The external threaded connection of plate heat exchangers is a common connecting component, which is used to realize the connection between plate heat exchangers and external pipelines. A detailed introduction is as follows:
Features
Threaded connections boast the advantages of convenient installation and high construction efficiency. The connection can be completed without sophisticated tools and professional expertise. However, they have relatively low pressure resistance, and are generally suitable for low-pressure and normal-temperature working conditions. In addition, leakage is prone to occur under long-term vibration. Therefore, they are less frequently applied in industrial systems, and are mostly used in simple small-scale systems such as small fully welded heat exchangers matched with civil wall-hung boilers.
Commonly Adopted Standards
Threaded connections are classified into internal threads and external threads, with widely used standards including ISO-G, NPT and ISO 7/1. Among them, ISO-G threads, also known as British standard pipe threads, are parallel threads. NPT refers to American standard tapered pipe threads, featuring excellent sealing performance. Similar to ISO-G, ISO 7/1 is also a British standard pipe thread specification.
Specifications and Dimensions
Common specifications include ½”, ¾”, 1”, 1¼”, 1½”, 2” and so on. Threaded connections of different specifications correspond to distinct parameters such as shear force, tensile force and torque. For instance, the shear force of a ½” threaded connection is 3.5 kN (3500 N) with a torque range of 20–35 N·m; the shear force of a 1” threaded connection is 11.2 kN (11200 N) with a torque range of 45–155 N·m.
Key Installation Points
PTFE tape, also known as thread seal tape, shall be wound or thread sealant shall be applied during installation to enhance sealing performance and prevent leakage. Meanwhile, over-tightening, which may cause thread damage or deformation of the heat exchanger nozzles, must be avoided. The tightening operation shall be carried out in accordance with the specified torque values.
Maintenance Precautions
Regular inspections shall be conducted to check for leakage at the threaded connections. If leakage is detected, the sealing materials shall be replaced or the threads shall be repaired in a timely manner. Furthermore, careful operation is required during the disassembly and reinstallation of threaded connections to prevent damage to the threads and the main body of the heat exchanger.
