Dredgers used at Swansea & Port Talbot
The following article on the ‘Afan’ is an extract from The Eagle comic dated 17th November 1962
There is always work for dredgers. Shifting sands and mudbanks can threaten the safe navigation of ships in river estuaries and in the approaches to many ports and harbours. Channels have to be cleared at regular intervals and the spoil – mud or sand – dumped out at sea where it is out of harm’s way.
One of the latest suction dredgers is the twin–screw diesel electric Afan, built in the early 60’s by Richard Dunston Ltd. She works out of Cardiff, and her duties are to keep clear the approaches to the ports of Swansea and Port Talbot.
She has two large electrically driven pumps, each of which sucks up the spoil from the sea bed through two trailer suction pipes that are lowered either side of the vessel. Most of the water brought up with the spoil is then separated in a distribution box and returned overboard, leaving the solid matter to be fed into the ship’s two large hoppers. This is later dumped at sea through the doors at the bottom of the hoppers.
Two 920 h.p. diesel engines drive the generators which supply power to the propulsion motors and the suction pump motors. All the generators and the motors were built in the UK by Brush Electrical Engineering.
(This drawing was produced by L. Ashwell Wood. Several attempts have been made by ourselves and others to establish copyright ownership, but without success. We therefore trust that the copyright owner, should any exist, will not object to us showing the drawing on our site.)
Key to Numbered Parts
( 1 ) Suction nozzle on sea bed. (2) Starboard trailer suction pipe; another is on the port side (not shown). (3) Flexible joints. (4) Pipe joint which is lowered over the ship's side to connect with the suction valve and pump. (5) Stone separating box (6) and (7) Centrifugal suction pumps. (8) 250 h.p. pump motors. (9) Davit for lowering and raising the trailer suction pipe. These pipes are stowed on deck when not in use. (10) Discharge pipes to distribution box. (11) Forward hydraulic ram for operating hopper door. (12) Port trailer suction pipe davit. (13) Sluice valves, one either side, discharge spoil into forward hopper. (14) Forward hopper being filled. (15) Separated water being discharged overboard. (16) Davit for stowing trailer pipes on deck. (17) Port sluice valves. (18) Spoil distribution box to all six valves. (19) Starboard sluice valve to rear hopper (closed). (20) Trays for distributing spoil into hopper. (21) Chain pulleys for hopper doors. (22) Rear hopper; each hopper has a 500 cubic yard capacity. (23) Side buoyancy space. (24) Hopper discharge doors — six to each hopper. (25) Hydraulic ram for operating hopper doors. (26) and (27) Pumps, sluice valves, hopper door controls. All dredging operations are remote-controlled from the bridge, as is the propulsion machinery. (28) Streamlined funnel, with exhausts from engine-room. (29) Engine-room hatch and ventilator. (30) 16-ft. aluminium lifeboat. (31) Crew's accommodation. (32) Oil fuel bunker. (33) 920 h.p. Ruston Hornsby Diesel engines (port and starboard). (34) Propulsion generator. (35) Auxiliary lighting Generator. (36) Suction pump generator. (37) Circulation pumps. (38) Auxiliary Diesel generator. (39) and (40) 610 h.p. propulsion motors, driving the twin propellers. (41) Reduction gearbox. (42) starboard propeller. (43) Balanced rudder. (44) Stern anchor. (45) Anchor winch. (46) 12-ft. work boat.