Reference Manual for Lamp Heating

1.	Overview of lamp heating
2.	Selection of lamp heating device
3.	Appropriate usage method
4.	Safety precautions (Important)
5.	Condensed light diameter (width)
6.	Halogen lamp characteristics
7.	Light condensing spot type lamp heater (halogen spot heater)		HSH type
8.	Light condensing line type lamp heater (halogen line heater)		Introduction to LHW type, LHA type and NIL type products
9.	Proposal of cavity heating method (high-efficiency, and high temperature uniform heating)
10.	Light absorption rate of various substances		Physical property data

1. Overview of lamp heating

The lamp heating method of Fintech uses a concave mirror to condense the light from a halogen lamp and a high temperature is obtained. Classified as light condensing spot and line type lamp heaters based on the shape of the condensed light. The wavelength of light from a halogen lamp ranges from 0.4 µm to 2.5 µm range with a peak of approximately 1 µm (visible light to near infrared range). The following are the features when the halogen lamp system is compared to other lamp heating systems.

Summarizing the above, the advantages of lamp heating using a halogen is as given below:

1. The conversion efficiency to radiant energy is extremely high

2. The temperature of the heater itself rises extremely fast (approximately 1 second)

3. Low cost (initial and running costs)

4. Can heat to a high temperature (1832°F (1000°C) or more)

5. Heating through glass is possible

The above are the important points. The following are the other features in addition to the above.

6. The absorptivity is better than far-infrared heater with respect to metals. There are some that are not good for nonmetals too (difference is high). Reference data Emissivity of various materials (absorptivity).

7. Penetrates relatively deep inside semi-transparent bodies (skin, paint, and adhesive), and also heats from the inside.

8. Dust and gases are not generated because quartz glass is used in the product and can also be used in clean rooms. (However, the lead wires and tip processing have to comply with the “Clean room specifications”, therefore normal halogen heaters cannot be used for clean rooms.)

9. Relatively safe heating device with respect to the human body. The device is a high pressure lamp manufactured from glass and must be handled with care. There is risk of blindness when lasers are used especially such as visible-light lasers and far infrared rays. Xenon lamp is a high pressure sealed lamp exceeding that of halogen lamp by 5 times or more, and the risk of rupture is high, furthermore the ultraviolet rays are extremely strong. Also, a high voltage exceeding several thousands of volts is used during startup.

2. Selection of lamp heating device

Light condensing spot type (spot heater)

When you want to heat with a point or heat a circular area, select “Light condensing spot type (spot heater)”. Designing the required light distribution is relatively easy by controlling the mirror curve in case of light condensing spot type. However, there may be cases where the required distribution cannot be achieved, please consult with Fintech. Maintaining a short radiation distance (from the mirror opening end to the irradiated object) is advantageous both when condensing to a single point and when heating a circle --> In case of light condensing spot type, there is less loss of light energy, the condensed light diameter is smaller, and a higher temperature can be obtained. Light condensing spot type (spot heater) is prepared with a NC lathe, and even special order products can be manufactured at a comparatively cheaper cost. Even then, the cost will be 1.5 to 2 times that of standard products.

Light condensing line type (Line heater)

When heating is required along a line or a wide strip, select “Light condensing line type (Line heater)”. Only the width direction of the condensed light can be controlled by the mirror curve, and the mirror cannot be used to control the length direction in case of light condensing line type If uniform heating length is required in the length direction, the line heater must be sufficiently longer than the required uniform heating length. The uniform heating width can be increased by controlling the emission pattern of the lamp, but the design and production work are both difficult. Shorter the irradiation distance, more will be the range which can be heated uniformly, therefore short irradiation distance is advantageous. If the distance very long, the radiation intensity will damped by almost (COSθ)^2 depending on the angle of deviation from the center. When objects on a conveyor have to be heated uniformly, a good method is to use a line heater for heating the whole object and a line heater for heating only the ends. The temperature at the edges is likely to be lower when only the line heater is used for heating the whole object, and to obtain a uniform temperature for the entire conveyor the output of the line heater used for heating only the edges is adjusted. Extruded aluminum is used as the mirror for standard light condensing line type. The custom-made mirror other than the standard are expensive as they are machined using milling machines.

