Robotic Tank Inspection

Project Description and Services Provided

The Chilled Water Store within the Terminal 5 (T5) Energy Centre is designed to increase the resilience of the chilled water system’s ability to provide cooling for the T5 buildings. It is understood the Chilled Water Store is 18m x 32.5m x 8m and there is access to the tank from four hatches situated on top. Two measure 1.68mx1.6m and two measure 1m x 1.8m. In addition, there are ten precast concrete columns within the tank measuring 600 x 800mm which extend from the base to the ceiling.

This tank is required to be inspected to ensure there are no obvious structural defects in the concrete, showing signs of aging or deterioration.

The scope of work to be carried out was as follows:

1. Complete a Amentum Risk Assessment and Method Statement for the deployment of kit.

2. Perform remote visual inspection with a UAV (Unmanned Aerial Vehicle).

3. Deliver inspection images of Chilled Water Store surfaces for Amentum (as Jacobs) P&PS to produce the Heathrow Inspection Report.

Challenges

It was initially proposed that this tank be inspected by deploying people into the environment on a personnel riding basket. However, this approach is hazardous as the tank is a confined space and there is a steam relief valve within, which could cause serious burns. Therefore, a remote solution to this problem is preferable.

The equipment selected to perform this task was the Elios 3, a caged drone sporting a 4k front facing camera, a front facing thermal camera, and a LiDAR module on the back. The flight time is limited to approximately 9 minutes; however, this can be supplemented using additional battery packs. By performing a return to home and battery replacement exercise, the effective flight time can be extended over multiple concurrent flights.

Due to the craft being untethered, signal between the UAV and controller was unreliable. A signal booster was deployed along side the UAV to guarantee constant connection and ensure safety was maintained throughout the mission. During flight, delicate manoeuvring around furniture within the tank was necessary as there were many pipes and support structures as well as the original man access ladders.

The use of a UAV on the airside of Heathrow raises implications due to the restrictions in place for airborne vehicles on-site. This was worked around by constructing a gazebo over the tanks access points, removing the possibility for the UAV to fly into the restricted air space.

Solutions and Outcome

Performing the inspection revealed a series of cracks within the concrete. The work completed offers the client a solution that will mitigate the need to send personnel into potentially hazardous areas within a confined space. The UAV can capture more imagery at all heights within the tank and in this case, was able to capture cracks within the concrete that would have otherwise been missed should the inspection be carried out at ground level. Deploying the UAV was also the most cost-effective solution for the client.

Following the inspection, the client was provided with imagery from the flight allowing them to analyse the results and compile a report which will aid with future repair work and potential maintenance to ensure the continued safe operation of their cooling system.