Mechanical seals introduce

Mechanical seals are one of the basic mechanical components of precision and complex structure, is a key component of all kinds of pumps, reaction kettle, turbine compressor, submersible motors and other equipment. The sealing performance and service life depends on many factors, such as selection, machine precision, correct installation etc..

Basic knowledge of mechanical seals

1, the basic concept of mechanical seal:

The mechanical seal is defined by at least a pair of end faces perpendicular to the axis of rotation of the fluid pressure and the elasticity of compensation organizations (or force) the role of the device and auxiliary seal with maintaining relative sliding postmerger and constitutes to prevent fluid leakage. Auxiliary compensating ring seal for metal bellows called bellows mechanical seal.

2, mechanical seal:

There are four main parts. A.: the main seal movable ring and the static ring. B. auxiliary seal: seal ring. C.: pressing spring, push the ring. D. drive: Bomb Kei seat and a key or a fixed screw.

Should pay attention to the problem

1, installation precautions

A, we must pay great attention to avoid the installation deviation generated during installation

(1) to tighten the gland should be aligned in the coupling bolts should be uniform, to prevent the end cap oblique, with feeler check, the error is less than 0.05 mm.

(2) clearance check the gland and the shaft or shaft diameter (i.e. concentricity), around to evenly, not more than 0.01 mm check with the feeler the tolerance.

B, the amount of spring compression according to the regulations, there are too large or too small phenomenon does not allow the error of 2 mm. The increase of the surface pressure, the other end wear rate. Is too small will cause less than the pressure to play the sealing role.

C, ring after installation to ensure beard can move flexibly on the shaft, the moving ring pressure to the spring should be able to automatically bounce back.

2, the demolition notice

A, in the disassembly of mechanical seal carefully, prohibited the use of hammer and chisel, so as not to damage the sealing element. To do a pair of wire hook, in the direction of self financing gap into the driving seat, the sealing device is pulled. If not remove fouling, should be cleaned after removing.

B, if both ends in the pump with mechanical seal, take care of each other in the assembly, the disassembly process, prevent the care for this and lose that.

C, to run the sealing machine, where the sealing gland loose move, then the dynamic and static ring parts must be replaced, should not continue to use re tightening. Because in the kind of dynamic friction Ying, the original orbit will change, the contact surface of the seal is very vulnerable to damage.

Mechanical seals The normal operation and maintenance

1, before the start of the preparatory work and the matters needing attention

A, a comprehensive inspection of the mechanical seal, and ancillary equipment and pipeline installation is complete, compliance with technical requirements.

B, mechanical seal before the start of the hydrostatic test, check the mechanical seal leaks. If the leakage is more, should identify the reasons to eliminate. If still valid, you should remove and reinstall the check. The general static pressure test pressure of 2~3 kg / cm2.

C, according to the pump rotate to turning check whether a uniform. Such as turning demanding or not move, it should check whether the assembly size error installation is reasonable.

2, installation and outage

A, before the start should be kept sealed cavity filled with liquid. To deliver solidified medium, the application of steam seal chamber heating melt medium. Before the start must be turning in order to prevent the sudden start caused by soft ring fragmentation.

B, for the use of pump oil sealing system of the mechanical seal, the sealing oil system should be the first to start. Finally stop the seal oil system of parking.

Can't stop cooling water sealed oil chamber and seal C, hot oil pump after the shutdown, should be the end seal oil temperature dropped to 80 degrees below, can stop the cooling water, so as not to damage the sealing parts.

3, operation

A, after the pump is started if there is a slight leakage phenomenon, should be observed for a period of time. Such as 4 hours of continuous operation, the leakage is not reduced, it should stop the pump check.

B, the operation of the pump pressure should be smooth, the pressure fluctuation is not greater than 1 kg / cm2.

C, the pump is in operation, should avoid the evacuation phenomenon, so as to avoid damage to the sealing surface and seal dry friction.

D, always check the sealing condition. In operation, when the leakage exceeds the standard, heavy oil is less than 5 drops per minute, the light oil is not greater than 10/, such as 2-3, still no improvement trend, should stop the pump check sealing device.

Seal "in the development of our country has a long history, the ancients had to do with the mechanical seal of water extraction of cotton, hemp fiber, and abroad until 1782 to use the packing. The importance of the seal, here is not to say, now have already appeared in academic research law, seal sealing technology design and application of the principle of scientific equipment - "seal", scientific research institutions also have professional courses devoted to the study of seal, but in our country, so far as I know, there are fluid mechanics and the hydraulic transmission course in the University, but also there is no special research on sealing seal system, compared with foreign research level so we still have the gap.

Seal design of the professional field very much, in addition to materials and machinery, and mechanical (including fluid mechanics, boundary layer theory and so on), tribology, automatic control etc.. So on the seal, the research difficulty is relatively large. The sealing industry level, personally think that the gap between foreign countries should be not less than 50 years.

A sealing mechanism

Want to learn the seal, you must first understand the understanding of the principle of leakage, leakage, the corresponding sealing mechanism is. There are three kinds of leakage:

One is the leakage, that is the gap between the sealing surface leakage

The two is leakage of fluid which is sealed by the sealing material of the capillary leakage

The three is spread, refers to the difference in concentration under the action of sealing medium by capillary gap or material occurrence of mass transfer.

A sealing method

There are several - sealing method

1 minimize set seal parts

2 blocking and isolation

3 extraction or injection

4 the increase of leakage resistance

5 additional work elements in the channel

6 kinds of combination sealing method

The common seal form

Gasket seal, packing seal, mechanical seal, non contact seal and injecting pressure seal is a common seal form. The packing should be regarded as the most common, it also includes the soft packing seal, packing seal and packing seal molding hard. We include the O ring, Y ring and common seal packing seal molding etc.. Non contact type seal including clearance seal and labyrinth seal, floating seal, dynamic seal, magnetic fluid seal and fully enclosed seal.