Sealing with packing (ring gasket)

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Valves and some water pumps in industrial applications use packing (seal rings) for sealing. After being in use for a certain period of time, these packings lose their elasticity and lubricating properties; if not replaced in time, this can lead to liquid leakage and the entry of air. Therefore, the packing needs to be replaced every time the sealing device is serviced. Sometimes, when severe leaks occur due to poor quality of the filler or improper installation, it also needs to be replaced. When installing or repairing the packing, first remove the packing gland, take out the old packing, clean all the components, then install new packing, and check the clearances of all parts. If the gap between the packing retainer and the shaft sleeve (or the shaft or valve stem when there is no shaft sleeve) is too large, the packing inside the packing box may be forced out. When the gap between the outer circular surface of the packing gland and the inner circular surface of the stuffing box is too large, the gland is prone to being pressed off center. The inner circular surface of the packing gland and the outer circular surface of the shaft sleeve (or shaft, valve stem) must remain concentric; if the gap is too small, friction with the shaft sleeve (or shaft, valve stem) is likely to occur. All of the above gaps must strictly meet their specified standards; if not, they must be adjusted or replaced. 1. Disassembly of the packing seal device: 1) Remove the packing gland nut, move the packing gland axially away, use a packing removal tool or wire hook to take out the packing and packing rings, clean the gland and packing rings, remove the liquid seal tube, and clear the liquid seal channel. 2) When the shaft sleeve of the packing device (or the shaft or valve stem in the case of no shaft sleeve) is severely worn or has grooves, it should be replaced with a new part. If no new spare parts are available, the issue can be addressed by machining the neck of the shaft or valve stem and then fitting a sleeve onto it. 3) New parts should also be replaced when the packing gland, packing retainer, and packing ring are excessively worn. 2. Packing assembly: The quality of packing assembly has a significant impact on the sealing performance of the packing. The following points should be noted during packing assembly: 1) When cutting the packing, the cuts should be neat, with no loose asbestos fibers, and the joints should form an angle of 30° to 45°. 2) Each packing ring should be coated with lubricant and pressed into the stuffing box separately. During compression, the cuts of the packing rings must be offset from each other; generally, the joints of adjacent packing rings should be staggered by 120°. 3) The water seal ring should be aligned with the liquid seal tube; considering that the packing will continue to be compressed after the packing gland is installed, it can be adjusted outward by 3~5 mm. In this way, after the packing gland is installed, the water seal ring can be aligned with the liquid seal tube. 4) After installing the packing, it is necessary to tighten the bolts on both sides of the packing gland evenly; the gland must not be skewed, and it should not be tightened too much at once, as this could cause the packing to lose its elasticity completely, making it impossible to adjust later. It would also increase wear on the shaft sleeve (or shaft, valve stem) and the packing, as well as lead to increased power consumption. 5) The depth to which the packing gland is pressed into the packing box is generally equal to the height of one layer of packing, but it must not be less than 5 mm. There should be a certain distance between the cover plate of the packing gland and the packing box, so that the packing can be compressed further.