1984 ЕЭЛЗ ДНаТ 400-4 (EÈLZ DNaT 400-4)

The invention of the high-pressure sodium lamp by General Electric of America in the early 1960s was such a breakthrough that it forced all major lamp manufacturers to quickly develop their own variant of the technology in order to secure their place in a changed lighting market. In many cases this process started via the licensing of GE's patents on the design of their first Lucalox burner, which consisted of a section of sintered polycrystalline alumina (PCA) tubing frit-sealed to niobium end caps. The situation with the many state-owned lamp manufacturers of the Soviet Union was more a grey area as GE may have shared some of its technology and equipment with some of them, as part of a global trade agreement between the USA and the USSR, while others developed their own sodium lamps based on GE's published works alone (articles and patents) without any formal licenses. In any case, this resulted in most of the first high-pressure sodium lamps released by Soviet manufacturers looking like GE's early Lucalox lamps.

Such is the case of the sodium lamps made at the Yerevan electric lamp factory (ЕЭЛЗ) in the then Armenian Soviet Socialist Republic. Development work on ceramic burners there began in the late 1970s under the direction of Benjamin Tumasyan (Бениамин Тумасян) who was the company’s chairman from 1974 to 1993. Because of a limited capacity for further development, the overall design of their sodium lamps remained strikingly similar to that GE’s first Lucalox, including its clear elliptical bulb provided with a support dimple. The 1984 DNaT 400-4 shown here is of the fourth generation produced by the Armenians but still features a burner sealed with niobium end caps provided with symmetrical tubular sodium-mercury amalgam reservoirs for an operation at all positions. GE phased out this particular design in 1969 due to reliability issues. Another characteristic of early PCA burners, the ceramic material used in the DNaT 400-4 is much more opaque than that produced in the West at the time. Poor material quality and the lack of optimization of production processes caused a high density of defects and impurities in the resulting ceramic material, a hallmark of Soviet-made high-pressure sodium burners.

ЕЭЛЗ eventually upgraded its sodium lamps to a more modern construction still related to GE Lucalox lamps, but of later designs. In their fifth-generation DNaT 400 released in 1985, the Amernians used an improved burner featuring a compound seal design consisting of PCA plugs, a wire seal at one end and an external amalgam reservoir at the other end. Such arctube construction was introduced eight years earlier in the West by GE, with tts third-gen Lucalox lamps.