Across many forms of merchandise in a big selection of industries, the apply of mixing assorted parts from varied sources around the world is the rule, not the exception. Should this be a concern for a control valve user? For example, when an end user discovers that a number of parts are being made in China (Figure 1), ought to the user fear concerning the quality?
When coping with a significant valve vendor, the answer is “no.” There shouldn’t be any room for doubt when the vendor has a quantity of checks and balances in place focusing on product high quality to make sure control valves operate as designed, want minimal maintenance, carry out safely and operate inside environmental laws.
Yet, despite such efforts by the vendor, a control valve person may have questions about global sourcing and the nation of origin. This article discusses how one major control valve vendor ensures product high quality. Many different control valve vendors comply with the identical or comparable procedures.
Quality specification brings world assurance
Emerson enforces a complete high quality specification for its Fisher control valves that have to be met by suppliers of pressure-containing and structural steel castings. The quality specification contains more than a dozen requirements that apply to the following 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 process. The course of completely investigates a possible supplier’s capability to fulfill material specifications and relevant international codes and standards — in addition to specific necessities associated to component manufacture. In the case of castings, a foundry is taken into account “qualified” when it passes a critical evaluation by Fisher’s engineers.
The foundry must show a record of qualification by a third-party inspection company and conform to various standards, similar to ISO 9001:2000, ASME, A2LA, PED and others. It must cross a evaluation of its high quality program in addition to on-site audits of the foundry’s processes and procedures such as welding, warmth remedy and non-destructive examination. Additional proof of performance is set by analysis of tryout castings to verify specifications are met.
Welding procedures — Welding is used through the manufacturing and upgrading of castings, such as 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 standards. Similarly, every lot of weld filler should comply with ASME/AWS chemical analysis specifications. In Europe, compliance should be to EN499. Weld filler will need to have actual chemistry.
Marking inspection and testing — Valve physique castings have markings (Figure 2) that establish the foundry that poured the casting and that point out the heat code. Material identification is also sometimes shown on the body casting, corresponding to CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct both visual inspections and mechanical tests on pressure-retaining castings.
As-cast exterior and internal surfaces are inspected visually for unacceptable irregularities, including hot tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing involves a hydrostatic strain test to confirm the leak tightness of a management valve’s pressure-retaining elements, including the body and bonnet castings. The take a look at procedure includes a fixture that closes off cavities that may be pressurized in service after which topics the part to the hydrostatic shell check pressure acceptable for the valve physique material and class.
ASME B16.34 sets out the hydrostatic check stress to use for steel and alloy valves. It’s calculated by multiplying the working stress by 1.5 and rounding to the following larger 25 psig increment. Any visually detectable weeping or leaking through the stress boundary walls that are part of the valve assembly is a mandatory cause for rejection (Figure 3).
Compliance with these specifications must be ensured, as properly as with different requirements regarding materials.
Figure 2. Markings establish the foundry and materials of the valve body. These control valve bodies were cast at an Emerson-approved foundry in China.
Meeting materials necessities
Valve casting integrity and high quality begins with specifications that decision not only for premium supplies, but in addition for the supplies that work best in the meant functions. These application requirements embrace strength and ductility in addition to resistance to certain elements, including the makeup of the managed fluid, operating temperature and circulate velocity.
For instance, chemical composition must be controlled precisely to achieve an alloy’s supposed performance stage. Carbon metal castings for valves intended to be used in oil and gasoline functions should meet NACE SP0472 recommendations that chemical composition be managed to less than zero.43% carbon equivalency. The lower carbon content improves weldability and reduces the potential for stress cracking by hydrogen sulfide sometimes found in oil and gasoline manufacturing and processing functions.
เกจวัดแรงดันดิจิตอล of materials tied to a particular utility embody these for upstream oil and gas manufacturing. Many of these applications occur in the arctic regions 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 international use now adjust to twin materials specs to fulfill ASME and European standards. For example, steel castings are specified and authorized to both ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson typically adds its personal stringent necessities similar to the heat treating of excessive nickel alloys, more demanding chemical composition or special welding procedures.
In the previous, Emerson has supplemented standard ASTM and ASME specs to realize the improved corrosion-resistance ranges and excessive temperature capabilities supplied by high-nickel alloys. This is now achieved by the new ASTM specification A990, which addresses both materials composition and high quality.
Figure three. Pressure-retaining elements of a valve are subjected to hydrostatic testing to evaluate the parts’ integrity. Visible leakage or seepage through a casting means automatic rejection.
Qualifying a foundry
As a part of a prospective foundry’s qualification, Emerson inspects and tests 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, scorching tears or inserts are allowed as laid out 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 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 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 troublesome to forged due to the distinction 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 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 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 end result within the disqualification of the foundry from additional consideration. Casting patterns have to be dedicated solely to high-nickel alloy service. Use of carbon metal or a stainless-steel pattern is unacceptable due to differences in solidification properties.
Shrinkage rates for gates, risers and different accessories can differ considerably. Once the dedicated pattern tools for every of those elements has been secured, try-out castings are poured for each pattern-alloy combination. The castings are then radiographed.
The intent is to reveal any inherent casting defects — such as shrinkage — that have to be eradicated by modifying the sample rigging.
Figure four. In a foundry evaluation, a casting is full of 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 bodies for more than a decade. After an exploratory visit by procurement and manufacturing specialists, followed by an intensive qualification process, the foundry was accredited and has been delivering high-quality valve body and bonnet castings to Fisher valve manufacturing websites.
To help guarantee the quality of the castings it produces, the Chinese foundry has carried out international standards and has obtained certifications for German TUV and CE, Norway DNV, German Lloyd’s and American ABS, and has passed international quality system certifications of ISO 9001 and QS -9000.
The foundry has been awarded Gold Medals thrice 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 specifications for casting valve bodies.
Summary
Control valve users can be involved once they study sure valve parts are not made in the U.S. or Europe, but elsewhere. Perhaps their concern stems from expertise with other inferior products, corresponding to appliances, clothes or electronics made in those nations and bought online. But if the valve elements are being provided to a serious 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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