Valve sourcing goes global

Across many types of merchandise in a wide range of industries, the follow of combining assorted components from numerous sources all over the world is the rule, not the exception. Should this be a priority for a control valve user? For example, when an finish consumer discovers that a number of parts are being made in China (Figure 1), ought to the user fear about the quality?
When dealing with a significant valve vendor, the reply is “no.” There shouldn’t be any room for doubt when the seller has a quantity of checks and balances in place focusing on product high quality to ensure management valves operate as designed, need minimal upkeep, perform safely and operate inside environmental rules.
Yet, regardless of such efforts by the seller, a control valve user may have questions about global sourcing and the country of origin. This article discusses how one main control valve vendor ensures product quality. Many different control valve distributors follow the identical or comparable procedures.
Quality specification brings international assurance
Emerson enforces a comprehensive quality specification for its Fisher control valves that should be met by suppliers of pressure-containing and structural steel 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 undergo a rigorous qualification process. The process completely investigates a potential supplier’s ability to meet material specifications and relevant international codes and requirements — in addition to specific necessities related to element manufacture. In the case of castings, a foundry is taken into account “qualified” when it passes a crucial evaluation by Fisher’s engineers.
The foundry must reveal a report of qualification by a third-party inspection company and conform to varied standards, similar to ISO 9001:2000, ASME, A2LA, PED and others. It should move a evaluate of its quality program as properly as on-site audits of the foundry’s processes and procedures similar to welding, heat therapy 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 in the course of the manufacturing 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, each lot of weld filler should adjust to ASME/AWS chemical analysis specifications. In Europe, compliance should be to EN499. Weld filler must have precise 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 warmth code. Material identification can additionally be sometimes shown on the physique casting, such as CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct each visible inspections and mechanical exams on pressure-retaining castings.
As-cast external and inner surfaces are inspected visually for unacceptable irregularities, including sizzling tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing involves a hydrostatic strain take a look at to confirm the leak tightness of a control valve’s pressure-retaining parts, including the body and bonnet castings. The test process includes a fixture that closes off cavities that might be pressurized in service after which subjects the part to the hydrostatic shell check pressure appropriate for the valve physique material and class.
ASME B16.34 sets out the hydrostatic test pressure to use for steel and alloy valves. It’s calculated by multiplying the working strain by 1.5 and rounding to the next greater 25 psig increment. Any visually detectable weeping or leaking through the strain boundary walls that are a half of the valve assembly is a mandatory cause for rejection (Figure 3).
Compliance with these specs should be ensured, in addition to with other necessities concerning materials.
Figure 2. Markings determine the foundry and supplies of the valve body. These management valve our bodies had been solid at an Emerson-approved foundry in China.
Meeting material requirements
Valve casting integrity and quality begins with specs that call not just for premium supplies, but also for the supplies that work finest within the meant applications. These utility necessities embrace power and ductility in addition to resistance to certain elements, together with the makeup of the controlled fluid, working temperature and move velocity.
For instance, chemical composition should be managed precisely to realize an alloy’s meant efficiency stage. Carbon metal castings for valves supposed to be used in oil and gasoline applications should meet NACE SP0472 recommendations that chemical composition be controlled to lower than zero.43% carbon equivalency. The decrease carbon content material improves weldability and reduces the potential for stress cracking by hydrogen sulfide typically found in oil and gas production and processing purposes.
Another instance of materials tied to a particular application embody those for upstream oil and fuel manufacturing. Many of those applications occur within the arctic areas of Russia and Canada. For this service, castings are ASME SA 352 Grade LCC, while forgings should meet ASME SA 350 Grade LF2.
Many merchandise with international use now comply with twin material specifications to meet ASME and European requirements. For instance, metal castings are specified and certified to each ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson usually adds its personal stringent necessities similar to the heat treating of high nickel alloys, more demanding chemical composition or special welding procedures.
In the past, Emerson has supplemented standard ASTM and ASME specs to realize the enhanced corrosion-resistance ranges and excessive temperature capabilities supplied by high-nickel alloys. This is now accomplished by the new ASTM specification A990, which addresses each material 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 by way of a casting means automatic rejection.
Qualifying a foundry
As part of a potential foundry’s qualification, Emerson inspects and tests Fisher valve castings. Non-destructive testing radiography is used as a monitoring software. ASTM A990 Class C requires radiography of the first casting of each sample. The acceptance criterion is Level 3 for categories A, B and C. For classes D by way of G, no cracking, scorching tears or inserts are allowed as specified in ASTM A990.
High-nickel alloy castings provide improved efficiency in corrosive services and elevated temperatures. However, if high-nickel castings are improperly ready, they can pose main problems, including poor integrity, poor weldability and lower-than-expected corrosion resistance. เกจแรงดันลม of may be followed to keep away from these casting difficulties.
The foundry should forged 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 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 procedure 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 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 meet quality standards will result within the disqualification of the foundry from further consideration. Casting patterns should be devoted solely to high-nickel alloy service. Use of carbon steel or a stainless-steel pattern is unacceptable as a result of variations in solidification properties.
Shrinkage charges for gates, risers and different accessories can range considerably. Once the devoted pattern gear for each of those parts has been secured, try-out castings are poured for each pattern-alloy mixture. 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 4. 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 go to by procurement and manufacturing specialists, adopted by an extensive qualification process, the foundry was accredited and has been delivering high-quality valve physique and bonnet castings to Fisher valve manufacturing websites.
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 passed international quality system certifications of ISO 9001 and QS -9000.
The foundry has been awarded Gold Medals 3 times 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 specifications for casting valve bodies.
Summary
Control valve customers could be concerned once they learn certain valve parts usually are not made in the united states or Europe, but elsewhere. Perhaps their concern stems from experience with different inferior merchandise, similar to home equipment, clothes or electronics made in these countries and sold on-line. But if the valve components are being provided to a major control valve vendor that has gone to great lengths to qualify the foundry or provider, then users may be assured the valves meet all specifications.
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