Nitroglycerine Section (NG Hills)
Control Blockhouses :-
Key Points :-
- References in Gordon Nicholson's 1942 article "Manufacture of 'A' Nitroglycerine - Continuous Nitration"
- Located beside Nitration House embankment and able to dump the Nitration reaction into the
Drowning Tank remotely. Also could cut off power to the House.
- Small brick-built structures stand beside both Nitration Houses.
- Electrical supply services and floor-level openings, indicating that some power and possibly liquid function
- Small 'sentry box' structures stand beside Nitration House ground level pedestrian enmtries and could be
for emergency drowning controls.
- 25 Volt Emergency Lighting - Battery location uncertain but possibly Charge House or Control Blockhouse.
- Further investigation (possibly excavation) advised.
Blockhouse at Unit 2 NG Hill from SE. Central floor-level opening.
The Charge House, the Acid Tank bases and the Nitration House are easily understood features of the NG Hills, but there are
two associated buildings that are harder to understand and yet are plainly part of the process. In his work on the
manufacture of Nitroglycerine, Gordon Nicholson refers in passing to a 'Block House'. :-
- "the block-house just outside the nitrating house embankment". It held a hand-lever to
open the drowning-cocks that could dump the contents of the Nitrator and Primary Separator into the Drowning Tank under
- "There is also a press button switch in the block house which cuts off the electric power". It might also be the battery
house for the 25 Volt emergency lighting within the Nitration House and the tunnel (covered trolley runway) to the Final
Wash House. That implied a building which was able to monitor and stop the nitration process and through which the power supply could
be routed. In other parts of the site (e.g. Cordite Milling Section) this building would be termed a Motor House,
but at the NG Hill 'Control Blockhouse' may be a more appropriate term.
Archaeological Evidence for the Control Blockhouse :
Only two buildings match the Nicholson description and are present at both NG Hills :-
To summarise, the writer wonders whether the 'sentry-box' did have a mechanical cutoff and button switch in it, but is inclined to the
opinion that the Blockhouse referred to by Nicholson was the larger of the two buildings. It could have had a remote valve
and control function, possibly with electrical repeater dials for input flow rates, temperatures and pressures.
- In Unit 2 NG Hill there is a brick building beside the Nitration House embankment with sloping concrete slab roof and composition waterproofing,
about 4 metres long by 2.75 metres wide. It has a doorway midway along one long wall and an opening at floor level on the
far side from the door, partly closed by a corrugated asbestos sheet. There are four metal supports along that wall. Steel
-sheathed power conduits go through the end wall of this building, indicating that it at least had some power control
function and there is a fuse box on the inside of that wall. It is possible that building held the emergency lighting
batteries and possibly a panel of control gauges and dials similar to those beside the Schmid Nitrator. As against that,
the building is not in line with any entry to the Nitration House, so a mechanical wire linkage like that for a Victorian
house bell system could have been run from the floor slot along conduits into the Nitration Hill.
- In Unit 1 NG Hill the Mixed Acid tank bases and the High Pressure Air Tank base are beyond Nitration House AB1 on its
north side, so at some distance from the one Blockhouse beside Nitration House AB2; what may be the walls of the Refuse Acid
tank base are beside the Blockhouse. It seems that the twin Nitration Houses shared a Blockhouse, which may explain its
position almost between them. Malcolm Bowditch has suggested that one Nitration House may have been shut for maintenance
whilst the other was operating, which might make sense and avoid duplication of controls.
- A sentry-box size brick building with a slab roof stands beside the ground floor entry to each Nitration House. The rear
wall has a number of heavy bolt studs on it but no obvious apertures for levers or wires. It could have held the two
controls indicated but nothing else. In its favour, a mechanical wire linkage system could have been run more easily from
the outside of the 'sentry box' along the passage and into the Nitration House. Unfortunately, there is no sign of any way
in which a man in that box could monitor the activities within and know when to pull the lever or press the switch, except
if warned by some kind of alarm bell. For the anxious, the 'sentry boxes' in both Units are only a short distance from a
single-seat outside bucket toilet with a blast wall.
The Blockhouse and the 'Sentry Box' appear to be parts of multiple layer safety control system to halt the reaction in the
Nitration House if it overheated and ran out of control. In addition, the Blockhouse may have remotely monitored the
reaction and housed the emergency lighting batteries and control system. Some features are so uncertain that further
investigation - possibly involving excavation - would be advised in order to gather more evidence.
Back to Nitroglycerine Hills page ~
Back to Charge House
Forward to Nitration House ~
Forward to Final Wash House
© 2006 Richard Edkins, Dalbeattie Internet.