Scope and purpose
This practical guide covers routine maintenance of industrial level gauges of the radar type and guided wave radar (guided wave radar) used to measure the level of liquids and bulk materials in tanks, hoppers and process vessels. The procedures are intended for the maintenance of devices in the chemical, oil refining, food and energy industries in accordance with DSTU EN 61508-1:2018 and ISO 55000:2014.
Maintenance is performed every 3-6 months depending on operating conditions, or when the readings deviate more than ±2% from the control values. Critically important for systems with an accuracy class of 0.2% according to DSTU EN 60770-1.
Safety measures
ATTENTION! Before starting work, it is mandatory to turn off the power supply and block energy carriers (LOTO) according to DSTU OHSAS 18001.
Dangerous factors:
- High voltage 24-230V DC/AC
- Radio frequency radiation 26 GHz (SAR level < 1.6 W/kg)
- Chemicals in Tanks - MSDS Check Required
- Working at a height of more than 1.8 m - the use of a safety belt is mandatory
Necessary tools and materials
| Name | Specification | Quantity |
|---|
| Torque wrench | 5-50 Nm, accuracy ±3% | 1 |
| Digital multimeter | True RMS, 4-20mA, 1000V AC/DC | 1 |
| Current loop calibrator | 4-20mA, accuracy ±0.02% | 1 |
| End heads | M6, M8, M10 (6-sided) | 1 set |
| Horn keys | 8, 10, 13, 17 mm | 1 set |
| Nylon bristle brush | Diameter 25 mm, length 150 mm | 2 |
| Napkins are lint-free | Cellulose, size 200x200 mm | 20 |
| Technical solvent | Isopropanol 99.9% | 0.5 l |
| Silicone grease | Temperature range -40...+200°C | 50 g |
| O-ring seals | NBR 70 Shore A (various sizes) | kit |
Inspection before maintenance
| Check element | What to check | Acceptance/rejection criteria | Notes |
|---|
| Device body | Mechanical damage, corrosion | Reject: cracks >0.5 mm, corrosion >5% of the surface | Photofixation of defects |
| Cable inputs | Connection density, integrity | Reject: loosening >0.5 revolutions | Tightening torque 8-12 Nm |
| Radar sensor antenna | Pollution, plaque, deformation | Reject: plaque >1mm, deformation | Teflon coatings are particularly sensitive |
| Waveguide (GWR) | Mechanical damage to the rod | Reject: bending >2mm, cuts >0.1mm | Replacement of the rod in case of damage |
| Indication of the device | Deviation from control values | Reject: error >±2% of range | Comparison with the reference level gauge |
| Output signal current | 4-20mA according to the level | Accept: linearity ±0.1mA | Measurements on terminals 3-4 |
| Operating temperature | The surrounding environment | Accept: -40...+80°C for standard execution | Verification of compliance of the passport |
| Mounting vibration | Rigidity of installation | Reject: backlash >0.5mm | Flange tightening torque 35-45 Nm |
Step-by-step service procedure
Preparatory works
- Perform the lockout and tagging (LOTO) procedure: turn off the power at the switchboard, hang a tag with the name of the performer and the date. A common mistake: working under voltage can lead to electric shock up to 230V.
- Record the current readings of the device in the service log: value 4-20mA, corresponding level in mm, fixation time.
- Photograph the general condition of the equipment for comparison after service.
- Check the body surface temperature - should be <60°C for safe touch. At a higher temperature, wait for cooling.
Dismantling and access to nodes
- Disconnect the power cable from the terminal box of the level meter. The moment of unscrewing the cable entry: 8-12 Nm (counter-clockwise).
- Open the cover of the electronic unit with a 10 mm key. Attention: there may be condensation inside - carefully wipe with a napkin.
- For radar devices: unscrew the protective cover of the antenna (torque: 15-20 Nm). Visual indicator of correct dismantling - the antenna is completely open, there are no distortions.
- For GWR devices: loosen the clamping nuts of the waveguide (torque: 12-18 Nm). Do not pull the rod completely out of the tank.
Cleaning the radar antenna
- Visually assess the type and degree of contamination of the antenna. Typical contaminants: dust (gray coating), product condensate (colored spots), salt crystals (white deposits).
- For light dirt: wipe the antenna with a tissue moistened with isopropanol. Movements - from the center to the edges, without strong pressure.
- For heavy dirt: use a nylon brush with a diameter of 25 mm. It is forbidden to use metal brushes - damage to the antenna coating!
- Check cleanliness: the surface of the antenna should be uniformly matte, without stains and deposits. Unacceptable solvent residues (visually - wet spots).
- Dry the antenna in the air for 5-10 minutes. Acceleration of drying with compressed air is allowed at pressure <2 bar.
Inspection of the guided waveguide
- Inspect the waveguide rod at the access length (usually 300-500mm from the flange). Look for: bends over 2mm, scratches over 0.1mm deep, product deposits.
- Measure the diameter of the rod at three points with a caliper: near the flange, in the middle of the accessible area, at the end. The deviation from the nominal diameter should not exceed ±0.1mm.
- Clean the accessible part of the rod with isopropanol and a lint-free cloth. Move only along the rod axis, not in a circle!
- Check rod connecting elements (if any): tightening torque 25-35 Nm for M12 connections, 15-25 Nm for M8.
- Visually assess the condition of insulators (usually Teflon): absence of cracks, chips, discoloration (yellowing indicates overheating).
