To connect the mud cleaner feed to the shaker via an extended sealable header box would entail mounting the mud cleaner parallel and within a meter to the original shale shaker. This in turn would cause problems using it as a mud cleaner as to effect proper solids control the primary shale shaker should be mounted above the angled sand traps, (compartment No 1 on Tank No 1) for proper solids control efficiency the mud cleaner must discharge its cleaned mud into compartment No 2 or 3 on Tank No 1. This would be a distance of several meters.
I would suggest the use of a flow divider fitted to the back of shaker No1 which can divert the flow of mud over either the shaker or the shaker and mud cleaner, the flow divider connects the shaker and mud cleaner via a 10” pipe,
Alternatively split the flow line after the bell nipple somewhere down the flow line, with a spade valve and a diverted pipe from this junction to the mud cleaner.
Please contact me if this is un clear.