GB2206147A

GB2206147A - Shell bund for above ground liquid storage tanks

Info

Publication number: GB2206147A
Application number: GB08808492A
Authority: GB
Inventors: Ian Mcleod Traill
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-06-23
Filing date: 1988-04-11
Publication date: 1988-12-29
Anticipated expiration: 2008-04-11
Also published as: GB8808492D0; GB2206147B; GB8714713D0

Abstract

A shell bund has a watertight bund 3 with an abutted storage tank 1 which by its position above the bund 3 restricts the ingress of rainwater. The bund 3 has a dipped outlet 6 which prevents floating liquids, such as oil, from discharging outside the bund 3. The storage tank 1 can be reinforced on its vertical outer walls to reduce the chances of fracture. The storage tank 1 can have an outlet in the base of the tank 1 to encourage leaks to enter the bund 3. The tank 1 or bund 3 may have legs 4 or 5 Fig. 1 to assist inspection or maintenance. <IMAGE>

Description

SHELL BUND FOR ABOVE GROUND LIQUID STORAGE TANKS THIS INVENTION RELATES TO THE PROTECTION OF OIL CROUND LIQUID STORAGE TWItS WHICH IS ESPECIALLY BUT NOT EXCLUSIVELY TO PROTECT TANKS FROM 50 GALLONS ( 0.23 i3 ) TO 5000 GALLONS ( 22.73 m ) CAPACITY.

THE INVENTION HAS ITS ROOTS IN THE PETROLEUM INDUSTRY, PARTICULARLY THE PETROLEUM (CONSOLIDATION) ACT OF 1928. IN THIS ACT THERE IS REFERENCE TO FIRE WALLS TO CONTAIN SPILLAGES FROM ABOVE GROUND PETROLEUM SPIRIT TANKS AND THUSPPREVENT THE POTENTIAL SPREAD OF FIRE.

HOWEVER, WHEN ACCIDENTS OCCUR CAUSING LIQUID SPILLAGE, THE LIQUID MAY ESCAPE INTO THE GROUND To CAUSE WATER POLLUTION. SUBSWQUENTLY THE FLOORS ARE SOMETIMES SEALED, THAT IS TO SAY ME WATERTIGHT. ALTERNATIVELY THE FLOORS MAY BE CONSTRUCTED WITH UNDERDRAINS TO CONVEY THE SPILLAGES AWAY TO AN INTERCEPTOR TANK.

THE USE OF UNDERDRAINS TO CONVEY THE SPILLAGES AWAY IS NOT VERY SAFE SINCE LIQUID CAN ESCAPE BELOW THE DRAINS TO POLLUTE GROUNDWATER.

IN ADDITION THE INTERCEPTOR TANK AT THE END OF THE UNDERDRAINS CAN BE FLOODED BY A HEAVY FLOW OF LIQUID CAUSING THE LIQUID TO OVERSPILL THE INTERCEPTOR OUTLET AND POLLUTE SURFACE WATERS SUCH AS STREAMS OR RIVERS.

s WATERTIGHT FLOOR WITH FIRE WALLS IS SOMETIMES KNOWN AS A BUND.

HOWEVER, WATERTIGHT WINDS IN THE OPEN AIR COLLECT RAINWATER AND THUS THE BUND CAN BECOME INEFFECTIVE OWING TO LOSS OF STORAGE CAPACITY DUE TO THE PRESENCE OF RAINWATER. THE OWNER IS AT A DISADVANTAGE IN HAVING TO CHECK AND MAINTAIN SUCH BUNDS.

IN PRACTICE MANY WATERTIGHT BONDS ARE FITTED WITH DRAIN VALVES OR ELSE THE WALL IS PERMANENTLY BREACHED. FOR EXAMPLE A BRICK MAY BE REMOVED FROM A BRICK BUND WALL TO ALLOW THE RAINWATER TO ESCAPE.

