The bolt stretcher is an ultra-high pressure product and should be used correctly, otherwise it will not achieve the expected effect and may even be dangerous.

(1) The oil pressure must be calculated before use, so as to prevent the working pressure from being too large and beyond the bearing capacity of the bolt, causing plastic deformation of the bolt and damaging the bolt. The tensile force generated by the bolt tensioner is equal to the product of the output pressure of the power source and the effective area of the piston. Therefore, the allowable stress can be calculated according to the strength grade of the bolts used, and the output pressure of the pump can be calculated in reverse. Ensure that the deformation of the bolt is within the elastic deformation, and complete the work without destroying the bolt.

(2) In the process of pressurization, the pressurization should be as uniform as possible. Every time a certain pressure is increased, it should be stabilized before it is increased, so as to avoid excessive impact tension and affect the pre-tightening effect of bolts.

(3) During the stretching process, pay attention to the maximum design stroke of the stretcher. If the maximum stroke is exceeded, the seal will be cut lightly, and the safety accident will occur seriously. Generally, tensioners have a maximum travel warning line, which requires users to pay attention to the maximum travel at any time during use.

(4) When using the tensioner to remove the bolt, after tightening the tension nut, loosen it by about 3/4-1 turn, so as not to tighten the tension nut on the piston when the bolt is elastically reset. When the bolt is pre-tightened, there is no such problem, and this part of the force is mainly borne by the working nut instead of the tension nut.

(5) When preloading multiple bolts step by step, in order to reduce the influence between bolts preloaded in different steps, the sequence of bolt preloading and tensile force should be arranged reasonably. Generally, the order should be arranged according to the principle of symmetry. For example, when a single tensioner is used to pretension the flanges of eight bolts, the tension control in each step is more complicated, because in the flanges as shown in the above figure, the bolts that are pretensioned later will definitely have an impact on the bolts that are pretensioned first.