How to compile technical specifications for valve procurement?
It is a common phenomenon in the current market economy environment to only specify the specifications, materials, structure descriptions, dimensions, and models to meet the procurement requirements when ordering valves. However, this approach is wrong, because a simple valve model, so Only a small part of the technical requirements covered, and this part of the requirements covered can not be completely reflected in the model, so it is easy to cause asymmetric information between the supply and demand of the valve, delay the normal installation and use time or after installation. Major accident. Therefore, it is very necessary to compile detailed and correct technical documents when purchasing valves.
These valves are first divided into ordinary valves and special valves. The engineer will receive the valve material summary of each device, which generally includes various forms, sizes and materials of valves. For example, ordinary non-metal lined valve, ordinary non-metal valve, ordinary metal valve, high temperature valve, low temperature valve, oxygen valve, low leakage valve, insulation valve, etc. Because the strength and focus of different manufacturers are different, they must be put forward separately when distributing technical bidding documents. Therefore, more than one technical specification for valve procurement will be prepared in a relatively large project, so the technical documents prepared can well meet the requirements of quotation.
① The scope shall clearly indicate the pertinence of the technical specifications prepared, such as the valve type and requirements, the project to be used, and the device to be used, etc.
② The field basic data include: environmental conditions, installation site and operating medium characteristics.
Indicate whether the valve installation site is outdoor or indoor; the environmental conditions include the table of main meteorological parameters, such as monthly average temperature, historical minimum and maximum temperature, wind speed, relative humidity, etc.; the composition and content proportion of the operating medium should be indicated in the characteristics of the operating medium. For valves, these conditions sometimes affect the structure and configuration of the products provided by it, such as It is necessary to consider the antifreeze problem in cold areas, the anti-corrosion coating grade and the adaptability of various parts to the environment.
③ Application standards and regulations shall include manufacturing standards, inspection and test standards, material standards, etc. In terms of valve standards / American standards include API, ASTM, ASME, MSS and other standards of various societies or valve associations, while in China, most of them are GB, JB, HG or sh standards. Different design, inspection, material and structural connection dimension standards have different requirements, which are reflected in the different structure, length and configuration of valves, resulting in different prices. Generally, valves manufactured according to ASME or API standards are more expensive than those manufactured according to GB or JB standards. When using API valve in SH standard system, the difference of temperature pressure value between them should be paid attention to. Especially for carbon steel and chromium molybdenum steel, due to the poor comparability of the two materials, the allowable pressure value of SH flange is much lower than that of API valve at the same temperature for the same nominal pressure class. At this time, the strength grade of flange material should be appropriately improved, otherwise the valve capacity will be wasted. In addition to manufacturing standards, inspection and test standards, material standards and other basic standards, other standards involved in the product must be filled in completely, otherwise it may cause trouble and mistakes. For example, when the valve is butt welded, the application standard of its connecting pipe, the application standard of joint weld groove, and the pipe label shall be given.
④ The main technical requirements include valve design and manufacture, material, inspection and test, name plate, coating packaging and transportation, submission of documents, technical service, acceptance, after-sales service, guarantee.
- a. The material requirements shall specify the standard and code, material name, performance grade and forming method of the materials required for the valve. When the valve manufacturer processes and manufactures according to the requirements, it shall provide the chemical composition and mechanical property test report of the relevant materials, and the non-destructive test report shall be provided for the valves parts requiring non-destructive test.
- b. The design and manufacture should describe as much as possible the relevant structural types, structural characteristics, design and manufacture standards and special requirements of the required valves according to the actual use needs, so that the valve manufacturers can manufacture the valves that meet the actual needs more accurately according to the description.
- c. During the inspection and test, the inspection and test standard code of the valve shall be specified; the corresponding inspection and test requirements shall be put forward; if there are special requirements, they shall be separately put forward and explained, and the NDT method and acceptance level shall be specified for the parts requiring NDT.
- d. The technical documents to be submitted by the valve manufacturer during bidding, after ordering and during delivery shall be specified as required.
- e. Relevant standards for coating, packaging and transportation of valves shall be specified and supplemented appropriately. Such as valve surface pretreatment, coating type, coating thickness, packaging and transportation type requirements.
- f. The contents, materials and fixing methods of the required valve name plates shall be specified.
- g. It is stipulated that the valve manufacturer shall provide technical services for the supplied valves after winning the bid.
- h. After sales service, guarantee and guarantee are stipulated according to actual needs.
- i. Specify the acceptance methods and requirements. Acceptance includes factory acceptance, arrival acceptance, intermediate acceptance and final acceptance.
⑤ The valve data sheet is the specific requirements of valve products put forward by the valve ordering unit to yaang valve. It shall include valve code, structure type, driving mode, connection type, nominal pressure, nominal size, quantity, application standard (the wall thickness of connecting pipe shall be given at the same time when butt welding), valve body material and material standard, bonnet gasket, bonnet bolt, valve trim number, stem packing, etc. For pipe fittings and pipes, it should include product name, nominal wall thickness, quantity, material, structural requirements, specifications, material standards, application standards, connection types, etc. The filling in of this item is not only cumbersome but also meticulous. If the item is omitted, it will bring great mistakes to the procurement work, especially when purchasing from abroad, it will bring huge economic losses, and may involve the progress of engineering construction. This is the core part of valve procurement, especially for special valves, it is particularly important to choose the right products correctly and economically. If this step can be done in place, then it is half the success for the correct selection of valves.
⑥ The technical documents of special technical requirements negotiation bidding are different from the technical attachments used for the final contract signing, because the manufacturer has not been determined at this time, and the situation of the manufacturers coming to bid is not the same, so some technical requirements are inconvenient to be put forward. At this time, we can put forward some questions that have an impact on product quality, and let the manufacturer answer them. For example, the smelting method of materials to be adopted by the manufacturer, the items of process evaluation, the items of type test, the qualified rate and internal indicators of type test, the delivery status, the place of origin, the application performance of similar conditions, the delivery date, after-sales service, the quality assurance period, etc. In order to unify the basis of quotation, we can also negotiate on the items that affect the price, such as specifying a valve leakage level, and then adjust according to the negotiation results.
Source: China Valve Manufacturer – Yaang Pipe Industry Co., Limited (www.steeljrv.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
If you want to have more information about the article or you want to share your opinion with us, contact us at [email protected]
Please notice that you might be interested in the other technical articles we’ve published:
- Sealing Tests for Valves
- The Origin and Development of the Valve
- Nine Anti-Corrosion Measures of Valves
- The Selection of Control Valve
- Operation and Maintenance Manuals for Gate Valves
- When the control valves are used in liquid service
- Choosing Valves Based on Industry Characteristics
- How to choose valves
- Corrosion Fatigue of Valves
- How to choose a valve
- What is a fully welded ball valve
- Application status and key design requirements of cryogenic valve in LNG field