An increase in tankers disasters in the mid 1970s prompted the holding of a further conference on tanker safety and pollution prevention in 1978. This produced a Protocol requiring new tankers to be fitted with SBTs if the deadweight tonnage of the tanker is 20,000 or more and further, that the SBTs be protectively located, i.e. positioned in such a manner as to insulate the cargo tanks from the effects of a collision or grounding. The 1978 Protocol introduces stringent regulations regarding inspection and certification with the aim of giving strength and ‘bite’ to the 1973 Convention. This includes periodic surveys at intervals not greater than five years; an initial survey before the ship goes into service, or if it is an existing ship before the issuing to it of an International Oil Pollution Prevention Certificate. Where tankers operate exclusively between specific ports which are provided with adequate reception facilities whereunder tank washings and ballast water can be transferred conveniently to shore facilities, these tankers may then be exempted from the requirements of COW, SBTs or CBTs. This is provided that they do trade solely within national limits and/or areas designated and defined by the Convention. MARPOL required that governments of contracting countries should provide adequate reception facilities for oily residues not later than twelve months after entry into force of the Convention (i.e. twelve months from October, 1983) at the following categories of ports: Where crude oil is loaded into tankers which have only just completed a short sea passage. Where more than 1,000 tons of oil, other than crude oil, is loaded per day. Any port with repair or tank cleaning facilities. Any port handling tankers equipped with sludge tanks. All ports for oily bilges. All ports which handle bulk cargo, for oil residues. There is, however, no provision for sanctions to be available to tanker owners who suffer as a result of a contracting country’s failure to comply with these requirements.