升降机的密封件是液压升降机中很重要的一个零件，是防止流体或固体微粒从相邻结合面间泄漏以及防止外界杂质如灰尘与水分等侵入机器设备内部的零部件的材料或零件。升降机的密封件虽小，但是它在升降机中的起的最用很大。 选择升降机设备密封圈时应该考虑哪些因素呢？

1、压力
压力的高低，移动式升降机压力循环周期变化的长短，对密封件损坏有很大的影响。压力越高，其它的因素对密封件的性能影响越大，如温度，速度，密封件的材料，活塞和缸筒之间的间隙，活塞和缸头之间的间隙。　　 
High and low pressure, pressure cycling mobile lift cycle length, has a great influence on the seal is broken. The higher the pressure, the greater the influence of other factors on the performance of the seal member, the gap clearance, such as temperature, speed, material for the sealing member, the piston and the cylinder between the piston and the cylinder head.

2、温度
一种密封件材料的最高使用温度和最低使用温度进行描述是比较困难的，对于活塞和活塞杆的工作温度都不同，要对它们进行区别选择。
The maximum temperature of a seal material and the lowest temperature is more difficult to be described, the piston and piston rod operating temperatures are different, to distinguish them selected.

3、摩擦力
密封件和密封表面的摩擦力取决于很多因素：表面粗糙度，表面的特性，压力，介质，温度，密封件的材料，密封件的型式和运动速度。
Friction seals and the sealing surface depends on many factors: the type and the motion velocity of the surface roughness properties of the surface, the pressure, the material medium, temperature,the sealing member, the sealing member.

4、表面
液压升降机油缸活塞和活塞杆表面的特性对密封件的寿命有着非常大的影响。表面特性常用表面粗糙度Ra的值来定义，Ra是表面形状偏离中心线绝对值的算术 平均值。但些数值并不能完全表示表面情况对密封件的影响，这是因为即使在同样的粗糙度下，不同的表面形状特征可以导致对密封件不同程度的密封件磨损。
Characteristics of the hydraulic lift cylinder piston and piston rod surface has a very big impact on the life of the seal. Surface characteristics of the common value of the surface roughness Ra is defined, Ra is the arithmetic average deviation from the center line of the surface shape of the absolute value. However, these values ?do not fully represent the impact on the surface condition of the seal, this is because even under the same roughness, the surface shape of the different features may lead to different levels of the sealing member seals wear.