Bulk carriers on ballast passage usually have their hatchcovers open partially in order to prepare the holds for loading the next cargo. They need fresh air, and illumination to do their job and also access to run hoses and supplies. They can work with hatchcovers closed but it is tedious.
The cleaning process requires sweeping the innerbottom and washing the bulkheads as well as cleaning the undersides of hatchcovers The quantity of work depends on the previous cargo. Some Cargo residues or stains might be difficult to remove without applying chemicals, then washing with high pressure seawater and rinsing with fresh water. It is important to do it right, because if the ship fails hold inspection at the load Port, the costs can be massive. For example, if s ship is coming in to load grain in a US port, any evidence of insects or weevils inside the hold will require a fumigation of all holds and the bill could be higher than a few hundred thousand dollars.
The hatchcovers are usually opened in fair weather at 0800 and secured with stoppers; and then closed before sunset.
If the weather is rough, hatchcovers are not opened.