The most common SPF applications are in the construction market with commercial roofing and perimeter wall insulation as the leading segments. It is not always practical to lift the machine and all its auxiliary components out of the truck, onto a roof or into a residential home. For this reason, most SPF machines use several hundred feet of hose to deliver the raw materials to the spray gun for applying to the remote roof or wall surface.
As mentioned previously, SPF commonly needs to be heated to 120°F-140°F for optimum processing. Heating the material is the job of the pre-heaters located on the proportioning machine. Heated hoses are a secondary heating source used to maintain the chemicals at the required temperature until they are mixed and applied with the spray gun.
Heated Hose Construction
The way the heated hose commonly works is via a copper wire band that is spiral wrapped down the hose inside of a protective polymer / butyl jacket. This wire or braid is supplied with low voltage electricity engineered at a pre-set electrical resistance level to create heat. The heat is conductively transferred from the outside of the hose into the liquid components within the hose.
The butyl jacket not only acts as a protective covering to protect the elements, but butyl has a relatively low vapor transmission permeability level to prevent moisture from intruding into the hoses. This is especially important on the isocyanate (a-side) side, because moisture reacts with iso making it brittle and hard which can ruin a hose and cause other processing problems.
Heated Hose Length
The length of hose is dictated by the specifications of the machine. A machine’s maximum hose length is typically in the 200ft to 310ft range. Most all machines will allow you to run at hose lengths shorter than the maximum rating, but running at lengths greater than the maximum rating will often result in an inadequate heating situation. Some suppliers offer an optional “booster pack” that provides greater heat capacity to accommodate longer than 300ft hose lengths.
Most hose manufacturers build the heated hoses in 50ft lengths. In order to get 300ft of hose on your foam machine, you would have six (6) – 50ft lengths of heated hose all connected together using high pressure JIC style fittings. Heated Hose diameters are typically ½ inch or 3/8 inch. These are often determined by output and pressure configurations need for each particular application.
Longer hose lengths require the machine to supply more electrical current (amps) to the hose to supplement the longer length. Some machines have built in electronics and sensors to read the length of heated hose and automatically set the required amperage to the hose. Yet most spray foam equipment uses a tap setting on the electric transformer that operator manually sets to match the length of hose in use. Therefore if you commonly change the length of heated hose, you should be aware that you may also have to make an adjustment of the machine for this.
The reason for the hose heat transformer is because most spray foam machines require high voltage (220v) power to operate. To make the hose heating system safer for the operator, the machine “steps down” this voltage to a safer lower voltage.
Hose Heat Temperature Control
The heated hose system for a spray foam machine is controlled by the Hose Heat Temperature Controller in the Main Electric Console. This is where the operator manually enters the hose heat set point, or desired temperature you want your hose heat to operate at. The hose heat controller “turns on” or “turns off” the hose heat as required to maintain a relatively consistent temperature at the set point.
We mentioned earlier that the hoses are configured in a multiple number of 50ft sections. In order for the hose heat system to work, there is a device called a Temperature Sensing Unit (TSU) or Fluid Temperature Sensor (FTS) located between any two (2) of the hose sections. It is normally placed at the last hose section to be as close to the gun as possible to get an accurate reading of the process temperature at the gun, or place of application.
Gun Hose Whip
The last hose in the system is referred to as a gun whip. It is normally a smaller diameter of unheated hose at a 10ft length. The purpose of the gun whip is to provide greater flexibility and easier manipulation of the spray gun to assist in a more controlled application and better use of the gun.