SME Foam Generator Discharge Devices | Medium Expansion Generator


Medium Expansion (MEX) foam generators are designed to expand foam solution into a stable aggregation of bubbles with discharge expansion ratios from 20:1 up to 200:1, which is dependent on the foam concentrate, used and supply pressure. Foam solution enters the generator through a sized orifice inside the inlet tube and is sprayed onto a mesh diffuser screen. The increased velocity through the inlet orifice creates a venturi effect and aspirates air into the spraying foam solution creating a homogeneous finished foam. The produced foam is capable of flowing into hard to reach areas and limits the release of flammable vapors due to its thick foam blanket. The expanded foam properties makes it suitable for indoor and outdoor use.

MEX generators are usually part of a fixed deluge or flow control system and shall be used in combination with a suitable foam proportioning system. They are suitable for use in total flooding or local application systems. Foam Concentrates developed and tested to work in medium expansion systems should be used. It is important to consider that different foams will have varying expansion performance through a medium expansion generator.

Medium expansion foam systems are commonly used on hazards with ordinary combustibles (Class A) or ignitable liquids (Class B). These hazards are commonly found in process areas, chemical storage, tank farms, loading areas and fuel transfer facilities for example.

This technical data is intended for trained experts. It contains basic information needed to use the product described.  Technical data can be found on the Fomtec website. For further information, please contact Fomtec or refer to the technical documentation. The contents of this publication are subject to modifications without notice.

Listings and approvals


Construction features

  • 6 standard size options for optimum design flexibility
  • No moving parts and no external power requirements
  • Vertical, horizontal or diagonal installation
  • Stainless steel body
  • Grooved or threaded connection

Standard materials - Medium Expansion Generator

Generator Inlet Pipe Stainless steel AISI-304
Main Body Stainless steel AISI-304
Inlet Orifice Stainless steel AISI-304
Foam Diffuser Screen Stainless steel AISI-304
Handle (were fitted) Plastic

Scope of delivery

Ensure that all components are complete and in good condition.

Unit supplied with integrated orifice and foam diffuser.

Not Included:
Fixing material, inlet connection fitting / coupling.


Please contact Fomtec for further information.

SME-Medium expansion generator

Product variants

  • UNI-45, UNI-70, STORZ, BSS, NH threads or UNI, DIN, ANSI, ASA flanges
  • Non-standard connections may be available on request.

Performance data

Notice: The following data is based on the Medium Expansion Generators referenced in this data page working together with the specific foam concentrates at their tested flow rates and pressures. Actual site conditions may produce different results.

Different foam concentrates will produce different expansions characteristics depending on variables such as the inlet pressure, generator size or water quality for example. Performance is generic or general. Table 7.1 in the datasheet is designed to give an overview of the MEX generator performance based on the foams detailed. Data is based on internal testing of actual discharge performance.

The protection scheme philosophy should be considered when selecting the foam concentrate to use. When used in a total flooding system designed to fill a given volume in a given time, it is important that the foam has good expansion and is stable without collapse. Whereas in a local application system based on area/density a lower expanded foam could be more suitable to avoid overwhelming the protected area such as a fuel storage tank farm.

Other considerations relate to the other types of system on site if sharing the same foam supply. If there are a combination of Low Expansion and Medium Expansion Systems then the foam concentrate should be suitable for both types of application. Generators have a throw capability of between 1 metre and 8 metres depending on generator size and inlet pressure. Most of these generator / foam combinations are at the lower end of the medium expansion foam range as applications tend to be external and if the expansion is too high then the discharge and foam blanket could be adversely affected.


If applicable, refer to the requirements of NFPA11 or EN13565-2. In addition, the “Authority Having Jurisdiction” (AHJ) may have additional installation requirements that must be followed.

The generator can be installed vertically or diagonally angled downwards. It can also be installed horizontally. Ideally, the inlet end of the generator should be outside the risk area to avoid any effect from fire on the expansion performance. Whilst the generator weight is supported from the inlet connection, it is advisable to bracket the main body or build a suitable support to prevent stresses on the inlet connection during discharge.


Medium Expansion Foam Generators are part of a fixed fire protection system incorporating a water supply, system pipework, foam concentrate, foam storage tank and proportioning / admixing system. In a fire condition, the detection system will activate and sound the warning alarms. The deluge or flow control system(s) will then be released via a releasing panel working in conjunction with the detection system. Once the deluge or flow control valve is in operation, the incoming water supply is mixed with the foam concentrate using a proportioning / admixing system thereby creating foam solution. Once the system pipework has filled and is up to the required pressure – medium expansion foam discharge will begin.


For details of warranty, contact Fomtec directly.

Inspection, tests and maintenance

Notice: The owner is responsible for maintaining the fire protection system and devices in proper operating condition.

Warning: Any system maintenance or testing that involves placing a control valve or detection system out of service may eliminate the fire protection capabilities of that system. Prior to proceeding, notify all Authorities Having Jurisdiction. Consideration should be given to employment of a fire patrol in the affected area.

Refer to respective requirements of NFPA11 and/or EN13565-2. In addition, the “Authority Having Jurisdiction” (AHJ) may have additional maintenance, testing and inspection requirements that must be followed. This device has no specific maintenance activities but an interim inspection shall be made to ensure debris is not blocking any part of the device.


At end of use the product described here should be disposed of via the national recycling system.

Accessories and spare parts

This device has no accessories or spare parts.

Declaration of conformity

If required. Contact Fomtec for further information.