Across many kinds of products in a variety of industries, the follow of combining assorted parts from varied assets around the globe is the rule, not the exception. Should this be a concern for a control valve user? For instance, when an finish user discovers that a number of parts are being made in China (Figure 1), ought to the consumer 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 make sure control valves operate as designed, want minimal maintenance, perform safely and function inside environmental regulations.
Yet, regardless of such efforts by the vendor, a control valve consumer might have questions about world sourcing and the country of origin. This article discusses how one major control valve vendor ensures product quality. Many different management valve distributors observe the same or comparable procedures.
Quality specification brings world assurance
Emerson enforces a comprehensive quality specification for its Fisher management valves that must be met by suppliers of pressure-containing and structural steel castings. The high quality specification contains more than a dozen necessities that apply to the following areas:
Marking inspection and testing
Tryout and pattern castings
Certification of compliance
Supplier qualification — Suppliers bear a rigorous qualification process. The course of completely investigates a potential supplier’s capability to meet materials specs and applicable worldwide codes and standards — in addition to particular requirements associated to part manufacture. In the case of castings, a foundry is considered “qualified” when it passes a critical analysis by Fisher’s engineers.
The foundry should reveal a document of qualification by a third-party inspection company and conform to numerous requirements, similar to ISO 9001:2000, ASME, A2LA, PED and others. It should move a review of its quality program in addition to on-site audits of the foundry’s processes and procedures similar to welding, warmth therapy and non-destructive examination. Additional proof of performance is determined by analysis of tryout castings to verify specifications are met.
Welding procedures — Welding is used during the production and upgrading of castings, corresponding to when radiographic examination is required. Welding requirements state that procedures and welder qualifications should meet ASME Section IX (or EN ISO 15614-1 and ISO 9606-1) qualification standards. Similarly, each lot of weld filler must adjust to ASME/AWS chemical analysis specifications. In Europe, compliance should be to EN499. Weld filler must 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 heat code. Material identification is also sometimes shown on the physique casting, such as CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct each visible inspections and mechanical exams on pressure-retaining castings.
As-cast exterior and inside surfaces are inspected visually for unacceptable irregularities, together with hot tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing involves a hydrostatic pressure check to verify the leak tightness of a control valve’s pressure-retaining components, together with the physique and bonnet castings. The test procedure entails a fixture that closes off cavities that might be pressurized in service after which topics the element to the hydrostatic shell test stress acceptable for the valve body material 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 pressure by 1.5 and rounding to the following higher 25 psig increment. Any visually detectable weeping or leaking by way of the stress boundary walls that are a part of the valve assembly is a mandatory trigger for rejection (Figure 3).
Compliance with these specs have to be ensured, in addition to with other necessities regarding materials.
Figure 2. Markings identify the foundry and materials of the valve physique. These management valve bodies had been forged at an Emerson-approved foundry in China.
Meeting materials requirements
Valve casting integrity and quality begins with specifications that call not only for premium materials, but in addition for the materials that work finest in the intended functions. These application necessities embody energy and ductility in addition to resistance to certain elements, together with the make-up of the managed fluid, working temperature and circulate velocity.
For occasion, chemical composition have to be managed precisely to realize an alloy’s supposed efficiency level. Carbon steel castings for valves supposed for use in oil and gas purposes should meet NACE SP0472 recommendations that chemical composition be controlled to lower than zero.43% carbon equivalency. The decrease carbon content improves weldability and reduces the potential for stress cracking by hydrogen sulfide usually found in oil and gasoline production and processing purposes.
Another instance of supplies tied to a selected software include these for upstream oil and gas production. Many of these applications occur in 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 merchandise with global use now comply with twin material specifications to fulfill ASME and European requirements. For example, steel castings are specified and authorized to each ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson typically adds its personal stringent requirements corresponding to the warmth treating of excessive nickel alloys, extra demanding chemical composition or special welding procedures.
In the previous, Emerson has supplemented typical ASTM and ASME specifications to realize the enhanced corrosion-resistance levels and high temperature capabilities provided by high-nickel alloys. This is now accomplished by the new ASTM specification A990, which addresses both material composition and high quality.
Figure 3. Pressure-retaining parts of a valve are subjected to hydrostatic testing to evaluate 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 checks Fisher valve castings. Non-destructive testing radiography is used as a monitoring device. ASTM A990 Class C requires radiography of the primary casting of each 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 performance in corrosive companies and elevated temperatures. However, if high-nickel castings are improperly prepared, they can pose main problems, including poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification course of may be adopted to keep away from these casting difficulties.
The foundry should solid a 1-inch thick high-nickel check plate (Figure 4) that meets ASTM Material Specification A990. It’s troublesome to cast due to the distinction in cross-section between the base 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 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 carefully for cracking along the weld heat-affected zone, casting grain boundaries or dendrite boundaries. Failure to satisfy high quality standards will result within the disqualification of the foundry from additional consideration. Casting patterns should be devoted solely to high-nickel alloy service. Use of carbon metal or a stainless-steel pattern is unacceptable due to variations in solidification properties.
Shrinkage rates for gates, risers and other equipment can range considerably. Once the devoted pattern gear for each 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 — similar to shrinkage — that must be eradicated by modifying the sample rigging.
Figure 4. In เครื่องมือวัดpressure , a casting is full of 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 in depth qualification course of, the foundry was approved and has been delivering high-quality valve physique and bonnet castings to Fisher valve manufacturing websites.
To assist ensure the quality 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 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 received an Excellent Supplier award from Emerson.
Figure 5. This Chinese foundry meets all specs for casting valve our bodies.
Control valve customers may be concerned after they study sure valve elements aren’t made in the U.S. or Europe, however elsewhere. Perhaps their concern stems from experience with different inferior products, corresponding to appliances, clothes or electronics made in those countries and sold on-line. But if the valve elements are being provided to a significant management valve vendor that has gone to nice lengths to qualify the foundry or supplier, then customers may be assured the valves meet all specs.