Metal Halide Lamps
Metal halide lamps provide high light output at relatively high efficiency levels. The lights come in many sizes, shape and types. We also carry Probe Start Metal Halide Lamps which are also commonly known as Pulse Start Metal Halide Lamps. You will not find better service, support and quality from any other Metal Halide supplier anywhere.
Advantages of Metal Halide Light Bulbs
Metal halide lamps provide several unique characteristics. Metal halide lamps have an average life span of 15000 to 20000 hours, which is more than ten times that of the traditional incandescent light bulbs, saving you maintenance costs. Metal Halide bulbs also provide an output that is much closer to natural light than other lamps. This white light produced by MH light bulbs is preferable by a lot of people since it provides better visual acuity, even at low light levels.
The color temperature given off by metal halide lamps has a very wide range – from about 2700 Kelvin to 20000 Kelvin, meaning that almost any color temperature desired can be achieved including blue, green, aqua and pink.
MH lamps offer an excellent color rendering index of 65 – 90 CRI which is more than the average value for most other light sources.
The compact size of metal halide light bulbs means that a high light level is generated from a compact light source, providing smaller, more controllable luminaries. The metal halide lamp is also extremely versatile. It is relatively unaffected by ambient temperature and so can be used for both indoor and outdoor applications. They also come in extensive style and wattage options which allows for many different uses.
Compared to other light sources like fluorescent light bulbs and incandescent bulbs, the metal halide light bulb is very efficient, generating 65 -115 lumens per watt, which make them a cost saving and less wasteful option. However, this is not just about saving money. Widespread use of MH light bulbs will have a positive effect on air quality and the environment in general. This is because lower electrical power generating requirements means less air pollution from power stations and the long life and efficiency of the halide bulb translates to less landfill waste generated.
It is also useful to compare metal halide light bulbs with other types of light sources available. As compared to incandescent lights, a 100-watt halide lamp provides five times the lumen output of a 100-watt incandescent bulb, lasting twenty times longer. The incandescent bulb may have a lower initial cost, but the metal halide bulb has a much lower overall cost over its total life because it is five times more efficient.
Vapor mercury lamps also have a long life but are not nearly as efficient as the metal halide bulbs, producing 35 – 58 lumens per watt compared to the 65 – 115 lumens per watt of the MH bulbs. Mercury Vapor lights are also limited to the blue/green spectrum, having a lower (CRI) color rendering index. The metal halide light bulb provides light that is closer to sunlight than any other high intensity discharge (HID) light source.
High pressure sodium (HPS) lamps are another type of HID light which have a long life. However, they do not provide the same light quality as metal halide light bulbs because they only give off the strong yellow light of the spectrum, which is about 2200 Kelvin due to their sodium content. The color rendering index of HPS lights is also very poor at about 20 -25 CRI. Metal halide lamps on the other hand provide the full spectrum of light with a much higher CRI.
Fluorescent light bulbs are usually much longer and thus can be less directed than metal halide bulbs which are compact and easily controllable as earlier mentioned. A single 100-watt halide bulb will provide the same light as three 48 inch high output fluorescent lamps. Fluorescent lamps are often limited in the temperature range in which they can perform, performing optimally in indoor applications at about 77 degrees Fahrenheit, and this degrades as the temperature varies. Metal halide bulbs are able to tolerate a wider range of operating temperature conditions.
Halide light bulbs can be applied in a wide range of areas, used both for general industrial purposes and for specific applications requiring a specific UV or blue-frequency light. A common use is for indoor gardening since they produce the spectrum and temperature of light which encourages plant growth. They are also used in athletic facilities like gyms and squash courts, and also popular with reef aquarists who need high intensity light for their corals. MH lamps also have widespread use in high end professional lighting fixtures, especially in intelligent lighting where they are commonly known as MSD lights. In these applications they are used in 150-, 250-, 575-, and 1200-watt ratings.
All MH bulbs require ballasts with which regulate the current flowing through the arc of the lamp and deliver the right voltage to the arc. The most common are the electrical ballasts. The probe start metal halide bulbs contain a starting electrode in the light bulb which initiates the arc when turned on, generating a slight flicker in the process. Pulse start metal halide light bulbs use a special starting circuit known as the igniter to generate a high voltage pulse to the operating electrodes. The American national Standards Institute (ANSI) has established parameters for all halide bulbs except for some newer products.
