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Cut-off valve types and selection principles


Stem and seat sealing surface perpendicular to the axis of cutoff valve stem to open or close the relatively short trip. Once the valve is in the open position of the valve between its seat and valve sealing surface is no longer in contact with, and has a very reliable cutting action, making the cut-off valves suitable for medium cut or regulation and throttle use .

Once the valve is turned on, its valve seat and valve sealing surface is no longer in contact, thus sealing surface mechanical wear a smaller cut-off valve. Because most of the valve seat and valve repair or replacement is easier when the sealing element without the entire valve removed from the pipeline, which for the valves and pipes welded into one of the occasions are very applicable. Medium flow direction through the valve when such a change, and therefore a higher cut-off valve flow resistance in other valves.

The most obvious advantage of cut-off valve is: open and closed process, because the valve to the friction between the valve sealing surface is smaller than the gate, so wearable. Cut-off valve open seat height is typically only 1/4 channel diameter, so much smaller than the gate. Usually in the valve body and valve sealing surface is only one, and thus the manufacturing process is better, ease of maintenance.

Cut-off valve selection principles are:

1, the cut-off valve should use high temperatures, high pressure tubing, or media devices. Fire power plants, nuclear power plants, petrochemical system of high temperature, high-pressure pipeline.

2, the cut-off valve in the pipeline with the strict requirements of the convection resistance pipeline. Namely, the pressure loss is not the place to consider.

3, the choice of a small needle valve, instrument valves, sampling valves, pressure needle and so on.

4, flow regulation or pressure regulation, but accuracy is not required to adjust, and the pipeline diameter and relatively small, such as Nominal by pipeline ≤50mm, the shut-off valve should be selected.

5, the industrial production of small synthetic fertilizers and fertilizer should use large nominal PN160 PN320 nominal pressure PN 16MPa or 32MPa high-pressure or high angle globe valve throttle angle. 6. Bayer process alumina production workshop desilication, pipeline easy to coke, easy selection of the divided body, can place the seat, carbide seal pair of DC-DC type valve or throttle.

7, the urban construction of water supply, heating engineering, Nominal by smaller pipeline, the choice of cut-off valve, balance valve or piston valve, such as Nominal by less than 150mm in the pipeline.

Commonly used cut-off valve are the following:

1) angle type valve; the angle globe valve, the fluid simply by changing a direction, so that the pressure drop through the valve shut-off valves smaller than the conventional structure.

2) DC-type valve; in DC-type or Y-shaped valve, the valve body of the flow channel and the main channel into a slash, the extent of damage to the state of this flow is smaller than the conventional cut-off valve, so the pressure loss through the valve accordingly the small.

3) plunger-type valve: This form of cut-off valve is a variant of the conventional cut-off valve. In the valve, the valve and seat are usually designed based on the plunger principle. Polished into the plunger and valve stem is connected seal is set on the plunger two elastic seals to achieve. Two elastic seals separated by a collar, and through the valve cover nut load exerted on the valve cover seals around the plunger pressure prison. Elastic ring can be replaced, you can use a variety of materials, the valve is mainly used in the "on" or "off", but with a special form of plunger or special rings can also be used to regulate the flow .


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