Across many types of merchandise in quite so much of industries, the apply of combining assorted elements from various sources around the globe is the rule, not the exception. Should this be a concern for a management valve user? For example, when an end user discovers that several parts are being made in China (Figure 1), should the user worry about 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 a quantity of checks and balances in place focusing on product quality to make sure control valves function as designed, need minimal maintenance, carry out safely and operate within environmental rules.
Yet, despite such efforts by the vendor, a management valve user may have questions about global sourcing and the nation of origin. This article discusses how one major control valve vendor ensures product high quality. Many different control valve vendors follow the identical or similar procedures.
Quality specification brings international assurance
Emerson enforces a complete quality specification for its Fisher control valves that have to be met by suppliers of pressure-containing and structural steel castings. The quality specification consists of more 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 course of. The process thoroughly investigates a possible supplier’s capability to meet materials specs and applicable worldwide codes and standards — as nicely as particular requirements associated to element 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 company and conform to numerous standards, corresponding to ISO 9001:2000, ASME, A2LA, PED and others. It should move a evaluation of its high quality program as properly as on-site audits of the foundry’s processes and procedures such as welding, heat treatment and non-destructive examination. Additional proof of performance is determined by evaluation of tryout castings to verify specs are met.
Welding procedures — Welding is used in the course of the production and upgrading of castings, corresponding 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 must comply with ASME/AWS chemical evaluation specs. In Europe, compliance should be to EN499. Weld filler should have precise chemistry.
Marking inspection and testing — Valve body castings have markings (Figure 2) that determine the foundry that poured the casting and that point out the warmth code. Material identification is also typically shown on the physique casting, corresponding 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 inner surfaces are inspected visually for unacceptable irregularities, including sizzling tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing includes a hydrostatic strain test to confirm the leak tightness of a control valve’s pressure-retaining elements, together with the body and bonnet castings. The test procedure involves a fixture that closes off cavities that might be pressurized in service after which topics the element to the hydrostatic shell take a look at strain applicable for the valve physique material and sophistication.
ASME B16.34 units out the hydrostatic check stress to use for steel and alloy valves. It’s calculated by multiplying the working stress by 1.5 and rounding to the subsequent greater 25 psig increment. Any visually detectable weeping or leaking by way of the strain boundary walls which may be a part of the valve assembly is a mandatory trigger for rejection (Figure 3).
Compliance with these specifications have to be ensured, as nicely as with different requirements regarding supplies.
Figure 2. Markings determine the foundry and materials of the valve physique. These control valve bodies have been forged at an Emerson-approved foundry in China.
Meeting materials necessities
Valve casting integrity and quality begins with specs that decision not only for premium supplies, but in addition for the supplies that work greatest within the supposed functions. These utility requirements embody energy and ductility in addition to resistance to sure factors, together with the make-up of the controlled fluid, operating temperature and circulate velocity.
For เกจวัดแรงดันน้ำราคา , chemical composition must be controlled precisely to achieve an alloy’s meant efficiency level. Carbon steel castings for valves supposed to be used in oil and gasoline functions should meet NACE SP0472 recommendations 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 usually present in oil and gasoline production and processing purposes.
Another example of supplies tied to a specific software embrace those for upstream oil and gasoline manufacturing. Many of those applications occur within the arctic regions of Russia and Canada. For this service, castings are ASME SA 352 Grade LCC, whereas forgings should meet ASME SA 350 Grade LF2.
Many products with global use now comply with dual materials specifications to meet ASME and European standards. For example, metal castings are specified and authorized to both ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson often adds its own stringent necessities similar to the heat treating of high nickel alloys, extra demanding chemical composition or special welding procedures.
In the previous, Emerson has supplemented typical ASTM and ASME specifications to achieve the enhanced corrosion-resistance levels and high temperature capabilities provided by high-nickel alloys. This is now completed 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 judge the parts’ integrity. Visible leakage or seepage via a casting means automated rejection.
Qualifying a foundry
As part of a potential 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 classes D via G, no cracking, hot tears or inserts are allowed as laid out in ASTM A990.
High-nickel alloy castings provide improved efficiency in corrosive providers and elevated temperatures. However, if high-nickel castings are improperly prepared, they’ll pose major problems, together with 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 check plate (Figure 4) that meets ASTM Material Specification A990. It’s troublesome to forged because of the difference 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 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 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 satisfy quality standards will end result within 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 end result of variations in solidification properties.
Shrinkage rates for gates, risers and other accessories can differ significantly. Once the devoted pattern gear 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 have to be eliminated by modifying the sample rigging.
Figure four. In a foundry analysis, a casting is crammed 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 go to by procurement and manufacturing specialists, adopted 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 help guarantee the standard of the castings it produces, the Chinese foundry has implemented 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 thrice 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.
Summary
Control valve users could be concerned after they learn certain valve parts are not made in the united states or Europe, but elsewhere. Perhaps their concern stems from experience with other inferior products, corresponding to appliances, clothes or electronics made in those nations and bought online. But if the valve elements are being supplied to a serious management valve vendor that has gone to nice lengths to qualify the foundry or provider, then users can be assured the valves meet all specifications.
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