Aluminum and gold-plated mirrors comparison

The body of both the light condensing spot and line types are made from aluminum. Aluminum mirror is obtained by polishing the aluminum to a mirror finished surface. The reflectance of aluminum mirrors as shown in the figure below is a little less than 90% for the radiation of a halogen lamp, and is less than that of gold plated mirrors, which will be described later. Also, the reflectance is slightly reduced due to oxidization when used over a long period of time. However, the additional advantage in case of aluminum mirrors is that the mirrors can be easily re-polished by the users. The gold plated mirror reflects the radiant energy of the halogen lamps efficiently, and is the best mirror for this purpose. However, if there is staining by substances that evaporate from the object which is heated, the gold-plating may get peeled-off depending on the type of dirt. In such cases, the gold plating cannot be repaired, and has to be re-plated, the cost for which is approximately 10,000 yen for 15.5 inch2 (100 cm²). Therefore, please take maximum precautions to ensure that the gold-plated mirror does not get dirty. The gold plated mirror can withstand long-term use as long as it does not get dirty. The decrease in reflectivity is also very less. Provide a glass window between the mirror and the object as a measure to prevent the mirror from getting dirty. Ensure that the glass window can be cleaned easily when it gets dirty. Quartz glass is suitable to be used as the glass material. However quartz is expensive, and Pyrex glass (brand name. Other equivalent products such as TEMPAX) is used as an alternative in many cases. The models of Fintech which come with the window glass as a standard feature are the small-diameter SH-35 with quartz glass and HSH-60 with Pyrex or TEMPAX. HSH-120 and HSH-160 are optional in which quartz glass is used. The methods other than the above used are blowing clean air into the mirror to maintain a positive pressure inside the mirror which is an effective method. However, there will be no effect in this case unless a certain degree of sealed structure is maintained inside the mirror, and hence this method is generally used as auxiliary method for the window glass system.

3. Appropriate usage method

Summary

The lamp heating device that uses a halogen is basically a halogen lamp, the usage method and precautions are the same as that of halogen lamps and its mounting device. The brightness can be controlled from 0% to 100% by just controlling the voltage in the same way as a general halogen lamp luminaire. However, the device output (power) is relatively large compared to the size of the instrument and leads to cooling problems. Water cooling or forced air cooling is used for lamp heating devices having high output.

Measures for inrush current

If a high voltage is suddenly applied to the halogen lamp, inrush current which is more than five times that of the initial current will flow, and adversely effects the halogen lamp. The larger the current value of the lamp, the more pronounced will be the effect. Definitely for lamps of more than 10 A!, even in the case of lamps with lower current value, try to use the power supply with a soft-start of more than 1 second. "Measurement data of the inrush current The circuit breaker may be activated due to the inrush current depending on the power supply and the current may not be supplied in some cases." The models with overcurrent protection based on “Fold back shaped characteristics” which is sometimes seen in the protection circuits of DC power supply cannot be used as a power supply source for the halogen lamp. If the protection is based on “Drooping characteristics”, then such models can be used. However, check and confirm with the power supply manufacturer. Since most of the high powered halogen lamps (over 300 W) use AC power supply, usually the supplied power is controlled by phase control (sinusoidal control). Since soft-start function can be incorporated easily for the thyristor controller and is provided as standard accessory except in the basic models.

Precautions to be taken for extending the service life

As far as possible, do not apply voltages exceeding the rated voltage. Doing so may cause disconnection, blackening, or rupture. Using the lamp at low voltage in the range that satisfies the heating requirements will be advantageous for the lamp service life. A 10% voltage drop increases the service life by 3 times. AC power supply is safe. However, for models below 24 V even DC is okay. When using AC, trying to obtain the appropriate voltage using phase control (thyristor control) from a voltage that is higher than the rated voltage is dangerous. In this case, a high voltage will be applied momentarily even though the effective value is below the rated voltage, this may cause a breakdown of the lamp leading to disconnection or rupture. The correct usage method is to use the AC power supply of the rated voltage and then reduce the voltage with phase control (thyristor control). As much as possible ensure that the body and halogen lamp are subject to minimum vibrations and shocks. In case of severe shock, the glass may crack or the filament may get cut immediately. However, even if these abnormalities cannot be seen clearly, damage may be caused to the filament which may remain leading to a decrease in service life. There is no restriction on the lighting direction for light condensing spot type. However, basically the light condensing line type must be used horizontally. This is due to the structural features of the halogen lamp used in this heater. However, halogen lamp that supports vertical lighting can be designed and manufactured, please consult with Fintech.

