Fighting high hazard and storage tank fires is one of the most challenging scenarios firefighters and crisis management teams must plan for and manage, says fire protection foam dosing technology company DoseTech.

DoseTech states that the occurrence of high hazard fires has reduced in the last few years suggesting training and testing standards have improved, supported by testing from industry bodies such as Joint Oil and Industry Fire Forum and LASTFIRE.

This is an achievement in that global storage capacity is expected to double from 2005 to 2025 from about 600-million cubic metres to over one-billion cubic metres.

However, DoseTech states that the oil industry faces increasing challenges and opportunities. These include the legislative and enforced change from environmentally harmful polyfluoroalkyl substances type foams to fluorine-free foams.

The oil and gas industry’s adoption of Industry 4.0 and digital solutions for remote monitoring, control and testing, also means a reduction in site manpower requirements.

Fixed Systems

Fixed systems remain a central hub of any fire protection system. However, owing to the rapid breakouts caused by unknown and uncontrollable events, fixed systems may get damaged by the fire incident itself.

Fixed systems consist of a firewater main pump feeding a hydrant with fixed monitors, foam pourers for tanks and sprinkler systems for storage areas. The foam concentrate is stored in a fixed atmospheric or pressurised storage tank, with a proportioner to deliver the recommended mix of foam concentrate into the extinguishing water stream.

Operators and end-users are increasingly looking to provide hybrid solutions, says DoseTech; the ideal being a fire protection system using a fixed system aided by a team with versatile mobile equipment which can be rapidly deployed, depending on the hazard.

The use of mobile firefighting equipment which is easy to deploy and use will become an integral method to fight large fires as the cost and complexity of fixed systems increases.

Mobile Firefighting Equipment

DoseTech says the challenges for many mobile applications are the potentially long hose lengths, restricted diameters and the pressure drop associated with many pieces of equipment.

Bladder tanks and balanced pressure proportioner systems combined with venturi-based proportioners are designed for fixed installations with a fixed range of pressures and flows. These proportioners are easy to design and install, however, there is a trade-off, such as their lack of suitability for mobile applications and varying firefighting approaches.

The ideal design for mobile equipment is components that are external power independent with a low pressure-loss, consistent proportioning rates irrespective of foam concentrate viscosity at varying water flows, and back pressures that are easily and rapidly deployed, suggests DoseTech.

Mobile Proportioner Design

DoseTech states that FireDos GENIII hydraulically driven foam proportioners present significant advantages:

Accurate proportioning rates

Water from a hydrant is used to drive the positive displacement water motor, which in turn drives the plunger pump of the foam proportioner. As each revolution have a fixed volume, it becomes easy to determine the fixed proportioning rate. As the water flow increases, this in turn increases the volume of foam concentrate pumped into the water motor and into any mobile foam outlet devices.

Testing

“Having the ability to circulate the foam concentrate back to the tank is a saving provided by FireDos GENIII proportioners,” says DoseTech. This eliminates short- or long-term environmental impacts, such as associated disposal. Mobile foam testing is National Fire Protection Agency-compliant.

Capacity limitations

An Intermediate Bulk Container tank typically contains 1 000 litres of foam concentrate, providing a limited firefighting capability. For small applications up to 1 000 to 2 000 litres extinguishing water per minute (LPM) with a 3% nominal foam proportioning rate, an integrated trailer could provide 17 minutes at full flow.

For medium water flows above 2 000 to 4 000 LPM, separate mobile proportioners fed by foam concentrate tankers are recommended.

The versatility of FireDos foam proportioners means they are not susceptible to changes in back pressure or flow restrictions, guaranteeing foam quality at the specified percentage regardless of flow rate.

Pressure loss

The GENIII is designed with a maximum pressure drop of 1.5 to 1.9 bar, depending on operating conditions. A low-pressure drop across the proportioner, combined with an ideally designed monitor and mobile mounted equipment presents a better option.

DoseTech mentions that FireDos introduced their range of approved firefighting monitors for water and foam with flows ranging from 500 LPM at 6 bar to 60 000 LPM at 16 bar. Each model is designed using a low pressure drop, reduced ballast tank and adjustable flow during operation for trailer mounting.

The reputational damage associated with large fires is often worse than the tangible costs. Modern operators must consider the costs of foam discharges and any short- or long-term damage to the environment.

“Using equipment designed for mobile use, rather than modifying equipment initially designed for fixed extinguishing systems is one such method to achieve better outcomes,” claims DoseTech.