Advanced Level Transmitters for Urea/Carbamate Services

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Advanced Level Transmitters for Urea/Carbamate Services

Prem Baboo

Dangote Fertilizer Projects

Abstract: -The microwave level meter can carry out measurement not only with corrosive/high pressure but also in a high temperature or under an environment with corrosive liquid/gases. Accurate measurement has been achieved even under adverse environment conditions. The microwave level meter contains the self-diagnostic function and informs you of a measurement error of the level meter as soon as possible. Non-contact radar level transmitters are used for the measurement of almost any liquid and many solids in storage tanks, vessels or during processing. Radar level measurement is a safe solution even under extreme process conditions (pressure, temperature) and bi phased liquid and vapours. Radar level transmitters work based on the time of flight measuring principle or time domain reflect metric type. Nucleonic transmitters or nucleonic control systems (NCS) are used in urea plants to improve the quality process optimization and accuracy of the control reliability. In some plants stripper nucleonic LT are using for level measuring.The phenomenon of reducing the intensity of gamma radiation when passing through liquids or solids is used in nucleonic devices for measurement of level of liquids and solids. A gamma-detector converts the gamma-radiation into the output signal. In Old plant having nucleonic LT or delta P type LT can easily converts into Radar LT. and it is easy to install.

Key Word:- Radar transmitter, Nucleonic, Urea Plant, Corrosive, Radiation. Carbamate, urea. Differential pressure. Gamma radiations.

INTRODUCTION

Urea carbamate solution is very corrosive and urea process having high temperature at this conditions measuring level in high pressure urea synthesis equipment like HP stripper and HP carbamate separator level and also Medium pressure absorber which is heart of the Urea plants are not an easy job. Extreme process conditions especially with respect to the corrosiveness of the process media and the nature of the equipment involved eliminate most of the measuring principles available. Numbers of the old plants are using delta p type transmitters in stripper. One of the very few reliable techniques uses radioactive sources (gamma radiations) to measure level and is thus more or less common practice in urea plants. Now a days it is practices to coverts these types of LT into radar LT. The phenomenon of reducing the intensity of gamma radiation when passing through liquids or solids is used in nucleonic devices for measurement of level of liquids and solids. . A gamma-detector converts the gamma-radiation into the output signal (a series of small current pulses) however radar-based non contacting measurement has become feasible because the increasing computing power is able to deal with the necessary advanced signal processing. Using appropriate construction materials this technology offers a perfect alternative.

UREA PROCESS DESCRIPTION

The urea process is characterized by a urea synthesis loop with a reactor operating at about 140-175 kg/cm2 (g) (for stripping process) with ammonia to carbon dioxide molar ratio at urea reactor inlet of 2.8 – 3.9. This allows a CO2 conversion into urea of 60 – 68% in the reactor itself, also perforated trays which prevent back-flow maintained plug flow and favour gas absorption by the liquid. Different type of HET vortex mixture with booster is used now a day to increase the conversion rather than vessel size and pressure. Different types of HET are developed like super cup etc. There are two kinds of chemical reactions at the same time in the urea reactor:

2NH3 + CO2 NH2-COO-NH4 + 136230 kJ/kmol of carbamate (at 1.03 kg/cm2; 25°C); NH2-COO-NH4 NH2-CO-NH2 + H2O – 17575 kJ/kmol of urea (at 1.03 kg/cm2; 25°C)

The First reaction is strongly exothermic and the second one is weakly endothermic and occurs in the liquid phase at low speed. Downstream the urea synthesis the decomposition (and relevant recovery) of unconverted chemical reagents is carried out in three subsequent steps: High Pressure Decomposition in H.P. stripper; Medium Pressure Decomposition in M.P. Decomposer and, finally, Low Pressure Decomposition in L.P. Decomposer. The decomposition reaction is the reverse reaction of the first one above showed, viz.: NH2-COO-NH4 2NH3 + CO2 (- Heat) and, as can be inferred from the equation, it is promoted by reducing pressure and adding heat. The urea reactor effluent solution enters the stripper, under slightly lower pressure than the urea reactor, where a fair part of the unconverted carbamate is decomposed, due to the stripping action of either NH3orCO2, so that the overall yield of the H.P. synthesis loop referred to CO2 is as high as 80-85% (on molar basis). Ammonia and carbon dioxide vapours from the stripper top, after mixing with the carbamate recycle solution from M.P. section, are condensed at the same pressure level of the stripper, in the H.P. carbamate condenser; thus producing the LS steam which is used in downstream sections.

