Across many types of products in a variety of industries, the practice 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 consumer discovers that several elements are being made in China (Figure 1), should the person worry concerning the quality?
When dealing with a significant valve vendor, the reply is “no.” There shouldn’t be any room for doubt when the seller has a quantity of checks and balances in place focusing on product quality to ensure control valves function as designed, need minimal upkeep, perform safely and function inside environmental regulations.
Yet, despite such efforts by the vendor, a control valve person might have questions about global sourcing and the nation of origin. This article discusses how one main management valve vendor ensures product quality. Many other control valve vendors observe the same or related procedures.
Quality specification brings global assurance
Emerson enforces a comprehensive quality specification for its Fisher management valves that should be met by suppliers of pressure-containing and structural metallic castings. The high quality specification consists of 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 course of. The course of completely investigates a possible supplier’s capacity to satisfy material specs and applicable international codes and standards — in addition to particular necessities related to element manufacture. In the case of castings, a foundry is considered “qualified” when it passes a critical analysis by Fisher’s engineers.
The foundry should demonstrate a document of qualification by a third-party inspection company and conform to various standards, corresponding to ISO 9001:2000, ASME, A2LA, PED and others. It should cross a evaluate of its quality program in addition to on-site audits of the foundry’s processes and procedures corresponding to welding, warmth treatment and non-destructive examination. Additional proof of performance is determined by evaluation of tryout castings to verify specs are met.
Welding procedures — Welding is used during the production and upgrading of castings, such as 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 requirements. Similarly, each lot of weld filler should comply with ASME/AWS chemical evaluation specs. In Europe, compliance have to be to EN499. Weld filler will need to have actual chemistry.
Marking inspection and testing — Valve physique castings have markings (Figure 2) that identify the foundry that poured the casting and that indicate the warmth code. Material identification can also be sometimes shown on the physique casting, corresponding to CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct each visual inspections and mechanical tests on pressure-retaining castings.
As-cast external and inner surfaces are inspected visually for unacceptable irregularities, including hot 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 elements, together with the body and bonnet castings. The test procedure includes a fixture that closes off cavities that may be pressurized in service after which subjects the element to the hydrostatic shell take a look at stress appropriate for the valve physique material and sophistication.
ASME B16.34 sets out the hydrostatic test strain to use for steel and alloy valves. It’s calculated by multiplying the working strain by 1.5 and rounding to the subsequent larger 25 psig increment. Any visually detectable weeping or leaking via the stress boundary walls which are part of the valve meeting is a compulsory cause for rejection (Figure 3).
Compliance with these specifications must be ensured, in addition to with different necessities concerning materials.
Figure 2. Markings determine the foundry and supplies of the valve physique. These control valve our bodies were forged at an Emerson-approved foundry in China.
Meeting material requirements
Valve casting integrity and quality begins with specifications that call not just for premium supplies, but also for the supplies that work finest within the meant purposes. These utility requirements embrace energy and ductility in addition to resistance to certain factors, together with the make-up of the controlled fluid, operating temperature and move velocity.
For instance, chemical composition must be managed exactly to realize an alloy’s intended performance level. Carbon steel castings for valves supposed to be used in oil and gasoline functions should meet NACE SP0472 recommendations that chemical composition be controlled to lower than zero.43% carbon equivalency. The lower carbon content improves weldability and reduces the potential for stress cracking by hydrogen sulfide typically found in oil and fuel production and processing applications.
Another example of materials tied to a particular application embody these for upstream oil and gas production. Many of these functions occur in the arctic regions of Russia and Canada. For this service, castings are ASME SA 352 Grade LCC, while forgings should meet ASME SA 350 Grade LF2.
Many merchandise with world use now comply with twin materials specs to meet ASME and European requirements. For instance, metal castings are specified and licensed to each ASME SA216 Grade WCC and EN 10213 Grade 1.0619. เกจวัดไนโตรเจนราคา adds its personal stringent requirements such as the heat treating of high nickel alloys, extra demanding chemical composition or particular welding procedures.
In the past, Emerson has supplemented conventional ASTM and ASME specifications to achieve the improved corrosion-resistance levels and excessive temperature capabilities provided by high-nickel alloys. This is now accomplished by the brand new ASTM specification A990, which addresses each material composition and high quality.
Figure 3. Pressure-retaining components of a valve are subjected to hydrostatic testing to judge the parts’ integrity. Visible leakage or seepage via a casting means automatic 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 tool. ASTM A990 Class C requires radiography of the first casting of every sample. The acceptance criterion is Level three for categories A, B and C. For categories D through G, no cracking, scorching tears or inserts are allowed as specified in ASTM A990.
High-nickel alloy castings present improved efficiency in corrosive services and elevated temperatures. However, if high-nickel castings are improperly prepared, they will pose major problems, including poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification process can be adopted to avoid these casting difficulties.
The foundry must cast a 1-inch thick high-nickel test plate (Figure 4) that meets ASTM Material Specification A990. It’s tough to cast due to the difference 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 full of an identical composition weld materials. เพรสเชอร์เกจไฮดรอลิค and procedure for this step must 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 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 fulfill quality standards will outcome within the disqualification of the foundry from additional 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 equipment can range considerably. Once the dedicated pattern tools for every 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 disclose any inherent casting defects — corresponding to shrinkage — that have to be eradicated by modifying the pattern rigging.
Figure four. In a foundry analysis, 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 more than a decade. After an exploratory visit by procurement and manufacturing specialists, adopted by an in depth qualification process, the foundry was permitted 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 applied worldwide standards 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 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 specifications for casting valve bodies.
Summary
Control valve customers can be concerned when they study certain valve components usually are not made in the U.S. or Europe, however elsewhere. Perhaps their concern stems from expertise with other inferior products, such as appliances, garments or electronics made in those nations and bought online. 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 provider, then users may be assured the valves meet all specifications.
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