Application and installation requirements of Pneumatic 3-way control valve

Application and installation requirements of Pneumatic 3-way control valve

The Pneumatic 3-way control valve has two structural forms: confluence and diversion. The valve core structure adopts a cylinder thin-walled window and adopts the side guidance of the valve core. The three-way valve can replace two two-way valves and one three-way connecting pipe in some occasions, and it is widely used in the two-phase regulation of heat exchangers, as well as simple proportioning regulation. When the nominal diameter and pressure difference are small, the combined valve can be used for shunting occasions and can be used interchangeably, but the nominal diameter is greater than 80mm and pressure. It can not be used interchangeably when the difference is large.

Pneumatic 3-way control valve is a very common and important control equipment in industrial production. Whether it works normally or not is directly related to the normal production of the whole device. At present, with the rapid development of control valve technology, there are many manufacturers and forms of control valves, and their functions are also different. The following focuses on the common problems that should be paid attention to before the installation and operation of various types of pneumatic three-way control valves.

1. Incoming inspection before installation of pneumatic three-way control valve incoming inspection of control valve is a very important link to confirm whether the arrival of control valve meets the design requirements. Each technical requirement of the field regulating valve should meet the design requirements, but the following items should be emphatically checked during the incoming inspection.

2. Specification of valve body / Trim: this item mainly includes: valve model, valve type, nominal diameter, valve seat size, valve core form, flow characteristics, leakage grade, valve body material, valve core material, valve seat material, CV value, flange standard grade size and sealing surface form, etc. in case of any inconsistency with the design, the design shall be confirmed and approved.

3. For the actuator part, the model, type, action form, spring range, air supply pressure, etc. of the actuator shall be checked.

4. This item of positioner mainly checks the input signal, air source pressure, electrical and air source interface size and explosion-proof grade of the positioner, and the explosion-proof grade shall not be lower than the design grade requirements.

5. Accessories shall be carefully cleaned according to the design and technical requirements of the regulating valve, such as filter pressure reducing valve, valve position switch, solenoid valve, handwheel mechanism and special tools. The inspection of the above contents can be realized by cleaning, measuring instruments, checking nameplate and special detection means (such as flange and bolt materials can be identified by spectral analysis).

6. Hydrostatic test of  Pneumatic 3-way control valve the hydrostatic test of the valve body includes the pressure test of the valve body and the leakage test when the valve element is fully closed. Generally, when the design pressure of the control valve exceeds 10MPa, the valve body must undergo a pressure test to check the pressure resistance of the valve body and the upper bonnet.