Valve Guide: Types, Functions, and Applications
Section 1: Control Valves and Screw Closure
Screw Closure
A screw:
- Interior: Thread rod driver fits into a capsule.
- Exterior: RBI stem thread is on the outside of the capsule.
Screw Valve Types
- Globe Valve: Spherical body with ends in a straight line. Rod axis is perpendicular to the body ends.
- Oblique Valve: Spherical body with ends in a straight line. Rod axis is oblique to the body ends.
- Valve Conduits in Right Angles: Cylindrical body with ends at right angles. Rod axis is straight with one end of the body.
- Needle Valve: Body ends are straight, right-angled, or oblique. Needle-nosed disk for precise regulation.
- Other: Side valves, three-step valves, or T-junction valves.
Section 2: Check Valves
Check Valve
Valve: Prevents backflow using a retention mechanism. Opens with fluid flow and closes with the weight of the mechanism or counterpressure.
Check Valve Models
- Horizontal: Straight ends for horizontal installation.
- Vertical: Straight ends for vertical installation.
- Angular: Ends at right angles for installation between vertical and horizontal.
Types of Retention Mechanisms
- Swing Type: Oscillating disk on a hinge.
- Vertical Closing Type: Disc, piston, or ball that rises linearly along the seat body axis.
- Retention Disc: Disc-shaped retention mechanism.
- Retention Piston: Cylinder with a piston and cylinder shock absorber.
- Ball Retention: Sphere-shaped retention mechanism.
Other Check Valves
- Valve and Control Screw: Holds the disc closed regardless of flow, restricting disc elevation.
- Foot Valve: Vertical check valve installed at the bottom of a suction pipe.
Section 3: Gate Valves
Gate Valve
Gate Valve: Provides direct fluid flow passage. Straight body ends with a gate moving between the seats via a stem.
Types of Stems
- Internal Screw: Screw driver inside the valve.
- Interior Screw Upward Stem: Wheel fixed to the stem, rising when the valve opens.
- Inner Screw Non-Rising Stem: Gate rises when the valve opens.
- Rising Stem Inside Screw: Wheel fixed to a rising stem, rising with the spindle when the valve opens.
- External Screw: Screw rod outside the dome.
- External Screw, Rising Stem with Wheel: Wheel fixed to the stem, rising when the valve opens.
- External Screw, Stem Rises Through Wheel: Wheel fixed to a bracket, stem rises through it when the valve opens.
- External Screw, Non-Rising Spindle: Handle attached to a non-rising spindle, stem rises when the valve opens.
Types of Gate Valves
- Wedge Gate Valve: Operates via wedge action between the gate and body seats.
- Solid Wedge: One-piece gate forming the core.
- Split Wedge: Two-part gate.
- Valve Release: Massive wedge gate used for aqueducts.
- Double Disc Gate Valve: Two discs separated by an expansion mechanism.
- Parallel Slide Valve: One or more discs sliding parallel between body seats.
Section 4: Safety Valves
Safety Valve
Safety Valve: Automatically releases pressure exceeding a predetermined safe level. Used for steam and other gases.
Types of Safety Valves
- Common Lifting: Valve head automatically rises at least D/24.
- Spring-Loaded: Load applied directly to the valve head via a compression spring.
- Weight-Loaded: Load applied to the valve head via a weight.
- Lever and Weight Pressure: Pressure applied to the valve head via a weight actuated by a lever and fulcrum.
- Spring and Lever Resistance: Resistance applied to the valve head via a spring acting through a lever and fulcrum.
- Bottom Valve Head: Pressure applied to two valve heads via a tension spring.
- High Elevation: Valve head automatically rises at least D/12.
- Total Elevation: Valve head section rises automatically. When fully raised, a download area surrounds the valve seat edge.
- Pilot-Operated: Hole ensures maximum discharge capacity with relay operation.
- Torsion Bar: Pressure load applied by a torsion bar spring.
- Electrically Powered: Electrical energy used for pressure relief.