Page 317 - Pipelines and Risers

290 Chapter 16

water release a low momentum jet fire may develop if ignition occurs before a significant
cloud can develop. Such an ignition will result in a jet flame.

Combustion
jet fire-There are a number models establishing jetfire characteristics e.g. Shell Thornton. A
jetfire is characterized by flame length and radiated heat flux.

Pool fire- the height of the flame is highly dependent on the depth of the slick, the rate of
combustion of the liquid and the wind speed.

Explosion- clouds of flammable gas can explode when ignited this is termed an unconfined
vapour cloud explosion. (WCE). This type of explosion is relatively mild, and has two
effects; heat and force. The force effects can be modeled using the multi-energy method. For
humans exposed to an explosion heat is the critical factor in determining bodily harm. Force
can also act indirectly on persons exposed to the explosion, injury or death can result from
flying debris or glass splinters. For stmctures it is the effect of force, which is critical.

Damage and Loss
It is also necessary to model the potential damage and loss that can occur to the following
(these figures are obtained from Olshausen, 1998):

1. Humans
- Heat from explosions or fires
The injury is dependent on the dose, which is D= time x (kW/m2)4"
50% death rate is likely when exposed to D50= 2000 sec x (kW/m2)
- Force/missiles from explosions
There is a 50% chance of lung injury at 1.4 barg
There is a 50% chance of perforated eardrum at 0.5 barg
- Toxic effects
0 For a majority of substances the D5o dose is known, that is a product of the time
exposed and the (concentration) which results in a 50% likelihood of death.
2. Material loss
- Repair of pipeline
- Loss of Production
0 This is cost of lost income due to incapacity to provide a product to sell, this is a
function of the time it takes to restore the pipeline to a functioning state.
3. Environmental damage