Introduction
Summer brings high temperatures, high humidity, heavy rainfall, and frequent thunderstorms. These environmental conditions can significantly affect the reliability and accuracy of industrial instrumentation.
During hot and humid seasons, common instrument problems include:
- Measurement drift caused by high temperature
- Signal instability caused by moisture and condensation
- Transmitter damage caused by lightning surges
- Blockage or vaporization in impulse lines
- Control valve failures caused by wet instrument air
Therefore, regular summer inspection is essential to ensure stable operation, accurate measurement, and safe production.
The main inspection focus should include:
- Protection against high temperature
- Waterproof and moisture prevention
- Lightning and surge protection
- Prevention of blockage and cavitation
- Corrosion control
- Avoidance of false alarms and unexpected shutdowns
1. General Instrument Inspection
1.1 Check Instrument Temperature
High ambient temperatures and direct sunlight can affect electronic components inside field instruments.
Inspect:
- Pressure transmitters
- Flow meter converters
- Valve positioners
- Junction boxes
Common problems:
- Display black screen
- Zero-point drift
- Electronic component aging
- Output signal instability
Recommended actions:
- Avoid direct sunlight exposure
- Install sunshades where necessary
- Check whether instruments are installed too close to high-temperature pipelines
- Verify that unnecessary heat tracing is switched off
1.2 Waterproof and Moisture Protection
Summer rain and humidity are major causes of instrument failures.
Check:
- Junction box sealing
- Transmitter rear covers
- Cable glands and cable entries
- Local instrument panels
- Field cabinets
Moisture ingress may cause:
- Short circuits
- Signal fluctuation
- Terminal corrosion
- Insulation failure
Pay special attention to:
- Condensation inside junction boxes
- Damaged sealing rings
- Loose cable glands
1.3 Dust and Corrosion Inspection
High humidity combined with dust can form conductive dirt layers and accelerate corrosion.
Inspect:
- Instrument housings
- Supports and brackets
- Impulse lines
- Cable trays
- Protection covers
Check for:
- Rust
- Damaged insulation
- Blocked impulse lines
- Broken protective coatings
2. Temperature Instrument Inspection
( RTD, Thermocouple, Temperature Transmitter )
2.1 High Temperature Measurement Drift
Compare field temperature indication with DCS values.
If deviation occurs, check:
Thermocouple:
- Incorrect compensation cable polarity
- Aging or damage of extension wires
- Short circuits
RTD:
- Loose terminals
- Moisture inside junction box
- Broken sensor wiring
2.2 Thermowell and Installation Check
Inspect:
- Thermowell tightness
- Leakage
- Corrosion
- Mechanical damage
For high-temperature applications, check whether the thermowell shows:
- Burn marks
- Erosion
- Deformation
3. Pressure Instrument Inspection
(Pressure Transmitter, Pressure Gauge, Pressure Switch)
3.1 Vaporization and Gas Blocking in Impulse Lines
During summer, high ambient temperature may cause process fluids to vaporize.
Common applications:
- Hot water systems
- Hydrocarbon systems
- Ammonia systems
- Chemical processes
Symptoms:
- Unstable pressure indication
- Incorrect zero point
- No pressure output
Inspection:
- Check impulse line condition
- Verify condensate pot operation
- Remove trapped gas when necessary
3.2 Impulse Line and Valve Inspection
Check:
- Blockage in impulse lines
- Leakage points
- Root valves
- Three-valve manifolds
Summer temperature changes may accelerate:
- Gasket aging
- Valve leakage
- Seal failure
4. Flow Meter Inspection
(Orifice Flow Meter, Magnetic Flow Meter, Vortex Flow Meter, Coriolis Flow Meter)
4.1 Temperature Effects on Flow Measurement
Liquid Flow Measurement
High temperature may cause:
- Density changes
- Vapor formation
- Flow signal fluctuation
Gas Flow Measurement
Temperature increase causes gas expansion.
Check:
- Temperature compensation function
- Pressure compensation
- Calculation parameters
4.2 Magnetic Flow Meter Inspection
High humidity may reduce insulation resistance between electrodes.
Possible symptoms:
- Maximum flow display
- Unstable output
- No measurement signal
Check:
- Junction box sealing
- Electrode insulation
- Grounding connection
4.3 Vortex and Turbine Flow Meter
Inspect:
- Sensor condition
- Pipeline vibration
- Mechanical resonance
High vibration may cause:
- False signals
- Measurement instability
5. Level Instrument Inspection
(Radar Level Meter, Ultrasonic Level Meter, Magnetic Level Gauge, Displacer Level)
5.1 High Temperature Vapor Effect
For differential pressure level measurement:
High temperature may cause expansion of fill fluid inside capillary systems.
