Across many forms of products in a wide selection of industries, the practice of mixing assorted elements from various assets around the globe is the rule, not the exception. Should this be a concern for a control valve user? For instance, when an end person discovers that a quantity of components are being made in China (Figure 1), should the consumer 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 seller has a number of checks and balances in place focusing on product high quality to make sure management valves function as designed, need minimal upkeep, carry out safely and operate inside environmental laws.
Yet, regardless of such efforts by the seller, a control valve person might have questions about global sourcing and the country of origin. This article discusses how one main control valve vendor ensures product high quality. Many different management valve vendors observe the same or comparable procedures.
Quality specification brings international assurance
Emerson enforces a comprehensive quality specification for its Fisher management valves that should be met by suppliers of pressure-containing and structural metallic castings. The quality specification contains more 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 bear a rigorous qualification process. The process totally investigates a possible supplier’s capability to fulfill material specs and relevant worldwide codes and standards — in addition to specific requirements 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 show a record of qualification by a third-party inspection agency and conform to numerous requirements, corresponding to ISO 9001:2000, ASME, A2LA, PED and others. It should cross a evaluation of its high quality program as properly as on-site audits of the foundry’s processes and procedures corresponding to welding, warmth remedy and non-destructive examination. Additional proof of efficiency is set by analysis of tryout castings to verify specs are met.
Welding procedures — Welding is used in the course of 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, each lot of weld filler must adjust to ASME/AWS chemical evaluation specs. In Europe, compliance must be to EN499. Weld filler should have precise chemistry.
Marking inspection and testing — Valve body castings have markings (Figure 2) that establish the foundry that poured the casting and that point out the warmth code. Material identification can also be usually 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, together with scorching tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing entails a hydrostatic pressure check to confirm the leak tightness of a management valve’s pressure-retaining parts, together with the physique and bonnet castings. The test procedure involves a fixture that closes off cavities that might be pressurized in service and then topics the part to the hydrostatic shell take a look at stress appropriate for the valve body materials and sophistication.
ASME B16.34 sets out the hydrostatic take a look at pressure to use for metal and alloy valves. It’s calculated by multiplying the working stress by 1.5 and rounding to the following larger 25 psig increment. Any visually detectable weeping or leaking by way of the pressure boundary partitions that are a part of the valve meeting is a compulsory trigger for rejection (Figure 3).
Compliance with these specifications should be ensured, in addition to with different requirements concerning supplies.
Figure 2. Markings determine the foundry and supplies of the valve body. These management valve our bodies had been cast at an Emerson-approved foundry in China.
Meeting materials requirements
Valve casting integrity and quality begins with specifications that decision not just for premium materials, but additionally for the materials that work greatest in the intended functions. These utility requirements embody strength and ductility in addition to resistance to certain elements, together with the makeup of the controlled fluid, working temperature and flow velocity.
For occasion, chemical composition have to be managed exactly to attain an alloy’s meant performance level. Carbon metal castings for valves supposed to be used in oil and fuel purposes should 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 usually present in oil and gasoline manufacturing and processing functions.
Another instance of supplies tied to a particular application include those for upstream oil and gasoline manufacturing. Many of those functions occur in the arctic areas of Russia and Canada. For this service, castings are ASME SA 352 Grade LCC, whereas forgings should meet ASME SA 350 Grade LF2.
Many merchandise with global use now adjust to twin materials specifications to fulfill ASME and European standards. For instance, steel castings are specified and certified to both ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson often provides its personal stringent requirements corresponding to the heat treating of high nickel alloys, extra demanding chemical composition or special welding procedures.
In the past, Emerson has supplemented conventional ASTM and ASME specifications to realize the improved corrosion-resistance ranges and high temperature capabilities supplied by high-nickel alloys. เกจวัดแรงดันco2 is now completed by the model 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 through a casting means automatic rejection.
Qualifying a foundry
As a half of a potential foundry’s qualification, Emerson inspects and checks Fisher valve castings. Non-destructive testing radiography is used as a monitoring device. 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 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 prepared, they’ll pose major problems, together with 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 solid a 1-inch thick high-nickel take a look at plate (Figure 4) that meets ASTM Material Specification A990. It’s troublesome to forged due to the difference 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 full of a matching composition weld material. The welder and procedure 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 minimize 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 meet quality standards will result in the disqualification of the foundry from further consideration. Casting patterns must be dedicated 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 other accessories can range significantly. Once the devoted pattern tools for each of these parts has been secured, try-out castings are poured for each pattern-alloy mixture. The castings are then radiographed.
The intent is to reveal any inherent casting defects — such as shrinkage — that need to be eradicated by modifying the pattern rigging.
Figure 4. In a foundry evaluation, a casting is crammed with weld filler, then sliced to yield a bar for bend testing.
A certified foundry
Emerson has used a Chinese foundry (Figure 5) to forged Fisher valve bodies for greater than a decade. After an exploratory go to by procurement and manufacturing specialists, followed by an extensive qualification course of, the foundry was approved and has been delivering high-quality valve physique and bonnet castings to Fisher valve manufacturing sites.
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 handed international quality system certifications of ISO 9001 and QS -9000.
The foundry has been awarded Gold Medals thrice consecutively within 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 specifications for casting valve bodies.
Summary
Control valve customers could be concerned once they learn certain valve parts usually are not made in the U.S. or Europe, however elsewhere. Perhaps their concern stems from experience with different inferior merchandise, similar to home equipment, garments or electronics made in these international locations and bought online. But if the valve parts are being equipped to a significant control valve vendor that has gone to great lengths to qualify the foundry or supplier, then users can be assured the valves meet all specifications.
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