bids are invited for the period of comprehensive annual maintenance contract will be valid for a period of 1 years. the maintenance contract shall be comprehensive in nature and the contractor will be required to keep all the equipments in perfect working condition throughout the period of contract and no extra payment will be made for any repair, replacement of any part of the equipments gas charging etc to the contractor. bidders are, accordingly, instructed to quote all-inclusive rates per machine ( per unit ) for the maintenance of the equipment apparatus during the whole of the period of contract. ( b ) free repairing of the compressor / fans / motor. ( c ) free replacement of defective electrical / mechanical parts. ( d ) servicing including washing and cleaning of outer grill, filter etc on quarterly basis. ( e ) free gas charging ( except physical damage by monkeys ) ( f ) overhauling including servicing once a year.