When should the positioning pins of the spring hangers be removed?
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When the unit was first put into operation, when were the positioning pins of the spring hangers removed? Some say it is after pressure testing and before water commissioning, while others say it is after water commissioning and before cold oil operation. Are there any relevant standards or specifications?
Generally, the spring pin is removed before starting up and feeding material, in order to conduct a hot-state test of the device and verify whether the expansion design is reasonable.
The positioning pins of the spring hangers must be removed after the installation and welding are completed. Be sure to make marks before removal, and observe any changes in stress after removal; in some cases, prestress adjustment is also required. During the heating or loading process, multiple measurements should be taken, and adjustments should be made if necessary.
1. Variable or constant force spring supports mainly compensate for the displacement of pipes, ensuring that the supporting load remains at the designed value within the specified displacement range. Since pipe displacement is primarily caused by temperature changes, the positioning pins should be removed before the system reaches its operating temperature. 2. During the cold commissioning phase, it is fine to remove the positioning pins as long as no liquid enters the gas pipeline. The self-weight of ordinary pipes (including the medium inside) does not change much, so there is no risk of damaging the elastic support brackets; therefore, removing them earlier has little impact ； However, the self-weight varies greatly; for example, when large-sized vapor pipes are filled with liquid, such abnormal loads should not be borne by elastic elements, but rather by positioning pins. 3. For those with special design requirements, follow those requirements
It is generally removed before hot-state commissioning, for example, before introducing steam or heating the furnace