After separating the inert gases which are passed to M.P. section, the carbamate solution is finally recycled to the reactor bottom by means of a liquid/liquid ejector, which exploits H.P. ammonia feed to reactor as motive fluid. This ejector and the kettle-type carbamate condenser above mentioned, allow a horizontal layout, which is one of the main features of Stripping process. Downstream of the stripper residual carbamate and ammonia are recovered in two recycle stages operating at about 17.5 kg/cm2

  1. (M.P. section) and 3.7 kg/cm2 (g) (L.P. section) respectively. Ammonia and carbon dioxide vapours coming from carbamate

    decomposition are condensed and recycled to H.P. section. The solution leaving the L.P. section arrives to the concentration section where process condensate is removed in order to reach a concentration of about 96 97% which is required to feed granulator. Urea Sections are characterized by the following main process steps: a) Urea synthesis and NH3, CO2 recovery at high pressure; b) Urea purification and NH3, and carbamate recovery at medium and low pressures; c) Urea concentration; d) Waste water treatment. Urea solution production unit is also provided with the following: Auxiliary installation; f) Steam networks; g) Condensate Recovery & Flushing networks. In urea plants different types of level transmitters are used, e.g. Nucleonic LT, Differential pressure type, Capacitance types and radar types LT, Float type in tanks etc.

    NUCLONIC LEVEL TRANSMITTERS IN STRIPPER

    In Urea plant HP stripper & HP carbamate separator have nucleonic level transmitters as shown in the figure-1&3, however some plant are replacing nucleonic into radar transmitters. The phenomenon of reducing the intensity of gamma radiation when passing through liquids or solids is used in nucleonic devices for measurement of level of liquids and solids. . A gamma- detector converts the gamma-radiation into the output signal (a series of small current pulses). The stripped source is more accurate as it radiates a long, narrow, uniform beam in the direction of the detector. As the level changes, the detector is covered and protected from the source and the corresponding response changes. The response is uniform and linear over the entire span, producing a linear signal that corresponds with changes in level. The point source works in a similar way to the strip source system, in that the strip detector measures the radiation from the source. The radiation sensed by the detector is still attenuated with level; however, the point source sysem produces a non-linear response with level change.The main component of this type of measuring device is the radioactive source. The two common types of radioactive sources are Caesium 137 (Cs 137) and Cobalt 60 (Co 60). The activity of the radioactive substance decreases with time.

    Fig-1

    The time taken for the activity of such a substance to halve is termed its half-life. Cobalt 60 has a half-life of 5.3 years while Caesium 137, on the other hand, has a half-life of 32 years. The detector for continuous measurement is a type of scintillation counter and photomultiplier. This type of sensing has the advantage of the high sensitivity of the scintillation crystals (compared to Geiger counters) coupled with the safety and economy of a point source. The point detector is also installed in very compact space. The rod scintillation counter is a rod of optically pure Perspex within which scintillation crystals are uniformly distributed. In the presence of gamma radiation, the scintillation crystals emit flashes of light which are then detected by a photomultiplier at the base of the rod and converted into electrical pulses.Number of plants are used Cobalt-60 radiation source for nuclear level transmitters each having activities 90 mili Ci and 21 Mili Ci respectively which will mounted on the stripper and carbamate separator which is permanently installed in the device for purpose of quality control as shown in the figure-1.

    Using radioactive measurements for the determination of the level in vessels is based on the absorption of gamma rays through the product being measured. The gamma rays are emitted by a source of known intensity and the remaining of the radiation after absorption is measured by a detector. The remaining intensity or radiation exposure at the detector primarily depends on the distance between source and detector according.

