DESMI PUMPING TECHNOLOGY A/S P a g e | - 53 -Tagholm 19400 Nørresundby - DenmarkPhone.: +45 96 32 81 11Fax : +45 98 17 54 99E-mail: desmi@desmi.comwww.desmi.com17.1 Adjusting the soft shaft sealThe shaft seal must not be adjusted during operationIt is important that the soft shaft seal leaks during operation, as this provides lubrication andalso releases the frictional heat that is generated.The shaft seal with packing coil requires continuous adjustment, to make sure that the volumeof leakage by the stuffing box is correct.Depending on the speed, pressure, pump size and viscosity, the stuffing box must leak 10-100drops per minute to remove the frictional heat that is generated between the shaft and thepacking rings. If there is insufficient leakage, the heat generated can cause the gasket rings toharden and create increased wear on the shaft.The leakage described above is achieved by tightening the packing rings axially, so that theyapply a pressure against the shaft. This pressure restricts the flow of the liquid, as the playbetween the shaft and the packing ring is in the order of a few thousandths of a millimetre. Softshaft seal:Figure 35:The location of the soft shaft seal, the shaft seal casing and the packing gland on the pump.The design of the shaft seal casing, does, however, depend on the individual pump application.
