Select the valve to consider the description from these 6 perspectives

1, the use of the valve requirements
1 Ordinary gate valves, ball valves, and globe valves are strictly prohibited for adjustment according to their structural characteristics. However, in process design, it is commonly used for conditioning. Due to the adjustment and use, the valve seal is in a throttling state for a long time, the impurities in the oil scouring the seal, damaging the sealing surface, causing the closure to be unsatisfactory or because the operator has caused the seal to seal the seal surface, causing the valve to pass and open. .
2 The valve installation position is unreasonable. When the medium contains impurities, no filter or filter is installed at the front end to allow impurities to enter the valve interior, causing damage to the sealing surface, or impurities deposit on the bottom of the valve, causing the valve to be closed tightly. There is a leak.
2, from the perspective of process requirements
1 For corrosive media, if the temperature and pressure are not high, non-metallic valves should be used as much as possible; if the temperature and pressure are high, a lining valve can be used to save precious metals. When selecting a non-metallic valve, economic rationality should still be considered; for a medium with a large viscosity, a smaller six groups are required, and six small valves such as a DC shut-off valve, a gate valve, a ball valve, and a plug valve should be used. Six groups of small valves have low energy consumption; when the medium is special medium such as oxygen or ammonia, the corresponding oxygen special valve or ammonia valve should be used.
2 Double-flow pipelines should not use directional valves, and non-directional valves should be used. For example, after the heavy oil pipeline of the refinery stops running, the steam should be reversely purged to prevent the heavy oil from solidifying and block the pipeline. It is not appropriate to use the shut-off valve because it is easy to erode the sealing surface of the shut-off valve when it flows backward. The effect of the valve is affected, and the gate valve should be selected.
3 For some media with crystallization or sedimentation, it is not advisable to use shut-off valves and gate valves because their sealing faces are susceptible to crystallization or deposit wear. Therefore, it is appropriate to use a ball valve or a plug valve; a slab gate valve is also available, but a jacket valve is preferred.
4 In the selection of gate valve, the single-bar of the open rod is more suitable for corrosive medium than the double-bar of the dark rod; the single-gate is suitable for medium with high viscosity; the adaptability of wedge-type double-gate to high temperature and deformation of sealing surface It is better than the wedge type single shutter, and there is no jamming due to temperature change, especially if it is more rigid than the gate.
5 Half-water, steam valve on the official road, can use cast iron valves, but if the steam is stopped in the outdoor steam pipe, it will cause condensed water to freeze, thus freezing the valve. Therefore, in cold regions, the valve is made of cast steel, low-temperature steel or effective insulation measures.
6 For highly toxic highly toxic media or other harmful media, bellows-structured valves should be used to prevent media from leaking from the packing.
7 gate valve, globe valve and ball valve are valves used in the valve * large, should be considered comprehensively. The gate valve has strong circulation capacity, and the energy consumption of the conveying medium is small, but the installation space is large. The structure of the shut-off valve is simple, the maintenance is convenient, but the flow resistance is large. The ball valve has the characteristics of low flow resistance and quick opening and closing, but the use temperature is limited. In petroleum medium and other medium with high viscosity, the gate valve is mostly used in consideration of the flow capacity of the gate valve. On the water and steam pipelines, the shut-off valve is applied, and the pressure drop is not large. Therefore, the shut-off valve is applied in medium pipes such as water and steam. More, the ball valve can be used under the conditions of the working conditions.
3, from the perspective of ease of operation
1 For large-diameter valves and long-distance, high-altitude, high-temperature, high-pressure occasions, electric and pneumatic valves should be used. For flammable and explosive occasions, explosion-proof devices should be used. For reliable use, hydraulic and pneumatic devices are used.
2 For valves that need to be opened and closed quickly, butterfly valves, ball valves, plug valves or quick-opening gate valves should be used according to requirements. It is not advisable to use general gate valves and globe valves. In the case where the operating space is limited, it is not advisable to use a bright gate valve. It is advisable to use a dark rod gate valve, but it is better to use a butterfly valve.
4, from the accuracy of adjusting the flow rate
When it is necessary to accurately adjust the flow rate, the regulating valve should be used. When the accuracy of his small flow is required, a needle valve or a throttle valve should be used. When it is necessary to reduce the pressure behind the valve, a pressure reducing valve should be used. To maintain the stability of the pressure behind the valve, a pressure reducing valve should be used.
5, from the temperature and pressure resistance
High-temperature and high-pressure medium often adopts chromium-molybdenum steel and chromium-molybdenum-vanadium steel for casting. For the ultra-high temperature and high-pressure medium, the corresponding forgings should be considered. The comprehensive performance of forgings is better than that of castings, and the temperature and pressure resistance are superior to castings.
6, considering cleanliness
In food and bioengineering production and transportation, the requirements of the valve on the process pipeline need to consider the cleanliness of the medium, and the general gate valve and globe valve cannot be guaranteed. From the point of view of cleanliness, no valve is comparable to a diaphragm valve.

1 Diaphragm valve has a simple structure, a variety of valve body and diaphragm materials, can be widely used in food and bioengineering, but also suitable for some difficult and transportable and dangerous media.
a. Only the valve body and the diaphragm are in contact with the flow, and the other parts are all isolated, and the valve can be thoroughly sterilized by steam.
b, has its own ability to discharge.
c, can be repaired online. Diaphragm valves have therefore become widely used in the food and bioengineering sector*.
2 bottom valve. In the case of strict requirements on the **, there is almost no room for choice in the discharge valve at the bottom of the tank. The bottom valve is directly on the bottom head of the drought storage tank when the equipment is manufactured. It is very different from the commonly used method of making a nozzle at the bottom of the tank, and then connecting the valve on the nozzle. When the valve is closed, the spool is The inner bottom of the tank is Xiangping, so it effectively eliminates the dead angle in the tank, so that all the liquid in the tank can be fully mixed in the fermentation process, and the unique steam sealing system greatly reduces the contamination of the product. possibility.