3.5　Level

3.5.1　The level measuring point shall be selected at the place where the operating condition of medium is stable and also shall meet the requirements of measuring range of instrument.

3.5.2　The installation of single chamber balancing container shall meet the following requirements：

1　The balancing container shall be vertically installed.

2　As for the balancing container，its installation elevation and its distance to the positive and negative pressure tapping shall meet the measuring range required by design.

3.5.3　The installation of double-chamber balancing container shall meet the following requirements：

1　The manufacturing dimension shall be rechecked and the sealing of internal pipe shall be inspected before installing.

2　The balancing container shall be vertically installed，and the distance between its positive and negative pressure measuring pipes shall meet the measuring range required by design.

3.5.4　For measuring the water level of steam drum，the installation of the compensatory balancing container or hot-sleeve double chamber balancing container and its pipe shall meet the following requirements：

1　The manufacturing dimension shall be rechecked and the sealing of internal pipe shall be inspected before installing.

2　The sampling valve shall be installed between the steam drum and the balancing container.

3　The balancing container shall be vertically installed，its zero level mark shall be at the same level as the zero level line of steam drum.

4　The drain pipe of balancing container shall be separately led to the downcomer，its vertical distance shall be about 10m，and it should be separately insulated，and the stop valve shall be installed at the side near the downcomer.

3.5.5　When installing the balancing container，valve and pipe，proper measures shall be adopted to prevent them from any damage due to the displacement caused by heat expansion of the thermal equipment.Except for the upper steam side，the rest parts of the double-chamber balancing container all shall be insulated.

3.5.6　The water level balancing containers of high and low pressure heaters and their pipe shall not be insulated and shall be equipped with protective measures.

3.5.7　The sampling valve between steam drum and balancing container shall be transversely installed and be level with the valve rod，the conduit at steam side from the balancing container to the measured vessel have a slope to let the condensed water flow back.

3.5.8　As for the balancing container in which the steam is uneasy to condense，the makeup water pipe shall be installed on it，and other low pressure balancing container may be installed with screwed stopper.

3.5.9　The positive and negative pressure pipes from the balancing container to the differential pressure instrument shall be led out by 400mm horizontally，and then shall be downward in parallel.

3.5.10　The measuring cylinder of electric contact water level meter shall be vertically installed，its vertical deviation shall not be greater than 2°，and its bottom shall be installed with blowdown valve.For the measuring cylinder，the bottom horizontal line of the middle axis of its zero level electrode shall be at the same height as the zero level line of the measured vessel.

3.5.11　The installation of drain pipe that is led out from the electric contact water level meter till the downcomer shall meet those specified in Item 5 of 3.5.4 of this Part.

3.5.12　The bending radius of the laid capillary of double-flange level transmitter shall be larger than 75mm，the capillary shall not be kinked，and two capillaries shall be under the same ambient temperature.

3.5.13　The center line mark on the float cylinder shell of external float-cylinder level gauge represents the midpoint of measuring range，and the installation elevation of float cylinder shall meet the measuring range required by design.

3.5.14　Where the internal float-cylinder level gauge and the float-ball level gauge are adopted with guide pipe，then the guide pipe shall be vertically installed.Both the guide pipe and the lower retainer ring shall be firmly fixed，and the float position shall be limited within the tested measuring range.

3.5.15　The sensor of capacitance level meter shall be vertically installed，its perpendicularity deviation shall not exceed 5°，and it shall avoid the impact of material from feed opening onto the electrode.

3.5.16　The detector of ultrasonic level gauge shall be installed with its distance to the inner wall of vessel being larger than the radius of wave beam at the place with maximum measured distance，and it shall be kept clear from the feed opening.Other objects beyond the material level interface shall not exist within the transmission range of ultrasonic beam.

3.5.17　The heavy punch level gauge sensor and radio frequency admittance sensor for measuring the coal level shall be vertically installed，and their installation positions shall be selected at the place far away from the inlet and outlet.