The connection and positioning bolts between the cylinder block and cylinder head of the GD5-1000/17-230 diaphragm compressor are broken
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On March 18, 2024, a cylinder head mounting bolt failed in the GD5-1000/17-230 type hydrogen diaphragm compressor used in a certain project. For this model, the weight of each set of cylinder blocks, cylinder heads, bolts, etc. together is approximately 2 tons. The cylinder block and cylinder head of a diaphragm compressor are connected together by a ring of bolts that pass through them (with the diaphragm sandwiched in between). In this design, there are 3 positioning bolts per cylinder head; these bolts have a slightly larger outer diameter than ordinary bolts, and they fit into holes in the cylinder block and cylinder head in a transitional manner (the holes for these positioning bolts are precision-machined). The purpose of this design is to use these 3 positioning bolts to hold the cylinder block and cylinder head in place, preventing the diaphragm and O-rings from shifting out of position. Additionally, these bolts help to support the weight of the cylinder head when the diaphragm needs to be replaced. The remaining 29 are ordinary bolts with a slightly smaller diameter; there is a clearance fit between the ordinary bolts and the bolt holes in the cylinder block and head (the bolt holes in the cylinder block and head are drilled with a 2mm clearance). In addition to differing in thickness, regular bolts and set screws also differ in their structural design.
The weight of the cylinder block and cylinder head is nearly 2 tons; together, their thickness is 420 mm. The length of the positioning section is 400 mm, and this excessive length causes the positioning bolts to break, as the weight of the cylinder head exerts shear forces on these bolts. Additionally, there is a certain degree of misalignment between the holes in the cylinder block and cylinder head, which leads to deformation of the bolts. Under alternating loads, the positioning bolts are repeatedly stretched and bent, resulting in gradual failure at the points of maximum deformation or at defective areas, eventually leading to cracking. To address the issue of broken bolts in the cylinder head assembly, this problem tends to occur due to the thick thickness and large weight of the cylinder head. The following procedure can be followed: Use the existing positioning bolts as temporary positioning elements; first install these three bolts to determine the position of the cylinder block and cylinder head. Once everything is in place, install the remaining regular bolts and apply a torque of 200 NM. Then remove the temporary positioning bolts and replace them with the regular bolts, applying another torque of 200 NM. After performing this operation, both the cylinder block and the cylinder head are accurately positioned, and there is no more bending or deformation of the positioning bolts; the stress conditions of all bolts are normal, ensuring safety and reliability. For larger diaphragm compressors in subsequent models, the method of assembling the cylinder block and cylinder head involves using special tools and bolts; positioning and assembly are carried out first, followed by the installation of regular bolts, in order to avoid the risk of the bolts being sheared due to the heavy weight of the cylinder head.
On March 18, 2024, a failure occurred in a GD5-1000/17-230 type hydrogen diaphragm compressor used in a project, as the set screws connecting the cylinder block to the cylinder head broke. This compressor weighs approximately 2 tons, with the cylinder block and cylinder head held together by a ring of bolts, including 3 thicker setting bolts and 29 regular bolts. The setting bolt is designed to ensure proper alignment of the cylinder block and the cylinder head, as well as to support the weight of the cylinder head when replacing the diaphragm. The breakage of this bolt may affect the proper operation and safety of the machine. .