When selecting the electric control valve, the caliber […]
When selecting the electric control valve, the caliber should be clear first
The electric control valve is hard-sealed and then welded with wear-resistant alloy, etc. is the choice of shut-off valve. This method also considers the service life and reliability while considering the tightness. Although the factory specifications are only 10-6 to 10-8, it can not achieve the effect of zero leakage of the soft seal, but it is enough to meet the strict and strict requirements, and it Durable, more cost-effective from an economic perspective.
When selecting the electric regulating valve, the caliber should be clear first, this is based on the user's pipeline caliber. The pressure of the pipeline must also be determined. The general pressure level is 1.0MPa-10.0MPa. If the pressure is higher, you can call to order. The material of the electric control valve is also a very important parameter that should be noted when selecting the model. This is mainly based on the medium in the pipeline. The general control valve material is mainly divided into carbon steel and stainless steel.
⒈ The main control parameters selected for the electric control valve are: nominal diameter, design nominal pressure, medium allowable temperature range, flow coefficient, etc.
⒉ For strict occasions requiring a proportional relationship between flow rate and opening height, a special control valve should be used. Ball valves and butterfly valves are generally available for coarse adjustment.
⒊ The sealing performance of the electric control valve is one of the main indicators for evaluating the quality of the valve. The sealing performance of the valve mainly includes two aspects, namely internal leakage and external leakage. Internal leakage refers to the degree of sealing of the medium between the valve seat and the closing member. Outer leakage refers to the leakage of the packing part of the valve stem, the leakage of the middle port gasket part and the leakage of the valve body due to casting defects. Leakage is not allowed.
⒋ The ideal flow characteristics of electric control valves are quick open, parabolic, linear, and equal percentage. It is necessary to select a control valve with appropriate flow characteristics according to the actual working flow characteristics.
⒌ The selection of the nominal diameter of the electric control valve should be determined according to the required valve flow capacity. The nominal diameter of the regulating valve should not be too large or too small. Too large, increase engineering cost, and the valve is in a low percentage range, the adjustment accuracy is reduced, making the control performance worse. If it is too small, the system resistance will increase, and even when the valve is 100% open, the system still cannot meet the set capacity requirements.
6. Adjusting pressure difference and shut-off pressure difference of regulating valve
For regulating electric regulating valves, the allowable regulating pressure difference and shut-off pressure difference are important indicators for their selection. If the actual pressure difference is higher than the allowable adjustment pressure difference of the control valve, the electric control valve will have the problem that it cannot be accurately adjusted, which will seriously damage the valve actuator. The electric control valve is not without its shortcomings: the internal heat generated by the operation of the motor will cause thermal protection and stop the control valve; because the motor has to undergo multi-stage deceleration to output torque, the operating speed is not very fast, and some require rapid opening and closing The occasion is not applicable, high torque and high speed are still a difficult contradiction; due to the large number of moving parts, it is relatively easy to cause failures, especially in frequent adjustment conditions, it is easy to produce motor thermal protection, reduction gear damage, and module SCR For burnout and other faults, it is more appropriate to use pneumatic control valve under this working condition.