MA/V Medium Pressure Mercury Discharge

Although Crompton is traditionally thought of as an incandescent lamp manufacturer, the company was quite innovative in both mercury and fluorescent lamp manufacture in the 1950's and 1960's.

Crompton's MA lamp was technologically unique and it survived in the fiercely competitive mercury lamp business by patenting its novel lamp construction technique. MA arc tubes do not require thermal insulation as do sodium lamps, all that is required is a stationary layer of gas since draughts can cause variations in light output by affecting the arc tube temperature. Whereas competitors went to the expense of sealing arc tubes into an outer bulb filled with carbon dioxide or nitrogen gas, Crompton was the first to adopt a low-cost air filled open design.

The Crompton arc tube is manufactured from Aluminosilicate glass sourced from GEC glassworks, and fabricated in the same way as an Osram lamp, making use of the efficient pinch-sealing technique and low cost drawn tubing rather than expensive hand-blown arc tube inners. A flared glass tube is fused into the dome of the outer bulb, and the arc tube is mounted between this flare and a similar double-ended flare to which the outer bulb is drop-sealed. Asbestos pads offer cushioning and permit thermal expansion of the arc tube. All that remained was for the outer bulb to be capped, and the slow, expensive exhaust process had been eliminated. However with the introduction of the more efficient Quartz MB type arc tube, this did require an inert atmosphere to protect the high temperature molybdenum seals. Crompton could not compete in this market and ceased mercury production when the MA market dried up.
Manufacturer: Crompton Parkinson Ltd.
Lamp Power: 250 Watts
Lamp Current: 2.15 Amps
Lamp Voltage: 104-145 Volts For 200/250V Mains
Cap Type: E40s/45 Brass + Vitrite
Bulb Finish: Clear Soda-lime soft glass
Bulb Type: T-51 T-16 in eighths/inch
Overall Length: 290 mm 11½ inches
Light Centre Length: 170 mm 6¾ inches
Arc Length: 120mm 4¾ inches
Electrodes: C-6 Open Coil Thoria pellet emitter
Atmosphere: Inner: Hg | Ar (1 atm) Outer: Nitrogen
Luminous Flux: Not published
Luminous Efficacy: Not published
Colour Temperature & CRI: CCT: 5400K CRI: Ra 6
Chromaticity Co-ordinates: CCx: 0.337 CCy: 0.421
Burning Position: Vertical
Rated Lifetime: Not published
Warm-up & Re-strike Time: 5 minutes 5 minutes
Factory: Guiseley England
Date of Manufacture: June 1959 Date Code: 18
Original & Present Value: Unknown