1. Scope and purpose
This manual covers maintenance and calibration procedures for radar level sensors (non-contact) and waveguide level radar (GWR) sensors that are widely used in Ukrainian industry for accurate level measurement of liquids, bulk materials and interfaces. Regular maintenance of these devices is critical to ensure their accuracy, reliability and longevity.
The maintenance work described in this manual is recommended as part of scheduled preventive maintenance, in the event of malfunctions, inaccurate readings, or after significant changes in the technological process. The goal is to maintain optimal performance of the level sensors and prevent unplanned production stoppages.
2. Precautions
CAUTION: Before starting any maintenance work, be sure to read the equipment manufacturer's instruction manual and follow all local safety regulations.
Lockout and Tag Out (LOTO): Always use the Lockout and Tagout (LOTO) procedure to isolate electrical energy and any other form of hazardous energy (pneumatic, hydraulic, mechanical, thermal) before starting work. Make sure all power sources are turned off and locked.
Depressurization and Drainage: If the sensor is installed on a container containing pressure or hazardous substances, the container must be depressurized and the product drained to a safe level or completely before opening any process connections.
Personal Protective Equipment (PPE): Be sure to use appropriate PPE, which includes (but is not limited to): safety glasses, protective gloves (chemically resistant if working with hazardous substances), safety helmet, safety shoes, and specialized protective clothing as determined by the risk assessment.
Hazardous substances: Be careful when working with containers containing aggressive, flammable, toxic or hot substances. Provide adequate ventilation and follow safety procedures when handling these materials.
Working at height: When working at height, use certified ladders, hoists or scaffolding. Always use safety equipment.
3. Necessary tools and materials
| Name of tool/material | Specification | Quantity |
|---|---|---|
| A set of wrenches | From 8 mm to 32 mm | 1 set |
| A set of hex keys | From 2 mm to 10 mm | 1 set |
| Torque wrench | Range: 5-50 Nm and 20-200 Nm (with calibration) | 2 pcs. |
| Screwdrivers | A set of flat and cross-shaped | 1 set |
| Multimeter | With VDC, mA, resistance measurement functions | 1 pc. |
| Power supply/current simulator | Ability to generate 4-20 mA | 1 pc. |
| Isopropyl alcohol (IPA) | Purity > 99% | 1 liter |
| Lint-free napkins | Industrial class | 1 package |
| Soft brushes | For cleaning delicate surfaces | 2-3 pcs. |
| Spare seals/gaskets | According to the manufacturer's specification (eg PTFE, Viton) | As needed |
| Thread sealant (optional) | Chemically resistant, for flange connections | 1 tube |
| Brush for removing dirt | Stiff bristles (for probes) | 1 pc. |
| Measuring tape/Laser range finder | Accuracy ±1 mm | 1 pc. |
| Computer/laptop with software for configuration | Appropriate manufacturer software (e.g. HART communicator) | 1 pc. |
4. Inspection before maintenance
Before starting work, perform a visual inspection and check of the system.
| Item | Verification | Acceptance/rejection criteria | Notes |
|---|---|---|---|
| Documentation | Availability of manufacturer's instructions, previous maintenance reports | Available, relevant | Check for model-specific data |
| Visual inspection of the sensor | The presence of mechanical damage, corrosion, leaks | Absence of visible damage, corrosion, leaks; strong attachment | Pay attention to the case, cable entries, technological connection |
| Cable connections | The integrity of the cable, the reliability of the connection, the absence of insulation damage | The cables are intact, securely fastened, with no signs of wear | Check the presence and condition of cable entries |
| Antenna/probe contamination | The presence of product deposits, dust, moisture on the radiating surface (radar) or probe (GWR) | Absence of significant deposits that may affect work | Especially important for radar antennas with a lens |
| Fastening | The strength of the attachment of the sensor to the flange/reservoir | Reliable fastening, no backlash | Check the tightening of the flange bolts |
| Ambient conditions | Temperature, humidity, vibration within operating parameters | Compliance with operating conditions | High vibration or temperature may cause malfunctions |
| Sensor readings | Comparison of current readings from SCADA/HMI with expected level | Readings are stable and within expected values | Record current readings for comparison |
5. Step-by-step procedure
5.1. Preparation and isolation
- Learning the documentation: View the sensor data sheet, manufacturer's (OEM) instruction manual, and wiring diagrams. Note specific model requirements, measurement ranges, and electrical characteristics.
