Across many kinds of products in a wide range of industries, the follow of mixing assorted parts from varied sources around the globe is the rule, not the exception. Should this be a priority for a management valve user? For example, when an end user discovers that several components are being made in China (Figure 1), should the person worry concerning 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 focusing on product high quality to make sure control valves operate as designed, want minimal upkeep, carry out safely and function inside environmental rules.
Yet, despite such efforts by the seller, a management valve user may have questions about international sourcing and the country of origin. This article discusses how one major management valve vendor ensures product quality. Many other management valve distributors follow the identical or comparable procedures.
Quality specification brings world assurance
Emerson enforces a complete quality specification for its Fisher control valves that should be met by suppliers of pressure-containing and structural steel castings. The quality specification consists of greater than a dozen requirements that apply to the following areas:
Supplier qualification
Welding procedures
Marking inspection and testing
Tryout and pattern castings
Production castings
Certification of compliance
Supplier qualification — Suppliers bear a rigorous qualification process. The course of thoroughly investigates a possible supplier’s ability to satisfy material specs and relevant worldwide codes and standards — in addition to specific necessities associated to part manufacture. In the case of castings, a foundry is considered “qualified” when it passes a critical evaluation by Fisher’s engineers.
The foundry should reveal a document of qualification by a third-party inspection company and conform to various standards, such as ISO 9001:2000, ASME, A2LA, PED and others. It must pass a evaluation of its high 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 decided by analysis of tryout castings to verify specifications are met.
เพรสเชอร์เกจ — Welding is used in the course of the manufacturing 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 standards. Similarly, every lot of weld filler must adjust to ASME/AWS chemical evaluation specs. In Europe, compliance have to be to EN499. Weld filler should 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 heat code. Material identification is also usually proven on the body casting, corresponding to CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct each visual inspections and mechanical exams on pressure-retaining castings.
As-cast external and internal surfaces are inspected visually for unacceptable irregularities, including hot tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing includes a hydrostatic stress take a look at to substantiate the leak tightness of a management valve’s pressure-retaining elements, including the body and bonnet castings. The test procedure includes a fixture that closes off cavities that may be pressurized in service after which subjects the element to the hydrostatic shell take a look at strain acceptable for the valve body materials and class.
ASME B16.34 sets out the hydrostatic take a look at pressure to use for steel and alloy valves. It’s calculated by multiplying the working strain by 1.5 and rounding to the subsequent larger 25 psig increment. Any visually detectable weeping or leaking by way of the stress boundary walls that are a part of the valve meeting is a compulsory cause for rejection (Figure 3).
Compliance with these specs should be ensured, in addition to with different requirements relating to supplies.
Figure 2. Markings determine the foundry and supplies of the valve body. These control valve our bodies were forged at an Emerson-approved foundry in China.
Meeting material requirements
Valve casting integrity and quality begins with specifications that decision not only for premium materials, but additionally for the supplies that work best in the supposed purposes. These utility requirements embrace energy and ductility as well as resistance to sure components, together with the make-up of the managed fluid, operating temperature and flow velocity.
For occasion, chemical composition have to be managed exactly to realize an alloy’s meant efficiency stage. Carbon steel castings for valves supposed to be used in oil and gas functions should meet NACE SP0472 recommendations that chemical composition be managed to less than 0.43% carbon equivalency. The lower carbon content improves weldability and reduces the potential for stress cracking by hydrogen sulfide typically found in oil and fuel manufacturing and processing functions.
Another example of materials tied to a selected software include these for upstream oil and gas production. Many of those purposes occur within the arctic regions 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 international use now comply with dual materials specifications to fulfill ASME and European requirements. For example, steel castings are specified and certified to each ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson often adds its own stringent requirements such as the warmth treating of high nickel alloys, more demanding chemical composition or particular welding procedures.
In the previous, Emerson has supplemented conventional ASTM and ASME specifications to achieve the enhanced corrosion-resistance ranges and high temperature capabilities supplied by high-nickel alloys. This is now accomplished by the model new ASTM specification A990, which addresses each material composition and high quality.
Figure 3. Pressure-retaining components 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 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 sample. The acceptance criterion is Level 3 for classes 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 provide improved efficiency in corrosive services and elevated temperatures. However, if high-nickel castings are improperly ready, they will pose major issues, together with poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification process may be adopted to avoid 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 due to 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 minimize 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 satisfy high quality standards will outcome in the disqualification of the foundry from further consideration. Casting patterns should be dedicated solely to high-nickel alloy service. Use of carbon steel or a stainless-steel pattern is unacceptable as a outcome of differences in solidification properties.
Shrinkage rates for gates, risers and other accessories can vary significantly. Once the dedicated pattern gear for every of these 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 must 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 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, adopted by an in depth qualification process, the foundry was approved and has been delivering high-quality valve physique and bonnet castings to Fisher valve manufacturing sites.
To assist diaphragm seal of the castings it produces, the Chinese foundry has implemented 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 acquired an Excellent Supplier award from Emerson.
Figure 5. This Chinese foundry meets all specs for casting valve bodies.
Summary
Control valve users can be involved after they be taught sure valve components aren’t made in the U.S. or Europe, but elsewhere. Perhaps their concern stems from experience with other inferior merchandise, corresponding to appliances, garments or electronics made in those nations and offered online. But if the valve elements are being supplied to a major management valve vendor that has gone to great lengths to qualify the foundry or provider, then customers may be assured the valves meet all specs.
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