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how to grasp the essentials of mechanical seal technology
Mar 01, 2018

1. Basic concept of mechanical seal:

Mechanical seal means a device for preventing fluid leakage consisting of at least a pair of end surfaces perpendicular to the axis of rotation, under the action of fluid pressure and compensation mechanism elasticity (or magnetism), and with the aid of sealing to maintain a combination of relative sliding. The auxiliary seal of the compensating ring is called bellows mechanical seal.

2. Mechanical Seal Composition:

There are mainly the following four types of components. A. Main seals: dynamic ring and static ring. B. Auxiliary seals: Seals. C. Compact parts: Spring, push ring. D. Transmission parts: Bouncing seat and key or fixed screws

3. Mechanical seal work should pay attention to the problem:

1. Precautions for installation

A. Be careful to avoid installation deviations from installation

(1) Tighten the gland should be found after the coupling, bolts should be evenly on the support to prevent the gland face deflection, with Feeler check each point, the error is not greater than 0.05 mm.

(2) Check the gland and shaft or sleeve diameter of the matching clearance (that is, concentricity), evenly around, with feeler check each point tolerance is not greater than 0.01 mm.

B. Spring compression should be carried out in accordance with the provisions, not allowed to have too large or too small phenomenon, required 2.00 mm error. The General Assembly increases the end-face pressure, the other speed end face wear. Too small can cause less than pressure and can not play a sealing effect.

C. Dynamic ring installation After the beard to ensure that the axis of flexible movement, the dynamic ring pressure to spring should be able to automatically bounce back.

2. Precautions for demolition

A. In the removal of mechanical seals to be careful, strictly prohibit the use of hammer and flat shovel, so as not to damage the sealing elements. Can do a pair of wire hooks, in the direction of self-financing into the drive seat gap, the sealing device pull out. If the scaling is not removed, should be cleaned and then removed.

B. If at both ends of the pump with mechanical seals, in the assembly, demolition process to take care of each other, to prevent the other.

C. For the mechanical seals that have been run, where the gland is loose so that the seal is moving, the static and dynamic ring parts must be replaced and should not be tightened for further use. Because in the sample after the movement, the friction pair of the original trajectory will change, the contact surface sealing is very vulnerable to damage.

Three. Machine seal normal operation and maintenance problem:

1. Pre-start preparation and precautions

A. Comprehensive inspection of mechanical seals, as well as the installation of ancillary devices and pipelines are complete, whether meet technical requirements.

B. Mechanical seals before the start of the static pressure test to check whether the mechanical seal leakage phenomenon. If leakage is more, should find out the reason to try to eliminate. If it is still not valid, you should remove the check and reinstall it. General static pressure test pressure with 2~3 kg/cm.

C. Press the pump to the disc to check whether it is brisk and even. If the car is struggling or not moving, you should check the assembly size is wrong, installation is reasonable.

2. Installation and outage

A. Keep the sealed cavity filled with liquid before starting. For the transport of solidified media, the use of steam to heat the sealing chamber to melt the medium. The car must be parked before starting to prevent the soft ring from breaking up suddenly.

B. For the use of the pump oil seal system of mechanical seals, should start the oil seal system. Stop the oil seal system at the end of the stop.

C. Hot oil pump After the shutdown can not immediately stop sealing the oil cavity and end of the cooling water, should be sealed at the end of the oil temperature down to 80 degrees below, can stop cooling water to avoid damage to seal parts.

3. Operation

A. If there is a slight leakage after the pump starts, it should be observed for some time. If the continuous operation of 4 hours, leakage is still not reduced, you should stop pump inspection.

B. Pump operating pressure should be smooth, pressure fluctuation is not less than 1 kg/square centimeter.

C. Pump in operation, should avoid the occurrence of the phenomenon, so as to avoid the sealing surface of dry friction and seal damage.

D. Seals should be checked regularly. In operation, when its leakage exceeds the standard, the heavy oil is not more than 5 drops/min, light oil is not greater than 10/min, such as 2-3 days there is no improvement trend, it should stop pump bolt check sealing device.

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