RECOMMENDATIONS FOR A PROPER INSTALLATION OF CARTRIDGE HEATERS
-Distribute the required load over the highest possible number of heaters in order to reduce the density in W/cm2 of each heater.
-Insert the ULTRAMAX cartridges in bored holes. Clearance between heater and hole reduces heat transmission, increases cartridge temperature, intensifies the oxidation process, increases energy consumption and considerably decreases heater life.
-If the cartridges are mounted on moving parts of the machine, make sure the cables are well anchored a few centimeters upstream of the heater’s outlet to prevent movements that could result in break-downs. Even though small movements are generally acceptable, there is always a high risk of break-downs. It is advisable to make a few extra turns of the cable upstream of the outlet to lengthen its life. If the application requires continuous movement, it is indispensable to advise Rotfil with the width and type of motion. In many cases an intermediate box is very useful for transferring motion to an additional cable that can easily be replaced.
-If there are a significant number of vibrations, it is advisable to use an intermediate connection box as described above.
-Protect cables and cartridge head, especially if not sealed, against contamination from oils, liquids, sprays, corrosive gases, splashes of water. With repeated hot/cold cycles, the cartridge absorbs any substance that comes into contact with the insulating material. Most substances char and produce short circuits. The only sealant that ensures total protection is SC400 (see page 20). -If the cables stay in areas with a constant temperature above 250 °C, one of the following actions becomes indispensable:
-Use flexible nickel cables insulated with ceramic fiber or ceramic beads.
-Use rigid nickel conductors, not insulated or insulated with a sheath of ceramic fiber or ceramic beads.
-Extend cold zone of heater enough to bring the cables out of the high temperature area.
-Prevent the cartridge head, and consequently the cables, from entering the hole. The heat of the metal ground could damage the insulating material and the sealant.
-Avoid using adhesive tape near the cartridge head. The adhesive of certain types of tape could enter the head, char and produce short circuits. If taping is unavoidable, use silicone-base adhesives.
-At high temperatures it is always advisable to thermally insulate the heated parts. The following positive effects are obtained by insulation: energy consumption is lowered by up to 40%. less powerful and consequently longer-lasting elements can be used. higher temperatures are reached in a shorter time.
-To improve heat conductivity and ease the extraction of the cartridge, use our LUBRIHOT compound. Make sure the compound does not dirty the cartridge head as this could result in electricity leakage or short circuits.
-Place the external thermocouples no further than 10 mm from the cartridge and, if possible, in the central area. This warning is extremely important when the cartridge has a high watt density. The use of proportional microprocessor thermoregulators is essential for extending heaters’ life.
-Oxidation of ULTRAMAX heaters and the hole in which they are inserted, produced by many hours of work at high temperatures, can make it difficult to extract the burnt element. After having attempted extraction by using EXTRACTOR (see in the accessories section), make a hole with a bit 0.2-0.3 mm smaller than the nominal diameter of the heater. After extraction, use a boring machine to re-bore the hole; if necessary, use an iron rod and a hammer as well.
-A ROTFIL cartridge heater, if used correctly, provides a very long life. To obtain maximum performance, advise Rotfil with all the details that might be important in order to determine the most suitable heater.
STANDARD TOLERANCES ON ULTRAMAX CARTRIDGE HEATERS
||The tolerance is indicated in correspondence to the various diameters listed in the catalogue|
||up to 100 mm ± 2 mm|
over 100 mm ± 2%
Resistance varies together with temperature. At ambient temperature, resistance is approximately 5% lower than at working temperature.
||For lengths of up to 300 mm|
0.1 mm every 150 mm
Over 300 mm, apply the following operation:
Arrow=L² X 4 / 1,000,000
L=length of heater in mm
In any case, given the heater's flexibility, the arrow will hardly be a problem upon being inserted into the heater, even if the hole has strict service.
|Tolerances stricter than standard can be agreed upon with our Customer Service|
HEATING OF LIQUIDS
The compactness and high watt density of Ultramax heaters make it an excellent solution for the heating of liquids.
-Place the heater as far as possible from the tank walls to favour the highest circulation of liquid by convection. -Make sure the heater is always covered with at least 20 mm of liquid. -Avoid too frequent ON/OFF cycles using a proportional thermoregulator. -Make sure no powder, rust, lime deposit or other foreign substance pollutes the heater’s sheath. -To avoid emptying the tank when replacing the used heater, is advisable to use our additional sheaths. -If there is risk of liquid’s overflowing, or there is humidity or steam, sealed heaters shall be used. -Do not exceed the densities in W/cm2 suggested in the following table. Shall there be forced re-circulation, the density can be slightly higher. A lower density, on the other side, increases the heater’s life.
|Asphalt, tar and high viscosity compounds
|Petrol - Kerosene
|Metals in liquid state
|SAE 30 motor oil
|Caustic soda 10%
|Caustic soda 75%
TEMPERATURE TAKEN ON BY SHEATH AT VARIOUS WATTAGE DENSITIES
MAXIMUM DENSITY ON THE ULTRAMAX HEATERS, USED IN HIGH TEMPERATURE ENVIRONMENTS
HEATING OF METALS
Maximum admissible clearance in millimeters between hole and ULTRAMAX cartridge as a function of the density in W/cm² and the working temperature
Maximum admissible clearance between hole and ULTRAMAX cartridge as a function of the density in W/cm2 and the working temperature. For aluminum and brass, choose the clearance in the column corresponding to the temperature immediately superior to that of the working temperature (+ 100 °C).
The clearance is obtained by the difference between the hole diameter and the real diameter of the cartridge (nominal diameter -maximum tolerance).
Example: hole diameter 12.6 mm nominal diameter of cartridge 12.5 mm
12.6 mm - 12.42 mm (12.5 -0.08 maximum catalog tolerance) = 0.18 mm (maximum admissible clearance)
For optimum working conditions, energy-saving and longer heater life, it is advisable to bore holes with a tolerance of H7.