Inside every Leister hot air tool is a heating element composed of a ceramic honeycomb supported resistance wire filament (See below). Electric resistance wire heaters work on the principle that when electrical current passes through a conductor heat is generated, and the amount of heat generated is related to the resistance of the conductor.
Some resistance wire heaters are able to function without airflow because they have been designed in such a way that they will not reach temperatures above their safe operating limits. Examples include: a toaster, some ovens, wrap heaters, some space heaters, etc.
However, Leister heaters are designed to operate at very high temperatures—most are designed to heat airflows up to 650°C, and some up to 900°C—and as a result require airflow at all times. To reach these high air temperatures, the heating element must be capable of reaching even higher temperatures. Without adequate airflow, the element will heat up unchecked and will exceed safe limits, leading to the destruction of the element.
While Laser IR Thermometers are an extremely common tool, they are entirely ineffective for measuring the outlet temperature of an air heater. To understand why, we must first understand how this tool works. Laser IR Thermometers measure the surface temperature of an object by measuring the thermal energy emitted by the target. Knowing the amount of thermal energy discharged and the emissivity of an object’s surface, the object's temperature can be determined by the device.
When measuring a heater’s output air temperature, the largest issue with these tools is that they measure surface temperatures. As the heated air is transparent, the measurement will always be the surface temperature of a nozzle or a component of the heater housing; and frequently it will be an exterior surface. These items will always be cooler than the heated air, often by a significantly larger margin than the user would expect. To accurately measure the output temperature of an air heater you must measure air temperature and laser IR thermometers are incapable of doing so.
Growing insulation requirements have resulted in changes to roof structures in recent years. Rigid polyurethane (PUR), polyisocyanurate (PIR) or thicker mineral wool insulating materials with a higher level of compressive strength are now installed on the upper side of the roof deck. During the welding process, these insulating materials demonstrate virtually no elastic behavior resulting in a harder welding surface. This may cause air inclusions (bubbles) to form in the weld seam of mechanically fastened PVC roof sealing sheets under certain conditions, particularly if the roof substrate is uneven.
The new rake nozzle kit from Leister ensures that all leak-tightness and aesthetic requirements are met even in roof structures of this nature. The rake nozzle provides constant pressure on the lower PVC sheet. The soft silicone pressure roller ensures the pressure is distributed as effectively as possible over uneven and hard substrates.
If you're having problems with air inclusions in your welds, contact us today for more details.
A properly prepared substrate should be solid, evenly laid, and free from debris such as loose screws or stones.
If it is raining, welding must not be carried out without special protective equipment.
Welding must be suspended at temperatures below +5°C in order to prevent the material from being exposed to an excessively high thermal load (in accordance with DVS 2225-4).
In some cases, excessively high humidity can cause condensation to form on the welding surface, which has a negative effect on seam strength.
If there is strong wind, the tool may not reach the required welding temperature. This can be counteracted by raising the welding temperature by 20 to 30°C or reducing the speed by 20 to 40 cm/min. If the wind is excessively strong, the welding area should be shielded against wind or welding should be suspended.
Prolonged exposure to the sun can cause the material to heat up significantly causing thermal expansion. This causes wrinkles which makes the welding process more difficult and leads to an unacceptably high level of tension in the seam area when the material cools.
Maintaining the Tools
The air inlet and filter should be cleaned frequently and the heating element removed and cleaned periodically. This ensures the tool is able to produce the correct air volume and temperature output.
Using Generator Power
The generator must have the correct specifications in order to ensure safe operation:
Manual Welding Process
The distance between the pressure roller and the nozzle opening should be between 20 and 30 mm to ensure that the weld seam is joined as efficiently as possible. The pressure roller must be guided so that it is parallel to the nozzle. This will ensure that the welding process yields the best possible results (see images above).
The hot-air nozzle should be cleaned periodically to keep the contaminants out of the welding seam. A blocked nozzle will restrict the tool’s air output which may cause fluctuations in the output temperature.
Radius welding is quick and efficient with the UNIROOF AT / ST. Pipe collars, exhaust vents, and other roof features can be welded easily and quickly with the flexible axle of the UNIROOF AT / ST.
Taking the time to perform maintenance on your machine now can save you downtime during the roofing season. We recommend you do the following things:
We often get questions and see repairs with problems that can be traced back to the generator, cord, or plug being used while on the roof. This article covers best practices and our suggestions for generators, cords, and plugs for roofing tools like the VARIMAT, SARNAMATIC, and TRIAC ST.
The size of generator you need depends on which tool, and how many, you are using. When using a generator, ensure that the maximum current capacity is never reached as the resulting voltage spikes can damage equipment. We recommend that a generator is not run above 85% of its rated power. If the generator begins to roar, it may have reached its maximum capacity.
The minimum generator capacity required when using only a VARIMAT is 6000W with at least 5000W of continuous output; for a BITUMAT minimum 8000W with at least 7000W of continuous output; for a SARNAMATIC minimum 8500W with at least 7500W of continuous output. If a 120V hand tool, such as the TRIAC ST, will be used simultaneously a continuous output of 10,000W or higher is recommended.
Never turn the generator on or off with the tool connected and switched on. Dirty or water-contaminated fuel, undersized generators, or poorly maintained extension cords can cause voltage spikes which may blow fuses or damage circuit boards in the equipment.
Do not put undue stress on a tool’s electrical cord. Carrying the tool by the cord, using the cord to correct tracking, or otherwise pulling on the cord should be avoided.
Be sure to use a 10 gauge or thicker cable if you plan to make a 30 metre (100 foot) or longer extension cord.
If the cord feels hot to the touch, check that the plug contacts clamp down on the bare wire only and not on the conductors around them.
When installing a plug, be sure to screw down the wire contacts onto the bare electrical wire only and not clamp down on the insulation of the wire. Bad contacts cause sparking which may cause the cord to heat up and could damage the equipment.
When connecting a 230V twist-lock plug to a cord:
Have questions? Give us a call at 1-888-438-6324 or firstname.lastname@example.org.
Simple tips and tricks to use and optimal operation of UNIROOF AT.
We often get questions from customers about the VARIMAT V2 and the BITUMAT B2. These machines seem similar on paper but are specialized to deal with specific roofing materials.
The VARIMAT V2 and BITUMAT B2 are both designed for flat roof work and are best suited for basic welding seams, not detail work. They perform exceptionally well on long, straight runs. They have similar drive speeds, dimensions, and looks and they both achieve their welds using hot air. Beyond this, the tools have little in common.
The largest difference between the VARIMAT V2 and BITUMAT B2 is the material they are designed to weld. The VARIMAT V2 is made exclusively for use on single ply thermoplastic materials whereas the BITUMAT B2 is made exclusively for use on modified bitumen. Although a popular request, one machine cannot weld both materials.
The welding seam width that each tool provides is optimized for the material as well. The VARIMAT V2 welds 40 mm seams while the BITUMAT B2 welds 75 or 100 mm seams, depending on the model.
The BITUMAT B2 carries an extra 5 kg (11 lbs) of weight and has a slower top welding speed of 6 m/min. (19.6 ft./min.). The BITUMAT B2 has a power output of 6700W while the VARIMAT V2’s output is 4600W. This added power output, along with the heavier machine, allows the BITUMAT B2 to handle the more difficult task of welding modified bitumen.
Other aspects of the tools like the nozzle design and pressure roller material are optimized for the material as well.
Have questions about these tools? Contact your Technical Sales Representative for more information.