Valve sourcing goes international

Across many forms of products in quite lots of industries, the apply of combining assorted parts from numerous assets around the world is the rule, not the exception. Should this be a priority for a control valve user? For instance, when an finish person discovers that several elements are being made in China (Figure 1), ought to the person worry concerning 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 a quantity of checks and balances in place focusing on product high quality to ensure management valves operate as designed, need minimal maintenance, perform safely and operate inside environmental regulations.
Yet, despite such efforts by the vendor, a control valve consumer may have questions about global sourcing and the nation of origin. This article discusses how one major management valve vendor ensures product high quality. Many different management valve vendors comply with the same or similar procedures.
Quality specification brings global assurance
Emerson enforces a comprehensive quality specification for its Fisher control valves that have to be met by suppliers of pressure-containing and structural metallic castings. The high quality specification includes greater than a dozen requirements 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 bear a rigorous qualification process. The process thoroughly investigates a possible supplier’s capacity to satisfy materials specs and applicable worldwide codes and requirements — as well as particular 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 varied requirements, corresponding to ISO 9001:2000, ASME, A2LA, PED and others. It must move a review of its high quality program as properly 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 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 standards. Similarly, every lot of weld filler must adjust to ASME/AWS chemical analysis specs. In Europe, compliance must be to EN499. Weld filler will need to have actual chemistry.
Marking inspection and testing — Valve body castings have markings (Figure 2) that identify the foundry that poured the casting and that point out the warmth code. Material identification can be typically shown on the physique casting, such as CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct each visual inspections and mechanical exams on pressure-retaining castings.
As-cast exterior and internal surfaces are inspected visually for unacceptable irregularities, including sizzling tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing involves a hydrostatic pressure take a look at to confirm the leak tightness of a control valve’s pressure-retaining components, including the body and bonnet castings. The take a look at procedure involves a fixture that closes off cavities that may be pressurized in service after which topics the component to the hydrostatic shell check stress applicable for the valve body material and sophistication.
ASME B16.34 units out the hydrostatic test pressure to use for metal and alloy valves. It’s calculated by multiplying the working strain by 1.5 and rounding to the next higher 25 psig increment. Any visually detectable weeping or leaking by way of the pressure boundary walls that are part of the valve meeting is a compulsory trigger for rejection (Figure 3).
Compliance with these specs must be ensured, as nicely as with other necessities relating to materials.
Figure 2. Markings identify the foundry and supplies of the valve physique. These management valve bodies were forged at an Emerson-approved foundry in China.
Meeting material necessities
Valve casting integrity and quality begins with specifications that decision not only for premium supplies, but additionally for the supplies that work best in the intended purposes. These utility necessities include strength and ductility as nicely as resistance to certain factors, including 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 efficiency stage. Carbon steel castings for valves supposed for use in oil and gas purposes should meet NACE SP0472 recommendations that chemical composition be managed 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 gas manufacturing and processing applications.
Another instance of supplies tied to a selected application embody those for upstream oil and gasoline production. Many of those purposes occur within the arctic areas 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 global use now adjust to dual materials specs to satisfy ASME and European standards. For example, steel castings are specified and certified to each ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson often provides its own stringent necessities such as the warmth treating of excessive nickel alloys, extra demanding chemical composition or particular welding procedures.
In the previous, Emerson has supplemented standard ASTM and ASME specifications to realize the improved corrosion-resistance levels and high temperature capabilities offered by high-nickel alloys. This is now achieved by the model new ASTM specification A990, which addresses each materials composition and quality.
Figure three. Pressure-retaining elements of a valve are subjected to hydrostatic testing to judge the parts’ integrity. Visible leakage or seepage through a casting means computerized rejection.
Qualifying a foundry
As part of a prospective foundry’s qualification, Emerson inspects and tests Fisher valve castings. Non-destructive testing radiography is used as a monitoring tool. ASTM A990 Class C requires radiography of the primary casting of each pattern. The acceptance criterion is Level three for classes A, B and C. For categories D through G, no cracking, hot tears or inserts are allowed as specified in ASTM A990.
High-nickel alloy castings provide improved efficiency in corrosive services and elevated temperatures. However, if high-nickel castings are improperly ready, they will pose major issues, together with poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification course of may be adopted to avoid 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 cast 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 full of a matching 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 cut 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 meet high quality requirements will result within the disqualification of the foundry from additional consideration. Casting patterns must be devoted solely to high-nickel alloy service. Use of carbon metal or a stainless-steel sample is unacceptable because of variations in solidification properties.
Shrinkage charges for gates, risers and other equipment can vary significantly. Once the devoted pattern gear for each of these parts has been secured, try-out castings are poured for every pattern-alloy mixture. 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 four. In a foundry analysis, a casting is crammed with weld filler, then sliced to yield a bar for bend testing.
A certified foundry
Emerson has used a Chinese foundry (Figure 5) to solid Fisher valve bodies for more than a decade. After an exploratory visit by procurement and manufacturing specialists, adopted by an extensive qualification course of, the foundry was accredited and has been delivering high-quality valve physique and bonnet castings to Fisher valve manufacturing sites.
To assist ensure 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 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. เครื่องมือความดัน has twice acquired an Excellent Supplier award from Emerson.
Figure 5. This Chinese foundry meets all specs for casting valve bodies.
Summary
Control valve customers can be concerned when they learn certain valve parts are not made in the united states or Europe, however elsewhere. Perhaps their concern stems from experience with different inferior products, similar to appliances, garments or electronics made in these nations and offered online. But if the valve parts are being provided to a serious management valve vendor that has gone to great lengths to qualify the foundry or supplier, then customers could be assured the valves meet all specifications.
Share

Scroll to Top