Lighthouse Halogen BSL/3H

Following the obsolescence of the L/3 Lighthouse lamp, the author website was contacted by Trinity House Lighthouse Corporation with a request to develop a modern alternative - the result of which is illustrated on this page.

Previous experiments had been carried out with a cluster of four 24V 50W halogen capsules, type RJY5024AX made by Radium Germany. It was found that the space required for the lampholders limited the proximity with which they could be brought together, and the concentrated heat caused the quartz pinch-seals to exceed their limit of 350°C and fail.

The oxidation problem was solved by sealing the capsules into a nitrogen-filled glass bulb. The dimensional restriction was overcome by spot-welding the pins of the capsules directly to a metallic support frame, which resulted in an increased efficiency of the optical system and a much brighter signal approaching that of the original single-filament L/3 lamps. In the later design lamps such as this example, the support frame is made from braided nickel wire so as to avoid high stresses being placed on the quartz pinch-seals of the capsule and reduce the risk of breakage during thermal cycling. A dimple was also added to the bulb crown to support a central metal rod welded to the mount assembly, to reduce problems of breakage during transport.

A small series of these lamps, classified as type L/3H (Halogen) was produced by the author with assistance of the Glassblower at the University of Bath. These proved satisfactory in keeping a number of smaller lighthouses operational until they could be redesigned around other more readily available modern light sources.
Manufacturer: Lumalux Lighting
Lamp Power: 200 Watts
Lamp Voltage: 24 Volts
Lamp Current: 8.33 Amperes
Cap Type: P28s/25 Brass & Vitrite
Bulb Type: PD-80 PD-23 in eighths/inch
Bulb Finish: Clear Soda-lime silicate
Filament Type: 4CC-8 Quadruple Axial
Atmosphere: Halogen inner Nitrogen outer
Luminous Flux: 3,400 Lumens
Luminous Efficacy: 17.0 Lumens per Watt
Beam Intensity: N/A
Beam Distribution: N/A
Colour Temperature & CRI: CCT: 3000 Kelvin CRI: Ra 100
Chromaticity Co-ordinates: CCx: 0.452 CCy: 0.409
Rated Lifetime: 2000 hours
Burning Position: Vertical base down
Overall Length:
Light Centre Length: 55.5 mm 23/8 inches
Factory: University of Bath Glass Shop England
Date of Manufacture: April 1996
Original Value: GBP £50.00 (1996)
References: 1) Radium Lamp Catalogue, 1999.