Operating & Maintenance
OPERATING AND MAINTENANCE INSTRUCTIONS.
NEVER RUN THE PUMP IN A DRY CONDITION, EVEN FOR A FEW REVOLUTIONS OR THE STATOR WILL BE IMMEDIATELY DAMAGED. Pumps must be filled with liquid before running. Filling plugs are provided for this purpose. This initial filling is not for priming purposes but to provide the necessary lubrication of the stator unit the pump primes itself.
When the pump is stopped, sufficient liquid is normally trapped in it to provide lubrication on starting again, but if the pump has been standing for some time or has just been moved to a new location or has been dismantled for examination, it must be filled with liquid and given a few turns by hand before starting. The pump is normally somewhat stiff to turn by hand on account of the fit of the rubber stator, but this stiffness disappears when the pump is running against pressure.
Gland Packing is carefully fitted to all pumps before dispatch, but the packing should be finally adjusted to correct sealing after the pump has been run-in. under normal pumping practice slight drip from the gland, when working under pressure, does no harm and assists lubrication of the packing. A gland drip is, however, undesirable when handling corrosive, degreasing or abrasive solutions and the gland should then be carefully tightened, whilst the pump is running, to ensure satisfactory sealing when under pressure or to stop the entry of air when under suction.
Where special gland packing or mechanical seals are specified, the manufacturer’s recommendations should be followed to prevent damage when first starting up and during the early period of operation.
If the supply of liquid to the pump suction is liable to fail, the pump can be protected against damage due to “dry running” by fitting a “snorer” or circulating by-pass. This connects the lower portion of the discharge side of the pump back to the suction passage and a small quantity of liquid to keep the stator lubricated for a considerable period. While the nozzle is designed to minimize the risk of clogging, it should be inspected occasionally to ensure that it is free from obstructions. On re-assembly, care must be taken to fit the nozzle at the delivery end of the pump.
D Range mono Pumps are normally arranged for counter-clockwise rotation (facing the driving end) which results in the branch nearer the driving end being the suction. In cases where it is essential that there should be no risk of aerating the liquid, it may be preferred to run the pump in the reverse direction so as to bring the delivery at the driving end. If this is done, reverse the barrel, barrel gasket and stator so that the stator flange is at the suction end of the pump and the barrel gasket is at the delivery end of the pump. (This does not apply to D42, D62, D72 pumps). If a by-pass relief valve and/or a “snorer” by-pass are fitted, these 2 items should also be re-fitted in the reverse direction. The nozzle of a “snorer” by-pass should always be on the delivery side.