    I=K* Io/d2

    Where, I-intensity reaching the detector, K- material constant, Io- intensity of the source d distance between source and detector. Every single material, so urea solution, steel vessel wall, corrosion-resistant liner, insulation, air gap between detector and vessel wall etc. between the source and the detector absorbs part of the radiation and thus attenuates the original radiation according the following equation :

    I=Io*e-µ* *d

    Where,µ-absorption coefficient, -density of the material, and d -thickness of the material.

    Knowing the exact geometry of the vessel it can easily be calculated how much attenuation of the original signal occurs for the fixed parameters of the vessel like wall and insulation thickness, gap between detector and vessel wall etc. The only remaining variable is the level height (thickness of the urea solution). It is clear that the density of the urea solution as well as the density of the gas cushion above the solution is not constant, however during normal operation of the plant deviations on the level measuring signal are minor. Although other configurations are also possible, it is common practice that the radio-active source is installed within the pressure vessel and the detector outside. For the reactor a so-called rod source is used. The radioactive substance is present in the form of a mostly Co-60 wire. In case of the stripper the source is always a point source of either Co60 or Cs-137 material. In both cases the radioactive material is installed in a protecting tube. Typical intensities of Co-60 sources are 400 2000 MBq (Mega Bequerel) and for Cs-137 15000 4 0000 MBq. Typical configurations for both measurements look like this Although the radioactive measurements are quite reliable and robust they still have some disadvantages. First of all and the most obvious one as the name already explains, is radioactivity. Although the legislation with respect to the use, application and handling of radioactive sources is very strict, inexpert use can lead to serious incidents

    Fig-2

    RADIATIATION PROTECTION PROGRAME

    In urea plants activities involves measurements of level and densities of material using equipment's that the use of radioactive source. Plants are used Cobalt-60 radiation source for nuclear level transmitters each having activities 90mili Ci and 21 Mili Ci respectively which will mounted on the stripper and carbamate separator(train-1 &2 respectively)which is permanently installed in the device for purpose of quality control. Urea plants are committed to a radiation protection Programme (RPP) of highest quality. Likewise hereby commits to full and complete compliance with all relevant requirements in the Nuclear Regulatory Authority (NRA) Regulations for the control of ionizing radiation. Urea plants committed to the RPP is based on the fundamental principle that levels of radioactivity to be used, and exposure to all source of ionizing radiation are to be maintained as Low as reasonable Achievable(ALARA) as shown in the table-1.

    Fig-3

    SAFETY SYSTEM

    For the purpose of plants will always regular radiation protection training.

    1. All the radiation workers are always regular radiation protection training.

    2. Adequately shielded cabinet for storage of radioactive source will always be Available on the site.

    3. The cabinet is properly secured padlock and security.

    4. Radiation level and warning signs is posted with padlock and security.

    5. Radiation safety officer of plants or any person appointed by him is carried out all necessary measurements on the radioactive source on plant sites to ensure that and dose rate at 1 meter on the radioactive source on plant sites ensure that the source is still within its container and that the radiation level are not than the regulatory limits.

    6. All the radiation workers are properly enrolled for personal dosimeter.

OCCUPATIONAL DOSE LIMITS OF NUCLEONIC RADIATIONS

Sr. No.

Occupationally exposed adults

Annual limit (mili Sv)

As Low As Reasonably Achievable (ALARA).(mSv)

1

Total Effective Dose Equivalent

20 average over 5 years

3

2

Total organ Dose Equivalent (except lens of the eye)

500

50

3

Eye lens Dose Equivalent

150

15

4

Declared pregnant woman

1 (to embro/foetus)

