Technical requirements and precautions of pneumatic lifting mechanical seal
Seal ring is the general name of moving ring and static ring (the same below), which is the most important component of mechanical seal. Seal ring determines the service performance and service life of mechanical seal to a great extent. Therefore, some requirements are put forward for it. It can be used in telescopic mast
Sufficient strength and rigidity
Under working conditions (such as pressure, temperature, sliding speed, etc.), the deformation should be as small as possible, and the sealing performance can still be maintained when working conditions fluctuate. In particular, the sealing end face should have sufficient strength and certain corrosion resistance to ensure satisfactory service life of the product.
Have good heat resistance and impact resistance
Therefore, the material is required to have a higher thermal conductivity and a smaller linear expansion coeffcient, and it will not crack when it is subjected to thermal shock.
Smaller friction coefficient
Seal ring matching should have a smaller friction coefficient.
If dry friction occurs for a short time during work, the sealing end face will not be damaged. Therefore, seal ring should have good self-lubrication, and seal ring materials and sealing fluid should also have good wettability.
The structure of the seal ring should be simple and symmetrical, and the structure of the overall type should be preferred. The combined (such as embedded) seal ring can also be adopted, so as to avoid the spraying structure of the sealing end face as much as possible.
Seal ring is easy to process and manufacture
Installation and maintenance should be convenient and the price should be low.
Pay attention to problems
1. Pay great attention to avoid installation deviation during installation
(1), tighten the gland should be carried out after the coupling alignment, bolts should be evenly supported to prevent the gland end face deflection, check each point with a feeler, the error is not more than 0.05mm.
(2) Check the matching gap (I .e. concentricity) between the gland and the outer diameter of the shaft or sleeve, and make it uniform around. Use a feeler to check that the tolerance of each point is not more than 0.01mm.
2. The compression amount of the spring should be carried out according to the regulations. It is not allowed to be too large or too small, and the error is required to be 2.00mm. Increase the specific pressure of the end face during the meeting to accelerate the wear of the end face. Too small will cause insufficient specific pressure and cannot play a sealing role.
3. After the moving ring is installed, the moving ring should automatically bounce back after being pressed to the spring.
Installation location requirements
In order to ensure stable operation of mechanical seal, long service life and low leakage performance, it is very important to correctly install it on the machine. Precautions for installation:
1. Confirmation of components
When installing the mechanical seal on the machine, it should be compared well with the General Assembly drawing before installation to confirm whether the parts are fully prepared. At this time, pay attention to whether there are scars on the sealing surface of the sealing friction pair and the sealing ring, etc, abnormal phenomena such as defects, attention should also be paid to whether there are scars on the shaft or sleeve surface, flange and other parts that contact with packing, sealing ring (O ring), etc. If abnormal phenomena are found, it must be replaced or repaired before use.
In actual installation, do not bring more than the required parts to the site. In this way, if there are any remaining parts after installation, there is a missing place during installation; If the parts are insufficient, it means that parts are also assembled in unnecessary places, which also plays a role of self-checking during installation.
(Some people think that a good fitter does not need drawings and other marks, which is wrong. Then he is just a skilled worker, not a good inspector)
2. Installation location
The installation essentials vary with the mechanical seal type and machine type. Details are not described here.
Technical requirements for installation
Mechanical Seal is a mechanical component with high precision, which has a great influence on its correct installation and operation on its service life. We generally follow the standards stipulated by the Ministry of Petroleum and Chemical Industry.
The technical requirements of the matching part of pump and mechanical seal installed with mechanical seal are as follows:
1. Shaft bending degree: the maximum is not more than 0.05mm;
2. Rotor vibration: no more than 0.06mm near the shaft sleeve at the moving ring seal ring;
3. The axial channeling momentum of the shaft is not allowed to exceed ± 0.5mm. If there is a shaft sleeve, the shaft sleeve is not allowed to loosen;
4. Alignment error of coupling: for gear coupling no more than 0.08~0.10mm (P2008C), for elastic coupling no more than 0.05~0.06mm; (customary practice end jump <0.05, diameter jump <0.10)
5. Gland (stationary seal ring seats) and seal fit seam allowance the concentricity tolerance of the Axis center line is 0.05mm, and the verticality tolerance of the plane in contact with the gasket to the center line is 0.03~0.05mm, if the requirements are not met, seal cage will be processed;
6. The end of the shaft sleeve where the moving ring seal ring is installed and the end of the gland (or shell) where the stationary seal ring is installed should be chamfered and smooth.
1. Be careful when installing and disassembling the mechanical seal. Do not use hand hammer and flat shovel to avoid damage to potted component. If the scale cannot be removed, it should be cleaned before disassembly.
2. If both ends of the pump are mechanically sealed, take care of each other during assembly and disassembly to prevent one from losing one another.
3. For the running mechanical seal, if the gland is loose and the seal moves, the dynamic and static ring parts must be replaced and should not be used again. Because the original running track of the friction pair will change after loosening, the sealing of the contact surface will be easily damaged.
Preparations before Startup
1. Fully check whether the mechanical seal and auxiliary device and pipeline installation are complete and meet the technical requirements.
2. Conduct static pressure test before starting the mechanical seal to check whether the mechanical seal has leakage. If there are more leaks, we should find out the reasons and try to eliminate them. If it is still invalid, it should be disassembled, checked and reinstalled. General static pressure test pressure is 2~3kg/square centimeter.
3. Press the pump to rotate turning machine manually to check whether it is light and even. If the car is difficult or not moving, check whether the assembly size is wrong and whether the installation is reasonable.
Installation and shutdown
1. Keep the sealed cavity filled with liquid before starting. When conveying solidified medium, steam is applied to heat seal cage to melt the medium. You must turning machine manually before starting to prevent the soft ring from cracking due to sudden starting.
2. For the mechanical seal of the oil sealing system outside the pump, the oil sealing system should be started first. Stop the oil sealing system finally after parking.
3. After the shutdown of hot oil pump, the cooling water sealing the oil Chamber and the end face seal cannot be stopped immediately. The cooling water can be stopped only when the oil temperature at the end face seal drops below 80 degrees, so as not to damage the sealing parts.
1. If there is slight leakage after the pump is started, observe for a period of time. If the leakage is still not reduced after continuous operation for 4 hours, the pump should be stopped for inspection.
2. The operating pressure of the pump should be stable, and the pressure fluctuation should not be more than 1kg/cm2.
3, pump on stream, should avoid the phenomenon of evacuation, so as not to cause dry friction and seal damage.
3. Check the sealing condition frequently. In operation, when the leakage exceeds the standard, the heavy oil is not more than 5 drops per minute, and the light oil is not more than 10 drops per minute. If there is still no improvement trend within 2-3 days, the pump should be stopped to check the sealing device.