A crane that loses a tire loses the yard
An RTG lifts forty-tonne containers on eight tires that carry the whole portal. On this class of machine the tires are not a consumable line item the way they are on a road truck — they behave much more like structure. When one runs low, load shifts to its neighbours, the portal tilts slightly, the drive motors work harder, and rolling resistance rises on every one of the thousands of short moves a yard makes in a shift.
Fleets usually discover a slow leak the expensive way: a fitter checks pressures by hand at the end of a week, or a tire fails in a peak hour and the block stops. An RTG TPMS is not primarily about tire cost. It is about keeping a machine that costs far more than the tires in service.
So the question buyers bring to us is narrower than "should we monitor tire pressure". It is: fit at build, or retrofit the cranes already in the yard?
What makes an RTG a different problem
Four things separate an RTG from a highway vehicle.
Load, not speed. The tire carries a very high vertical load at walking speed. A pressure error shows up as casing stress and irregular wear rather than as heat generated by speed.
A stationary machine. A yard crane sits for minutes at a time between moves. That is a gift for radio and for leak detection: a slow leak has time to register before the machine travels again.
A cabinet you can reach. The electrical cabinet is accessible, dry and already has a DC supply. Our receiver runs on DC 10–30 V, which covers the 24 V control supply used on most cranes, so no extra converter is normally needed.
Environment. Dust, rain, washdown and yard debris. The sensor has to survive all of it, which is why the enclosure rating matters more here than in a truck: IP68.
Retrofit: what you gain, what it costs
Retrofit is usually the right answer for a fleet that already exists — and for most buyers that is the whole fleet.
What you gain:
- No dependency on the next crane order. You instrument the machines you already run, in the order that hurts most.
- A smaller, reversible project. The crane keeps its controller. TPMS arrives either as a second data source or as a driver display.
- A faster trial. Fix the configuration on one machine, then repeat the same bill of materials across the yard.
What it costs:
- A working window. Nobody stops a yard for a TPMS install. The work has to fit a scheduled maintenance slot, which means sensor count, repeater plan and harness length should be settled before the crane comes out of service.
- Cable routing. The wheel positions are easy. The path from the receivers back to the cabinet along a steel structure is the part that takes planning.
- Someone has to own the interface. If nobody on your team can accept a CAN frame or a Modbus register, the data stays on a cab display. That is still useful, but it is not integration.
Front-fit: when to specify it at build
Front-fit means the crane builder owns the whole chain. The harness is designed in, the wheel map matches the axle drawing, and the interface to the machine's own controller is part of the delivery documentation.
Specify TPMS at build when you control the crane specification, when the machine's controller is being written anyway, and when you want a single supplier accountable for tire data end to end. The result is cleaner: sensor IDs and the wheel map get recorded against the machine serial number instead of being assembled from a commissioning note.
The trade-off is flexibility. A front-fit decision is made once, early, usually before the yard knows exactly how it wants to use the data.
Five questions that settle it
1. Can the crane's existing controller take the data? If it already reads CAN or Modbus, retrofit is straightforward. If the only path is a cab display, decide now whether that is enough.
2. How many wheel positions, and how many receivers? One receiver supports up to 256 wheel positions, so an RTG is small in wheel count and the receivers are not the constraint. Reaching the far corner of the portal with a reliable radio link is.
3. Where does the receiver go? Cabinet, mast, or next to the wheel group. This decision sets harness length and therefore cost.
4. Who terminates the harness? Your electricians or ours. This is the most common source of schedule slip.
5. What happens to the data? A closed loop that derates the machine, a maintenance alert, or a report. The answer defines which protocol documents you need.
The interface is the real specification
Pressure accuracy is a datasheet number. On an RTG the number that decides the project is how tire data reaches the machine. Our receivers output CAN 2.0B at 250 kbps by default with a 500 ms data period, and both are software-configurable. J1939, RS485, RS232, Modbus RTU, PROFINET and UART are supported on the same platform. We supply a message map or DBC file, an alarm semantics document and a connector pinout, so your electricians wire it once.
A TPMS that nothing can read except its own display is a gauge. A TPMS that appears on the crane controller is a protection function.
What actually fails first
In port machinery work the sensor is rarely the problem. The failures we see are mechanical and human:
- A sensor fitted without the right torque, or onto a valve stem that was already tired.
- A repeater omitted on a long portal, leaving one corner reporting intermittently.
- An alarm threshold left at the factory default, so the operator learns to ignore it.
- Nobody re-commissioned the wheel map after a tire change.
All four are avoidable, and none of them is fixed by a better sensor. Ask any supplier how they handle the fourth one — that is the difference between a system that is installed and a system that still works in year three.
How we work
GZVIA designs and builds the sensor, receiver, repeater, display and cloud platform in-house in Shenzhen. We supply port machinery builders under their own brand, at around 600 units a year across that segment. The internal sensor is rated from −40 to +125 °C and the external sensor from −20 to +85 °C, with pressure accuracy of ±7 kPa and tire temperature accuracy of ±3 °C.
If you are deciding between retrofit and front-fit, send us the wheel count, the cabinet supply and the controller that has to receive the data. We will reply with a configuration, a repeater plan and the protocol documents you will need.
Read more on TPMS for port machinery, see the RTG crane installation, or send us the machine details.