0.25 (to embro/foetus

Table-1

REPLACEMENT OF OLD LT WITH NEW TECHNOLOGY IN UREA PLANTS

Implementation of nuclear level detection method involves high cost as compared to other standard methods also risk in any damaged. Apart from the initial installation cost, there are some hidden costs associated with licensing and regular surveying a procedure varies from country to country. Other drawback of nucleonic LT is whenever the radiography for other equipment nearby done the level of vessel will be out. The nucleonic level sensors after being used must be discarded in an appropriate manner via properly authorized associations meant for this purpose only. This procedure also proves to be very costly. The nucleonic are now replacing with Radar technology as shown in the figure-4. Radar transmitters have been installed in number of urea plants in stripper, MP absorber & HP carbamate separators etc. with excellent and accurate results. Numbers of plant

replaced their old LT with radar LT and under construction and will be taken in operation soon. Radar transmitters can be applied in existing equipments in Urea plant. Required nozzle diameters for installing the measurement go down to 2. Deviating nozzle sizes must be investigated separately but in general it can be stated that a nozzle of at least 2 is sufficient for installing a radar level measurement. It might well be possible that existing smaller nozzles can be adapted without sacrificing th wall strength. However for these cases some additional engineering like MOC has to be done. In Urea Technology can offer these additional services. A proper design and the use of Duplex material and Titanium as a construction material for certain wetted parts of the instrument are a prerequisite for excellent resistance in the extremely corrosion sensitive urea synthesis and thus a trouble-free and reliable operation. Stripper replacement Nucleonic LT as shown in the figure-4

Fig-4

Some of the old plant stripper having delta P type LT. Because of the risk for crystallization of the impulse lines of the stripper. They needed to be tracing of steam with an additional disadvantage in this case was the extra amount of water being introduced to the process. As water has a negative effect on the urea conversion reaction, adding extra water should be avoided. In other differential pressure LT purge water is also given to avoid crystallization, e.g. MP absorber etc. The main problem with this type of measurement was however caused by the high pressure flush pumps necessary for purging the impulse lines a single plunger reciprocating pump is required to inject the water into Tapping and leakage from plunger and stuffing box leakages were the rule rather than the exception. when leakage started in plunger the level of stripper will not show actual. Flush pump failure inevitably caused the process medium to come in contact with the membranes of the measurement leading to corrosion and finally leaks. For the stripper level measurement for the stripper only the differential pressure type arrangement seemed feasible. Any other alternative measuring principle failed mainly because they are all based on the process medium being in

contact with the measuring element and thus were heavily sensitive for corrosion (e.g. capacitive or conductivity probe) or simply because the arrangement is not suited for the high synthesis pressures e.g. ultrasonic types. The usual construction materials used by instrument manufacturers were insufficiently corrosion-resistant and the use of exotic materials was still in the development stage and thus often too expensive to become attractive as an alternative. From the mid-seventies many urea reactors and strippers were equipped with radioactive level measurements and until recently this was the most used principle. The delta P type LT can be easily replaced with Radar transmitters.

DIFFERENT TYPES OF LEVEL TRANSMITTERS USED IN UREA PLANTS

A level sensor is one kind of device used to determine the liquid level that flows in an open system or closed system. Level transmitter is an instrument that provides constant level measurement and sends to control room signals. Level transmitters are used to determine the level of a certain plant vessel, equipments bulk-solid or liquid. Operational Control involves all manual, continuous and automated actions required to properly operate the process and keep the process within its operating window. Operational control consists of regulatory control, sequence control, manual manipulation and advanced process control. Emergency shutdown involves all unscheduled instrument actions, which are designed to place the process in a safe state if it moves out of its operating window towards an unsafe situation. Emergency shutdown consists of the protection against loss of life/serious injury, production loss, equipment and environmental damage. In normal operation, the output signal of the constraint controller is saturated, due to the deviation of the process variable from the set point; therefore, the override selector selects the output signal of the basic controller. In extreme conditions, the process variable is supposed to have reached the critical set point of the constraint controller; its output signal, not any longer saturated, becomes comparable to the signal of the basic controller. As consequence, one of the constraint controllers may take the control of the process, overriding the signal of the basic controller. External feedback shall be provided for selective control loops to avoid wind-up of the overridden controller. Output value going to the field (output of the signal selector) is given as external feedback to the controller not in regulating condition to avoid the saturation of the integral term of the non regulating controller.

Level Transmitters from fields are different to level switches, which only sound an alarm when the level of material reaches low or high and normal a predetermined level.

