Difference between revisions of "Philips ML"

Standard High Pressure Mercury Lamp for general lighting with 50W, 80W, 125W (E27 base) and 125W, 250W, 400W, 700W, 1000W (E40 base)

*E27 base or E40 base (requires matching ballast)

*Soft glass (100, 160 and 250W) or Hard glass (250 and 500W)

All the above particular operating issues make the lamp slightly inconvenient to operate, even if the lamp itself is highly attractive to use and install and not an expensive purchase.

The only slight drawbacks are the lamp's sensitivity to positioning and operating voltage, along with slightly lower than average service life, especially compared with modern lighting technology. The lamp's low efficiency is caused by the compromise of its internal construction. The warm light generated by the internal filament also comes with massive heat radiation, which is similar to typical tungsten lamps that were previously popular.  

The pleasant light is suited both as general lighting in homes as well as gardens or workshops. A good selection of lamps can be used if power consumption is not critical and a specific scene or effect is desirable. Unfortunately, especially in small spaces, the lamp can contribute to heating, which may be advantageous as well as undesirable, depending on application. Special care should be taken when cleaning the lamp as vibrations, dirt accumulation and improper handling can easily crack the bulb, especially on soft glass lamps. Any dirt present on the lamp may be trapped longer due to melting and subsequent adhesion to glass. This means that lamp cleaning has to be as thorough and careful as on old tungsten lamps.

This type of mercury vapour lamps were popular mostly before the oil crisis that occured in the 1970s. Many years have passed since use of this lamp was basically non existant, meaning that stocks are not very large. Although the lamp could directly replace even less efficient tungsten or incandescent lamps, this market very rapidly diminished as soon as compact flourescent lamps with screw bases were made available. These had a much longer life, had no restriction on mounting, were highly energy efficient and had even better colour reproduction. There were few fixtures specifically designed for Philips ML lamps. They could operate on typical high pressure mercury vapour fixture but this was uncommon. There was a market for street-lighting in France, many decades ago, as the lamp offered a pleasant light and energy was quite cheap. Due to the lamp operating restrictions as well as simple use, free standing or hanging mounting were quite common, even if lighting efficiency was diminished.

HPL-N lamps are high pressure mercury vapour lamps that have been produced, with somewhat similar properties, since the 1950s. The lamp's fluorescent coating technology dates back to around the end of 1930s while modern lamps were essentially manufactured as early as 1970s and are a result of subsequent improvements up until that time. The market for these lamps grew as industry and commercial activity recovered after the Second World War, meaning that research was justified by large sales.  

The lamp technology was an improvement of previous lamps that used a clear envelope and had an alumino-silicate glass where the mercury discharge was constrained. Colour reproduction was nonexistent, being so low as to render people and everything natural around them as being dead. Increasing the pressure and temperature of the mercury vapour gas discharge to emit more useful light and operation in any position was possible only with the advent of quartz discharge tubes. Colour reproduction was only slightly improved but lower wattage lamps were much more efficient. Up until late in production, the clear lamp was avoided except for street lighting and some industrial applications. Subsequently, mercury vapour lamps were heavily used in street lighting and industry. Colour rendering was the highest barrier to market success. Improvements focused on colour reproduction but energy efficiency and reliability increases were areas with best results.

Development of fluorescent coatings that emit red light made the lamp more desirable although good flourescent powders were mass produced and cheap only in late 1970s. The lamps itself were running hot so fluorescent powders had to withstand temperature and UV-C exposure stress for many years while also emitting more light than the coating powder absorbed. The first generation powders had mild colour improvements but Yttrium Vanadate ones were highly successful and durable, making the lamp suited even for some indoor illumination, especially for deluxe lamps. Near the end of production deluxe lamps were very common and standard lamps such as the HPL-N were incorporating most developments specific to these top-of-the-line lamps. These improvements made high pressure mercury vapour lamps suited for industrial, commercial, street-lighting and even some occasional residential use.

 

The energy crisis meant that clients demanded improvements and they were focused on improving these lamps, giving rise to derivatives such as metal-hallide lamps, with much better colour reproduction and lower energy consumption. Sodium lamps were improved, culminating in the high-pressure sodium lamps that, with their yellow-orange or golden glow, dominated exterior lighting. By late 1980s mercury vapour lamps where on a market share decline that lasted more than 25 years. This can be attributed mostly to inertia in replacing fixtures that had a lifetime of around 15 years because new installations were not done after mid 1990s due to availability of compact or linear fluorescent lamps.

 

These lamps were not intended for home or office use and they were seldomly used as such. Tungsten lamps had perfect colour reproduction and electric energy costs were very low. Even after the oil crisis of the early 1970s, tungsten lamps were still cheap enough and convenient to be used for general lighting. Also, these lamps did no require any gear.

Philips has been releasing lamps for many decades. Lamps produced in the 70s and early 80s are probably not commonly found today. In the 90s and early 2000 Philips was manufacturing lamps in Holland and other countries, while in the last years they were doing the same thing in China. Quality was not severely affected as, realistically speaking, there were some occasional lamp defects even in their Holland produced lamps due to average manufacturing quality. It should be noted that mercury vapour lamps were mass manufactured and considered low-cost products, meaning that quality was not paramount.

Until the manufacturing plants move to China, there were small differences in this product line as the 90s and early 2000s was using the same technology. Chinese built lamps have some slight improvements that leave some aspects to be desired as well. The internal coating is thinner and has a different grain size with a potentially different powder mix, improving colour rendering more than what the datasheet suggests. Lamp lumen maintenance and uniformity is improved due to a thinner coating that degrades slower and more uniformly. However, the lamp light looks whitish-green rather than whitish-purple, which might be unpleasant for some persons.

Products manufactured by Philips were similar to General Electric but with a quality and consistency much above some East-European manufacturers in terms of colour rendering, light output and life. However, Philips was manufacturing lamps with shorter lifetimes and poorer internal coatings than Osram ones, even if some values specified in datasheets might not suggest much. These differences were maintained until the end of mercury vapour lamp production in the late 2010s. This Philips-Osram lamp difference must be experienced in person. On the other side, Philips lamps were much more popular and are easier to find.