of nearly 150 °C only 25 min into the burn. No cracks that wide were present in the 2x6#1&2. The same
trend was noticed in the 4x6 RGO tests shown in Figure 3.

Other temperature data from the tests suggest imperfections in the construction of detonator containers
influence when detonators start to explode. In the test with one detonator suspended, it exploded at
172°C while the air temperature was 200°C. The average temperatures at the 1" det time in the other
tests were as follows. The air in the 16 boxes was 171°C with a relatively high standard deviation of 51.
The center of the detonators was only 67°C with a relatively low standard deviation of 8 in the 7
measurements taken. The temperature of joints varied from 43°C to over 726°C (in 2x6#3) at the 1" det
time depending on the tightness of the joint. The average temperature of the bottom inside wall fell into
two sets but was always well below the temperature of joints which did not meet flush. For the wood
boxes, it was 57°C with a standard deviation of 16 in 8 tests (excepting 4x6#1). For the metal/plywood
and IME 22 composites, it was 119°C with a standard deviation of 20 in 6 tests.

The M/P#1 test yielded a 1" det time of 16 min. Despite the heavy steel latch, the lid flew open on this
box in 25 min. This was prevented in the next two tests by putting a %-inch bolt through the latch and
bolt to prevent it from pulling out under the pressure of detonators exploding. In M/P#2, a detonator
went off in 21 min. Then, 38 min into the burn, one of the welded seams split and allowed a few
detonators to escape. Although a detonator went off in 12 minutes in M/P#3, it was the only test in
which detonators never escaped the box. Along with the improved latch, the interior joints of this box
were filled with common stove pipe caulking.

The boxes in M/P#1 and M/P#3 had gaps as wide as %-inch where the plywood sheets met. The box in
Metal#2 had tight fitting joints. The effect is apparent in Figures 4 and 5, the air and crack temperatures.
The crack temperature in the M/P#2 test roughly followed the air temperature. In M/P#1&3, the crack
temperature was hotter than the metal shell from about 5 minutes on. The stove pipe caulking reduced
the crack temperature somewhat and may have kept the air temperature from continuing to rise in M/P#3.
Histograms of the number of exploding detonators per minute up to when the box’s lid opened are shown
in Figure 6. Figures 6a-c show detonators were going off at a rate of over | per second just before the
lid opened in M/P#1 and the seam split in M/P#2. However, in test Metal#3, detonators never went off
at a rate faster than 45 per minute. Whether or not the application of caulking was the reason for this is
undetermined.

The IME 22 boxes showed great variability in their significant event times. The 1“ det time varied from
17 min in IME#3 to 165 min in IME#1. Detonators were expelled in about 50 min in IME#2&3 and
165 min in IME#1. The different exteriors mentioned earlier are mainly responsible for this. Why a
detonator went off in 17 minutes in IME#3 is undetermined.

Figure 7 shows the temperature of the metal in the IME 22 box tests. The insulating effects of the
different exteriors (1/4-inch plywood, ¥%-inch plywood, and %-inch plywood coated with 1/16-inch
fiberglass) are apparent. Two hours into IME#1, the metal temperature had not yet reached 200°C. In
IME#2&3, the metal reached 200°C in just over 10 and 20 minutes. This carried over to the air
temperatures as seen in Figure 8.


8

‘Temperature C
a
8

Figure 4. Metal/Plywood Air Temperatures

g

Minutes from Start of Fire

Temperature C

Metal/Plywood Crack Temperatures
i : Leobeann

08:00

8 8 8 8 8 8
2 2 & & 8 8

Minutes from Start of Fire



References

(1) Institute of Makers of Explosives Safety Library Publication No. 22. “Recommendations for the Safe
Transportation of Detonators in a Vehicle with Certain other Explosives”, Institute of Makers of
Explosives, Washington, DC, May, 1993, 16 pp.

(2) The United Nations, Recommendations on the Transport of Dangerous Goods, Test and Criteria, 2m
edition, Labelmaster, Chicago, IL., 1990, p. 126.

