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Across many forms of products in a variety of industries, the apply of combining assorted elements from various assets all over the world is the rule, not the exception. Should this be a priority for a management valve user? For example, when an finish person discovers that a quantity of elements are being made in China (Figure 1), should the consumer fear about the quality?
When coping with a significant 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, want minimal maintenance, carry out safely and operate within environmental laws.
Yet, despite such efforts by the seller, a management valve person might have questions about world sourcing and the nation of origin. This article discusses how one main management valve vendor ensures product quality. Many other management valve vendors comply with the same or related procedures.
Quality specification brings international assurance
Emerson enforces a comprehensive quality specification for its Fisher control valves that have to be met by suppliers of pressure-containing and structural steel castings. The quality specification consists of greater than a dozen requirements 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 undergo a rigorous qualification course of. The process thoroughly investigates a potential supplier’s capability to fulfill materials specifications and relevant worldwide codes and requirements — as nicely as specific requirements associated to part manufacture. In the case of castings, a foundry is considered “qualified” when it passes a critical evaluation by Fisher’s engineers.
The foundry should demonstrate a record of qualification by a third-party inspection agency and conform to various requirements, such as ISO 9001:2000, ASME, A2LA, PED and others. It must pass a review of its high quality program in addition to on-site audits of the foundry’s processes and procedures such as welding, heat therapy and non-destructive examination. Additional proof of efficiency is decided by evaluation of tryout castings to confirm specifications are met.
Welding procedures — Welding is used during the production and upgrading of castings, similar to when radiographic examination is required. Welding necessities state that procedures and welder qualifications should 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 analysis specifications. In Europe, compliance should be to EN499. Weld filler must have actual 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 also be sometimes proven on the physique casting, such as CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct each visible inspections and mechanical checks on pressure-retaining castings.
As-cast external and internal surfaces are inspected visually for unacceptable irregularities, together with scorching tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing involves a hydrostatic stress take a look at to confirm the leak tightness of a control valve’s pressure-retaining elements, together with the physique and bonnet castings. The test procedure involves a fixture that closes off cavities that may be pressurized in service and then subjects the part to the hydrostatic shell take a look at stress acceptable for the valve physique material and class.
ASME B16.34 sets out the hydrostatic take a look at stress to make use of for steel and alloy valves. It’s calculated by multiplying the working strain by 1.5 and rounding to the next greater 25 psig increment. Any visually detectable weeping or leaking by way of the stress boundary partitions that are part of the valve meeting is a mandatory trigger for rejection (Figure 3).
Compliance with these specifications should be ensured, in addition to with different requirements relating to materials.
เครื่องมือวัดความดันคือ . Markings determine the foundry and materials of the valve body. These management valve our bodies were solid at an Emerson-approved foundry in China.
Meeting materials necessities
Valve casting integrity and high quality begins with specs that decision not only for premium materials, but in addition for the supplies that work greatest within the supposed purposes. These software requirements embrace strength and ductility as properly as resistance to sure elements, together with the makeup of the controlled fluid, working temperature and circulate velocity.
For instance, chemical composition should be managed exactly to achieve an alloy’s supposed performance level. Carbon metal castings for valves supposed to be used in oil and gasoline applications should meet NACE SP0472 suggestions that chemical composition be controlled to lower than zero.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 fuel manufacturing and processing functions.
Another example of supplies tied to a specific software embrace those for upstream oil and gasoline production. Many of those functions occur in the arctic regions of Russia and Canada. For this service, castings are ASME SA 352 Grade LCC, whereas forgings should meet ASME SA 350 Grade LF2.
Many merchandise with international use now comply with twin material specs to meet ASME and European standards. For instance, steel castings are specified and licensed to both ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson usually provides its personal stringent necessities similar to 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 specifications to attain the improved corrosion-resistance levels and high temperature capabilities supplied by high-nickel alloys. This is now accomplished by the model new ASTM specification A990, which addresses both material composition and quality.
Figure 3. Pressure-retaining components of a valve are subjected to hydrostatic testing to gauge the parts’ integrity. Visible leakage or seepage via a casting means automatic rejection.
Qualifying a foundry
As a 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 sample. The acceptance criterion is Level three for classes A, B and C. For classes D by way of G, no cracking, hot tears or inserts are allowed as specified in ASTM A990.
High-nickel alloy castings provide improved performance in corrosive providers and elevated temperatures. However, if high-nickel castings are improperly ready, they will pose main problems, including poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification course of can be adopted to avoid these casting difficulties.
The foundry should solid a 1-inch thick high-nickel test plate (Figure 4) that meets ASTM Material Specification A990. It’s difficult to forged because of the difference 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 filled with a matching composition weld materials. The welder and procedure for this step should meet the requirements 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 carefully for cracking alongside the weld heat-affected zone, casting grain boundaries or dendrite boundaries. Failure to satisfy quality requirements will result in the disqualification of the foundry from additional consideration. Casting patterns should be dedicated solely to high-nickel alloy service. Use of carbon steel or a stainless-steel pattern is unacceptable because of variations in solidification properties.
Shrinkage rates for gates, risers and different accessories can range considerably. Once the dedicated sample tools for each 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 eliminated by modifying the sample rigging.
Figure four. In a foundry evaluation, a casting is crammed with weld filler, then sliced to yield a bar for bend testing.
A qualified 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, followed by an in depth qualification process, the foundry was permitted and has been delivering high-quality valve body and bonnet castings to Fisher valve manufacturing websites.
To help guarantee the standard of the castings it produces, the Chinese foundry has carried out worldwide requirements 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 three 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 bodies.
Summary
Control valve users may be involved once they be taught certain valve elements are not made in the U.S. or Europe, however elsewhere. Perhaps their concern stems from experience with other inferior products, corresponding to appliances, clothes or electronics made in those international locations and bought on-line. But if the valve parts are being provided to a major control valve vendor that has gone to great lengths to qualify the foundry or provider, then customers can be assured the valves meet all specifications.
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