Pressure rise in the 53B sealed isolation tank
Thread Content
A certain diesel hydrogenation unit is equipped with a hydraulic turbine to recover the energy from high-temperature fractions to low-temperature fractions, thereby driving the feed pump and achieving energy savings and reduced consumption. The pressure of the hot high fraction is 6.9 Mpa, and the pressure of the hot low fraction is 2.1 Mpa. The hydraulic turbine uses external flushing along with the 53B system, with the pressure for 53B set at 2.3 Mpa. Recently, when the hydraulic turbine was in standby mode (with the outlet valve open, without preheating and without the external flushing system in use), the pressure in the 53B seal tank at the coupling end rose from 2.3 Mpa to 3.5 Mpa; even after pressure release, it continued to increase. The pressure in the balance tube remained around 2.6 Mpa (no external leakage from the mechanical seal was observed). What could be the reason for this, according to those of you with experience in this field? Furthermore, when the hydraulic turbine is preheated, there is only a preheating coil at the lower part of the pump body, which makes it impossible to preheat the inlet pipeline; the inlet pipeline remains at room temperature before the pump is started. What are the hazards of not preheating the inlet pipeline, and is it necessary to preheat it?
The inlet pipeline definitely needs to be preheated. Turbine manufacturers generally only consider the preheating of the turbine itself; pipeline preheating is something that the designer must take into account. If there is no preheating line available, preheating can be achieved by slightly opening the inlet control valve
When the turbine is put into operation, low-speed warming up is required. There should be a relatively thin bypass line in front of the control valve that regulates the flow of hot high-pressure fluid to the turbine; before starting up, the turbine needs to be warmed up at low speed using this thin bypass line
Based on practical work experience, it is indeed necessary to optimize the preheating process; if preheating of the inlet pipeline is required, this can only be achieved by slightly opening the inlet valve
Slightly open the inlet valve; this operation involves certain technical risks, as the turbine might start rotating if not handled properly
Yes, it can’t be turned up too much; our turbine basically needs 80t to start rotating