Across many kinds of products in a selection of industries, the apply of mixing assorted components from various assets all over the world is the rule, not the exception. Should this be a priority for a control valve user? For example, when an end user discovers that a number of elements are being made in China (Figure 1), should the consumer worry in regards to the quality?
When dealing with a serious 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 ensure management valves function as designed, want minimal maintenance, carry out safely and function inside environmental laws.
Yet, regardless of เกจวัดแรงดันไทวัสดุ by the seller, a control valve person might have questions about international sourcing and the nation of origin. This article discusses how one main management valve vendor ensures product high quality. Many different control valve distributors observe the identical or related procedures.
Quality specification brings international assurance
Emerson enforces a comprehensive high quality specification for its Fisher control valves that have to be met by suppliers of pressure-containing and structural metal castings. The quality specification contains greater than a dozen requirements that apply to the next 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 process. The process completely investigates a possible supplier’s ability to satisfy material specs and applicable worldwide codes and requirements — in addition to particular necessities associated to part 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 should reveal a report of qualification by a third-party inspection agency and conform to various requirements, such as ISO 9001:2000, ASME, A2LA, PED and others. It should pass a evaluate of its quality program in addition to on-site audits of the foundry’s processes and procedures such as welding, warmth therapy and non-destructive examination. Additional proof of efficiency is determined by evaluation of tryout castings to verify specifications are met.
Welding procedures — Welding is used through the production and upgrading of castings, corresponding to when radiographic examination is required. Welding necessities state that procedures and welder qualifications must meet ASME Section IX (or EN ISO 15614-1 and ISO 9606-1) qualification standards. Similarly, every lot of weld filler should comply with ASME/AWS chemical analysis specs. In Europe, compliance must be to EN499. Weld filler will have to have actual chemistry.
Marking inspection and testing — Valve physique castings have markings (Figure 2) that establish the foundry that poured the casting and that point out the heat code. Material identification can also be usually shown on the body casting, similar to CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct each visual inspections and mechanical tests on pressure-retaining castings.
As-cast external and inside surfaces are inspected visually for unacceptable irregularities, together with sizzling 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 body and bonnet castings. The take a look at process entails a fixture that closes off cavities that may be pressurized in service after which subjects the component to the hydrostatic shell test pressure applicable for the valve body materials and sophistication.
ASME B16.34 units out the hydrostatic check strain to make use of for steel and alloy valves. It’s calculated by multiplying the working pressure by 1.5 and rounding to the subsequent larger 25 psig increment. Any visually detectable weeping or leaking by way of the pressure boundary walls that are a half of the valve meeting is a compulsory cause for rejection (Figure 3).
Compliance with these specs have to be ensured, as nicely as with other necessities regarding supplies.
Figure 2. Markings determine the foundry and supplies of the valve physique. These management valve bodies had been solid at an Emerson-approved foundry in China.
Meeting material requirements
Valve casting integrity and quality begins with specifications that call not just for premium materials, but also for the supplies that work finest in the supposed purposes. These utility requirements embrace power and ductility as properly as resistance to certain factors, together with the makeup of the managed fluid, working temperature and flow velocity.
For occasion, chemical composition have to be managed exactly to achieve an alloy’s intended performance level. Carbon metal castings for valves meant to be used in oil and gasoline functions should meet NACE SP0472 recommendations that chemical composition be controlled to lower than 0.43% carbon equivalency. The decrease carbon content improves weldability and reduces the potential for stress cracking by hydrogen sulfide usually present in oil and gasoline manufacturing and processing functions.
Another example of materials tied to a specific software include these for upstream oil and gas production. Many of those 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 comply with dual material specifications to meet ASME and European standards. For instance, metal castings are specified and licensed to both ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson typically adds its personal stringent requirements corresponding to the warmth treating of excessive nickel alloys, extra demanding chemical composition or special welding procedures.
In the previous, Emerson has supplemented typical ASTM and ASME specs to realize the improved corrosion-resistance levels and high temperature capabilities provided by high-nickel alloys. This is now accomplished by the brand 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 evaluate the parts’ integrity. Visible leakage or seepage by way of a casting means automatic rejection.
Qualifying a foundry
As a part of a prospective foundry’s qualification, Emerson inspects and exams Fisher valve castings. Non-destructive testing radiography is used as a monitoring tool. ASTM A990 Class C requires radiography of the primary casting of every pattern. The acceptance criterion is Level 3 for classes A, B and C. For classes D by way of G, no cracking, hot tears or inserts are allowed as specified in ASTM A990.
High-nickel alloy castings provide improved efficiency in corrosive providers and elevated temperatures. However, if high-nickel castings are improperly prepared, they will pose main problems, together with poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification process may be followed to keep away from these casting difficulties.
The foundry should cast a 1-inch thick high-nickel take a look at plate (Figure 4) that meets ASTM Material Specification A990. It’s tough to cast 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 crammed with a matching composition weld materials. The welder and procedure 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 minimize from the plate and bent over a 1½-inch mandrel per ASTM A990 into a U-shape.
The bars are examined closely for cracking along the weld heat-affected zone, casting grain boundaries or dendrite boundaries. Failure to meet quality standards will outcome in the disqualification of the foundry from additional consideration. Casting patterns should be dedicated solely to high-nickel alloy service. Use of carbon metal or a stainless-steel sample is unacceptable because of differences in solidification properties.
Shrinkage charges for gates, risers and other equipment can vary considerably. Once the dedicated sample equipment for every of these components has been secured, try-out castings are poured for every pattern-alloy combination. 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.
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 forged Fisher valve bodies for more than a decade. After an exploratory visit by procurement and manufacturing specialists, followed by an in depth qualification course of, the foundry was permitted and has been delivering high-quality valve body and bonnet castings to Fisher valve manufacturing sites.
To help 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. It has twice received an Excellent Supplier award from Emerson.
Figure 5. This Chinese foundry meets all specs for casting valve bodies.
Summary
Control valve customers can be concerned when they learn sure valve parts usually are not made in the us or Europe, but elsewhere. Perhaps their concern stems from experience with other inferior products, similar to home equipment, garments or electronics made in those international locations and bought online. But if the valve elements are being provided to a major control valve vendor that has gone to nice lengths to qualify the foundry or supplier, then customers may be assured the valves meet all specs.
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