Lawson A-frame

[mudflap276]

we are having an issue with some lawsons A-frames. on 2 systems, the left lufting lags. there is a 4-6 inch delay. in other words, when lufting outboard, the right leg has a 4-6 inch headstart and the left has to catch up. we have checked the counterbalance valves in the legs and double checked the piping and connections. the problem becomes that when landing the sub, one cannot get the snubber even all the way around and it pinches the rubber bladders and they become useless. the only way we have found to somewhat correct this is to raise the tele legs up a little when landing and snubber down a little more than normal. just another step that we have to add to the process. we have spoken to Lawsons and not much info from them. if anyone has an idea, please put it out and we will try it and let you know what happens.

thanks in advance,
Mud

[turtle]

Is it possible that the left circuit is seeing more resistance to flow, thus not kicking in until resistance on stbd side allows pressure to build up substantially? Any way to put restriction to pressure/flow on stbd side to see if they’ll move at same time? Maybe try capping flow to stbd to observe movement on port side completely independent of what stbd is doing.

[DANFROV]

Have you checked the Mob / Demobilisation valve?
it might have been only partially closed by mistake. (See Below for Lawson instructions)
———————————————————————————

1. Position skid, A-frame and snubber assembly on deck.
2. Weld the two outboard sacrificial weld brackets, bolted to skid, to the
deck.
3. Position Power pack adjacent to skid.
4. Connect A-frame main cylinder hoses to "A-frame erection valve" on
power pack.
5. Connect power pack power supply.
6. Turn mobilisation key switch on HPU panel. This isolates the winch safety
circuit.
7. Check motor rotation is correct, only motor 1 will operate during
mobilisation.
8. Start Motor 1 on the power pack, wait for motor to switch to delta, approx.
5 seconds.
9. Switch valve (98), drawing Sw1618X-0003, located at the rear of the Skid
(see fig 1), to supply oil to L.H. cylinder only.
10. Remove bolts from sliding cylinder mount of the R.H. cylinder.( See fig
2).
11. Extend the L.H. cylinder until the R.H. cylinder mount has slid into its
intermediate position. CAUTION – it is not possible to slide the cylinders
along the skid with the tall weld down brackets (for the winch) in place.
The fittings to the cylinders foul.
12. Bolt R.H. cylinder mount in place.
13. Remove bolts from L.H. cylinder mount.
14. Retract the L.H. cylinder, which pulls the L.H. cylinder mount forward
into its intermediate position.
15. Bolt L.H. cylinder mount in place.
16. Extend the L.H. cylinder until the R.H. cylinder mount has slid into its
forward socket.
17. Bolt R.H. cylinder mount in place. (Torque = 800Nm)..
18. Remove bolts from L.H. cylinder mount.
19. Retract the L.H. cylinder, which pulls the L.H. cylinder mount forward
into its socket.
20. Bolt L.H. cylinder mount in place. (Torque = 800 Nm).
21. Switch valve (98), drawing SW1618X-0003, to centre position
22. Disconnect power pack to A-frame hoses.

————————————————————————-

Dan

dan@workocean.com

Workocean Limited

[Ray Shields]

Certainly does sound like one cylinder is getting more pressure than the other (suich as the mob/demob valve partially moved from the normal operate position) as Dan suggests.

Are you able to put a pressure meter on each of the rams and check they are getting the same pressure?

[mudflap276]

we dont currently have spare gauges to put on 😕
i will certainly look at the mob valve. that never crossed my mind. i will report back shortly and let you know how that worked.

thanks very much gents

Mud

[mudflap276]

well it looks like counterbalance valves are the culprit. we suspected it before but today actually verified everything.

[Author]

Posts