UNFORTUNATELY IN THIS CIRCUMSTANCE THE BUND IS NOW NO LONGER WATERTIGHT AND THEREFORE DOES NOT DO ITS JOB OF CONTAINING LIQUID SPILLAGES. A BUND WALL FITTED A DRAIN VALVE CAN BE INEFFECTIVE SINCE THE DRAIN VALVE IS OFTEN LEFT OPEN TO OBVIATE THE NEED FOR DRAINING OFF RAINWATER FROM TIME TO TIME. IN ADDITION UNAUTHORISED PERSONS MAY TURN THE VALVE ON TO DRAIN THE BUND WITHOUT THE OWNER'S KNOWLEDGE. POLLUTION CAN OCCUR DURING DRAINING SINCE RAINWATER INSIDE A BUND CAN BE CONTAMINATED WITH LIQUID PROM THE STORAGE TANK.

UNAUTHORISED PERSONS CAN EASILY GAIN ACCESS TO BUNDED INSTALLATION AND INTERFERE WITH THE STORAGE TANK AND CAUSE POLLUTION.

IN ANOTHER TYPE OF BUND THERE IS NO DRAIN VALVE. A WATERTIGHT SUMS IN THE FLOOR COLLECTS RAINWATER BUT THE OWNER HAS THE EXPENSE OF PROVIDING PUMP IN ORDER TO EMPTY THE BUND OF RAINWATER FROM TIME TO TIME. AGAIN POLLUTION CAN OCCUR IF RAINWATER IN THE BUND IS CONTAMINATED.

IF A TANK IS FILLED FROM A ROAD TANKER OR RAIL TANKER THEN THE TANK MAY BE OVERFILLED BY ACCIDENT AND LIQUID MAY ESCAPE UNDER PRESSURE FROM THE VENT PIPE AS A JET OR SPRAY AND MAY ALSO BE DEFLECTED FROM A WALL OF THE TANK. LIQUID MAY ESCAPE UNDER THE HYDROSTATIC PRESSURE OF THE TANK CONTENTS SUCH AS WHEN A VALVE IS REMOVED BY MISTAKE.

CONSEQUENTLY LIQUID CAN ESCAPE OVER THE BUND WALLS AND IS THEREFORE NOT CAPTURED INSIDE THE BUND. IN TURN THIS CAN LEAD TO POLLUTION OR DAMAGE TO OTHER PROPERTY. IT MAY ALSO BE UNSAFE.

EVEN A LIQUID STORAGE TANK LOCATED INSIDE A BUILDING MAY NOT BE TROUBLE-FREE SIN AN ACCIDENT CAN CAUSE WATER POLLUTION OUTSIDE THE BUILDING AS THE LIQUID ESCAPES.

IT HAS BEEN SUGGESTED THAT DIESEL FUEL ESCAPING INTO THE GROUND THROUGH POROUS FLOORS (WITHIN A FIRE WALL) CAN BE SAFELY DEALT WITH BY RECOVERING POLLUTED GROUNDWATER THROUGH BOREHOLES IN STRATEGIC LOCATIONS. THE GROUNDWATER IS THEN TREATED BY A SETTLING TANK AND ACTIVATED CARBON. HOWEVER THE METHOD MAY BE EXPENSIVE IN TERMS OF THE DRILLING OF A BOREHCLE AND THE PROVISION OF A PUMP AND TREATMENT PLAT. UNFORTUNTELY THE METHOD ONLY OPERATES AFTER CONTAMINATION OF GROUNDWATER HAS OCCURRED AND THIS WATER MAY BE AN IMPORTANT DRINKING WAS SUPPLY.

AN ADDITIONAL PROBLEM WITH EXISTING WAYS IS THAT SMELL NUISANGE MAY ARISE DUE TO FUMES FROM LIQUID LYING IN THE BUND.

