Valve sourcing goes international

Across many kinds of products in quite a lot of industries, the apply of mixing assorted elements from varied assets around the world is the rule, not the exception. Should this be a priority for a control valve user? For instance, when an end person discovers that several parts are being made in China (Figure 1), should the consumer worry concerning the quality?
When coping with a major valve vendor, the reply is “no.” There shouldn’t be any room for doubt when the vendor has multiple checks and balances in place focusing on product high quality to ensure control valves function as designed, want minimal maintenance, carry out safely and operate within environmental rules.
Yet, regardless of such efforts by the seller, a control valve person could have questions about international sourcing and the nation of origin. This article discusses how one major control valve vendor ensures product high quality. Many other management valve vendors follow the same or related procedures.
Quality specification brings global assurance
Emerson enforces a comprehensive quality specification for its Fisher control valves that should be met by suppliers of pressure-containing and structural metal castings. The quality specification consists of greater than a dozen necessities that apply to the following areas:
Supplier qualification
Welding procedures
Marking inspection and testing
Tryout and pattern castings
Production castings
Certification of compliance
Supplier qualification — Suppliers endure a rigorous qualification course of. The course of completely investigates a possible supplier’s capability to fulfill material specifications and applicable international codes and standards — in addition to specific requirements associated to element 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 show a document of qualification by a third-party inspection agency and conform to numerous requirements, corresponding to ISO 9001:2000, ASME, A2LA, PED and others. It must move a evaluation of its high quality program as properly as on-site audits of the foundry’s processes and procedures such as welding, warmth remedy and non-destructive examination. Additional proof of efficiency is set by analysis of tryout castings to confirm specs are met.
Welding procedures — Welding is used through the manufacturing and upgrading of castings, similar to when radiographic examination is required. Welding requirements state that procedures and welder qualifications should meet ASME Section IX (or EN ISO 15614-1 and ISO 9606-1) qualification requirements. Similarly, every lot of weld filler should comply with ASME/AWS chemical evaluation specs. In Europe, compliance should be to EN499. Weld filler must have precise chemistry.
Marking inspection and testing — Valve body castings have markings (Figure 2) that identify the foundry that poured the casting and that indicate the heat code. Material identification can be usually proven on the physique casting, such as CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct both visible inspections and mechanical exams on pressure-retaining castings.
As-cast external and internal surfaces are inspected visually for unacceptable irregularities, together with sizzling tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing includes a hydrostatic stress take a look at to confirm the leak tightness of a control valve’s pressure-retaining elements, including the physique and bonnet castings. The test process entails a fixture that closes off cavities that may be pressurized in service after which subjects the element to the hydrostatic shell take a look at stress acceptable for the valve physique material and sophistication.
ASME B16.34 sets out the hydrostatic check pressure to make use of for metal and alloy valves. It’s calculated by multiplying the working pressure by 1.5 and rounding to the following greater 25 psig increment. Any visually detectable weeping or leaking through the strain boundary partitions which are part of the valve assembly is a compulsory cause for rejection (Figure 3).
Compliance with these specs have to be ensured, in addition to with other requirements relating to supplies.
Figure 2. Markings establish the foundry and materials of the valve physique. These control valve bodies have been solid at an Emerson-approved foundry in China.
Meeting materials requirements
Valve casting integrity and quality begins with specifications that decision not only for premium materials, but also for the materials that work greatest within the meant applications. เกจวัดแรงดันคือ and ductility as well as resistance to sure components, together with the makeup of the managed fluid, working temperature and circulate velocity.
For occasion, chemical composition should be controlled precisely to attain an alloy’s intended performance degree. Carbon metal castings for valves meant to be used in oil and gas applications must meet NACE SP0472 suggestions that chemical composition be controlled to less than zero.43% carbon equivalency. The lower carbon content improves weldability and reduces the potential for stress cracking by hydrogen sulfide typically present in oil and gas production and processing functions.
Another example of materials tied to a particular application embody those 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, whereas forgings must meet ASME SA 350 Grade LF2.
Many merchandise with international use now adjust to twin materials specifications to fulfill ASME and European requirements. For instance, metal castings are specified and licensed to each ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson often provides its personal stringent requirements such as the heat treating of high nickel alloys, extra demanding chemical composition or special welding procedures.
In the past, Emerson has supplemented typical ASTM and ASME specs to achieve the improved corrosion-resistance levels and high temperature capabilities offered by high-nickel alloys. This is now accomplished by the brand new ASTM specification A990, which addresses each materials composition and high 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 automatic rejection.
Qualifying a foundry
As part of a prospective foundry’s qualification, Emerson inspects and tests Fisher valve castings. Non-destructive testing radiography is used as a monitoring tool. ASTM A990 Class C requires radiography of the first casting of every pattern. The acceptance criterion is Level 3 for classes A, B and C. For classes D by way of G, no cracking, hot 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 prepared, they’ll pose major issues, together with poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification process could be adopted to keep away from these casting difficulties.
The foundry should solid a 1-inch thick high-nickel check plate (Figure 4) that meets ASTM Material Specification A990. It’s tough to solid because of the distinction in cross-section between the bottom of the weld cavity (in the center) and the general 1-inch thickness of the plate. The cavity of the poured plate is then filled with an identical composition weld materials. The welder and process for this step must meet the standards outlined in Section IX of the ASME Boiler and Pressure Vessel Code. Test bars (3/8-inch thick) are reduce from the plate and bent over a 1½-inch mandrel per ASTM A990 into a U-shape.
The bars are examined closely for cracking along the weld heat-affected zone, casting grain boundaries or dendrite boundaries. Failure to satisfy high quality standards will outcome in the disqualification of the foundry from further consideration. Casting patterns must be devoted solely to high-nickel alloy service. Use of carbon metal or a stainless-steel pattern is unacceptable as a end result of differences in solidification properties.
Shrinkage rates for gates, risers and other accessories can vary significantly. Once the dedicated pattern gear for every of those components has been secured, try-out castings are poured for every pattern-alloy combination. The castings are then radiographed.
The intent is to reveal any inherent casting defects — similar to shrinkage — that have to be eliminated by modifying the pattern rigging.
Figure four. In a foundry analysis, a casting is crammed with 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 bodies for greater than a decade. After an exploratory go to by procurement and manufacturing specialists, followed by an intensive qualification course of, 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 applied international standards and has obtained certifications for German TUV and CE, Norway DNV, German Lloyd’s and American ABS, and has passed worldwide high quality system certifications of ISO 9001 and QS -9000.
The foundry has been awarded Gold Medals three times consecutively in 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 specifications for casting valve our bodies.
Control valve customers may be involved after they study certain valve elements usually are not made in the U.S. or Europe, but elsewhere. Perhaps their concern stems from expertise with other inferior merchandise, such as appliances, clothes or electronics made in these nations and bought on-line. But if the valve components are being equipped to a serious control valve vendor that has gone to great lengths to qualify the foundry or supplier, then customers can be assured the valves meet all specifications.

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