View Full Version : The Bomb Power Indicator Equipment Information

24-09-2010, 07:31 AM
Bomb Power Indicator known by the acronym BPI was a detection instrument, located at the twenty five British Royal Observer Corps controls and 1563 ROC underground monitoring posts, across the United Kingdom, during the Cold War that would have detected any nuclear explosions and measured the peak-overpressure of the blast waves.
The instruments, operated by volunteers, measured the level of peak-overpressure at the instrument's location. Once readings had been combined with information provided by the Ground Zero Indicators it would be possible to estimate the size of the nuclear explosion in megatons. Detailed BPI information was backed up by the automatic AWDREY readings.
The BPI was designed and built by the Atomic Weapons Establishment at Aldermaston and tested for performance and accuracy on real nuclear explosions at the 1957 Kiritimati (or Christmas Island) nuclear bomb test (after being mounted onboard a ship). A number of BPIs were also tested in Australia during the Operation Buffalo series of nuclear tests mounted at various distances from ground zero.
Above ground a pair of circular plated baffles would be affected by the passing of the blast wave. The detector was connected by a steel pipe to the indicator dial below ground in the protected monitoring post. The dial was wall mounted and measured readings from 0.1 to 5 pounds per square inch peak overpressure. Readings below 0.3 pounds per square inch were noted but not reported.
The baffles were normally stored below ground and only screwed onto the top of the pipe at the start of exercises or at Transition To War. Outside of operations the BPI pipe was protected by a screw on cap and there was a drain valve at the base of the instrument to remove any excess rainwater.
If the BPI registered a reading of 0.3 or higher the operator would wait ten seconds before pressing the reset button and making a report to the group control. One minute after a BPI reading an observer is sent above ground to change the photographic papers in the Ground Zero Indicator.
Royal Observer Corps reports following a reading on any BPI were prefixed with the codeword "Tocsin" eg "Tocsin Shrewsbury 56 post - (time) oh five fifty five - pressure two point six".

Taken from Wikipedia.

On the far right hand side.

Seen in the ROC heyday at Sandy ROC Post

Anyone with a detailed picture, please post! Im not lucky enough to own one, but i know many of you guys our there are!

24-09-2010, 03:11 PM
Happy to oblige:thumb


This is the BPI for Middleton Stoney:thumb
The Blue backing plate indicates that this originally came from the UKWMO:thumb

24-09-2010, 03:42 PM
Ill get some pics up of mine when I get home from work, good thread.

24-09-2010, 09:47 PM
that makes me hard.

You should see Industry's BPI. Its perfect, no scratches or anything, just perfect. Ohhhhhhhhhhhhhhhhhhhhhhh