THE CONCEPT OF PREVENTING WATER POLLUTION STEMS FROM VARIOUS ACTS OF PARLLAMENT SUCH AS THE CONTROL OF POLLUTION ACT 1974. THIS ACT REFERS TO THE CUSTODY OR CONTROL OF ANY POISONOUS, NOXIOUS OR POLLUTING MATTER. AS A RESULT OF ACTS LIKE THIS, VARIOUS AUTHORITIES HAVE TRIED TO IDENTIFY THE AREAS WHERE PROHLEMS MAY OCCUR. THE SEVERN TRENT WATER AUTHORITY DESIGNATE ZONES OF PROTECTION TO REDUCE THE RISK FROM LIQUID STORAGE TANKS, UNLESS ADEQUATE PROTECTIVE MEASURES ARE AGREED. THE REASON UNDERLYING THE PRESENT INVENTION IS THE CONCEPT OF TOTAL CONTAINMENT IN THE EVENT OF SPILLAGE OF A LIQUID. EXISTING BUND DESIGNS AND FIRE WALLS DO NOT GIVE THIS TYPE OF PROTECTION.

THE PRESENT INVENTION IS INTENDED TO PROTECT ABOVE GROUND LIQUID STORAGE TANKS AND IN WHICH THE ABOVE MENTIONED DIFFICULTIES ARE AVOIDED OR REDUCED.

ACCORDING TO THE PRESENT INTENTION THE IS PROVIDED A SHELL BUND COMPRISING A WATERTIGHT BUND WITH THE STORAGE TANK SITTING ON TOP.

THIS ARRANGEMENT REDUCES INGRESS OF RAINWATER WHICH WOULD OTHERWISE ENTER THE BUND. THE BUND MAY BE LIKE A DEEP TRAY AND MAY BE DEEP ENOUGH TO CONTAIN THE TANK CONTENTS OR GREATER THAN THIS VOLUME. THE STORAGE TANK MAY HAVE LEGS WHICH READILY OCCUPY A POSITION ON A FLANGE OF THE BUND OR SIMILAR MEANS. IN THIS WAY IT IS POSSIELS TO SEE INTO THE BUND FOR MAINTENANCE AND INSPECTION PURPOSES. THE BUND MAY HAVE LEGS TO ALLOW IT TO BE READILY LIFTED BY FORK LIFT TRUCK OR SIMILAR MEANS.

THE LEGS MAY ALSO PERMIT EASY INSPECTION OF THE UNDERSIDE OF THE BUND IN THE EVENT TILT A LEAK OCCURS.

THE STORAGE TANK OUTLET MAY BE FIXED TO THE UNDERSIDE OF THE TANK.

IN THIS WAY IF THE OUTLET VALVE OR CONNECTION FAILS THEN THE TANK CONTENTS MAY DISCHARGE INTO THE BUND. ALTERNATIVELY THE STORAGE TANK OUTLET MAY BE OFFSET FROM THE TANK IN SUCH A WAY THAT IF ITS VALVE FALLS, OR OTHER PITTING FAILS WHICH KEEPS THE OUTLET NORMALLY CLOSED, THEN IT WILL DISCHARGE INTO THK BUND.IF THE TANK HAS A DRAIN VALVE THEN IT MAY BE FITTED IN SUCH A WAY TEAT IT DRAINS INTO THE BUND WHEN REQUIRED,

IN ANOTHER EMBODIMENT THE BLIND MAY BE FITTED WITH A DIPPED OUTLET DISCHARGING AT A HIGH LEVEL IN TIIP BLIND WALL. IN THIS WAY LIQUIDS WITH A LOWER SPECIFIC GRAVITY THAN WATER, AND ESSENTIALLY IMMISCIELE WITH WATER, MAY BE RETAINED WHILST ALLOWING WATER TO DISCHARGE THROUGH THE DIPPED OUTLET WHICH SHOULD END WITHIN 250mm OF THE BUND FLOOR AND PREFERAiLY WITHIN X50 mm OF THE FLOOR.THE DIPPED OUTLET SHOULD NOT TOUCH THE BUND FLOOR SINCE THIS COULD RESULT IN HLOCKAGE.

