It is a common phenomenon in the current market economy environment that only the specification, material, structure description, size and model meet the purchase requirements when ordering. However, this is wrong because a simple valve model covers only a few technical requirements, and the requirements covered in this part cannot be completely correct from the model It can easily cause the information asymmetry between the supply and demand of the valve, delay the normal installation and use time or cause major accidents after installation. Therefore, it is necessary to write out detailed and correct technical documents in the process of valve procurement.
These valves are divided into ordinary valves and special valves first. The engineer will receive a summary of valve materials for each unit, which generally includes valves of various forms, sizes and materials. For example, ordinary non-metallic lined valve, ordinary non-metallic valve, common metal valve, high temperature valve, low temperature valve, oxygen valve, low leakage level valve, heat preservation valve, etc. Because the strength of different manufacturers is different, the technical proposal must be separately submitted when distributing the technical tender. Therefore, more than one valve procurement technical specification will be prepared in a relatively large project, so the technical documents can be well adapted to the requirements of quotation.
(1) The scope shall clearly indicate the pertinence of the technical specifications prepared, such as valve type and requirements in which aspects, what works to use and what devices are used.
(2) The basic data on site includes: environmental conditions, installation site and operation medium characteristics.
Indicate whether the valve installation site is outdoor or indoor; environmental conditions include such as main meteorological parameters table: monthly average temperature, historical limit minimum and maximum temperature, wind speed, relative humidity, etc.; in the characteristics of operating medium, the composition and content proportion of operating medium shall be indicated. These conditions may sometimes affect the structure and configuration of products provided by the valve, such as The anti freezing problem in cold area, the anti-corrosion paint grade and the adaptability of each spare parts to the environment should be considered.
(3) The application standards and regulations shall include manufacturing standards, inspection and test standards, material standards, etc. In terms of valve standards / American standards, there are many standards of API, ASTM, ASME, MSS and other societies or valve associations, while most of them are GB, JB, Hg or sh standards in China. Different design, inspection, material and structural connection dimension standards have different requirements, which reflect that the structure, length and configuration of valves are different, which leads to different prices. Generally, ASME or API standard makes valves more expensive than those made in GB or JB. When API valves are quoted in SH standard system, the difference between temperature and pressure values should be noted. Especially carbon steel and chrome molybdenum steel, due to the poor comparability of the materials used by both, the same nominal pressure level will appear, while sh flange is much lower than the allowable pressure value of API valve at the same temperature. At this time, the strength of flange material should be properly improved, otherwise, the valve capacity will be wasted. In addition to the basic standards such as manufacturing standards, inspection and test standards and material standards, other standards involved in the product must be filled in completely, otherwise, it may cause trouble and error. For example, when the valve is butt welded, the application standard of its nozzle, the application standard of joint weld groove, and the pipe number shall be given.
(4) The main technical requirements include design and manufacture, materials, inspection and test, nameplates, coating packaging and transportation, submission documents, technical services, acceptance, after-sales service, guarantee of valves.
- a. The material requirements shall specify the standards and codes, material names, performance grades and forming methods of materials required by valves. When the valve manufacturer processes and manufactures according to this, it shall provide the chemical composition and mechanical performance test report of relevant materials, and provide NDT report for parts requiring NDT.
- b. Design and manufacture shall describe as much as possible the relevant structural types, structural characteristics, design and manufacturing standards and special requirements of the required valves according to the actual use requirements, so as to facilitate the valve manufacturer to manufacture the valve which meets the actual needs more accurately according to the description.
- c. The code of inspection and test standards for valves shall be specified in inspection and test; corresponding inspection and test requirements shall be put forward. If there are special requirements, it shall be separately proposed and explained. For parts requiring NDT, the nondestructive testing method and receiving grade shall be specified.
- d. The technical documents required by the valve manufacturer in the bidding, after ordering and delivery shall be specified respectively as required.
- e. Specify the relevant standards for coating packaging and transportation of valves required and make appropriate supplement. Such as valve surface pretreatment, coating type, coating thickness, packaging and transportation type requirements.
- f. The contents, materials and fixing methods of the valve nameplate shall be specified.
- g. It is required that the valve manufacturer shall provide the technical services for the supplied valve after winning the bid.
- h. After sales service, guarantee and guarantee are specified according to actual needs.
- i. Specify the acceptance method and acceptance requirements. The acceptance includes factory acceptance, arrival acceptance, intermediate acceptance and final acceptance.
(5) Valve data sheet is the specific requirements of valve products proposed by valve ordering unit to valve factory. It shall include valve code, structure type, driving mode, connection type, nominal pressure, nominal size, quantity, application standard (pipe wall thickness shall be given simultaneously during butt welding), material and material standard of valve body, gasket of valve cover, valve cover bolt, valve inner part number, valve stem packing, execution The common conditions (if any) and other contents used by the mechanism; for pipe fittings, pipes, etc., it shall include product name, nominal wall thickness, quantity, material, structural requirements, specifications, material standards, application standards, connection types, etc. The filling of this item is not only trivial but also detailed. 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 the project construction. This is the core part of valve procurement, especially for special valves, whether to choose the right and economic products is particularly important. If this step can be done in place, then it has been half successful for the correct selection of valves.
(6) The technical documents for special technical requirements negotiation are different from those used for the final contract signing. At this time, the manufacturer has not yet determined the situation of the manufacturers who come to bid are different, and some technical requirements are not suitable for specific proposal. At this time, some questions that have an impact on the quality of the product can be raised and answered by the manufacturer. For example, the material smelting method to be adopted by the manufacturer, the items of process evaluation, type test items, the qualification rate and internal index of type test, delivery status, origin, application performance of similar conditions, delivery period, after-sales service, quality assurance period, etc. If the price is unified, the negotiation can be carried out on the items affecting the price, such as setting a valve leakage level, and then adjusting according to the negotiation results.
Post time: Apr-16-2021