Across many forms of merchandise in quite so much of industries, the practice of combining assorted elements from numerous sources around the globe is the rule, not the exception. Should this be a priority for a management valve user? For instance, when an end user discovers that several elements are being made in China (Figure 1), should the consumer fear about the quality?
When dealing 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 specializing in product high quality to make sure control valves operate as designed, want minimal upkeep, carry out safely and function within environmental regulations.
Yet, despite such efforts by the vendor, a control valve user may have questions about international sourcing and the country of origin. This article discusses how one main management valve vendor ensures product quality. Many other management valve distributors follow the identical or related procedures.
Quality specification brings world assurance
Emerson enforces a complete high 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 greater than a dozen necessities 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 undergo a rigorous qualification course of. The process thoroughly investigates a potential supplier’s capacity to satisfy material specifications and applicable worldwide codes and requirements — as well as specific requirements related to component manufacture. In the case of castings, a foundry is considered “qualified” when it passes a important analysis by Fisher’s engineers.
The foundry should reveal a record of qualification by a third-party inspection company and conform to various standards, such as ISO 9001:2000, ASME, A2LA, PED and others. It must pass a review of its quality program in addition to on-site audits of the foundry’s processes and procedures corresponding to welding, heat treatment and non-destructive examination. Additional proof of performance is set by analysis of tryout castings to confirm specifications are met.
Welding procedures — Welding is used in the course of the production and upgrading of castings, such as 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, every lot of weld filler must comply with ASME/AWS chemical analysis specifications. In Europe, compliance must 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 warmth code. Material identification can additionally be sometimes proven on the body 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 external and inside surfaces are inspected visually for unacceptable irregularities, together with sizzling tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing involves a hydrostatic pressure test to substantiate the leak tightness of a control valve’s pressure-retaining parts, including the body and bonnet castings. The check process involves a fixture that closes off cavities that may be pressurized in service after which topics the element to the hydrostatic shell check stress appropriate for the valve physique materials and class.
ASME B16.34 sets out the hydrostatic test 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 following higher 25 psig increment. Any visually detectable weeping or leaking by way of the stress boundary walls that are a half of the valve assembly is a compulsory cause for rejection (Figure 3).
Compliance with these specifications should be ensured, in addition to with other requirements regarding supplies.
Figure 2. Markings establish the foundry and materials of the valve physique. These management valve bodies had been cast 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 in addition for the supplies that work finest in the supposed purposes. These utility necessities embody power and ductility in addition to resistance to sure elements, together with the makeup of the controlled fluid, operating temperature and move velocity.
For occasion, chemical composition have to be managed exactly to achieve an alloy’s intended efficiency degree. Carbon metal castings for valves supposed for use in oil and fuel functions should meet NACE SP0472 recommendations that chemical composition be controlled to lower than 0.43% carbon equivalency. The decrease carbon content improves weldability and reduces the potential for stress cracking by hydrogen sulfide typically found in oil and gas manufacturing and processing functions.
Another example of supplies tied to a specific application include these for upstream oil and gas manufacturing. Many of those purposes happen in 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 specs to satisfy ASME and European standards. For example, metal castings are specified and certified to both ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson often provides its own 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 improved corrosion-resistance levels and excessive temperature capabilities supplied by high-nickel alloys. This is now accomplished by the new ASTM specification A990, which addresses both materials composition and high quality.
Figure 3. Pressure-retaining components of a valve are subjected to hydrostatic testing to gauge the parts’ integrity. Visible leakage or seepage via a casting means automated rejection.
Qualifying a foundry
As a 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 first casting of each sample. The acceptance criterion is Level three for classes 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 present improved performance in corrosive companies and elevated temperatures. However, if high-nickel castings are improperly prepared, they will pose main issues, together with poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification process can be adopted to keep away from these casting difficulties.
The foundry should forged a 1-inch thick high-nickel take a look at plate (Figure 4) that meets ASTM Material Specification A990. เกจวัดแก๊สหุงต้ม to forged due to the distinction 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 an identical composition weld materials. 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 reduce from the plate and bent over a 1½-inch mandrel per ASTM A990 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 satisfy high quality standards will 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 other equipment can differ considerably. Once the devoted sample gear for every of those parts has been secured, try-out castings are poured for every pattern-alloy combination. The castings are then radiographed.
The intent is to reveal any inherent casting defects — such as shrinkage — that must be eradicated by modifying the pattern rigging.
Figure 4. In a foundry evaluation, 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 bodies for greater than a decade. After an exploratory visit by procurement and manufacturing specialists, followed by an intensive qualification process, the foundry was approved and has been delivering high-quality valve body and bonnet castings to Fisher valve manufacturing websites.
To help ensure the quality of the castings it produces, the Chinese foundry has carried out worldwide standards and has obtained certifications for German TUV and CE, Norway DNV, German Lloyd’s and American ABS, and has passed worldwide quality system certifications of ISO 9001 and QS -9000.
The foundry has been awarded Gold Medals 3 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 our bodies.
Summary
Control valve customers may be involved after they study sure valve components are not 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 offered online. But if the valve elements are being supplied to a significant control valve vendor that has gone to great lengths to qualify the foundry or supplier, then users may be assured the valves meet all specs.
Share