Across many forms of merchandise in a wide range of industries, the practice of mixing assorted components from numerous resources all over the world is the rule, not the exception. Should this be a priority for a management valve user? For instance, when an finish user discovers that a quantity of elements are being made in China (Figure 1), should the person 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 focusing on product high quality to make sure control valves operate as designed, want minimal upkeep, perform safely and operate inside environmental rules.
Yet, despite such efforts by the vendor, a control valve consumer could have questions on international sourcing and the nation of origin. This article discusses how one main control valve vendor ensures product quality. Many different control valve vendors comply with the same or comparable procedures.
Quality specification brings international assurance
Emerson enforces a comprehensive high quality specification for its Fisher control valves that must be met by suppliers of pressure-containing and structural metal castings. The quality specification consists of greater than a dozen necessities that apply to the following areas:
Supplier qualification
Welding procedures
Marking inspection and testing
Tryout and pattern castings
Production castings
Certification of compliance
Supplier qualification — Suppliers endure a rigorous qualification process. The process completely investigates a potential supplier’s ability to meet material specs and relevant international codes and standards — in addition to specific necessities related to part manufacture. In the case of castings, a foundry is considered “qualified” when it passes a crucial evaluation by Fisher’s engineers.
The foundry should demonstrate a document of qualification by a third-party inspection agency and conform to varied requirements, corresponding to ISO 9001:2000, ASME, A2LA, PED and others. It should cross a review of its high quality program in addition to on-site audits of the foundry’s processes and procedures such as welding, warmth treatment and non-destructive examination. Additional proof of performance is set by analysis of tryout castings to verify specifications 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 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 adjust to ASME/AWS chemical analysis specifications. In Europe, compliance must be to EN499. pressure gauge หน้าปัด 4 นิ้ว will have to have precise chemistry.
Marking inspection and testing — Valve physique 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 shown on the physique casting, corresponding to CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct both visual inspections and mechanical tests on pressure-retaining castings.
As-cast external and internal surfaces are inspected visually for unacceptable irregularities, including scorching tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing involves a hydrostatic stress check to substantiate the leak tightness of a management valve’s pressure-retaining elements, including the physique and bonnet castings. The test procedure includes a fixture that closes off cavities that may be pressurized in service and then topics the element to the hydrostatic shell check stress appropriate for the valve body materials and sophistication.
ASME B16.34 units out the hydrostatic test strain to use for metal and alloy valves. It’s calculated by multiplying the working strain by 1.5 and rounding to the following larger 25 psig increment. Any visually detectable weeping or leaking via the stress boundary walls which might be part of the valve meeting is a compulsory trigger for rejection (Figure 3).
Compliance with these specifications have to be ensured, as well as with different necessities relating to materials.
Figure 2. Markings identify the foundry and supplies of the valve body. These control valve bodies were solid at an Emerson-approved foundry in China.
Meeting materials requirements
Valve casting integrity and quality begins with specifications that call not just for premium supplies, but also for the supplies that work greatest within the supposed functions. These utility necessities embody energy and ductility as nicely as resistance to certain elements, including the makeup of the managed fluid, operating temperature and move velocity.
For instance, chemical composition have to be managed exactly to achieve an alloy’s supposed efficiency degree. Carbon metal castings for valves supposed for use in oil and gasoline applications must meet NACE SP0472 recommendations that chemical composition be managed to less than zero.43% carbon equivalency. The decrease carbon content material improves weldability and reduces the potential for stress cracking by hydrogen sulfide typically present in oil and gasoline production and processing functions.
Another example of materials tied to a specific application embody these for upstream oil and fuel manufacturing. Many of those functions 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 global use now comply with twin materials specifications to meet ASME and European requirements. For instance, steel castings are specified and certified to both ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson typically adds its personal stringent requirements similar to the warmth treating of excessive nickel alloys, extra demanding chemical composition or special welding procedures.
In the past, Emerson has supplemented standard ASTM and ASME specifications to attain the improved corrosion-resistance levels and high temperature capabilities offered by high-nickel alloys. This is now completed by the new ASTM specification A990, which addresses both 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 by way of a casting means automated rejection.
Qualifying a foundry
As a part of a prospective foundry’s qualification, Emerson inspects and checks 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 classes D through G, no cracking, scorching 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 ready, they can pose major issues, together with poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification course of can be adopted to keep away from these casting difficulties.
The foundry should cast a 1-inch thick high-nickel take a look at 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 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 should 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 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 in the disqualification of the foundry from additional consideration. Casting patterns must be dedicated solely to high-nickel alloy service. Use of carbon metal or a stainless-steel sample is unacceptable due to differences in solidification properties.
Shrinkage charges for gates, risers and different accessories can range significantly. Once the dedicated sample gear for each of these components has been secured, try-out castings are poured for every pattern-alloy combination. The castings are then radiographed.
The intent is to disclose any inherent casting defects — similar to shrinkage — that need to be eradicated by modifying the pattern rigging.
Figure four. In a foundry evaluation, 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 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 physique and bonnet castings to Fisher valve manufacturing sites.
To assist ensure the quality of the castings it produces, the Chinese foundry has implemented international standards and has obtained certifications for German TUV and CE, Norway DNV, German Lloyd’s and American ABS, and has passed international high 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 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 once they study certain valve elements aren’t made in the us or Europe, but elsewhere. Perhaps their concern stems from expertise with different inferior products, such as home equipment, garments or electronics made in these countries and bought on-line. But if the valve parts are being equipped to a significant management valve vendor that has gone to nice lengths to qualify the foundry or provider, then users could be assured the valves meet all specs.
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