HQI-BT Tubular Metal Halide

HQI lamps from Osram are metal halide sources designed for operation on ballasts for high pressure sodium lamps. No third auxiliary starting electrode is employed, nor is there any other starting aid, so a high voltage ignitor is required. The lamps can be run on mercury gear at reduced performance.

The arc tube in Osram lamps is formed from three pieces of quartz tubing, consisting of a central large diameter portion with conical end chambers forming the discharge vessel, with a narrow diameter piece of tubing being fused to each end to allow slim pinch-seals to be made. This creates an arc tube shape whose cold spot temperature is higher, leading to better efficacy and colour rendering. The reduced mass of quartz also means it is capable of running up to full temperature, and cooling down to re-striking temperatures more rapidly than traditional one-piece pinched arc tubes.

This is a daylight colour lamp with higher colour temperature than the standard types. Dysprosium and thallium iodides are the principal metal halide constituents, this chemistry causing the arc to become very constricted which leads to instability and a chance of flicker. Caesium iodide is therefore added to counter this effect and fatten the arc back to normal levels.

The luminous efficacy is somewhat less than for lower colour temperature lamps, consequently the short arc in this lamp develops considerably more heat. The arc tube is therefore enclosed in a vacuum atmosphere to minimise effects of heat transfer to the outer jacket. In early designs of the 400W daylight lamp this sometimes caused the tubular outer bulb to reach softening temperatures and suck-in when used horizontally. This post-1999 bulged shape solved the issue.
Manufacturer: Osram GmbH
Lamp Power: 420 Watts (SON ballast) 360 Watts (MB ballast)
Lamp Current: 4.0 Amps (SON ballast) 3.5 Amps (MB ballast)
Lamp Voltage: 100 Volts (SON ballast) 130 Volts (MB ballast)
Cap: E40s/45 nickel plated
Bulb Finish: Clear borosilicate
Bulb Type: BST-62
Overall Length: 285 mm
Light Centre Length: 127 mm
Electrodes: Thoriated tungsten
Inner / Outer Atmosphere: Ar | Hg (Dy,Th,Cs)Ix Outer: Hard vacuum
Luminous Flux (100 hrs): 32,000lm (SON ballast) 25,000lm (MB ballast)
Luminous Efficacy (100 hrs): 76 lm/W (SON ballast) 69 lm/W (MB ballast)
Colour Temperature 5200K (SON ballast) 6100K (MB ballast)
Colour Rendering: Ra >90
Burning Position: Universal
Rated Life: 6,000 hours (to 50% survival)
Warm Up / Re-strike Time: 4 minutes 10 minutes max.
Factory: Spandau, Berlin, Germany
Date of Manufacture: February 2001
Original / Present Value:
References: 1) Osram Lichtprogramm 2002.