Correct choice of process control valves and piping to connect the form of the end (annular surface connecting / convex connection / on the clip-on). Equipped on the flange, such as to require suppliers to provide valve and valve gasket between the flange pair, should be indicated in the Technical Annex to the contract requirements and the flange material, pressure rating and labeling systems to take over the flange. Clip-on control of the valve itself, if a single flange, flange connection wire set screw holes should be metric, if contains the complete thread for the British, should be required to supply-side valve connected with bolts.
If the control valve with a solenoid valve, the proposed contract in the Technical Annex of the solenoid valve to be part of the technical parameters specified manufacturer, brand, voltage levels, explosion-proof form, material requirements and the opening of control valves and related travel time, but without solenoid valve indicate the specific models, specific models should be available valve or calculated in accordance with the final selection of plant-based testing, but it should be stated whether or not to allow suppliers to control the use of gas as the pilot valve solenoid valve. When the control valve of the air volume requirements of the implementing agencies, the control valve in order to shorten the journey time, the solenoid valve as a pilot valve with large flow capacity of pneumatic actuators used in combination, following, you can reduce costs, but also increased the number of the annex, as part of the increase in gas means that the increase in the point of failure, so discussion of the Technical Annex should be used to determine whether to allow control of the gas.
Whether the proposed executing agency Diaphragm or piston executing agency must be equipped with air filtration pressure reducer, so that implementing agencies can be driven by the pressure of gas source.
In the pre-delivery, control valves should be equipped with an annex to the full connectivity in the production plant and tested in conformity with the contract requirements of the Technical Annex. Control valves should be based on supply-side valve applications, the decision to connect the steel pipe, PVC pipe or stainless steel sheath, according to the valve travel time calling for a decision on connecting gas pipe diameter. General control valve connecting the gas pipe diameter shall be not less than 8 × 1mm, because too small will cause the control valve is too slow to respond, of course, if the control valve to allow travel time of the switch, can also use the diameter of 6 × 1mm to connect the gas pipe.
Control valve as far as possible, the aperture size should be consistent with the design documents, if the need to change to the process piping, equipment and related communications professional engineers (such as not allowed to change, then the relevant professionals should discuss it together and decided to change the program), to carry out the appropriate design changes.
Valve should be noted that the corrosion problem. If the control valve by the existence of procurement cavitation, flashing, cavitation, erosion and other issues, they should pay attention to whether or not to take the appropriate means to deal with, can avoid these problems, or as much as possible to reduce the possibility of the occurrence of the phenomenon. Valve, valve core, valve cage, the ring material should be rigid steel or alloy steel, or for processing, such as nitriding or surface coating (for example, Levin-plated Adams too). Control valves should be absolutely avoided under the conditions of a wide range of applications in the emerging phenomenon of cavitation.
Technical Annex to the contract must be in the shape of the valve such as size and location of the installation of the annex to the request to confirm the position to determine the control valve installation space, the annex to the installation directions and drawings on the installation location of the available space there is a conflict between . If there is conflict, we must first confirm whether the executing agency to change the control valve or valve installation position of the annex to the location and orientation of the installation. If you can not change the location of the valve should be circular process, piping, equipment, electrical and other relevant professionals as soon as possible modifications to the layout and design.
Contracts should be required to provide the key components of control valves, material analysis, control valve leakage test reports, test reports pressure to form a test report or certification, gas connection graph, the control valves used in pressure test point of order, method and Control valve leakage testing testing protocols, and methods for inspection, review.
Tender book should be required to tender to provide a sample selection of control valves (on the samples of the specific model code, the initials should be a detailed description), application performance. Technical contract should require the contract to provide the valve body and its day-to-day maintenance manual annex, annex agents and sellers of contact address, fax, phone number.
Control valve attachment should not be lower than protective levels IP54/NEMA4 (digital valve positioner general level of protection for IP65/NEMA4X), junction box into the round of the port should be sealed.
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