Philips HPI/T 400W 4th Generation
This lamp represents a small improvement beyond its 3rd generation predecessor. The sodium-indium-thallium chemistry of Philips HPI lamps is particularly sensitive to contamination, and special measures for cleanliness have to be taken during production. The problems were exacerbated during the early years when Philips used to produce its own metal halide pellets for dosing the arc tube, their purity being less than desirable.

After dosing the arc tubes with halides and gas, they were tipped-off with long exhaust tubes and furnaced at just over 1000°C for 40 hours to bake out the impurities. The long exhaust tubes were then re-opened, the impurities pumped out and replaced with fresh gas, and the arc tubes sealed-off with the final short tips. To protect the delicate molybdenum foil arc tube seals from oxidation during furnacing, small quartz tubes used to be melted over the seals, evacuated, and afterwards cracked off. Needless to say the process was labour intensive, a small army of glassblowers being employed to keep up with production. That expensive process was finally eliminated in the mid-1980s with the development of the cassette-oven process, in which each arc tube is placed into a small sealed container before furnacing. This lamp is notable for the absence of the remnants of quartz tubing over its end seals.

The illuminated photograph shows that colour demixing in this lamp has been improved vs earlier generations when burned vertically, however it is still rated only for horizontal operation. The optical quality and chemical purity of the quartz tubing is also much better, with almost no airlines being visible.
Manufacturer: NV Philips Gloeilampenfabrieken
Lamp Power: 390 Watts
Lamp Current: 3.4 Amps
Lamp Voltage: 125 Volts 700V Ignition
Cap Type: E40s/45 Ni plated brass + porcelain
Bulb Type: T-46 T-16 in eighths/inch
Bulb Finish: Clear Borosilicate glass
Electrodes: Double Coil Tungsten Radioactive ThO2 emitter
Arc Length: 41.5 mm 1 5/8 inches
Atmosphere: (Na,In,Tl)Ix, Hg | Ne-0.5%Ar Outer: Ne-40%N2
Luminous Flux: 31,500 lm (@ 100hrs) 29,200 lm (@ 2000hrs)
Luminous Efficacy: 80.7 lm/W (@ 100hrs) 74.9 lm/W (@ 100hrs)
Colour Temperature & CRI: CCT: 4500K CRI: Ra 65
Chromaticity Co-ordinates: CCx: 0.377 CCy: 0.386
Rated Lifetime: 6000 hours 70% survival, 75% flux
Warm-up & Re-strike time: 3 minutes 5 minutes
Burning Position: Horizontal ± 20°
Overall Length: 275 ± 8 mm 11 inches
Light Centre Length: 175 ± 8 mm 7 inches
Factory: Turnhout Belgium
Date of Manufacture: November 1986 Date Code L6
Original / Present Value:
 
References: 1) Philips Metal Halide Gas-discharge Lamps Brochure, 1009 448 00011, April 1986.
2) Philips UK Comprehensive Catalogue, 1985.
3) Philips Training Manual MTO Turnhoutlampen - Metaalhalogenidelampen, F. Oostvogels, D. v.Pijkeren & G. Rouweler, 1985.