Information on cooling the heaters

Ensure that 0.13 gal/min (0.5 L/min) of water flows for each 1 kW of lamp power for the models requiring water cooling. 0.26 gal/min (1 L/min) or more for heaters of 2 kW. The water temperature will increase by approximately 10ºC at this time. If possible, ensure that the flow rate is 2 times the minimum flow rate. Also, preferably provide an interlock to switch OFF the power supply of the lamp when the flow of water stops. The water cooling type has been designed and manufactured assuming that the water pressure in the usage environment will be below 29.00 psi (200 kPa (approximately 2 kgf/cm²)). If the water pressure is expected to cross 43.51 psi (300 kPa), please consult with Fintech. The thermal energy generated from the mirror is approximately 1/3 of the power supplied in most of the lamp heating devices. In other words, heat dissipation of approximately 1/3 the power supply is required, this can be achieved with natural cooling in case of heaters of smaller power, but when the heating device is compact with a large power, forced air cooling is required. Condensation can be a problem if the water temperature is very low compared to the ambient temperature when cooling water such as groundwater is used. In case of severe condensation, there is a risk of leakage and the reflectivity of the mirror may also be affected. In such a case, the water has to be passed through a long copper tube so that the difference with the ambient temperature is reduced and then supplied to the heater, take measures such as stopping the cooling water when current is not passing, and keeping the flow quantity to the minimum required limit even when current is passing. Foreign matter is accumulated in the cooling water channels based on the quality of the cooling water. The aluminum may get corroded and aluminum compounds may accumulate. Clean periodically and maintain the proper flow of water.

Others

Take care not to dirty the lamp when replacing the lamp. Wipe the lamp clean with a cloth moistened with alcohol if the lamp is dirty. Also clean the lamp mounting unit of the mirror body by wiping. If the mounting unit is dirty, the lamp may get dirty during installation. The reflecting mirror surface is the most important part of the heating device, and requires the maximum maintenance. This was also touched upon in the “Selection of lamp heating device” section, the performance will be reduced significantly by adherence of smoke etc., that is generated from the heated object due to evaporation and combustion, to the mirror surface. When heating such objects, provide a protection glass in front of the lamp heating device, and clean and replace the glass periodically. The entry of smoke can be prevented more effectively by blowing in clean air into the space within the mirror and maintaining an internal positive pressure. The lamp has been designed such that the replacement is simple, reproducible and highly accurate. However, if the heating device main unit is disassembled, sometimes the unit cannot be assembled easily. In normal cases, disassembling of the main body is not required, therefore please avoid disassembly. Please contact Fintech when disassembly is absolutely necessary.

4. Safety precautions → The following precautions must be taken to avoid danger to the human body

The main body and the lamp are at extremely high temperatures when the current is passing / has just passed through them, therefore take precautions to prevent burns or fires. Also, the space around the light condensing unit will be at very high temperatures, and the same precautions are required. The risk of rupture for high pressure sealed glass bulbs such as halogen lamps is not zero. A rupture can be very dangerous as quartz glass of high temperature (1112°F (600°C) or more) will be scattered. To avoid this danger, use devices that have been designed and under the conditions which will ensure that there is no fire and danger to the human body even in the event of a rupture, and also add an appropriate fast-acting fuse to the power supply line. Frequent ruptures indicate that, arc discharge takes place inside the lamp once the filament burns out, and the resulting high temperature causes the internal pressure to increase leading to ruptures. Or, the large current due to the aforementioned arc discharge burns the molybdenum foil during which the quartz glass breaks leading to the rupture of the lamp. Therefore, it can be inferred that rupturing of the lamps can occur easily in high voltage lamps where arc discharge take place during filament burn out. Rupture is less in low voltage lamps (24 V or less). However, take sufficient precautions as rupture is not zero. The light of halogen lamps based on its characteristics contains trace amounts of ultraviolet rays that are harmful to the human body (approximately one-tenth of sunlight) and precautions must be taken in case of irradiation for long periods of time and with high illuminance. Also, UV filter may be required in some heating applications such as UV-curable resin. Even if it is not ultraviolet rays, intense light is harmful to the eyes. Protect your eyes using dark sunglasses to view the filament and condensing unit of the spot heater when the lamp is lit up. Do not wet the lamp heating device (HSH, and LHW). Also, ground the main body for safety. Check and make sure that the power supply is turned OFF when replacing the lamp.