There are a few electronic ballasts available now for MH light bulbs. These offer more precise management of the lamp’s wattage, providing more consistent color and a longer life. Electronic ballasts are also known to increase the efficiency, or in other words, reduce the electrical usage of the halide bulb. Although, high frequency operations may not necessarily increase the light’s efficiency (as with high output or very high output fluorescent bulbs), it may allow for specially designed dimming metal halide ballast systems.
MH bulbs were hitherto preferred to mercury vapor lights in uses where a more natural light was required because of the whiter light produced by mercury vapor lights. The differences are not as great today with some Metal Halide bulbs providing very white light with a color rendering of up to 80 CRI. Specialized metal halide mixtures are now available which can have a color temperature of as low as 3000 Kelvin, which is very yellow; to as high as 20000 Kelvin, which is very blue. Some of these specializations are targeted for use by indoor gardeners for their growing plants; and for use in indoor aquariums to benefit animals.
Because of tolerances in the manufacturing process, color temperature can vary slightly between lights such that the color properties of metal halide lamps cannot be predicted with 100 percent accuracy. The standards set by ANSI specify that the color specification of metal halide bulbs can only be measured after the bulb might have been seasoned (or burned) for 100 hours. With probe start MH bulbs, a color temperature variance of, give-or-take 300 Kelvin may be recorded, while with the newer pulse start technology, the variance observed is less.
The color temperature of a metal halide bulb may also be affected by the electrical system which is powering it. An underpowered halide bulb will have a color temperature closer to that given off by mercury vapor lights. This is because the temperature of the light will be cooler and as such the halide salts, which are responsible for the warmer reds and yellows, will not reach complete vaporization and ionization. The more easily ionized mercury will then dominate, resulting in a cooler, bluer output. With an overpowered halide bulb, the reverse will be the case, but this condition is not desirable and is potentially dangerous as it could lead to arc-tuber rupture. The color properties of metal halide light bulbs may change over their lifetime and it can be noticed that where there is a large installation of MH bulbs, no two will be exactly the same color.
When a metal halide light bulb is started at below its operating temperature, it cannot begin providing light at its full capacity. This is because the temperature and pressure within the inner arc require time to reach full operating levels. This may take a few seconds, and even up to five minutes, depending on the type of lamp. As the various metal halides vaporize in the arc chamber, the MH lamp will exhibit different colors.
The MH bulb’s arc will go out if power is interrupted however briefly, and the high pressure within the hot arc tube will prevent re-striking of the arc. Because a cool-down period of five to ten minutes is required to restart the halide bulb, it is a major concern where prolonged lighting interruption could create process shut-downs or safety issues. However, some few metal halide bulbs have an instant re-strike capability in which the lamp, ballast and socket are built to withstand the 30000 volts required to re-ignite the lamp via a separate anode wire.
When metal halide light bulbs reach the end of their life, they display a phenomenon known as cycling in which the light glows for a while and the goes out, repeatedly. The cause of this is that when the lamps are old, the voltage required to maintain the arc exceeds the voltage provided by the ballast. When the halide bulb heats up to the point where the maintaining voltage is higher than that provided by the ballast, the arc fails and the light goes out. Some more sophisticated ballast designs recognize cycling and do not attempt to restart the best metal halide bulb after a few attempts. This phenomenon is what is commonly seen in your neighborhood when a street light turns off, and back on again, after it has cooled.
There are some dangers and other effects in the use of metal halide lamps in relation to humans. Some people have noticed a temporary blurring of vision after very brief close range exposure to metal halide lighting which could be linked to Photokeratitis, or snow blindness – a result of unprotected exposure to ultraviolet radiation.
MH lamps using a quartz arc tube are also susceptible to explosion at the end of life as the corrosive effects of the halide salts degrade the quartz over its life. A universal position halide bulb which is mounted horizontally also has an increased risk of explosion because of higher arc wall temperatures. Mechanical shock and leaving the MH bulb on all day are other situations which may cause explosion. To remedy these, an MH bulb should be turned of for at least 15 minutes each week and a quartz shroud may be used for added protection, and also to reduce ions escaping through the arc tube wall in the case of quartz metal halide light bulbs.
