How loud are detonators?

[Islineclear3_1]

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)

 

[ExRes]

I'm not sure of the actual dB level but I can assure you when two go off under the driving cab at 6am because someone forgot to remove them, they're bloody loud

 

[zwk500]

I'm told (by an acoustics engineer) not a railway engineer) that there is a defined standard of dB that has to be audible in the cab. Given that, I'd assume there's also a defined minimum dB the detonator itself must make.

 

[Islineclear3_1]

I'm told (by an acoustics engineer) not a railway engineer) that there is a defined standard of dB that has to be audible in the cab. Given that, I'd assume there's also a defined minimum dB the detonator itself must make.

Is there also a defined standard of dB that has to be heard when on the track? Obviously this will be a lot louder to a track worker than to a driver.

Reason I'm asking is that I've seen a patient today who used to work on the lines and had his ear drums blasted out by a detonator during his shift. And he wasn't wearing ear protection at the time. Certainly was a nasty shock to him

 

[zwk500]

Is there also a defined standard of dB that has to be heard when on the track? Obviously this will be a lot louder to a track worker than to a driver.

Reason I'm asking is that I've seen a patient today who used to work on the lines and had his ear drums blasted out by a detonator during his shift. And he wasn't wearing ear protection at the time. Certainly was a nasty shock to him

I genuinely don't know. I might be able to find out but won't be for a while.
Somebody with RSSB access may be able to find the relevant standard quicker.

 

[12LDA28C]

Reason I'm asking is that I've seen a patient today who used to work on the lines and had his ear drums blasted out by a detonator during his shift. And he wasn't wearing ear protection at the time. Certainly was a nasty shock to him

No doubt that's the reason for the Rule Book requirement to stand a minimum of 30m away from detonators on the line, not only to avoid flying shrapnel but also hearing damage.

 

[Islineclear3_1]

I genuinely don't know. I might be able to find out but won't be for a while.
Somebody with RSSB access may be able to find the relevant standard quicker.

Thank you, that would be really useful.

 

[Llanigraham]

Having been a passenger on a train that detonated 3, BL@@DY loud!

 

[zwk500]

Thank you, that would be really useful.

Haven't found the UK ones, but Australian dets need to be minimum 150dB linear peak hold

 

[Horizon22]

I've been stood maybe 300-400m away from some and they made a quite noticable large bang.

 

[skyhigh]

I genuinely don't know. I might be able to find out but won't be for a while.
Somebody with RSSB access may be able to find the relevant standard quicker.

I've had a search on the RSSB standards page and can't find any hard numbers (though it's entirely possible I'm not looking in the right place).

It seems like BR060 A "Specification for Railway Detonators, Single Chamber Type for Hand or Machine Placing" (1964) would be a useful document, though I can't find a copy of it!

 

[midland1]

There have been cases where detonators have not been heard in the cab of a steam loco as they go off at the front of the loco. Like the Welwyn Garden City accident in 1957.

 

[Ediswan]

Haven't found the UK ones, but Australian dets need to be minimum 150dB linear peak hold

Looking at the document you linked, that is to be measured at 6 meters. Which equates to roughly 135dB at 30 meters, which is still 'close to a jet aircraft on takeoff' territory.

 

[bspahh]

RSSB funded two projects to look at the performance of detonators.
You need to register to see the documents at
https://www.rssb.co.uk/research-catalogue/CatalogueItem/T1155
https://www.rssb.co.uk/research-catalogue/CatalogueItem/T1167

This Word document was the specification for the second of those projects

https://www.contractsfinder.service.gov.uk/Notice/Attachment/1384a539-6bdc-4e68-b8dc-c6b9cdf124c5

This is the Background section from that:

Background

Detonators are small metal devices that contain a small quantity of explosives, that are placed on the railhead to cause a loud sound, activated by the wheel-rail interface of a passing train to alert the driver they are approaching a hazard on the line ahead (RSSB GE/GN8532, 2015). During track possessions, detonators are intended to provide a safety protection method if for example a train has been incorrectly signalled into a worksite or to mitigate unauthorised engineering trains exiting the worksite.

