Monitoring at Bardon Hill
Two Milltronics Mercap units have replaced capacitance rope level monitors to measure the level of limestone filler at Aggregate Industries' Bardon Hill Quarry in Leicestershire.
Mounted at the top of two 10.25m high silos, the Mercap units provide continuous level measurement with high alarms. Limestone filler is stored in the two 56-tonne silos before being piped out for mixing. The Mercap units provide visual and audible local alarms for lorry drivers delivering product to the silos, together with remote alarms which are displayed in the control cabin. As well as reading a digital display of the level, the driver receives an early warning of possible overfill problems.
The level of limestone filler is monitored in each silo by a vertically mounted Mercap unit. The filler forms a dielectric between the silo wall and the probe and the resulting capacitance value is converted by the Mercap unit to a signal that is proportional to the level of the contents in the silo.
The system consists of two probe components - an active shield and an active measurement section. The active shield is electrically isolated from the measuring portion of the rod and joined to the high-integrity process seal. The electronic transmitter, which converts the variable capacitance from the probe into a standard 4-20mA or Hart process signal, is housed in an explosion-proof enclosure.