- LOTO Application:
- Power Off: Disconnect electrical power to the sensor at the appropriate control panel or junction box. Apply a lock-out and tag-out (LOTO) procedure in accordance with the company's internal rules.
- Process Isolation: If the sensor is connected to a pressurized or hazardous container, close the container's inlet and outlet shut-off valves. Depressurize it if necessary for safe access to the sensor. Error: Incomplete isolation or failure to check residual pressure can result in injury.
- Check for no voltage: Using a multimeter (set to VDC), check for no voltage at the sensor power terminals. Expected value: 0V.
- Equipment Access: Install the necessary means of access (ladders, hoists, scaffolding) to reach the sensor safely. Make sure they are stable and comply with safety regulations.
5.2. Cleaning the radar antenna (non-contact sensors)
- Opening the housing (if necessary): If the antenna is inside a protective housing or you need to access the electrical connections, carefully open the sensor housing cover.
CAUTION: Be careful not to damage the gaskets or electronic components.
- Visual inspection of the antenna: Inspect the radiating surface of the antenna (lens, horn) for product deposits, dust, moisture, condensed liquid or mechanical damage (cracks, scratches).
- Cleaning the antenna:
- Wide a lint-free cloth with isopropyl alcohol (IPA).
- Carefully wipe the surface of the antenna, removing all dirt. For persistent deposits, use a soft brush dipped in IPA. Error: Using abrasive materials or aggressive solvents can damage the surface of the antenna, breaking its radio transparency.
- Make sure there are no traces or cleaner residue on the surface of the antenna. The surface must be clean and dry.
- Inspection of seals: Check the condition of the seals between the antenna and the sensor body, as well as the sealing of the process connection. Replace damaged or worn seals with new ones according to the manufacturer's specification (eg PTFE or Viton).
- Closing the case: If the case has been opened, close it carefully, making sure the seals are installed correctly. Tighten the mounting bolts evenly, according to the tightening torque specified in the manufacturer's instructions (typically 5-10 Nm for small covers).
5.3. Checking the waveguide probe (GWR sensors)
- Disconnecting the probe (if necessary):
- If access to the probe requires disassembly, carefully disconnect the flange or threaded connection of the probe from the process port of the vessel.
CAUTION: Make sure the container is completely drained and depressurized.
- Support the probe to prevent it from bending or falling.
- If access to the probe requires disassembly, carefully disconnect the flange or threaded connection of the probe from the process port of the vessel.
- Visual inspection of the probe:
- Inspect the entire probe for mechanical damage (bends, deformations), corrosion, abrasive wear, insulation damage (for coaxial probes) or any other defects. Error: Slight probe bends can cause signal loss or false readings.
- Check the integrity of the point of attachment of the probe to the body of the sensor.
- For probes with support points (for example, long rod probes), check their condition and secure attachment.
- Cleaning the probe:
- Remove all product deposits (eg sticky substances, crystals, scale) from the surface of the probe. Use a stiff bristle brush and appropriate solvents if approved by the manufacturer and safe for the probe material.
- Wipe the probe with a clean lint-free tissue moistened with IPA.
- Make sure the probe is completely clean and dry.
- Reinstalling the probe:
- If the probe was disassembled, reinstall it using a new gasket (eg DN50/PN16, PTFE).
- Tighten the flange bolts evenly in a criss-cross pattern with a torque wrench. The recommended tightening torque for DN50 flanges (M16 bolts) is 60-80 Nm, for DN80 (M16 bolts) - 70-90 Nm. For smaller threaded connections (eg G1
