Refrigerant Receiver Pump-Down Capacity

Answered before the shutdown rather than during it. The fill limit is the whole point. A receiver filled solid with liquid and then warmed has no vapor space to absorb the liquid's thermal expansion, and the resulting pressure rise is enormous and fast -- hydrostatic overpressure, which is a vessel rupture rather than a relief-valve event where there is no relief path on the liquid side. The customary 80 percent limit is therefore evaluated at the WARMEST liquid temperature the receiver could credibly see, not at operating temperature, because the dangerous case is a shut-down plant sitting in a hot machine room on a summer afternoon. The practical use is a go or no-go. A plant that discovers mid-shutdown that its receiver will not take the pumped-down charge has to either transfer to a rented recovery vessel or vent, and venting ammonia is a reportable release. The same arithmetic run backwards gives the maximum charge the receiver can accept, so a service plan can be built around what the vessel actually holds. Density is ENTERED at the warm condition because it is the input the answer is most sensitive to. This sizes no relief valve and does not check the receiver's pressure rating or its relief path. It is also not the portable recovery-cylinder rule, which covers a DOT cylinder on a scale where the basis is stamped water capacity rather than a plant vessel's gallons. IIAR 2, ASHRAE 15, and the vessel's own data plate govern.

available volume = receiver volume x fill limit - existing liquid; required volume = charge / (liquid density / 7.48052 gal per cu ft); the resulting fill is the sum over the receiver volume; the maximum charge is the available volume times that density.

The receiver fill-limit check as IIAR 2 and ASHRAE 15 practice writes it, evaluated at the WARMEST expected liquid temperature because the hazard is hydrostatic overpressure from liquid thermal expansion in a vessel with no vapor space. The customary limit is four fifths of the volume and is ENTERED. Gallons convert at 1728/231 cubic inches per gallon, exact by definition. It does not size a relief valve or check the vessel's pressure rating.

One volume balance and one density; no standard text is reproduced.

Estimate. AHJ and licensed professional govern.

Field names used by the API: receiver_volume_gal, existing_liquid_gal, fill_limit_fraction, liquid_density_lb_ft3, charge_to_pump_lb, density_lb_gal, available_gal, required_gal, resulting_fill_pct, spare_gal, max_charge_lb

• Density at the warm condition the answer is most sensitive to this inputthe plant's property data
• The fill limit is entered the customary limit is four fifths of the vessel volumeIIAR 2 and ASHRAE 15
• Not the recovery-cylinder rule recovery-cylinder covers a portable DOT cylinder on stamped water capacityEPA Section 608 practice