Across many forms of merchandise in a big selection of industries, the practice of mixing assorted components from various resources around the world is the rule, not the exception. Should this be a concern for a management valve user? For example, when an finish person discovers that a number of parts are being made in China (Figure 1), ought to the user worry in regards to the quality?
When coping with a major valve vendor, the answer 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 control valves function as designed, need minimal upkeep, carry out safely and function within environmental laws.
Yet, regardless of such efforts by the vendor, a control valve person could have questions about world sourcing and the nation of origin. This article discusses how one main management valve vendor ensures product quality. Many other control valve distributors observe the same or related procedures.
Quality specification brings world assurance
Emerson enforces a comprehensive high quality specification for its Fisher control valves that should be met by suppliers of pressure-containing and structural steel castings. The quality specification contains more than a dozen requirements that apply to the next 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 course of. The course of thoroughly investigates a potential supplier’s capacity to meet materials specs and applicable worldwide codes and requirements — in addition to particular necessities associated to part 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 reveal a report of qualification by a third-party inspection agency and conform to various standards, such as ISO 9001:2000, ASME, A2LA, PED and others. It must pass a evaluation of its quality program as nicely as 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 confirm specifications are met.
Welding procedures — Welding is used through the manufacturing and upgrading of castings, similar 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, each lot of weld filler must adjust to ASME/AWS chemical evaluation specs. In Europe, compliance must be to EN499. Weld filler should have precise chemistry.
Marking inspection and testing — Valve body castings have markings (Figure 2) that identify the foundry that poured the casting and that indicate the warmth code. Material identification can also be usually proven 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 exterior and internal surfaces are inspected visually for unacceptable irregularities, together with scorching tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing entails a hydrostatic stress check to confirm the leak tightness of a management valve’s pressure-retaining parts, including the body and bonnet castings. The take a look at procedure involves a fixture that closes off cavities that might be pressurized in service and then topics the element to the hydrostatic shell test stress appropriate for the valve body materials and sophistication.
ASME B16.34 units out the hydrostatic test pressure to use for steel and alloy valves. It’s calculated by multiplying the working stress by 1.5 and rounding to the next larger 25 psig increment. Any visually detectable weeping or leaking through the strain boundary walls that are part of the valve meeting is a compulsory trigger for rejection (Figure 3).
Compliance with these specs have to be ensured, in addition to with other requirements relating to materials.
Figure 2. Markings determine the foundry and supplies of the valve body. These control valve bodies had been forged at an Emerson-approved foundry in China.
Meeting materials necessities
Valve casting integrity and high quality begins with specs that call not just for premium supplies, but in addition for the materials that work greatest in the intended applications. These application requirements include strength and ductility in addition to resistance to certain components, together with the make-up of the controlled fluid, operating temperature and circulate velocity.
For instance, chemical composition should be managed precisely to realize an alloy’s intended performance degree. Carbon metal castings for valves supposed to be used in oil and fuel applications must 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 usually found in oil and gasoline manufacturing and processing functions.
Another example of supplies tied to a selected software embrace those for upstream oil and gasoline production. Many of those applications occur 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 twin material specifications to satisfy ASME and European standards. For example, metal castings are specified and certified to both ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson often adds its own stringent requirements corresponding to the heat treating of excessive nickel alloys, extra demanding chemical composition or particular welding procedures.
In the past, Emerson has supplemented typical ASTM and ASME specs to achieve the enhanced corrosion-resistance levels and excessive temperature capabilities provided by high-nickel alloys. This is now accomplished by the new ASTM specification A990, which addresses both materials 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 by way of a casting means automated rejection.
Qualifying a foundry
As part of a prospective foundry’s qualification, Emerson inspects and exams Fisher valve castings. Non-destructive testing radiography is used as a monitoring software. ASTM A990 Class C requires radiography of the primary casting of each pattern. The acceptance criterion is Level three for categories A, B and C. For pressure gauge nuova fima ราคา through G, no cracking, sizzling tears or inserts are allowed as specified in ASTM A990.
High-nickel alloy castings present improved efficiency in corrosive companies and elevated temperatures. However, if high-nickel castings are improperly ready, they’ll pose major issues, together with poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification process could be followed to keep away from these casting difficulties.
The foundry must solid a 1-inch thick high-nickel take a look at plate (Figure 4) that meets ASTM Material Specification A990. It’s tough to solid because of the distinction in cross-section between the base of the weld cavity (in the center) and the overall 1-inch thickness of the plate. The cavity of the poured plate is then crammed with an identical composition weld material. The welder and process for this step must 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 along the weld heat-affected zone, casting grain boundaries or dendrite boundaries. Failure to satisfy high quality standards will outcome within the disqualification of the foundry from further consideration. Casting patterns must be devoted solely to high-nickel alloy service. Use of carbon metal or a stainless-steel sample is unacceptable because of variations in solidification properties.
Shrinkage rates for gates, risers and different accessories can differ significantly. Once the devoted sample tools for every of these parts 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 — similar to shrinkage — that need to be eradicated by modifying the pattern rigging.
Figure 4. 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 solid Fisher valve our bodies for more than a decade. After an exploratory go to by procurement and manufacturing specialists, adopted by an extensive qualification course of, the foundry was accredited and has been delivering high-quality valve physique and bonnet castings to Fisher valve manufacturing websites.
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 worldwide 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 received an Excellent Supplier award from Emerson.
Figure 5. This Chinese foundry meets all specs for casting valve our bodies.
Summary
Control valve customers could be involved when they learn sure valve components are not made in the us or Europe, but elsewhere. Perhaps their concern stems from experience with other inferior merchandise, such as home equipment, clothes or electronics made in those countries and sold on-line. But if the valve elements are being provided to a significant control valve vendor that has gone to great lengths to qualify the foundry or supplier, then users can be assured the valves meet all specifications.
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