IN ANOTHER EMBODIMENT THE STORAGE TANK MAY BE REINFORCED BY ELASTIC PANELS OR FOAM PANELS OR SIMILAR MEANS, GLUED OR WELDED TO THE OUTER VERTICAL WALLS OF THE TANK. IN ANOTHER EMBODIMENT THE TANK OR BLIND OR BOTH MAY BE DOUBLE SKINNED. IN THIS WAY THE TANK MAY BE LESS SUSCEPTIELE TO DAMAGE OR VANDALISM WHICH IN TURN PREVENTS OIL LEAKS WHICH WOULD OTHERWISE ESCAPE OVER THE BUND WALLS DUE TO HYDROSTATIC PRESSURE OF TANK CONTENTS.

IN ANOTHER EMBODIMENT THE ROOF OF THE STORAGE T & K MAY BE RIBBED TO ENCOURAGE FLOW OF RAINWATER IN THE DIRECTION OF RIBBING. THIS WILL INCREASE THE VELOCITY OF FLOW AND THE RAINWATER MAY ESCAPE OVER THE BUND WALL RATHER THAN FILLING THE BUND.

A SPECIFIC EMBODIMENT OF THE INVENTION WILL NOW BE DESCRIBED BY WAY OF EXAMPLE WITH REFERENCE TO THE ACCOMPANYING DRAWINGS IN WHICH: FIGURE I SHOWS IN PERSPECTIVE THE SHELL BUND WITH STORAGE GE TANK IN POSITION ON TOP OF THE BUND.

FIGURE 1 SHOWS THE BUND 3 WITH LEGS 4 AND LIQUID STORAGE TANK I WITH ITS LEGS 5 AND FILL POINT 2. THE LEGS 5 ABUT TO THE BUND 3 BY s FLANGE OR ANY WELL KNOWN MEANS. THE LECS 5 ABUT TO THE INSIDE OF THE BUND 3. THE BUND 3 MAY BE SUPPORTED BY A BR & E FRAME (NOT SHOWN) WHICH IS SECURED TO THE BUND 3 BY ANY WELL KNOWN WAY. THE BUND 3 HAS A DIPPED OUTLET 6.

THE TANK I AND THE BUND 3 CAN BE MADE ESPECIALLY BUT NOT EXCLUSIVELY OF PLASTIC SUCH AS POLYETHYLENE, OR PLASTIC WHICH WILL WITHSTAND THE CORROSIVENESS OF THE STORED LIQUID. THE LEGS 5 AND 4 MAT ALSO BE MADE ESPECIALLY BUT NOT EXCLUSIVELY OF PLASTIC. THE TANK I AND BUND 3 MAY BE MADE FROM THE SAME MOULD OR PATTERN SUCH THAT THEY SLOT INTO EACH OTHER IN THE MANNER OF PALLET CONTAINERS. IN THIS CIRCUMSTANCE THE STORAGE TANK I WILL HAVE TO BE FITTED WITH A SEALED LID TO MAKE THE TANK I WATERTIGHT. THE TANK I MAY BE FITTED WITH A FILL POINT 2 OR DEPTH GAUGE (NOT SHOWN) OR DRAIN VALVE (NOT SHOWN) OR DELIVERY VALVE (NOT SHOWN) OR ALL THESE THINGS. THE TANK I MAY DELIVER ITS CONTENTS BY GRAVITY OR By PUMP (NOT SHOWN).ANY OR ALL THESE THINGS MAY BE ATTACHED TO Till SHELL BUND.

FIGURE 2 SHOWS THE BUND 3 WITH DIPPED OUTLET 6. THE DIPPED OUTLET 6 DISCHARGES CLEAN WATER FROM NEAR THE BASE OF THE BLIND 3. IN THE EVENT THAT OIL IS STORED IN THE TANK I, SOME LEAKING OIL MAY ENTER BUND 3. EVEN IF THE BUND 3 IS FULL OF RAINWATER THE OIL WILL FLOAT ON THE SURFACE. CONSEQUENTLY THE OIL WILL NOT READILY DISCHARGE VIA THE DIPPED OUTLET 6. THIS IS A WELL KNOWN PRINCIPLE USED IN THE DESIGN OF OIL INTERCEPTORS AND IN LIKE MANNER THE BUND 3 ALSO ACTS AS AN INTERCEPTOR.

