How loud are detonators?

[Gloster]

Black/White chevron lever in the frame.

Indeed, pointing down for the Down line and up for the Up line, but not every box had them. At some boxes, like my first, there were dets looped around a bar in the lobby so that in an emergency you could grab them as you dashed out.

 

[The Puddock]

I was involved in a project in a previous job and as part of that I needed to find out exactly how loud detonators are. Like the OP I also struggled to find any info in company and group standards so I eventually phoned the manufacturers, Clayton of Penistone. They told me that there isn't a standard for loudness, they just fill up dets with a certain amount of explosive charge to their traditional recipe and they reckon that should make a suitably loud bang. I was really surprised that the industry hadn't come up with a standard but that's what they told me. This happened in 2013 and I don't imagine anything has changed in the last ten years.

 

[Llanigraham]

How are you going to measure how loud they are? There are far too many variables to get an accurate reading. Dets placed on top of an embankment are going to sound much quieter than dets placed in a cutting or between buildings, even weather conditions can affect things.

I've been trained to do Noise Inspections for MotorSport UK and our rules on how and where to take readings are quite specific and are based on scientific advice.

 

[Tallguy]

If the OP requires the services of consultant acousticians with experience in workplace noise levels and very specialist circumstances the. I suggest contacting Stephen Stringer or Richard Muir at Sandy Brown Associates in London. Sandy Brown is the leading acoustic consultancy in the UK and both Stephen and Richard have formidable reputations in their field.

 

[AndrewE]

I was involved in a project in a previous job and as part of that I needed to find out exactly how loud detonators are. Like the OP I also struggled to find any info in company and group standards so I eventually phoned the manufacturers, Clayton of Penistone. They told me that there isn't a standard for loudness, they just fill up dets with a certain amount of explosive charge to their traditional recipe

No they don't.

and they reckon that should make a suitably loud bang. I was really surprised that the industry hadn't come up with a standard but that's what they told me. This happened in 2013 and I don't imagine anything has changed in the last ten years.

Actually there was a very detailed BR spec, in about 1980 at least. Not specifying outcomes in noise levels or anything, but exactly how they had to be assembled. Even down to the black powder weight and grain size, which I have personaly extracted, sieved and weighed, besides doing lots of other QC tests on them. And fitness-for-purpose tests (Chuck a few dozen from each batch into a bucket of hot water, leave overnight to go cold (and suck in water if any seals aren't perfect) then take them somewhere acceptable and run a shunter over them counting each detonation. If any fail, do it again. If they still fail the batch is scrapped. I never knew it to happen.)

I suspect the spec was based on a (possibly pre-war) set of trials which found out what worked and insisted it should be just like that. The trouble with performance specs ("to allow alternative suppliers fair competition") is that often the the people drawing up the (new) spec don't really understand the job, or why things are as they were. The consultants produce a "performance spec" which is very soon found to be not fit for purpose.

As I said (but it seems to have been ignored) most of the alert to the footplate staff is by structure-borne sound. Actual volume at the ear is a bit of a red herring.

 

[Pigeon]

I'm guessing that is RMS in uk parlance?

No, it's a peak measurement - capture the peak of the signal, and then hold that measurement. RMS is Root Mean Square; it's meaningful for continuous signals, but not so much for an isolated impulse like a detonator going off.

They are bloody loud from inside the passenger compartment of an old DMU. Used to hear them every day for a spell when there was a TSR just north of Worcester tunnel and they were putting dets down for every train.

 

[The Puddock]

No they don't.

Actually there was a very detailed BR spec, in about 1980 at least. Not specifying outcomes in noise levels or anything, but exactly how they had to be assembled. Even down to the black powder weight and grain size, which I have personaly extracted, sieved and weighed, besides doing lots of other QC tests on them. And fitness-for-purpose tests (Chuck a few dozen from each batch into a bucket of hot water, leave overnight to go cold (and suck in water if any seals aren't perfect) then take them somewhere acceptable and run a shunter over them counting each detonation. If any fail, do it again. If they still fail the batch is scrapped. I never knew it to happen.)

I suspect the spec was based on a (possibly pre-war) set of trials which found out what worked and insisted it should be just like that. The trouble with performance specs ("to allow alternative suppliers fair competition") is that often the the people drawing up the (new) spec don't really understand the job, or why things are as they were. The consultants produce a "performance spec" which is very soon found to be not fit for purpose.

As I said (but it seems to have been ignored) most of the alert to the footplate staff is by structure-borne sound. Actual volume at the ear is a bit of a red herring.

Well, that's what they told me. You agree with me, however, that the rail industry in the UK currently has no specified standard for the volume of the explosion made by an exploding detonator (as in a "it must produce a sound pressure of X decibels measured a Y metres" sort of thing)?

 

[ComUtoR]

Stood near 3 as they exploded (I was approx 25-30m away) and driven over dets twice. They are certainly pretty loud but I never had any damage or any concerns. I appreciate that others may have experienced other circumstances.

My last hearing test was a few weeks ago and I passed. I get periodic medicals every 3yrs so I'm sure any damage would have been picked up by then.

