After the  circulating water was interrupted, the exhaust temperature will rise quickly, the tie bar, low-pressure cylinder and copper tube of the condenser are expanded laterally, at this moment if the circulating water is supplied, the copper tube will be firstly cooled, but the tie bar(lacing wire) of low-pressure condenser is not cooled, in this way the copper tube is shrunk, and the tie bar is not, the copper tube will have bigger tensile stress, which will loosen the end of the copper end, thus causing the copper tube of the condenser to leak, therefore the condenser cannot be supplied with water again until the condenser temperature is below 50 ℃ after the circulating water has been interrupted for long time.