Possible problems:
- Zero drift
- Incorrect level indication
- Measurement error
Check:
- Capillary condition
- Reference side pressure
- Leakage points
5.2 Radar and Ultrasonic Level Meter
High temperature inside tanks may generate:
- Steam
- Condensation
- False echoes
Inspect:
- Antenna condition
- Condensation
- Product buildup
- Purge air system
5.3 Magnetic Level Gauge
Common summer problems:
- Float sticking
- Indicator failure
- Magnetic coupling failure
Check:
- Float movement
- External indicator response
- Difference between local and DCS indication
6. Control Valve and Positioner Inspection
Summer is a high-risk period for pneumatic control valves.
6.1 Positioner Temperature and Moisture
Check:
- Direct sunlight exposure
- Water ingress
- Alarm conditions
High temperature may cause:
- Positioner drift
- Slow valve response
- Calibration errors
6.2 Instrument Air Quality
High humidity increases condensate formation in compressed air systems.
Inspect:
- Air filters
- Pressure regulators
- Air dryers
- Drain valves
Wet instrument air may cause:
- Valve sticking
- Positioner malfunction
- Control loop oscillation
6.3 Valve Operation Test
Check:
- Valve stroke
- Response speed
- Hysteresis
- Leakage
Inspect packing:
- Valve stem leakage
- Aging seals
7. Instrument Air System Inspection
7.1 Moisture and Dew Point
Summer inspection should focus on:
- Air dryer operation
- Filter drainage
- Receiver tank drainage
Water contamination may affect the entire plant’s control system.
7.2 Air Pressure Stability
Typical instrument air pressure:
0.4–0.7 MPa
Check:
- Pressure fluctuations
- Compressor loading
- Leakage points
8. DCS, PLC and Control Cabinet Inspection
8.1 Cabinet Temperature
Check:
- Air conditioner
- Cooling fan
- Ventilation
High temperature may accelerate:
- Electronic aging
- Module failure
- Communication problems
8.2 Moisture and Dust Prevention
Inspect:
- Condensation
- Dust accumulation
- Cabinet sealing
8.3 Grounding and Wiring
Check:
- Loose terminals
- Grounding resistance
- Safety barrier condition
Poor grounding may cause:
- Signal interference
- Communication failure
- False alarms
9. Lightning, Static Electricity and Explosion Protection
9.1 Lightning Protection
During thunderstorms, inspect:
- Instrument grounding
- Surge protection devices
- Lightning protection modules
Lightning surges may damage:
- Transmitters
- PLC cards
- Safety barriers
9.2 Explosion-Proof Inspection
Check:
- Cable glands
- Flexible conduits
- Explosion-proof seals
Ensure:
- No damage
- Proper sealing
- No loss of explosion protection
10. SIS / ESD Safety Instrument Inspection
Safety instruments require special attention.
Check:
- Pressure switches
- Level switches
- Flame detectors
- Vibration monitoring devices
Important:
Never operate bypass switches or safety interlocks without proper authorization.
High temperatures may accelerate:
- Contact aging
- False triggering
- Sensor failure
11. Common Summer Instrument Failures Summary
| Problem | Possible Cause |
|---|---|
| Signal fluctuation | Moisture inside junction box |
| Incorrect pressure/level | Impulse line vaporization or blockage |
| Flow measurement error | Density change or gas expansion |
| Valve oscillation | Wet instrument air |
| Radar false level | Steam and condensation |
| Transmitter damage | Lightning surge |
| Display failure | High temperature exposure |
12. Summer Instrument Inspection Checklist
During routine inspection, record:
- Temperature indication deviation
- Pressure and level fluctuations
- Flow measurement stability
- Leakage points
- Abnormal noise or vibration
- Instrument air pressure
- Cabinet temperature
- Alarm and communication status
For critical equipment such as:
- Distillation units
- Gasification systems
- Storage tanks
- High-temperature process units
Inspection frequency should be increased during summer.
Conclusion
Summer environmental conditions create additional challenges for industrial instrumentation. Proper inspection and preventive maintenance can significantly reduce instrument failures, improve measurement accuracy, and ensure safe plant operation.
A systematic summer inspection program helps engineers identify problems before they become production interruptions.