Occupational Hazards - Boil Over & Slop Over

Front 1

WHAT ARE BUNDS?

Back 1

Walls surrounding flammable liquid tanks designed to contain a spill should a leak occur. They are designed to hold 100% of the tank's contents or the contents of the largest tank in the bund and are constructed of concrete or earth similar to a dam wall.

Front 2

WHAT IS A RIM FIRE?

Back 2

Rim fires are the most common fire to occur in tha tank with a 'floating'roof. They are commonly caused by lightning strike. They runner seal around they edge of the roof catches fire.

Front 3

WHAT IS A
FULL SURFACE
FIRE?

Front 4

WHAT IS SLOP OVER?

Back 4

Slop over is where pockets of water from ill directed cooling lines or seawater trapped within the crude oil is instantly heated to boiling point and expands to steam.
The force of the expansion causes frothing of the top layers of the product which can then flow down the sides of the tank and into the bunded area.

Front 5

WHAT IS BOIL OVER?

Back 5

A layer of water is located at the bottom of the tank. When the thermal layer (travelling between 0.3m to 1m per hour) reaches the bottom of the tank, the water is instantly vaporized (water to steam ratio of 1700:1). This causes a piston effect which violently forces unburnt product up through the fire.

Front 6

EFFECTS OF BOIL OVER

Back 6

• Burning product froths and pours down the sides of the tank and into bunded area.
• The velocity of this action can cause a wave that can flow up and over the bund.
• The fire increases dramatically in intensity and the radiated heat is now extreme.

Front 7

IMPORTANT
POINTS

Back 7

• Protect exposures
• Avoid entering bunded areas
• Cool sides of tank to maintain integrity
• Monitor progression of heat layer
• Do not apply water to fire
• Do not apply foam until sufficient concentrate is on scene
• Use aerial appliances and monitors
• Direct foam into vortexes
• Difficult to direct foam from ground
• Use installed systems where possible
• Seek expert advice