Vital information on VR2 systems and UST pressure risks
July 27, 2017
NSW laws stipulate that fuel retail sites located in an around Sydney that retail more than 3.5ML of petrol per year, are required to have installed Stage 2 Vapour Recovery (VR2) equipment by 1 January 2017.
In addition, new retail sites (or modified sites) located in the Greater Sydney Region (i.e. Sydney, Central Coast, Newcastle and Wollongong) that were commissioned after November 2009 are required to have installed VR2 equipment.
The NSW requirements for installation of VR2 equipment are summarised in figure 1 (as sourced from the NSW EPA website).
“One aspect of these Regulations has been a considerable source of discussion between ACAPMA and the NSW Government”, said ACAPMA CEO Mark Mckenzie.
“That aspect is the operation of the PV vent and the regulatory requirement for installation of a specific design that appears to impose a significant maintenance burden on fuel retailers when compared with appropriate alternative designs”, Mark continued.
The NSW Regulations stipulate the use of a single piston style PV valve.
Given early experiences with these valves seizing shut – resulting in unsafe pressures in Underground Storage Tanks (UST’s) – the NSW Government took it upon itself to specify that a 10mm hole should be drilled in the vent chamber to provide a failsafe.
“But there is a growing body of evidence suggesting that this procedure does not provide sufficient ventilation of underground storage tank systems, resulting in the creation of destructive tank vacuums and pressures”, said Mark.
The problem is compounded where the vent stanks for individual tanks are manifolded to a single vent stack.
Manifolded vents reduce the venting capacity, potentially creating over pressurisation and over vacuum events to occur and placing UST equipment under stress. This stress is then exacerbated with the use of the PV Vent valves stipulated in the NSW Regulation.
“Effectively, should the PV Vent valve seize shut, then the only venting of the underground tanks is by way of the 10mm orifice which causes the UST system to be operated well in excess of their design criteria”, said Mark.
The minimum standard venting capacity for category 4 underground storage tanks is 40mm per tank. If the system is manifolded, then the venting capacity should be increased to either 120mm (3 tanks), 160 (4 tanks) or 200mm (5 tanks) capacity.
“We are hearing numerous reports of PV vent failure and strongly suggest that fuel retailers make sure that there is sufficient venting of their UST systems, particularly where VR2 systems have been installed”, said Mark.
Where single piston style PV Valves have been installed, it is vital that these valves be inspected regularly (at least monthly), as a failed valve can contribute to catastrophic tank failure where there is insufficient venting.
“Alternatively, fuel retailers should consider use of multi-valve systems which provide good venting capacity in the event of one or more valves seizing shut”, said Mark.
ACAPMA is currently finalising a Best Practice Guideline for fuel retailers on VR2 systems that will be released at the 2017 Asia Pacific Fuel Industry Forum, to be held in Melbourne on 13 and 14 September 2017
In the meantime, it is suggested that all fuel retailers who have VR2 systems installed at their site contact their UST system provider to satisfy themselves that their system has sufficient venting capacity in the event of PV vent failure said Mark.
“Relying on the 10mm orifice to vent a single tank – let alone multiple tanks manifolded to a single stack – risks major damage to UST’s”, concluded Mark.