Grasso RC-11 & RC-12 Overhaul Checklist for Ammonia Plants

Grasso RC-11 and RC-12 open-drive reciprocating compressors remain in service across cold storages, ice plants, and food factories in Pakistan, the Middle East, and Africa. When suction pressure climbs, oil carry-over increases, or valve-plate temperature spikes, a structured overhaul restores capacity faster than swapping the entire machine.

Start with isolation. Pump down the ammonia circuit, lock out the motor, and tag the starter. Record running hours, suction and discharge pressure, oil condition, and any knock or vibration the operators have logged. Photograph the nameplate so spare-part identification for RC-11 versus RC-12 is never mixed.

Strip in a clean sequence: coupling or flywheel, shaft seal housing, cylinder heads, valve plates, pistons, connecting rods, liners, then crankshaft inspection. Measure liner bore ovality, piston-ring gap, pin clearance, and crank-journal wear against the last overhaul sheet. Replace valve plates as a set — mixing worn discharge reeds with new suction reeds is a common cause of early callback.

Reassembly is where plants lose weeks. Fit new gaskets dry to the manufacturer pattern, set piston-to-head clearance, and torque in the documented star sequence. After the shaft seal is seated, laser-align the motor-compressor train. A few tenths of a millimetre of offset will destroy a new seal in days on an RC-11 or RC-12.

Commission with oil charge, leak test, and a staged load-up. Watch discharge temperature, oil pressure, and liquid carry-over for the first operating shift. AmmoniaEquip keeps pistons, liners, valve plates, connecting rods, and gasket sets for Grasso RC-11 and RC-12 so the shutdown window stays planned rather than open-ended.