Class 1 Leak Detection - The ultimate protectionAudio version
Publication: PetrolPlaza Technology Corner
Issued: August 2012
Author: Thompson Jamie
I spent much of my life as a regulator controlling service stations and trying to prevent leaks, spills and accidents at filling stations.
Overpressure leak detection systems - image source SGB GmbH
Multitank installation monitored with a central class 1 overpressure system - image source SGB GmbH
Underpressure leak detection system - image source SGB GmbH
Vacuum Monitoring of Above Ground Storage Tanks - image source SGB GmbH
Class 2 liquid based leak detection system
Class 3 leak detection system with liquid sensors
Example of a leaking tank
Example of a leaking tank
Explosion caused by a leaking pressure system which killed the manager and injured several customers. The incident occurred in 1987 in the Netherlands.
A big part of this work in the past was trying to determine when single wall tanks would leak.
Although I have looked at many systems which were tried and tested no one system was able to inform us when a tank wall was breached - before product entered the ground.
I have had far too much experience of failures of systems and the consequences of leaking installations to have great faith in some forms of so called leak detection
While the loss of product from a tank or pipes from service stations has always been of concern that concern today is higher than ever before.
We should remember
- The risk of fire and explosion is still with us from any leak
- The consequences of a leak to the environment is considered by all those involved as of much higher concern now, with the subsequent claim against pollution damages caused by leaking product that can be catastrophic to a business and also negatively impact the reputation as well as harmful to the environment
- The very high cost of fuel also means the monetary loss should be of concern to businesses, as a 10,000 litre loss =13,500 Euros
The biggest change in the UK came in 1990 when we decided that no more single wall tanks would be installed and double wall tanks with leak detection would only be permitted.
The UK were behind other European countries such as Germany who had already made such a decision many years before to have all underground tanks double wall with leak detection. It was somewhat ironic that after the reunification of Germany, one half of the country had double wall tanks, the other did not.
While each country made decisions on the regulations for underground tanks, in Europe the EU had formulated a number of Directives (Laws) which has to be made mandatory by each EU country. These Directives covered mainly environmental issues such as prevention of pollution, protection of groundwater and drinking water, and the disposal of waste water. One Directive also covers the storage and use of dangerous substances.
These actions by the EU now mean that all member countries have been encouraged by Directives to comply with these laws. The industry has moved forward quickly and embraced the European standards for double wall tanks, and double wall pipes and of course leak detection. These standards are all designed to support the various Directives.
This standard EN 13160 -1 to 7 provided industry with several options [SEE DIRECTIVES]
- For those who chose the modern safe route of installing double wall tanks and pipes, then they should install Class 1 system which in fact is leak prevention (see images 1 to 4)
- Class 2 and 3 are also defined to only be used on double wall systems (see images 5 and 6)
- For those who already have single wall installations with no interstitial space then the options would be to install leak detection and classes 4, 5 & 6 are the options
- EN13160-7 even covers the lining of existing single wall tanks so that a class 1 leak detection can be fitted to old installations
What do the classes mean?
They are designed to guide the designer or owner of the service station as to the effectiveness of the system they are installing. Class 1 being the highest and class 6 being the lowest level.
Pressure or vacuum (see images 1 to 4)
The pressure system operates by putting a positive pressure in the interstitial space between the two walls of the double wall tank. This pressure will be above any external pressures from groundwater or the fuel itself. Any breach of the two walls will be detected as a loss of pressure indicating a leak and an alarm sounded enabling the owner to remove product from the tank before there is a threat to the environment.
The vacuum system operates in a similar way but draws a vacuum in the interstitial space. Any breach of the skins allows air, water or fuel to enter the interstitial space, this rise of pressure indicates a leak and an alarm will sound.