For detonators to be effective, they must be clearly audible so necessary precaution and mitigation action can be taken. The Rail Group Standard GM/RT2160 (RSSB, 2010) mandates the requirements for the audibility of detonators in driving cabs, and states that:

“Driving cabs shall have acoustic characteristics that ensure that exploding detonators, as specified in BR 0640A, can be heard inside the cab at any vehicle speed and readily distinguished from background noise” (p. 5).[1]

In a live running railway, it is expected there are a variety of circumstances that will affect the audibility of detonators. T315 workstream 1: noise exposure of staff in driving cabs (RSSB, 2004)[2] suggest sources of driving cab noise include rolling noise, traction and ancillary equipment noise, aerodynamic noise, warning horns, in-cab audible warnings, air-conditioning equipment and heater fans. These, and other factors such as environmental conditions (e.g. weather), insulation of the cab, and subjective comfort, may influence the extent in which detonators are audible to the driver.

Detonators that are not clearly audible to the driver may exacerbate safety risks, if they are not alerted to a hazard or possession on the line ahead. T326 Good Practice Guide for the design of alarms and alerts (RSSB, 2008) note that warning alarms must be heard against background noise but should not exceed noise tolerance limits. Ambient noise should be no greater than 85dB(A) for any length of time, and alarms should be between 15 and 25dB(A) above the ambient noise, which in total, should not generally exceed about 110dB(A). As detonators provide a warning alert that is activated externally to the cab, given variable factors that may influence the audibility of detonators, it is unknown in what conditions detonators are clearly audible to the driver.

It is also possible that audibility of detonator activation may alert track workers of an approaching train. The extent in which detonators may be audible to track workers is likely to vary depending on conditions such as distance of working from detonator placement, weather, personal protective equipment (ear protection) and machinery in use. However, little evidence is currently available to determine whether detonators provide such secondary function, and what, if any, conditions may influence their effectiveness in being audible to track workers. Therefore, this research sets out to evaluate the effectiveness of detonators, to determine the conditions in which they are audible to drivers within the cab and track workers.

It is recognised that the placing and removing of detonators require staff to access the track, exposing them to risks of trackside working, including train movements, slips, trips and falls. This research does not investigate the risks and benefits associated with detonator use, as this is being undertaken in RSSB research project T1155 – Reviewing the risks and benefits of detonator use. T1155 is undertaking a case by case review of detonator use, benefits and risks, to identify cases where a safety benefit can be gained through alternative options to detonator use[3]. T1155 also includes a review of alternative technologies and options to detonators. Therefore, T1167 (this project) is expected to align to T1155, which will be supported by RSSB staff working across both projects.

---

[1] https://www.rssb.co.uk/research-catalogue/CatalogueItem/T1155
[2] https://www.sparkrail.org/Lists/Records/DispForm.aspx?ID=9995
[3] The case scenarios to be examined are: a) Assistance to failed train, b) Emergency protection, c) T3 protection, d) Line blockage protection, e) Single Line Working, f) Working of single and bi-directional lines by pilotman: Working to the point of obstruction, g) Temporary Block Working, h) Movements towards an isolated section, and i) Divided train.

 

[Taunton]

New Year at midnight, Taunton steam shed, all the date-expired detonators (which conveniently expired at that moment) were laid on the outlet track and run over by a loco. Audible halfway across the town.

 

[AndrewE]

In a modern (by which I mean 1960's!) loco cab - and presumably on a steam engine too, maybe more so because of the lower amount of springs and dampers - much of the awareness/audibility of dets comes from structure-borne sound. It was described to me as sounding in the cab like a metal edged workbench being struck hard with the edge of a heavy steel rule.

 

[Islineclear3_1]

Looking at the document you linked, that is to be measured at 6 meters. Which equates to roughly 135dB at 30 meters, which is still 'close to a jet aircraft on takeoff' territory.

That's very useful cheers So a rough guess would be about 144 dB SPL at 10 meters (?).

