Protecting Occupied Buildings from Process Tank

Rupture SpillageDavid Ho - Principal Consultant/Manager

– Advanced Analysis

November 2016

Tank rupture is rather rare – though if it occurs the consequence can be catastrophic:• The spillage can destroy

surrounding buildings• It has enough energy to overtop

bunds • And very importantly, lives can

be lost

Boston molasses tank rupture (1919)

Fuel oil tank failure – Ashland Oil (1988)

Fertilizer tank collapse – Allied Terminals,

Virginia (2008)

These pictures show a few well-known tank failures that have occurred in the US…

Tank collapse spilling radioactive slurry -

Ranger Uranium Mine (2013)

Water tank rupture – Sunshine Coast

(2015)

Leach tank rupture – Ravensthorpe nickel mine (2014)

In Australia, recent tank failures have been reported in the media

Tank Rupture Hazard Identification & Risk Management –

A Case Study

A minerals processing facility owner required an analysis of their facility to identify hazards and manage the risks should one of their on-site tanks rupture.

• The facility has aboveground processing tanks• If one of the tank ruptures an engulfment hazard

will occur• Need to identify which occupied buildings will be

affected• Want to plan for future building locations on site –

temporary and permanent – without exposing staff to risk

Tank Characterisationand Rupture

The critical parameters that could give the worst type of spillage were considered.

The parametric study found that the tank height and fluid density would have the greatest impact on the surrounding buildings.

Tank Characterisation and Rupture

How different rupture openings could affect spillage were considered.

The panel failure at the base of the tank was selected because the jet of liquid can flow further and last longer, affecting buildings

further away from the tank.

Consequence Modelling

• The spillage was simulated using Computational Fluid Dynamics (CFD)

• In the modelling, the tank was put on flat and site-specific terrain

• Other objects were included in the model• The analysis tracked how the fluid

escaped from the rupture opening and provided the flow velocity, depth and pressure along the flow path in space and time

This shows what happens about six seconds after a rupture occurs at the base of this tank.

The liquid jets across the road hitting the buildings on the other side.

Some liquid has enough energy to reach the storage silos further away.

This shows another area where there is a retention pond between the tank farm and an occupied building which is elevated above ground. The building is supported on stilts.

The spill flows into the retention pond and out the other side and towards the building.

Impact on Buildings

• It is more desirable to perform a high-level assessment if it can be done

• The maximum head and flow depth around each tank was quantified as a panel rupture could occur at any position around the tank

• From the simulation results, contour plot maps of maximum head and maximum flow depth can be obtained

• The pressure acting on a building wall can be quantified and estimated anywhere on site

Impact on BuildingsTop graphsThe maximum pressure and maximum flow depth away from the ruptured tank.

Bottom graphics Results are plotted around each tank ignoring the presence of the other tanks and objects on site.

Impact on Buildings Height of wall

Pressure

Maximum flow depth

2 x Maximum flow depth

Maximum head

As long as the maximum pressure head and flow depth are known, the likely pressure on a building wall can be estimated.

The structural integrity of the building can then be assessed.

Protective Measures

• If building relocation costs are too high, buildings need to be protected

• A barrier to deflect flow is a method to protect existing buildings

• CFD modelling can be used to evaluate barrier concepts

• Further site-specific modelling can be used to consider other site constraints

Protective MeasuresA number of barrier profiles were examined to see which one could best deflect the flow.

The assessment criterion is that no liquid can go over the barrier.

The graphics on the right show snap shots of the flow hitting the barrier.

The flow is deflected up and back and in this case no overtopping occurs.

Protective MeasuresOnce the barrier profile was selected, its effectiveness is further tested in the site model.

In the snap shot to the right, you can see it protects the buildings.

• Hydrodynamic behaviour of spillage from a ruptured tank – captured by CFD modelling

• Impact on existing buildings along flow path• Likely impact to the wall if a building were in the

flow path• Evaluate effectiveness of barrier concepts

Conclusions

• Hydrodynamic behaviour of spillage from a ruptured tank was captured by CFD modelling

• Impact on existing buildings along flow path was determined

• The likely impact to the building wall was assessed

• Effectiveness of barrier concepts were evaluated