Mechanical seal requirements for elastic components-
Mechanical seal requirements for elastic components:
The elastic elements in modern mechanical seals mainly include springs and bellows. Their functions have been described above. There are various types of springs such as cylindrical spiral springs, disc springs, wave springs, rectangular springs and metal diaphragm springs, among which cylindrical spiral springs are the most used. Taking cylindrical spiral spring as an example, the following issues should be paid attention to in the design:
(1) Spring pressure: The specific pressure of the spring should be selected correctly according to the specific working conditions and purposes.
(2) Spring material: not only the strength and elasticity should be considered when choosing, but also the corrosion and fatigue properties should be considered.
(3) When the shaft diameter is less than 70mm, a concentrated large spring can be used (in order to shorten the axial distance, generally only springs with a small number of turns and a large pitch are used to make the spring pressure uniform and not affected by centrifugal force. Larger ones can use small springs evenly distributed at multiple points in the circumferential direction.
(4) Both ends of the spring must be perpendicular to the axis. In order to ensure that the supporting surface is perpendicular to the center line, and the spring force is uniform, there must be no less than 3/4 of the parallel support ring at each end, and the end surface should be smoothed. The surface roughness should not be less than and the two ends should be parallel. The position should be staggered.
(5) The working compression of the spring should be 2/3~3/4 of the ultimate compression.
(6) When the soft-ring wear-bearing protrusions are all worn, the spring specific pressure should not change much. The rule of thumb requires that the specific pressure of the spring should not be reduced by more than 18%~20% at this time.
(7) In order to ensure that the spring force does not decrease much when the soft ring is worn, the single spring adopts a spring with a small number of turns and a large pitch.
(8) When using a parallel spring drive, pay attention to the rotation of the spring and the rotation of the shaft. Looking at the spring from the static ring side, right-handed springs should be used when the pump shaft rotates to the right; left-handed springs should be used when the pump shaft rotates to the left.
(9) A spring-loaded push-ring seal is used. It should be noted that as the medium pressure increases, the load factor (area ratio) of the seal decreases.
(10) When the diameter-to-length ratio of the cylindrical small spiral spring is too small, the stability may be lost due to the spring flexibility exceeding the limit value, and each small spring can be sleeved on the guide pin.
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