ANOTHER SPECIFIC EMBODIMENT OF THE INVENTION WILL NOW BE DESCRIBED BY WAY OF EXAMPLE WITH REFERENCE TO THE ACCOMPANYING DRAWINGS IN WHICH: FIGURE 3 SHOWS IN PERSPECTIVE THE SHELL BUND WITH THE STORAGE TANK IN POSITION ON TOP OF THE BUND.

FIGURE 3 SHOWS THE BUND 3 WITH EXTERNAL BRACE FRAME 4 AND LIQUID STORAGE TANK I SITTING ON THE BRACE FRAME 4 WITHIN THE BUND 3.THE TANK I MAY RAVE A FILL POINT (NOT SHOWN), DRAIN VALVE AND OUTLET (NOT SHOWN). THE TANK I MAY BE SECURED TO THE BUND 3 BY ANY WELL KNOWN WAY. THE TANK I HAS ITS BASE AND DRAIN VALVE (NOT SHOWN) AND OUTLET (NOT SHOWN) PROTECTED WITHIN THE BUND WALLS 3 WHICH MAY EXTEND ABOVE THE BASE OF THE TANK I BY AT LEAST 15 = OR MORE. HOWEVER THE TANK I DOES NOT TOUCH THE TOP WATER BEVEL WITHIN THE BUND 3. THE BRACE FRAME 4 EXTENDS BELOW THE BUND 3 IN ORDER TO RAISE THE BUND OFF THE GROUND. THE DIPPED OUTLET 6 IS SHOWN.

FIGURE 2 SHOWS THE BUND 3 WITH DIPPED OUTLET 6.

THE TANK I AND BUND 3 CAN BE MADE ESPECIALLY BUT NOT EXCLUSIVELY OF MILD STEEL SHEET OR PLATE, SUITABLY COATS WITH PRIMER OR PAINT OR EVEN FLAME SPRAYED OR ANY WELL KNOWN FINISH OR COMBINATION OF FINISHES. THE EMBODIMENT JUST DESCRIBED IS MOST SUITABLE FOR METAL STORAGE TANKS SINCE THESE ARE VULNERABLE TO CORROSION AND CONSEQUENLY MAY LEAK PARTICULARLY AT THE BASE OT THE TANK. BY PROTECTING THE BASE OF THE TANK I WITHIN THE BUND 3 THEN LEAKS DUE TO CORROSION AT THE BASE MAY ENTER THE BUND. SIMILARLY LEAKS PROM VALVES AT THE BASS OF THE TANK I MAY ENTER THE BUND 3.

FIGURE 4 SHOWS A CROSS SECTION OF THE BUND 3, TANK I, AND ERACE FRAME 4 WITH DIPPED OUTLET 6.

