracting a local repair vendor. However, with the number of end-user mergers, the number of contracts has shrunk proportionally. Some of the larger end-user companies are now contracting with a single valve service company to handle all of their repair and service work on a national or even global basis.
One trend that is becoming more prevalent is the acquisition of valve service shops by some of the larger diversified valve manufacturers. It remains to be seen how an industry that has traditionally been centered on customer service and one-on-one relationships fares, as the realities of large corporate bureaucracy are instilled upon them.
Another growing trend in the valve repair industry is the Valve Management Program. Although the details can vary, and are custom tailored to the needs of the particular end-user, the program creates a single source for all valve related activity. This can include new valve pre-testing, valve modification and repair. Aside from lowered costs, these programs allow the end-user much greater control over the valves that enter the plant. New valve pre-testing programs serve as an additional QA inspection that often catches problems that slipped through the manufacturers testing and inspection programs. The modification of valves for special service applications becomes interactive, as the plant engineering department and the repair/service facility engineers communicate closely to solve valve related issues. Additionally, more valve information is gleaned as pre-tested valves are serialized and dimensionally checked prior to installation.
Although the playing field, as well as some of the rules are changing, the basics of repairing valves to extend their service life is still the same. Valve repair in the 21st Century promises to be technologically advanced, with data and digital imagery being exchanged between the repair facility and the end-user. But when you break the repair process down to the lowest level, there will still be skilled valve technicians armed with a set of wrenches and a tube of “Prussian Blue”, performing basic operations that have changed little over the past 100 years.