M24M24(1975)(cont)(Rev.11976)(Rev.2Aug 2023)

Requirements concerning use of crude oil orslops as fuel for tanker boilers
M24.1 This UR applies to tankers where crude oil or slops are used as fuel for boilers, except
for the requirement(s) in this UR which create conflict with the statutory requirements related
to alternative design and arrangements required by SOLAS II-1/55 that do not need to becomplied with (i.e statutory requirements take precedence over this UR).
M24.12 In tankers crude oil or slops may be used as fuel for main or auxiliary boilers
according to the following requirements. For this purpose all arrangement drawings of a crude
oil installation with pipeline layout and safety equipment are to be submitted for approval ineach case.
M24.23 Crude oil or slops may be taken directly from cargo tanks or flow slop tanks or fromother suitable tanks. These tanks are to be fitted in the cargo tank area and are to be
separated from non-gas-dangerous areas by means of cofferdams with gas-tight bulkheads.
M24.34 The construction and workmanship of the boilers and burners are to be proved to besatisfactory in operation with crude oil.
The whole surface of the boilers shall be gas-tight separated from the engine room. Theboilers themselves are to be tested for gas-tightness before being used. The whole system ofpumps, strainers, separators and heaters, if any, shall be fitted in the cargo pump room or inanother room, to be considered as dangerous, and separated from engine and boiler room by
gas-tight bulkheads. When crude oil is heated by steam or hot water the outlet of the heatingcoils should be led to a separate observation tank installed together with above mentioned
components. This closed tank is to be fitted with a venting pipe led to the atmosphere in asafe position according to the rules for tankers and with the outlet fitted with a suitable flame
proof wire gauze of corrosion resistant material which is to be easily removable for cleaning.
M24.45 Electric, internal combustion and steam (when the steam temperature is higher than220°C) prime movers of pumps, of separators (if any), etc., shall be fitted in the engine room
or in another non-dangerous room.
Where drive shafts pass through pump room bulkhead or deck plating, gas-tight glands are to
be fitted.
The glands are to be efficiently lubricated from outside the pump room.
Note:
1.

Rev.2 of this UR is to be uniformly implemented by IACS Societies on ships contracted
for construction on or after 1 January 2025.

2.

The “contracted for construction” date means the date on which the contract to build thevessel is signed between the prospective owner and shipbuilder. For further details
regarding the date of “contract for construction”, refer to IACS Procedural Requirement(PR) No. 29.

Page 1 of 4

IACS Req. 1975/Rev.2 2023

M24M24(cont)M24.56 Pumps shall be fitted with a pressure relief bypass from delivery to suction side and it
shall be possible to stop them by a remote control placed in a position near the boiler fronts
or machinery control room and from outside the engine room.
M24.67 When it is necessary to preheat crude oil or slops, their temperature is to be
automatically controlled and a high temperature alarm is to be fitted.
M24.78 The piping for crude oil or slops and the draining pipes for the tray defined inM24.910 are to have a thickness as follows:
External diameter of pipes, dede88,9 88.9 mm< de114,3 114.3 mm < de152,4 152.4 mm ≤ de≤≤≤82, 5 82.5 mm
108 mm
139,7 139.7 mm

thickness, ttttt≥≥≥≥

6,3 6.3 mm
7,1 7.1 mm
8 mm
8,8 8.8 mm

Their connections (to be reduced to a minimum) are to be of the heavy flange type. Within theengine room and boiler room these pipes are to be fitted within a metal duct, which is to begas-tight and tightly connected to the fore bulkhead separating the pump room and to thetray. This duct (and the enclosed piping) is to be fitted at a distance from the ship's side of atleast 20% of the vessel's beam amidships and be at an inclination rising towards the boiler sothat the oil naturally returns towards the pump room in the case of leakage or failure indelivery pressure. It is to be fitted with inspection openings with gas-tight doors in way ofconnections of pipes within it, with an automatic closing drain-trap placed on the pump roomside, set in such a way as to discharge leakage of crude oil into the pump room.
In order to detect leakages, level position indicators with relevant alarms are to be fitted on
the drainage tank defined in M24.910. Also a vent pipe is to be fitted at the highest part of theduct and is to be led to the open in a safe position. The outlet is to be fitted with a suitable
flame proof wire gauze of corrosion-resistant material which is to be easily removable forcleaning.
The duct is to be permanently connected to an approved inert gas system or steam supply inorder to make possible:
injection of inert gas or steam in the duct in case of fire or leakage purging of the duct
before carrying out work on the piping in case of leakage.
M24.89 In way of the bulkhead to which the duct defined in M24.78 is connected, delivery
and return oil pipes are to be fitted on the pump room side, with shut-off valves remotely
controlled from a position near the boiler fronts or from the machinery control room. The
remote control valves should be interlocked with the hood exhaust fans (defined in M24.1011)
to ensure that whenever crude oil is circulating the fans are running.
M24.910 Boilers shall be fitted with a tray or gutterway of a height to the satisfaction of theClassification Society and be placed in such a way as to collect any possible oil leakage fromburners, valves and connections.
Such a tray or gutterway shall be fitted with a suitable flame proof wire gauze, made ofcorrosion resistant material and easily dismountable for cleaning. Delivery and return oil pipes
shall pass through the tray or gutterway by means of a tight penetration and shall then beconnected to the oil supply manifolds.

