Philips HPI/T 400W Third Generation
This lamp represents a notable improvement beyond its 2nd generation predecessor, due to the addition of a hydrogen getter in the outer bulb. Hydrogen is evolved in MH lamps as traces of water vapour emerge from the quartz, this being cracked in contact with hot metal parts to form the oxide and free hydrogen. Hydrogen molecules are small enough to diffuse through the quartz into the arc tube, where they lead to an increase of the arc re-ignition voltage on each half cycle of the mains, and as a result a reduction in lamp life.

The original Philips getter takes the form of small pellets pressed from zirconium and nickel powder. These are fragile and must be protected from incident light, so they are enclosed in small pockets pressed into a folded metal strip. The strip, containing four pills, is welded to the frame near the dome end of the lamp where it reaches approximately 250°C - hot enough to sorb hydrogen and cool enough that it does not react with the nitrogen outer gas filling.

The arc tube is filled sodium, indium and thallium iodides and the flat-ended shape with end pockets ensures uniform halide temperatures and minimal colour variation. It is filled with neon-argon for easy ignition, the outer containing the same partial pressure of neon to avoiding loss of this gas from the arc tube. The close-up photo of the arc tube seal reveals a curious residue of the early HPI exhaust process, in which small tubes of quartz were melted over the lead wire to protect the seal during furnacing of the arc tube for 40 hours at 1030°C to bake out impurities - after which arc tubes were opened, refilled with clean gas and finally tipped off. A steatite tube over the frame beside the arc tube serves to reduce sodium loss by the photochemical effect.
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: Not published
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: June 1981 Date Code 1F
Original / Present Value:
 
References: 1) Philips Metal Halide Gas-discharge Lamps Brochure, 1009 448 00011, December 1981.
2) Philips UK Comprehensive Catalogue, PL8158, 1980.
3) "The Iodide Discharge Lamp", L.B. Beijer, C.A.J. Jacobs & T. Tol, Philips Technical Review 1968 V.29 No.12 pp.353-362
4) Philips Training Manual MTO Turnhoutlampen - Metaalhalogenidelampen, F. Oostvogels, D. v.Pijkeren & G. Rouweler, 1985.