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How to connect intermediate bulk containers (IBC) as foam agent tanks with a common suction line

The key elements of a foam-based extinguishing system are a foam agent tank, a proportioning system and a monitor or sprinkler. Instead of a single foam agent tank, it is possible to connect and use several intermediate bulk containers (IBC) as foam agent storage. This is not a preferred option as the tanks will have to fulfil several requirements.

The ideal application of IBCs as foam agent tanks means the tanks are all interconnected independently of the suction line. If the IBCs are not independently connected, only the first IBC will be drained, and then air will be sucked before the additional IBCs will be drained. This will create high pressure peaks which can potentially damage installed equipment downstream and the proportioning of foam agent is interrupted.

Incorrect layout: Intermediate bulk containers (IBC) as foam agent tanks

Incorrect: A parallel IBC connection with the suction line does not work.

The crucial factor: The dimensioning of the suction line

The dimensioning of the suction line including the diameter of the connection to the IBC, is crucial. The type of foam agent used and the quantity required will determine whether the IBC connection is sufficiently dimensioned. The majority of IBCs only have a 2" connection which would limit the flow of foam concentrate and the resulting water flow to that shown in the table.

  Low viscosity foam agent  High viscosity foam agent 
Max foam agent flow through 2” connection   150 l/min 100 l/min
Max resulting water flow with 1 % foam concentrate 11,500 l/min 7.690 l/min
Max resulting water flow with 3 % foam concentrate 3,840 l/min 2,500 l/min
Max resulting water flow with 6 % foam concentrate 2,100 l/min 1,400 l/min

The values will not change when connecting the suction line to multiple IBCs in parallel. Only the IBC with the lowest path of resistance will be drained. This phenomenon is not specific to FireDos proportioners, but applies to all suction lines for all foam agent pumps.

the solution

  • Use a dedicated storage tank with a properly calculated and dimensioned connection and suction line.
  • Interconnect all IBCs independently of the suction line (serial connection). This will though result in a limitation of the max allowed water flow due to the 2" connection.

Correct: Additional interconnection of IBCs

Correct: Serial connection of IBCs

The foam agent return line

When connecting multiple IBCs, the correct arrangement of the foam concentrate return line is an additional factor to be observed. As a unique feature of FireDos proportioners, a foam concentrate return line can be added for testing purposes by returning the foam concentrate to the foam concentrate storage tank. This means no foam solution is discharged, saving considerably on costs. We recommend returning to the most remote IBC at the end of the interconnection. This will ensure that the foam concentrate is circulated equally in all IBCs.

Of course, this information also applies to the use of several suitable foam agent tanks. Basically, IBCs are containers for transport purposes only and, therefore, are quite unsuitable as foam agent tanks.

Contact us for suction line calculations

FireDos, as part of its customer service, will assist in providing dimensional calculations of the suction line or verifying the proper dimensioning of existing suction lines.

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