How to Buy a Used Duty-Cycle Crane or Diaphragm Wall Rig
Duty-cycle cranes are built for continuous heavy work rather than occasional lifts, and they are the base machine for diaphragm walling, dynamic compaction and heavy grab work. The crane and the tooling it carries are separate purchases even when they arrive together.
These are the largest and most expensive machines in foundation work, and the practical constraints — transport, ground bearing, assembly time — often decide the purchase before the specifications do.
Duty-cycle rating is not lifting capacity
A duty-cycle crane is rated for sustained cyclic work, and its line pulls and duty ratings matter far more than its maximum lift. Establish the main and auxiliary winch line pulls and line speeds, and the duty classification.
A standard lattice crawler crane converted to duty-cycle work is not the same machine as one built for it, and the difference shows in winch and structural life. Establish which you are looking at.
Check the free-fall arrangement if the work needs it, and confirm the brakes and clutches associated with it have been maintained.
Winches, ropes and structure
Winches are the wear item. Inspect drums for grooving, check the ropes over their full length, and ask for rope certificates and their dates. Rope replacement on a machine this size is a significant cost.
Look along the boom sections for straightness and damage, and check the pins and connections. Ask whether all sections present are certified and matched to the machine — mixed or uncertified lattice sections are a serious problem.
Ask for the machine’s inspection and thorough-examination history. On lifting equipment this is not optional paperwork and its absence should stop the conversation.
Grabs and hydromills
For a mechanical or hydraulic grab, establish the panel width and thickness it is set up for, and confirm the jaws and cutting edges suit your ground. Check the verticality control arrangement, since panel accuracy is the whole product in diaphragm walling.
For a hydromill, the cutter wheels, gearboxes and the desanding arrangement are where cost concentrates. Establish the overhaul history of the wheel drives specifically, and confirm what desanding plant is included — it is a substantial machine in its own right and is often excluded.
Confirm the instrumentation works. Verticality and depth monitoring is what a client is paying for, and a system that cannot be relied on has to be replaced before the machine earns.
Transport, assembly and ground
These machines move in many loads and take days to assemble. Establish the number of loads, the assembly time and the crane required to assemble them, and price all of it before comparing purchase prices.
Get the ground bearing pressure for the loaded, working case. On soft sites this decides whether the machine can work at all, and the mat requirement can be a large cost of its own.
Inspection checklist
- Duty-cycle rating and winch line pulls established, not just lifting capacity
- Purpose-built or converted machine established
- Free-fall arrangement checked if the work requires it
- Winch drums and ropes inspected, rope certificates dated
- Boom sections checked for straightness, certification and matching
- Inspection and thorough-examination history obtained
- Grab panel width and thickness confirmed against your work
- Verticality control and depth instrumentation confirmed working
- Hydromill wheel drive overhaul history established
- Desanding plant confirmed as included or budgeted for
- Transport load count, assembly time and assist crane priced
- Ground bearing pressure obtained for the loaded working case
Frequently asked questions
What makes a crane a duty-cycle crane?
It is built for sustained cyclic work rather than occasional lifting: heavier winches, higher line speeds, structure and drives rated for continuous duty. A standard lattice crawler converted to the role is not equivalent, and the difference shows in winch and structural life.
Is the desanding plant usually included with a hydromill?
Often not, and it is a substantial machine in its own right. A hydromill without desanding plant is not a working system. Confirm in writing what is included before comparing prices.
What is the most commonly underestimated cost?
Transport and assembly. These machines move in many loads and take days to erect, usually needing an assist crane. Price the whole movement before comparing purchase prices, because it can change which machine is actually cheaper.
Browse cranes & diaphragm wall equipment on Piling Broker or read the other buyer’s guides.