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How To Correctly Install A Single-end Mechanical Seal?
May 03, 2018

How to correctly install a single-end mechanical seal?


The installation sequence of the mechanical seals can be installed in a certain order after the installation preparation is completed. The installation of the stationary parts in the end caps and the installation of the rotating parts on the shafts are completed. Finally, the overall assembly of the seals is completed. Take the single end face built-in unbalanced mechanical seal used in the centrifugal pump shown in Figure 1 as an example. The installation sequence is as follows:

1. Installation of stationary parts

Insert the anti-rotation pin (1) into the corresponding hole in the seal cap, and then insert the static ring auxiliary seal ring (2) from the tail of the stationary ring (3). If using a V-ring, pay attention to its installation direction. If it is an O type Circle, don't scroll. Then align the anti-rotation pin on the back of the stationary ring with the anti-rotation pin into the sealing end cap. The height of the anti-rotation pin should be appropriate, and the gap should be 1~2mm with the static ring. Do not top the static ring. Finally, the distance A from the end of the stationary ring to the end surface of the sealed end cap is measured. After the static ring is installed in the end cap, the verticality of the seal end face and the center line of the end cap and the flatness of the seal end face shall be checked. For the pump conveying liquid hydrocarbon medium, the verticality error is not more than 0.02mm, and the medium such as oil can be controlled within 0.04mm.

2. Determine the mounting position of the spring seat on the shaft

The installation position of the spring seat should be determined on the basis of adjusting the relative position of the rotary shaft and the seal chamber housing. First draw a reference line correctly on the pump shaft along the face of the seal chamber. Then, according to the sealed working length marked on the seal assembly drawing, the spring is adjusted by the positioning dimension of the spring seat.


The amount of compression to the design specification. The positioning dimensions of the spring seat (see Figure 1) can be derived as follows: B = L - (A + S) where:

B—distance from the back face of the spring seat to the reference line

L—the total height of the working position of the rotating part, L=L’—H;

H - spring compression

A—The distance from the static ring end face to the end cover end face after the stationary ring assembly is installed in the sealing end cap;

S - seal end cap gasket thickness.

3. Assembly of rotating parts

Both ends of the spring (8) are respectively put on the spring seat (9) and the push ring (7), and the two ends of the flattened spring are pressed against the planes on the spring seat and the push ring. Then, the auxiliary ring (5) of the moving ring is inserted into the moving ring (4), and is integrated with the pushing ring, and then the assembled rotating part is put on the shaft (or the shaft sleeve) so that the spring seat back end surface Align with the specified position, tighten the screws (10) evenly several times, and press the ring backwards by hand to see if it can float axially.

4. Static component assembly

The sealed end cap installed with the stationary part is mounted on the sealed cavity, and the end cap is evenly pressed. The gap between the end cap and the end face of the sealing cavity may not be installed with a feeler gauge, and the error is not more than 0.04 mm. Check the radial clearance between the end cap and the stationary ring against the shaft, the error along the circumference of each point is not more than 0.1mm.


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