250 PRI Product Data Sheet

Product catalog summary

Overview: The document is a product data sheet for the Lee 250 PRI® pressure relief valve, designed for low flow hydraulic applications. It highlights the valve's specifications, performance, materials, and the Lohm system for fluid resistance measurement.

Specifications:

Cracking pressures range from 80 to 3600 psid.
Weighs 4.5 grams and measures 1.1 inches in length.
Constructed entirely of stainless steel for durability.
Includes a Lee Safety Screen for added protection.
100% tested and inspected for reliable performance.

Performance:

Leakage at minimum cracking and shutoff pressure is 2 mL/minute maximum.
Nominal system pressure up to 3000 psi, with a peak pressure of 4100 psi.
Endurance tested to a minimum of 100,000 cycles.

Materials: The valve is made from various stainless steel grades, including 304 CRES, 17-4PH CRES, and 15-5PH CRES, ensuring high strength and corrosion resistance.

Lohm System:

The Lohm is a unit of fluid resistance, analogous to the Ohm in electrical systems.
It simplifies hydraulic computations by compensating for discharge coefficients and dimensional tolerances.
A 1 Lohm restriction allows a flow of 100 gallons per minute of water with a 25 psi pressure drop at 80°F.

Flow Calculations: The document provides formulas for calculating flow rates using the Lohm system, considering factors like liquid density and viscosity.

Additional Tools: The Lee Company offers a free Hydraulic and Pneumatic Flow Calculator slide rule to assist with Lohm calculations.