Tilbury Docks protects lifting kit with monitoring software

25 June 2010

Tilbury Port in London, UK has utilised condition-monitoring equipment from 4B Braime Elevator Components to protect a ship-unloader that was installed in the 1960’s. The port has two Marine Leg ship-unloaders, the main component of which are two rail-mounted, mobile Marine Towers.

Based on the then well known North American ‘Great Lakes’ design, the Marine Towers are quite unique within the UK. Although the equipment is more than 40 years old and has, since installation, handled many millions of tonnes of grain, it is still in excellent working condition and is a key element of the grain operations at the port.

When one of the Marine Legs was overhauled Port authorities decided to bring the condition monitoring up to date. The 4B Braime Watchdog Elite system was chosen and installed on the Marine Tower.

The Marine Leg is an extremely heavy duty, purpose built, bucket elevator; designed to be deployed into a ship's hold in order to dig into and unload grain cargo to shore. Raising and lowering of the leg, together with luffing, is achieved through a winch and rope system controlled by an operator in a cabin mounted high in the Marine Tower. The 35m long Marine Leg elevator operates at a capacity of 860 tonnes per hour, is fitted with 4B Braime HDPE CCS elevator buckets bolted to a continuous 1120mm wide belt and runs at a speed of 3.5 metres per second.

Belt under speed and misalignment are monitored by WDA High Power sensors which detect moving ferrous material, in this case bucket bolts - since non ferrous elevator buckets are being used. This is a non-contacting extended range sensor, designed to detect targets which are up to 100mm away. Sensors mounted either side of the Marine Leg casing monitor belt alignment.

Alarms for under speed are set at > 10 per cent for 180 plus seconds and immediate shutdown at > 20 per cent.

All four main conveyor shaft bearings are monitored for temperature with trips set at 80°C and alarms for 180 seconds and real-time readouts are given from 50°C - 120°C.

Blocked chute detection is provided in the infeed chute by the installation of a Binswitch capacitance style sensor that can detect plugs.

Andy Lamb, engineering manager at the Tilbury Grain Terminal, explained: “When the Watchdog gives us a first indication of belt slip and raises an initial alarm, we use this as a ‘trigger point’ to deploy our planned maintenance scheme. There is a strong correlation between that very early, slight ‘out of order’ condition and the timing of a service. By doing this our maintenance regime is tied to hours of machine usage not absolute time and therefore we only service when necessary. This saves valuable manpower resources and obviously money”.

Tilbury Docks is now looking to replicate the system on the second Marine Leg and, furthermore in addition has now decided to extend the Watchdog Elite system philosophy into the main silo block itself. The technology will be the ‘big brother’ of Watchdog – the T500 Elite. This system is capable of monitoring up to 256 inputs every 4 seconds and has full integration capability with the on-site PLC set up.

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