Across many kinds of products in a selection of industries, the follow of combining assorted parts from varied assets all over the world is the rule, not the exception. Should this be a concern for a control valve user? For instance, when an finish consumer discovers that a quantity of elements are being made in China (Figure 1), ought to the consumer worry in regards to the quality?
When dealing with a major valve vendor, the reply is “no.” There shouldn’t be any room for doubt when the vendor has multiple checks and balances in place specializing in product high quality to make sure management valves operate as designed, need minimal maintenance, carry out safely and operate inside environmental laws.
Yet, regardless of such efforts by the vendor, a control valve user may have questions on world sourcing and the nation of origin. This article discusses how one major control valve vendor ensures product high quality. Many different control valve vendors observe the identical or similar procedures.
Quality specification brings world assurance
Emerson enforces a complete quality specification for its Fisher management valves that must be met by suppliers of pressure-containing and structural steel castings. The quality specification consists of greater 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 endure a rigorous qualification process. The process completely investigates a possible supplier’s capability to meet materials specs and applicable worldwide codes and requirements — as nicely as specific necessities related to part 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 should reveal a document of qualification by a third-party inspection agency and conform to various requirements, such as ISO 9001:2000, ASME, A2LA, PED and others. It should cross a review of its quality program as well as on-site audits of the foundry’s processes and procedures corresponding to welding, warmth treatment and non-destructive examination. Additional proof of performance is determined by evaluation of tryout castings to confirm specifications are met.
Welding procedures — Welding is used through the manufacturing 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, each lot of weld filler must comply with ASME/AWS chemical analysis specs. In Europe, compliance should be to EN499. Weld filler will have to have actual chemistry.
Marking inspection and testing — Valve physique castings have markings (Figure 2) that determine the foundry that poured the casting and that indicate the heat code. Material identification can also be usually shown on the physique casting, similar to CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct each visible inspections and mechanical tests on pressure-retaining castings.
As-cast external and internal surfaces are inspected visually for unacceptable irregularities, together with sizzling tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing involves a hydrostatic pressure test to verify the leak tightness of a control valve’s pressure-retaining elements, including the physique and bonnet castings. The test procedure entails a fixture that closes off cavities that would be pressurized in service and then topics the component to the hydrostatic shell check strain applicable for the valve physique material and class.
ASME B16.34 sets out the hydrostatic test pressure to make use of for steel and alloy valves. It’s calculated by multiplying the working stress by 1.5 and rounding to the subsequent greater 25 psig increment. Any visually detectable weeping or leaking by way of the pressure boundary walls which might be part of the valve meeting is a mandatory cause for rejection (Figure 3).
Compliance with these specifications must be ensured, as nicely as with other necessities relating to supplies.
Figure 2. Markings determine the foundry and supplies of the valve physique. These control valve bodies have been forged at an Emerson-approved foundry in China.
Meeting materials requirements
Valve casting integrity and high quality begins with specifications that call not only for premium supplies, but additionally for the supplies that work finest in the meant functions. เกวัดแรงดันน้ำ include strength and ductility in addition to resistance to certain factors, including the makeup of the controlled fluid, working temperature and flow velocity.
For occasion, chemical composition should be managed exactly to achieve an alloy’s supposed efficiency level. Carbon metal castings for valves intended for use in oil and gas functions should meet NACE SP0472 suggestions that chemical composition be controlled to less than zero.43% carbon equivalency. The decrease carbon content material improves weldability and reduces the potential for stress cracking by hydrogen sulfide sometimes found in oil and gasoline manufacturing and processing purposes.
Another example of materials tied to a particular application embody those for upstream oil and gasoline production. Many of these applications occur within the arctic areas of Russia and Canada. For เกจ์วัดแรงดันแก๊ส , castings are ASME SA 352 Grade LCC, whereas forgings must meet ASME SA 350 Grade LF2.
Many products with international use now comply with twin materials specifications to fulfill ASME and European requirements. For instance, steel castings are specified and authorized to both ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson usually adds its personal stringent requirements similar to the heat treating of excessive nickel alloys, more demanding chemical composition or particular welding procedures.
In the past, Emerson has supplemented typical ASTM and ASME specs to attain the enhanced corrosion-resistance ranges and excessive temperature capabilities supplied by high-nickel alloys. This is now completed by the brand new ASTM specification A990, which addresses each material composition and high quality.
Figure 3. Pressure-retaining elements of a valve are subjected to hydrostatic testing to judge 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 tests Fisher valve castings. Non-destructive testing radiography is used as a monitoring device. ASTM A990 Class C requires radiography of the primary casting of each pattern. The acceptance criterion is Level 3 for categories A, B and C. For classes D by way of G, no cracking, scorching tears or inserts are allowed as laid out in ASTM A990.
High-nickel alloy castings present improved performance in corrosive providers and elevated temperatures. However, if high-nickel castings are improperly ready, they can pose major problems, including poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification course of could be adopted to avoid these casting difficulties.
The foundry must cast a 1-inch thick high-nickel check plate (Figure 4) that meets ASTM Material Specification A990. It’s troublesome to forged because of the distinction 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 crammed with 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 cut from the plate and bent over a 1½-inch mandrel per ASTM A990 into a U-shape.
The bars are examined closely for cracking along the weld heat-affected zone, casting grain boundaries or dendrite boundaries. Failure to satisfy high quality standards will end result in the disqualification of the foundry from further consideration. Casting patterns have to be dedicated solely to high-nickel alloy service. Use of carbon steel or a stainless-steel sample is unacceptable as a end result of variations in solidification properties.
Shrinkage rates for gates, risers and different equipment can differ considerably. Once the devoted sample tools for each of those components has been secured, try-out castings are poured for every pattern-alloy mixture. The castings are then radiographed.
The intent is to disclose any inherent casting defects — similar to shrinkage — that have to be eliminated by modifying the sample rigging.
Figure four. In a foundry analysis, a casting is crammed with weld filler, then sliced to yield a bar for bend testing.
A qualified foundry
Emerson has used a Chinese foundry (Figure 5) to cast Fisher valve our bodies for more than a decade. After an exploratory visit by procurement and manufacturing specialists, followed by an intensive qualification course of, the foundry was permitted and has been delivering high-quality valve physique and bonnet castings to Fisher valve manufacturing sites.
To assist guarantee 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 three times consecutively in the Beijing International Casting, Forging and Industrial Boiler Expo. It has twice obtained an Excellent Supplier award from Emerson.
Figure 5. This Chinese foundry meets all specifications for casting valve our bodies.
Summary
Control valve customers may be concerned after they study certain valve parts usually are not made in the us or Europe, but elsewhere. Perhaps their concern stems from expertise with other inferior merchandise, similar to home equipment, clothes or electronics made in these countries and sold on-line. But if the valve parts are being supplied to a significant management valve vendor that has gone to great lengths to qualify the foundry or provider, then customers may be assured the valves meet all specifications.
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