MacGREGOR’s patented ‘hold overpressure system’ is a way of maximising the weathertightness of hatch covers. When the covers have been closed and cleated and all other openings including non-return drainage valves have been shut, the cargo hold is pressurised to a slightly higher pressure than the atmospheric one, to a maximum of 0.04 bar. All leaks caused by, for example, old sealing systems, or wear and tear in stoppers, can be prevented by pressurising the hold. The positive pressure is enough to ensure weathertightness even in case of several small leaks. Pressure in the hold is maintained by fans throughout the voyage – a relief valve ensures that the pressure is kept at the correct level and a pressure gauge is fitted on the bridge. The system works with CAT-profile, Flexseal and sponge seals.
Fittings needed for the ‘hold overpressure system are:
- air fans (capacity depends on the hold size)
- shut-off valves for non-return drainage valves
- pressure relief valve to ensure the correct pressure level in holds
- pressure gauge for checking the correct pressure level.