A high discharge temperature trip is a protection, not a fault in itself. It exists because the compressor or blower is running outside the conditions it was designed for. Treating the trip as the problem, and resetting it without investigating, usually means the same shutdown returns within days. The useful response is to establish whether the cause sits in the cooling system, in the flow through the unit, or in the gas being handled.
What the trip is protecting
The protection is there to keep the machine inside its safe operating envelope. Excessive discharge temperature stresses seals, lubricants and internal clearances, and sustained operation in that condition shortens the life of the component that is hardest to replace. The trip is therefore a symptom that the unit is working outside its envelope, not a fault in the sensor that reports it.
The four causes that account for most events
- Reduced cooling, most often a fouled coil, restricted airflow or a cooling fan that is no longer performing;
- Low flow through the unit, where the gas path is restricted or the inlet is throttled;
- A change in the gas being handled, for example a warmer tank or a different fuel grade producing different vapour;
- Mechanical wear inside the machine, which raises the temperature needed to achieve the same pressure.
A step-by-step field check
Start with the simple, external observations before opening anything. Confirm that airflow around the unit is unobstructed, that the heat exchanger surface is clean, and that the cooling fan is running as it should. Then compare the current operating readings with the commissioning record: inlet and discharge temperature, pressure, and the flow through the unit. Only after those comparisons should the investigation move inside the machine.
Reading to cause
| Reading | Likely cause | Next check |
|---|---|---|
| High discharge temperature with normal flow | Reduced cooling capacity | Coil condition and airflow first |
| High temperature with falling flow | Restriction in the gas path | Check filters, traps and low points |
| High temperature only at certain times of day | Ambient heat load | Review cooling margin for site conditions |
| Gradual rise over weeks | Mechanical wear or fouling | Compare with commissioning data |
What not to do
Do not raise the trip setting to stop the shutdown, and do not bypass the protection to keep the station operating. Both actions hide the condition that the protection is reporting, and the consequence is usually a much larger repair later, at a time that is less convenient than the present one.
Common questions
Why does this happen more in summer?
Higher ambient temperature reduces the capacity of the cooling stage and increases vapour generation in the tank. Both effects push the unit toward its limit, so a unit with little margin in its cooling design will show the problem first in hot weather.
How often should the cooling surfaces be cleaned?
The interval depends on the site: dust, leaves and airborne contamination all vary. Checking at each scheduled service and cleaning when the surface is visibly loaded is more practical than relying on a fixed interval.
Is a single trip a reason to replace the machine?
No. A single event after a period of stable operation usually points to cooling or flow, which can be corrected. Repeated events that continue after those are addressed are what justify a closer look at mechanical condition.
Luoyang Wohong Petrochemical Equipment Co., Ltd. designs and manufactures vapor recovery units and membrane separation skids for gasoline stations and fuel depots. Contact us for system sizing, site survey and after-sales service.