Following on from last week’s blog, we present our second blog with tips for correctly installing compression packing. These tips are invaluable for correctly installing compression packing and achieving a trouble-free startup.
Tip #4: Correctly cut the packing rings.
Correctly installing compression packing means cutting packing rings with the right technique and the right tools. Packing rings may be cut in one of two ways: on a 70° angle or on a 45° angle. Experienced cutters know that cutting on a 45° angle usually yields the best results. In addition, making an axial, as opposed to a radial cut, generally produces a superior seal of the medium. Finally, use of a packing cutter will usually produce better results than that obtainable from using a knife.
Tip #5: Correctly insert the rings into the stuffing box.
When inserting the rings into the stuffing box, a common mistake is to incorrectly position the rings. Care should be taken to insert the packing ring with the joint first. The correct end of the rings should also be placed at the top, rather than at the bottom. Each ring should be firmly pressed down, and care should be taken to stagger the joints appropriately.
Tip #6: Pre-compress the rings before startup.
Before the equipment is started, the entire ring set should be pre-compressed to seat the rings in the box, eliminate possible hollows or gaps, and close the joints properly. For rotary pumps, the gland should be tightened just enough to compress and seat the rings.
Tip #7: Follow the correct startup procedure.
Correctly installing compression packing requires a good startup procedure. Following a good startup procedure can significantly affect the life of the packing. When the pump is started, the medium will enter the stuffing box through the gap at the bottom and exert an upward (axial) pressure on the packing rings which are blocking its way. This axial medium-pressure gets converted to radial pressure which causes the packing rings to press against the stuffing box body and the shaft. This pressure automatically reduces the initial leakage.
Medium pressure by itself can usually reduce the leakage to the desired level. Therefore, the bolts may have to be loosened a little until sufficient leakage is restored. If, however, the leakage rate is too much once the rings have settled, the bolts can be retightened until the leakage is reduced to an acceptable level.
It is important to remember that some leakage is necessary and actually beneficial. Too little leakage causes unnecessary friction and heat build-up, which can destroy the packing or at least shorten its life.
Following the tips for installing compression packing in these two blogs can help you achieve superior sealing performance and extend packing life. Canada Rubber Group Inc. (CRGI) supplies high quality compression packing manufactured by Teadit.
For more information on the packing styles we can supply, please contact our sales department at email@example.com.