Valve sourcing goes world

Across many types of products in a wide range of industries, the apply of mixing assorted elements from varied resources around the world is the rule, not the exception. Should this be a concern for a control valve user? For example, when an end user discovers that several components are being made in China (Figure 1), should the consumer worry in regards to the quality?
When dealing with a serious valve vendor, the reply is “no.” There shouldn’t be any room for doubt when the seller has multiple checks and balances in place specializing in product quality to ensure management valves function as designed, want minimal upkeep, perform safely and operate inside environmental laws.
Yet, regardless of such efforts by the vendor, a control valve consumer might have questions about international sourcing and the nation of origin. This article discusses how one main management valve vendor ensures product quality. Many other control valve vendors comply with the identical or related procedures.
Quality specification brings international assurance
Emerson enforces a complete high quality specification for its Fisher management valves that have to be met by suppliers of pressure-containing and structural metallic castings. The quality specification consists of 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 totally investigates a possible supplier’s ability to satisfy materials specifications and relevant worldwide codes and standards — as well as specific requirements associated to part manufacture. In the case of castings, a foundry is taken into account “qualified” when it passes a crucial evaluation by Fisher’s engineers.
The foundry must reveal a record 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 evaluation of its quality program in addition to on-site audits of the foundry’s processes and procedures corresponding to welding, heat therapy 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 in the course of the production and upgrading of castings, such as 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 must comply with ASME/AWS chemical analysis specs. In Europe, compliance have to be to EN499. Weld filler must have precise chemistry.
Marking inspection and testing — Valve physique castings have markings (Figure 2) that determine the foundry that poured the casting and that indicate the heat code. Material identification can be sometimes proven on the body 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 inside surfaces are inspected visually for unacceptable irregularities, including sizzling tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing involves a hydrostatic stress check to confirm the leak tightness of a control valve’s pressure-retaining parts, including the physique and bonnet castings. The test procedure involves a fixture that closes off cavities that would be pressurized in service after which topics the element to the hydrostatic shell check pressure acceptable for the valve body material and sophistication.
ASME B16.34 sets out the hydrostatic test pressure to make use of for metal and alloy valves. It’s calculated by multiplying the working pressure by 1.5 and rounding to the following higher 25 psig increment. Any visually detectable weeping or leaking through the strain boundary walls which may be part of the valve assembly is a compulsory trigger for rejection (Figure 3).
Compliance with these specifications must be ensured, in addition to with different necessities relating to materials.
Figure 2. Markings establish the foundry and supplies of the valve physique. These control valve our bodies had been solid at an Emerson-approved foundry in China.
Meeting material requirements
Valve casting integrity and high quality begins with specifications that decision not just for premium materials, but also for the supplies that work best in the meant functions. These application necessities include power and ductility in addition to resistance to sure factors, together with the make-up of the controlled fluid, working temperature and move velocity.
For instance, chemical composition should be managed precisely to attain an alloy’s meant efficiency degree. Carbon steel castings for valves intended for use in oil and gas purposes should meet NACE SP0472 recommendations that chemical composition be managed to lower 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 manufacturing and processing applications.
Another example of supplies tied to a selected software include those for upstream oil and gasoline manufacturing. Many of those applications occur in the arctic regions 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 world use now comply with twin materials specifications to satisfy ASME and European requirements. For instance, metal castings are specified and certified to each ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson usually provides its personal stringent necessities corresponding to the heat treating of high nickel alloys, more demanding chemical composition or special welding procedures.
In the past, Emerson has supplemented standard ASTM and ASME specs to realize the enhanced corrosion-resistance levels and excessive temperature capabilities offered by high-nickel alloys. This is now accomplished by the new ASTM specification A990, which addresses each material composition and high quality.
Figure three. 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 potential foundry’s qualification, Emerson inspects and checks Fisher valve castings. Non-destructive testing radiography is used as a monitoring software. ASTM A990 Class C requires radiography of the first casting of each pattern. 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 services and elevated temperatures. However, if high-nickel castings are improperly prepared, they can pose main issues, including poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification process can be followed to keep away from these casting difficulties.
The foundry must forged a 1-inch thick high-nickel take a look at plate (Figure 4) that meets ASTM Material Specification A990. It’s difficult to forged 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 a matching composition weld material. The welder 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 cut 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 along the weld heat-affected zone, casting grain boundaries or dendrite boundaries. Failure to meet quality requirements will outcome in the disqualification of the foundry from further consideration. Casting patterns should be devoted 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 equipment can differ considerably. Once the devoted pattern tools for every of these components has been secured, try-out castings are poured for each pattern-alloy combination. เครื่องมือความดัน are then radiographed.
The intent is to reveal any inherent casting defects — such as shrinkage — that have to be eliminated by modifying the pattern rigging.
Figure four. In a foundry analysis, a casting is filled 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 intensive qualification course of, the foundry was approved and has been delivering high-quality valve body and bonnet castings to Fisher valve manufacturing sites.
To assist guarantee the quality of the castings it produces, the Chinese foundry has carried out worldwide standards and has obtained certifications for German TUV and CE, Norway DNV, German Lloyd’s and American ABS, and has passed 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 acquired an Excellent Supplier award from Emerson.
Figure 5. This Chinese foundry meets all specifications for casting valve bodies.
Control valve users may be concerned after they be taught sure valve elements are not made in the us or Europe, but elsewhere. Perhaps their concern stems from expertise with different inferior merchandise, similar to appliances, garments or electronics made in those nations and sold on-line. But if the valve elements are being equipped to a significant control valve vendor that has gone to great lengths to qualify the foundry or supplier, then customers can be assured the valves meet all specs.

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