Skilling Up: Rope access for HVAC installation
Rope access is proving its worth in the safe installation of ventilation systems in Thames Water's Lee Tunnel
by Rebecca Clissett, Operations Director, Air Technology Systems
Heating, Ventilation and Air Conditioning (HVAC) systems and ductwork are installed at height within a variety of different locations, traditionally via mobile or powered access. Sometimes these traditional methods aren’t always the safest or most cost effective. To provide a safe method of working and a competitive solution, ATS have developed their rope access division.
Our new rope access division allows the installation of HVAC systems via rope access. Highly skilled plumbers, pipe fitters, ductwork fitters, air conditioning engineers and electricians are trained in rope access techniques that conform to the international governing body IRATA. This allows access for installation within areas where scaffolding or other access methods are inappropriate, costly or unsafe. Rope access is recognized as the safest method of working at heights and ATS are currently the only company to use this method of installation for HVAC systems.
What is rope access?
IRATA International’s rope access system is a safe method of working at height where ropes and associated equipment are used to gain access to and from the workplace, and to be supported there.
The advantage of using rope access methods mainly lies in the safety and speed with which workers can get to or from difficult locations to carry out their work, often with minimal impact on other operations and the nearby area. Another major benefit is that the combination of the total man-hours is reduced and the level of risk for a particular task (man-at-risk hours) is often reduced when compared with other means of access and their associated risks and costs.
Where rope access is used
Although rope access has its origins in the offshore industry, it was quickly recognized that there were many onshore applications for work placement techniques that were safe, environmentally friendly and not intrusive. ATS have to date used this installation method in many different settings from commercial warehouses, to the side of office buildings, staircases, to sewage treatment works; as our Lee Tunnel case study shows. This specialist installation technique is unique to ATS, and in future we plan to increase the volume of systems we install and maintain via this method.
Use on the Lee Tunnel project
ATS are proud to be working with MVB and Thames Water on the Lee Tunnel Project, London: the largest, deepest vertical tunnel in Europe. ATS are providing both a specialist ventilation solution combined with innovative rope access installation methodology within the new Main Shaft Pumping Station at Beckton Sewage Treatment Works, London as part of the prestigious and groundbreaking Lee Tunnel Project.
The Lee Tunnel is the first of two tunnels being constructed for Thames Water, which will collectively capture sewage from various combined sewer overflows (CSOs), built by the Victorians as part of an ageing sewerage network that still serves London 150 years on.
The four-mile tunnel will run beneath the London Borough of Newham from Abbey Mills to Beckton and it will help prevent more than 16 million tonnes of sewage mixed with rainwater overflowing into the River Lee each year, by capturing it and transferring it to Beckton Sewage Treatment Works, which is being expanded to enable it to deal with the increased volumes of sewage and flood water.
A new main shaft pumping station is being constructed within a 38m diameter, 80m deep shaft at Beckton and linked to the main Lee Tunnel. The main area of the pumping station will be divided into two dry well compartments which shall house the pumps and motors to pump the storm water into Beckton STW for treatment.
In addition the pumping station has two designated access shafts to allow safe ingress and egress from the pumping station for maintenance.
ATS have worked in the water industry as specialist ventilation and odour control providers for 20 years and were approached by MVB to quote for the ventilation for this specialist project, and were successful.
The ventilation systems to serve the main shaft are designed to achieve a safe working environment for operatives due to the risk of hydrogen sulphide being present, but additionally to overcome the huge heat gain from the large pumps.
Air is supplied to both sides of the shaft via large plants located outside the shaft with large vertical ductwork being used to distribute air evenly throughout the drywells. We have further innovated by the use of our original ‘JETFLO’ nozzles which are key to achieving a high ventilation efficiency by thoroughly mixing the air, diluting any heat and contaminants such as hydrogen sulphide and creating the best possible working environment.
Air is extracted from low level from both sides of the shaft, another key ATS design feature being that hydrogen sulphide is heavier than air and so collecting air at low level is another way we have increased the ventilation efficiency. Pumps are also located at low level and so we are able to capture heat at source and exhaust to outside.
The Access Shafts had different design requirements with a need to provide both general ventilation to the stairways, but also to pressurise the entire access shafts for firefighting. The system has been fully designed in accordance with BS EN 12101-6:2005 to provide a Class B system for means of escape and firefighting.
The design process has been challenging with lots of aspects to consider including selection of materials.
The entire main shaft ductwork system is 316 stainless steel in order to achieve a 20 year design life and with some of the ducts being 2.2m diameter we have used specialist construction techniques. Due to the depth of the pumping station replacement of ductwork will be very difficult and so selection of the correct materials is important.
The entire access shaft ductwork systems are 316 stainless steel, but fire rated for 4 hours.
The biggest challenge on this project was how we would safely complete the installation. Conventional methods such as scaffolding and man riders were considered, but it was impossible to use this method because of the space available and the need to access flanges and the like behind the ductwork. Installation via rope access was risk assessed as the most practical solution as it allows access to areas where scaffolding would traditionally be required, but would be inappropriate, prohibitively expensive or unsafe.
Using rope access as a method of installation is innovative because it solves problems that traditional methods of access cannot. It was originally devised as a method of installation when ductwork was being fitted within a lift shaft and it became apparent that once scaffolding had been erected there would no longer be the space required to fit the actual ductwork itself. Scaffolding, the usual method of access, was simply impossible and would have caused programmed installation periods to dramatically increase, so it was clear that something more innovative was required.
At about the same time as this, an A/C system was being fitted on the 9th floor, in a light-well of a building that had multiple owners/landlords. The time taken to receive the necessary permissions to erect scaffold would have meant costly delays to the project.
Both of these challenges were overcome with a new innovative solution: the combination of IRATA rope access methods with the technical trade skills our operatives already had. Combining two existing skills is a major innovation in construction that has led to ATS being able to solve problems and provide solutions on both small and very large scales.
About the Author: Rebecca Clissett is Operations Director at Air Technology Systems (ATS), design and project management specialists with over twenty five years of experience in providing effective, energy saving systems for industrial heating, ventilation, air conditioning, odour control and bespoke climate management solutions
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