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Across many types of products in a wide selection of industries, the practice of combining assorted elements from numerous sources all over the world is the rule, not the exception. Should this be a concern for a management valve user? For instance, when an end user discovers that several elements are being made in China (Figure 1), ought to the user worry in regards to the quality?
When dealing with a serious valve vendor, the answer is “no.” There shouldn’t be any room for doubt when the seller has a quantity of checks and balances in place specializing in product high quality to ensure control valves operate as designed, need minimal upkeep, perform safely and operate within environmental rules.
Yet, regardless of such efforts by the vendor, a management valve user might have questions about world sourcing and the nation of origin. This article discusses how one major management valve vendor ensures product high quality. Many other management valve vendors observe the identical or similar procedures.
Quality specification brings international assurance
Emerson enforces a complete quality specification for its Fisher management valves that should be met by suppliers of pressure-containing and structural steel castings. The high quality specification includes more than a dozen necessities that apply to the following areas:
Supplier qualification
Welding procedures
Marking inspection and testing
Tryout and sample castings
Production castings
Certification of compliance
Supplier qualification — Suppliers undergo a rigorous qualification course of. The process totally investigates a possible supplier’s capacity to satisfy materials specifications and relevant worldwide codes and standards — as well as specific requirements related to part manufacture. In the case of castings, a foundry is taken into account “qualified” when it passes a critical evaluation by Fisher’s engineers.
The foundry should demonstrate a report of qualification by a third-party inspection company and conform to varied standards, such as ISO 9001:2000, ASME, A2LA, PED and others. It should move a evaluate of its quality program as well as on-site audits of the foundry’s processes and procedures corresponding to welding, heat remedy and non-destructive examination. Additional proof of performance is determined by analysis of tryout castings to confirm specs are met.
Welding procedures — Welding is used in the course of the manufacturing and upgrading of castings, similar to when radiographic examination is required. Welding requirements state that procedures and welder qualifications must meet ASME Section IX (or EN ISO 15614-1 and ISO 9606-1) qualification requirements. Similarly, each lot of weld filler must comply with ASME/AWS chemical analysis specifications. In Europe, compliance should be to EN499. Weld filler must have actual chemistry.
Marking inspection and testing — Valve physique castings have markings (Figure 2) that determine the foundry that poured the casting and that indicate the heat code. Material identification can also be usually shown on the body casting, corresponding to CC, CF8M, CN7M and others.
Casting เกจ์วัดแรงดันน้ำมันเครื่อง — Emerson technicians conduct each visual inspections and mechanical tests on pressure-retaining castings.
As-cast exterior and inside surfaces are inspected visually for unacceptable irregularities, together with scorching tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing includes a hydrostatic strain take a look at to substantiate the leak tightness of a management valve’s pressure-retaining elements, including the body and bonnet castings. The take a look at process involves a fixture that closes off cavities that might be pressurized in service after which topics the component to the hydrostatic shell take a look at stress appropriate for the valve body material and sophistication.
ASME B16.34 units out the hydrostatic test pressure to make use of for steel and alloy valves. It’s calculated by multiplying the working strain by 1.5 and rounding to the following larger 25 psig increment. Any visually detectable weeping or leaking via the strain boundary walls which are a part of the valve meeting is a compulsory trigger for rejection (Figure 3).
Compliance with these specifications should be ensured, as properly as with other necessities relating to supplies.
Figure 2. Markings identify the foundry and materials of the valve body. These management valve bodies have been forged at an Emerson-approved foundry in China.
Meeting material necessities
Valve casting integrity and high quality begins with specs that decision not just for premium supplies, but also for the supplies that work best within the supposed purposes. These software requirements embrace power and ductility in addition to resistance to certain factors, together with the make-up of the controlled fluid, working temperature and flow velocity.
For instance, chemical composition should be controlled precisely to realize an alloy’s meant efficiency degree. Carbon metal castings for valves intended to be used in oil and gasoline applications should meet NACE SP0472 suggestions that chemical composition be controlled to lower than 0.43% carbon equivalency. The lower carbon content material improves weldability and reduces the potential for stress cracking by hydrogen sulfide typically present in oil and gasoline production and processing functions.
