On the mechanical seals in rotating equipment applications and troubleshooting

Abstract: a brief analysis of mechanical seals in rotating equipment applications, and the reasons for failure analysis and treatment measures.

Keywords: mechanical seal, troubleshooting, analysis}

Mechanical seals on rotating equipment is widely used, the mechanical seal seal will directly affect the operation of the machine, serious security incidents will also be significant.

Mechanical seal from the perspective of internal and external conditions affecting the sealing effect of several factors and should take reasonable measures.

A mechanical seal principles and requirements
Also known as seal mechanical seal, it is a rotating mechanical seal device, means at least one rotation axis perpendicular to the face in the liquid pressure and stretch compensation mechanism (or magnetic) effect and maintain auxiliary sealed with paste consisting of combined sliding device to prevent fluid leakage. Its main function will be easy to change the axial seal leakage is more difficult to seal leaks and it is widely used in pumps, kettle, compressors and other similar equipment rotation axis seal.

Mechanical seal is usually ring, stationary ring, composed of pressed components and sealing elements which move with the rotating ring with the shaft, ring and stationary ring sealing surface composed of tightly fitting to prevent media leaks. Ring sealed chamber by pressed to face the pressure of the liquid in the stationary ring side surface, and two ring-side surface appropriate to specific pressure and maintain a layer of very thin liquid film to achieve the purpose of sealing. compaction pressure components to enable the pump not running the state, but also to maintain end-fitting to ensure no leakage of the sealed medium, and to prevent impurities into the seal faces. sealing element and the shaft seal ring from the gap, the gap static ring and the gland's role, while the elastic element of the pump vibration, shock dampening effect of mechanical seals in the actual operation of the pump is combined with other components to run, the normal operation of the mechanical seal with its own performance, external conditions have a great relationship, but we to first ensure their own performance parts, seals and installation of auxiliary technical requirements, the mechanical seal to play its due role.

2 the performance of mechanical seal failure and the reasons
2.1 parts of mechanical seal failure of rotating equipment running them, they would often seal faces wear, thermal cracking, deformation, damage, etc., the spring will relax with a long, fracture and corrosion. Secondary seal gap will appear distorted and deformation, rupture and so on.

2.2 Mechanical seal vibration, heat cause of the malfunction
Equipment rotation, will face rough fit ring movement, movement rings and seal cavity gap is too small, due to runout caused by the collision causing the vibration, sometimes because Seals poor corrosion resistance and heat resistance, or inadequate cooling or face particles in the installation folder with impurities, can cause mechanical vibrations and heat sealed.

2.3 Mechanical seal leakage of the medium cause of the malfunction
(1) Static leak test of mechanical seal in the installation because they do not careful, tend to make the seal face was bruised, deformed, damaged, do not clean up the net, there are the granular impurities, or because of screw loosening, gland not pressed, machinery, precision equipment is not enough, so that the sealing surface is not fully fit, will result in media leaks. If it is missing sleeve, the sleeve seal assembly is compressed or not enough compression or damage. (2 cyclical or intermittent leaks. Cyclical components of the mechanical seal rotor vibration, axial movement is too big, can cause leakage. Mechanical seal sealing surface have a certain specific pressure, so as to play a role in sealing, This requires that the mechanical seal spring to have a certain amount of compression to the seal faces a thrust, rotate them so that the sealing surface than produce the required sealing pressure. In order to ensure that a specific pressure, mechanical shaft seal requirements can not have too much channeling the amount, generally less than 0.25mm to ensure, but in the actual design which, due to improper design, often channeling shaft have a huge amount, the use of mechanical seals is very unfavorable (3 recurrent mechanical seal leakage mechanical seal leakage regular many reasons First, since the seal faces caused by defects in recurrent leak. The second aspect is secondary seal leakage caused by the recurrent third aspect is caused by defects in the spring leakage of other aspects, including the vibration caused by the leakage of the rotor, transmission, adapter and the thrust caused by loose parts or poor quality leak, mechanical seal leakage caused by supporting institutions, due to media problems caused frequent leaks, etc. (4 vibration is too large mechanical seal Mechanical seal vibration is too large, leading to loss of sealing effect, but the vibration is too large because the mechanical seal mechanical seal is often not just their own reasons, the other pump parts is the source of vibration, such as shaft unreasonable design, processing reasons, lack of precision bearings, coupling the parallel difference, radial force and other reasons.

Links to free download http://www.hi138.com 3 failed to take measures to deal with
If the mechanical seal parts failure, the need to replace parts or to improve precision machining parts, mechanical seals to improve their precision and accuracy of processing other parts of the pump mechanical seal effect is very beneficial. In order to improve the sealing effect of the static ring of the friction surface finish and roughness higher. Static friction surface width of the ring is not, generally 2 to 7 mm.

3.1 Mechanical seal vibration, heat treatment
If the movement ring and the seal cavity gap is too small, we should increase or decrease the diameter of the sealed chamber turning diameter, 0.75mm gap at least to ensure that if the friction pair is improper, we must change the static ring materials, making it resistant to temperature, corrosion-resistant so it will reduce the mechanical vibrations and heat sealed.

3.2 Mechanical seal leakage treatment
Mechanical seal leakage is due to a variety of causes, we have to deal with specific issues order to minimize the leakage, be sure to install the mechanical seal in strict accordance with technical requirements for the assembly, but also note the following.

(1 assembly to clean and smooth. Mechanical seal parts, tools, lubricants, wiping materials to be very clean. Static ring seal faces to use a soft gauze wipe (2 trimming chamfer rounding. Shaft seal cover chamfer to be trimmed so smooth, rounded shaft and end caps to the sanding polish (3 secondary seal assembly, the rubber secondary seal can not use gasoline, kerosene immersion washing, so as not to swell deformation, premature aging. After the static ring assembly, hand pressing the compensation loop, check whether the place is flexible; elastic snap ring is positioned reliable ring installation, you must ensure that it is flexible in the shaft axial movement.

3.3 shaft channeling large processing
nbsp; rational design of axial force balance device, eliminating the amount of axial channeling. To meet this requirement, the multi-stage centrifugal design are: balance disc plus the axial thrust bearing, axial force balance by the balance disc, the axial thrust bearing on the shaft axial spacing.

3.4 increase the auxiliary flush system
Sealed cavity sealing medium containing particles, impurities, must be washed, otherwise they will be the precipitation of crystals, particles, impurities deposition, so that the spring mechanical seal failure, if the particles into the friction will lead to rapid destruction of the mechanical seal, so mechanical The auxiliary seal flush system is very important, it can effectively protect the sealing surface, play a cooling, lubrication, wash away debris and so on.

Pump vibration treatment measures 3.5
Pump assembly in the process of manufacturing the product in strict accordance with standards and procedures to perform, to eliminate the vibration source pump, motor, base, on-site piping and other auxiliary equipment installed in the field, to strictly eliminate the source of vibration.

More than a simple study of the mechanical seals in rotating equipment applications, and failures, the later encounter mechanical seal failure, we should first consider the factors affecting the mechanical seal itself, and then have to consider some of the mechanical seal external factors. For example: the quality of the mechanical seal in the analysis of the reasons for the accident, taking into account other parts of the pump affect the operation of mechanical seals, mechanical seals to take measures to continuously improve the results. Links to free download http://www. hi138.com