Across many forms of merchandise in quite a lot of industries, the apply of mixing assorted elements from varied resources around the globe is the rule, not the exception. Should this be a priority for a management valve user? For เครื่องมือที่ใช้วัดความดัน , when an end person discovers that several components are being made in China (Figure 1), ought to the person worry in regards to the quality?
When dealing with a major valve vendor, the answer 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 ensure management valves function as designed, need minimal maintenance, carry out safely and function inside environmental regulations.
Yet, despite such efforts by the seller, a control valve person may have questions about world sourcing and the nation of origin. This article discusses how one main control valve vendor ensures product high quality. Many different control valve vendors observe the identical or similar procedures.
Quality specification brings global assurance
Emerson enforces a comprehensive quality specification for its Fisher management valves that should be met by suppliers of pressure-containing and structural steel castings. The quality specification contains greater than a dozen requirements that apply to the next areas:
Marking inspection and testing
Tryout and pattern castings
Certification of compliance
Supplier qualification — Suppliers undergo a rigorous qualification process. The process completely investigates a potential supplier’s capability to fulfill materials specs and applicable worldwide codes and standards — in addition to specific necessities related 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 demonstrate a document of qualification by a third-party inspection company and conform to various requirements, similar to ISO 9001:2000, ASME, A2LA, PED and others. It should move a review of its quality program as well as on-site audits of the foundry’s processes and procedures similar to welding, heat therapy and non-destructive examination. Additional proof of efficiency is set by evaluation of tryout castings to verify specs 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 must 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 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 warmth code. Material identification can be typically shown on the body casting, such as CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct each visual inspections and mechanical tests on pressure-retaining castings.
As-cast external and internal surfaces are inspected visually for unacceptable irregularities, including scorching tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing includes a hydrostatic pressure check to confirm the leak tightness of a management valve’s pressure-retaining parts, including the body and bonnet castings. The check procedure includes a fixture that closes off cavities that might be pressurized in service after which topics the element to the hydrostatic shell take a look at strain applicable for the valve physique material and sophistication.
ASME B16.34 units out the hydrostatic test pressure to use for metal and alloy valves. It’s calculated by multiplying the working stress by 1.5 and rounding to the subsequent higher 25 psig increment. Any visually detectable weeping or leaking via the strain boundary partitions that are a part of the valve meeting is a mandatory cause for rejection (Figure 3).
Compliance with these specs must be ensured, as properly as with other requirements regarding supplies.
Figure 2. Markings determine the foundry and materials of the valve physique. These management valve our bodies had been solid at an Emerson-approved foundry in China.
Meeting materials requirements
Valve casting integrity and quality begins with specifications that call not just for premium materials, but additionally for the materials that work best in the meant functions. These utility requirements embrace power and ductility in addition to resistance to certain elements, together with the makeup of the controlled fluid, working temperature and circulate velocity.
For occasion, chemical composition must be controlled exactly to achieve an alloy’s intended performance stage. Carbon metal castings for valves meant for use in oil and gas functions should meet NACE SP0472 recommendations that chemical composition be controlled to lower than 0.43% carbon equivalency. The lower carbon content improves weldability and reduces the potential for stress cracking by hydrogen sulfide sometimes present in oil and fuel production and processing functions.
Another example of materials tied to a specific utility embrace these for upstream oil and gas production. Many of these applications occur within the arctic areas 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 adjust to twin materials specs to meet ASME and European requirements. For example, metal castings are specified and certified to each ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson usually 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 typical ASTM and ASME specs to attain the improved corrosion-resistance ranges and excessive temperature capabilities offered by high-nickel alloys. This is now completed 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 gauge the parts’ integrity. Visible leakage or seepage via a casting means automated rejection.
Qualifying a foundry
As part of a potential foundry’s qualification, Emerson inspects and exams 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 sample. The acceptance criterion is Level three for classes 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 performance in corrosive services and elevated temperatures. However, if high-nickel castings are improperly ready, they can pose main problems, 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 must cast a 1-inch thick high-nickel take a look at plate (Figure 4) that meets ASTM Material Specification A990. It’s tough 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 materials. The welder and procedure for this step should meet the requirements 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 right 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 meet quality standards will outcome in the disqualification of the foundry from additional consideration. Casting patterns have to be devoted solely to high-nickel alloy service. Use of carbon metal or a stainless-steel pattern is unacceptable because of variations in solidification properties.
Shrinkage charges for gates, risers and different accessories can vary considerably. Once the devoted pattern equipment for each of these components 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 — such as shrinkage — that need to be eliminated by modifying the pattern rigging.
Figure 4. In a foundry analysis, 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 cast Fisher valve our bodies for more than a decade. After an exploratory visit by procurement and manufacturing specialists, adopted by an in depth qualification process, the foundry was accredited and has been delivering high-quality valve body and bonnet castings to Fisher valve manufacturing sites.
To assist guarantee the quality of the castings it produces, the Chinese foundry has implemented worldwide standards 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 3 times 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 specifications for casting valve our bodies.
Control valve customers could be concerned after they learn certain valve elements usually are not made in the U.S. or Europe, but elsewhere. Perhaps their concern stems from experience with other inferior products, such as appliances, clothes or electronics made in these countries and sold on-line. But if the valve parts are being provided to a significant management valve vendor that has gone to great lengths to qualify the foundry or supplier, then users may be assured the valves meet all specifications.
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