接触式机械密封寿命预测方法

Predicting seal life for contact mechanical seals

依据分形理论,用具有尺寸独立性的分形参数表征包含粗糙度和波度的密封端面形貌及其变化,研究了机械密封端面形貌变化对泄漏通道的影响规律,结合Navier-Stokes方程,建立了基于允许泄漏率的机械密封寿命预测方法。运用这一方法,对工作在柴油泵中的108型机械密封进行了寿命预测。研究发现密封介质压力为0.8MPa,端面比载荷为1.1MPa,工作11500h的108型机械密封,软质环端面形貌D=1.5607,G=2.0298×10-9m,理论泄漏率为2.95cm3·h-1。此时,其工作时间已超出美国石油学会和美国摩擦学家与润滑工程师学会制定的易挥发物逸出量控制标准下的密封寿命1400h,处于危险状态。结果表明,正确预测机械密封寿命是十分必要的。机械密封寿命预测方法的建立,为确定维修周期、保证设备安全可靠运行提供了依据。

Based on the fractal geometry theory, the surface topography including surface roughness and waviness of the end faces of the sealing rings and its change during the frictional wear of mechanical seals were characterized by the fractal parameters with independent dimension. The effect of change of surface topography on leakage path was analyzed. A permissible-leakage-rate-based method of predicting seal life of mechanical seals was developed by using Navier-Stokes equation, and the seal life of a 108 mechanical seal in diesel oil pump was predicted by this method. The 108 mechanical seal worked for 11500 h in 0.8 MPa diesel oil when the pressure on seal face pg was 1.1 MPa, the fraetal dimension D was 1. 5607, scale amplitude G was 2. 0298× 10^9m, and the calculated leakage rate Q reached 2.95 cm^3· h^-1. The seal life exceeded 1400 h as calculated for volatile matter permissible leakage given in API and STLE and the mechanical seal was in dangerous state. The research results indicate that accurately predicting seal life of mechanical seals is essential. The method of predicting seal life of mechanical seals put forward in this paper can be used to make scheduled maintenance and achieve safe, reliable service of mechanical seals.