Pumps require mechanical sealing in the region where a shaft driven by a motor enters a housing. Pumps can often contain fluid within the housing. It is desirable to seal the shaft entry of the pump to prevent any fluid in the housing from entering the atmosphere or affecting shaft bearings.
A typical mechanical seal will utilize a sealing face that is rotating against another sealing face. The sealing faces are held together by mechanical means, such as springs, hydraulic pressure, or a combination thereof.
An inherent part of a mechanical seal is the paradoxical notion that it must leak in order to work. Almost all mechanical seals utilized for pumps utilize the process fluid as lubrication for the seal faces. As such, some process fluid flows through the mechanical seal and exit the housing.
While this is typically a small amount of fluid, the problem is significant when pumping caustic, corrosive, or otherwise dangerous fluids.
In addition to process fluid being used to lubricate the seal faces, mechanical seals are often very sensitive to process upsets or deflections of the shaft. System conditions such as pump or compressor cavitation can cause the shaft to deflect along its rotational axis. This can in turn cause the seal surfaces to separate and allow significant leakage.
In instances where hard but brittle materials such as Silicon Carbide are utilized for seal faces, impact of the seal faces against one another during upset conditions can cause cracking or shattering of the seal faces.
Upset conditions can also cause radial deflections of the shaft, leading to sealing surface misalignment, uneven loading, and potential failure of the seal.
Often, double mechanical seal arrangements are utilized for critical equipment. Costly, bulky, and heavy bearing frame assemblies are often utilized to help minimize shaft deflections that mechanical seals are sensitive to.
When a mechanical seal fails, the fluid within the housing can leak to the atmosphere or into the bearing frame assembly. This can cause significant injury to personnel, violate environmental regulations, violate occupational safety regulations, and damage surrounding equipment.
A need exists for a cost efficient leak resistant pump with mechanical sealing system for preventing the leakage of a fluid to the atmosphere.
A further need exists for an improved leak resistant pump wherein upon a failure, leakage can be directed through a drain to a safe containment area, activate a shut-down of the equipment, or an alarm.
The present embodiments meet these needs.
The present embodiments are detailed below with reference to the listed Figures.