Valve sourcing goes global

Across many types of products in a selection of industries, the practice of mixing 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 end user discovers that a number of parts are being made in China (Figure 1), ought to the consumer fear about the quality?
When coping with a major valve vendor, the reply is “no.” There shouldn’t be any room for doubt when the vendor has multiple checks and balances in place specializing in product quality to make sure control valves function as designed, need minimal upkeep, carry out safely and operate inside environmental regulations.
Yet, despite such efforts by the seller, a management valve user may have questions about world sourcing and the nation of origin. This article discusses how one main management valve vendor ensures product high quality. Many other control valve distributors comply with the same or comparable 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 metal castings. The quality specification consists of greater than a dozen necessities 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 course of. The process completely investigates a possible supplier’s ability to meet materials specs and applicable worldwide codes and standards — as properly as particular necessities associated to component manufacture. In the case of castings, a foundry is considered “qualified” when it passes a critical analysis by Fisher’s engineers.
The foundry must reveal a report of qualification by a third-party inspection agency and conform to numerous standards, such as ISO 9001:2000, ASME, A2LA, PED and others. It should cross a evaluate of its quality program in addition to on-site audits of the foundry’s processes and procedures such as welding, heat treatment and non-destructive examination. Additional proof of performance is decided by analysis of tryout castings to confirm specifications are met.
Welding procedures — Welding is used through the manufacturing 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 requirements. Similarly, each lot of weld filler should adjust to ASME/AWS chemical evaluation specifications. In Europe, compliance must be to EN499. Weld filler will need to have actual chemistry.
Marking inspection and testing — Valve physique castings have markings (Figure 2) that determine the foundry that poured the casting and that point out the heat code. Material identification can also be sometimes proven on the physique casting, corresponding to CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct both visual inspections and mechanical tests on pressure-retaining castings.
As-cast external and inside surfaces are inspected visually for unacceptable irregularities, including sizzling tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing involves a hydrostatic stress check to substantiate the leak tightness of a management valve’s pressure-retaining parts, including the body and bonnet castings. The test process involves a fixture that closes off cavities that might be pressurized in service after which subjects the component to the hydrostatic shell test strain appropriate for the valve body materials and class.
ASME B16.34 units out the hydrostatic check stress to use for steel and alloy valves. It’s calculated by multiplying the working strain by 1.5 and rounding to the subsequent larger 25 psig increment. Any visually detectable weeping or leaking via the strain boundary partitions that are a half of the valve assembly is a compulsory trigger for rejection (Figure 3).
Compliance with these specs must be ensured, in addition to with other necessities regarding materials.
Figure 2. Markings determine the foundry and supplies of the valve physique. These control valve bodies have been solid at an Emerson-approved foundry in China.
Meeting materials requirements
Valve casting integrity and high quality begins with specs that decision not only for premium supplies, but also for the supplies that work best within the meant applications. These utility requirements embody energy and ductility as well as resistance to sure elements, including the makeup of the managed fluid, working temperature and move velocity.
For occasion, chemical composition have to be controlled precisely to realize an alloy’s supposed efficiency level. Carbon metal castings for valves supposed to be used in oil and fuel purposes must meet NACE SP0472 recommendations that chemical composition be controlled to lower than 0.43% carbon equivalency. The lower carbon content material improves weldability and reduces the potential for stress cracking by hydrogen sulfide sometimes found in oil and gasoline production and processing functions.
Another instance of supplies tied to a selected application embrace these for upstream oil and fuel production. Many of these purposes occur in the arctic regions of Russia and Canada. For this service, castings are ASME SA 352 Grade LCC, whereas forgings must meet ASME SA 350 Grade LF2.
Many merchandise with world use now adjust to twin material specs to meet ASME and European requirements. For example, steel castings are specified and authorized to each ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson often provides its own stringent necessities corresponding to the warmth treating of excessive nickel alloys, extra demanding chemical composition or special welding procedures.
In the past, Emerson has supplemented typical ASTM and ASME specs to achieve the improved corrosion-resistance levels and high temperature capabilities offered by high-nickel alloys. This is now completed by the model new ASTM specification A990, which addresses both material composition and quality.
Figure three. Pressure-retaining parts of a valve are subjected to hydrostatic testing to judge the parts’ integrity. Visible leakage or seepage by way of a casting means computerized rejection.
Qualifying a foundry
As a half of a prospective 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 pattern. The acceptance criterion is Level three for categories A, B and C. For classes D by way of G, no cracking, scorching tears or inserts are allowed as laid out in ASTM A990.
High-nickel alloy castings provide improved performance in corrosive services and elevated temperatures. However, if high-nickel castings are improperly prepared, they will pose major problems, together with poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification process may be adopted to avoid these casting difficulties.
เครื่องมือวัดความดันคือ must solid a 1-inch thick high-nickel take a look at plate (Figure 4) that meets ASTM Material Specification A990. It’s difficult to forged because of 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 crammed 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 fulfill high quality standards will end result within the disqualification of the foundry from further consideration. Casting patterns have to be devoted solely to high-nickel alloy service. Use of carbon steel or a stainless-steel pattern is unacceptable because of differences in solidification properties.
Shrinkage rates for gates, risers and different accessories can differ considerably. Once the dedicated pattern gear for each of those components has been secured, try-out castings are poured for each pattern-alloy combination. The castings are then radiographed.
The intent is to disclose any inherent casting defects — such as shrinkage — that have to be eradicated by modifying the sample rigging.
Figure 4. In a foundry analysis, a casting is crammed with weld filler, then sliced to yield a bar for bend testing.
A qualified foundry
Emerson has used a Chinese foundry (Figure 5) to forged Fisher valve our bodies for greater than a decade. After an exploratory visit by procurement and manufacturing specialists, adopted by an extensive qualification process, the foundry was permitted 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 carried out worldwide requirements and has obtained certifications for German TUV and CE, Norway DNV, German Lloyd’s and American ABS, and has passed worldwide 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.
Summary
Control valve users may be concerned after they study certain valve parts usually are not made in the U.S. or Europe, but elsewhere. Perhaps their concern stems from experience with other inferior merchandise, such as home equipment, clothes or electronics made in these nations and bought on-line. But if the valve parts are being supplied to a significant management valve vendor that has gone to great lengths to qualify the foundry or supplier, then users may be assured the valves meet all specs.
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