On line monitoring system of main fan

  Ventilation subsystem I
1 On line monitoring system of main fan
1、 1
1 System status
The ventilation subsystem includes the main fan online monitoring system and the underground local fan online monitoring system
Both systems are newly built control systems
The system uses Siemens PLC as the control core and is equipped with RJ45 communication interface

According to the on-site environment and actual hardware configuration conditions, after analysis, the automatic control system can be constructed to realize unattended

1、 1
2 System overview
The on-line monitoring system of mine fan is a necessary supporting equipment of fan
It monitors the operation state of main fan in real time, and makes rapid and reasonable treatment for various situations in its operation, so as to provide information basis and powerful measures for coal mine safety production, economic and reasonable ventilation and fire disaster relief ventilation

The on-line monitoring system of the main fan designed in this scheme can provide rich data, graphics and information, so that users can quickly understand the current operation state of the fan
When the fan operates abnormally or with diseases, the system will give reliable alarm signals and corresponding logic control; Provide technical reference for operators, effectively ensure mine safety and double the production efficiency of coal mine

1、 1
3 System monitoring object
The main monitoring objects of the fan online system are: the status and parameters of the fan, the motor driving the fan, the motor driving device (PLC communication interface needs to be reserved), the fan damper, the fan power distribution equipment and supporting pipelines

1、 1
4 system composition
The overall design of the fan online monitoring system is a three-tier architecture: information layer (background and touch screen), control layer (PLC), and equipment layer (field sensors, intelligent monitoring instruments, integrated protection devices, etc
)
The system topology is shown in the figure

 
Topology of fan on-line monitoring system
Control background
The control box is equipped with a touch screen to locally display and control the operation status and parameters of the fan
The touch screen is a 10 inch display screen
The TPC 1062ks touch screen supports 32 language configurations including Chinese, which is suitable for a variety of installation environments
The screen body is embedded in the front end of the control cabinet
Before installing the touch screen, a window needs to be reserved according to the size of the screen body

Control cabinet
Siemens S7-300 series PLC is configured as the control core of the system, and the on-site switching value signal is collected by configuring the switching value input module; Configure the switching value output module to complete the logic control of the controller to the fan, collect the value of the on-site analog sensor by configuring the analog input module, and realize the communication with the on-site intelligent comprehensive protection device, intelligent power acquisition module, motor drive unit, etc
by configuring the Profibus / RS485 communication module

The design size of control cabinet is 800x 600x2000mm, the layout in the cabinet is shown in the figure

 
External front view of control cabinet
 
Front view of control cabinet interior
1、 1
5 Sensing equipment
Negative pressure sensor
The negative pressure sensor is used to detect the gas pressure in the air duct of the main fan
DPT series pressure transmitter is selected
The DPT series micro differential pressure transmitter of Finnish HK instrument unit has small volume and very stable performance
The range can be selected by jumper

 
Main technical parameters:
1
  4 ~ 20mA, maximum load 500 Ω;
2
  Electrical connection: 4 screw terminals, max
1
5 mm2;
3
  Cable inlet: m 16;
4
  Power supply voltage: 24VDC;
5
  Operating temperature: - 10 + 50 ℃;
6
  Storage temperature: - 20 + 70 ℃;
7
  External humidity: 0 to 95% RH

Differential pressure sensor
The differential pressure sensor is used together with the pressure tapping device to detect the gas pressure in the air duct of the main fan in order to calculate the air volume of the air duct
The differential pressure sensor adopts DPT series pressure transmitter
The DPT series micro differential pressure transmitter of Finnish HK instrument unit has small volume and very stable performance, and the range can be selected by jumper

 
Main technical parameters:
a)  4 ~ 20mA, maximum load 500 Ω;
b)  Electrical connection: 4 screw terminals, max
1
5 mm2;
c)  Cable inlet: m 16;
d)  Power supply voltage: 24VDC;
e)  Operating temperature: - 10 + 50 ℃;
f)  Storage temperature: - 20 + 70 ℃;
g)  External humidity: 0 to 95% RH

