Across many forms of merchandise in a wide range of industries, the follow of combining assorted components from varied assets around 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 a number of elements are being made in China (Figure 1), should the consumer worry concerning the quality?
When coping with a serious 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 specializing in product quality to ensure management valves function as designed, want minimal upkeep, perform safely and operate within environmental rules.
Yet, despite such efforts by the seller, a management valve consumer may have questions on world sourcing and the nation of origin. This article discusses how one main control valve vendor ensures product quality. Many different management valve vendors observe the same or related procedures.
Quality specification brings world assurance
Emerson enforces a complete quality specification for its Fisher management valves that have to be met by suppliers of pressure-containing and structural metallic castings. The quality specification includes more than a dozen necessities that apply to the following areas:
Supplier qualification
Welding procedures
Marking inspection and testing
Tryout and pattern castings
Production castings
Certification of compliance
Supplier qualification — Suppliers undergo a rigorous qualification course of. The process thoroughly investigates a potential supplier’s ability to meet material specifications and relevant worldwide codes and requirements — in addition to particular necessities associated to component manufacture. In เครื่องมือวัดความดันคือ of castings, a foundry is considered “qualified” when it passes a important evaluation by Fisher’s engineers.
The foundry should 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 pass a evaluate of its high quality program as properly as on-site audits of the foundry’s processes and procedures corresponding to welding, warmth therapy and non-destructive examination. Additional proof of performance is set by analysis of tryout castings to verify specs are met.
Welding procedures — Welding is used during the production and upgrading of castings, corresponding to when radiographic examination is required. Welding necessities 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 specs. In Europe, compliance have to be to EN499. Weld filler must have precise 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 additionally be usually shown on the body 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 inside surfaces are inspected visually for unacceptable irregularities, including hot tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing includes a hydrostatic strain check to verify the leak tightness of a control valve’s pressure-retaining parts, including the physique and bonnet castings. The check procedure entails a fixture that closes off cavities that would be pressurized in service and then topics the element to the hydrostatic shell test strain appropriate for the valve physique materials and sophistication.
ASME B16.34 units out the hydrostatic take a look at pressure to use for steel and alloy valves. It’s calculated by multiplying the working strain by 1.5 and rounding to the subsequent higher 25 psig increment. Any visually detectable weeping or leaking by way of the stress boundary partitions which are a part of the valve meeting is a compulsory cause for rejection (Figure 3).
Compliance with these specs have to be ensured, in addition to with other necessities relating to supplies.
Figure 2. Markings determine the foundry and supplies of the valve body. These control valve bodies have been cast at an Emerson-approved foundry in China.
Meeting materials requirements
Valve casting integrity and high quality begins with specifications that call not only for premium materials, but additionally for the materials that work best in the intended applications. These software requirements include strength and ductility in addition to resistance to certain components, together with the makeup of the controlled fluid, operating temperature and circulate velocity.
For occasion, chemical composition should be controlled precisely to attain an alloy’s meant performance degree. Carbon metal castings for valves meant to be used in oil and gas applications should meet NACE SP0472 suggestions that chemical composition be managed to lower than zero.43% carbon equivalency. The decrease carbon content improves weldability and reduces the potential for stress cracking by hydrogen sulfide sometimes present in oil and gas production and processing functions.
Another example of materials tied to a selected utility include these for upstream oil and gas manufacturing. Many of those functions occur 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.
Many products with world use now comply with twin materials specifications to meet ASME and European requirements. For example, steel castings are specified and licensed to both ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson usually provides its own stringent requirements similar to the heat treating of excessive nickel alloys, more demanding chemical composition or special welding procedures.
In the past, Emerson has supplemented standard ASTM and ASME specifications to attain the enhanced corrosion-resistance levels and high temperature capabilities offered by high-nickel alloys. This is now accomplished by the brand new ASTM specification A990, which addresses each material composition and high quality.
Figure 3. 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 prospective foundry’s qualification, Emerson inspects and exams Fisher valve castings. Non-destructive testing radiography is used as a monitoring device. ASTM A990 Class C requires radiography of the first casting of every pattern. The acceptance criterion is Level three for categories A, B and C. For classes D through G, no cracking, sizzling 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 will pose main problems, including 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 difficult to cast due to the distinction in cross-section between the bottom 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 a matching composition weld materials. The welder and process 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 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 meet high quality requirements will result in the disqualification of the foundry from additional consideration. Casting patterns should be devoted solely to high-nickel alloy service. Use of carbon metal or a stainless-steel pattern is unacceptable due to variations in solidification properties.
Shrinkage rates for gates, risers and other equipment can range considerably. Once the devoted sample gear for every of those 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 pattern rigging.
เกจวัดแรงดันอาร์กอน . 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 solid Fisher valve bodies for more than a decade. After an exploratory go to by procurement and manufacturing specialists, adopted by an intensive qualification course of, the foundry was permitted and has been delivering high-quality valve physique and bonnet castings to Fisher valve manufacturing websites.
To help ensure the standard of the castings it produces, the Chinese foundry has carried out international standards 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 specifications for casting valve our bodies.
Summary
Control valve customers may be involved once they learn certain valve elements aren’t made in the us or Europe, however elsewhere. Perhaps their concern stems from expertise with different inferior products, corresponding to appliances, garments or electronics made in these nations and offered online. But if the valve components are being equipped to a significant control valve vendor that has gone to great lengths to qualify the foundry or supplier, then users could be assured the valves meet all specs.
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