Pump packing

Many industrial pumps around the world still use ring packing as the shaft seal. These packings require continual maintenance. They need to be tightened and adjusted and it is necessary to change them frequently. Packings wear and damage the shaft or sleeve of the pump, which necessitates their frequent replacement. The leakage from the packing gland corrodes the pump, base plate and foundation. The drips can enter into the bearings and contaminate the bearing lubricant. This sacrifices the life of the bearings.

The majority of existing pumps that were originally designed for packings can be converted to use mechanical seals. Consider the following. We have many pumps in our private everyday lives. Practically all are adapted to mechanical seals. The family car has about 6 pumps with mechanical seals:

■ The radiator water pump.

■ The power steering pump.

■ The pump that sprays and cleans the windshield.

■ The air conditioning compressor.

Do you have two cars? Then you have about 12 pumps with seals. And in your house, how many sealed pumps do you have? In the kitchen, mechanical seals are on the pump in the dishwasher, the blender, the refrigerator compressor, and the garbage disposal under the sink. Do you have a clothes washer? There are two seals on the clothes washer, one on the pump that fills and drains the washer, and another seal on the agitator shaft. How many drips are on the laundry room floor?

AUTHOR'S NOTE

Does your house have air conditioning, or a heat pump? Do you have solar heating, a Jacuzzi bath, swimming pool, aquarium, solar heating, a roof mounted water storage tank, a well, a power assisted commode, a motorboat, a jet ski, ATV or camper? Then you have even more mechanical sealed pumps. We have mechanical sealed pumps in practically all facets of our everyday life, and these pump seals last for years without problems.

The environmental laws favor mechanical seals over packings. The need to conserve energy favors mechanical seals. The needs to reduce labor costs and consumption of natural resources favor the mechanical seal over packings.

The majority of pump manufacturers offer their products with standard or optional mechanical seals. The mechanical seal manufacturers make seal models designed to substitute packings. The majority of pumps can be converted to mechanical seals without machining or design change. And still other pumps can be converted to mechanical seals with a slight design adjustment that doesn't affect flow or head. The conversion to a mechanical seal improves the pump's efficiency. The cost of the seal and die labor to convert the pump will be returned in reduced operating costs in just a few months.

The mechanical seal runs in the same space previously occupied by the packing rings (Figure 13-1 and Figure 13-2, next page).

The mechanical seal on the radiator water pump of your car has to work under severe conditions. This seal must resist the pressures and temperatures, corresponding to the velocities of the motor, and the variable operating times. This seal is not a precision seal (it has stamped parts rather than machined components) and the pump is a portable pump. The pump doesn't use a direct coupling but a v-belt pulley with radial loading. The seal must resist many vibrations commencing with the v-belt slapping and whipping.

The seal must also resist the vibrations from the explosions of internal combustion in the engine, chassis and wheel vibrations, and even potholes in the road. This seal must resist strong chemicals (anti freeze, anti-rust agents, radiator stop-leak and sealant chemicals, gasoline and lubricant residuals), and also solid particles (rust, iron slag, minerals, asbestos fibers, and silica from the engine casting mold). In spite of all this, the mechanical seal on the water pump of your car can run 7, 10, even 15 years without problems.

Figure 13-1

Figure 13-2

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