Wind speed sensor
 
Gfw15 coal mine air volume sensor adopts ultrasonic measurement principle
It is mainly used to continuously monitor the wind speed at the main return air roadway of mine ventilation, main underground wind measuring station, fan, etc
it is an important instrument for the measurement of mine ventilation safety parameters
It has infrared remote control adjustment function and simple adjustment

Main technical indicators
1)  Measurement range: 0
3-15m/s
2)  Measurement error: less than & plusmn; 0
3m/s
3)  Response time: less than 40s
4)  Display: three digit LED local display
5)  Output signal: 4-20mA
6)  Working voltage: intrinsically safe dc9v-21v
7)  Operating current: & le; 70mA  
8)  Signal transmission distance: & le; 2km
Vibration monitor and accessories
The vibration monitor is used to detect the axial vibration and radial vibration amplitude of the fan duct
The zt6305 vibration intensity monitor and supporting speed sensor produced by Jiangyin Zhongtai science and technology unit are selected, and the CD-6 is selected

 
Main technical parameters:
1
  Sensitivity: 20mV / mm / S & plusmn; 5%；
2
  Frequency response: 10 ~ 1000Hz; Input impedance: & gt; 100KΩ；
3
  Measurement range: 0 ~ 50
0mm/s (true effective value);
4
  Measurement accuracy: linear error &le& plusmn; 1% (full scale value);
5
  Display mode: 3-digit nixie tube display;
6
  Current output: 4 ~ 20mA output load: ≤ 500Ω；
7
  Alarm contact capacity: dc28v3a;
8
  Working environment: temperature: 0 ~ 65 ℃, relative humidity: ≤ 85%；
9
  Working power supply: AC 220VAC & plusmn; 10% 50Hz power consumption ≤ 20W；
10
  Installation method: disc type;
11
  Overall size: 160 (width) & times; 80 (high) & times; 300 (deep) mm;
12
  Opening size: 151 (width) & times; 75 (height) mm

Main functions:
1
  Display function: vibration measurement value, I value alarm and II value alarm setting value can be displayed on LED nixie tube respectively;
2
  Alarm function: when the vibration amplitude exceeds the alarm set value, the alarm indicator will be on, and the switch signal will be output at the back to protect the monitored equipment;
3
  Alarm delay time setting function: the adjustment range of alarm delay time is 0 ~ 3 seconds to prevent false alarm caused by on-site interference;
4
  Self diagnosis function: it has the function of power on and power off detection, and disconnect the alarm output circuit, which can effectively suppress the false alarm of the instrument

1、 1
6 System principle
1
The principle of measuring the air volume by pressure method is adopted
A pressure taking pipe is installed on the air inlet roadway or diffuser of No
1 and No
2 fans
The pressure difference of the variable section of the diffuser is measured by the differential pressure transmitter to calculate the air volume;
A static pressure tapping pipe is installed in the mine air tunnel, and the total negative pressure of the mine can be continuously monitored by using the pressure transmitter;
3
Temperature detection elements shall be embedded on the bearings of No
1 and No
2 fans and the stator winding of the motor
Temperature signals shall be collected through the thermal resistance input module installed in the PLC cabinet
When any temperature exceeds the set temperature alarm value, audible and visual alarm can be carried out;
4
Use the equipment start and stop sensor to monitor the start and stop status of No
1 and No
2 fans in the mine;
5
By monitoring the change of total negative pressure in the mine, the reverse air or motor reverse state of the mine can be judged by using computer software;
6
The amplitude is measured by the vibration speed sensor installed on the fan bearing, converted into vibration speed by the vibration intensity monitoring instrument, and output to PLC as standard electrical signal

