Here is a look at how and when to replace packing, as well as why doing it correctly is so important. Like any other part of a slurry pump, packing material is subject to wear over time and requires regular inspection and replacement. In order to avoid issues with the stuffing box, operators should know the expected lifespan of its packing material. First, operators should know whether or not the packing material is the right one for their application; for this, they can consult the manual that came with their pump.
Second, the lifespan depends on whether or not the seal water system is properly designed. Seal water should be 10 psig 0. Solids should be less than ppm and 50 microns thick. If operators maintain the sealing system at those conditions and check the packing on a weekly basis, they can expect a lifespan of six to twelve months. The most common sign that packing needs replacement is excessive leakage from the back of the stuffing box.
The leakage will likely be cool to the touch and cloudy. In addition, the amount of leakage dripping from the bottom of the box will be noticeably larger than the size of a pencil. You may see spraying or gushing at the site of the leak. If packing is in good condition and properly tightened, exiting water will be at a temperature that is comfortable for handwashing, roughly F 46 C. Operators may also notice that the gland adjustor is bottomed out; this is another sign of worn packing.
Finally, if operators notice that the packing rings have reached their maximum compression state, they should replace them right away. Although the process for removing and replacing packing is relatively simple, it is essential that operators follow the directions carefully to avoid improper installation.
Running rotating equipment with packing in the stuffing box is like driving your car with the hand brake on. Would this affect your fuel consumption?
Of course it would and so packed glands therefore greatly increase power costs. In some cases pumps can be made to run at a lower speed and efficiency, increasing costs still further.
The single major cause of bearing failure in rotating equipment is contamination of the lubrication. In a study conducted by Mobil Oil it was discovered that water contamination of 0. This is the equivalent of 2 drops of water in a litre of oil. Packing leaks by design and is in close proximity with the bearings. This subjects the bearings to a constant stream of leakage and contamination. No leakage equates to longer bearing life and less downtime costs.
Many mechanical seal failures are attributed to excessive shaft movement caused by failed bearings. Most rotating equipment is fitted with repairable wear sleeves in the region of the gland packing to adress the fact that packing is designed to wear the shaft in this area.
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. Skid System Store.
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