Project Management

Operated by the Environment Agency, the Thames Barrier is London’s main defence against flooding. It has been in operation since 1982 and protects parts of the city against abnormally high tides and storm surges. Each of the four main gates weighs more than 3,300 tons, presents a 20 metre high barrier when in defence position and can hold back loads of up to 9,000 tons.

During its 30-year history the barrier has been closed more than 400 times. About 80 of these closures were deployed as protection against tidal surges and about 40 against rainfall, storm or fluvial surges.

Early in 2010 Monitran was asked to design, install and commission a system to monitor bearing movement and gate position. Critically, the system had to be a permanent fixture and would require some equipment to be placed on the outer faces of the bearings where it would be subjected on occasion to the full force of a tidal river.

The sensing requirements for each gate were as follows:

• 4 x eddy current probes to monitor bearing clearance around the 1 metre circumference as they rotate through 180º
• 1 x pressure sensor to derive water depth or tide height
• 1 x inclinometer to monitor gate position or angle
• 1 x accelerometer to monitor vibration levels
• 1 x water leak detector to confirm the continuing integrity of the waterproof junction boxes (on certain gates only)

All signals and power lines to and from the sensing equipment converge at a single cabinet on one of the barrier’s decks. The cabinet has displays which show:

• Bearing displacements relayed by the 48 eddy current probes
• Outputs of the 12 pressure sensors
• Gate positions at 0°, 90° or 180°
• Status of each of the 8 water leak detectors

The cabinet also houses connectors for accelerometer outputs for vibration monitoring or analysis.

This project warranted far more than just the provision of standard products. Several elements of the project required custom-built equipment and, additionally, Monitran needed to assemble a team of skilled engineers trained and certified to work in confined spaces and on floating platforms – a far cry from the cosy atmosphere of Monitran’s development laboratory and test room!

Monitran has undertaken a wide variety of smaller projects over the years but the Thames Barrier project is considered to be its most prestigious, and at times challenging, to date.

Read Industrial Plant and Equipment "Time and Tide", Sept 2011

The modern fully amphibious hovercraft is unique in its ability to travel over both water and flat land with equal facility and without any interruption during transition between the two.

Originally designed for rapid passenger transport over short distances, the modern hovercraft has proved its usefulness in a wide diversity of applications. These include coastguard and military theatres where a high-speed means of transport is required that is also capable of adapting to coastal, estuary and shallow waters as well as to beaches and islands. They are currently deployed in operations to counter smuggling, human trafficking and illegal immigration, and are also used to provide rapid search and rescue capability in emergency situations.

Monitran was approached as an established UK manufacturer with a view to providing an integrated engine and gearbox vibration monitoring system. The brief was to provide real-time condition monitoring direct to the pilot on a fleet of 12 vessels designed for coastguard use.

Each craft had 2 engines providing both lift and propulsion, plus drive trains linking these engines to the lift fans and propellers. In all, 14 sensors were required on each craft and an indication of abnormal vibration on any one of these sensors had to be available immediately to the pilot. Additionally, it was imperative to ensure that short periods of high vibration encountered during extreme manoeuvres could be discriminated from both normal running vibration levels and possible imminent failure. While the pilot required a simple indication, much like an oil pressure warning light on a car, maintenance engineers would require information on exactly what vibration levels any of the sensors was experiencing. The Monitran system would need to satisfy both these requirements.
In addition, all equipment had to be provided in a format compliant with marine regulations, and had to be as compact and lightweight as possible as well as resistant to the high levels of shock and vibration encountered during day-to-day operations.

The sensing part of the project was readily satisfied using Monitran 1100W accelerometers in submersible format fitted with marine-approved cable. These would provide many years service in wet and salty environments. Raw signals from these sensors were conditioned by 8066 ‘g-Mac’ units allowing velocity or peak g to be monitored on-line for either overall vibration or bearing wear detection. These raw signals could also be sampled off-line by the user’s vibration analyser for a full condition monitoring examination whenever real-time values indicated the need.

The project required:

• The development of a multichannel microcomputer controller to monitor sensor output and to discriminate between normal and abnormal vibration
• A real-time pilot warning
• A display, set-up and diagnostic capability for the hovercraft operator’s maintenance engineers to fit into the limited space available
• Protection of the internal electronics from water, shock and crew damage

In summary, Monitran’s development team was able to combine microcontroller technology with well-established and field-tested sensors to provide a tailored solution to meet this challenging brief.

Construction activities such as hammering, drilling and piling can cause transient levels of shock and vibration to neighbouring property. These transient vibrations must be monitored and minimised in accordance with British Standards for safe levels of ground vibration during construction operation to ensure that no long-term structural damage is caused.

Monitran was asked to develop a system for continuously monitoring the vibrations caused during the construction of an extension to a girls’ school in London. The construction work, close to a row of old houses and their boundary walls, required some very deep piling.

This type of measurement, though within the scope of Monitran’s sensors, was different from most standard applications in that it required the acquisition of transient vibration data at low frequency and with unpredictable timing. The sensors needed to be robust enough for installation on a construction site, yet the signal acquisition capabilities had to be sensitive enough to capture low-frequency and unpredictable vibration episodes and raise an alarm if levels approached maximum safely limits.

The specific requirements on this site were:

• To log the vibrations (in 3 axes) at 7 locations during site working hours and in all weather conditions
• To activate a visual alarm when vibrations exceeded safe levels (audible alarms were unsuitable due to high levels of ambient site noise)
• To log vibration events to provide access to data in case of complaints from residents

Monitran was required to install, assemble and commission all elements of the system on site.

Standard MTN1100 accelerometers were used for vibration detection, mounted tri-axially on blocks, which were then bolted to the building walls considered to be at risk.

Signal acquisition was achieved via a custom-built microcontroller capable of scanning the outputs of all sensors to capture the transient vibrations. The microcontroller incorporated an industrial touch screen for command input and output display, while continuously logging out-of-range vibrations with time and magnitude data. In real time any sustained high-level vibrations would trigger xenon alarm beacons to warn the site operator to suspend or modify operations until safe vibration levels were restored.

In summary, Monitran’s development team was able to combine state-of-the-art microcontroller technology with well-established field-tested sensors to provide a tailored solution to a challenging brief.