Causes:
(1) Due to the overall design of the heating station, considering the reasons of hydrophobic recovery, etc., the heater is placed at the highest temperature of the heating network (at the highest point in the circulation system).
(2) Since the concentrated hot water supply distance can reach 30KM or even longer, the pipe network is huge, and the pipe network construction is completed year by year. When constructing a new pipe network, it is often selected during the heat network outage period. During the period, the pipe network is not replenished and pressure-protected. Therefore, when water is injected into the pipe network in the early stage of heating, the air in the pipe network cannot be completely discharged.
(3) When the heat network heater is put into operation, after the water supply and return water pressure of the pipe network is established, the external air is completely shut off, the circulating pump is started to establish a cold water cycle, and the water on the water side of the heater is exhausted, then the gas is closed. All of the air doors, fully open the heater circulating water inlet and outlet doors, open the steam side to heat the circulating water. Due to the nature of the water, a certain gas is dissolved in the water, so the gas in the pipe network enters the hot site along with the flow of water. Most of the gas will collect in front of the inlet of the circulation pump, and will be drained from the air door, but some will pass through the pump body, the pipe, enter the heater, and gradually gather at the top of the water side of the heater. The accumulated gas is under pressure. Under the action of water, it will gather in a semicircle along the inner wall of the water side of the heater. When the amount is small, vibration will only occur when the heat load of the heater is changed. At this time, the vibration is small and it is not easy to detect. When the amount of internal aggregation is large, a strong thermal stress will be generated, and strong vibration will occur, causing the heater tube bundle to rupture, so that the heater leaking water cannot be recovered, resulting in huge economic loss. (When the heater is broken, the bundle will also appear in a semi-circular shape, which is the characteristic of the gas gathering on the water side of the heater)