Heat exchange tube rupture and leakage, along with safety valve issues
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1. Where is the discharge path behind the safety valve? Heat exchange occurs between the exhaust gas and water; the water circuit is equipped with a safety valve. Since leaks in the heat exchange tubes are expected to prevent large amounts of exhaust gas from escaping into the water system, the fluid discharged by the safety valve should be mostly water, though it may also contain some exhaust gas. Should this discharged fluid be sent to the flare condensate tank or elsewhere? 2. The discharge is directed to the flare condensate tank, but the tank is very small. Normally, it should be discharged into the flare condensate tank; however, the existing condensate tank in the facility has dimensions of 1000×2500 mm, with an inlet pipe of DN100 and a main water pipeline of DN200. The outlet of the safety valve also has a DN100 diameter. As a result, the condensate tank will fill up very quickly once discharge occurs. How can this problem be solved? There is another issue: after coming out of the liquid outlet at the bottom of this condensate tank, the liquid flows into a pipe tray that is at a higher level than the tank. Since the condensate tank is connected to the flare main at atmospheric pressure, how is this liquid discharged? (This unit’s existing condensate line has been sealed, so there is virtually no condensate.)
By considering factors such as the structural type of the heat exchanger, the flow path of the cooling water, and the special piping design near the cooling water outlet of the heat exchanger, a local environment is created in which the gas and liquid phases flow separately. This location serves as the point where the inlet pipeline of the safety valve is connected, thereby ensuring that the safety valve releases mainly gas, thus avoiding the complications associated with discharging a two-phase flow containing a high proportion of liquid.
It depends on the analysis of the operating conditions of your safety valve. If it is determined that overpressure leads to the rupture of the heat exchange tubes and the leakage of exhaust gases into the water side, such gases must not be released into the atmosphere; they should first be discharged into the liquid separation tank. The existing condensate tank is too small and unsuitable; it needs to be enlarged. The condensate from the condensate tank generally enters a closed collection system.