Claims

I A SHELL BUND FOR ABOVE GROUND LIQUID STORAGE TANKS COMPRISING A WATERTIGHT BUND WITH STORAGE TANK ABUTTED ON TOP, AND IN WHICH THE STORAGE TANK IS SO ARRANGED TO RESTRICT INGRESS OF RAINWATER INTO THE BUND.
2 A SHELL BUND AS CLAIMED IN CLAIM I WHEREIN THE STORAGE TANK RAS LEGS WHICH ABUT ONTO THE BUND AND THUS ALLOW FREE SPACE FOR INSPECTION AND MAINTENANCE TO THE BUND.
3 A SHELL BUND AS CLAIMED IN CLAIM I OR CLAIM 2, WHEREIN THE BLIND HAS LEGS TO ALLOW INSPECTION OF THE UNDERSIDE OF THE BUND OR TO ALLOW s FORKLIFT TRUCK TO LIFT IT.
4 A SHELL BUND AS CLAIMED IN ANY PRECEDING CLAIM, WHEREIN THE BUND HAS A DIPPEND OUTLET AT A HIGH LEVEL. TO ALLOW THE DISCHARGE OF CLEAN WATER WHILST RETAINING FLOATING LIQUIDS, SUCH AS OIL, IN THE BUND.
5 s SHELL BUND AS CLAIMED IN ANY PRECEDING CLAIM, WHEREIN THE WATERTIGHT BLIND HAS THE CAPACITY TO CONTAIN UP TO II0% OF THE TANK CONTENTS.
6 A SHELL BLIND AS CLAIMED IN ANY PRECEDING CLAIM, WHEREIN THE STORAGE TANK LEGS ARE ABUTTED TO AN INTERNAL FLANCE OF THE BUND.
7 A SHELL BUND AS CLAIMED IN ANY PRECEDING CLAIM, WHEREIN THE STORAGE TANK IS REINFORCED WITH PANELS ATTACHED TO THE OUTER VERTICAL WALLS OF THE TANK TO REDUCE THE POSSIBILITY OF FRACTURE OF THE VERTICAL WALLS.
8 A SHELL BUND AS CLAIMED IN ANY PRECEDING CLAIM, WHEREIN THE OUTLET OR DRAIN VALVE OR BOTH ARE FIXED TO THE UNDERSIDE OF THE STORAGE TANK OR ARE OFFSET IN SUCH A WAY THAT OUTLET OR DRAIN VALVE FAILURE WILL CAUSE THE STORED LIQUID TO DISCHARGE INTO THE BUND.
9 A SHELL BUND AS CLAIMED IN ANY PRECEDING CLAIM, WHEREIN THE ROOF OF THE TANK HAS RIBS TO ENCOURAGE RAINWATER TO FLOW OFF IN THE DIRECTION OF THE RIBS SUCH THAT THE VOLUME AND SPEED OF FLOW WILL INCREASE AND ESCAPE OVER THE BUND RATHER THAN INTO IT.
IO A SHELL BUND AS CLAIMED IN ANY PRECEDING CLAIM, WHEREIN THE STORAGE TANK IS SUPPORTED ON A BRACE FRAME.
II A SHELL BUND AS CLAIMED IN ANY PRECEDING CLAIM, WHEREIN THE STORAGE TANK IS SUPPORTED ON AN EXTERNAL BRACE FRAME WHICH PASSES UNDER THE BLIND THUS OBVIATING THE REQUIREMENT FOR LEGS ON THE BUND.
12 A SHELL BUND AS CLAIMED IN ANY PRECEDING CLAIM, WHEREIN THE STORAGE TANK SUPPORTED IN SUCH A WAT THAT THE BASE OF THE TANK OR THE OUTLETS OR VALVES AROUND THE BbSB OF THE TANK ARE PROTECTED WITHIN THE BUND WALLS TO A DEPTH OF AT LEAST 15 ii.

I3 A SHELL BUND AS CLAIMED IN ANY PRECEDING CLAIM, WHEREIN THE BVND HAS A DIPPED OUTLET AT A HIGH LEVEL TO ALLOW THE DISCHARGE OF CLEAN WATER WHILST RETAINING FLOATING LIQUIDS, SUCH AS OIL, IN THE BUND. THE DIPPED OUTLET SHOULD END WITHIN 250mm OF THE BUND FLOOR AND PREFERABLY WITHIN 150 mm OF THE FLOOR BUT THE END SHOULD NOT TOUCH THE FLOOR.

Amendments to the claims have been filed as follows 8 A SHELL BUND AS CLAIMED IN ANY PRECEDING CLAIM, WHEREIN THE OtrILET OR DRAIN VALVE OR BOTH ARE FIXED TO THE UNDERSIDE OF THE STORAGE TANK OR ARE OFFSET IN SUCH A WAY OUTLET OR DRAIN VALVE FAILURE WILL CAUSE THE STORED LIQUID TO DISCHARGE INTO THE BUND.

