Reciprocating piston compressors for process flow are an important equipment widely used in various industries. The crosshead is an important part of the crank-link mechanism that converts the rotary motion of the drive machine into a reciprocating linear motion. There are many ways to connect the crosshead to the chrome plated steel rod. Threaded connections, coupling connections, flange connections and wedge connections. Figure 1 is a structure of a threaded connection, characterized in that the crosshead and the chrome plated steel rod are screwed and fastened with a hydraulic nut. The structure is simple in this way, and the dead space between the piston and the cylinder can be adjusted by the connecting thread of the chrome plated steel rod and the crosshead. However, since the crosshead and the hydraulic nut are closely fitted, the elastic deformation of the chrome plated steel rod in this section is very small, and even if a large preload is applied during installation, it is easy to loosen when subjected to an impact load. And the piston needs to rotate together with the piston component when adjusting the dead space, which is large in size,
Heavy weight pistons are very inconvenient.
2 structural improvement
Flange-type connection structure and threaded connection structure Most of the large-scale reciprocating piston compressors, the piston rod and the crosshead are connected by hydraulic stretching to tighten the coupling nut. The hydraulic tensioning method is used to tighten the nut, mainly by hydraulically loading and connecting the stud to generate a certain amount of elastic deformation.
A gap is created between the two connectors, and the gap is eliminated by the rotation of the nut. When this gap is removed, the elastic deformation of the studs still exists, forming the necessary pretension. Since the load of the reciprocating piston compressor has a certain impact, if the amount of elastic deformation generated under the impact load is greater than the amount of deformation generated when the preload is installed, the nut is liable to loosen. The structure shown in Fig. 1 is too small, only about 0.02~0.05 mm, so the unit with this structure has experienced several times of nut loosening.