Across many types of merchandise in a wide range of industries, the apply of combining assorted elements from varied resources all over the world is the rule, not the exception. Should this be a concern for a management valve user? For example, when an finish user discovers that several elements are being made in China (Figure 1), ought to the consumer worry concerning the quality?
When coping with a serious valve vendor, the reply is “no.” There shouldn’t be any room for doubt when the vendor has a number of checks and balances in place focusing on product high quality to make sure control valves function as designed, want minimal maintenance, perform safely and operate within environmental laws.
Yet, regardless of such efforts by the vendor, a control valve user might 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 management valve vendors follow the same or similar procedures.
Quality specification brings global assurance
Emerson enforces a complete high quality specification for its Fisher control valves that should be met by suppliers of pressure-containing and structural steel castings. The quality specification includes more than a dozen necessities that apply to the next areas:
Supplier qualification
Welding procedures
Marking inspection and testing
Tryout and sample castings
Production castings
Certification of compliance
Supplier qualification — Suppliers undergo a rigorous qualification process. The course of completely investigates a potential supplier’s capability to fulfill material specifications and applicable worldwide codes and requirements — as nicely as specific requirements related to part manufacture. In the case of castings, a foundry is taken into account “qualified” when it passes a crucial analysis by Fisher’s engineers.
The foundry must show a document of qualification by a third-party inspection company and conform to numerous standards, corresponding to ISO 9001:2000, ASME, A2LA, PED and others. It must pass a evaluation of its quality program as properly as on-site audits of the foundry’s processes and procedures similar to welding, heat treatment and non-destructive examination. Additional proof of efficiency is set by analysis of tryout castings to verify specs are met.
Welding procedures — Welding is used through the manufacturing and upgrading of castings, corresponding to 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 analysis specs. In Europe, compliance have to be to EN499. Weld filler must have precise 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 also be sometimes proven on the physique casting, corresponding to CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct both visible inspections and mechanical tests on pressure-retaining castings.
As-cast external and internal surfaces are inspected visually for unacceptable irregularities, together with hot tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing entails a hydrostatic pressure take a look at to confirm the leak tightness of a management valve’s pressure-retaining elements, including the body and bonnet castings. The take a look at process includes a fixture that closes off cavities that may be pressurized in service and then topics the element to the hydrostatic shell test pressure applicable for the valve body materials and class.
ASME B16.34 units out the hydrostatic check strain to make use of for metal and alloy valves. It’s calculated by multiplying the working stress by 1.5 and rounding to the next larger 25 psig increment. Any visually detectable weeping or leaking through the pressure boundary partitions which are a part of the valve meeting is a compulsory trigger for rejection (Figure 3).
Compliance with these specifications have to be ensured, in addition to with different requirements relating to supplies.
Figure 2. Markings establish the foundry and supplies of the valve physique. These management valve our bodies were solid at an Emerson-approved foundry in China.
Meeting materials requirements
Valve casting integrity and high quality begins with specs that call not only for premium materials, but additionally for the supplies that work best in the supposed purposes. These application requirements embody power and ductility in addition to resistance to sure elements, including the makeup of the controlled fluid, operating temperature and move velocity.
For instance, chemical composition must be controlled exactly to realize an alloy’s meant performance degree. Carbon metal castings for valves meant for use in oil and gasoline applications must meet NACE SP0472 suggestions that chemical composition be controlled to lower than zero.43% carbon equivalency. The lower carbon content improves weldability and reduces the potential for stress cracking by hydrogen sulfide usually found in oil and gas manufacturing and processing purposes.
Another instance of supplies tied to a particular software embody these 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 must meet ASME SA 350 Grade LF2.
Many products with world use now comply with twin materials specifications to satisfy ASME and European requirements. For instance, steel castings are specified and licensed to each ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson typically adds its personal stringent requirements corresponding to the heat treating of high nickel alloys, extra demanding chemical composition or particular welding procedures.
In the past, Emerson has supplemented conventional ASTM and ASME specifications to achieve the enhanced corrosion-resistance ranges and high temperature capabilities supplied by high-nickel alloys. This is now achieved by the brand new ASTM specification A990, which addresses each material composition and quality.
Figure three. Pressure-retaining elements of a valve are subjected to hydrostatic testing to gauge the parts’ integrity. Visible leakage or seepage through a casting means automatic rejection.
Qualifying a foundry
As part of a prospective 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 primary casting of every pattern. The acceptance criterion is Level three for categories A, B and C. For classes D via G, no cracking, sizzling tears or inserts are allowed as laid out in ASTM A990.
High-nickel alloy castings provide improved performance in corrosive providers and elevated temperatures. However, if high-nickel castings are improperly ready, they can pose main issues, together with poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification process could be followed to keep away from 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 troublesome to forged due to 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 an identical composition weld material. 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 minimize 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 fulfill high quality standards will outcome in the disqualification of the foundry from additional consideration. Casting patterns have to be devoted solely to high-nickel alloy service. Use of carbon steel or a stainless-steel sample is unacceptable as a outcome of variations in solidification properties.
Shrinkage charges for gates, risers and other accessories can vary considerably. Once the dedicated sample equipment for every of these components has been secured, try-out castings are poured for every pattern-alloy mixture. The castings are then radiographed.
The intent is to disclose any inherent casting defects — corresponding to shrinkage — that need to be eliminated by modifying the sample rigging.
Figure 4. In a foundry analysis, a casting is full of weld filler, then sliced to yield a bar for bend testing.
A certified foundry
Emerson has used a Chinese foundry (Figure 5) to forged 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 permitted and has been delivering high-quality valve body and bonnet castings to Fisher valve manufacturing sites.
To assist guarantee the standard of the castings it produces, the Chinese foundry has applied international requirements 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 3 times consecutively in the Beijing International Casting, Forging and Industrial Boiler Expo. It has twice obtained an Excellent Supplier award from Emerson.
Figure 5. This Chinese foundry meets all specifications for casting valve bodies.
Summary
Control valve customers may be concerned after they be taught certain valve parts usually are not made in the U.S. or Europe, but elsewhere. Perhaps ราคาเกจวัดแรงดันน้ำ from experience with different inferior products, similar to home equipment, garments or electronics made in these nations and offered online. But if the valve elements are being provided to a significant 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