DESIGN TEMPERATURE PHILOSOPHY

The design temperature shall be based on the maximum operating temperature plus a minimum margin of 20°F.  For equipment operating at ambient conditions, the upper design temperature shall be at least equal to a maximum black bulb temperature of 160°F unless it is insulated or other corrective action is taken.  Fire conditions will not be considered in establishing the design temperature of a vessel.

For process coolers, consideration should be given to designing downstream equipment for the upstream design condition. Reliance on devices such as temperature trips to protect downstream equipment in the event of cooling failure may introduce risk, as the instrument response time may not be sufficiently rapid to offer adequate protection. This will be reviewed on a case by case basis.

Compressor Suction Scrubbers

Compressor suction scrubber design temperatures are defined as the highest of the following:

a)     Maximum operating temperature at the compressor suction in the event of air cooler failure.

b)    Maximum recycle temperature (discharge minus JT drop across anti-surge valve) in the event of air cooling failure.

c)     Maximum normal operating temperature plus 50°F.

Compressor Discharge

Maximum operating temperature on compressor discharge will be defined as 20°F above the predicted maximum normal operating temperature to allow for lower efficiency at off-design operation.  The maximum discharge temperature shall be confirmed by the compressor vendor.

Shell and Tube Heat Exchanger

For shell and tube heat exchangers, whenever the shell side fluid is hotter than the tube side fluid, the design temperature on the tube side shall be made equal to the shell side design temperature.

Over Pressure Protection Requirements

Protection of equipment against overpressure and other excessive operating conditions shall be in accordance with API RP 14C (Basic Safety System), API RP 520 (Pressure Relieving Systems) and API RP 521 (Pressure Relief and Depressuring Systems).