Branches, North China Electric Power Group Corporation, electric power companies of provinces (autonomous regions and municipalities directly under the Central Government), Huaneng Group, Huaneng International, CLP International, Guodian Electric Power, General Administration of Electricity Supervision, Northeast, East China, Central South and Southwest Electric Power Design Institutes:
1997 after the "12. 16" boiler water shortage accident occurred in Qinhuangdao thermal power plant, the state power company specially organized experts to investigate the water level measurement and water level protection of boiler drums in domestic power plants, and found that there were a series of problems in system configuration, installation of measuring devices, operation management and so on. It has seriously threatened the safe and stable operation of the unit. Therefore, in the chapter "Preventing boiler drum from water shortage and water filling accidents" of "Fifteen Key Requirements for Preventing Major Accidents in Electric Power Production", the installation, water level benchmark and protection management of boiler drum water level measurement system are put forward in principle. In order to better implement the relevant provisions of "Twenty-five Key Requirements for Preventing Major Accidents in Electric Power Production" and effectively prevent boiler drums from being short of water and full of water, based on reference to domestic and foreign power station boiler manufacturing standards, combined with the actual situation of domestic power station boilers, some provisions on configuration have been formulated, and the "Measures for Installation and Use of Power Station Boiler Drum Water Level Measurement System of State Power Company (Trial)" has been formulated, which are hereby printed and distributed to you, and all units are requested to strictly implement it. Attachment:
Provisions on Configuration, Installation and Use of Boiler Drum Water Level Measurement System of State Power Company
(Trial)
In order to ensure the safe operation of power plant boilers, this regulation is formulated according to the relevant requirements of "preventing boiler drum from being full of water and short of water" in "Twenty-five key requirements for preventing major accidents in power production".
1. Scope of application
This procedure is applicable to ultra-high pressure and subcritical thermal power generation drum boilers of State Power Company.
2 configuration of water level measuring system
2. 1 The newly-built boiler drum should be equipped with two sets of local water level gauges and three sets of differential pressure water level measuring devices, and 1 of the two sets of local water level gauges can be replaced by electrode water level measuring devices. The drum of in-service boiler should be configured according to the actual site and the configuration requirements of newly-built boiler.
2.2 The adjustment, alarm and protection of boiler drum water level should be taken from the signals judged by three independent differential pressure transmitters, and the signals should be corrected for pressure and temperature.
2.3 The local water level gauge can be glass plate type, mica plate type and bull's-eye type.
3. Install water level measuring device
3. 1 Each water level measuring device shall have an independent sampling hole. Multiple water level measuring devices should not be connected in parallel on the same sampling hole to avoid mutual influence and reduce the feasibility of water level measurement.
3.2 When installing the water level measuring device, the installation position of each water level measuring device should be accurately determined with the level gauge based on the geometric center line at the same end of the steam drum, and the boiler platform and other objects should not be taken as the reference.
3.3 When installing the sampling valve of the water level measuring device, the valve stem should be in a horizontal position, and a connecting pipe can be added between the steam side sampling pipe and the water side sampling pipe of the water level measuring device.
3.4 The opening position of the water level measuring device and the diameter of the sampling tube shall be determined and provided by the boiler manufacturer according to the structure and arrangement of the internal components of the boiler drum and the operation mode of the boiler.
3.5 Installation of local water level gauge
3.5. 1 The zero water level line of the local water level gauge should be lower than the zero water level line in the drum, and the reduced value depends on the working pressure of the drum. If the zero water level line of the local water level gauge in service is consistent with the zero water level line in the boiler drum, the zero water level line of the local water level gauge should be recalibrated according to the working pressure in the boiler drum, and the specific reduction value should be provided by the boiler manufacturer.
3.5.2 When installing the steam-water side sampling pipe, ensure that the inclination of the pipe is not less than 100: 1, the sampling hole side of the steam side sampling pipe is high, and the sampling hole side of the water side sampling pipe is low (see figure 1).
3.5.3 The sampling pipe, sampling valve and connecting pipe on the steam-water side shall be well insulated.
3.6 Installation of differential pressure water level measuring device
3.6.l The balance container of differential pressure water level measuring device should be a single-chamber balance container, that is, a sphere or a ball-head barrel (with a volume of 300-800ml), and there is a sampling pipe connecting pipe at the steam-water side in front of the container.
3.6.2 When installing the sampling pipeline on the steam-water side, ensure that the inclination of the pipeline is not less than 100: 1. For the steam side sampling tube, the sampling hole side should be lower, and for the water side sampling tube, the sampling hole side should be higher (see Figure 2).
3.6.3 It is forbidden to open a sampling hole in the middle section of the connecting pipe as the sampling point of the steam-water side of the differential pressure water level measuring device.
Fig. 3 schematic diagram of sampling hole in the middle section of communication pipe
3.6.4 The sampling pipe, sampling valve and connecting pipe on the steam-water side shall be well insulated. The balance vessel and the pipeline forming the reference water column at the lower part of the vessel should not be insulated. The two pipes leading to the differential pressure transmitter should be laid in parallel and insulated, and anti-freezing measures should be taken as required.
4. Operation and maintenance of water level measuring device
4. 1 The differential pressure water level measuring device shall determine the average temperature of the reference water column for temperature correction according to the on-site ambient temperature, and set the correction loop regularly according to the change of ambient temperature.
4.2 Before the boiler starts, the formation of reference water column of differential pressure water level measuring device shall be ensured. The monitoring of boiler drum water level should be based on the display value of differential pressure water level measuring device.
4.3 Check the zero water level of differential pressure water level measuring device and the zero water level of local water level gauge at rated steam pressure on a regular basis (per shift). If the deviation is too large, the zero water level of differential pressure water level measuring device should be corrected based on the zero water level of local water level gauge under rated steam pressure.
5. Boiler high and low water level protection
5. 1 boiler water level protection is not put into use, and it is forbidden to start the boiler.
5.2 Boiler drum water level protection should be tested before the boiler starts, and it is forbidden to use signal short circuit method for simulation test.
5.3 The setting, setting value and delay value of boiler drum water level protection vary with the type of boiler and the internal components of the drum. The specific value is determined by the boiler manufacturer, and each unit shall not determine it by itself.
6. The Power Generation and Transmission Operation Department of the State Power Company shall be responsible for the interpretation of these Provisions.
7. These Provisions shall come into force as of the date of promulgation.