5. Condensed light diameter (width)

The following are the relationships of the condensed light diameter when the irradiation diameter of the condensing type lamp heater has been focused to the maximum.

1. The condensed light diameter changes almost inversely proportional to the aperture. Larger the mirror opening diameter, smaller will be the light diameter and a higher temperature will be obtained.

2. The condensed light diameter changes almost proportionally to the focal length (irradiation distance). Shorter the focal length, smaller will be the light diameter and a higher temperature will be obtained. 3. The condensed light diameter is almost proportional to the light source size. The filament diameter of the lamp is almost proportional to the square root of the power. Larger the light source (power is large), larger will be the irradiation diameter. In other words, if a halogen lamp of higher power is used, the irradiation diameter increases and the power density does not change. The following figure shows the method for practical calculations based on these relationships. Scientifically, this an inaccurate method.

The above calculation can be used when small hot spots is required by focusing the light energy. Consider that the focal point diameter mentioned here, as the range which has almost the same temperature as the center. There are various definitions for the focal point diameter, if the definition is “The range in which the irradiation intensity is 1/2 that of the central portion”, then the focus diameter will be more than twice the above calculation result. Also, this is not true when f is extremely short. Consider that the focal point spot diameter will be roughly the size of the light source in case of mirrors with a short focal length (focal length is approximately half the aperture). A larger area can be heated by moving back and forth from the focal position. This can also be achieved by special design and manufacturing, but try and check if the requirement can be met by shifting from the focal position due to issues of cost and delivery date. The following shows the change in the irradiation diameter and irradiation pattern when the irradiation distance is changed.

“Irradiation at a distance of 0.39 in (10 mm) with a model of f = 15 The distribution is almost equal and the irradiation diameter is increasing.	“Irradiation at a distance of 0.59 in (15 mm) with a model of f = 15 The light beam is focused to the maximum since it is the focal position.” High temperature is obtained.
"Irradiation at a distance of 0.78 in (20 mm) with a model of f = 15 The irradiation diameter is increasing, but the central portion is slightly stronger.”	"Irradiation at a distance of 1.18 in (30 mm) with a model of f = 15 The irradiation diameter has increased and the irradiation is almost uniform.”
"The above was in the case of the light condensing spot type (spot heater), and the same also applies for the light condensing line type (line heater) → Refer to the photographs below The condensed light width increases when moved in any direction from the focal position, the light distribution along the length direction will continue to become longer as the separation distance increases (when the distance is sufficiently separated, the increase is nearly in proportion to the distance).”

"Irradiation at a distance of 0.47 in (12 mm) with a model of f = 20 The central portion is slightly dark, but the irradiation is wider.”	"Irradiation at a distance of 0.55 in (14 mm) with a model of f = 20 The distribution is almost uniform and the irradiation width is wider.”
"Irradiation at a distance of 0.78 in (20 mm) with a model of f = 20 Focused to the narrowest as the position is the focal position.”	“Irradiation at a distance of 0.55 in (30mm) with a model of f = 20 The distribution is almost uniform and the irradiation width is wider.”

6. ogenogen lamp characteristics

Various characteristics of the halogen lamp changes when the voltage is changed. The major change is to the service life, the service life increases by 3 times when the voltage is decreased by 10%. The lamp service life is mainly determined by the temperature of the filament (color temperature). The service life is approximately 1000 hours at 3000 K, and 200 to 300 hours at 3200 K. The calculated service life will be very high when the temperature is significantly lower than 3000 K, but even if the calculated service life of the filament is long, the service life of the lamp may not be as calculated due to various factors. As a thumb rule, the values are 5000 hours at 2600 K and 20,000 hours at 2200 K. The filament temperature is not the only factor limiting the lamp service life. If the temperature of the seal is high, this will be the factor that determines the lamp life (see the figure below). When the lamp service life is 2000 hours and the seal temperature is 662°F (350°C) or less, then the heat resistance of the seal will not be a limiting factor for the service life. When the temperature is 662°F (350°C) or more, the seal will rupture within 2000 hours and cannot be used.