Across many kinds of merchandise 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 control valve user? For instance, when an finish user discovers that several parts are being made in China (Figure 1), should the consumer worry about the quality?
When dealing with a serious valve vendor, the reply is “no.” There shouldn’t be any room for doubt when the seller has multiple checks and balances in place focusing on product high quality to make sure management valves operate as designed, want minimal maintenance, perform safely and operate inside environmental regulations.
Yet, regardless of such efforts by the vendor, a control valve person might have questions about world sourcing and the nation of origin. This article discusses how one major control valve vendor ensures product quality. Many different control valve vendors follow the same or comparable procedures.
Quality specification brings international assurance
Emerson enforces a comprehensive quality specification for its Fisher control valves that should be met by suppliers of pressure-containing and structural metal castings. The high quality specification contains more 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 materials specifications and relevant international codes and standards — in addition to specific necessities associated to element manufacture. In the case of castings, a foundry is taken into account “qualified” when it passes a important evaluation by Fisher’s engineers.
The foundry must show a report of qualification by a third-party inspection agency and conform to numerous standards, corresponding to ISO 9001:2000, ASME, A2LA, PED and others. It should pass a review of its quality program as nicely as on-site audits of the foundry’s processes and procedures similar to welding, warmth treatment and non-destructive examination. Additional proof of efficiency is determined by evaluation of tryout castings to confirm specifications are met.
Welding procedures — Welding is used through the production and upgrading of castings, such as 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, each lot of weld filler must adjust to ASME/AWS chemical analysis specs. In Europe, compliance must be to EN499. Weld filler should have actual chemistry.
Marking inspection and testing — Valve physique castings have markings (Figure 2) that identify the foundry that poured the casting and that point out the warmth code. Material identification can also be sometimes shown on the physique casting, similar to 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, including sizzling tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing involves a hydrostatic stress take a look at to verify the leak tightness of a management valve’s pressure-retaining parts, including the body and bonnet castings. The check process involves a fixture that closes off cavities that might be pressurized in service after which subjects the component to the hydrostatic shell take a look at strain appropriate for the valve body material and class.
ASME B16.34 sets out the hydrostatic take a look at strain to use for steel and alloy valves. It’s calculated by multiplying the working strain by 1.5 and rounding to the following greater 25 psig increment. Any visually detectable weeping or leaking via the stress boundary partitions which would possibly be part of the valve assembly is a mandatory cause for rejection (Figure 3).
Compliance with these specs should be ensured, as nicely as with other requirements concerning supplies.
Figure 2. Markings identify the foundry and supplies of the valve body. These control valve our bodies had been forged at an Emerson-approved foundry in China.
Meeting materials requirements
Valve casting integrity and high quality begins with specs that decision not just for premium materials, but in addition for the materials that work finest in the intended functions. These utility requirements embrace energy and ductility in addition to resistance to certain elements, together with the make-up of the managed fluid, operating temperature and circulate velocity.
For occasion, chemical composition must be controlled precisely to realize an alloy’s intended efficiency stage. Carbon steel castings for valves supposed for use in oil and gasoline functions must meet NACE SP0472 suggestions that chemical composition be controlled to less than 0.43% carbon equivalency. The lower carbon content material improves weldability and reduces the potential for stress cracking by hydrogen sulfide typically present in oil and gasoline production and processing applications.
Another example of materials tied to a specific utility include those for upstream oil and gasoline production. Many of these functions happen in the arctic regions of Russia and Canada. For ร้านซ่อมเครื่องวัดความดัน , castings are ASME SA 352 Grade LCC, while forgings must meet ASME SA 350 Grade LF2.
Many products with global use now adjust to dual materials specs to meet ASME and European standards. For instance, metal castings are specified and licensed to each ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson often adds its personal stringent necessities corresponding to the heat treating of excessive nickel alloys, extra demanding chemical composition or particular welding procedures.
In the previous, Emerson has supplemented typical ASTM and ASME specifications to attain the enhanced corrosion-resistance levels and high temperature capabilities supplied by high-nickel alloys. This is now completed by the model new ASTM specification A990, which addresses both material composition and quality.
Figure three. Pressure-retaining components of a valve are subjected to hydrostatic testing to judge the parts’ integrity. Visible leakage or seepage through a casting means computerized rejection.
Qualifying a foundry
As part of a potential foundry’s qualification, Emerson inspects and checks Fisher valve castings. Non-destructive testing radiography is used as a monitoring software. ASTM A990 Class C requires radiography of the first casting of each pattern. The acceptance criterion is Level three for categories A, B and C. For categories D via G, no cracking, scorching tears or inserts are allowed as specified in ASTM A990.
High-nickel alloy castings present improved efficiency in corrosive services and elevated temperatures. However, if high-nickel castings are improperly prepared, they can pose major issues, 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 should cast a 1-inch thick high-nickel test plate (Figure 4) that meets ASTM Material Specification A990. It’s tough to cast due to 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 filled with an identical composition weld materials. 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 minimize from the plate and bent over a 1½-inch mandrel per ASTM A990 into a U-shape.
The bars are examined carefully for cracking alongside the weld heat-affected zone, casting grain boundaries or dendrite boundaries. Failure to fulfill quality standards will outcome in 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 pattern is unacceptable because of differences in solidification properties.
Shrinkage rates for gates, risers and different accessories can range significantly. Once the dedicated pattern gear for each of these elements 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 — such as shrinkage — that have to be eradicated 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 certified foundry
Emerson has used a Chinese foundry (Figure 5) to cast Fisher valve bodies for greater than a decade. After an exploratory visit by procurement and manufacturing specialists, adopted by an extensive qualification course of, the foundry was approved 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 applied worldwide requirements and has obtained certifications for German TUV and CE, Norway DNV, German Lloyd’s and American ABS, and has passed international high 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 obtained an Excellent Supplier award from Emerson.
Figure 5. This Chinese foundry meets all specifications for casting valve bodies.
Summary
Control valve users can be concerned once they be taught certain valve components usually are not made in the U.S. or Europe, but elsewhere. Perhaps their concern stems from experience with different inferior products, such as appliances, garments or electronics made in those international locations and sold online. But if the valve parts are being equipped 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 specifications.
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