There are different types of level transmitters some of the types are following-

Level Measurement Two methods of Level Measurement

  1. Direct Measurement

    Direct Measurement uses methods such as visual Inspection displacement of float Tuning fork etc. Inferential measurement

  2. Inferential measurement uses methods such as pressure head time of flight etc. attenuation of radiation Change in Capacitance of material Photoelectric

Indirect Level Measurement

  1. Differential Pressure.

  2. Time of flight Ultrasonic

  3. Time of flight Radar Base.

  4. Nucleonic Level measurement Briefly all are shown in the figure-5

    Ultrasonic level Transmitters- In urea plant this type of transmitters used in chemical handling, e.g. sulphuric acid tank, molasses tank used in raw water treatments plant. Ultrasonic level sensors are used to detect the levels of sticky liquid substances and bulkiness materials as well. In this type of transmitter, an ultrasonic transducer is mounted at, or near the top of a container containing liquid. The transducer sends out an ultrasonic pulse. They are worked by producing audio waves at the range of frequency from 20 to 200 kHz. These waves are then replicated back to a transducer. The ultrasonic sensors response is influenced by turbulence, pressure, moisture, and temperature. Ultrasonic level meter (for material and liquid level measurement) is a non-contact highly reliable and cost-effective material level measuring instrument which is easily installed and maintained. Applied urea plants in sewage tank, mixing tank, reaction kettle, Wells, tanks, rivers, reservoirs, fuel, water depth or liquid level measurement.

    Guided Microwave Level Transmitters

    This type of transmitters used in ammonia storage tank in ammonia plants. This transmitters work by sending a microwave pulse through a sensor cable. The signal from field hits the surface of the liquid, and travels back to the sensor, and then to the transmitter housing. The electronics integrated in the transmitter housing determine the filling level based on the time taken by the signal to travel down the sensor and back up again. These types of level transmitters are used in industrial applications in all areas of process technology.

    Conductive sensors are used for point-level sensing conductive liquids carbamate such as water and highly corrosive liquids. Simply put, two metallic probes of different lengths (one long, one short) insert into a vessel and equipments. The long probe transmits a low voltage; the second shorter probe is cut so the tip is at the switching point. When the probes are in liquid, the current flows across both probes to activate the switch.

    Optical level sensors are used to detect liquids including poised materials, interface between two immiscible liquids and the occurrence of sediments. In urea plant effluents treatments plant area used. They are worked based on the changes of

    transmission in infrared light emitted from an IR LED. The interference from the produced light can be reduced by using a high energy IR diode and pulse modulation methods.

    Float switches are one of the most cost effective but also well proven technologies for liquid level sensing. This type of transmitters used in Urea storage tank, carbonate solution and waste spec tank in urea plants.A float switch includes a magnet within a float and a magnetic reed switch contained within a secure housing. The loat moves with the change in liquid and will cause the reed switch to either open or close depending on if its in air or liquid. Although simple in design, this technology offers long-term reliability at an attractive price point.

    Hydrostatic Level Transmitters

    Also known as pressure level transmitters, these transmitters help in determining fluid contents of a container by measuring the pressure of resting body of the fluid within it. The greater the force of liquid, the greater the volume of fluid.

    Fig-5

    RADAR BASED LEVEL TRANSMITTERS

    Radar level transmitters work based on the time of flight (TOF) measuring principle or time domain reflectometry (TDR). Radar (Radio Detection and Ranging) systems are widely used now-a-days in variety of applications including air traffic control, astronomy, air defense systems, ocean surveillance, ground penetrating radars for geological observations, flight control systems, and automotive radar for Intelligent Transport System (ITS). Spread spectrum techniques have some fine properties which make them an excellent candidate for Radar applications. Radar level transmitters provide non-contact type of level measurement in case of liquids in a metal tank. They make use of EM i.e. electromagnetic waves usually in the microwave X- band range which is near about 10 GHz. Hence, they can be also known as microwave level measurement devices.However, there are some differences between radar and microwave types. They are: Power levels in case of radar systems are about 0.01 mW/cm2 whereas in case of microwave systems, these levels range from 0.1 to 5 mW/cm2.Microwaves can work at higher energy levels; hence they are competent enough to endure extra coating as compared to radar level detectors.