(3) Darling, J.A., “Burning Trials of a Test Container Protecting Detonators from Fire”, Canadian
Explosives Research Laboratory, CANMET report MRP/MRL 81-104(OP), September, 1981, 7 pp.

(4) Becker, K.R., “Status Report-Effectiveness of Barriers and Containers”, U.S. Bureau of Mines’
Pittsburgh Research Center Report No. 4304, December 2, 1980, 11 pp.

(5) Dowling, T.P., Trojan - U.S. Powder Co. Memorandum on “Testing of Containers for Combination
Electric Blasting Cap/High Explosive Shipments”, October 11, 1971, 11 pp.


Figure 6d shows the number of exploding of detonators each minute after the test was started for IME#3.
More research is needed to explain why a detonator exploded 17 min into the test and 6 more exploded in
the next 20 minutes This event did show that having a detonator container securely closed can be
critical. The latch on this box was wired shut but gave way when the first detonator exploded allowing
the lid to open and at least one other detonator to come out. This detonator exploded in the burn pan in
the next few seconds. Since a padlock would have prevented the box from opening, this event was not
considered a threat to explosives. Surprisingly, the lid opened slightly when the next detonator exploded
but did not open again until it was blown off its hinges 24 minutes later.

Other observations showed that the type of closure hardware affects the safety of detonator containers.
In IME#2&3, the lid latch and hinge were made from aluminum. Common aluminum alloys melt between
600-700°C. When the detonators began to explode in rapid succession in tests IME#2&3, the lid was
thrown off since the only thing holding it down was its own weight. These boxes may have opened
sooner if they had side opening doors instead of top opening lids. The IME#1 box came open as soon as
detonators started to go off. Even though the latch and hinges were heavy duty steel, they were not
attached to the metal shell and had no strength since the wood they were attached to was burned away
when the detonators started to go off.

The closure mechanism is definitely an issue with less insulated boxes like the metal/plywood composite
boxes. In M/P#1, the %-inch steel bolt, which extended over an inch into the latch, was bent and pulled
out of the latch by the force of the exploding detonators. The addition of a %-inch machine bolt through
the %-inch steel bolt and latch prevented this in M/P#2&3. In field use, a heavy cotter pin could serve
the same purpose.

Conclusions

The following conclusions can be drawn from the results of the research.

¢ The craftsmanship as well as the material used in detonator containers have significant impact on the
time and rapidity in which detonators explode in the box in a fire.

© Well constructed boxes with walls of four inches of red oak provide over an hour of protection
against a kerosene fire.

© With proper latch reinforcing and tight fitting or sealed joints, the metal/plywood composite boxes
tested can provide about 30 minutes of protection and have the potential to eliminate the threat of
detonators escaping from the box in a fire.

© The exterior of an IME 22 container has significant influence on its thermal properties.

© The material and method used to close a detonator container have significant influence on when and if
detonators present a threat to nearby explosives.

Acknowledgments

Thanks go to the Getman Corp., Willard Machine and Welding Inc., Austin Powder Co., and the IME for
providing equipment, supplies, and information used in this research.


Temperature C

Figure 2. 2x6 RGO Air Temperatures

250

8

g

8

Temperature C

Figure 3. 4x6 RGO Air Temperatures
300 : TREE ©

250

3

g

0:00
0:10
0:20 4--
0:30
0:40
0:50

Of

1

20 fe
1:30
1:40

1:50
2:00
2:40
2:20

Hours:Minutes from Start of Fire



FIRE PROTECTION PROVIDED BY DETONATOR
CONTAINERS

by
Lon D. Santis"

