Across many forms of merchandise in a wide selection of industries, the follow of combining assorted elements from various sources all over the world is the rule, not the exception. Should this be a concern for a management valve user? For instance, when an finish consumer discovers that a quantity of components are being made in China (Figure 1), ought to the consumer fear 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 number of checks and balances in place focusing on product high quality to make sure management valves operate as designed, want minimal maintenance, carry out safely and operate within environmental laws.
Yet, regardless of such efforts by the seller, a management valve user may have questions about world sourcing and the country of origin. This article discusses how one major control valve vendor ensures product high quality. Many different management valve vendors follow the identical or similar procedures.
Quality specification brings world assurance
Emerson enforces a complete quality specification for its Fisher management valves that must 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 sample castings
Production castings
Certification of compliance
Supplier qualification — Suppliers endure a rigorous qualification course of. The course of thoroughly investigates a possible supplier’s capacity to fulfill materials specifications and applicable international codes and requirements — in addition to particular requirements associated to element manufacture. In the case of castings, a foundry is considered “qualified” when it passes a important evaluation by Fisher’s engineers.
The foundry must demonstrate a record of qualification by a third-party inspection company and conform to varied requirements, such as ISO 9001:2000, ASME, A2LA, PED and others. It should cross a evaluation of its quality program in addition to on-site audits of the foundry’s processes and procedures corresponding to welding, warmth remedy and non-destructive examination. Additional proof of efficiency is set by evaluation of tryout castings to verify specs are met.
Welding procedures — Welding is used during the production and upgrading of castings, such as 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, every lot of weld filler must adjust to ASME/AWS chemical evaluation specs. In Europe, compliance have to 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 indicate the heat code. Material identification is also typically proven on the physique casting, corresponding to CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct both visible inspections and mechanical exams on pressure-retaining castings.
As-cast exterior and inside surfaces are inspected visually for unacceptable irregularities, including hot tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing involves a hydrostatic stress check to substantiate the leak tightness of a control valve’s pressure-retaining components, including the body and bonnet castings. The test process includes a fixture that closes off cavities that might be pressurized in service after which subjects the part to the hydrostatic shell test strain applicable for the valve physique materials and class.
ASME B16.34 sets out the hydrostatic test pressure to make use of for steel 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 through the stress boundary partitions that are a part of the valve assembly is a compulsory cause for rejection (Figure 3).
Compliance with these specs should be ensured, as properly as with different necessities regarding materials.
Figure 2. Markings identify the foundry and materials of the valve body. These control valve our bodies were cast at an Emerson-approved foundry in China.
Meeting material necessities
Valve casting integrity and high quality begins with specs that call not just for premium supplies, but additionally for the materials that work best within the meant applications. These application requirements include energy and ductility as nicely as resistance to sure components, together with the make-up of the managed fluid, working temperature and circulate velocity.
For instance, chemical composition must be controlled precisely to achieve an alloy’s supposed efficiency degree. Carbon metal castings for valves supposed for use in oil and gasoline applications should meet NACE SP0472 recommendations that chemical composition be controlled to less than zero.43% carbon equivalency. The lower carbon content improves weldability and reduces the potential for stress cracking by hydrogen sulfide sometimes found in oil and fuel manufacturing and processing applications.
Another example of supplies tied to a particular application embrace those for upstream oil and gas manufacturing. Many of those purposes happen within the arctic areas 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 dual material specifications to satisfy ASME and European standards. For example, steel castings are specified and licensed to both ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson often adds its personal stringent requirements corresponding to the warmth treating of high nickel alloys, more demanding chemical composition or particular welding procedures.
In the past, 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 completed by the new ASTM specification A990, which addresses both material composition and quality.
Figure 3. Pressure-retaining components 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 tests Fisher valve castings. Non-destructive testing radiography is used as a monitoring device. ASTM A990 Class C requires radiography of the first casting of every pattern. The acceptance criterion is Level three for categories A, B and C. For categories D through G, no cracking, scorching tears or inserts are allowed as laid out in ASTM A990.
High-nickel alloy castings present improved performance in corrosive providers and elevated temperatures. However, if high-nickel castings are improperly prepared, they’ll pose main problems, together with poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification course of can be adopted to avoid these casting difficulties.
The foundry must forged a 1-inch thick high-nickel take a look at plate (Figure 4) that meets ASTM Material Specification A990. It’s tough to forged due to 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 full of a matching composition weld material. The welder and procedure 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 cut from the plate and bent over a 1½-inch mandrel per ASTM A990 into a U-shape.
The bars are examined closely for cracking along the weld heat-affected zone, casting grain boundaries or dendrite boundaries. Failure to satisfy quality requirements will outcome 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 as a result of variations in solidification properties.
Shrinkage rates for gates, risers and other accessories can vary significantly. Once the devoted sample tools for each of those components has been secured, try-out castings are poured for each pattern-alloy combination. The castings are then radiographed.
The intent is to disclose any inherent casting defects — such as shrinkage — that must be eradicated by modifying the pattern 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 solid Fisher valve bodies for more than a decade. After เกจวัดแรงดันน้ำประปาราคา by procurement and manufacturing specialists, followed by an intensive qualification process, the foundry was accredited and has been delivering high-quality valve body and bonnet castings to Fisher valve manufacturing websites.
To help guarantee the standard of the castings it produces, the Chinese foundry has carried out international standards 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 three times 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 specs for casting valve bodies.
Summary
Control valve customers may be concerned after they be taught sure valve elements usually are not made in the us or Europe, however elsewhere. Perhaps their concern stems from expertise with other inferior merchandise, corresponding to home equipment, clothes or electronics made in those countries and sold on-line. But if the valve parts are being equipped to a significant control valve vendor that has gone to nice lengths to qualify the foundry or provider, then customers can be assured the valves meet all specs.
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