Valve Types & Selection FAQ
Expert answers on different valve types including gate, globe, ball, check, butterfly, control, diaphragm, knife gate, plug, and needle valves.
What is the difference between a gate valve and a globe valve?
Gate valves are designed for on/off service with minimal pressure drop. They feature a straight-through flow path and a wedge that moves perpendicular to flow. Best for: fully open/closed applications, minimal pressure drop, infrequent operation.
Globe valves are designed for throttling and flow regulation with a Z-shaped internal path. Best for: flow control, frequent operation, precise regulation, applications where pressure drop is acceptable.
When should I use a ball valve instead of a gate valve?
Choose a ball valve for: Quick operation (90° turn), tight shut-off with minimal leakage, compact design, lower cost for smaller sizes, bi-directional flow, clean non-abrasive fluids.
Choose a gate valve for: Larger sizes (DN 150+), high-temperature applications (above 200°C), minimal pressure drop in fully open position, compliance with API 600/602 standards.
What are the different types of check valves and their applications?
1. Swing Check Valve: Disc swings on a hinge. Best for low-velocity applications and horizontal lines.
2. Lift Check Valve: Disc lifts vertically. Ideal for high-pressure systems and steam service.
3. Wafer Check Valve: Compact, lightweight design between flanges. Perfect for space-constrained installations.
4. Dual Plate Check Valve: Two spring-loaded plates. Excellent for low-pressure drop and compact installation.
5. Non-Slam Check Valve: Prevents water hammer with assisted closing. Essential for pump discharge lines.
6. Tilting Disc Check Valve: Disc tilts on a shaft. Suitable for large diameter pipes and low-pressure drop.
What is a butterfly valve and when should it be used?
A butterfly valve uses a rotating disc to control flow (90° operation). Advantages: Lightweight, low cost, quick operation, suitable for large diameters, low pressure drop when open.
Best Applications: Water treatment, HVAC systems, fire protection, slurry handling, low to medium pressure applications.
Limitations: Not suitable for high-pressure throttling, abrasive media at high velocities, or applications requiring zero leakage.
What is a control valve and how does it differ from an on/off valve?
A control valve modulates flow by varying the valve opening in response to a control signal. Unlike on/off valves, control valves operate continuously at various positions.
Key Features: Precise flow control, actuator-driven (pneumatic/electric/hydraulic), positioner for accurate positioning, characterized flow (linear, equal percentage, quick opening), integrated with control systems (DCS, PLC).
Common Types: Globe-style control valves, angle valves, butterfly control valves, ball control valves, diaphragm control valves.
What is a diaphragm valve and where is it used?
A diaphragm valve uses a flexible diaphragm to control flow. The diaphragm isolates the valve's internal mechanism from the process fluid.
Advantages: Excellent for corrosive and abrasive fluids, no packing glands (leak-free stem), suitable for slurries and viscous fluids, easy to clean and maintain, ideal for hygienic applications.
Applications: Chemical processing, pharmaceutical exporting, food & beverage, water treatment, mining slurries, corrosive media handling.
What is a knife gate valve and when is it preferred?
A knife gate valve features a thin, sharp-edged gate that cuts through thick fluids, slurries, and media with suspended solids.
Best Applications: Pulp and paper industry, mining and mineral processing, wastewater treatment, slurry handling, viscous fluids with solids.
Advantages: Compact design, bi-directional sealing, minimal pressure drop, ability to handle thick, fibrous, or abrasive media.
What is a plug valve and how does it work?
A plug valve uses a cylindrical or tapered plug with a passage through it to control flow. Rotating the plug 90° opens or closes the valve.
Types: 1) Lubricated Plug Valve (uses lubricant for sealing), 2) Non-Lubricated Plug Valve (uses sleeve/liner), 3) Eccentric Plug Valve (reduces friction with offset design).
Applications: Oil & gas, chemical processing, high-pressure systems, multi-port flow diversion.
What is a needle valve and what are its uses?
A needle valve has a long, tapered, needle-like stem that provides precise flow control in small-bore applications.
Key Features: Extremely precise flow control, small orifice size, high-pressure capability, fine adjustment capability.
Applications: Instrumentation lines, sampling systems, gauge connections, gas chromatography, precise flow metering applications.
What is a pressure relief valve and why is it important?
A pressure relief valve (PRV) or safety relief valve (SRV) automatically releases pressure when it exceeds a predetermined set point, protecting equipment and personnel from overpressure conditions.
Types: Spring-loaded PRV (most common), Pilot-operated PRV (large flow capacities), Balanced bellows PRV (compensates for backpressure).
Applications: Boilers, pressure vessels, pipelines, compressors, any pressurized system requiring overpressure protection per ASME Section VIII.
What is a 3-way valve and its applications?
A 3-way valve has three ports for mixing or diverting flow. Types: L-port (90° flow change) and T-port (straight-through or diverting).
Applications: Temperature control systems, flow diversion, mixing applications, bypass systems, heat exchangers, process control.
What is the difference between a Y-type and basket strainer?
Y-Type Strainer: Y-shaped body with screen at an angle. Compact, suitable for high-pressure, can be installed horizontally or vertically. Best for: steam, gas, and liquid applications.
Basket Strainer: Larger screening area, easier to clean, higher dirt-holding capacity. Best for: liquid applications with high debris content, frequent cleaning requirements.
What is a solenoid valve?
A solenoid valve is an electromechanically operated valve controlled by an electric current through a solenoid coil.
Types: Direct-acting (small sizes), pilot-operated (larger sizes), 2-way, 3-way, normally open, normally closed.
Applications: Automated control systems, water treatment, irrigation, pneumatic systems, process automation.
What is a pressure reducing valve (PRV)?
A pressure reducing valve automatically reduces high inlet pressure to a lower, constant outlet pressure regardless of flow variations.
Applications: Building water supply, steam distribution, gas distribution, protecting downstream equipment from high pressure.
Note: Different from pressure relief valve (same acronym PRV but opposite function).
What is a steam trap and how does it work?
A steam trap automatically drains condensate from steam systems while preventing steam loss.
Types: 1) Thermodynamic (disc type, most common), 2) Mechanical (float & thermostatic, inverted bucket), 3) Thermostatic (bellows, bimetallic).
Applications: Steam heating systems, process steam lines, steam tracing, condensate removal.