Another instance of materials tied to a particular software embrace these for upstream oil and fuel manufacturing. Many of these purposes occur in the arctic areas of Russia and Canada. For this service, castings are ASME SA 352 Grade LCC, while forgings must meet ASME SA 350 Grade LF2.
Many merchandise with global use now adjust to dual materials specifications to fulfill ASME and European requirements. For example, metal castings are specified and certified to each ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson typically adds its personal stringent necessities similar to the heat treating of excessive nickel alloys, extra demanding chemical composition or special welding procedures.
In the past, Emerson has supplemented typical ASTM and ASME specs to realize the improved corrosion-resistance ranges and excessive temperature capabilities supplied by high-nickel alloys. This is now completed by the brand new ASTM specification A990, which addresses each materials composition and quality.
Figure three. Pressure-retaining parts of a valve are subjected to hydrostatic testing to gauge the parts’ integrity. Visible leakage or seepage through a casting means computerized rejection.
Qualifying a foundry
As a half of a prospective foundry’s qualification, Emerson inspects and checks Fisher valve castings. Non-destructive testing radiography is used as a monitoring tool. ASTM A990 Class C requires radiography of the primary casting of each pattern. The acceptance criterion is Level three for categories A, B and C. For categories D by way of G, no cracking, scorching tears or inserts are allowed as specified in ASTM A990.
High-nickel alloy castings present improved performance in corrosive services and elevated temperatures. However, if high-nickel castings are improperly ready, they’ll pose major problems, including poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification course of could be adopted to keep away from these casting difficulties.
The foundry must cast a 1-inch thick high-nickel check plate (Figure 4) that meets ASTM Material Specification A990. It’s tough to solid due to the difference in cross-section between the base of the weld cavity (in the center) and the general 1-inch thickness of the plate. The cavity of the poured plate is then full of an identical composition weld material. The welder and process for this step should meet the requirements outlined in Section IX of the ASME Boiler and Pressure Vessel Code. Test bars (3/8-inch thick) are cut from the plate and bent over a 1½-inch mandrel per ASTM A990 right into a U-shape.
The bars are examined carefully for cracking alongside the weld heat-affected zone, casting grain boundaries or dendrite boundaries. Failure to satisfy quality requirements will outcome within the disqualification of the foundry from further consideration. Casting patterns have to be devoted solely to high-nickel alloy service. Use of carbon metal or a stainless-steel pattern is unacceptable because of differences in solidification properties.
Shrinkage rates for gates, risers and different equipment can vary considerably. Once the devoted sample tools for each of those elements has been secured, try-out castings are poured for each pattern-alloy combination. The castings are then radiographed.
The intent is to reveal any inherent casting defects — corresponding to shrinkage — that need to be eliminated by modifying the pattern rigging.
Figure four. In a foundry analysis, a casting is full of weld filler, then sliced to yield a bar for bend testing.
A qualified foundry
Emerson has used a Chinese foundry (Figure 5) to cast Fisher valve our bodies for greater than a decade. After an exploratory visit by procurement and manufacturing specialists, followed by an in depth qualification process, the foundry was accredited and has been delivering high-quality valve body and bonnet castings to Fisher valve manufacturing sites.
To assist guarantee the quality of the castings it produces, the Chinese foundry has implemented worldwide standards and has obtained certifications for German TUV and CE, Norway DNV, German Lloyd’s and American ABS, and has handed international high quality system certifications of ISO 9001 and QS -9000.
The foundry has been awarded Gold Medals three times consecutively within the Beijing International Casting, Forging and Industrial Boiler Expo. It has twice obtained an Excellent Supplier award from Emerson.
Figure 5. This Chinese foundry meets all specs for casting valve bodies.
Summary
Control valve users could be concerned once they be taught certain valve elements usually are not made in the U.S. or Europe, however elsewhere. Perhaps their concern stems from experience with other inferior products, such as home equipment, clothes or electronics made in those nations and sold on-line. But if the valve parts are being provided to a significant management valve vendor that has gone to nice lengths to qualify the foundry or provider, then customers can be assured the valves meet all specs.
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