6.4　Water Level Indicator for Steam Drum

6.4.1　The following items shall be inspected before the erection of the water level indicator:

1　There shall be no sundries in any steam and water pipes.

2　The joining surface of the glass plate and the mica cover plate shall be flat and tight.The grinding shall be carried out if necessary.

3　All valves shall be filled with the packing.Opening and closing shall be flexible.There shall be leakfree.

4　The joining surface of the gaskets should use the copper washer.

6.4.2　The steam connecting pipes between the water level indicator and steam drum shall incline toward the water level indicator.The water connecting pipes shall incline toward steam drum.The clearance shall be reserved for the free expansion of steam-water connecting pipe support.

6.4.3　For the erection of the water level indicators，the normal，high and low water level lines shall be marked in the water level indicator according to the drawing sizes and with reference to the center line of steam drum.The deviation shall not exceed 1mm.

6.4.4　The mica sheets，glass plates and quartz glass tubes used for the water level indicator shall meet the following requirements:

1　The mica sheet must be high quality，transparent，flat and uniform.There shall be no spot，wrinkle，crack，bending or other defects.The thickness shall meet the requirements of the manufacturer's instruction.

2　The compressive strength and the thermal stability of the glass plate and the quartz glass tube shall meet the operation pressure requirement，and the sealing surface shall be fine.

6.4.5　The water level indicator shall be used for hydrostatic test，not for the overpressure test.

6.4.6　After the erection of the water level indicator，the zero position of water level indicator shall be led to the end of steam drum and be marked permanently.