Valve sourcing goes global

Across many forms of products in quite a lot of industries, the apply of combining assorted elements from numerous resources around the globe is the rule, not the exception. Should this be a concern for a management valve user? For example, when an end user discovers that several components are being made in China (Figure 1), ought to the user worry about the quality?
When dealing with a major 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 make sure management valves function as designed, need minimal maintenance, carry out safely and function within environmental regulations.
Yet, regardless of such efforts by the seller, a control valve person could have questions on global sourcing and the country of origin. This article discusses how one major control valve vendor ensures product quality. Many other control valve distributors follow the same or related procedures.
Quality specification brings global assurance
Emerson enforces a complete quality specification for its Fisher control valves that have to be met by suppliers of pressure-containing and structural metallic castings. The high quality specification contains 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 undergo a rigorous qualification course of. The process totally investigates a possible supplier’s capability to fulfill material specs and relevant worldwide codes and standards — in addition to particular requirements associated to component manufacture. In the case of castings, a foundry is taken into account “qualified” when it passes a important evaluation by Fisher’s engineers.
The foundry must show a report 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 pass a review of its quality program in addition to on-site audits of the foundry’s processes and procedures such as welding, warmth remedy and non-destructive examination. Additional proof of performance is set by evaluation 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 evaluation specifications. In Europe, compliance have to be to EN499. Weld filler must have actual chemistry.
Marking inspection and testing — Valve body castings have markings (Figure 2) that establish the foundry that poured the casting and that indicate the warmth code. Material identification can be typically proven on the body casting, corresponding to CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct each visual inspections and mechanical checks on pressure-retaining castings.
As-cast exterior and internal surfaces are inspected visually for unacceptable irregularities, including scorching tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing entails a hydrostatic strain take a look at to substantiate the leak tightness of a control valve’s pressure-retaining elements, together with the body and bonnet castings. The test process includes a fixture that closes off cavities that may be pressurized in service after which subjects the part to the hydrostatic shell take a look at pressure applicable for the valve body material and class.
ASME B16.34 sets out the hydrostatic test stress to use for metal and alloy valves. It’s calculated by multiplying the working strain by 1.5 and rounding to the following higher 25 psig increment. Any visually detectable weeping or leaking through the strain boundary partitions which would possibly be part of the valve meeting is a compulsory cause for rejection (Figure 3).
Compliance with these specifications should be ensured, in addition to with other necessities regarding supplies.
Figure 2. Markings identify the foundry and materials of the valve body. เกจวัดแรงดันเชื้อเพลิง had been solid at an Emerson-approved foundry in China.
Meeting materials necessities
Valve casting integrity and quality begins with specs that call not only for premium materials, but also for the supplies that work best in the meant applications. These application requirements embody power and ductility in addition to resistance to sure factors, together with the makeup of the managed fluid, operating temperature and move velocity.
For instance, chemical composition should be managed precisely to achieve an alloy’s intended performance level. Carbon metal castings for valves supposed to be used in oil and fuel applications should meet NACE SP0472 suggestions that chemical composition be managed to lower than 0.43% carbon equivalency. The lower carbon content improves weldability and reduces the potential for stress cracking by hydrogen sulfide usually found in oil and fuel production and processing functions.
Another instance of supplies tied to a selected application embrace these for upstream oil and fuel production. Many of these functions occur 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 international use now adjust to twin material specs to satisfy ASME and European standards. For example, steel castings are specified and certified to both ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson usually provides its own stringent necessities such as the warmth treating of excessive nickel alloys, extra demanding chemical composition or particular welding procedures.
In the previous, Emerson has supplemented conventional ASTM and ASME specifications to attain the improved corrosion-resistance levels and excessive temperature capabilities supplied by high-nickel alloys. This is now completed 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 gauge 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 software. ASTM A990 Class C requires radiography of the primary casting of each sample. The acceptance criterion is Level 3 for categories A, B and C. For categories D through 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 prepared, they will pose major problems, including poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification process can be followed to keep away from these casting difficulties.
The foundry should forged a 1-inch thick high-nickel take a look at plate (Figure 4) that meets ASTM Material Specification A990. It’s difficult to solid due to 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 crammed with an identical composition weld material. 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 right 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 standards will result within 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 because of differences in solidification properties.
Shrinkage rates for gates, risers and different accessories can range considerably. Once the devoted sample tools for each of those 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 — corresponding to shrinkage — that need to be eliminated 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 certified foundry
Emerson has used a Chinese foundry (Figure 5) to cast Fisher valve bodies for more than a decade. After an exploratory go to by procurement and manufacturing specialists, followed by an in depth qualification process, the foundry was approved and has been delivering high-quality valve physique and bonnet castings to Fisher valve manufacturing sites.
To help guarantee the standard of the castings it produces, the Chinese foundry has applied worldwide requirements and has obtained certifications for German TUV and CE, Norway DNV, German Lloyd’s and American ABS, and has handed 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 received 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 once they learn certain valve components aren’t made in the us or Europe, however elsewhere. Perhaps their concern stems from expertise with other inferior merchandise, corresponding to appliances, clothes or electronics made in those nations and bought on-line. But if the valve parts are being supplied to a serious control valve vendor that has gone to nice lengths to qualify the foundry or provider, then customers can be assured the valves meet all specifications.

Scroll to Top