RSSB funded two projects to look at the performance of detonators.
You need to register to see the documents at
https://www.rssb.co.uk/research-catalogue/CatalogueItem/T1155
https://www.rssb.co.uk/research-catalogue/CatalogueItem/T1167

This Word document was the specification for the second of those projects

https://www.contractsfinder.service.gov.uk/Notice/Attachment/1384a539-6bdc-4e68-b8dc-c6b9cdf124c5

This is the Background section from that:

I found my old RSSB credentials and had a look at these documents. No mention of sound pressure levels however.... shame

Haven't found the UK ones, but Australian dets need to be minimum 150dB linear peak hold

I'm guessing that is RMS in uk parlance?

 

[12LDA28C]

That's very useful cheers So a rough guess would be about 144 dB SPL at 10 meters (?).

What does 10 meters metres have to do with anything? Nobody should be 10m from exploding detonators.

 

[Ediswan]

That's very useful cheers So a rough guess would be about 144 dB SPL at 10 meters (?).

I used this. It also covers the underlying maths.

https://www.omnicalculator.com/physics/distance-attenuation

This distance attenuation calculator is a tool that lets you analyze how the sound propagates in the air.

 

[Islineclear3_1]

What does 10 meters metres have to do with anything? Nobody should be 10m from exploding detonators.

Standing on a bridge?

I used this. It also covers the underlying maths.

https://www.omnicalculator.com/physics/distance-attenuation

I understand the inverse square law but this is great, thanks

 

[Parham Wood]

In the old days S&T engineers used to put detonators (date expired I guess) in the mechanical signal box locking frame. Quite a shock for the signalman when he pulled the booby trapped lever!

 

[zwk500]

I'm guessing that is RMS in uk parlance?

I have no idea I'm afraid, and if this is potentially getting legal I won't speculate/comment beyond pointing to appropriate documents.

 

[D365]

In the old days S&T engineers used to put detonators (date expired I guess) in the mechanical signal box locking frame. Quite a shock for the signalman when he pulled the booby trapped lever!

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

 

[12LDA28C]

Standing on a bridge?

A member of the public then?

 

[Islineclear3_1]

A member of the public then?

Rail staff can stand on bridges Could also have been on a signal bracket/gantry

This is detracting from my question so if you don't have anything useful to add....

 

[zwk500]

Reason I'm asking is that I've seen a patient today who used to work on the lines and had his ear drums blasted out by a detonator during his shift.

What does 10 meters metres have to do with anything? Nobody should be 10m from exploding detonators.

Standing on a bridge?

A member of the public then?

Not after a member of the public, according to the OP

And he wasn't wearing ear protection at the time. Certainly was a nasty shock to him

This might be more important than any legal standards about dB levels.

 

[Shimbleshanks]

About 20 years ago, I was on a Redhill-Tonbridge Cl313 that went over two dets as it approached a broken-down train in front of it near Edenbridge. A lady in the seating bay opposite was quite shocked and scared by the noise; the guard didn't bother giving a warning over the PA. Fortunately I was able to tell her what it was and that there was nothing to worry about.

 

[dk1]

I once went into a worksite setting off the dets when they’d set it up on the wrong line. I thought somebody had thrown a rock at the DVT door never even considering a detonator.

 

[Gloster]

I don’t know what the current situation is, but in the early 1980s plenty of manual signal boxes had detonator placers right outside the box, often with two dets in them. The box windows might be open or the signalman might even be leaning out to attract the driver’s attention. In some places the signalman might have had to go out onto the track to fasten dets to the rail head as the train approached and not be back inside. All part of the job.

 

[dk1]

I don’t know what the current situation is, but in the early 1980s plenty of manual signal boxes had detonator placers right outside the box, often with two dets in them. The box windows might be open or the signalman might even be leaning out to attract the driver’s attention. In some places the signalman might have had to go out onto the track to fasten dets to the rail head as the train approached and not be back inside. All part of the job.

Black/White chevron lever in the frame.