The Effect of Size and Material of Packing Seal and Pump Flow Rate to Leakage Rate at Stuffing Box of Centrifugal Pump

Abstract

This research explore on the effect of size and material of packing seal and discharge valve opening to the leakage rate at stuffing box for pump P7301-A. Leak at stuffing box is unavoidable due to gap exists between the pump casing and shaft. Therefore, it is necessary for a suitable sealing system which includes packing size and material to be installed on all pumps for controlling the leakage rate without damaging the pumps. It is also important for operator to know the proper discharge valve opening at which the pump should be operated to get minimum leakage. Experiment was conducted by recording the leakage volume at stuffing box with changes of size (9mm, 10mm and 11mm) and material (graphite, polytetrafluoroethylene (PTFE) and PTFE-Asbestos) of packing seal and discharge valve opening (50%, 75% and 100%) that would determine the pump flow rate. The experiment was executed and analyzed using one factor at a time (OFAT) method whereby the testing of factors conducted one at a time instead of multiple factors simultaneously in determining which setting would lead to the lowest leakage rate without compromising the pump’s healthiness. Feasibility analysis was also conducted on the operating cost focusing on saving in utility bill and maintenance cost that focused on painting and fitting replacement works. Result from experiment and analysis showed that packing seal size and discharge valve opening have effect on leakage rate at stuffing box while material of packing seal is not significant in influencing the leakage rate of this pump. Larger size of packing seal would cause lower leakage rate due to greater obstruction at stuffing box. Leakage rate also declined when the discharge valve was fully opened due to less resistance created at the discharge line had reduced the pressure in the pump casing which led to less leakage at stuffing box. Feasibility analysis showed cost saving of RM5,930.00 on the operating cost and cost saving of RM221,200.00 on the maintenance cost for 10-year operation of 10 pumps can be achieved. Outcome from this study can be utilized to reduce the plant operating cost, maintenance cost, manhours saving and preserve the treated water resources.