Skip to main content

Ammonia Gas Detector Working Principle and Calibration

 Ammonia gas detector working principle and calibration. (Make: Dragger Model : Polytron 5100)

Gas detector is a very important safety device for any chemical plant. Its can give information in any small leak from any pipelines and with early action we can save any incident in plant.

In any chemical plant generally we use four types detector:

Hydrocarbon Detector

CO detector

NH3 detector

Chlorine detector

Here we discussed about Ammonia detector.

Principle :

Ammonia detector works on electrochemical principle. Electrochemical sensors are electrochemical measuring transducers for measuring the partial pressure of gases under atmospheric conditions. The ambient air being monitored diffuses through a membrane into the liquid electrolyte in the sensor. The electrolyte contains a measuring electrode, a counter-electrode and a reference electrode. An electronic potentiostatic circuit ensures a constant electrical voltage between the measuring electrode and reference electrode.

Voltage, electrolyte and electrode material are selected to suit the gas being monitored so that it is transformed electrochemically on the measuring electrode and a current flows through the sensor. This current is proportional to the gas concentration. At the same time, oxygen from the ambient air reacts at the counter-electrode electrochemically. The current flowing through the sensor is amplified electronically, digitized and corrected for several parameters (e.g. the ambient temperature). The resulting measured value is given as an analog, 4-20 mA signal.

Gas Detector Parts :

1.Meter
2.Potentiostat
3.Direct current supply
4.Measured gas
5.Membrane
6.Measuring electrode
7.Electrolyte
8.Reference electrode
9.Counter electrode
10.Temperature sensor

Configuration of Gas Detector:
Gas detector can be used as a two wire or as three wire device.

Connect the gas detector wiring as per your requirement & Power ON the detector. Display shows a start up timer.

Wait for the timer to complete and then press down navigation and go to FSD for Span range.

Calibration of Gas Detector:
For calibration we use N2 gas for zero calibration and 90 PPM ammonia cylinder for span gas .

Typical Calibration Setup : 


Parts :

1.Regulator
2.Calibration gas cylinders ( Zero Gas Cylinder & Span Gas Cylinder  )
3.Calibration adapter
For zero calibration

1.Connect the regulator with N2 cylinder adapter to detector then adjust the flow to 0.5 l/min
2.Press down navigation key for 5 sec its showing -0- Adj.
3.Tap [OK].
4.The display will show the current value blinking.
5.Wait for the value to stabilize.
6.Use [UP] / [DOWN] navigation to adjust the value to 0.
7.Enter [OK] then detector return to main menu.
8.Turn off gas flow and remove the calibration adapter from the sensor or disconnect tubing.
Note : Ambient air can be used to zero the sensor instead of nitrogen or Zero Air if the area is known to be free of the target gas or any gas to which the sensor may be cross-sensitive. In this case, no cylinder or calibration adapter is needed for the zero calibration.

For span calibration

1.Connect the regulator with 90 PPM ammonia cylinder adapter to detector then adjust the flow to 0.5 l/min
2.Press down navigation key for 5 sec its showing -0- Adj. press down its showing SPn Adj
3.Tap [OK].
4.The display will show the current value blinking.
5.Wait for the value to stabilize.
6.Use [UP] / [DOWN] navigation to adjust the value (As mention on cylinder certificate, means span cylinder gas concentration).
7.Enter [OK] then detector return to main menu.
8.Turn off gas flow and remove the calibration adapter from the sensor or disconnect tubing.
General Preventive Maintenance : In every 6 months once, carry out the calibration of gas detector.

Reference : Drager Manual



Labels:

Comments

Post a Comment

Popular posts from this blog

PLC Program for Mixing Tank

 Create a ladder diagram for controlling a batch mixing process. Implement a PLC program for mixing tank or Mixing Process using PLC Ladder Logic. PLC Program for Mixing Tank Fig : Mixing tank A tank is used to mix two liquids. The required control circuit operates as follows: A. When the START button is pressed, solenoids A and B energize. This permits the two liquids to begin filling the tank. B. When the tank is filled, the float switch trips. This de-energizes solenoids A and B and starts the motor used to mix the liquids together. C. The motor is permitted to run for 1 minute. After 1 minute has elapsed, the motor turns off and solenoid C energizes to drain the tank. D. When the tank is empty, the float switch de- energizes solenoid C. E. A STOP button can be used to stop the process at any point. F. If the motor becomes overloaded, the action of the entire circuit will stop. G. Once the circuit has been energized, it will continue to operate until it is manually stopped. Solution...
1 comment
Read more

Ferrules and Cross Ferruling

 Ferrules are identification labels provided for every wire terminations in an instrument, equipment, or electrical/instrumentation control panels. These tube-shaped sleeves can be inserted easily on each individual wire in a multi-core cable. In earlier days fixed digits/letters are used as ferrules, but now Instrumentation engineers/technicians prints out desired ferrules by using a ferrule printing machine. Typical Ferrule The numbers/ letters on the ferrules will be given as per the approved electrical hook up or loop diagrams. This helps technicians to easily identify a particular loop/wiring from a series of terminal blocks and to troubleshoot the desired terminal connection. Separate numbers on the ferrules distinguish the positive and negative polarities of wires, thus ensure the polarity protection of the instrument. Cross Ferruling  As a wire is connected on its both ends, it is quite useful to use a cross reference method for wire identification. Unlike normal ferru...
Post a Comment
Read more

What is Relay? How it Works? Types, Applications, Testing

 We use relays for a wide range of applications such as home automation, cars and bikes (automobiles), industrial applications, DIY Projects, test and measurement equipment, and many more. But what is Relay? How a Relay Works? What are the Applications of Relays? Let us explore more about relays in this guide. What is a Relay? A Relay is a simple electromechanical switch. While we use normal switches to close or open a circuit manually, a Relay is also a switch that connects or disconnects two circuits. But instead of a manual operation, a relay uses an electrical signal to control an electromagnet, which in turn connects or disconnects another circuit. Relays can be of different types like electromechanical, solid state. Electromechanical relays are frequently used. Let us see the internal parts of this relay before knowing about it working. Although many different types of relay were present, their working is same. Every electromechanical relay consists of an consists of an Elect...
1 comment
Read more