Rotary screw compressor trips on high discharge temperature on hot afternoons?
Our rotary screw air compressor keeps tripping on high discharge temperature, but only on hot afternoons. It runs fine in the mornings and on cooler days. What should I check first?
High discharge temperature trips on hot afternoons often point to issues with heat rejection. The compressor is struggling to cool the air and oil when ambient temperatures are elevated. Start by checking the cooler's cleanliness and the oil level.
Likely causes and checks
1Fouled or blocked coolers
- Points to it
- Reduced airflow through the cooler or buildup on its fins prevents efficient heat transfer. This becomes more critical when ambient temperatures are high, as the cooler has less capacity to dissipate heat.
- Check
- Visually inspect the air-oil cooler and aftercooler for dust, dirt, or debris accumulation on the fins. Clean them thoroughly with compressed air or a suitable cleaning solution. Check for internal fouling if external cleaning doesn't resolve the issue.
2Low oil level or incorrect oil type
- Points to it
- Insufficient oil reduces the compressor's ability to cool the air during compression. Incorrect oil type might have a lower thermal stability or heat transfer capacity, leading to higher operating temperatures, especially under stress.
- Check
- Check the oil level in the separator tank. Ensure it's within the recommended range. Verify that the correct type and grade of compressor oil are being used according to the manufacturer's specifications. Top up or change oil if necessary.
3Poor ventilation in the compressor room
- Points to it
- Inadequate airflow in the compressor room leads to a buildup of hot air, which the compressor then draws in. This elevates the inlet air temperature, making it harder for the compressor to cool itself, especially on hot days.
- Check
- Check the compressor room's ventilation system. Ensure intake and exhaust fans are operating correctly and that air filters are clean. Verify there are no obstructions blocking airflow into or out of the room. Measure ambient temperature near the compressor inlet.
4Malfunctioning thermal bypass valve (thermostatic valve)
- Points to it
- The thermal bypass valve regulates oil flow through the cooler. If it's stuck closed or partially closed, too much oil bypasses the cooler, or not enough oil flows through it, leading to insufficient cooling and high oil temperatures.
- Check
- Isolate and lock out the compressor. Inspect the thermal bypass valve. It may need to be removed and checked for proper operation, ensuring it opens and closes correctly at its set temperature. Look for signs of sticking or damage.
Next check: After checking and cleaning the coolers, verifying the oil level and type, and ensuring proper room ventilation, if the problem persists, focus on the thermal bypass valve. If the valve is confirmed to be operating correctly, consider checking the discharge temperature sensor for accuracy.
What it typically looks like in the data
Related questions
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