Blame/Claim situations aren't as simple as "this happened, so gimmie money" There would be a thorough investigation as to why somebody was so close to detonators exploding and the affects of long term damage from repeated exposure or a singular event.

I hope the person is ok.

 

[AndrewE]

I was involved in a project in a previous job and as part of that I needed to find out exactly how loud detonators are

People have no idea how difficult/sophisticated noise measurement is.
A detonation (like when the can of a det bursts) has an instantaneous pressure pulse, (which is a "noise," but almost impossible to measure absolutely exactly.) Then you have a sound pressure level measured by what normal microphones can respond to, missing the highest instantaneous pressure unless they have been designed to capture that - in which case they can't measure the noise in a way that correlates with any other noise measurement. There are lots of measures which do their best to produce a useful number, see the frequency weighting section on wikipedia https://en.wikipedia.org/wiki/Sound_level_meter. This seems to say that an instantaneous SPL is now a reality.

Well, that's what they told me. You agree with me, however, that the rail industry in the UK currently has no speciftied standard for the volume of the explosion made by an exploding detonator (as in a "it must produce a sound pressure of X decibels measured a Y metres" sort of thing)?

No I don't, I have absolutely no idea about the current standard.
I just said that BR (in the 1980s/90s) had a very detailed spec of exactly how dets had to be when delivered - and hence how they should be made. And that people making up "modern" standards (consultants being paid to produce guff in the modern style) often don't really understand either the science or the industry they are about to lock into a straight jacket.

I also said that I don't think that what we in the UK call Sound Pressure Level (SPL) in deciBels, dB, at whatever distance in air (and whether A-rated - mimicking
the human ear's threshold of hearing at different frequencies, or linear, or C-weighted) is particularly relevant to the detection/hearing of dets on the footplate...

A further problem is that hearing protection almost always uses A-weighting, whetre the human threshold of hearing is subtracted from the actual SPL at each frequency...

 

[Efini92]

Question for the forum: has the dB level formally been measured on track-placement detonators? Do we know what the dB SPL level is of these devices (on a quiet day)

They are about as loud as a shotgun, roughly 150/160db

 

[The Puddock]

No I don't, I have absolutely no idea about the current standard.
I just said that BR (in the 1980s/90s) had a very detailed spec of exactly how dets had to be when delivered - and hence how they should be made. And that people making up "modern" standards (consultants being paid to produce guff in the modern style) often don't really understand either the science or the industry they are about to lock into a straight jacket.

I also said that I don't think that what we in the UK call Sound Pressure Level (SPL) in deciBels, dB, at whatever distance in air (and whether A-rated - mimicking
the human ear's threshold of hearing at different frequencies, or linear, or C-weighted) is particularly relevant to the detection/hearing of dets on the footplate...

Ok. I don't know if this is just your posting style but you're coming across quite aggresively when really there's no need to be so wound up. You've told me your experience, I've told you mine. I'm not trying to pick a fight with you, if that's how you've interpreted my posts!

 

[AndrewE]

Ok. I don't know if this is just your posting style but you're coming across quite aggresively when really there's no need to be so wound up. You've told me your experience, I've told you mine. I'm not trying to pick a fight with you, if that's how you've interpreted my posts!

don't misinterpret my replies then, or assert that I am agreeing with you.
You are guessing about science and my knowledge of current facts and getting both wrong.

I told you that a) BR knew what it was doing and that it was fit for purpose at the time and b) in my (professionally-qualified) opinion it was probably perfectly adequate, and that lots of supposedly "scientific" over-thinking by consultants since Railtrack was set up is probably money wasted, as most of them don't understand the science or the industry.

 

[Islineclear3_1]

Thanks to everyone; I think I have my answers

 

[Nippy]

The procedure now is that date expired detonators have to be sent now for a controlled destruction. Whether that happens in practice...

We ‘may‘ have done 24 out of date ones from the Signalboxes in the loop at Slough once.That ‘might‘ have been very loud.

 

[Annetts key]

and that lots of supposedly "scientific" over-thinking by consultants since Railtrack was set up is probably money wasted, as most of them don't understand the science or the industry.

A bit like a shed load of other stuff on the so called modern railway.

Honestly, if you have ever heard a real detonator go off, there is absolutely no ignoring it. They are plenty loud enough both trackside (outside of a train) and in older rolling stock.

I’ve not been in a modern train (a type built since privatisation) that has set off a real detonator, so can’t comment on that aspect. But I can’t imagine that it would make any significant difference. As as previous poster says, a shock wave will be transmitted through the wheel, axle and rest of the trains structure.

Also it was not uncommon for BR standards to specify the components and construction of systems and any railway specific tests that said item would have to meet, rather than an external performance or external standard.

 

[323235]

I remember when I did the last train around the Oldham Loop Line and we went over a detonator to mark the occasion - I think half of Oldham would have heard it, I certainly did and the train was rammed with people toasting, chattering and marking the occasion with beers.

 

[185]

The previous time i heard dets being cracked off, it sounded like a flatulent cow. More recently during the rescue of a demic I nearly fell out the seat as it sounded like a ____ going off.

