Levelling out the pressures

The larger Prince Phillip lock deals with bigger ships and has what are called ‘mitre’ gates, designed to be held shut by water head pressure. Before the lock gates open, it is important that the water level is equalised to within 150mm, otherwise the mechanical linkages are damaged by the hydraulic system’s attempt to open the gates against the very high pressure, as has happened in the past.

A system which would protect the gates, reduce maintenance and damage costs was needed. However, although the smaller Prince George lock has an ultrasonic level system manufactured by US company Vega, this wasn’t suitable. Installing the necessary protective cylinder, called a stilling tube, was going to be difficult, costly, need more maintenance, and be prone to damage as the large ships that pass through the lock do not leave any room to spare.

An answer was found in a non-contact radar unit. Designed for use in the water sector, the Vegapuls WL 61 is a loop powered device for easy connection and it doesn’t require any stilling tube arrangement. Further, the fact that the unit utilises pulsed microwaves rather ultrasonic sound waves helps because their accuracy is unaffected by environmental conditions such as wind, temperature, rain and sun. It has an IP68 housing for excellent environmental protection, 15m range and minimal blocking zone within millimetres of accuracy. The radar-type device is also the first in its class to meet the latest EN standard for use out in the open.

The unit was mounted on a standard bracket, and sited in a wall recess to accommodate the gates when in the open position which serves to protect the radar when ships are passing through. The narrow beam angle of the radar enables it to work even though it is mounted close to the side wall without creating false signals. It also maintains excellent accuracy monitoring the level over an 8m range to within a few millimetres, well within the 150mm differential range required to operate the lock gates safely.