Structural Features And Applications Of Commonly Used Valves

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(1) Gate Valve:

1. Structural features of gate valves:

A gate valve is composed of a lower valve body, an upper valve cover, a gate plate, a valve stem, a handwheel, a sealing ring and other parts.

(1) Gate plates: They are classified into wedge rigid single gate plates, wedge elastic single gate plates, wedge double gate plates, double gate plates, etc

(2) Valve stem: Visible stem and concealed stem. The exposed stem is the valve stem that rises and falls along with the opening or closing of the gate. The concealed stem means that the valve stem only rotates and rises and falls along with the opening and closing of the gate plate, and the position of the valve stem remains unchanged.

(3) Small-diameter gate valves are generally manual, while large-diameter gate valves can be driven by spur gears or electric motors.

2 The application scope of gate valves

Parameter range of gray cast iron and ductile iron gate valves:

Nominal pressure PN0.1-4.0Mpa;

Nominal diameter: DN50-1800mm;

Connection form: Flange connection

Parameter range of steel gate valves

Nominal pressure PN0.1-4.0Mpa;

Nominal diameter: DN50-1800mm;

Connection form: Flange connection

3. Precautions

1) It is not suitable for regulating the pressure and flow rate of the medium.

2) It is suitable for coking applications, but elastic gate valves and double gate valves are not recommended.

3) For large-diameter or high-pressure gate valves, a bypass valve can be installed to reduce the opening and closing torque of the main gate valve.

4) For applications with very high sealing performance requirements, the valve stem should adopt bellows sealing.

4. Advantages and disadvantages:

Advantages: Low flow resistance, unrestricted medium flow direction, and relatively short installation length of valve components.

Disadvantages: The gate plate and sealing surface are prone to scratches, the sealing surface is difficult to maintain, and the height requirement for the valve installation space is large.

5. Common Faults and Their Handling

(1) Leakage of packing: The general treatment methods are to tighten the cover or stop the gas supply and replace the packing.

(2) Treatment methods for oil cup leakage:

A. Leakage at the oil cup thread – Tighten the oil cup or stop the gas supply and reinstall the oil cup.

B. Oil cup mouth leakage – Grease or replace the oil cup.

(3) Handling method for tight handwheel: Add lubricating oil, replace the packing and clean the shaft

(4) Internal leakage treatment methods: Drain and repair the gate plate

6. Daily maintenance: Cleaning, turning the wheel, draining, adding lubricating oil, and greasing