Across many types of merchandise in a variety of industries, the practice of combining assorted parts from numerous sources all over the world is the rule, not the exception. Should เกจวัดแรงดันถังแก๊ส be a concern for a control valve user? For instance, when an finish person discovers that a number of components are being made in China (Figure 1), should the person fear in regards to the quality?
When dealing with a serious valve vendor, the answer is “no.” There shouldn’t be any room for doubt when the vendor has multiple checks and balances in place specializing in product high quality to make sure management valves function as designed, need minimal upkeep, perform safely and operate inside environmental regulations.
Yet, regardless of such efforts by the vendor, a management valve person may have questions about international 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 identical or similar procedures.
Quality specification brings international assurance
Emerson enforces a comprehensive high quality specification for its Fisher control valves that must be met by suppliers of pressure-containing and structural metal castings. The quality specification includes greater 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 undergo a rigorous qualification course of. The process completely investigates a possible supplier’s capacity to satisfy material specifications and applicable worldwide codes and requirements — in addition to particular requirements related to component manufacture. In the case of castings, a foundry is considered “qualified” when it passes a crucial evaluation by Fisher’s engineers.
The foundry should show a record of qualification by a third-party inspection company and conform to numerous requirements, similar to ISO 9001:2000, ASME, A2LA, PED and others. It should pass a evaluation of its high quality program in addition to on-site audits of the foundry’s processes and procedures similar to welding, heat therapy and non-destructive examination. Additional proof of performance is determined by evaluation of tryout castings to verify specifications are met.
Welding procedures — Welding is used through 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 standards. Similarly, each lot of weld filler should adjust to ASME/AWS chemical analysis specs. In Europe, compliance have to be to EN499. Weld filler must have actual chemistry.
Marking inspection and testing — Valve physique castings have markings (Figure 2) that determine the foundry that poured the casting and that point out the heat code. Material identification is also typically shown on the physique casting, similar to CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct both visual inspections and mechanical tests on pressure-retaining castings.
As-cast external and inside 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 test to substantiate the leak tightness of a control valve’s pressure-retaining parts, together with the physique and bonnet castings. The test procedure includes a fixture that closes off cavities that would be pressurized in service after which subjects the element to the hydrostatic shell test stress applicable for the valve body material and sophistication.
ASME B16.34 sets out the hydrostatic check strain to use for steel and alloy valves. It’s calculated by multiplying the working pressure by 1.5 and rounding to the next larger 25 psig increment. Any visually detectable weeping or leaking through the stress boundary partitions which might be a half of the valve assembly is a compulsory cause for rejection (Figure 3).
Compliance with these specs should be ensured, in addition to with other requirements concerning supplies.
Figure 2. Markings identify the foundry and materials of the valve physique. These management valve bodies were solid at an Emerson-approved foundry in China.
Meeting materials requirements
Valve casting integrity and quality begins with specifications that decision not just for premium materials, but additionally for the materials that work finest within the intended functions. These software requirements include energy and ductility as well as resistance to sure factors, including the makeup of the controlled fluid, working temperature and flow velocity.
For instance, chemical composition have to be controlled precisely to attain an alloy’s supposed performance level. Carbon steel castings for valves meant to be used in oil and gas applications should meet NACE SP0472 suggestions 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 sometimes found in oil and gasoline production and processing functions.
Another instance of supplies tied to a selected utility embody those for upstream oil and gas manufacturing. Many of these functions happen within the arctic regions of Russia and Canada. For this service, castings are ASME SA 352 Grade LCC, while forgings must meet ASME SA 350 Grade LF2.
Many products with international use now adjust to twin materials specifications to satisfy ASME and European standards. For example, steel castings are specified and licensed to both ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson usually adds its personal stringent necessities such as the heat 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 levels and excessive temperature capabilities offered by high-nickel alloys. This is now accomplished by the model new ASTM specification A990, which addresses each materials composition and quality.
Figure three. Pressure-retaining components of a valve are subjected to hydrostatic testing to judge the parts’ integrity. Visible leakage or seepage by way of a casting means automatic rejection.
Qualifying a foundry
As a half 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 every sample. The acceptance criterion is Level three for categories A, B and C. For classes D via 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 prepared, they’ll pose main problems, together with poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification course of may be followed to keep away from these casting difficulties.
The foundry must solid a 1-inch thick high-nickel take a look at plate (Figure 4) that meets ASTM Material Specification A990. It’s troublesome 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 full of an identical 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 into a U-shape.
The bars are examined intently for cracking alongside the weld heat-affected zone, casting grain boundaries or dendrite boundaries. Failure to satisfy high quality requirements will outcome within the disqualification of the foundry from further consideration. Casting patterns must be devoted solely to high-nickel alloy service. Use of carbon metal or a stainless-steel pattern is unacceptable as a result of variations in solidification properties.
Shrinkage charges for gates, risers and different accessories can range considerably. Once the devoted sample tools for every of these components 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 analysis, a casting is filled 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 bodies for more than a decade. After an exploratory visit by procurement and manufacturing specialists, adopted by an in depth qualification course of, the foundry was permitted and has been delivering high-quality valve body and bonnet castings to Fisher valve manufacturing websites.
To assist ensure the quality of the castings it produces, the Chinese foundry has implemented worldwide standards and has obtained certifications for German TUV and CE, Norway DNV, German Lloyd’s and American ABS, and has passed worldwide quality system certifications of ISO 9001 and QS -9000.
The foundry has been awarded Gold Medals 3 times consecutively in 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 specifications for casting valve bodies.
Summary
Control valve customers may be involved after they be taught certain valve parts aren’t made in the U.S. or Europe, however elsewhere. Perhaps their concern stems from experience with different inferior merchandise, similar to home equipment, clothes or electronics made in those countries and sold on-line. But if the valve elements are being equipped to a major control valve vendor that has gone to great lengths to qualify the foundry or provider, then users could be assured the valves meet all specs.
Share