1、 1
7 measuring method
The accuracy of on-site analog and digital measurement affects the operation of the whole system, so it is very important to select the correct measurement method
The following briefly introduces the measurement methods of several parameters in the system:
1
Static pressure measurement
The measurement of total negative pressure in extraction ventilation mine is to measure the average static pressure in the fan tunnel
Pitot tubes and various static pressure sensing tubes can be used to measure the average static pressure at a point in the wind tunnel
Two problems should be paid attention to in static pressure measurement:
As the static pressure is the normal pressure value of the air flow acting on the pipe wall, the key to measuring the static pressure value is to select an appropriate pressure measuring section to ensure that the center line of the sensing hole of the installed pressure measuring pipe is perpendicular to the air flow direction

The static pressure tapping pipe can be either a static pressure tapping pipe or a wall hole

The static pressure measurement is measured by differential pressure transmitter
There is a set of water column pressure gauge for measuring mine negative pressure in the ventilator room
If the installation of pressure taking pipe meets the use requirements, the original impulse pipe can be used
The connection method is shown in the figure below
The static pressure tapping device placed in the air tunnel is connected with a pressure inducing rubber pipe, which is divided into two channels through a three-way, one of which is connected to the water column meter in the ventilator room, and the other is connected to the low-pressure end (L) of the static pressure transmitter through a filter
The high end (H) of the transmitter is connected to the atmosphere, and the transmitter outputs 4 ~ 20mA electrical signal corresponding to the relative static pressure value in the air tunnel

 
Static pressure measurement connection method
2
Differential pressure measurement and fan exhaust volume measurement
The air volume of axial flow fan is measured by drop method
Calculating the air volume by measuring the static pressure difference between two close reducing sections of the gradually shrinking air duct is called the drop method in hydrodynamics

Several static pressure holes (depending on the size of the section) are respectively opened on Section 1 (large) and section 2 (small) of the conical diffuser of the fan, as shown in the figure below
Connect all static pressure pipes in parallel with metal pipe or rubber pipe and lead them to the differential pressure sensor with rubber pipe
According to Bernoulli equation and continuity equation, the calculation formula of average wind speed V2 on small section can be obtained as follows:
 
Where:
A1 and A2: area of section 1 and 2, m2;
P1 and P2: static pressure of section 1 and 2, PA

 
ξ The pressure loss coefficient on the two sections is determined by experiment (negligible)

Enter the area of section 2-2 (small section), and the exhaust air volume of the main fan can be calculated

 
Pressure tapping hole of fan conical diffuser
The schematic diagram of pressure tapping device using drop method is shown in the figure below
Because the drop method is to measure the static pressure difference between two sections, only the static pressure probe is required
The axis of the pressure tap of the static pressure probe shall be perpendicular to the air flow direction, and the vortex area formed by the irregular cylinder wall shall be avoided to affect the air flow stability
The three static pressure taps on sections a and B are installed at 120 degrees
It is respectively connected to the impulse pipe through tee, and the two impulse pipes are respectively connected to the two pressure taps of the differential pressure transmitter, in which the impulse pipe of section a is connected to the high end

 
Pressure tapping device diagram of drop method
3
Temperature monitoring
When the ventilator leaves the factory, temperature measuring elements are generally embedded in the bearing and motor winding & mdash; PT100, connect the output signal of the temperature sensor to the PLC thermal resistance input module to measure the temperature of the motor bearing and winding of the main fan

4
Fan operation status monitoring
The operation status monitoring includes the start-up and stop monitoring of main fan equipment, anti air status monitoring, air tunnel damper status monitoring, etc

Fan start and stop monitoring: two kgt9-e coal mine equipment start and stop status sensors are selected as start and stop sensors, which are respectively stuck on the high-voltage cables of the main and standby fans without electrical contact, and the equipment start and stop is determined by monitoring the cable current

1、 1
8 system function
1
Communication and interface function: the system provides standard RJ45 interface and software OPC interface to realize remote monitoring and control
The monitoring center can check and view the operation status of the main fan in real time through the network
And provide web mode for intranet users to browse

2
Data acquisition function: by configuring the sensor or by