Across many forms of merchandise in quite lots of industries, the follow of combining assorted components from varied sources around the globe is the rule, not the exception. Should this be a priority for a control valve user? For instance, when an end user discovers that a quantity of parts are being made in China (Figure 1), ought to the consumer fear 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 operate as designed, need minimal upkeep, carry out safely and operate inside environmental rules.
Yet, despite such efforts by the vendor, a control valve person could have questions on world sourcing and the nation of origin. This article discusses how one major control valve vendor ensures product quality. Many other management valve distributors follow the identical or similar procedures.
Quality specification brings world assurance
Emerson enforces a comprehensive quality specification for its Fisher control valves that must be met by suppliers of pressure-containing and structural metal castings. The high 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 bear a rigorous qualification process. The course of thoroughly investigates a possible supplier’s capability to fulfill materials specifications and applicable worldwide codes and requirements — as well as particular requirements associated to element manufacture. In the case of castings, a foundry is taken into account “qualified” when it passes a important evaluation by Fisher’s engineers.
The foundry must show a record of qualification by a third-party inspection agency and conform to numerous requirements, similar to ISO 9001:2000, ASME, A2LA, PED and others. It must cross a evaluate of its quality program as well as on-site audits of the foundry’s processes and procedures corresponding to welding, warmth remedy and non-destructive examination. Additional proof of performance is determined by analysis of tryout castings to verify specs are met.
Welding procedures — Welding is used during the production and upgrading of castings, similar to when radiographic examination is required. Welding requirements state that procedures and welder qualifications must 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 should have actual chemistry.
Marking inspection and testing — Valve body castings have markings (Figure 2) that establish the foundry that poured the casting and that point out the warmth code. Material identification can be sometimes proven on the body casting, such as 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, together with hot tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing includes a hydrostatic pressure take a look at to substantiate the leak tightness of a management valve’s pressure-retaining elements, including the body and bonnet castings. The take a look at procedure includes a fixture that closes off cavities that may be pressurized in service after which topics the part to the hydrostatic shell check strain applicable for the valve physique materials and sophistication.
ASME B16.34 sets out the hydrostatic check pressure to use for metal and alloy valves. It’s calculated by multiplying the working pressure by 1.5 and rounding to the subsequent greater 25 psig increment. Any visually detectable weeping or leaking via the pressure boundary walls which would possibly be a part of the valve meeting is a compulsory trigger for rejection (Figure 3).
Compliance with these specs must be ensured, in addition to with other necessities concerning materials.
Figure 2. Markings identify the foundry and supplies of the valve body. These control valve bodies have been cast at an Emerson-approved foundry in China.
Meeting material requirements
Valve casting integrity and quality begins with specs that decision not just for premium materials, but additionally for the materials that work best in the supposed functions. These application requirements include energy and ductility as nicely as resistance to sure components, including the makeup of the controlled fluid, working temperature and flow velocity.
For occasion, chemical composition should be managed exactly to realize an alloy’s supposed performance degree. Carbon steel castings for valves meant for use in oil and fuel applications should meet NACE SP0472 suggestions that chemical composition be managed to less than zero.43% carbon equivalency. The decrease carbon content improves weldability and reduces the potential for stress cracking by hydrogen sulfide typically found in oil and gas manufacturing and processing purposes.
Another instance of supplies tied to a specific software include these for upstream oil and fuel production. Many of these purposes happen within the arctic areas of Russia and Canada. For this service, castings are ASME SA 352 Grade LCC, while forgings must meet ASME SA 350 Grade LF2.
Many merchandise with global use now comply with dual materials specs to meet ASME and European requirements. For instance, steel castings are specified and authorized to each ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson usually adds its own stringent necessities similar to the warmth treating of excessive nickel alloys, more demanding chemical composition or particular welding procedures.
In the past, Emerson has supplemented typical ASTM and ASME specs to realize the enhanced corrosion-resistance ranges 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 high quality.
Figure three. Pressure-retaining parts of a valve are subjected to hydrostatic testing to evaluate the parts’ integrity. Visible leakage or seepage through a casting means automated 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 software. ASTM A990 Class C requires radiography of the primary casting of every sample. The acceptance criterion is Level 3 for categories A, B and C. For categories D via G, no cracking, hot tears or inserts are allowed as specified in ASTM A990.
High-nickel alloy castings provide improved performance in corrosive companies and elevated temperatures. However, if high-nickel castings are improperly prepared, they’ll pose main problems, including poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification course of can be followed to avoid these casting difficulties.
The foundry should forged a 1-inch thick high-nickel test plate (Figure 4) that meets ASTM Material Specification A990. It’s tough to forged 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 filled with an identical composition weld materials. The welder and process for this step must meet the standards 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 carefully for cracking alongside the weld heat-affected zone, casting grain boundaries or dendrite boundaries. Failure to fulfill high quality requirements will end result within the disqualification of the foundry from further consideration. Casting patterns have to be dedicated solely to high-nickel alloy service. Use of pressure gauge ยี่ห้อ tk or a stainless-steel pattern is unacceptable as a end result of variations in solidification properties.
Shrinkage rates for gates, risers and different accessories can range considerably. Once the devoted sample gear for each of those elements 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 — corresponding to shrinkage — that have to be eliminated by modifying the sample rigging.
Figure 4. 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 bodies for more than a decade. After an exploratory go to by procurement and manufacturing specialists, followed by an intensive qualification course of, the foundry was accredited and has been delivering high-quality valve physique and bonnet castings to Fisher valve manufacturing sites.
To help guarantee the quality of the castings it produces, the Chinese foundry has carried out international standards and has obtained certifications for German TUV and CE, Norway DNV, German Lloyd’s and American ABS, and has handed international quality system certifications of ISO 9001 and QS -9000.
The foundry has been awarded Gold Medals thrice 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 our bodies.
Summary
Control valve customers can be involved once they study certain valve elements usually are not made in the us or Europe, but elsewhere. Perhaps their concern stems from expertise with other inferior products, corresponding to home equipment, clothes or electronics made in those countries and offered online. But if the valve components are being provided to a serious management 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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