Polam LRF 125W Mercury Discharge

This is an example of one of the older mercury lamps to have beeb produced in Poland by Polam Pabjanice the former state-run lamp manufacturing operation.

It was produced with technology originally exported from Philips in the Netherlands, and technically the construction of the arc tube is fairly similar.

The phosphor coating on this lamp appears to be an interesting blend of two or more standard types. The peaks around 618 and 700nm identify the presence of the standard yttrium vanadate material, but the emission is very weak - some four times less than would be expected. This is most likely due to inferior processing techniques in the phosphor manufacturing method, with either an inferior crystalline structure or the presence of impurities preventing the full quantum efficiency of this phosphor from being realised. Consequently the light output from this lamp would be rather low. Indeed, so low is the vanadate emission that the lamp achieves a red ratio of only 8.2% - a figure of 11% would be normally expected.

Behind the vanadate emission there is a second very broad emission centred around 600nm, and this is suspected to be from an orthophosphate based material blended in with the vanadate. The orthophosphates are useful for raising the luminous efficacy of the lamp but do little to increase colour properties. A pure vanadate coating would do better still, but if the manufacturer was unable to manufacture it to the required quality, this dual phosphor blend was perhaps the best attempt they were able to make to improve colour properties slightly, without loss of efficacy.
Manufacturer: Polam Pabjanice
Lamp Power: 125 Watts
Lamp Current: 1.15 Amps
Lamp Voltage: 125 Volts
Cap: E27s/30 Nickel plated brass
Bulb Finish: Coated Borosilicate
Bulb Type: E-75
Overall Length: 292 mm
Light Centre Length: 178 mm
Electrodes: Backwound tungsten with double carbonate emitter
Inner / Outer Atmosphere: Inner: Ar | Hg Outer: Nitrogen
Luminous Flux (Vertical): 5,550 lm (at 100 hrs)
Luminous Efficacy (Vertical): 44.4 lm/W (at 100 hrs)
Colour Temperature & CRI: CCT: 4550K CRI: Ra 34 with 8.2% red
Chromaticity Co-ordinates: CCx: 0.364 CCy: 0.398
Burning Position: Universal
Rated Life: 24,000 hours to 50% survival
Warm Up / Re-strike Time: 5 minutes 7 minutes
Factory: Pabjanice, Poland
Date of Manufacture: May 1976
Original / Present Value:
References: 1) Photometric measurements.