Across many types of products in quite lots of industries, the follow of combining assorted components from various resources all over the world is the rule, not the exception. Should this be a concern for a control valve user? For example, when an end consumer discovers that several parts are being made in China (Figure 1), ought to the user worry about the quality?
When coping with a significant valve vendor, the reply 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 maintenance, perform safely and operate within environmental laws.
Yet, despite such efforts by the vendor, a control valve user may have questions about international sourcing and the nation of origin. This article discusses how one main management valve vendor ensures product quality. Many other control valve vendors follow the identical or related procedures.
Quality specification brings global assurance
Emerson enforces a comprehensive high 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 greater than a dozen necessities 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 endure a rigorous qualification process. The course of completely investigates a possible supplier’s capacity to meet material specifications and applicable international codes and requirements — as properly as particular necessities related to element manufacture. In the case of castings, a foundry is considered “qualified” when it passes a crucial analysis by Fisher’s engineers.
The foundry must show a record of qualification by a third-party inspection company and conform to varied standards, such as ISO 9001:2000, ASME, A2LA, PED and others. It must cross a review of its quality program as well as on-site audits of the foundry’s processes and procedures corresponding to welding, warmth remedy and non-destructive examination. Additional proof of performance is set by analysis of tryout castings to verify specifications are met.
Welding procedures — Welding is used during the production 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 requirements. Similarly, each lot of weld filler must adjust to ASME/AWS chemical evaluation specs. In Europe, compliance have to be to EN499. Weld filler will have to 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 can additionally be usually proven on the body casting, similar to CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct each visible inspections and mechanical checks 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 entails a hydrostatic pressure check to substantiate the leak tightness of a management valve’s pressure-retaining parts, including the physique and bonnet castings. The check procedure involves a fixture that closes off cavities that would be pressurized in service and then topics the element to the hydrostatic shell test pressure appropriate for the valve body materials and sophistication.
ASME B16.34 units out the hydrostatic take a look at stress to make use of for steel and alloy valves. It’s calculated by multiplying the working pressure by 1.5 and rounding to the following greater 25 psig increment. Any visually detectable weeping or leaking by way of the stress boundary walls which would possibly be a half of the valve assembly is a compulsory trigger for rejection (Figure 3).
Compliance with these specifications have to be ensured, in addition to with other necessities regarding materials.
Figure 2. Markings establish the foundry and materials of the valve physique. These control valve bodies had been forged 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 also for the materials that work greatest in the supposed purposes. These application requirements include power and ductility as properly as resistance to certain elements, together with the make-up of the managed fluid, operating temperature and circulate velocity.
For occasion, chemical composition must be controlled exactly to realize an alloy’s meant efficiency degree. Carbon steel castings for valves meant to be used in oil and gas functions must meet NACE SP0472 suggestions that chemical composition be managed to lower than 0.43% carbon equivalency. The lower carbon content improves weldability and reduces the potential for stress cracking by hydrogen sulfide sometimes found in oil and fuel manufacturing and processing purposes.
Another instance of supplies tied to a particular software embrace these for upstream oil and gas manufacturing. Many of these purposes occur in 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 material specifications to fulfill ASME and European requirements. For เกจวัดแรงดัน10bar , metal castings are specified and certified to both ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson often provides its personal stringent necessities such as the heat treating of high nickel alloys, more demanding chemical composition or particular welding procedures.
In the past, Emerson has supplemented standard ASTM and ASME specifications to realize the improved corrosion-resistance ranges and excessive temperature capabilities provided by high-nickel alloys. This is now achieved by the brand new ASTM specification A990, which addresses each material composition and high quality.
Figure three. Pressure-retaining elements of a valve are subjected to hydrostatic testing to judge the parts’ integrity. Visible leakage or seepage by way of a casting means automated rejection.
Qualifying a foundry
As part of a potential foundry’s qualification, Emerson inspects and tests Fisher valve castings. Non-destructive testing radiography is used as a monitoring software. ASTM A990 Class C requires radiography of the first casting of each sample. The acceptance criterion is Level 3 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 efficiency in corrosive providers and elevated temperatures. However, if high-nickel castings are improperly ready, they can 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 should forged a 1-inch thick high-nickel test plate (Figure 4) that meets ASTM Material Specification A990. It’s troublesome to cast because of the difference in cross-section between the bottom of the weld cavity (in the center) and the overall 1-inch thickness of the plate. The cavity of the poured plate is then full of a matching composition weld material. 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 reduce 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 along the weld heat-affected zone, casting grain boundaries or dendrite boundaries. Failure to satisfy quality standards will outcome within 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 pattern is unacceptable due to variations in solidification properties.
Shrinkage rates for gates, risers and different accessories can differ significantly. Once the devoted sample tools for each of those parts 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 filled with weld filler, then sliced to yield a bar for bend testing.
A certified 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, adopted by an extensive qualification process, the foundry was approved and has been delivering high-quality valve body and bonnet castings to Fisher valve manufacturing websites.
To assist ensure the standard of the castings it produces, the Chinese foundry has implemented international standards and has obtained certifications for German TUV and CE, Norway DNV, German Lloyd’s and American ABS, and has handed worldwide quality system certifications of ISO 9001 and QS -9000.
The foundry has been awarded Gold Medals three times 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 specifications for casting valve bodies.
Summary
Control valve customers can be concerned after they learn sure valve elements are not made in the united states or Europe, but elsewhere. Perhaps their concern stems from expertise with other inferior merchandise, corresponding to appliances, clothes or electronics made in those international locations and offered on-line. But if the valve components are being provided to a significant management valve vendor that has gone to great lengths to qualify the foundry or supplier, then customers can be assured the valves meet all specifications.
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