A clean water flush should be provided before and after start up for 5 to 10 minutes changing to flush from discharge during normal running. Water should be available at a flow rate of 5 to 10 l/min (1.5 to 2 gallons).
Pre-Start Up Procedure
Ensure that the springs are evenly adjusted to give about 1/4 of their full load. It should be noted that the figure given here is a guide figure and as such will probably need adjustment dependent upon the particular operating conditions.
Ensure an adequate flow of flushing water 5 to 10 l/min (1.5 to 2 gallons/min) is present.
Check that the Seal Sleeve O-ring has been greased prior to Seal assembly and that the Seal Sleeve/Stuffing Box Liner cavity has also been packed with grease. This is very important to ensure proper operation of the Seal.
Seal Bedding In
Before starting up the pump, the flush system must be turned on and left turned on at all times whilst the pump is running.
Ensure that the Seal Sleeve is free to slide in the bore.
Flood the pump and start up. Adjust the springs to give the lightest load consistent with an acceptable Seal.
Overheating of Seal Faces
This is possibly the most important feature to watch for, and is indicated by one or more of the following:
- Burning smell from Seal
- Steam and/or leakage of hot water
- Alternate leakage and dry sealing possibly accompanied by burst of steam. Particular attention should be paid to this condition since it can be incorrectly diagnosed as requiring more Seal loading.
Cause of Overheating
Overheating can indicate one or more of the following:
Q: Sealing faces are starved of water.
A: Examine flushing system (customers supply) and locate problem.
Q: Seal too heavily loaded.
A: Reduce Seal loading to achieve an acceptable leakage level. Should the total load provided here be removed and there is no leakage, consult Sterling Mechanical Seals.
Q: Actual pressure in the Seal Chamber is not sufficient to create satisfactory lubrication of the Seal faces.
A: Reduce Seal loading to achieve “Normal Leakage” and contact Sterling Mechanical Seals regardless of leakage achieved.
The “bedding in” of the Seal will remove about 3mm from the End Seal until a full-face contact is achieved. This process could take as long as 500 hours but since every Seal is different it is very difficult to be precise on the time required to bed in or the leakage to be expected. The above is intended as a guide to assist in commissioning. It must be appreciated that during the bedding in period the End Seal is contacting on a narrow band and as such is very sensitive to changes in Seal loading. Changes in Seal loading should therefore be made with great care. At all times when changing the Seal loading, keep the load increments small and allow time for Seal to stabilize at the new load.
The loading of the Seal directly affects the life of the End Seal so careful commissioning will optimize the operating life of the Seal. It should be noted that prior to achieving a full-face contact excessive leakage from the Seal is not necessarily indicative of poor Seal performance, but leakage should be reduced as the Seal beds in to a full-face contact.
Final Adjustment After Bedding In Has Been Completed
The Seal should now be observed during all the speeds and pressures of the machine to ensure that the leakage is acceptable at all times and that no overheating occurs under any condition. If necessary the Seal loading should be adjusted to give the best overall performance of the Seal.
After the Seal has bedded in, the pressure in the Seal Chamber and the associated shaft speed together with leakage rates and final Seal loading should be recorded and reported to S M SEALS LTD.
As the End Seal wears, the spring load should be adjusted to compensate for this wear.