Valve sourcing goes international

Across many forms of merchandise in a wide range of industries, the apply of mixing assorted components from numerous assets around the world is the rule, not the exception. Should this be a concern for a control valve user? For example, when an end person discovers that several elements are being made in China (Figure 1), should the consumer fear concerning the quality?
When coping with a serious valve vendor, the reply is “no.” There shouldn’t be any room for doubt when the seller has a number of checks and balances in place specializing in product high quality to make sure control valves operate as designed, want minimal maintenance, carry out safely and operate within environmental laws.
Yet, despite such efforts by the vendor, a control valve person might have questions on global sourcing and the nation of origin. This article discusses how one major management valve vendor ensures product high quality. Many other control valve distributors observe the identical or comparable procedures.
Quality specification brings global assurance
Emerson enforces a complete quality specification for its Fisher control valves that must be met by suppliers of pressure-containing and structural steel castings. The high quality specification contains greater than a dozen requirements 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 endure a rigorous qualification process. The process thoroughly investigates a potential supplier’s capacity to satisfy material specs and applicable worldwide codes and requirements — in addition to particular necessities related 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 must reveal a document of qualification by a third-party inspection company and conform to varied requirements, corresponding to ISO 9001:2000, ASME, A2LA, PED and others. It should pass a evaluation of its high quality program as well as on-site audits of the foundry’s processes and procedures such as welding, heat treatment 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 production 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 standards. Similarly, each lot of weld filler must comply with ASME/AWS chemical evaluation specs. In Europe, compliance have to be to EN499. Weld filler should have precise chemistry.
Marking inspection and testing — Valve physique castings have markings (Figure 2) that identify the foundry that poured the casting and that indicate the warmth code. Material identification is also sometimes shown on the physique casting, corresponding to CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct each visual inspections and mechanical exams 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 pressure take a look at to verify the leak tightness of a control valve’s pressure-retaining parts, together with the body and bonnet castings. The take a look at process includes a fixture that closes off cavities that may be pressurized in service and then subjects the element to the hydrostatic shell take a look at strain acceptable for the valve body materials and sophistication.
ASME B16.34 sets out the hydrostatic test strain to use for metal and alloy valves. It’s calculated by multiplying the working pressure by 1.5 and rounding to the next higher 25 psig increment. Any visually detectable weeping or leaking via the strain boundary partitions which might be a half of the valve meeting is a compulsory trigger for rejection (Figure 3).
Compliance with these specs should be ensured, as nicely as with other necessities concerning materials.
Figure 2. Markings determine the foundry and materials of the valve body. These control valve our bodies had been solid at an Emerson-approved foundry in China.
Meeting materials requirements
Valve casting integrity and high quality begins with specifications that decision not just for premium materials, but in addition for the materials that work greatest in the supposed applications. These application necessities embody power and ductility as nicely as resistance to sure components, together with the make-up of the controlled fluid, working temperature and circulate velocity.
For occasion, chemical composition should be managed precisely to achieve an alloy’s supposed efficiency degree. Carbon metal castings for valves supposed for use in oil and gas purposes must meet NACE SP0472 recommendations that chemical composition be controlled to lower than zero.43% carbon equivalency. The lower carbon content improves weldability and reduces the potential for stress cracking by hydrogen sulfide usually found in oil and gas production and processing functions.
Another instance of materials tied to a particular application embrace those for upstream oil and gas production. Many of those purposes happen within the arctic regions of Russia and Canada. For this service, castings are ASME SA 352 Grade LCC, while forgings should meet ASME SA 350 Grade LF2.
ร้านซ่อมเครื่องวัดความดัน with world use now comply with dual material specifications to satisfy ASME and European standards. For instance, steel castings are specified and licensed to each ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson often adds its personal stringent requirements such as the warmth treating of excessive nickel alloys, more demanding chemical composition or special welding procedures.
In the previous, Emerson has supplemented conventional ASTM and ASME specs to attain the enhanced corrosion-resistance levels and excessive temperature capabilities provided by high-nickel alloys. This is now accomplished by the brand new ASTM specification A990, which addresses each materials composition and quality.
Figure 3. Pressure-retaining components of a valve are subjected to hydrostatic testing to evaluate the parts’ integrity. Visible leakage or seepage through a casting means computerized rejection.
Qualifying a foundry
As part of a prospective foundry’s qualification, Emerson inspects and tests Fisher valve castings. pressure gauge -destructive testing radiography is used as a monitoring device. ASTM A990 Class C requires radiography of the primary casting of every sample. The acceptance criterion is Level three for categories A, B and C. For classes D via G, no cracking, hot tears or inserts are allowed as specified 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 main problems, 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 must forged a 1-inch thick high-nickel test plate (Figure 4) that meets ASTM Material Specification A990. It’s tough to solid due to the distinction 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 materials. 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 reduce from the plate and bent over a 1½-inch mandrel per ASTM A990 into a U-shape.
The bars are examined carefully for cracking along the weld heat-affected zone, casting grain boundaries or dendrite boundaries. Failure to satisfy high quality requirements will end result in the disqualification of the foundry from additional consideration. Casting patterns must be devoted solely to high-nickel alloy service. Use of carbon metal or a stainless-steel sample is unacceptable as a result of variations in solidification properties.
Shrinkage charges for gates, risers and different equipment can differ significantly. Once the dedicated sample equipment for every of these components has been secured, try-out castings are poured for every pattern-alloy mixture. The castings are then radiographed.
The intent is to disclose any inherent casting defects — such as shrinkage — that have to be eliminated by modifying the pattern rigging.
Figure four. 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 cast Fisher valve our bodies for more than a decade. After an exploratory visit by procurement and manufacturing specialists, followed by an extensive qualification process, the foundry was permitted and has been delivering high-quality valve body and bonnet castings to Fisher valve manufacturing websites.
To assist ensure the quality of the castings it produces, the Chinese foundry has implemented worldwide requirements 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 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 our bodies.
Control valve customers may be involved when they study sure valve parts are not made in the united states or Europe, but elsewhere. Perhaps their concern stems from experience with different inferior merchandise, similar to appliances, garments or electronics made in those international locations and offered on-line. But if the valve elements are being supplied to a significant control valve vendor that has gone to great lengths to qualify the foundry or provider, then customers could be assured the valves meet all specs.

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