    A radar level detector basically includes:

    A transmitter with an inbuilt solid-state oscillator, A radar antenna and A receiver along with a signal processor and an operator interface. The operation of all radar level detectors involves sending microwave beams emitted by a sensor to the surface of liquid in a tank. The electromagnetic waves after hitting the fluid's surface returns back to the sensor which is mounted at the top of the tank or vessel. The time taken by the signal to return back i.e. time of flight (TOF) is then determined to measure the level of fluid in the tank. To start with, we can measure the distance from the reference point to surface of a liquid. Then the meter sends a high-frequency signal from an antenna or along a probe. Radar-based devices beam microwaves at the process material's surface. A portion of that energy is reflected back and detected by the sensor. Time for the signal's return determines the level. Radar provides a non contact sensor that is virtually unaffected by changes in process temperature, pressure or the gas and vapour composition within a vessel. In addition, the measurement accuracy is unaffected by changes in density, conductivity and dielectric constant of the product or by the air movement above the product. Time of flight Radar Radar- based devices beam microwaves at the process material's surface. A portion of that energy is reflected back and detected by the sensor. Radar provides a non contact sensor that is virtually unaffected by changes in process temperature, pressure or the gas and vapour composition within a vessel.

    MEDIUM PRESSURE ABSORBER LEVEL TRANSMITTER

    In old plant the MP absorber having delta P type transmitters .In any fluctuations of the plant the density of the solution changed rapidly so actual level we cannot seen. Radar mounted directly on vessel which cannot be shutdowned should be provided with isolation valves (full bore type). In MP absorber case the trays are there so it is installed bottom part of the vessel where solution level is there.The radar transmitters are the only solution in this types of vessel as shown in the figure-6 &7 In Radar transmitters an accurate measurement of the level inside the MP absorber medium pressure absorber is important for the safety, reliability, and efficiency of this process equipment. If the actual level does not reflect the value being transmitted back to the control system, opportunities for unplanned shutdowns, equipment damage.Due to the presence of bi phased ammonia, CO2 and carbamate vapours in the vessel, the microwave pulses slow as they travel through the vapours. Because the transmitter knows exactly where the reflector is located, the distance the liquid surface is displaced can be used to calculate how much compensation is needed. This determines the correct distance to the liquid surface pulse and outputs the correct level back to the control system. Carbamate vapour condensation and deposits can affect the radar measurement performance. In this case, necessary heat tracing and a round piece of PTFE is installed in the mounting flange to prevent the accumulating on the radar gauge cone. A use of a purge is also considered.

    Fig-6

    Most important is medium pressure absorber which is the heart of the urea plant because the ammonia is separated from carbamate mixture. The excess ammonia feed in the reactor separated by this vessel. The gaseous stream, leaving the top of the stripper, after mixing with the recovered solution from the bottom of medium pressure absorber, enters the carbamate condenser, Except for incondensable gases; vapours are condensed and recycled to the urea reactor, by means of carbamate ejector. Condensing vapours at high pressure and temperature allows the production of saturated steam at 3.5 kg/cm2 (g) in the carbamate condenser. Incondensable gases, consisting of inert gases (passivation air plus inerts with CO2 from B.L.) and containing a little quantity of NH3 and CO2, come out from the top of the carbamate separator and flow directly into the bottom of the medium pressure decomposer.NH3-CO2-H2O mixture, partially condensed coming from Medium pressure condenser,

    enters in the bottom of the absorber. Gases consisting of NH3, CO2, H2O and inerts, rising from the bottom, are absorbed by cold liquid ammonia reflux sent to the top tray of the absorber. CO2 and H2O vapours will condense forming ammonium carbamate which falls back to the bottom. Absorption heat is removed by the evaporation of NH3 coming from ammonia booster pumps, thus a current of inert gases saturated with ammonia and containing just a few ppm of CO2 leaves the top of the rectification section at an operating temperature of about 44 °C. The bottom level and temperature must be kept constant at about 40 % and 79 °C respectively. In order to avoid that a temperature increasing on the trays of the column can result in CO2 carry over (with consequent failure of all the system due to plugs formation on top of this equipment); one thermocouple has been provided for each tray, in order to check constantly the operating value. In the event that the trays are clogged with carbonate, they can be washed with water to dissolve the solid by HW injection. The trays segments are perfectly tightened by gore tax Teflon type.

