Across many kinds of products in a selection of industries, the apply of combining assorted parts from numerous resources all over the world is the rule, not the exception. Should this be a concern for a control valve user? For example, when an finish user discovers that several components are being made in China (Figure 1), should the user fear 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 focusing on product quality to ensure management valves function as designed, want minimal maintenance, carry out safely and function inside environmental regulations.
Yet, regardless of such efforts by the vendor, a management valve consumer might have questions on world sourcing and the country of origin. This article discusses how one main control valve vendor ensures product high quality. Many different management valve vendors observe the same or comparable procedures.
Quality specification brings world assurance
Emerson enforces a complete quality specification for its Fisher management valves that have to be met by suppliers of pressure-containing and structural metallic castings. The high quality specification includes more than a dozen necessities that apply to the next 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 potential supplier’s ability to satisfy materials specs and applicable worldwide codes and requirements — in addition to specific necessities related 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 should show a document of qualification by a third-party inspection company and conform to numerous standards, corresponding to ISO 9001:2000, ASME, A2LA, PED and others. It should cross a evaluation of its quality program in addition to on-site audits of the foundry’s processes and procedures corresponding to welding, warmth remedy and non-destructive examination. Additional proof of performance is set by evaluation of tryout castings to verify specs are met.
Welding procedures — Welding is used in the course of the manufacturing and upgrading of castings, such as when radiographic examination is required. Welding requirements state that procedures and welder qualifications must meet ASME Section IX (or EN ISO 15614-1 and ISO 9606-1) qualification requirements. Similarly, every lot of weld filler should adjust to ASME/AWS chemical evaluation specifications. 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 heat code. Material identification can be typically proven on the body casting, such as CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct each visible inspections and mechanical exams on pressure-retaining castings.
As-cast exterior and inner surfaces are inspected visually for unacceptable irregularities, including scorching tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing entails a hydrostatic pressure check to confirm the leak tightness of a control valve’s pressure-retaining parts, together with the physique and bonnet castings. The test procedure entails a fixture that closes off cavities that may be pressurized in service and then topics the part to the hydrostatic shell take a look at strain acceptable for the valve body material and class.
ASME B16.34 sets out the hydrostatic take a look at pressure to use for metal and alloy valves. It’s calculated by multiplying the working pressure by 1.5 and rounding to the subsequent larger 25 psig increment. Any visually detectable weeping or leaking through the strain boundary partitions that are part of the valve assembly is a compulsory trigger for rejection (Figure 3).
Compliance with these specifications should be ensured, in addition to with other necessities relating to supplies.
Figure 2. Markings determine the foundry and supplies of the valve physique. These control valve bodies had been solid at an Emerson-approved foundry in China.
Meeting material requirements
Valve casting integrity and high quality begins with specs that decision not just for premium supplies, but in addition for the materials that work greatest in the supposed applications. Big and ductility in addition to resistance to certain elements, including the make-up of the managed fluid, operating temperature and circulate velocity.
For instance, chemical composition have to be managed exactly to attain an alloy’s supposed performance stage. Carbon steel castings for valves meant for use in oil and gas functions must meet NACE SP0472 recommendations 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 present in oil and fuel manufacturing and processing functions.
Another example of materials tied to a selected software embrace those for upstream oil and fuel manufacturing. Many of those functions occur in the arctic areas of Russia and Canada. For this service, castings are ASME SA 352 Grade LCC, whereas forgings should meet ASME SA 350 Grade LF2.
Many products with international use now adjust to twin material specs to fulfill ASME and European requirements. For instance, steel castings are specified and certified to each ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson often adds its own stringent necessities such as the warmth treating of high nickel alloys, extra demanding chemical composition or special welding procedures.
In the previous, Emerson has supplemented standard ASTM and ASME specs to achieve the enhanced corrosion-resistance ranges and excessive temperature capabilities provided by high-nickel alloys. This is now achieved by the model new ASTM specification A990, which addresses each material composition and quality.
Figure 3. Pressure-retaining components of a valve are subjected to hydrostatic testing to evaluate the parts’ integrity. Visible leakage or seepage through a casting means computerized rejection.
Qualifying a foundry
As part of a prospective foundry’s qualification, Emerson inspects and checks Fisher valve castings. Non-destructive testing radiography is used as a monitoring device. ASTM A990 Class C requires radiography of the primary casting of every pattern. The acceptance criterion is Level three 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 efficiency in corrosive services and elevated temperatures. However, if high-nickel castings are improperly ready, they’ll pose main problems, together with poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification course of can be adopted to keep away from these casting difficulties.
The foundry should forged 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 distinction in cross-section between the bottom 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 right 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 meet quality requirements will result in the disqualification of the foundry from further consideration. Casting patterns should be devoted 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 other accessories can differ considerably. Once the devoted pattern tools for each of those components has been secured, try-out castings are poured for every pattern-alloy combination. The castings are then radiographed.
The intent is to reveal any inherent casting defects — corresponding to shrinkage — that need to be eradicated by modifying the pattern rigging.
Figure four. In a foundry evaluation, 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 forged Fisher valve our bodies for greater than a decade. After an exploratory go to 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 standard of the castings it produces, the Chinese foundry has carried out 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 three times consecutively in 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 specifications for casting valve our bodies.
Summary
Control valve users could be concerned when they study sure valve components aren’t made in the U.S. or Europe, however elsewhere. Perhaps their concern stems from experience with different inferior products, such as appliances, garments or electronics made in these international locations and bought online. But if the valve parts are being equipped to a major management valve vendor that has gone to nice lengths to qualify the foundry or supplier, then users could be assured the valves meet all specifications.
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