Double bottom (DB) tank survey preparation:
DB tank survey is necessary to ascertain the condition of double bottom. Before opening DB tank manhole for survey, following procedure must be followed:
- Carry out risk assessment.
- Arrange all tools
- Sounding of DB tank and the tank in which remaining fuel oil is to be transferred must be taken.
- Make sure that there is same fuel in the other tank in which oil from tank to be inspected is to be transferred.
- If it is not possible then make sure that both oil are compatible.
- Empty the oil, strip with portable pumps if required
- Clean the tank with sea water and pump it out through the oily water separator
- Ventilate the tank(s) with a blower specially provided for the purpose, always cross ventilate i.e. there should be at least two openings, each for entry and exit for the air
- Check the space for explosive gases at various points suitably, more sampling should be carried out at the corners at the bottom most part of the tank
- Complete the enclosed space entry checklist before entry
- Before beginning any survey the survey team should ensure that a safety meeting is held to discuss all aspects of safety referred to herein with special attention being paid to gas testing procedures, command and communication links, and rescue arrangements.