Inspection of electronic components
- Inspect the boards of the electronic unit: no oxidation of contacts, swelling of capacitors, darkening of resistors.
- Measure the insulation resistance between the input terminals and the case with a 500V megohmmeter: it should be >10 MΩ at normal humidity.
- Check the integrity of the connecting wires with a multimeter: the resistance of each conductor is <1 Ohm for a length of up to 5 m.
- Inspect the terminal connections: the tightening torque of the terminal screws is 0.8-1.2 Nm (use a screwdriver with a torque limiter).
Device calibration
- Connect the current loop calibrator to the output terminals (usually 3 and 4). Install a 24V DC power supply.
- Put the device in the setting mode according to the manufacturer's instructions (usually a combination of buttons or DIP switches).
- Set Empty Tank Value (4mA): Set the reference level to 0% and adjust the output to 4,000mA ±0.02mA.
- Set Full Tank Value (20mA): Set the reference level to 100% and adjust the output to 20,000mA ±0.02mA.
- Check linearity at intermediate points: 25% (7,000mA), 50% (12,000mA), 75% (16,000mA). The deviation should not exceed ±0.1mA.
- Save the calibration in the device's memory and exit the setup mode. Common mistake: Forgetting to save settings results in loss of calibration.
Collection and inspection
- Install the protective cover of the antenna or clamp the waveguide according to the specification (points are specified in clause 7-8).
- Close the cover of the electronic unit, check the correct fit of the O-ring seal.
- Connect the power cable, tighten the cable entry with a torque of 8-12 Nm.
- Apply power and wait for the initialization of the device (usually 30-60 seconds, indicated by the blinking of the LED).
- Check the current of the output signal at the current level - it should correspond to the calibration of ±0.1mA.
Control check after service
| Test | Expected result | Actual result | Pass/Fail |
|---|
| Output signal at minimum level | 4.000mA ±0.05mA | ______mA | _______ |
| Output signal at maximum level | 20,000mA ±0.05mA | ______mA | _______ |
| Linearity at the midpoint | 12,000mA ±0.1mA at 50% level | ______mA | _______ |
| Response time to a change in level | <5 seconds for a 10% change | ______sec | _______ |
| Insulation resistance | >10 MΩ at 500V | ______MOm | _______ |
| Body temperature in operation | <60°C at +25°C ambient | ______°C | _______ |
| No diagnostic errors | Green light or code 00 | _______ | _______ |
| Mechanical fixation of the case | Absence of backlash >0.5 mm | _______ | _______ |
Diagnostics and troubleshooting
| Symptom | Probable cause | Elimination |
|---|
| The output current is blocked at 3.6mA | Complete loss of signal, dirty antenna | Clean the antenna, check the range settings |
| The output current is blocked at 22mA | Out of range, electronics error | Check installation height, recalibrate |
| Unstable readings (fluctuation ±0.5mA) | Foam on the surface, turbulence | Increase the averaging time to 10-30 seconds |
| Linear deviation over the entire range | Offset of the zero point | Recalibrate points 4 and 20mA |
| No response to commands | A break in the communication cable | Check the integrity of the wires, the connection of the terminals |
| Error E14 (overheating) | Electronics temperature >85°C | Check the ventilation, solar protection of the housing |
| Error E7 (echo too weak) | Low dielectric constant of the medium | Change antenna type or switch to GWR |
| Intermittent signal in GWR | Deposits on the rod, mechanical damage | Disassemble and clean the entire rod |
Maintenance regulations
| Operation | Periodicity | Estimated duration | Qualification of the performer |
|---|
| Visual inspection, antenna cleaning | Every month | 30 minutes | Locksmith of the 3rd category |
| Full cleaning, calibration check | Every 3 months | 2 hours | Electric locksmith of the 4th category |
| Full service with dismantling | Every 6 months | 4 hours | Electromechanic of the 5th degree |
| Major inspection with replacement of seals | Annually | 6 hours | KVP specialist and A |
| Verification of measuring equipment | Every 2 years | 8 hours | Certified metrologist |
Directory of spare parts
| Description of the part | Typical specification | Category UNITEC |
|---|
| O-ring sealing of the body | NBR 70 Shore A, diameters 20-200mm | Seals are industrial |
| Radar horn antenna | Frequency 26GHz, material PTFE/steel | Sensors and sensors |
| Waveguide rod | Steel 316L, diameter 6-12mm, length up to 20m | Components of KVPiA |
| Instrument cable | 2x1.5mm², shielded, temperature up to 105°C | Cable products |
| Terminal block | 4-pole, current 16A, voltage 600V | Electrical materials |
| Electronic block | Power supply 24V DC, output 4-20mA | Electronics of KVPiA |
| Connecting flange | DN50-DN200, PN16, material steel/stainless steel. | Pipe fittings |
| Antenna protective cover | IP67, material polyamide or aluminum | Cases and protection |
A complete catalog of compatible spare parts and consumables is available in electronic catalog UNITEC-D. For specific details, please contact our technical department.
Normative links
- DSTU EN 61508-1:2018 - Functional safety of safety systems related to electrical/electronic/programmable electronic devices
- DSTU EN 60770-1:2016 - Transmitters for use in industrial processes
- ISO 55000:2014 - Asset management. General overview, principles and terminology
- DSTU OHSAS 18001:2010 - Occupational safety and health management systems
- DSTU 2681-94 - Metrology. Terms and definitions
- Manufacturers' instructions: Rosemount 5400/5408, Endress+Hauser Levelflex M, Vega VEGAFLEX series
