Due to the calculation error or incompleteness of the desulfurization pump, if the disc spring with excessive preload is selected, if the pressure is too high and exceeds the yield limit of the gasket and bolt materials, it will also lead to leakage.

In this case, the coil spring must be used for compensation, and the compensation force is greater than the required minimum seal preload and less than 75% of the material yield limit.

There are usually two kinds of errors in practical work.

1. Selection pressure is too small: according to the physical characteristics of bolt pre tightening, if the pre tightening force is relaxed by 30%, it will not reach the minimum value required for sealing, which is equivalent to installing coil spring;

2. The selection pressure is too large: if the elastic yield limit of the coil spring or the valve rod is locked, the inner taper of the coil spring stroke exceeds 75%, resulting in permanent deformation, which is equivalent to manually amplifying the pre tightening relaxation force of the bolt, which is more harmful.

3. Thermal expansion and cold contraction: in the same mechanical equipment, due to different materials of bolts, washers, flanges and packing boxes, the expansion and cold contraction speed is also different within the same temperature range. Therefore, within the temperature difference range, the original preload of the desulfurization pump manufacturer will be reduced, and the relaxation degree of preload will become geometric by overlapping each other. Stage expansion leads to leakage.