(1) valve pressure rating, temperature and corrosion resistance, etc. should not be less than the requirements of the pipeline process connections, and factory approved products should be preferred.

    (2) Water vapor or water more wet gas and explosive media, should not use cast iron valve.

    (3) When ambient temperature is below -20 (especially the north), not use cast iron valve.

    (4) cavitation, erosion and more severe temperature and pressure medium consisting of rectangular coordinates, the pressure connection for the 1.5MPA two o'clock outside the region, cutting the sealing surface should be used for wear-resistant materials such as cobalt Division based alloy or surfacing alloy Terai.

    (5) of strong corrosive medium, the choice of corrosion resistant alloys must be based on media type, concentration, temperature, pressure difference, choose a suitable corrosion-resistant materials.

    (6) Body parts were treated with the throttle, throttle body wall and allow a certain small rate of corrosion, the corrosion rate in the LMM / years; cutting pieces by high-speed erosion, corrosion, leakage increases will arch , the corrosion rate should be less than 0.1MM / year.

    (7) on the lining materials (rubber, plastic) of the choice of the working fluid temperature, pressure, concentration must meet the use of the material and consider it when the valve is physical, mechanical damage (such as shear failure) .

    (8) should not use the vacuum valve body lined with rubber, plastic structure.

    (9) water treatment system, two shut-off valve should not be optional rubber lining material.

    (10) Typical Typical corrosion resistant alloy material media options:

    A, sulfuric acid: 316L, Hastelloy, Alloy 20,
6, the spring range of options:

    (1) First, select the spring range, but also to determine the scope of the work of the spring.

    (2) to determine the scope of work involved in calculating the spring force to overcome the imbalance of power output. In case of difficulties, should conditions (mainly the pressure valve is closed) to tell manufacturers to help calculate and adjusted the factory springs and scope of work (currently, many manufacturers simply do not calculate).

    7, the flow of choice:

    (1) in the throttle, valve open against the direction of media flow away and to shut off flow of the direction of flow.

    (2) the choices of the flow of a single seal type valve, single seat valve, angle valve, single-sleeve valve seal three major categories. It provides the base flow (such as seat valve, V ball), and any movement (such as the O ball).

    (3) When the DG "15 when the flow is usually open election, when DG <= 15 small-caliber valve, especially high-pressureflow valve optional closed in order to improve life.

    (4) two optional flow switch valve closed.

    (5) If the flow of closed-type valve to oscillate, change over, open-type flow can be eliminated.

    8, the choice of filling:

    (1) control valve is commonly used fillers and graphite PTFE V-O-filler.

    (2) PTFE packing friction is small, but the temperature difference, short life; graphite packing friction, but the temperature, long life; high temperature and with the proposed election of the valve positioner graphite packing.

    (3) If the PTFE packing often change, you might consider packing with graphite.

    9, attachment options:

    (1) the annex to the main control valve are: positioning, converters, following the drive, boost valve, to secure his position valve, relief valve, filter, lubricator, limit switch, position the sender, solenoid valves, hand wheel.

    (2) features and accessories to complement the role of ensuring valve operation. Necessary to increase, not to increase unnecessarily. Necessary, increase prices and reduce the annex would increase reliability.

    (3) Locator main function is to increase the output force and velocity, do not need those features, do not take, not like with the locator.

    (4) rapid response system, not the fast valve, optional converter.

    (5) where strict proof, optional: electrical converters + pneumatic positioner.