Look at the conventional valve from different angles - Wuzhong instrument

Valve application requirements

(1) General gate valves, ball valves, and globe valves are prohibited from regulating according to their structural characteristics. However, in process design, it is commonly used for mediation. Due to the conditioning application, the valve seal is in a saving state for a long time, and the impurities in the oil wash the seal, damage the sealing surface, and form a loose closure or because the operator in order to make the sealing surface that has been damaged to achieve sealing, forming the phenomenon of passing and opening the valve.

(2) The position of the valve equipment is unreasonable, when the medium contains impurities, there is no filter or filter screen at the front end, so that the impurities enter the inside of the valve, forming damage to the sealing surface, or impurities accumulate at the bottom of the valve, causing the valve to be closed loosely and leakage.

Look at the conventional valve from different angles - Wuzhong instrument

Look at the conventional valve from different angles - Wuzhong instrument

1. Consider from the perspective of process requirements

(1) For corrosive media, if the temperature and pressure are not high, non-metallic valves should be selected as much as possible, and if the temperature and pressure are high, fabric valves can be used to save precious metals. When selecting non-metallic valves, economic rationality should still be considered; For the medium with large viscosity, it is required to have a small flow resistance, and valves with small flow resistance, such as direct flow globe valves, gate valves, ball valves, and plug valves, should be selected. Valves with low flow resistance and low energy consumption; When the medium is oxygen or ammonia and other special medium, the corresponding oxygen special valve or ammonia valve should be selected.

(2) Directional valves should not be selected for double-flow pipelines, but non-directional valves should be selected. For example, after the heavy oil pipeline of the refinery is suspended, the pipeline should be purged in reverse with steam to prevent heavy oil condensation from blocking the pipeline, and the shut-off valve should not be selected here, because when it comes to reverse inflow, the sealing surface of the shut-off valve is simply eroded, and the efficiency of the valve is also affected, and the gate valve should be selected.

(3) For some media with crystallization or precipitate, it is not advisable to use globe valves and gate valves, because their sealing surfaces are simply worn by crystallization or precipitation. Therefore, it is more appropriate to choose a ball valve or plug valve; Flat gate valves are also available, but jacketed valves are preferred.

(4) In the selection of gate valves, the open rod single ram and the dark rod double ram are more suitable for corrosive media; The single ram is suitable for media with high viscosity; The adaptability of the wedge-type double ram to the deformation of the sealing surface is better than that of the wedge-type single ram, and there will be no jamming due to temperature changes, especially it is more superior than the rigid single ram.

(5) Cast iron valves can be used for valves on general water and steam pipelines, but if the steam stops in the outdoor steam pipelines, condensate will form and freeze, thus freezing the valves. Therefore, in cold areas, it is advisable to use cast steel, low-temperature steel or effective insulation measures for valves.

(6) For highly toxic media or other harmful media with great risk, valves with bellows structure should be selected to prevent the medium from leaking from the packing.

(7) Gate valves, globe valves and ball valves are the most widely used valves, and should be considered when selecting. The flow of the gate valve can be strong, the energy consumption of the transport medium is less, but the equipment space is larger, the structure of the globe valve is simple, the maintenance is convenient, but the flow resistance is larger, the ball valve has the characteristics of low flow resistance and fast opening and closing, but the use temperature is limited, and the viscosity of petroleum products and other media is large, considering that the flow of the gate valve can be strong, most of the gate valves are selected; In the water and steam pipelines, the use of shut-off valves, the pressure drop is not large, so the shut-off valve is used more in water, steam and other medium pipelines, and the ball valve can be used under the condition of the operating conditions.

2. From the perspective of convenience of operation

(1) For large-diameter valves and long-distance, high-altitude, high-temperature, high-pressure occasions, electric and pneumatic valves should be selected, explosion-proof equipment should be selected for flammable and explosive occasions, and hydraulic and pneumatic equipment should be used for safety and reliability.

(2) For the valves that need to be opened and closed quickly, butterfly valves, ball valves, plug valves or quick-opening gate valves should be selected according to the needs, and general gate valves and globe valves should not be selected. In the case where the operating space is limited, it is not advisable to use the open rod gate valve, and the dark rod gate valve should be used, but it is best to use the butterfly valve.

3. Consider the accuracy of conditioning and saving

When the demand is accurate and the amount is saved, the conditioning valve should be selected, and when the accuracy of the small flow rate is required, the needle valve or saving valve should be selected. When the pressure behind the valve is reduced, the pressure reducing valve should be selected, and the pressure stabilizing valve should be selected when the pressure behind the valve is to be maintained.

4. It can only be considered from temperature and pressure resistance

Chromium-molybdenum steel and chromium-molybdenum-vanadium steel of castings are often selected for high-temperature and high-pressure medium, and the corresponding castings should be considered for ultra-high-temperature and high-pressure medium.

5. Consider cleanability

In the production and transportation of food and bioengineering, the requirements for valves on the process pipeline need to consider the cleanliness of the medium, and the general gate valve and shut-off valve cannot be guaranteed. In terms of cleanability, there is no valve that can compare with a barrier valve.

(1) The barrier valve has a simple structure, a variety of valve body and barrier materials, which can be widely used in the field of food and biological engineering, and is also suitable for some difficult to transport and risky media.

a. Only the valve body and barrier are touched with the flow, and the other parts are all isolated, and the valve can be completely sterilized with steam.

b. Have its own ability to drain clean.

c. Can be repaired online. As a result, barrier valves have become the most widely used valves in the field of food and bioengineering.

(2) Foot valve.

In the case of strict sterilization requirements, there is simply no choice between the discharge valve at the bottom of the tank. The bottom valve is directly welded to the bottom of the storage tank when the equipment is made, and the general selection of a nozzle at the bottom of the tank, and then connect the valve on the nozzle is very different, when the valve is closed, the valve core is flat with the inner bottom of the storage tank, so it effectively gets along with 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 is added, which greatly reduces the possibility of product infection.

Look at the conventional valve from different angles - Wuzhong instrument

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