The Code of Federal Regulations Title 30, Parts 56, 57, 75, and 77 require that detonators and explosives
be separated by four inches of hardwood or equivalents when transported together in mines. This
standard was developed to protect the explosives from initiation by the more sensitive detonators. The
research reported here is an attempt to quantify the fire protection offered by four inches of red oak and
other materials. Boxes with a volume of 6.75 cubic feet were made from four-inch thick rough green oak
(RGO), two-inch thick RGO plied, two-inch thick #1 common (dried) red oak plied, and a metal/plywood
composite. These and boxes meeting the Institute of Makers of Explosives’ (IME) Safety Library
Publication No. 22 were tested in bonfires. The boxes were instrumented with thermocouples, filled with
detonators, and placed over a kerosene fire imparting about 16 kilowatts per square meter heat flux for
up to 3 hours. Tests showed that the wood boxes protected the detonators for over an hour with
variations between the different trials. In the IME 22 container tests, detonators began exploding in as
little as 17 minutes in one test and not for 2-1/2 hours in another test. Detonators in the metal/plywood
boxes began to explode in about 15 minutes but with minor alterations, were able to contain the
detonators. The test results show that the exterior of an IME 22 container significantly affects its thermal
properties. Defects in the form of cracks and the manner in which the container is closed have a
significant effect on the performance of a detonator container in a fire.

‘ Mining Engineer, Pittsburgh Research Center, National Institute of Occupational Safety and Health.


Figure 7. IME 22 Metal Shell Temperatures

IME#2 Bottom |
“IME#2 Side

Temperature C

e@e°e8 98 c0°8 5906 898099 99 9 8
8s 28 8 © 8 8 2 &8& & FF ® SF SF & BF BB
6 & §6 § §6 6 2 & & & fF FB & & & & & A SG

Hours:Minutes from Start of Fire

Figure 8. IME 22 Air Temperatures

Temperature C

ge 2 ¢e 8 ge ge 2e8 8 2 2g © ¢g e
8 £ & 8 & 8B 2 & 8 @¢ 8 8 2 & 8
6 6 6 6 6 6 F FE SF 2 fF fF & BS AO & AW

Hours:Minutes from Start of Fire



Buiuedg piq [yun sewi] UolOUNY Joyeuo}eq ‘g eunBi4

aig Jo ues Woy Sanu

°

e

Bild JO HEIs WOY SaINUIW,

S$ & & RF SRB

2

ZHAI G9 Eun! 4

L#d/W “eg eunbiy

9

a 0% i
5 3

“3 “y
= =

ors os
e 5

os os

09 og

€#HNI pg eunBi4 C#d/IN ‘99 eunBi4
Bud JO WEIS WO. Sa;NUlW S414 JO UR}S Woy SazNUIW
Bas & FB SRBVS’S 8& & & 8S RB aS
+ ore ° 0
re

OL OL
i=] i=]

oz g oz g
Ea Ey
3 g
a i

3 oc 3

ov 5 or ¥
z
3 3

os os

og 09



Table 1. Test Parameters

‘TEST WALL SIZE ‘CLOSURE CONDITION] NO. OF | PAN SIZE|FUEL| SPACERS
inches inside to outside) _| (inches inside) METHOD pets | _ (fet) | ®

