Across many forms of products in quite lots of industries, the apply of mixing assorted elements from varied assets all over the world is the rule, not the exception. Should this be a concern for a control valve user? For instance, when an finish user discovers that several components are being made in China (Figure 1), ought to the user worry concerning the quality?
When coping with a major valve vendor, the answer is “no.” There shouldn’t be any room for doubt when the seller has a number of checks and balances in place focusing on product high quality to make sure control valves operate as designed, need minimal upkeep, perform safely and function inside environmental rules.
Yet, regardless of such efforts by the seller, a management valve user may have questions on global sourcing and the nation of origin. This article discusses how one major control valve vendor ensures product high quality. Many other control valve distributors follow the same or comparable procedures.
Quality specification brings international assurance
Emerson enforces a complete quality specification for its Fisher control valves that must be met by suppliers of pressure-containing and structural metallic castings. The high quality specification includes more than a dozen necessities 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 bear a rigorous qualification process. The course of totally investigates a potential supplier’s capacity to meet material specs and applicable international codes and standards — as nicely as specific requirements associated to part manufacture. In the case of castings, a foundry is considered “qualified” when it passes a critical analysis by Fisher’s engineers.
The foundry should show a record of qualification by a third-party inspection agency and conform to varied requirements, similar to ISO 9001:2000, ASME, A2LA, PED and others. It must cross a evaluate of its high quality program in addition to on-site audits of the foundry’s processes and procedures similar to welding, heat remedy and non-destructive examination. Additional proof of performance 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, every lot of weld filler must adjust to ASME/AWS chemical evaluation specifications. In Europe, compliance should 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 indicate the heat code. Material identification is also sometimes proven on the physique casting, corresponding to CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct both visual inspections and mechanical exams 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 includes a hydrostatic stress check to substantiate the leak tightness of a management valve’s pressure-retaining components, together with the body and bonnet castings. The take a look at procedure involves a fixture that closes off cavities that may be pressurized in service after which topics the element to the hydrostatic shell take a look at pressure acceptable for the valve body material and sophistication.
ASME B16.34 units out the hydrostatic check strain to use for metal and alloy valves. It’s calculated by multiplying the working stress by 1.5 and rounding to the next higher 25 psig increment. Any visually detectable weeping or leaking through the stress boundary partitions that are part of the valve assembly is a mandatory trigger for rejection (Figure 3).
Compliance with these specs should be ensured, as nicely as with other requirements relating to materials.
Figure 2. Markings determine the foundry and materials of the valve physique. These management valve our bodies were solid at an Emerson-approved foundry in China.
Meeting materials necessities
Valve casting integrity and quality begins with specs that call not just for premium supplies, but in addition for the materials that work finest within the meant purposes. These application necessities embody energy and ductility in addition to resistance to certain factors, together with the makeup of the managed fluid, working temperature and move velocity.
For occasion, chemical composition should be controlled exactly to attain an alloy’s intended efficiency degree. Carbon metal castings for valves intended for use in oil and fuel purposes should meet NACE SP0472 recommendations that chemical composition be managed to less than 0.43% carbon equivalency. The decrease carbon content material improves weldability and reduces the potential for stress cracking by hydrogen sulfide sometimes found in oil and gasoline production and processing purposes.
Another example of supplies tied to a specific software include those for upstream oil and gasoline production. Many of those functions occur within 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 merchandise with world use now comply with dual materials specs to fulfill ASME and European requirements. For instance, steel castings are specified and authorized to both ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson typically provides its own stringent necessities similar to the warmth treating of high nickel alloys, extra demanding chemical composition or special welding procedures.
In the previous, Emerson has supplemented conventional ASTM and ASME specifications to attain the improved corrosion-resistance ranges and excessive temperature capabilities supplied by high-nickel alloys. This is now achieved by the new ASTM specification A990, which addresses each materials composition and high quality.
Figure three. Pressure-retaining parts of a valve are subjected to hydrostatic testing to evaluate the parts’ integrity. Visible leakage or seepage via a casting means automatic rejection.
Qualifying a foundry
As part of a potential foundry’s qualification, Emerson inspects and exams 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 three for categories A, B and C. For categories 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 providers 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 process could 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 because of the difference in cross-section between the base 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 material. The welder and procedure for this step should meet the standards outlined in Section IX of the ASME Boiler and Pressure Vessel Code. Test bars (3/8-inch thick) are minimize from the plate and bent over a 1½-inch mandrel per ASTM A990 right into a U-shape.
The bars are examined intently for cracking alongside the weld heat-affected zone, casting grain boundaries or dendrite boundaries. Failure to satisfy high quality standards will outcome in the disqualification of the foundry from further consideration. Casting patterns have to be dedicated solely to high-nickel alloy service. Use of carbon steel or a stainless-steel pattern is unacceptable as a result of differences in solidification properties.
Shrinkage charges for gates, risers and different equipment can vary significantly. Once the devoted pattern equipment for every of these elements has been secured, try-out castings are poured for every pattern-alloy mixture. The castings are then radiographed.
The intent is to reveal any inherent casting defects — similar to shrinkage — that must be eliminated by modifying the sample 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 solid Fisher valve our bodies for more than a decade. After an exploratory visit by procurement and manufacturing specialists, adopted by an intensive 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 carried out 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 thrice consecutively in the Beijing International Casting, Forging and Industrial Boiler Expo. compound gauge ราคา has twice acquired an Excellent Supplier award from Emerson.
Figure 5. This Chinese foundry meets all specifications for casting valve our bodies.
Summary
Control valve customers may be concerned when they learn certain valve components are not made in the united states or Europe, however elsewhere. Perhaps their concern stems from expertise with other inferior products, corresponding to appliances, clothes or electronics made in these nations and offered online. But if the valve parts are being equipped to a serious management valve vendor that has gone to great lengths to qualify the foundry or supplier, then customers may be assured the valves meet all specifications.
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