Across many forms of merchandise in a variety of industries, the follow of combining assorted parts from numerous sources around the world is the rule, not the exception. Should this be a priority for a control valve user? For instance, when an finish person discovers that a quantity of parts are being made in China (Figure 1), ought to the user worry concerning the quality?
When coping 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 specializing in product high quality to make sure management valves function as designed, want minimal maintenance, perform safely and function inside environmental regulations.
Yet, despite such efforts by the vendor, a control valve consumer might have questions about global sourcing and the country of origin. This article discusses how one main management valve vendor ensures product quality. Many other management valve vendors observe the identical or similar procedures.
Quality specification brings international assurance
Emerson enforces a comprehensive high quality specification for its Fisher control valves that have to be met by suppliers of pressure-containing and structural metallic 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 pattern castings
Production castings
Certification of compliance
Supplier qualification — Suppliers endure a rigorous qualification course of. The process totally investigates a possible supplier’s capability to meet material specifications and applicable international codes and standards — in addition to particular requirements 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 demonstrate a document of qualification by a third-party inspection agency and conform to varied requirements, corresponding to ISO 9001:2000, ASME, A2LA, PED and others. It should cross a evaluate of its quality program as nicely as on-site audits of the foundry’s processes and procedures such as welding, heat remedy and non-destructive examination. Additional proof of performance is determined by evaluation of tryout castings to verify specs are met.
Welding procedures — Welding is used through the manufacturing 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 standards. Similarly, every lot of weld filler must adjust to ASME/AWS chemical analysis specifications. In Europe, compliance have to be to EN499. Weld filler should 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 warmth code. Material identification can be usually shown on the physique casting, such as 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 includes a hydrostatic stress check to verify the leak tightness of a control valve’s pressure-retaining parts, including the physique and bonnet castings. The take a look at process includes a fixture that closes off cavities that may be pressurized in service after which subjects the part to the hydrostatic shell test strain acceptable for the valve physique materials and sophistication.
ASME B16.34 units 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 next higher 25 psig increment. Any visually detectable weeping or leaking through the pressure boundary partitions which may be part of the valve assembly is a mandatory trigger for rejection (Figure 3).
Compliance with these specs must be ensured, as properly as with different requirements concerning supplies.
Figure 2. Markings identify the foundry and materials of the valve body. These management valve bodies had been solid at an Emerson-approved foundry in China.
Meeting material requirements
Valve casting integrity and high quality begins with specifications that decision not just for premium materials, but also for the supplies that work greatest in the intended functions. These software requirements embrace strength and ductility as well as resistance to sure factors, including the makeup of the managed fluid, working temperature and flow velocity.
For occasion, chemical composition should be controlled exactly to attain an alloy’s meant performance stage. Carbon steel castings for valves meant for use in oil and gas purposes should meet NACE SP0472 suggestions that chemical composition be controlled to less than 0.43% carbon equivalency. The decrease carbon content material improves weldability and reduces the potential for stress cracking by hydrogen sulfide typically found in oil and gasoline production and processing applications.
Another instance of supplies tied to a particular utility embody those for upstream oil and gasoline production. Many of these functions happen in the arctic areas of Russia and Canada. For this service, castings are ASME SA 352 Grade LCC, whereas forgings must meet ASME SA 350 Grade LF2.
Many products with world use now adjust to dual materials specs to fulfill ASME and European requirements. For instance, metal castings are specified and certified to each ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson usually adds its own stringent requirements such as the warmth treating of high nickel alloys, more demanding chemical composition or special welding procedures.
In the past, Emerson has supplemented standard ASTM and ASME specifications to attain the enhanced corrosion-resistance levels and excessive temperature capabilities provided 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 parts of a valve are subjected to hydrostatic testing to evaluate the parts’ integrity. Visible leakage or seepage via a casting means automatic rejection.
Qualifying a foundry
As part of a prospective 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 primary casting of every pattern. The acceptance criterion is Level 3 for categories A, B and C. For categories D via G, no cracking, sizzling tears or inserts are allowed as laid out in ASTM A990.
High-nickel alloy castings provide improved efficiency in corrosive providers and elevated temperatures. However, if high-nickel castings are improperly ready, they’ll pose major problems, including 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 must solid 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 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 an identical 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 into a U-shape.
The bars are examined intently for cracking alongside the weld heat-affected zone, casting grain boundaries or dendrite boundaries. Failure to fulfill quality standards will end result within 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 sample is unacceptable because of variations in solidification properties.
Shrinkage rates for gates, risers and other equipment can range considerably. Once the devoted sample gear for every of these elements 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 eliminated 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 cast Fisher valve bodies for greater than a decade. After an exploratory go to 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 sites.
To assist ensure เกจวัดแรงดันpsi of the castings it produces, the Chinese foundry has applied worldwide requirements and has obtained certifications for German TUV and CE, Norway DNV, German Lloyd’s and American ABS, and has passed worldwide 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.
Summary
Control valve users can be involved when they study sure valve elements are not made in the united states or Europe, however elsewhere. Perhaps their concern stems from expertise with different inferior merchandise, such as home equipment, garments or electronics made in those international locations and bought on-line. But if the valve parts are being equipped to a significant management valve vendor that has gone to great lengths to qualify the foundry or supplier, then users can be assured the valves meet all specs.
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