TYPES OF FOAM MAKING EQUIPMENT

 TYPES OF FOAM MAKING EQUIPMENT

Foam making equipment provides the necessary means for the production of mechanical foam, which is used for fighting B class fires (Flammable liquids) , these fires present themselves as contained tank fires or spill fires. There are three things necessary to create foam

• a. Water 
• b. Foam concentrate
• c. Air

There are two ways a foam can be created at foam making branch

• One way is by Inducting the foam concentrate at the branch using pipe dipped into the foam concentrate cans and getting mixed along with the incoming water and aspiration of air through air inlets. 
• Instead of inducting supplying the premix foam concentrate and water using an inline inductor and then this premix is pumped to the foam making branch where the air is aspirated through air inlets 
• In the above situation’s venturi principle is used to induce foam concentrate into the water stream moving with pressure 

The effectiveness of the foam in fighting fire depends upon many properties of the generated foam like the expansion of the foam, stability, fluidity, sealing, burn back resistance etc.  For these properties to be achieved the foam generated should be of high quality which in turn depends upon the equipment used to generate foam. The two major foam equipment used are. 

• 1. Foam making equipment 
• 2. Foam concentrate induction and injection equipment 

TYPES OF FOAM MAKING EQUIPMENT

These equipment are designed to work on a self-aspirating principle in which air is inducted into the stream of the foam-water solution by the suction effect created at the water head in the branch during discharge of foam solution under pressure. The different types of foam making equipment used are

• 1. LX hand-held foam-making branches
• 2. LX hand-held hose reel foam unit
• 3. LX foam generators
• 4. LX foam monitors
• 5. MX hand-held foam-making branches
• 6. MX foam pourers
• 7. HX foam generators.

• LX hand-held foam-making branches: LX means LOW EXPANSION and these are operated by hand hence these are called LX hand-held foam making branches, these branches are used where low quantities of foam are required for firefighting.  These are made of either stainless steel body or aluminium designed in different sizes like  5x, 10x and 20x with or without inline inductors, these are designed for FLOW of 225 LPM to 900 LPM at 7 bar PRESSURE with EXPANSION RATION of 1:2 to 1:12.

• LX hand-held hose reel foam unit:  This unit comes as a portable unit that contains up to 11 litres of foam concentrate which is connected to the incoming hose reel through an adaptor and water is supplied between 2 to 10.5 bar where some portion of water pressurizes the foam concentrate to enter the main water stream and passing as a premix solution to the main foam making branch. These are designed to give foam solution flow rate at 50 litres/minute at 4 bar 

• LX foam generators:  These are modified version of the inline inductor, it inducts foam as well as expand and it also transports the foam to a long distance. The foam induction is around 3% or 6% with a maximum working pressure of 10 bar. The flow is designed to be at 7 bars with either 225 LPM or 450 LPM

• LX foam monitors:  These are larger versions of  foam making branches which cannot be lifted by hand, they are fixed standing or mounted on trolleys or appliances and they have multiple water connections . They are numerous foam monitors in the market and they are available in wide range of nominal flow and inlet pressure requirements.  A typical foam monitor can be designed between 1890 LPM to 30200 LPM at 7 bar using 3% foam induction.

• MX hand-held foam-making branches: MX means MEDIUM EXPANSION and these are operated by hand hence these are called MX hand-held foam making branches, these branches are used to where MEDIUM quantities of foam are required for firefighting.  These are designed in different sizes 

• MX  foam pourers: These are designed to pour foam rather than projecting it on fires, these are larger than the conventional foam making branches and available as free-standing or handheld type, these are typically used to fill bunds and areas around fuel storage tanks. They operate in the same way as MX hand-held foam making branch.

• HX  foam generators: HX means HIGH EXPANSION. These are designed to produce finished foam of expansion ratios of 200:1 to 1200:1.  Airstream is created by the fan and the foam solution is sprayed on the surface of the fine net screen. These are very heavy and bulky items that are required to be carried on special vehicles designed to meet these specifications. A flow of  LPM the foam output is around 155 m³/min  with an expansion ratio of 1000:1

FOAM CONCENTRATE INDUCTION AND INJECTION EQUIPMENT

This equipment is designed to introduce foam concentrate into the water supply line which is attached at a distance away from the foam making equipment so that the required foam is produced at the foam making equipment outlet. This induction and injecting equipment working effectiveness is very important as this reduces the wastage of foam concentrate and ensures firefighting is not hampered.

The more the foam concentrate the lower the rate of the foam concentrate to be inducted into the water stream and vice versa, if the foam concentrate is not properly inducted that will result in two situations

• More foam concentrate being picked up:  This will result in a foam that is very thick which does not have adequate flow to cover the entire area of fire 
• Less foam concentrate being picked up:  This will result in foam that gets drained very easily and does not form a  blanket. 

The most common type of induction equipment used by used 

• 1. INLINE INDUCTORS: This equipment employs the venturi principle to induce the concentrate into the water stream. It is very important and necessary to match the flow and pressure characteristics of the foam making equipment with that of an inductor. 

• 2. ROUND THE PUMP PROPORTIONERS: This equipment is permanently designed around the pump to pump water and foam concentrate using a proportioner that produces a rich foam solution. The main advantage of these round the pump proportioner is there is no pressure loss

Article by PJ Mohan

Sr.Faculty, NIFS