Valve sourcing goes international

Across many forms of merchandise in a wide selection of industries, the practice of combining assorted elements from various resources around the world is the rule, not the exception. Should this be a concern for a control valve user? For example, when an end user discovers that a number of components are being made in China (Figure 1), should the consumer worry concerning the quality?

When coping with a serious valve vendor, the answer is “no.” There shouldn’t be any room for doubt when the vendor has a number of checks and balances in place focusing on product quality to ensure control valves function as designed, need minimal maintenance, carry out safely and operate within environmental rules.
Yet, regardless of such efforts by the vendor, a control valve person may have questions about international sourcing and the nation of origin. This article discusses how one major control valve vendor ensures product high quality. Many different control valve vendors comply with the same or related procedures.
Quality specification brings international assurance

Emerson enforces a complete high quality specification for its Fisher management valves that must be met by suppliers of pressure-containing and structural metallic castings. The quality specification consists of greater 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 capability to satisfy materials specs and applicable worldwide codes and standards — in addition to particular necessities associated to part manufacture. In the case of castings, a foundry is taken into account “qualified” when it passes a critical analysis by Fisher’s engineers.
The foundry must demonstrate a record of qualification by a third-party inspection company and conform to numerous standards, such as ISO 9001:2000, ASME, A2LA, PED and others. It must pass a evaluate of its quality program in addition to on-site audits of the foundry’s processes and procedures corresponding to welding, warmth remedy and non-destructive examination. Additional proof of efficiency is determined by analysis of tryout castings to confirm specs are met.
Welding procedures — Welding is used during the production and upgrading of castings, corresponding 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 standards. Similarly, every lot of weld filler should adjust to ASME/AWS chemical analysis specifications. In Europe, compliance have to 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 point out the heat code. Material identification is also usually shown on the physique casting, similar to CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct both visible inspections and mechanical tests on pressure-retaining castings.
As-cast exterior and internal surfaces are inspected visually for unacceptable irregularities, including hot tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing includes a hydrostatic pressure take a look at to substantiate the leak tightness of a management valve’s pressure-retaining components, including the body and bonnet castings. The check process involves a fixture that closes off cavities that may be pressurized in service after which subjects the part to the hydrostatic shell check stress applicable for the valve body materials and sophistication.
ASME B16.34 sets out the hydrostatic take a look at pressure to make use of for metal and alloy valves. It’s calculated by multiplying the working stress by 1.5 and rounding to the subsequent larger 25 psig increment. Any visually detectable weeping or leaking through the stress boundary walls which are a part of the valve assembly is a mandatory cause for rejection (Figure 3).
Compliance with these specs should be ensured, in addition to with other requirements concerning supplies.
Figure 2. Markings identify the foundry and supplies of the valve body. These control valve our bodies have been solid at an Emerson-approved foundry in China.
Meeting material necessities

Valve casting integrity and quality begins with specs that call not only for premium supplies, but also for the supplies that work greatest within the meant functions. ไดอะแฟรม include energy and ductility as nicely as resistance to certain factors, together with the makeup of the managed fluid, operating temperature and circulate velocity.
For occasion, chemical composition must be managed exactly to realize an alloy’s supposed efficiency stage. Carbon metal castings for valves meant for use in oil and gas functions should meet NACE SP0472 recommendations that chemical composition be managed to lower than 0.43% carbon equivalency. The lower carbon content material improves weldability and reduces the potential for stress cracking by hydrogen sulfide usually present in oil and fuel manufacturing and processing applications.
Another instance of supplies tied to a specific utility include these for upstream oil and gasoline production. Many of those applications happen 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 products with world use now comply with dual materials specifications to meet ASME and European standards. For instance, steel castings are specified and certified to both ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson typically provides its personal stringent necessities similar to the warmth treating of high nickel alloys, more demanding chemical composition or special welding procedures.
In the previous, Emerson has supplemented standard ASTM and ASME specs to achieve 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 both materials composition and quality.
Figure three. Pressure-retaining elements of a valve are subjected to hydrostatic testing to evaluate 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 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 every pattern. The acceptance criterion is Level 3 for classes A, B and C. For classes D through G, no cracking, hot tears or inserts are allowed as laid out in ASTM A990.
High-nickel alloy castings present improved performance in corrosive companies and elevated temperatures. However, if high-nickel castings are improperly ready, they’ll pose major issues, together with poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification course of can be followed to keep away from 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 tough to forged due to the distinction 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 an identical composition weld materials. The welder and process for this step must meet the requirements 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 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 meet high quality requirements will end result in the disqualification of the foundry from further consideration. Casting patterns should be dedicated solely to high-nickel alloy service. Use of carbon metal or a stainless-steel sample is unacceptable due to differences in solidification properties.
Shrinkage charges for gates, risers and different equipment can differ significantly. Once the devoted pattern equipment for every of these components has been secured, try-out castings are poured for each pattern-alloy combination. The castings are then radiographed.
เพรสเชอร์เกจ is to reveal any inherent casting defects — corresponding to shrinkage — that have to be eradicated by modifying the pattern rigging.
Figure 4. In a foundry analysis, a casting is filled with weld filler, then sliced to yield a bar for bend testing.
A certified foundry

Emerson has used a Chinese foundry (Figure 5) to forged Fisher valve our bodies for greater than a decade. After an exploratory go to by procurement and manufacturing specialists, followed by an in depth qualification course of, the foundry was accredited and has been delivering high-quality valve body and bonnet castings to Fisher valve manufacturing sites.
To help guarantee the quality of the castings it produces, the Chinese foundry has implemented international standards and has obtained certifications for German TUV and CE, Norway DNV, German Lloyd’s and American ABS, and has passed international quality system certifications of ISO 9001 and QS -9000.
The foundry has been awarded Gold Medals thrice consecutively in the Beijing International Casting, Forging and Industrial Boiler Expo. It has twice acquired an Excellent Supplier award from Emerson.
Figure 5. This Chinese foundry meets all specs for casting valve bodies.

Control valve users can be concerned after they study certain valve elements aren’t made in the U.S. or Europe, however elsewhere. Perhaps their concern stems from expertise with other inferior merchandise, similar to home equipment, clothes or electronics made in these international locations and sold online. But if the valve parts are being provided to a serious management valve vendor that has gone to nice lengths to qualify the foundry or provider, then users can be assured the valves meet all specifications.

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