Think it depends on how they are made, and how old they are.

 

[D365]

Also it was not uncommon for BR standards to specify the components and construction of systems and any railway specific tests that said item would have to meet, rather than an external performance or external standard.

Yes indeed - I've been spending a lot of time on PADS recently. The breath of BR standards and specifications is impressive.

 

[cockneyviking]

Very loud when you chuck a brick on one in an underpass!! Back in the days of stupidity as a teenager.

 

[Falcon1200]

Honestly, if you have ever heard a real detonator go off, there is absolutely no ignoring it. They are plenty loud enough both trackside (outside of a train) and in older rolling stock.

IIRC when the Class 91s were introduced there was concern that the cab was so well sound-insulated that a Driver might not be aware of having run over a detonator! Whether this really was a genuine possibility, and if so how it was overcome, I do not know.

 

[ChiefPlanner]

Once travelling back on the narrow gauge Viverais Railway in France on a classic 1930's railcar , we came out of a tunnel and ran over a detonator. To say it was a mighty explosion on such a low floored vehicle was an understatement.

Turned out there was a grass / scrub fire ahead and the incredibly well trained Fire Brigade knew there was a train around , so "protected the line" and stopped us. Stood for no more than 10 mins until the young "pompier" was sent to give us the road , and we carried on, - past the damping down crew. Very impressed.

About a mile later . we ran over a smallish tree - which got stuck under the leading bogie , so I assisted the crew in hacking it out with an axe from the toolkit. Absolutly magnificent day out (we had a trip out on the Mallet) , a nice lunch and some good operating insight. Cannot be beaten.

 

[Michael B]

Very loud when you chuck a brick on one in an underpass!! Back in the days of stupidity as a teenager.

Similar experience when I was a ticket office clerk on the Guildford 'New Line' in the early 80's. We had a local section P'Way gang and one of the gangers took it into his head to put a detonator on the platform in front of me. He then swiftly picked up a paving slab and threw it down onto the detonator which exploded literally a couple of feet in front of me. The bang was incredibly loud and reverberated with an echoey boom through the adjacent village. Fortunately the paving slab protected me from any shrapnel but I have never heard anything so loud before or since. The P'Way guys thought that was a real hoot and happily wandered off to do whatever it was that they did. I do now have mild tinnitus but I think that has been caused by 13 years of blowing a guards whistle and too much Hawkwind through headphones

 

[778]

Similar experience when I was a ticket office clerk on the Guildford 'New Line' in the early 80's. We had a local section P'Way gang and one of the gangers took it into his head to put a detonator on the platform in front of me. He then swiftly picked up a paving slab and threw it down onto the detonator which exploded literally a couple of feet in front of me. The bang was incredibly loud and reverberated with an echoey boom through the adjacent village. Fortunately the paving slab protected me from any shrapnel but I have never heard anything so loud before or since. The P'Way guys thought that was a real hoot and happily wandered off to do whatever it was that they did. I do now have mild tinnitus but I think that has been caused by 13 years of blowing a guards whistle and too much Hawkwind through headphones

If a ganger would have done that today, they would lose thier job and even face criminal charges.

 

[Clarence Yard]

If BR management had found out about it then, the ganger would have been in real trouble. Messing around with “shots” in a public place was a sackable offence. Gross Misconduct.

If he had got a white paper (Form 1) and I was his rep, unless there was a procedural error, I would have advised him to “put his papers in” (resign) before he actually got sacked on his Form 2. What he did - it was beyond stupid.

 

[778]

They are about as loud as a shotgun, roughly 150/160db

Is that as loud as a train horn being sounded, when you are standing directly in front of it?

 

[SteveyBee131]

Is that as loud as a train horn being sounded, when you are standing directly in front of it?

That would depend on the sort of train in question? A 185, 91 or 56 for example is rather loud (having experienced all at close range!) Some others might be less likely to top out the dB scale however.

 

[AndrewE]

IIRC when the Class 91s were introduced there was concern that the cab was so well sound-insulated that a Driver might not be aware of having run over a detonator! Whether this really was a genuine possibility, and if so how it was overcome, I do not know.

and still nobody wants to recognise the part played by structure-borne sound. See post #16

 

[bishdunster]

I recall quite a few decades ago one being dropped down the stovepipe of a p.way hut. i was first out of the door !

 

[Undiscovered]

I'd suggest that if you want to pursue your patients complaints, you'd best make sure all the paperwork around the initial incident has been correctly completed and submitted.
Use of dets is drilled into, certainly at my TOC, everyone who works on or near the line, especially regarding distances for placement and safety

 

[Annetts key]

I'd suggest that if you want to pursue your patients complaints, you'd best make sure all the paperwork around the initial incident has been correctly completed and submitted.
Use of dets is drilled into, certainly at my TOC, everyone who works on or near the line, especially regarding distances for placement and safety

The correct use, as in spacing and safe distance is also always spoken about on COSS (controller of site safety) courses including recertification courses that both Network Rail staff and contractor staff attend. At least, it is on the courses that I’ve been on.