Pump balance disc

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The pump balance disk is a device used to counteract the axial force of the pump. When the pump is in operation, there is always pressure from the outlet side toward the inlet side; to alleviate this pressure and reduce wear, a balance disk is installed during pump design in order to minimize this force. What is a water pump balance disk? The balance disk functions like a floating liquid-lubricated bearing, allowing it to move along with the rotor (in pumps equipped with a balance disk mechanism, the bearings at both ends do not restrict axial movement). Unlike a balance drum, it is capable of automatically balancing axial forces, and this is due to the complementary nature of the two gaps in the balance disk. Currently, in the use of high-pressure, high-head feed water pumps, double-shell pumps are widely applied due to their stable operation and ease of maintenance. Below, the role, measurement, and adjustment of the clearances in various parts of the pump are briefly explained in conjunction with the maintenance process of the double-shell feed water pump. The leakage rate of the balance disc is very high; for ordinary water pumps, it is 4% to 10% of the pump’s designed flow rate, while for pumps with high head and low flow rates, this figure can reach up to 20%. After wear over time during operation, the leakage rate increases further. Factors affecting the leakage rate of the balance disk: (1) For a fixed balance disk, the larger the value, the greater the leakage rate ； (2) The pump operates in the low-flow range, resulting in an increased leakage rate ； (3) When b1 is large, the leakage amount is high ； (4) High leakage rate at L1 hour ； (5) An increase in b2 leads to a larger leakage volume. When the balance disk is positioned too far backward, its end plane is no longer perpendicular to the axis line; this results in a gap forming between the balance disk and the balance ring after assembly, preventing the axial thrust from being balanced and causing the balance disk to wear out and leading to motor overload. Therefore, tilt measurement must be performed on all pumps equipped with a balance disc. Among the maintenance of all water pumps in power plants, feed water pumps require a high level of technical expertise due to their large number, high pressure, and high rotation speeds. During the maintenance of feed water pumps, while ensuring that there are no defects in the moving and stationary parts of the pump, the quality of such maintenance relies entirely on the accurate measurement and adjustment of the clearances. Among the numerous gaps and maintenance data related to water pumps, each gap and piece of maintenance data does not exist in isolation; rather, they are interconnected and influence one another. The value for each gap is determined by the manufacturing and operating requirements of the water pump.