Across many kinds of products in a wide selection of industries, the practice of mixing assorted elements from varied sources all over the world is the rule, not the exception. Should this be a priority for a control valve user? For example, when an end person discovers that a quantity of elements are being made in China (Figure 1), ought to the consumer fear concerning the quality?
When coping with a major valve vendor, the reply is “no.” There shouldn’t be any room for doubt when the seller has a quantity of checks and balances in place focusing on product quality to ensure control valves operate as designed, want minimal maintenance, carry out safely and operate within environmental rules.
Yet, despite such efforts by the seller, a management valve person could have questions about international sourcing and the nation of origin. This article discusses how one major control valve vendor ensures product quality. Many different control valve distributors comply with the same or comparable procedures.
Quality specification brings international assurance
Emerson enforces a complete high quality specification for its Fisher management valves that should be met by suppliers of pressure-containing and structural steel castings. The high quality specification includes more than a dozen necessities that apply to the following 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 ability to meet material specs and relevant worldwide codes and requirements — in addition to particular necessities related to part manufacture. In the case of castings, a foundry is considered “qualified” when it passes a crucial analysis by Fisher’s engineers.
The foundry should show a report of qualification by a third-party inspection company and conform to numerous standards, such as ISO 9001:2000, ASME, A2LA, PED and others. It must cross a review of its high quality program in addition to on-site audits of the foundry’s processes and procedures such as welding, heat remedy and non-destructive examination. Additional proof of efficiency is determined by evaluation of tryout castings to confirm specs 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 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 should comply with ASME/AWS chemical analysis specs. In Europe, compliance must be to EN499. Weld filler should have actual 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 is also usually proven on the physique casting, similar 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 inner surfaces are inspected visually for unacceptable irregularities, including hot tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing includes a hydrostatic strain take a look at to verify the leak tightness of a control valve’s pressure-retaining parts, including the body and bonnet castings. The take a look at procedure includes a fixture that closes off cavities that may be pressurized in service and then subjects the element to the hydrostatic shell test pressure appropriate for the valve body material and sophistication.
ASME B16.34 sets 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 higher 25 psig increment. Any visually detectable weeping or leaking through the stress boundary partitions that are a half of the valve meeting is a mandatory trigger for rejection (Figure 3).
Compliance with these specs have to be ensured, as nicely as with different requirements regarding materials.
Figure 2. Markings establish the foundry and materials of the valve body. These management valve our bodies had been forged at an Emerson-approved foundry in China.
Meeting material requirements
Valve casting integrity and high quality begins with specs that decision not only for premium supplies, but in addition for the materials that work best in the meant functions. These utility necessities embody power and ductility in addition to resistance to sure factors, including the make-up of the managed fluid, operating temperature and flow velocity.
For occasion, chemical composition have to be controlled exactly to achieve an alloy’s intended efficiency degree. Carbon steel castings for valves intended to be used in oil and gasoline applications should 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 sometimes found in oil and fuel manufacturing and processing functions.
Another example of supplies tied to a particular application embody those for upstream oil and fuel manufacturing. Many of these purposes happen 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 world use now adjust to dual material specs to fulfill 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 provides its personal stringent requirements similar to the heat treating of excessive nickel alloys, more demanding chemical composition or special welding procedures.
In the past, Emerson has supplemented typical ASTM and ASME specifications to attain the improved corrosion-resistance levels and high temperature capabilities offered by high-nickel alloys. This is now achieved by the new ASTM specification A990, which addresses both material composition and quality.
Figure 3. Pressure-retaining elements 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 part of a potential foundry’s qualification, Emerson inspects and exams Fisher valve castings. Non-destructive testing radiography is used as a monitoring tool. pressure gauge ยี่ห้อ tk requires radiography of the primary casting of each pattern. The acceptance criterion is Level three for categories A, B and C. For categories D by way of G, no cracking, sizzling tears or inserts are allowed as specified in ASTM A990.
High-nickel alloy castings provide improved efficiency in corrosive services and elevated temperatures. However, if high-nickel castings are improperly prepared, they’ll pose major issues, together with poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification process may be adopted to keep away from these casting difficulties.
The foundry must cast a 1-inch thick high-nickel test plate (Figure 4) that meets ASTM Material Specification A990. It’s tough to forged 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 material. The welder and procedure 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 satisfy quality standards will end result in the disqualification of the foundry from additional consideration. Casting patterns must be devoted solely to high-nickel alloy service. Use of carbon metal or a stainless-steel sample is unacceptable as a outcome of differences in solidification properties.
Shrinkage charges for gates, risers and other accessories can vary considerably. Once the devoted sample tools 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 eliminated by modifying the pattern rigging.
Figure 4. In a foundry analysis, 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 greater than a decade. After an exploratory go to by procurement and manufacturing specialists, followed by an extensive qualification course of, the foundry was accredited and has been delivering high-quality valve body and bonnet castings to Fisher valve manufacturing sites.
To assist ensure the standard 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 passed worldwide 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 obtained an Excellent Supplier award from Emerson.
Figure 5. This Chinese foundry meets all specs for casting valve our bodies.
Control valve customers can be involved after they be taught sure valve components are not made in the us or Europe, but elsewhere. Perhaps their concern stems from experience with other inferior products, corresponding to home equipment, garments or electronics made in those nations and bought online. But if the valve parts are being supplied to a significant management valve vendor that has gone to great lengths to qualify the foundry or provider, then users could be assured the valves meet all specifications.