McDonnell & Miller 250-1-125 Valve

The McDonnell & Miller 250-1-125 is a high-capacity ASME safety relief valve designed specifically for large-scale boiler applications and water heating systems requiring a 125 PSI pressure relief valve. Built with a 1" NPT inlet and outlet, this industrial pressure relief valve features a robust brass body and a high-temperature silicone rubber seat to ensure positive shut-off and prevent leaking after repeated cycles. Rated for a significant 3,735,000 BTU/hr discharge capacity, it provides essential overpressure protection for commercial hydronic systems. The internal stainless steel springs are calibrated for precision, ensuring the valve opens at the exact set point to prevent vessel failure. When upgrading or replacing a boiler safety valve, the model 250-1-125 is the standard for maintaining system integrity under high-demand thermal expansion scenarios. Proper installation requires the discharge piping to be the same size as the valve outlet to avoid backpressure interference during a blowdown event.

• High BTU Rating: Offers a 3,735,000 BTU capacity, making it suitable for high-output commercial water heaters and boilers.
• ASME Section IV Certified: Meets strict safety standards for pressure vessel overpressure protection in hydronic systems.
• Corrosion-Resistant Construction: Features a heavy-duty brass body and stainless steel internal components for longevity in harsh mechanical rooms.
• Fail-Safe Pressure Relief: Engineered to provide immediate full-flow discharge once the 125 PSI threshold is reached.

Commonly Asked Questions

What is the difference between a safety valve and a relief valve in this context?
Technically, this is a relief valve designed for liquid service. It opens proportionally as pressure increases beyond the 125 PSI set point, whereas a safety valve for steam would pop open instantly. This model is intended for water heating and storage tank applications.

Can this valve be mounted horizontally?
For proper operation and to prevent sediment buildup on the seat, it is best practice to install the McDonnell & Miller 250 series in a vertical position with the drain piping sloped for gravity drainage.

How do I verify if 125 PSI is the correct set point for my boiler?
Always check the Maximum Allowable Working Pressure (MAWP) stamped on your boiler's ASME nameplate. The relief valve set pressure must never exceed the MAWP of the vessel it is protecting.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.