The Difference Between Bleed Valves and Purge Valves

Pressure control valves are essential components in instrumentation and fluid control applications. While bleed valves, relief valves and purge valves are commonly found in hydraulic systems assisting other components to control pressure, they each have a special purpose. Learn more about the difference between relief valves, bleed valves and purge valves below!

What Are Bleed Valves?

Bleed valves are commonly used with applications to vent pressure or release other fluids. They are built using a threaded bleed screw to open or close the valve when needed. For instance, before starting maintenance work on applications that contain pressurized liquids or gasses, bleed valves are opened to vent pressure or release other matter from within the system. They are also used to drain off fluids during operation for analysis and/or fluid calibration.

Bleed valves are compatible with many other Hy-Lok products. They’re often paired with our gauge valves to safely vent pressure from systems into a containment vessel or to the atmosphere. They also feature a stop-screw opposite the vent tube to prevent accidental removal of the stem and avoid possible leakage.

Hy-Lok’s bleed valves are engineered to withstand up to 10,000 PSI at 100 ºF and manufactured in sizes ranging from ⅛” thru ½” tubing and piping system. They have a temperature rating from -65 ºF to 850 ºF with stainless steel, -20 ºF to 450 ºF with carbon steel and -65 ºF to 500 ºF with alloy 400. The stem thread and valve tips are plated in chrome to elongate the longevity of our bleed valves. With a variety of end connections, including male NPT, female NPT, ISO and SAE threads, Hy-Lok’s bleed valves can be easily integrated into your fluid system.

What Are Purge Valves?

Similar to bleed valves, purge valves are also used to regulate pressure in fluid systems but use a poppet and spring system instead of a threaded bleed screw to open and close the flow. It features a vent hole in the bottom of the valve to drain excess gas or liquid into the atmosphere from the build-up of pressure within the fluid system.

Accidental disassembly is a common issue with purge valves, as the caps can often be removed due to the build-up of pressure flowing through it. To prevent accidental removal, Hy-Lok permanently clamps its purge valve cap to the valve’s body. Our purge valves are manufactured using high-quality materials, including 316 stainless steel, carbon steel and brass. The stainless steel purge valves have pressure ratings up to 4000 PSI, while the carbon steel and brass purge valves have pressure ratings up to 3000 PSI. We offer a variety of different sizes ranging from ⅛” thru ½” and multiple end connections from SAE, NPT and ISO threads to tube adapters.

Hy-Lok Canada: Quality You Can Trust

Hy-Lok Canada is proud to have partnered with hundreds of industrial clients across Canada. With our nationwide network of distributors and expedited shipping services, Hy-Lok’s ready to supply you with the fittings and valves you need, no matter how remote the location is. Contact us today for more information on bleed valves and purge valves, or receive a quote in less than 24 hours when you put in your request online!