Across many forms of merchandise in quite lots of industries, the follow of combining assorted elements from numerous sources around the world is the rule, not the exception. Should this be a concern for a control valve user? For instance, when an end person discovers that a number of components are being made in China (Figure 1), should the user worry about the quality?
When dealing with a major valve vendor, the reply is “no.” There shouldn’t be any room for doubt when the seller has multiple checks and balances in place specializing in product quality to ensure management valves operate as designed, need minimal upkeep, perform safely and function within environmental regulations.
Yet, despite such efforts by the vendor, a control valve consumer may have questions on world sourcing and the nation of origin. This article discusses how one major management valve vendor ensures product quality. Many other control valve distributors observe the identical or comparable procedures.
Quality specification brings global assurance
Emerson enforces a complete quality specification for its Fisher management valves that must be met by suppliers of pressure-containing and structural steel castings. The quality specification includes more than a dozen requirements that apply to the following areas:
Marking inspection and testing
Tryout and pattern castings
Certification of compliance
Supplier qualification — Suppliers bear a rigorous qualification course of. The process completely investigates a potential supplier’s capacity to satisfy material specs and relevant worldwide codes and requirements — as properly as particular necessities associated to component manufacture. In the case of castings, a foundry is considered “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 various standards, such as ISO 9001:2000, ASME, A2LA, PED and others. It should move a evaluate of its high quality program in addition to on-site audits of the foundry’s processes and procedures similar to welding, warmth treatment and non-destructive examination. Additional proof of performance is set by analysis of tryout castings to confirm specs are met.
Welding procedures — Welding is used in the course of the manufacturing and upgrading of castings, similar to 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 requirements. Similarly, each lot of weld filler should comply with ASME/AWS chemical evaluation specs. In Europe, compliance should be to EN499. Weld filler will have to have precise chemistry.
Marking inspection and testing — Valve physique castings have markings (Figure 2) that establish the foundry that poured the casting and that indicate the heat code. Material identification can be usually shown on the physique casting, such as CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct each visual inspections and mechanical tests on pressure-retaining castings.
As- เกจวัดแรงดันแก๊สlpgรถยนต์ and inner surfaces are inspected visually for unacceptable irregularities, including hot tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing includes a hydrostatic pressure check to verify the leak tightness of a management valve’s pressure-retaining elements, including the physique and bonnet castings. The test procedure entails a fixture that closes off cavities that might be pressurized in service after which subjects the part to the hydrostatic shell take a look at pressure appropriate for the valve body materials and class.
ASME B16.34 units out the hydrostatic check stress to use for steel and alloy valves. It’s calculated by multiplying the working pressure by 1.5 and rounding to the subsequent higher 25 psig increment. Any visually detectable weeping or leaking via the strain boundary walls that are a half of the valve meeting is a mandatory trigger for rejection (Figure 3).
Compliance with these specifications must be ensured, as nicely as with different requirements relating to materials.
Figure 2. Markings determine the foundry and materials of the valve physique. These management valve our bodies were solid at an Emerson-approved foundry in China.
Meeting material requirements
Valve casting integrity and quality begins with specs that decision not just for premium materials, but also for the materials that work finest within the supposed purposes. These utility requirements embrace strength and ductility as nicely as resistance to certain elements, together with the makeup of the controlled fluid, operating temperature and move velocity.
For occasion, chemical composition have to be managed precisely to realize an alloy’s supposed performance level. Carbon steel castings for valves supposed to be used in oil and fuel applications must meet NACE SP0472 suggestions that chemical composition be controlled to lower than 0.43% carbon equivalency. The decrease carbon content material improves weldability and reduces the potential for stress cracking by hydrogen sulfide sometimes found in oil and gasoline production and processing purposes.
Another instance of supplies tied to a selected software include 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, while forgings must meet ASME SA 350 Grade LF2.
Many merchandise with global use now adjust to dual material specifications to fulfill ASME and European requirements. For example, metal castings are specified and certified to both ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson often provides its personal stringent requirements such as the heat treating of high nickel alloys, extra demanding chemical composition or particular welding procedures.
In the previous, Emerson has supplemented standard ASTM and ASME specs to realize the enhanced corrosion-resistance ranges and excessive temperature capabilities supplied by high-nickel alloys. This is now completed by the new ASTM specification A990, which addresses both material composition and quality.
Figure 3. Pressure-retaining elements of a valve are subjected to hydrostatic testing to judge the parts’ integrity. Visible leakage or seepage via a casting means automated rejection.
Qualifying a foundry
As part of a potential 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 sample. The acceptance criterion is Level 3 for classes A, B and C. For categories D by way of G, no cracking, sizzling tears or inserts are allowed as laid out in ASTM A990.
High-nickel alloy castings provide improved performance in corrosive services and elevated temperatures. However, if high-nickel castings are improperly ready, they’ll pose main problems, including poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification process can be adopted to keep away from these casting difficulties.
The foundry should solid a 1-inch thick high-nickel check plate (Figure 4) that meets ASTM Material Specification A990. It’s difficult to solid due to the difference 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 crammed with an identical composition weld materials. 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 closely for cracking along the weld heat-affected zone, casting grain boundaries or dendrite boundaries. Failure to meet quality requirements will outcome within the disqualification of the foundry from further consideration. Casting patterns have to be devoted solely to high-nickel alloy service. Use of carbon steel or a stainless-steel sample is unacceptable because of differences in solidification properties.
Shrinkage rates for gates, risers and other accessories can vary significantly. Once the dedicated sample tools for every of these 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 4. 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 more than a decade. After an exploratory visit by procurement and manufacturing specialists, adopted by an intensive qualification process, the foundry was approved and has been delivering high-quality valve physique and bonnet castings to Fisher valve manufacturing websites.
To assist ensure the standard of the castings it produces, the Chinese foundry has carried out international requirements and has obtained certifications for German TUV and CE, Norway DNV, German Lloyd’s and American ABS, and has handed worldwide 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 obtained an Excellent Supplier award from Emerson.
Figure 5. This Chinese foundry meets all specs for casting valve bodies.
Control valve customers can be concerned when they be taught sure valve parts are not made in the us or Europe, but elsewhere. Perhaps their concern stems from expertise with different inferior merchandise, similar to appliances, garments or electronics made in these international locations and bought on-line. But if the valve components are being provided to a serious control valve vendor that has gone to great lengths to qualify the foundry or supplier, then users could be assured the valves meet all specs.
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