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Relief ValvesLee Pressure Relief Valves are specifically designed to be the smallest valves available for safety relief applications. The smallest is only 3/16" in diameter and just over 1/2" long, and weighs only 1.5 grams. Seven different types are available, offering a wide range of cracking pressures and flow rates.

Available Designs:

Lee PRI (Pressure Relief Insert)
Lee PRIThese 0.187”, 0.250” and 0.281” diameter relief valves are constructed entirely of stainless steel and are available screened and unscreened. Built-in damping assures quiet operation. Cracking pressures for the 187 PRI range from 20 - 100 psid, and for the 250 and 281 PRI from 80-3600 psid.

Momentum PRI
These 0.375” and 0.500” diameter relief valves use the patented “momentum free” design concept, which compensates for momentum forces that upset the normal force balance of a direct acting valve. These momentum forces are produced by localized pressure gradients resulting from velocity changes within the valve. These valves offer both linear and stable operation with minimal hysteresis. Both valves are available with cracking pressures from 50-500 psid.

Zero Leak PRI
This 0.281” diameter valve is ideal for thermal relief and low flow hydraulic pressure relief applications where zero leakage is needed. Available cracking pressures range from 800 to 4700 psid.

High Pressure PRI
These 0.281” and 0.375” diameter relief valves are designed for applications where operating pressures and pressure spikes are too severe for conventional relief valves. Such conditions can lead to instability, erosion and structural damage of conventional relief valves. Both valves are available in a range of cracking pressures for system pressures up to 5,000 psi.

High-Q PRI
The High-Q PRI pressure relief valve, sometimes referred to as an LRU (Line Removable Unit), is designed for applications that require both a high relief pressure and a high flow rate in a compact package. The valve is capable of relief pressures up to 5,400 psid and flow rates over 19 GPM. The valve uses a side inlet flow path to minimize the installation boss size and weight.

NACE Compliant PRI
The 0.281” diameter NACE Compliant PRI is constructed of materials specifically chosen for optimal performance in harsh duty applications, such as those in the oil tool industry. This high speed, direct acting valve is constructed entirely of corrosion-resistant materials that are compliant with NACE specification MR0175/ISO 15156. A screened and unscreened model is available for system pressures up to 3000 psi. A high pressure screened model is also available for system pressures up to 5000 psi.

Lee TRI and High Pressure Lee TRI (Thermal Relief Insert)
Lee TRIThese 0.187” and 0.250” diameter Thermal Relief Valves are specifically designed to relieve pressure caused by thermal expansion of a trapped fluid volume, and are optimized for relieving small flows. The 187 TRI uses an advanced technology ceramic ball and seat to provide the toughness and dimensional stability needed for tight shutoff. The incorporation of an integral 15µm CRES filter upstream of the valve seat solves any low flow contamination problems. The Lee TRI is not recommended for general pressure relief service as excess total flow through the valve may cause clogging of the integral filter. The 250 High Pressure TRI is intended for applications where the valve will experience severe pressure spikes or pressure change rates in excess of 25,000 psi per second. The valve’s tight hysteresis and rugged design make it the preferred selection for these types of applications.