Across many forms of products in a variety of industries, the practice of mixing assorted elements from various assets all over the world is the rule, not the exception. Should this be a concern for a management valve user? For instance, when an end consumer discovers that a quantity of parts are being made in China (Figure 1), ought to the user worry concerning the quality?
When coping with a major valve vendor, the answer is “no.” There shouldn’t be any room for doubt when the seller has multiple checks and balances in place specializing in product high quality to ensure control valves operate as designed, want minimal maintenance, perform safely and function within environmental regulations.
Yet, regardless of such efforts by the seller, a control valve person may have questions about international sourcing and the country of origin. This article discusses how one main control valve vendor ensures product quality. Many different management valve vendors follow the same or related procedures.
Quality specification brings global assurance
Emerson enforces a complete high quality specification for its Fisher control valves that have to be met by suppliers of pressure-containing and structural metal castings. The high quality specification includes greater than a dozen necessities that apply to the following areas:
Marking inspection and testing
Tryout and sample castings
Certification of compliance
Supplier qualification — Suppliers endure a rigorous qualification process. The process completely investigates a possible supplier’s capacity to satisfy materials specifications and applicable worldwide codes and standards — as well as particular requirements related to element manufacture. In the case of castings, a foundry is considered “qualified” when it passes a critical evaluation by Fisher’s engineers.
The foundry must demonstrate a report of qualification by a third-party inspection agency and conform to various standards, such as ISO 9001:2000, ASME, A2LA, PED and others. It should cross a review of its quality program as well as on-site audits of the foundry’s processes and procedures such as welding, warmth therapy and non-destructive examination. Additional proof of efficiency is decided by evaluation of tryout castings to confirm specifications 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 requirements. Similarly, each lot of weld filler should comply with ASME/AWS chemical evaluation specifications. In Europe, compliance must be to EN499. Weld filler must have actual 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 typically shown on the body casting, similar to CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct each visible inspections and mechanical tests on pressure-retaining castings.
As-cast exterior and internal surfaces are inspected visually for unacceptable irregularities, together with sizzling tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing entails a hydrostatic strain test to verify the leak tightness of a management 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 and then subjects the element to the hydrostatic shell take a look at stress acceptable for the valve body materials and sophistication.
ASME B16.34 sets out the hydrostatic test stress to make use of for metal and alloy valves. It’s calculated by multiplying the working stress by 1.5 and rounding to the subsequent greater 25 psig increment. diaphragm seal or leaking by way of the stress boundary walls which are a part of the valve assembly is a compulsory trigger for rejection (Figure 3).
Compliance with these specs have to be ensured, as well as with other necessities regarding supplies.
Figure 2. Markings determine the foundry and supplies of the valve body. These control valve bodies had been forged at an Emerson-approved foundry in China.
Meeting materials necessities
Valve casting integrity and high quality begins with specs that call not just for premium supplies, but additionally for the materials that work greatest in the intended functions. These software necessities embody energy and ductility in addition to resistance to certain components, together with the make-up of the controlled fluid, operating temperature and circulate velocity.
For occasion, chemical composition must be controlled exactly to achieve an alloy’s intended efficiency level. Carbon metal castings for valves meant to be used in oil and gas purposes should meet NACE SP0472 suggestions that chemical composition be controlled to lower than zero.43% carbon equivalency. The decrease carbon content material improves weldability and reduces the potential for stress cracking by hydrogen sulfide sometimes present in oil and gas production and processing functions.
Another instance of supplies tied to a particular utility embrace those for upstream oil and fuel production. Many of those applications happen in 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 meet 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 often adds its personal stringent requirements similar to the warmth treating of excessive nickel alloys, more demanding chemical composition or special welding procedures.
In the past, Emerson has supplemented conventional ASTM and ASME specifications to realize the improved corrosion-resistance ranges and excessive temperature capabilities supplied by high-nickel alloys. This is now completed by the brand new ASTM specification A990, which addresses both materials composition and high quality.
Figure three. Pressure-retaining elements 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 part of a prospective foundry’s qualification, Emerson inspects and exams Fisher valve castings. Non-destructive testing radiography is used as a monitoring tool. ASTM A990 Class C requires radiography of the primary casting of every pattern. The acceptance criterion is Level three for categories A, B and C. For categories D through G, no cracking, sizzling tears or inserts are allowed as specified in ASTM A990.
High-nickel alloy castings present improved performance in corrosive companies and elevated temperatures. However, if high-nickel castings are improperly prepared, they can pose major problems, including 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 solid a 1-inch thick high-nickel test plate (Figure 4) that meets ASTM Material Specification A990. It’s troublesome to solid due to 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 a matching 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 closely for cracking alongside the weld heat-affected zone, casting grain boundaries or dendrite boundaries. Failure to meet high quality requirements will end result in the disqualification of the foundry from additional consideration. Casting patterns should be dedicated solely to high-nickel alloy service. Use of carbon steel or a stainless-steel sample is unacceptable as a result of differences in solidification properties.
Shrinkage rates for gates, risers and other accessories can differ significantly. Once the dedicated sample equipment for each of these components has been secured, try-out castings are poured for each pattern-alloy mixture. The castings are then radiographed.
The intent is to disclose any inherent casting defects — such as shrinkage — that need 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 qualified foundry
Emerson has used a Chinese foundry (Figure 5) to cast Fisher valve our bodies for more than a decade. After an exploratory visit by procurement and manufacturing specialists, adopted by an extensive qualification process, the foundry was approved and has been delivering high-quality valve physique and bonnet castings to Fisher valve manufacturing websites.
To assist ensure the standard of the castings it produces, the Chinese foundry has applied worldwide standards and has obtained certifications for German TUV and CE, Norway DNV, German Lloyd’s and American ABS, and has handed worldwide 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 received an Excellent Supplier award from Emerson.
Figure 5. This Chinese foundry meets all specifications for casting valve bodies.
Control valve customers could be involved once they learn sure valve elements are not made in the united states or Europe, however elsewhere. Perhaps their concern stems from expertise with different inferior merchandise, corresponding to home equipment, clothes or electronics made in those countries and offered online. But if the valve components are being equipped to a significant management valve vendor that has gone to nice lengths to qualify the foundry or supplier, then users could be assured the valves meet all specs.
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