fax6H1 4 Red Oak 18x36x18 | _ 8 inch Lag Screws Good 1140 8x8 14 | Fire Bricks
fax6#2 4 Red Oak 18x36x18 | 8 inch Lag Screws Good 1140 8x8 1.6 | Fire Bricks
lax6#3 4 Red Oak 18x36x18 | 8 inch Lag Screws Cracks 1140 8x8 1.6 | Steel Cylinders
l4xoeth 4 Red Oak 18x36x18_|__ 8 inch Lag Screws Cracks 1140 6x6, 12 none
4x62 4 Red Oak 18x36x18_| 8 inch Lag Screws Good 1140 8x8 1.6 | Fire Bricks
4x6e3 4 Red Oak 18x36x18_| 8 inch Lag Screws Good 1140 8x8. 1.6_| Steel Cylinders
|Com#1 4 Red Oak 18x36x18 8 inch Lag Screws Good 1140 6x6 12 none
[Com#2 4 Red Oak 18x36x18_| 8 inch Lag Screws Vented 1140 8x8 1.2 | Fire Bricks
IComi#3 4 Red Oak 18x36x18 B inch Lag Screws _| Large Cracks |_1140 8x8 1.6 | Steel Cylinders
MEAL IMEV172 fe ply (1).(2).@)__| _20x20x18 | Heavy Duty Commercial] Weathered _| 540 8x8 1.6 | Fire Bricks
IME#2, IME+1/2 ply 12x16x12 ‘Aluminum Latch | Small Cracks | _ 300 8x8 1.6 | Steel Cylinders
MEAS IME+1/4 ply 22x36x22 Aluminum Latch | Small Cracks |_1620 8x8 1.6 | Steel Cylinders
MIP 3/4 ply+1/4 steel 18x36x18 Heavy Steel Cracks 1140 6x6 12 none
rea 3/4 ply+1/4 steel 18x36x18_|_ Enhanced Heavy Steel Good 1140 8x8 1.6 | Fire Bricks
MiPH3 3/4 ply+1/4 steel 18x36x18_| Enhanced Heavy Steel_| Filled Cracks | 1140 8x8 1.6_| Steel Cylinders
13/4 in | 1-3/4 hwe+ 1/8 stoel+1/2 fo ply (4)| _18x18x24 Steel Latch Weathered | 600 8x8 16 | Fire Bricks
Orig IMEA1 IME+1/4 ply 16x16x16 (7) Heavy Stee! Good 100 N/A__| Wood NIA
Orig IME#2, Optional IME (5) 16x16x16 (7) Heavy Steel Good. 100 N/A__| Wood NA
[Canada CERL 6) N/A__[ None-Lid Rested on Top | Good 300 N/A__| Wood NA
(IME = 1/2 ply+1/2 gypsum board+1/8 steel (S)Optional IME = 1/4 ply+1 hardwood+1/2 ply+1/4 asbestos+22 gauge steel
(2)fe = fiberglass coated (6YCERL = 1 om ply+3 om semi-rigid glass fiber+3 mm stecl+?? ply
@)ply = plywood (7) = estimated
(A)hw = hardwood (8) = gallons of kerosene per minute except for wood

Figure 1. Significant Event Times

Wi 1st Detonator Explodes |
CO Detonators Outside Box

Hours:Minutes from Start of Fire

Com#1
Com#2
Com#3
1-3/4 in

Orig IME#1

Orig IMEH2
Canada



the joints did not meet flush. In test Com#2, the term “Vented” indicates a 2 inch diameter vent hole was
drilled in the top of the box. In test IME#1, the term “Weathered” indicates the box had been exposed to
the weather for about 7 years. In test M/P#3, the cracks were “Filled” with common stove pipe caulking.
The column “Pan Size” lists the plan view size of the pan used to contain the kerosene. The column
“Spacers” lists type of spacer placed in the pan to reduce the burning surface area. The term N/A means
not applicable.

The heat source was kerosene floated on 6 inches of water in all the tests. The variations in size of pan,
fuel feed rate, and type of spacer had no significant effect on the data. Analysis of the data from the
bottom outside thermocouple of tests 4x6#1, Com#2, 2x6#1, 2x6#2, and 2X6#3 indicate a thermal flux
of between 14.6 and 17.6 kilowatts per meter squared. The outsides of the boxes reached 300°C within a
few minutes and temperatures as hot as 1,000°C were recorded.

Each test was video recorded and instrumented with eight type K thermocouples. The thermocouple
leads were insulated from the fire with 1-1/2 inches of ceramic fiber insulation assuring no thermal
damage to the thermocouples. Each test had a thermocouple in the airspace of the box. Each test except
4x6#1 had a thermocouple on the outside and inside center of the bottom, and on the outside and inside
center of one side. Thermocouples were also placed in the walls, in the detonator packages, and on joints
or in cracks.

