ASCO’s 2-position 3-way has both direct-acting and pilot-operated types. How should I choose?
(1) Direct-acting solenoid valve
Generally, it is used in small diameter (ASCO8320 series interface size is 1/8″-1/4″) and low pressure environment. When the valve of this structure is opened, it does not require low pressure of the medium and zero pressure start, so Compared with the start speed of the pilot solenoid valve, it will come faster, and it is especially suitable for places that require fast shut-off.
The power consumption is larger than that of the pilot solenoid valve, generally 5-20w. The coil is easily burned when high-frequency energization, but the control is simple and the application range is wide.(2) Pilot solenoid valve
Pilot solenoid valves are generally used for large-caliber (ASCO8316 series interface size is 3/8″-1″) and high pressure occasions. When the valve of this structure is opened, the low pressure of the solenoid valve must not be lower than 0.05MPa. There must be pilot pressure, otherwise it cannot be opened. In addition, the flow capacity of the pilot solenoid valve is larger than that of the direct-acting solenoid valve. Generally, the CV can reach 3 or more. For the high purity of compressed air, the direct-acting type is not so strict.
The electromagnetic head is small, energy-saving, low power consumption, 0.1-0.2w, can be frequently energized, long-term energization, without burning. The upper limit of the fluid pressure range is higher, but the fluid pressure difference condition must be met. However, the impurities in the liquid are easy to block the pilot valve hole, which is not suitable for liquid use.
Summary of the difference between ASCO solenoid valve direct-acting and pilot-operated
a. Withstand pressure: in terms of the hydraulic pressure of the two, the pilot type can withstand more pressure than the straight-through type.
b. Response time: The direct-acting solenoid valve has a faster start-up speed than the pilot-operated solenoid valve. If you choose to cut off quickly, it is recommended to purchase a direct-acting solenoid valve. Because the pilot solenoid valve is energized, the small valve opens first, the main valve opens later, and the direct-acting solenoid valve opens the main valve directly.
c. Flow capacity: The flow capacity of the pilot type solenoid valve is larger than that of the direct-acting solenoid valve. Generally, the CV value can reach more than 3, while the general CV value of the direct-acting solenoid valve is less than 1. The direct-acting solenoid valve is activated by 0 pressure, and the pilot must have a pilot pressure, which is generally about 2 bar.
d. Power and loss: The direct-acting power is larger than the pilot-acting.
e. Medium cleanliness requirements: the pilot type has higher requirements for the purity of the circulating medium, but the direct-acting type is not so strict.
The difference between ASCO solenoid valve direct-acting type and pilot type, in general, the specific choice still has to refer to the user’s specific working environment and requirements.