Spigot End Gate Valve: A Detailed Explanation of Structure, Applications, and Selection Guide

1. Basic Concept

A spigot end gate valve refers to a gate valve with one end of the valve body designed as a spigot end. Its core function is to control the on-off of media in the pipeline through the lifting of the gate plate. Different from traditional gate valves with flange or threaded connections, the spigot end of this valve can be directly inserted into a matching socket, achieving a sealed connection via rubber seals, crimping, or welding. It is commonly used in pipeline systems that require quick installation or compact layouts.

2. Structure and Material Characteristics

(1) Spigot End Design

· A smooth cylindrical port on the exterior, some with flanges or grooves to fix sealing rings, forming a mechanical seal after inserting into the socket.

(2) Gate Plate Assembly

· The gate plate moves perpendicular to the fluid direction, divided into rigid gate plates and elastic gate plates. The latter is more suitable for sealing uneven pipes.

3. Typical Application Fields

· Municipal engineering: Sectional control of urban water supply networks and switching regulation of buried pipelines.

· Building water supply and drainage: Opening and closing control of fire protection pipelines in high-rise buildings and main water supply/drainage pipes in basements.

· Industrial processes: Corrosive medium pipelines in chemical plants and steam pipelines in thermal power plants.

· Agricultural irrigation: Main pipeline switching for drip irrigation and sprinkler irrigation systems, using PVC spigot end gate valves to reduce costs.

4. Installation and Maintenance Key Points

(1) Key Installation Steps

1. Interface treatment: Clean the spigot end and the inner wall of the socket to ensure no oil or impurities. Apply lubricant to the rubber seal ring for easy insertion.

2. Direction control: The fluid arrow on the gate valve must be consistent with the medium flow direction.

3. Fixing methods:

· Socket type: The insertion depth must reach the marked line to avoid leakage caused by insufficient depth;

· Welded type: Use argon arc welding or copper brazing, and conduct pressure testing after cooling to room temperature.

4. Pressure test: Fill with water to 1.5 times the working pressure, stabilize the pressure for 30 minutes, and check the interface and valve body for leaks.

(2) Maintenance Notes

· Regular inspection:

· Rotate the handwheel of manual gate valves once a quarter to prevent the valve stem from rusting and jamming;

· Observe the aging condition of the sealing ring and replace it promptly if cracks or deformation are found.

· Troubleshooting:

· Incomplete closure of the gate plate: This may be due to wear on the sealing surface, requiring grinding of the gate plate or replacement of the sealing ring;

· Valve stem leakage: Tighten the packing gland or replace the packing (such as graphite packing).

5. Advantages and Limitations

Advantages:

· Low Fluid Resistance: When fully open, the gate plate is entirely separated from the flow channel, resulting in minimal pressure loss. This design is ideal for large-flow transportation.

· Reliable Sealing: Rubber seals or welded connections have a low leakage rate, making them especially suitable for buried or concealed applications.

· Flexible Installation: The spigot end is compatible with socket pipes made from different materials, which minimizes the need for additional connectors.

Limitations:

· Slow switching speed: The gate plate needs to be rotated multiple times to lift, not suitable for emergency shutdown scenarios.

· High installation space requirements: The valve body is long, and sufficient operating space must be reserved when installing on vertical pipelines.

· Easy to freeze and crack at low temperatures: If cast iron material retains water in sub-zero environments, it may crack due to ice expansion.

6. Core Selection Parameters

1. Nominal diameter (DN): Common specifications range from DN25 to DN600, which need to match the inner diameter of the pipeline.

2. Pressure rating: Low pressure: PN ≤ 1.6MPa (household use); medium pressure: PN2.5~PN10 (industrial use); high pressure: PN16~PN40 (special working conditions).

3. Medium characteristics: Brass/cast iron can be selected for water, gas, and oil; stainless steel must be used for acid-base media.

4. Drive mode: Manual is suitable for DN ≤ 300; electric/pneumatic is suitable for remote control or large pipe diameters.

7. Common Questions

Q: Can spigot end gate valves be installed horizontally?

A: Yes, but ensure the handwheel faces upward or to the side for easy operation; when installed underground, add a protective well to prevent sediment from entering the valve stem.

Q: How to distinguish between the spigot end and the socket end?

A: The spigot end is smooth on the outside, with a diameter slightly smaller than the inner diameter of the pipeline, and can be inserted into the socket; the socket end has a cavity inside, with a diameter larger than the outer diameter of the pipeline, used to accommodate the spigot.