Mechanical Seal Self Priming Pump

The Mechanical Seal Self Priming Pump is designed for clean water and light chemical applications where zero leakage is required and the pumped liquid is free of large solids or abrasives. Unlike gland packing that allows controlled leakage, the mechanical seal provides a positive seal with no visible leakage. This is essential for potable water applications, chemical transfer, and any application where leakage cannot be tolerated. The self-priming capability allows the pump to be located above the water source, eliminating the need for foot valves and manual priming.

The mechanical seal is of the cartridge type, pre-assembled at the factory for easy installation and replacement. The seal consists of a stationary face (mounted in the seal chamber) and a rotating face (mounted on the shaft). The faces are lapped flat (within 0.0003mm) and pressed together by spring pressure. A thin film of liquid lubricates the faces. Seal face materials are selected for the specific fluid. For clean water, silicon carbide vs. carbon is standard. Silicon carbide vs. carbon provides long life (3 to 8 years) with low friction. For light chemicals, silicon carbide vs. silicon carbide with FKM elastomers is used.

The self priming mechanism is integrated into the pump casing. The priming chamber separates air from liquid during the priming cycle. When the pump starts, the impeller creates a vacuum that draws air from the suction line into the priming chamber. The air is discharged out of the pump. A recirculation port returns a portion of the liquid to the priming chamber to maintain the liquid seal. Within 30 to 60 seconds, all air is evacuated from the suction line and the pump is primed. Once primed, the pump operates as a standard centrifugal pump.

The mechanical seal is located above the impeller, isolated from debris that might settle in the pump casing. The seal chamber is designed with a large volume and flush connection to keep the seal faces clean. For applications where the pump may run dry during the priming cycle, we offer mechanical seals with dry-running capability (carbon vs. carbon or carbon vs. ceramic). However, for extended dry running, gland packing is recommended.

The impeller is of the enclosed type for maximum efficiency. The enclosed impeller has front and rear shrouds with vanes between them. This design minimizes internal recirculation and achieves peak efficiency of 75 to 85 percent. The impeller is dynamically balanced to ISO 1940 Grade G2.5 to ensure smooth, vibration-free operation. For clean water and light chemicals, the enclosed impeller provides the best performance.

The casing is manufactured from cast iron with epoxy coating for water service, or stainless steel for chemical service. The priming chamber has a drain plug and a removable cover for inspection and cleaning. The casing incorporates a sight glass to verify prime visually. A recirculation port is sized to maintain the liquid seal during priming.

The bearing system is designed for long service life. For close-coupled pumps (impeller mounted directly on motor shaft), the motor bearings are specified with higher load capacity. For frame-mounted pumps, a separate bearing housing contains the bearings. Bearings are grease-lubricated for easy maintenance. Bearing temperature monitoring (RTD) is optional.

The motor is a high efficiency IE3 or IE4 unit, TEFC enclosure for outdoor use. For variable flow applications, we offer VFDs with inverter-duty motors. The pump is available with electric motor or diesel engine drive. Diesel-driven units are skid-mounted with fuel tank and control panel.

In summary, the Mechanical Seal Self Priming Pump delivers zero leakage and automatic self-priming for clean water and light chemical applications.