Ffestiniog Railway experimenting with modern firing system
One
of its locomotives has been reconverted by the narrow-gauge Ffestiniog Railway
from oil to coal firing. A first change - from coal to oil - took place after
the 1970 season, principally to remove the fire risk from sparks when running
through forestry plantations in the hills above Porthmadog. Subsequently, all
the FR's steam locomotives were similarly converted.
However, the current reversal is not to the traditional method of coal firing, but experimentally to a more modern technology which has been used in recent years by some overseas railway administrations still operating with steam traction. This permits the use of low-grade coal without the formation of clinker in the firebed, and also virtually eliminates spark emission. It is known as the Gas Producer Combustion System.
Former Penrhyn Quarry Company 2-4-0 tank-tender engine Linda (Hunslet 590/1893) is the subject of this experiment, the alterations being carried out at Boston Lodge Works, as part of a major overhaul, its first since 1970, during which period the engine has travelled around 112,000 miles. Major features of the conversion have been a rocking pinhole grate of only 10% airspace, preventing air from lifting the fire and forming holes in the firebed at high power outputs and also allowing a thicker fire; the fitting of two secondary air inlets to each side of the firebox; and a steam exhaust system which includes a manifold and a cluster of four nozzles.
The chimney has a cylindrical mixing chamber and diffuser. This last is the only readily noticeable change to the locomotive's appearance (reminding one of the tall Urie Stovepipe, as fitted to the Southern's "Greyhounds") but, when trials are complete, the Hunslet parallel chimney and cap will be replaced over the Lempor type. A self-cleaning spark arrestor has been fitted.
A steam supply, provided when in motion from the exhaust system, is sent to the ashpan, where it mixes with the reduced amount of primary air. A chemical reaction then takes place in the firebed, producing gas which is burnt in the secondary air admitted above the fire and which has an increased calorific value compared with normal combustion. Secondary air is also channelled under the brick arch, through a vertical flap-type firedoor.
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Close-up
of the blastpipe arrangements and self-cleaning smoke box. © Norman
Gurley |
Trials before Easter caused small modifications to he carried out and these have resulted in the successful haulage of eight corridor coaches, the normal maximum loading for this class of locomotive on the ruling 1 in 80 gradients of the line. Significantly higher superheat temperatures have been recorded than with oil firing, and expectations regarding the lower cost of operating a locomotive using this system would seem to be fully justified, according to the FR, although exact figures will not be available until the tuning work and testing are completed.
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Notched
operating lever of the firehole door enables it to be left open to admit
secondary air under the brick arch. © Norman Gurley |
Taken from 'Railway Magazine', August 1985
No author was credited in the magazine.