Valve sourcing goes global

Across many types of products in a selection of industries, the practice of combining assorted elements from various assets around the world is the rule, not the exception. Should this be a concern for a control valve user? For instance, when an finish consumer discovers that a number of elements are being made in China (Figure 1), should the user worry about the quality?
When dealing with a serious valve vendor, the answer is “no.” There shouldn’t be any room for doubt when the vendor has multiple checks and balances in place specializing in product high quality to ensure management valves operate as designed, want minimal maintenance, perform safely and operate within environmental rules.
Yet, despite such efforts by the vendor, a control valve person might have questions on international sourcing and the country of origin. This article discusses how one major control valve vendor ensures product quality. Many other control valve vendors comply with the identical or similar procedures.
Quality specification brings global assurance
Emerson enforces a complete quality specification for its Fisher management valves that have to be met by suppliers of pressure-containing and structural steel castings. The quality specification consists of more than a dozen requirements that apply to the next areas:
Supplier qualification
Welding procedures
Marking inspection and testing
Tryout and sample castings
Production castings
Certification of compliance
Supplier qualification — Suppliers endure a rigorous qualification course of. The process thoroughly investigates a potential supplier’s ability to fulfill materials specs and applicable worldwide codes and standards — in addition to particular requirements associated to element manufacture. In the case of castings, a foundry is considered “qualified” when it passes a critical evaluation by Fisher’s engineers.
The foundry must reveal a record of qualification by a third-party inspection company and conform to varied standards, corresponding to ISO 9001:2000, ASME, A2LA, PED and others. It should move a evaluate of its quality program as nicely as on-site audits of the foundry’s processes and procedures similar to welding, heat remedy and non-destructive examination. Additional proof of efficiency is decided by analysis of tryout castings to verify specs are met.
Welding procedures — Welding is used in the course of the production and upgrading of castings, corresponding to when radiographic examination is required. Welding necessities 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 should adjust to ASME/AWS chemical analysis specs. In Europe, compliance must be to EN499. Weld filler should have actual chemistry.
Marking inspection and testing — Valve physique castings have markings (Figure 2) that establish the foundry that poured the casting and that point out the heat code. Material identification can also be typically proven on the body casting, corresponding to CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct both visible inspections and mechanical checks 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 entails a hydrostatic strain test to confirm the leak tightness of a management valve’s pressure-retaining components, including the physique and bonnet castings. The test process involves a fixture that closes off cavities that might be pressurized in service and then topics the component to the hydrostatic shell test pressure acceptable for the valve body material and sophistication.
ASME B16.34 sets out the hydrostatic check pressure to use for steel and alloy valves. It’s calculated by multiplying the working strain by 1.5 and rounding to the next higher 25 psig increment. Any visually detectable weeping or leaking through the strain boundary partitions which may be part of the valve assembly is a compulsory trigger for rejection (Figure 3).
Compliance with these specifications have to be ensured, in addition to with other requirements regarding materials.
Figure 2. Markings determine the foundry and supplies of the valve body. These control valve bodies were solid at an Emerson-approved foundry in China.
Meeting materials necessities
Valve casting integrity and quality begins with specifications that call not only for premium materials, but in addition for the materials that work greatest within the meant purposes. These utility requirements embody strength and ductility in addition to resistance to sure components, together with the make-up of the controlled fluid, working temperature and move velocity.
For occasion, chemical composition should be managed precisely to achieve an alloy’s intended efficiency stage. Carbon metal castings for valves intended to be used in oil and gasoline purposes should meet NACE SP0472 recommendations that chemical composition be controlled to lower than 0.43% carbon equivalency. เกจวัดแรงดันแก๊ส improves weldability and reduces the potential for stress cracking by hydrogen sulfide sometimes present in oil and fuel production and processing purposes.
Another instance of supplies tied to a specific utility embrace those for upstream oil and gasoline production. Many of those purposes happen within 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 world use now adjust to twin materials specifications to satisfy ASME and European requirements. For instance, steel castings are specified and certified to each ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson usually provides its own stringent requirements corresponding to the heat treating of excessive nickel alloys, more demanding chemical composition or particular welding procedures.
In the past, Emerson has supplemented standard ASTM and ASME specs to attain the enhanced corrosion-resistance levels and excessive temperature capabilities offered by high-nickel alloys. This is now accomplished by the new ASTM specification A990, which addresses both material composition and high quality.
Figure 3. Pressure-retaining elements of a valve are subjected to hydrostatic testing to evaluate the parts’ integrity. Visible leakage or seepage via a casting means automated rejection.
Qualifying a foundry
As part of a potential foundry’s qualification, Emerson inspects and checks Fisher valve castings. Non-destructive testing radiography is used as a monitoring device. ASTM A990 Class C requires radiography of the primary casting of each pattern. The acceptance criterion is Level 3 for classes A, B and C. For categories D through G, no cracking, hot tears or inserts are allowed as specified in ASTM A990.
High-nickel alloy castings provide improved performance in corrosive providers and elevated temperatures. However, if high-nickel castings are improperly ready, they can pose major issues, including poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification process could be adopted to avoid these casting difficulties.
The foundry should cast a 1-inch thick high-nickel test plate (Figure 4) that meets ASTM Material Specification A990. It’s difficult to cast because of the difference in cross-section between the bottom of the weld cavity (in the center) and the overall 1-inch thickness of the plate. The cavity of the poured plate is then filled with a matching 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 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 meet quality standards will result within the disqualification of the foundry from further consideration. Casting patterns have to be dedicated solely to high-nickel alloy service. Use of carbon steel or a stainless-steel pattern is unacceptable due to variations in solidification properties.
Shrinkage charges for gates, risers and other accessories can differ significantly. Once the devoted pattern equipment for every 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 — similar to shrinkage — that must be eradicated by modifying the pattern rigging.
Figure 4. In a foundry evaluation, a casting is filled with weld filler, then sliced to yield a bar for bend testing.
A qualified foundry
Emerson has used a Chinese foundry (Figure 5) to solid Fisher valve our bodies for greater than a decade. After an exploratory go to by procurement and manufacturing specialists, adopted 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 websites.
To assist ensure the standard 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 passed international high quality system certifications of ISO 9001 and QS -9000.
The foundry has been awarded Gold Medals thrice consecutively within the Beijing International Casting, Forging and Industrial Boiler Expo. It has twice received an Excellent Supplier award from Emerson.
Figure 5. This Chinese foundry meets all specs for casting valve bodies.
Summary
Control valve users could be involved when they be taught certain valve elements aren’t made in the us or Europe, however elsewhere. Perhaps their concern stems from experience with different inferior products, corresponding to home equipment, garments or electronics made in these countries and bought on-line. But if the valve components are being supplied to a major control valve vendor that has gone to nice lengths to qualify the foundry or provider, then users could be assured the valves meet all specs.
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