Across many forms of products in a wide range of industries, the apply of mixing assorted components from varied assets around the globe is the rule, not the exception. Should this be a concern for a management valve user? For instance, when an finish consumer discovers that a number of components are being made in China (Figure 1), should the user worry in regards to the quality?
When dealing with a significant valve vendor, the reply is “no.” There shouldn’t be any room for doubt when the vendor has a number of checks and balances in place specializing in product high quality to make sure management valves operate as designed, need minimal maintenance, perform safely and function within environmental rules.
Yet, despite such efforts by the vendor, a control valve user could have questions about international sourcing and the nation of origin. This article discusses how one major control valve vendor ensures product quality. Many other management valve vendors observe the same or similar procedures.
Quality specification brings world assurance
Emerson enforces a complete high quality specification for its Fisher control valves that must be met by suppliers of pressure-containing and structural steel 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 course of. The process completely investigates a potential supplier’s capacity to satisfy material specifications and applicable international codes and requirements — in addition to specific necessities associated to part manufacture. In the case of castings, a foundry is considered “qualified” when it passes a crucial evaluation by Fisher’s engineers.
The foundry must reveal a document of qualification by a third-party inspection agency and conform to varied requirements, similar to ISO 9001:2000, ASME, A2LA, PED and others. It must cross a evaluation of its high quality program as nicely as on-site audits of the foundry’s processes and procedures such as welding, heat treatment 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 through the production and upgrading of castings, similar 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, every lot of weld filler must adjust to ASME/AWS chemical analysis specs. In Europe, compliance must be to EN499. Weld filler must have precise 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 warmth code. Material identification can also be sometimes shown on the physique casting, corresponding to CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct both visible inspections and mechanical tests 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 entails a hydrostatic strain test to confirm the leak tightness of a control valve’s pressure-retaining parts, including the physique and bonnet castings. The check procedure includes a fixture that closes off cavities that may be pressurized in service after which subjects the part to the hydrostatic shell take a look at stress acceptable for the valve body material and class.
ASME B16.34 units out the hydrostatic take a look at strain to make use of for steel and alloy valves. It’s calculated by multiplying the working strain by 1.5 and rounding to the subsequent greater 25 psig increment. Any visually detectable weeping or leaking via the strain boundary partitions that are a part of the valve meeting is a compulsory cause for rejection (Figure 3).
Compliance with these specs must be ensured, as properly as with different requirements concerning materials.
Figure 2. Markings identify the foundry and supplies of the valve body. These management valve our bodies were forged at an Emerson-approved foundry in China.
Meeting material necessities
Valve casting integrity and high quality begins with specifications that call not only for premium materials, but additionally for the materials that work finest in the supposed applications. These application requirements embrace strength and ductility in addition to resistance to certain factors, including the makeup of the controlled fluid, operating temperature and move velocity.
For instance, chemical composition should be controlled precisely to realize an alloy’s supposed efficiency degree. Carbon metal castings for valves intended to be used in oil and fuel applications must meet NACE SP0472 recommendations that chemical composition be managed to less 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 these for upstream oil and gasoline production. Many of those functions occur in the arctic areas 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 twin materials specifications to satisfy 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 typically provides its own stringent requirements such as the heat treating of high nickel alloys, more demanding chemical composition or particular welding procedures.
In the past, Emerson has supplemented conventional ASTM and ASME specs to realize the enhanced corrosion-resistance ranges and high temperature capabilities offered by high-nickel alloys. This is now accomplished by the brand new ASTM specification A990, which addresses both materials composition and high quality.
Figure 3. Pressure-retaining elements of a valve are subjected to hydrostatic testing to evaluate the parts’ integrity. Visible leakage or seepage via a casting means automated rejection.
Qualifying a foundry
As a half of a prospective 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 first casting of each pattern. The acceptance criterion is Level 3 for categories A, B and C. For classes D via G, no cracking, sizzling tears or inserts are allowed as laid out in ASTM A990.
High-nickel alloy castings provide improved performance in corrosive providers and elevated temperatures. However, if high-nickel castings are improperly ready, they will pose major issues, including poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification course of may be adopted to keep away from these casting difficulties.
digital pressure gauge must forged a 1-inch thick high-nickel check plate (Figure 4) that meets ASTM Material Specification A990. It’s difficult to solid because of the distinction 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 filled with a matching composition weld materials. The welder and procedure 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 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 fulfill quality requirements will end result within 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 sample is unacceptable because of differences in solidification properties.
Shrinkage rates for gates, risers and other accessories can vary considerably. Once the devoted sample equipment for each of those 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 — corresponding to shrinkage — that must 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 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 intensive qualification course of, the foundry was approved and has been delivering high-quality valve body and bonnet castings to Fisher valve manufacturing websites.
To help ensure the quality of the castings it produces, the Chinese foundry has implemented international requirements 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 3 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 may be involved once they be taught certain valve components aren’t made in the united states or Europe, but elsewhere. Perhaps their concern stems from experience with different inferior products, corresponding to appliances, garments or electronics made in these nations and bought online. But if the valve components are being provided to a major management valve vendor that has gone to great lengths to qualify the foundry or supplier, then customers could be assured the valves meet all specifications.
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