Other bulkcarriers, perhaps designed for a particular trade, may be fitted with sophisticated discharging apparatus that operates on a conveyor belt and/or screw system (e.g. Siwertell System), loading being left to shore based equipment. Such machinery is usually tailored for a specific cargo type and trade – e.g. bulk cement – and is not normally suitable for a tramp bulkcarrier. With certain bulkcarrier sizes, however, ship’s gear is a definite disadvantage, trades having developed around sophisticated and speedy shore-equipment which needs clear, unhindered access to cargo compartments. Consequently, most panamax and almost all cape-size bulkcarriers are ‘gearless’ and close attention must be paid by their operators, charterers and brokers alike, that each vessel ‘fixed’ for a particular trade can physically fit beneath shore loading and/or discharging apparatus, not only when laden but, prior to commencement of loading and following discharge, in ballast condition. The dimension that determines a vessel’s suitability is the distance between the waterline surrounding the vessel and the top of her hatchway coamings – frequently referred to as the vessel’s ‘air-draft‘, and not to be confused with that other ‘air-draft‘, being the distance from the waterline to the top of the highest fixed point on a vessel. Unlike general cargo vessels it is unusual for bulkcarriers (especially older ones) to be fitted with electric ventilation, but many have fire-smothering (e.g. CO2) facilities serving cargo-holds. Most have steel hatch-covers, opening fore and aft on the majority of handy-sized vessels, whilst the larger vessels, from panamaxes upwards, are frequently fitted with hatch-covers opening sideways when, in the open position they cover the deck between coamings and the ship’s rail, supported by a steel framework to allow ship’s crew and shore workers to pass underneath when moving about the vessel’s decks. This enables a bigger open hatchway space than would otherwise be the case, the better to accommodate large shore-based cargo handling equipment and speedier cargo-handling.