LAWSON ENGINEERS LTD Ref : PJ1682
Issue Date : 06.06.2006
1.3 A-FRAME
See drawing SW1618C-0001
‘A’ Frame Assembly
The base (skid) is manufactured as a weldment from universal column and rolled steel
channel. The floor surface is covered with chequer plate which has a non-slip coating
applied under the topcoat of paint. The skid has the capability of extending outboard to
provide extra space for maintenance and to allow for the storage of the T.M.S. when
separated from the R.O.V.
Note - In the extended position the trolley is capable of supporting the full SWL (ROV +
TMS + Work Package). We recommend however that the trolley be not loaded thus
Offshore. The trolley is capable of supporting the TMS offshore.
The skid is capable of having the umbilical winch mounted in two positions, either
directly on top at the rear, or separate from the skid at some distance behind.
The skid is fitted with four lifting eyes for transport as well as lashing down points for
securing the ROV during transit voyages. The lifting eyes are rated for lifting the skid,
‘A’ frame and snubber but not the ROV or TMS.
The ‘A’ Frame is manufactured from rectangular hollow section and is capable of
handling various T.M.S. / R.O.V. / toolskid combinations. This is achieved by
hydraulically powered extension pieces that vary the length of the ‘A’ frame legs.
The cross beam has pinned connections for the snubber assembly.
Lift eyes are provided for the lifting of the legs and each sub assembly of the A-frame.
External face of leg pieces fitted with ladder rungs to permit access to the docking /
snubber and pulley assemblies.
Static guides are welded to the legs to aid guidance of the R.O.V. / toolskid assembly as it
moves between the legs during recovery.
The legs are moved by hydraulic rams that feature built-in counterbalance valves. The
ram mounting brackets have two positions on the skid to achieve a lower stowed position
for transport.
1.4 SNUBBER
See drawing SW1673D-0001 Snubber Assembly
The function of the snubber is twofold – firstly to capture the vehicle on mechanical
latches in order to take the strain off the umbilical cable during launch/recovery
operations, and secondly to align the vehicle and hold it in position while passing it
between the ‘A’ frame legs.
The assembly comprises of a damping frame pinned to the crossbeam that controls the
fore and aft swing. The sheave is pinned to the damping frame and articulates
transversely. The lower frame is suspended from the damping frame by a pair of hoist
cylinders and also guides the sheave. The hoist cylinders control both the side-to-side
motion of the snubber and the up and down motion. Mounted to the lower frame by a ring
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