升降機的密封件是液壓升降機中很重要的一個零件，是防止流體或固體微粒從相鄰結合面間泄漏以及防止外界雜質如灰塵與水分等侵入機器設備內部的零部件的材料或零件。升降機的密封件雖小，但是它在升降機中的起的最用很大。 選擇升降機設備密封圈時應該考慮哪些因素呢？

1、壓力
壓力的高低，移動式升降機壓力循環周期變化的長短，對密封件損壞有很大的影響。壓力越高，其它的因素對密封件的性能影響越大，如溫度，速度，密封件的材料，活塞和缸筒之間的間隙，活塞和缸頭之間的間隙。　　 
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、溫度
一種密封件材料的最高使用溫度和最低使用溫度進行描述是比較困難的，對于活塞和活塞桿的工作溫度都不同，要對它們進行區別選擇。
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決于很多因素：表面粗糙度，表面的特性，壓力，介質，溫度，密封件的材料，密封件的型式和運動速度。
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
液壓升降機油缸活塞和活塞桿表面的特性對密封件的壽命有著非常大的影響。表面特性常用表面粗糙度Ra的值來定義，Ra是表面形狀偏離中心線絕對值的算術 平均值。但些數值并不能完全表示表面情況對密封件的影響，這是因為即使在同樣的粗糙度下，不同的表面形狀特征可以導致對密封件不同程度的密封件磨損。
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.