As practised for decades in fire protection systems, the procedure to check the functionality of foam extinguishing systems includes an annual check of the proportioning rate according to a formula set out in national and international regulations. The results are usually documented in a maintenance log by a hand-written entry.

Unintentional errors sometimes occur when testing the proportioning rate. Most importantly, faulty proportioning rate checks have an immediate impact on the operational success of fire extinguishing systems. If the proportioning rate is too low, it reduces the effectiveness of the extinguishing system. The worst case is that this may allow the fire to keep expanding. An excess proportioning rate results in unplanned foam agent usage and shortens the possible extinguishing operation duration. Another disadvantage of the procedure so far is that extinguishing system operators receive no assistance monitoring the maintenance intervals.

The FireDos proportioner is designed to enable operation in a testing mode as an addition to the regular extinguishing mode. It is intended not to produce any water/foam agent premix while checking the proportioning rate. For this, the proportioner runs in returning mode, i.e., in testing mode. During functional testing of the extinguishing system, the water flow of the firewater pump drives the water motor of the proportioner. In return, the water motor drives the proportioning pump. In doing so, the delivered foam agent is not mixed into the extinguishing water flow but passed back into the foam agent tank via a return line. A special valve in the return line provides the necessary simulation of the operating pressure in the system. The proportioning rate can be checked in two different ways.

Variant 1

After the proportioner has reached a constant operating point, the foam agent flow rate in the return line and the water flow rate are measured simultaneously by volumetric flow meters. The proportioning rate is calculated from both values.

Variant 2

After a constant operating point of the proportioner has been reached, the water flow rate is measured by a volumetric flow meter. The foam agent flow rate in the return line is passed into a separate measurement vessel for a defined period of time. The foam agent flow rate can be calculated from the measured foam agent amount and the period of time of flowing into the measurement vessel. In turn, the proportioning rate can be calculated from the water flow rate and foam agent flow rate.

Both proportioning rate measurement methods are conducted in accordance with the standards EN 13565-1, NFPA 11, FM 4-12 and the formula specified in the Nordtest method NT Fire 042:

Foam agent flow rate [l/min]
---------------------------------------------------------------------- x 100 = Proportioning rate %
(water flow rate + foam agent flow rate) [l/min]

There are various errors and causes. Human error, for example, misreading, calculating or writing errors, may result in an incorrect proportioning rate calculation. Likewise, mistakes in operating the proportioner or the measurement equipment are possible. Because a proportioner's proportioning rate is checked only once per year, the personnel carrying out the work typically cannot gain comprehensive practical experience and routine. Hence, this increases the probability of human error. Increasing time pressure may also increase the probability of errors.

This is where a monitoring system for proportioners, an area of smart proportioner development FireDos is working on, can assist operators and maintenance teams.

Smart proportioners are generally an intelligent upgrade of mechanical proportioners. This upgrade can have different functions and fulfil diverse tasks. The monitoring system for proportioners represents only a section of these. The operating principle upon which the proportioner is based and has proven reliable thousands of times is not changed and remains purely mechanical. Hence, the proportioner itself keeps working without limitations as soon as extinguishing water flows through it.

To verify the monitoring system and to produce data for evaluation, FireDos has developed and installed a prototype system. The design and functioning of the monitoring system are explained using this prototype.

The monitoring system is an intelligent upgrade of the proportioner, including sensors, control unit and display unit. The system controls the automatic measurement, displaying and recording the proportioning rate and additional operating parameters of the proportioner.

A volumetric flow meter is installed in the proportioner's foam agent return line and the extinguishing water line in the model system. The volumetric flow meter in the extinguishing water line primarily displays the accuracy of the FireDos extinguishing agent measurement device based upon the number of revolutions of the water motor.

The monitoring system enables continuous measurement of the foam agent flow rate in the proportioner's return mode and the water flow rate through the water motor. These values form the initial values for proportioning rate calculation. Beyond this, the model system has a control unit equipped with an integrated display. The control unit records the sensor values before processing them and displaying them to the operator. In addition, it saves all values in a log file. The display is an optional component of the monitoring system only. An integrated wireless network interface allows transferring the display image also to a smartphone, tablet or notebook.

The basic version design generally corresponds to the prototype system, using the same three core components: the measurement of the foam agent flow rate, the measurement of the water flow rate and the control unit.

