Across many forms of merchandise in a big selection of industries, the follow of combining 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 example, when an finish user discovers that a number of elements are being made in China (Figure 1), ought to the consumer worry concerning 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 multiple checks and balances in place specializing in product quality to make sure control valves operate as designed, need minimal maintenance, perform safely and operate within environmental rules.
Yet, despite such efforts by the seller, a control valve person could have questions about international sourcing and the nation of origin. This article discusses how one major management valve vendor ensures product quality. Many other management valve distributors observe the identical or similar procedures.
Quality specification brings world assurance
Emerson enforces a comprehensive quality specification for its Fisher management valves that have to be met by suppliers of pressure-containing and structural steel castings. The quality specification includes greater than a dozen requirements 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 undergo a rigorous qualification course of. The course of completely investigates a potential supplier’s capability to meet material specifications and applicable international codes and requirements — in addition to specific necessities related to component manufacture. In the case of castings, a foundry is taken into account “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 varied requirements, such as ISO 9001:2000, ASME, A2LA, PED and others. It must cross a evaluate of its quality program in addition to 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 through the production and upgrading of castings, such as when radiographic examination is required. Welding requirements state that procedures and welder qualifications must meet ASME Section IX (or EN ISO 15614-1 and ISO 9606-1) qualification requirements. Similarly, each lot of weld filler should comply with ASME/AWS chemical evaluation specifications. In Europe, compliance must be to EN499. เกจวัดแรงดันแก๊สlpgรถยนต์ should have actual chemistry.
Marking inspection and testing — Valve body 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 typically shown on the body casting, corresponding to CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct each visible inspections and mechanical exams on pressure-retaining castings.
As-cast exterior 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 test to verify 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 may be pressurized in service and then topics the element to the hydrostatic shell test stress appropriate for the valve physique materials and sophistication.
ASME B16.34 sets out the hydrostatic check stress to make use of for metal and alloy valves. It’s calculated by multiplying the working pressure by 1.5 and rounding to the next larger 25 psig increment. Any visually detectable weeping or leaking by way of the pressure boundary partitions which may be a half of the valve assembly is a compulsory trigger for rejection (Figure 3).
Compliance with these specifications should be ensured, as properly as with other necessities relating to supplies.
Figure 2. Markings identify the foundry and materials of the valve physique. These control valve bodies had been forged at an Emerson-approved foundry in China.
Meeting material requirements
Valve casting integrity and quality begins with specs that decision not only for premium supplies, but in addition for the materials that work finest in the intended applications. These software requirements embrace strength and ductility in addition to resistance to sure factors, together with the make-up of the controlled fluid, working temperature and move velocity.
For instance, chemical composition should be controlled precisely to attain an alloy’s intended efficiency level. Carbon metal castings for valves intended to be used in oil and gasoline applications should meet NACE SP0472 suggestions that chemical composition be controlled to less than 0.43% carbon equivalency. The decrease carbon content material improves weldability and reduces the potential for stress cracking by hydrogen sulfide usually found in oil and gasoline production and processing functions.
Another instance of supplies tied to a specific software include those for upstream oil and fuel production. Many of these functions occur in the arctic regions of Russia and Canada. For this service, castings are ASME SA 352 Grade LCC, while forgings must meet ASME SA 350 Grade LF2.
Many products with global use now comply with dual materials specifications to fulfill ASME and European requirements. For example, metal castings are specified and licensed to each ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson typically adds its personal 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 standard ASTM and ASME specifications to achieve the enhanced corrosion-resistance ranges and excessive temperature capabilities offered by high-nickel alloys. This is now accomplished by the model new ASTM specification A990, which addresses both 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 by way of a casting means automatic rejection.
Qualifying a foundry
As a part of a prospective foundry’s qualification, Emerson inspects and tests 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 by way of G, no cracking, sizzling tears or inserts are allowed as specified in ASTM A990.
High-nickel alloy castings present improved efficiency in corrosive providers and elevated temperatures. However, if high-nickel castings are improperly ready, they’ll pose main issues, together with poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification course of could be adopted to keep away from these casting difficulties.
The foundry should solid a 1-inch thick high-nickel check plate (Figure 4) that meets ASTM Material Specification A990. It’s troublesome to solid due to the distinction 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 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 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 meet high quality requirements will outcome within the disqualification of the foundry from further consideration. Casting patterns should be dedicated solely to high-nickel alloy service. Use of carbon metal or a stainless-steel sample is unacceptable due to differences in solidification properties.
Shrinkage rates for gates, risers and different equipment can differ considerably. Once the dedicated sample equipment for each of those elements 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 — similar to shrinkage — that need to be eradicated by modifying the pattern rigging.
Figure four. In a foundry evaluation, 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 bodies for greater 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 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 worldwide quality system certifications of ISO 9001 and QS -9000.
The foundry has been awarded Gold Medals 3 times 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 specs for casting valve our bodies.
Summary
Control valve users may be involved when they learn certain valve components usually are not made in the U.S. or Europe, but elsewhere. Perhaps their concern stems from expertise with other inferior merchandise, corresponding to home equipment, garments or electronics made in those countries and bought online. But if the valve parts are being provided to a serious management valve vendor that has gone to great lengths to qualify the foundry or supplier, then customers could be assured the valves meet all specs.
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