The thermocouple data were recorded with a personal computer based data acquisition system. Each
channel was sampled at 40 hertz through a low pass (80 hertz) filter. A software program then averaged
every 160 data points, converted this voltage into degrees Celsius (°C), and stored the temperature value
with a time stamp every 4 seconds for all 8 channels.

Test Results

The time from the start of the fire to when the first detonator went off (1* det time) and when detonators
were expelled from the box were the two events of interest during the tests. Figure 1 is a bar graph
showing these two times for each test. Again, data from the original IME 22 container tests and a
Canadian test are included in Figure 1. Bars extending to the top of the graph indicate no detonators
escaped from the box. Since test 4x6#1 used only one detonator, the time when detonators escaped the
box was not applicable.

Except for test Com#3 and 4x6#1, the wood boxes prevented detonators from going off from between 85
and 138 minutes. The average for these 7 tests was 104 minutes with a standard deviation of 19 minutes.
All the wood boxes fell apart allowing detonators to fly about within a few minutes after detonators
started to go off.

Craftsmanship was critical as seen in the variability of the 2x6 RGO tests in Figure 1. Here, the three tests
yielded 1* det times of 84, 109, and 138 min. Figure 2, the air temperatures during these tests, shows a
spike in the air temperature in the first ten minutes of 2x6#3. This could be caused by influx of hot gasses
from the fire through cracks between the boards which were quickly plugged by combustion byproducts,
wood excretions, or swelling. These same defects allow a quicker overall temperature rise as seen in the
graph. A thermocouple placed in a 1/8-inch crack in the comer of the 2x6#3 box recorded temperatures


It is clear the mining law only considers the hazard of an accidental initiation of a detonator. When first
promulgated in the 1969 Mine Safety Act, a single box with a divider to separate the explosives and
detonators exemplified the four inch hardwood requirement. This was typical of the time, especially in
underground coal mines and others where relatively small amounts of explosive were used. Today
however, large amounts of explosive are transported requiring separate containers for the explosives and
detonators. Boxes with dividers are still used today, and no history of accidents with 4 inches of
hardwood as a divider exists. The critical features of this type of box would be its thermal properties and
the condition or effectiveness of the barrier while the detonators exploded. For example, if the barrier did
not meet the lid flush, exploding detonators would likely toss live detonators over the barrier into the
explosives. The results of this testing are directly applicable to the thermal properties. The effectiveness
of the barrier would depend on factors such as its ruggedness, the extent of thermal damage, and the
detonator load.

According to the IME, their design is mainly intended for protection ina fire. Prior US Bureau of Mines
research showed the IME 22 laminate provides an adequate shock attenuator also. (4)

The primary hazard is a fire situation. The author knows of no case where a commercial detonator
exploded inside a container during transport other than in a fire. Perhaps a bullet could penetrate the
magazine and strike a detonator, but the magazine has now been damaged and may not perform as
intended. Radio energy presents practically no threat to electric detonators if the legwires are in their
original shipping configuration. However, vehicle fires do occur in mining. According to the
Accident/Injury/Illness database generated from MSHA’s Form 7000-1, there were at least 189 mobile
equipment fires which lasted more than 30 minutes in US mines from 1990 to 1995. Although most of
these incidents involved heavy equipment, 23 involved compressors, forklifts, mancars, or nonhaulage
trucks.

Test Parameters

Boxes with a volume of 6.75 cubic feet were made from 4-inch by 6-inch rough green oak (RGO), 2-inch
by 6-inch RGO plied, two-inch thick #1 common (dried) red oak plied, and a metal/plywood composite.
These and boxes meeting the requirements of IME SLP 22 were placed in kerosene fires for up to

3 hours, The boxes were fabricated by professionals, thus assuring good construction. Each box was
filled with inner boxes of Austin’ Rock-Star detonators with 16 foot (ft) copper legwires. These
detonators were packaged 60 to an inner box and varied only in the length of the delay element. The
detonators had a base charge of 750 milligrams (mg) PETN and an initiating charge of 200 mg lead azide.
Table 1 summarizes the parameters of each test. For comparison, data from the original IME 22
container tests (5) and a test from which the Canadian standard was based (3) are included in Table 1.

