Across many kinds of products in a wide range of industries, the practice of mixing assorted elements from varied 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 end user discovers that several components are being made in China (Figure 1), ought to the user worry about the quality?
When coping with a significant valve vendor, the reply 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 ensure control valves operate as designed, need minimal upkeep, carry out safely and function inside environmental regulations.
Yet, despite such efforts by the seller, a control valve person may have questions about global sourcing and the country of origin. This article discusses how one main control valve vendor ensures product high quality. เกจวัดแรงดันเครื่องกรองน้ำ observe the identical or comparable procedures.
Quality specification brings world assurance
Emerson enforces a complete quality specification for its Fisher management valves that should be met by suppliers of pressure-containing and structural steel castings. The high quality specification includes greater 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 undergo a rigorous qualification course of. The course of thoroughly investigates a potential supplier’s ability to fulfill material specifications and applicable international codes and standards — as nicely as specific requirements associated to part manufacture. In the case of castings, a foundry is taken into account “qualified” when it passes a critical analysis by Fisher’s engineers.
The foundry should reveal a report of qualification by a third-party inspection agency and conform to numerous standards, such as ISO 9001:2000, ASME, A2LA, PED and others. It must move a evaluate of its quality program as nicely as on-site audits of the foundry’s processes and procedures corresponding to welding, heat remedy and non-destructive examination. Additional proof of performance is decided by analysis of tryout castings to verify specs are met.
Welding procedures — Welding is used during the manufacturing and upgrading of castings, corresponding 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 standards. Similarly, every lot of weld filler should comply with ASME/AWS chemical evaluation specifications. In Europe, compliance must be to EN499. Weld filler must have precise chemistry.
Marking inspection and testing — Valve physique castings have markings (Figure 2) that identify the foundry that poured the casting and that indicate the heat code. Material identification is also sometimes proven on the body casting, such as CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct both visual inspections and mechanical checks on pressure-retaining castings.
As-cast exterior and inner surfaces are inspected visually for unacceptable irregularities, including scorching tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing includes a hydrostatic stress check to substantiate the leak tightness of a management valve’s pressure-retaining parts, together with the physique and bonnet castings. The test process involves a fixture that closes off cavities that may be pressurized in service after which topics the component to the hydrostatic shell check strain applicable for the valve body materials and sophistication.
ASME B16.34 sets out the hydrostatic test strain to make use of for metal and alloy valves. It’s calculated by multiplying the working stress by 1.5 and rounding to the next larger 25 psig increment. Any visually detectable weeping or leaking by way of the pressure boundary walls which are a part of the valve assembly is a mandatory cause for rejection (Figure 3).
Compliance with these specifications should be ensured, in addition to with different requirements concerning supplies.
Figure 2. Markings determine the foundry and materials of the valve physique. These management valve bodies were forged 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 materials, but additionally for the supplies that work best within the intended applications. These software necessities include strength and ductility as properly as resistance to certain elements, together with the makeup of the controlled fluid, operating temperature and move velocity.
For occasion, chemical composition should be managed exactly to realize an alloy’s supposed performance stage. Carbon steel castings for valves intended for use in oil and fuel functions must meet NACE SP0472 suggestions that chemical composition be managed to lower than 0.43% carbon equivalency. The lower carbon content improves weldability and reduces the potential for stress cracking by hydrogen sulfide sometimes present in oil and gas production and processing purposes.
Another example of supplies tied to a particular software embody those for upstream oil and gasoline manufacturing. Many of these purposes occur in the arctic areas of Russia and Canada. For this service, castings are ASME SA 352 Grade LCC, whereas forgings must meet ASME SA 350 Grade LF2.
Many merchandise with global use now adjust to twin material specs to fulfill ASME and European requirements. For example, steel castings are specified and authorized to both ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson usually provides its personal stringent requirements similar to 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 specifications to achieve the improved corrosion-resistance levels and high temperature capabilities provided by high-nickel alloys. This is now completed by the new ASTM specification A990, which addresses both materials composition and high quality.
Figure 3. Pressure-retaining components of a valve are subjected to hydrostatic testing to gauge the parts’ integrity. Visible leakage or seepage by way of a casting means automated 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 software. ASTM A990 Class C requires radiography of the primary casting of each sample. The acceptance criterion is Level 3 for categories A, B and C. For categories D by way of G, no cracking, scorching tears or inserts are allowed as laid out in ASTM A990.
High-nickel alloy castings present improved performance in corrosive services and elevated temperatures. However, if high-nickel castings are improperly ready, they can pose major issues, 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 cast a 1-inch thick high-nickel take a look at plate (Figure 4) that meets ASTM Material Specification A990. It’s difficult to solid because of 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 crammed with an identical composition weld materials. The welder and process 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 reduce from the plate and bent over a 1½-inch mandrel per ASTM A990 right 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 fulfill quality standards will outcome within the disqualification of the foundry from further consideration. Casting patterns have to be dedicated solely to high-nickel alloy service. Use of carbon metal or a stainless-steel sample is unacceptable due to variations in solidification properties.
Shrinkage rates for gates, risers and different equipment can range significantly. Once the devoted pattern tools for each of these parts has been secured, try-out castings are poured for every pattern-alloy combination. The castings are then radiographed.
The intent is to reveal any inherent casting defects — similar to shrinkage — that must be eradicated by modifying the pattern rigging.
Figure 4. In a foundry evaluation, 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 cast Fisher valve bodies for more than a decade. After an exploratory go to by procurement and manufacturing specialists, adopted by an extensive qualification process, the foundry was accredited and has been delivering high-quality valve physique and bonnet castings to Fisher valve manufacturing websites.
To assist guarantee the standard of the castings it produces, the Chinese foundry has implemented international standards and has obtained certifications for German TUV and CE, Norway DNV, German Lloyd’s and American ABS, and has handed international high quality system certifications of ISO 9001 and QS -9000.
The foundry has been awarded Gold Medals thrice consecutively in the Beijing International Casting, Forging and Industrial Boiler Expo. It has twice acquired an Excellent Supplier award from Emerson.
Figure 5. This Chinese foundry meets all specs for casting valve our bodies.
Summary
Control valve customers could be involved after they be taught certain valve elements usually are not made in the U.S. or Europe, but elsewhere. Perhaps their concern stems from experience with other inferior merchandise, similar to appliances, garments or electronics made in those countries and offered online. But if the valve elements 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 specifications.
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