Resistance temperature detectors (RTDs)
An RTD sensing element consists of a wire coil or deposited film of pure metal. The element’s resistance increases with temperature in a known and repeatable manner. RTDs exhibit excellent accuracy over a wide temperature range and represent the fastest growing segment among industrial temperature sensors.
Application of RTD:-
For Profenofos Expansion we ordered Temperature Transmitter with below details.
Type:- PT-100 (PT- Platinum) 02 wired RTD Type Temp. Range of Platinum:- -200 to 850 °C Proposed application Temp. Range to measured:- 0-120 °C
Application of Level Transmitter:-
For Profenofos Expansion we ordered two different types of Level Transmitter with below details.
1. Type:- Differential Pressure Type Application:- In Batch Tank bottom mounting
Principle:- Based on Pressure difference P=ρ*g*h Level can be measured Mounting:- Bottom Limitation:- Sp. Gr of Fluid inside Tank must be constant in order to get max. Accuracy
2. Type:- Capacitance Type Application:- In Treatment Vessel Top mounting Principle:- Based on change in Capacitance of rod/ sensor of height equivalent to Vessel Ht. Level can be measured Mounting:- Top with Rod/ Sensor to be deep inside vessel Limitation:- Dielectric Constant of stored fluid must be known & should be constant
3. Type:- Radar Type = Continuous Level measurement device Application:- Level measurement in storage Tank of Clean Fluid- TMA
Principle:- They use Radar waves which is electromagnetic waves in nature. This device actually measure Distance between Source to the upper surface of Tank fluid level by measuring the time of flight of wave. Types:- 1. Guided Wave Radar= Contact type use probe inside tank to guide the radio waves into process fluid inside tank. 2. Non Contact Type which will guide radio waves outside tank. Mounting:- Top with Rod/ Sensor to be deep inside vessel
Application of Flow Transmitter:-
Magnetic Flow Meter = Mag Flow Meter = Volumetric Flow Meter Application:- To measure Volumetric Flow Rate of Liquid/ Slurry Principle:- Farady’s Law which states that when electrically conductive Liquid passes via magnetic field it will induce voltage proportionate to Strength of Magnetic Field, Velocity of Liquid via pipe & Length of Pipe. This voltage is proportional to Velocity of liquid. So basically measuring velocity through voltage & convert to Flow Rate by equation Q= A * V Mounting:- Between Pipe where Flow is to be measured
Limitation:- Liquid which Flow is to be measured must be conductive enough, Conductivity must be > 10 microsemence/cm Can’t use to measure vol. Flow of Steam/ Gases Remarks:- We have given order to Yokogawa special made Mag Flow Meter to measure conductivity < 1 microsemence/cm because in our case conductivity of liquid is 1.5 microsemence
2. Vortex Type Flow Meter = Mass Flow Meter Application:- To measure Mass Flow Rate of Steam Principle:- When an object for obstruction is installed in the way of fluid it will cause vortex due to lowering the pressure & increase in velocity. So Meter will measure the frequency of formation of vortex, the mass flow rate can be obtained. Governing equations are as per below. St= (Frequency*Width of Obstruction)/ (Avg. Velocity of Fluid) Q=A*V= (A*Frequency*Width of Obstruction)/ St Mounting:- Between Pipe where Flow is to be measured line should always be flooded Limitation:- 1. Fluid must be able to produce sufficient pressure so it must be having sufficient velocity to produce vortex for flow measurement 2. Fluid must be free of solid must be clean doesn’t contain slurry 3. Fluid should be free of solid so clogging of bluff body/ obstruction can be prevented 4. Should be single phase
3. Coriolis Type Flow Meter = Mass Flow Meter Application:- To measure Mass Flow Rate of Liquid Principle:- When an object for obstruction is installed in the way of fluid it will cause vortex due to lowering the pressure & increase in velocity. So Meter will measure the frequency of formation of vortex, the mass flow rate can be obtained. Governing equations are as per below. St= (Frequency*Width of Obstruction)/ (Avg. Velocity of Fluid) Q=A*V= (A*Frequency*Width of Obstruction)/ St Mounting:- Between Pipe where Flow is to be measured line should always be flooded Limitation:- 5. Fluid must be able to produce sufficient pressure so it must be having sufficient velocity to produce vortex for flow measurement 6. Fluid must be free of solid must be clean doesn’t contain slurry 7. Fluid should be free of solid so clogging of bluff body/ obstruction can be prevented 8. Should be single phase
Thermocouples
A thermocouple consists of two wires of dissimilar metals welded together into a junction. At the other end of the signal wires, usually as part of the input instrument, is another junction called the reference junction, which is electronically compensated for its ambient temperature. Heating the sensing junction generates a thermoelectric potential (emf ) proportional to the the two junctions. This millivolttemperature difference between level emf, when compensated for the known temperature of the reference junction, indicates the temperature at the sensing tip. Thermocouples are simple and familiar. Designing them into syst ems, however, is complicated by the need for special extension wires and reference junction compensation.
Thermistors
A thermistor is a resistive device composed of metal oxides formed into a bead and encapsulated in epoxy or glass.A typical th ermistor shows a large negative temperature coefficient. Resistance drops dramatically and nonlinearly with temperature. Sensitivity is many times that of RTDs but useful temperature range is limited. Some manufacturers offer thermistors with positive coe fficients. Linearized models are also available.