Some explanation of terms used in Table 1 is necessary for clarity. The column “Test” lists an
abbreviation for the type of box followed by the trial number if more than one was performed. The
column “Closure Method” lists the type of hardware used to seal the lid or door of the box. The column
“Condition” lists the observed general state of the box before the test. The term “Good” means the box
had not been exposed to weather and had tight fitting joints. The term “Cracks” refer to boxes in which

> Reference to specific manufacturers does not indicate endorsement by NIOSH.


Introduction

The Code of Federal Regulations (CFR) Title 30, Parts 56.6201, 57.6201, 75.1311(b)(2), and
77.1302(e), require that detonators and explosives be separated by four inches of hardwood or the
equivalent when transported together on the same vehicle in mines. Parts 56, 57 and 75, call for four
inches of hardwood, a laminated partition, or the equivalent. The laminated partition is defined as a
minimum of, from detonator side to explosive side, 42-inch plywood, ¥2-inch gypsum wallboard, 1/8-inch
steel, and %-inch plywood. This is also the minimum requirement listed in the Institute of Makers of
Explosives (IME) Safety Library Publication (SLP) No. 22 when explosives can contact the outside (1).
Part 77, the surface coal mine regulations, calls for “four inches of hardwood or the equivalent” with no
definition of equivalent. The Mine Safety and Health Administration’s (MSHA) policy has been to
require the mine operator to prove the equivalency of other partitions prior to use. The mining law also
requires that the detonators be kept in their original packaging if more than 1,000 are transported.

The CFR Title 49 Part 177.835(g) impacts vehicles which transport detonators and explosives together
over public highways. The only compartmental method listed in 49 CFR is use of a container as
described in IME SLP 22. There are also limitations on the quantity and hazard class of detonators
allowed in an IME 22 container. As recognized in these regulations, detonators with a mass detonation
hazard (shipping Class 1.1) can render any box construction worthless. If Class 1.1 detonators were
involved in a fire, it would be expected that all of them would explode at once. If explosives were also
on board, they would likely be initiated through direct shock or impact from flying debris.

There are two hazards when Class 1.4 detonators and explosives are transported on the same vehicle.
The first is a single detonator accidentally exploding and initiating the explosive load. Here, a shock-
attenuating barrier is needed. The second occurs when the vehicle is in a fire which involves the
detonators or explosives; at which point all fire fighting measures should stop. In theory, the explosives
should burn without detonating, but measures must be taken in case they do. The critical aspect now is
that there be enough time to secure the area before the detonators pose a threat to initiating the
explosives. As this takes place, the detonators must not be expelled from their container or else they
could initiate the explosive. Even if the load is only blasting agent, it would be a risky assumption to
believe a stray detonator could not set it off. Consider that the test to determine an explosives’ blasting
cap sensitivity uses a detonator with a base charge of 500 milligrams, a paper container for confinement
of the small charge, and is performed at 25°C (2). In a transportation fire, larger base charge detonators
are likely to be involved and the explosive may be confined, hot, and in larger diameter.

The length of time a detonator container should protect the detonators can be approached two ways.

The first is to determine the time needed to block access and ensure all personnel are in a safe location
away from the fire. A second approach, used by Darling (3), is to determine how long the explosives will
burn. A number of minutes that applies to all situations is impossible to arrive at with either approach.
The first approach depends on conditions at the scene of the fire. The second approach may work well
for high explosives which burn vigorously but, explosives with very high water content could take several
hours to burn. Ideally, the most effective detonator container would not allow detonators to escape the
box in a fire, rendering the time it takes to secure the area or to burn the explosives immaterial.

? Numbers in parentheses refer to references listed at the end of this report.