• Measurement of the foam agent flow rate:
  The foam agent flow rate is measured via a volumetric flow meter in the foam agent return line. Optionally, the foam agent flow rate can also be measured in the proportioning line. This is where the foam agent flow rate is measured in cases of extinguishing operations.
  
  
• Measurement of the water flow rate:
  The water flow rate is normally measured by the FireDos volumetric flow meter, but can also be measured by any other existing volumetric flow meter.
  
  
• The control unit:
  The control unit records and processes the required sensor values and determines the proportioning rate and additional operating parameters. The control unit saves the values in a log file. Optionally, the control unit can be equipped with an integrated display and/or a wireless interface, as described above.
  
  To check the proportioning rate, the proportioner is set to returning/testing mode. The firewater pump of the foam extinguishing system delivers extinguishing water through the water motor of the proportioner. The proportioning pump sucks in the foam agent and delivers it back into the foam agent tank. Actual proportioning of foam agent does not take place. The extinguishing water is not contaminated by foam agent.
  
  At the same time, the control unit records the water and foam agent flow rate in the return line. Based upon the measured values, the proportioning rate is calculated. These values are saved in a log file at regular time intervals and are optionally shown on the additional display of the control unit.
  
  Alternatively, the proportioning rate can also be checked in proportioning mode in order to monitor the proportioner during extinguishing operating.
  
  If the unit is equipped with a display, the procedure to be taken for proportioning rate determination can be presented there.

Smart proportioners provide specific advantages to the extinguishing system owner and operator, thus adding value for checking and maintaining the functionality of foam extinguishing systems. The monitoring system for proportioners provides specifically the following advantages:

• Correct proportioning rate determination during maintenance work:
  The proportioning rate, which is the core characteristic when testing proportioners, is always calculated correctly by the embedded algorithm. This excludes any possible calculation errors, allowing flawless checking of the proportioner's functionality. The proportioning rate calculation is, as mentioned above, conducted in accordance with the standard EN 13565-1 and the formula specified in the Nordtest method NT Fire 042.

• Documentation and maintenance date monitoring:
  The date and the proportioning rate values measured during maintenance are recorded. The operator of an extinguishing system can receive a corresponding maintenance reminder for devices installed.
  
  
• Permanent proportioning rate measurement:
  Remembering that water-driven foam proportioners are variable flow devices across their specified range, the proportioning rate is measured permanently and across the entire operating range fully automatically. This allows checking the proportioning rate across the complete operating range, opposed to the present snapshots of the proportioning rate at individual measured flow rates. In addition susceptible errors due to water flow rates not being measured simultaneously, are eliminated.
  
  
• Usage documentation:
  An optional volumetric flow meter in the proportioning line allows measuring the total foam agent and water usage during proportioning operation, i.e., in case of a fire. This allows determining which extinguishing agent amounts have been delivered in a case of operation. Such proof can be of help concerning increasing environmental requirements while in contact with authorities and disposal companies.

• Determining additional operating parameters:
  Other operating parameters can be determined beyond the proportioning rate and usage values, e.g., the foam agent temperature, the oil level in the proportioning pump, the ball valve positions in case of an existing position indication, offer as optional equipment, or the operating times and hours. Operating hours serve as an indicator for the proportioner's service interval.
  
  
• Visualization of proportioning rate and further parameters:
  The proportioning rate, extinguishing agent usage and all other operating parameters of the proportioner are displayed locally. This takes place via a wireless network interface on any smartphone, tablet or notebook. Optionally, a local display is possible. De-centralized visualization is also possible as an option.
  
  
• Recording of all operating parameters:
  The proportioning rate and all other measured operating parameters are permanently recorded with a timestamp at defined intervals. This creates a history that can be used as proof of regularly conducted tests of the proportioner and its use in operation.
  
  
• Improved and more accessible remote diagnostics:
  Using a monitoring system allows improved and more accessible remote diagnostics, even if there is no direct remote access to the control unit and its display. In the most straightforward case, the customer can send display photos to the service team or make a live video call without further effort. This way, the FireDos service team or their service partner can provide remote support, e.g., for checking the proportioning rate.

• Saving costs through reduced service efforts on-site:
  The improved remote diagnostics reduce the on-site service efforts for FireDos or their service partners. This reduces the service costs for the system owner.