There was a time when it was standard practice for diesel fuel to be stored in a bunded tank above ground and for gasoline (petroleum) to be stored in
a single skinned tank buried below ground. It still common practice in retail filling stations for all tanks to be buried. In the case of test facilities, if built within a secure perimeter, there is an increasing preference for fuel tanks and fuel piping to be installed above ground, where any leakage can be quickly detected. Local geology and proximity of groundwater sources or streams will play a part in determining the suitability of a fuel storage site.
The height below the datum ground level and any movement of the local water table1is of critical importance. In areas where the water table is high and variable, it is not unknown for buried tanks to “float” to the surface, with consequential fracturing of connections and fuel leakage.
The Approved Codes of Practice in the UK and in the USA require any underground fuel storage tanks (USTs) to be provided either with secondary containment or a leak detection system covering both tanks and associated pipework. Steel tanks also have to be fitted with a cathodic corrosion protection system.
The European regulations such as the ATEX Directive 94/9/EC and the EPA regulations in the USA, which in the 1980s required a major UST replacement program, encouraged many owners to convert to above-ground storage.
However, in many sites burial was required by local officials when the instal- lation was considered unsightly, exposed to high solar heat load, vulnerable to vehicular collision, vulnerable to vandalization or terrorist attack. These criteria are important, which is why a secure perimeter and careful layout is required when planning this part of a test facility.
If a full fuel storage license is required in the UK, the following information will usually be required (in the rest of the world attention to the same detail is recommended):
1. Site location map to a scale of 1:1250 or 1:2500 indicating all site bound- aries. Two copies of site layout to scale 1:100 clearly indicating the intended layout of fuel storage and distribution system.
2. The layout plan must show the following:
a. Location of storage tanks and tank capacities.
b. Route taken by road delivery vehicles (this must be a “drive-through”
not “cul-de-sac”).
c. Position of tanker fill points and their identification.
d. Location of pipework including all vent pipes, etc.
e. Location and type description of metering pumps, dispensers, etc.
f. All site drainage and its discharge location.
g. Petrol interceptor location and drainage discharge point.
1. The water table may be visualized as the surface of the subsurface materials that are saturated with groundwater in a given locality; it is not simply the depth to which groundwater settles in a hole. Note that some saturated ground materials are dangerously unstable. Local topography and geology will determine the details, which sometimes can vary over surprisingly small areas of ground.
Chapter | 8 Fuel and Oil Storage, Supply and Treatment 185
h. All other buildings within the site and their use.
i. All neighboring buildings within 6 m from the boundary.
j. Position of LPG storage, if applicable.
k. Location of car wash and drainage if applicable.
l. Main electrical intake point and distribution board.
m. Position of all fire-fighting appliances.
Very similar restrictions and requirements to those described above for the UK exist in most countries in the world, and any engineers taking responsibility for anything beyond the smallest and simplest test cell should make themselves familiar with all relevant regulations of this kind, both national and local.
Any contractor used to install or modify fuel systems should be selected on the basis of proven competence and, where applicable, relevant licensing to carry out such work and the required post-installation testing.
Both the legislative requirements and the way in which they are interpreted by local officials can vary widely, even in a single country. Where engine test installations are well established there should be a good understanding of the requirements, whereas in localities where such systems are novel, the fire and planning officers may have no experience of the industry and can react with concern; in these cases they may require tactful guidance.
Figure 8.1shows a typical arrangement for a fuel oil or gasoline bunded storage tank according to British Standard 799.
The risk of oil being lost during tank filling or from ancillary pipework is higher than tank rupture; the UK Control of Pollution (Oil Storage) Regulations 2001 recognize this fact and require that tanks have a list of ancillary equipment such as sight tubes, taps, and valves retained within a secondary containment system. The use of double-skinned tanks is strongly recommended and
Oil return line for unloading pumped ring main systems
Alternative oil submersion heater
Thermostat for
alternative heater Vent pipe
Filling line
Filling point Heater element withdrawal point Oil draw-off line Fire valve Filter Outlet
valve Oil immersion
heater Oil tight lining Tank supports Catchpit
Grating Semi-rotary pump
Tank lagging if required
Fire valve wire Manhole cover
with provision for dipstick
FIGURE 8.1 Typical above-ground bunded fuel tank with fittings.
increasingly required by regulation when used in underground installations [1].
Double-skinned tanks and fuel pipes should also be fitted with an interstitial leak monitoring device.
For the storage of fuel in drums or other containers, a secure petroleum store such as that shown inFigure 8.2is to be recommended. This design typically meets the requirements of the local UK authorities, but its location and the volume of fuel allowed to be stored may be subject to site-specific regulation.
The lower part forms a bunt, not more than 0.6 m deep, capable of containing the total volume of fuel authorized to be kept in the store. Ventilators at high and low level are to be covered by fine wire gauze mesh and protective grilles.
Proprietary designs should allow access to a wheeled drum lifter/trolley.
Packaged units built from 20-foot ISO shipping containers, designed for use at large road building sites, are probably a cost-effective solution for some facilities.
Finally, when planning bulk fuel storage, precautions should be taken against the theft of fuel and malicious damage (vandalism); where the risk is considered to be high the increased cost of burial is clearly justified.