Cross-Section of a Fire Main Isolating Valve (Gate Valve)
A gate valve is a suitable choice for isolating sections of a fire main due to its positive shut-off and low-pressure drop characteristics. Here’s a breakdown of its key components in a cross-section, along with suggested materials:
- Valve Body: The main housing that encloses all internal components. It should be made of high-strength material to withstand high water pressure in fire main systems.
- Suitable Material: Cast Iron (Ductile Iron or Nodular Iron) – Ductile iron offers a good balance between strength and ductility, making it resistant to high pressures and potential shock loads.
- Gate: A movable wedge-shaped disc that slides vertically within the body to control flow.
- Suitable Material: Cast Steel or Stainless Steel – These materials provide excellent strength and corrosion resistance, ensuring reliable operation in saltwater environments. Some fire main gate valves may use bronze for the gate due to its good wear resistance and sealing properties.
- Seat Rings: Sealing surfaces within the body that the gate comes in contact with to form a tight closure.
- Suitable Material: Bronze or Nickel-Alloy – These materials offer good wear resistance and corrosion resistance, ensuring a leak-proof seal when the gate is closed.
- Spindle: The shaft connected to the gate, used for manual or actuated control of the gate’s position.
- Suitable Material: Stainless Steel – This material offers high strength and corrosion resistance, ensuring smooth operation of the gate and resisting saltwater corrosion.
- Packing: Sealing material around the spindle to prevent water leakage along the shaft.
- Suitable Material: Graphite or PTFE (Teflon) – These materials provide good sealing properties and are relatively resistant to wear and tear.
- Bonnet (Optional): A bolted or screwed cover that secures the top of the valve body and provides access to the packing for maintenance.
- Suitable Material: Cast Iron (Ductile Iron) or Cast Steel – These materials offer sufficient strength and can be easily bolted or screwed to the valve body.
- Handwheel or Gear Operator: A mechanism attached to the spindle for manual operation of the gate valve.
- Suitable Material: Cast Iron, Steel, or Ductile Iron – These materials offer adequate strength for manual operation. Some valves may use stainless steel for the handwheel for improved corrosion resistance.
Note: This is a general description, and the specific materials used for each component may vary depending on the valve design, pressure rating, and manufacturer’s specifications.