McDonnell & Miller 325500 Head Gasket

The McDonnell & Miller 325500, also known as the Model 150-14H, is a high-performance 8-hole head gasket specifically engineered for Series 150S and Series 157S low water cut-offs. Designed for raised flange head units, this gasket provides a critical pressure-tight seal between the boiler control body and the head mechanism. Unlike standard fiber gaskets, the 150-14H is often fabricated from PTFE (Teflon) or high-yield composite materials to withstand the thermal cycling and chemical environment of commercial steam boiler applications. For successful field installation, technicians must ensure the raised face flange surfaces are cleared of old debris using a scraper before aligning the eight mounting holes. Tightening the bolts in an alternating star pattern to the manufacturer-specified torque of 14-20 ft-lb is recommended to prevent steam leaks and ensure the low water cut-off maintains precise calibration. This OEM replacement part is essential for maintaining the pressure integrity of boiler controllers in both high and low-pressure hydronic systems.

• Precision Compatibility: Specifically designed for McDonnell & Miller 150 series units with 8-bolt raised flange heads.
• Robust Material Construction: High-grade PTFE gasket composition resists degradation from boiler chemicals and steam.
• Leak Prevention: Engineered to provide consistent compression across the raised face flange for a reliable seal.
• Standardized Fit: Direct replacement head gasket for 325500, ensuring zero-clearance issues during maintenance.

• Can I use this gasket on a flat face flange? No, the 150-14H is specifically for raised flange head units. Using it on a flat face may result in uneven compression and potential steam bypass.
• What is the bolt pattern for the 325500? This is an 8-hole gasket. Check your existing head mechanism; if you have an older 4-bolt or 6-bolt unit, this part will not align.
• Does the gasket require additional sealant? Typically, these Teflon gaskets are designed to be installed dry on clean, smooth surfaces. Always inspect the raised face for pitting before installation.

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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.