CargoWatch CW/900-3A is a hold monitoring unit. It sits in the ship’s office or on the bridge, gathers readings from sensors distributed through the cargo spaces, and raises an alarm when a hold drifts outside the condition the cargo was accepted under. It is the least glamorous product we make and the one that most often pays for itself in a single voyage.
Why hold condition matters
Most cargo claims that reach arbitration are moisture claims. Steel sweats, grain heats, bagged cement takes up water and sets, and in almost every case the damage happens quietly over several days while nobody is looking inside the hold. A monitoring unit does not prevent any of this. What it does is produce a record — a timestamped series showing what the hold actually did — which changes the argument from an assertion into a document.
Sensor topology
The unit monitors up to 96 sensor drops across six holds. A drop is a string of sensors on a single cable run, typically three or four at different heights, because the whole point is to see stratification: warm damp air sitting under the hatch cover while the tank top stays cold. A single sensor per hold tells you almost nothing useful and we discourage it, even though it is cheaper and customers ask for it.
Alarm behaviour
Alarms are configured per hold, not globally, because a hold of steel coil and a hold of fertiliser want completely different limits. Humidity alarm hysteresis is fixed at 2.5 % RH and is not user-adjustable. This is a deliberate decision: field experience showed that customers given an adjustable hysteresis would widen it until the alarms stopped, which defeats the instrument. Temperature limits are freely configurable.
Records and export
The unit keeps its log internally and will export a voyage record for the ship’s file. The export is a plain delimited file rather than a proprietary format, on the reasoning that a record which can only be read by the manufacturer’s software is worth very little to a P&I club three years later when the software has moved on two major versions.
Ventilation decisions
Where the vessel has a dewpoint-based ventilation rule in its cargo care manual, the unit can display the comparison directly — hold dewpoint against outside dewpoint — so the decision to open or close vents stops being a matter of licking a finger and holding it up. This is not automation. The unit does not control the vents; it tells the officer of the watch what the numbers are.
Fitting
Cable runs are the hard part of a CargoWatch fit, not the head unit. Getting sensor cabling into a hold and protecting it from grabs, bulldozers and stevedores requires conduit routed with some thought, and it is normally done during a scheduled docking rather than alongside.