7.4　Leak Test for Furnace and Flue Gas System

7.4.1　The scope of the overall leak test for the furnace and flue gas and air system shall include boiler furnace，the tail flue gas duct and air heater，flue gas/air ducts，primary/secondary air passages，the denitrification equipment，dust precipitator and auxiliary machinery equipment of flue gas and air system.

7.4.2　The following conditions shall be ready for the test:

1　The documents，which include the internal cleanness inspection for the furnace and the flue gas and air system，the oil leak test for the fabrication and erection welds in the flue gas and air ducts and so on，shall be complete and meet the requirements.

2　The erection and adjustment for pipe supports and hangers in flue gas and air system as well as the corresponding acceptance have been completed.

3　Access holes，the sealing device and so on shall pass the leak test.

4　The damper shall be operated flexibly，with the correct indication.The operating devices of the pneumatic and electric dampers may be put into operation.

5　The fan used in testing has passed its trial operation.

6　The pressure measurement devices for the furnace and the air-flue gas system can be put into operation.

7.4.3　The test pressure shall be determined according to the requirements of the boiler manufacturer's technical documents.If there is no specific requirement，the test pressure shall be taken as 0.5kPa.

7.4.4　During the test，the methods such as putting the talcum powder at the fan cleaning door or other media，which may clearly reflect the leakage，shall be utilized to inspect the the tightness.If any leakage is found，the marking and record shall be carried out.The application amount of talcum powder shall not be less than 0.04kg/m3（the total volume of the furnace and flue gas and air ducts）.

7.4.5　If a wide range of leakage in the furnace or furnace top seal is found，the overall leak test shall be carried out to the furnace and flue gas and air system after the defects have been handled.