Page 2 of 4

IACS Req. 1975/Rev.2 2023

M24M24(cont)

A quick closing master valve is to be fitted on the oil supply to each boiler manifold. The tray
or gutterway shall be fitted with a draining pipe discharging into a collecting tank in pump
room. This tank is to be fitted with a venting pipe led to the open in a safe position and withthe outlet fitted with wire gauze made of corrosion resistant material and easily dismountablefor cleaning.
The draining pipe is to be fitted with arrangements to prevent the return of gas to the boiler orengine room.
M24.1011 Boilers shall be fitted with a suitable hood placed in such a way as to enclose as
much as possible of the burners, valves and oil pipes, without preventing, on the other side,
air inlet to burner register.
The hood, if necessary, is to be fitted with suitable doors placed in such a way as to enable
inspection of and access to oil pipes and valves placed behind it. It is to be fitted with a ductleading to the open in a safe position, the outlet of which is to be fitted with a suitable flame
wire gauze, easily dismountable for cleaning. At least two mechanically driven exhaust fanshaving spark proof impellers are to be fitted so that the pressure inside the hood is less thanthat in the boiler room. The exhaust fans are to be connected with automatic change over incase of stoppage or failure of the one in operation.
The exhaust fan prime movers shall be placed outside the duct and a gas-tight bulkhead
penetration shall be arranged for the shaft.
Electrical equipment installed in gas dangerous areas or in areas which may become
dangerous (i.e. in the hood or duct in which crude-oil piping is placed) is to be of certified safe
type as required by Classification Societies.
M24.1112 When using fuel oil for delivery to and return from boilers fuel oil burning units inaccordance with Classification Societies' Rules shall be fitted in the boiler room. Fuel oil
delivery to, and returns from, burners shall be effected by means of a suitable mechanicalinterlocking device so that running on fuel oil automatically excludes running on crude oil orvice versa.
M24.1213 The boiler compartments are to be fitted with a mechanical ventilation plant andshall be designed in such a way as to avoid the formation of gas pockets.
Ventilation is to be particularly efficient in way of electrical plants and machinery and otherplants which may generate sparks. These plants shall be separated from those for service ofother compartments and shall be in accordance with Classification Societies' requirements.
M24.1314 A gas detector plant shall be fitted with intakes in the duct defined in M24.78, in thehood duct (downstream of the exhaust fans in way of the boilers) and in all zones whereventilation may be reduced. An optical warning device is to be installed near the boiler fronts
and in the machinery control room. An acoustical alarm, audible in the machinery space andcontrol room, is to be provided.
M24.1415 Means are to be provided for the boiler to be automatically purged before firing.
M24.1516 Independent of the fire extinguishing plant as required by Classification Societies'Rules, an additional fire extinguishing plant is to be fitted in the engine and boiler rooms insuch a way that it is possible for an approved fire extinguishing medium to be directed on tothe boiler fronts and on to the tray defined in M24.910. The emission of extinguishing medium
should automatically stop the exhaust fan of the boiler hood (see M24.89).

Page 3 of 4

IACS Req. 1975/Rev.2 2023

M24M24(cont)M24.1617 A warning notice must be fitted in an easily visible position near the boiler front.
This notice must specify that when an explosive mixture is signalled by the gas detector plant
defined in M24.1314 the watchkeepers are to immediately shut off the remote controlledvalves on the crude oil delivery and return pipes in the pump room, stop the relative pumps,
inject inert gas into the duct defined in M24.78 and turn the boilers to normal running on fueloil.
M24.1718 One pilot burner in addition to the normal burning control is required.
End ofDocument

Page 4 of 4

IACS Req. 1975/Rev.2 2023