    Fig-7

    IMPROVED SAFETY AND RELIBILITYAND ENHANCING EFFICIENCY

    In corrosive fluid the contact type instrument got corroded resulted unnecessary shut down of the plant. After installation of this types (Radar) of level transmitter the 100% safe and secure of the plant. Processes that used to involve expensive equipment can now be achieved using creative, innovative and intelligent technologies that can be cost effective, reliable, robust, highly accurate and simple to install. Radar mounted directly on vessel which cannot be shutdowned should be provided with isolation valves (full bore type).Radar transmitters are available with a wide range of antenna designs and sizes for different applications. Radar transmitters are available for carbamate services, seals and housings to fit the process conditions and environment. Radar level measurement technique offer extremely accurate and reliable detection of level in storage tanks and process vessels.The performance ofradar level transmitters remains unaffected by heavy vapors and mostly all other physical properties of the fluid under level measurement (except dielectric constant of the liquid). Functional Safety relates to the overall safety of a system or piece of equipment that depends on corrosive and hazards environments or equipment operating correctly in response to its inputs, including the safe management of likely operator errors, hardware and software failures and environmental changes.

    CONCLUSION

    The urea process fluids is very corrosive we observed the benefits of radar measurements as an alternative for the traditional level measuring techniques like dp type, capacitance type in urea plants are obvious. The new technology in instrumentation the radar technology has been developed now radar is the proven and mature technology. The other types of technology are contact type there are chance of damage hence unnecessary loss of production. Increased processing power and improved electronic components made radar measurements available for the process industry and added reliability and accuracy to level measurement. Low Frequency Microwaves provide longer wave lengths which penetrate carbamate vapors, heavy vapour and condensation more easily. Wide beam angle can in some cases pass disturbances and turbulences of bi phased liquid and ammonia and carbamate vapors. The use of suitable and safe multi-interface level measurement systems would result in efficient separators, compact separator design, carbamate use and good quality products. To achieve this, different safe and cheap techniques have been investigated, e.g. externally mounted displacers, differential pressure transmitters, ultrasonic transducers, and gamma sensors, capacitance sensors with single or multi-electrodes, inductive and thermal sensors.

    LEGENDS-

    MOC-material of construction, MP-medium Pressure, HP-High Pressure, LT-Level Transmitter, B/L-Battery limits.

    REFERENCES

    1. Implementation of Radar Transmitter-Receiver using DSBPSK Modulation Technique by Ami Munshi#1 , Srija Unnikrishnan Vol-2,Issue-3,May-june- 2012.

    2. Radiotracers and Nucleonic Control Systems Applied in IndustryPolish Case by Andrzej G. Chmielewski, Tomasz Smoliski, Marcin Rogowski, World Journal of Nuclear Science and Technology, 2019, 9, 27-66.

    3. Third-Generation DC/DC Controllers Reduce Size and Cost by Randy G. Flatness, Linear Technology Volume-IX,Number-1

    4. High Power Monolithic Silent Switcher 2 Regulators Meet CISPR 25 Class 5 EMI, Fit Tight Spaces by Hua (Walker) Bai, Dong Wang and Ying Cheng,Journal of Power management,Vol-1,Number-1.

    5. Robust Industrial Sensing with the Temperature-to-Bits Family by Logan Cumming,Jounal of Analog Innovation, Vol-27 Number-1.

    6. Introduction to RADAR Systems by M. I. Skolnik, New York: McGraw-Hill,2001

    7. Role of Nuclear and Radiation Technologies in Oil, Gas and Coal Mining, Distribution and Power Sector Applications,2008, by Chmielewski, A.G, Nukleonika

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