Why is pump packing important

Over time, loss of the lubricant and wear of the packing rings contribute to gradual decreased effectiveness, leading to the need to replace the packing. The choice of packing material affects the operating costs of centrifugal pumps, but little is known about the relationship. The acronym "STAMPS" can be used to remember key considerations that can determine which packing material and construction should be selected:.

S Size — What are the stuffing box dimensions? T Temperature — What is the temperature of the medium? A Application — What type of equipment is it? M Media — What medium is being sealed? P Pressure — What is the internal pressure being sealed? S Shaft speed — What is the surface speed of the shaft? One common mistake is the tendency to maximize the packing's time in service to a perceived point of failure before replacing it. Defining failure is more a matter of opinion than science.

Signs that the packing has failed include increased leakage, smoke at the stuffing box or uncontrolled leakage at the gland. Safety-conscious operators service the pump and replace the packing at regular intervals. However no common criteria for determining the replacement frequency or relating it to the packing material are available.

An acceptable replacement cycle time is heavily dependent on the application, the equipment and the packing. The confusion occurs because of the forgiving nature of compression packing.

Pump operation is not impaired until the packing fails. It should be replaced long before this occurs. If a replaceable sleeve were not fitted, the shaft would need to be replaced or rebuilt in the worn area.

This would be both expensive in terms of spares holding or extended downtime while shafts are repaired. If a separate wear sleeve is fitted there is the cost of holding a spare in stock but there is an underlying danger that the shaft diameter under the sleeve has been greatly reduced to allow for fitting, considerably reducing the shafts resistance to bending.

Broken shafts are not uncommon and are generally caused by fatigue due to the constant bending of the shaft under operation. How does this happen? Running the pump away from its Best Efficiency Point, against throttled or closed discharge valves, over its designed capacity; long shaft overhang and stop-starting create massive forces within the volute. Shaft sleeves can also be notoriously difficult to remove.

This can be extremely time consuming and may even lead to damage of the shaft itself. Gland packing often requires the supply of a clean flushing medium to the lantern ring. This was originally done to prevent the ingress of air into a system under vacuum and was also found to cool the packing as it generated friction against the shaft.

The costs here are the supply of the flush, the leakage of the flush to atmosphere and the dilution of the product itself. This dilution may be acceptable or costs may be incurred in the removal of the dilutant at a later stage in the process.

No product dilution with mechanical seals means a better quality product and no additional costs to remove the dilutant. To ensure that packing operates as efficiently as it should it requires constant attention.

Too loose and leakage rates are unacceptable, too tight and the packing can burn out on start up, increasing leakage, wear on the shaft or sleeve and increasing power consumption. When packing is compressed, it squeezes tightly around the shaft sleeve causing additional drag on the shaft. Knowing the names of different centrifugal pump parts, and their functions, is critical to proper pump maintenance and operation.

Take the time to educate yourself and your team on all components to lessen maintenance downtime and keep pumps running efficiently. Trouble with pump packing? Ask us about it! We gladly provide technical assistance to businesses and municipalities in Wisconsin and upper Michigan. Skid Systems. Sanitary Cleaning Systems. Heat Exchangers. Skid System Packages. Skid Systems By Market. Success Stories. Skid System Store. Skid System Repair Services. Emergency Repair.

John Crane Seal Repair. Root Cause Analysis. Skid System Refurbishment. Replacing packing The most common sign that packing needs replacement is excessive leakage from the back of the stuffing box. Removing packing To remove packing, follow these steps: Obtain personal protective equipment PPE prior to service, since slurries can be chemically hazardous.

Identify the type of stuffing box for the packing and lantern ring position details. Shut down and lock out the pump. Allow the pump to cool prior to servicing! Valve off or drain the slurry from the sump tank and discharge pipe. Remove the seal guard and gland adjustor. Using a packing ring removal tool or other device, remove the packing and lantern rings.

Installing new packing To install new packing, follow these steps: Apply synthetic assembly lube to the replacement packing. Wrap the packing around the shaft sleeve. Stagger the ring joints. Use a blunt tool to lightly tap each packing ring in place.