9 A SHELL BUND AS CLAIMED IN ANY PRECEDING CLAIM, WHEREIN THE ROOF OF THE TANK HAS RIBS TO ENCOURAGE RAINWATER TO PLOW OFF IN THE DIRECTION OF THE RIBS SUCH THAT THE VOLUME AND SPEED OF PLOW WILL INCREASE AND ESCAPE OVER THE BUND RATHER THAN INTO IT.

IO A SHELL BLIND AS CLAIMED IN ANY PRECEDING CLAIM, WHEREIN THE STORAGE TANK IS SUPPORTED ON A BRACE FRAME. FOR ELASTIC EMBODIMENTS THIS MAY TAKE THE FORM OF A PERFORATED PALLET WHICH LIES ON THE FLANGE OF THE BUND. THE PERFORATIONS PERMIT EXAMINATION OF THE BUND CONTENTS AND MAINTENANCE.

II A SHELL BUND AS CLAIMED IN ANY PRECEDING CLAIM, WHEREIN THE STORAGE TANK IS SUPPORTED ON AN EXTERNAL BRACE FRAME WHICH PASSES UNDER THE BUND THUS OBVIATING THE REQUIREMENT FOR LEGS ON THE BUND.

I2 A SHELL BUND AS CLAIMED IN ANY PRECEDING CLAIM, WHEREIN THE STORAGE TANK IS SUPPORTED IN SUCH A WAY THAT THE BASE OF THE TANK OR THE OUTLETS OR VALVES AROUND THE BASE OF THE TANK ARE PROTECTED WITHIN THE BUND WALLS TO A DEPTH OF AT LEAST 15 mm.
13 A SHELL BUND AS CLAIMED IN ANY PRECEDING CLAIM, WHEREIN THE BUND HAS A DIPPED OUTLET AT A HIGH LEVEL TO ALLOW THE DISCHARGE OF CLEAN WATER WHILST RETAINING FLOATING LIQUIDS, SUCH AS OIL, IN THE BUND. THE DIPPED OUTLET SHOULD END WITHIN 250mm OF THE BLIND FLOOR AND PREFERABLY WITHIN I50 mm OF THE FLOOR BUT THE END SHOULD NOT TOUCH THE FLOOR.
I4 A SHELL BUND AS CLAIMED IN ANY PRECEDING CLAIM, WHEREIN THE TANK OUTLET OR OUTLET PUMP IS FITTED WITH A SPRING LOADED VALVE, OR LOCK OR OTHER WELL KNOWN WAY TO PREVENT THE TANK CONTENTS DRAINING OFF BY GRAVITY IN THE EVENT OF AN ACCIDENT.
I5 A SHELL BUND AS CLAIMED IN ANY PRECEDING CLAIM, WHEREIN THE STORAGE TANK IS SUPPORTED ON A BRACE FRAME AND THERE IS ALLOWED SUFFICIENT FREE SPACE BETWEEN THE TANK AND BUND FOR INSPECTION AND MAINTENANCE TO THE BUND.
I6 A SHELL BUND AS CLAIMED IN ANY PRECEDING CLAIM, WHEREIN THE STORAGE TANK IS ABOVE THE LEVEL OF THE INVERT OF THE DIPPED OUTLET.
I7 A SHELL BUND AS CLAIMED IN ANY PRECEDING CLAIM, WHEREIN THE BRACE FRAME, WHICH PASSES UNDER THE STORAGE TANK, IS ABOVE THE LEVEL OF THE INVERT OF THE DIPPED OUTLET TO PREVENT CORROSION.
18 A SHELL BUND AS CLAIMED IN ANY PRECEDING CLAIM, WHEREIN THE STORAGE TANK IS ATTACHED TO THE BUND BY ANY WELL KNOWN WAY FOR
19 A SHELL BUND FOR ABOVE GROUND LIQUID STORAGE TANKS SUBSTANTIALLY AS DESCRIBED HEREIN WITH REFERNCE CE TO FIGURES I-4 OF THE ACCOMPANYING DRAWINGS.