was 7.2 m/min (23 fpm), decreasing to
6 m/min (20-fpm) when the foam
reached 92 m (300 ft). The advance
rate was significantly slower than the
11.7 m/min (38 fpm) advance rate of
the tests performed with the plywood
pal n. This was attributed to the
restriction offered by the diameter of
the aperture.

At92 m (300 ft) the test was termi-
nated because the IFTS started leaking
foam around both ribs. It is possible
that such leakage could be mitigated
by increasing the size of the IFTS with
respect to the entry dimensions.

Additional tests included inserting
a 1170-mm-diam (46-in.-diam) rigid
tube through the feed-tube hole. This
increased the advance rate to 10.2 m/
min (33 fpm) for the first 30.5 m (100
ft). The initial experiments on the first
prototype showed that the IFTS con-
cept had merit and additional experi-
mentation was warranted,

Tests with inflatable feed-tube
seal, second prototype. In a subse-
quent version of the IFTS (Fig. 8), a
tubular shroud was used to convey
high-expansion foam from the foam
generator to a resilient feed-tube. The
overall dimensions of the IFTS were
also increased to enhance the distance
a foam plug can travel before the de-
vice fails and to allow deployment in
larger or irregular shaped entries.

The 1370-mm-diam (54-in.-diam)
resilient feed-tube incorporated a heli-
cal metal wire that extended the length
of the aperture. A wire-stay prevented
the aperture from collapsing due to the
air pressure in the seal. This helped to

DISTANCE OF FOAM-PLUG FRONT
FROM PARTITION, m

100 1
8oF 4
60 4
aor f7. 4
WA Partitions

= Plywood 4
20 —— IFTS-1

—— IFts-2

1
° 10 20
TIME, min

Fig. 9 — Distance traveled with respect to time of foam plug fronts for three partitions.

maintain the unrestricted propagation
of the foam from the generator through the partition.

A tubular shroud was attached to the front side of the seal
with a zipper and Velcro.* The shroud replaced the collaps-
ible plastic feed-tube used in the previous IFTS. The shroud
was designed to collapse when the foam generator is turned
off. This prevents flow of high-expansion foam back toward
the foam generator. The total weight of the bag, excluding the
blower assembly, was 39 kg (86 Ibs).

Experiments with the second prototype IFTS were con-
ducted in the Lake Lynn experimental mine. The amount of
foam concentrate used in the test was 90 L (24 gal). The
average advance rate of the foam plug for the first 30.5 m (100
ft) was 14.4 m/min (47 ft), decreasing to 9 m/min (30 ft) when
the foam reached 92 m (300 ft). At 183 m (600 ft), the test was
terminated because the IFTS started to leak foam near the
comer of the roof. Such leakage can probably be mitigated
by anchoring the four comers of the exiting foam side of the
IFTS to the ribs.

The distance-time relationships for transport of the foam

* Reference to specific products does not imply endorsement by the US
Bureau of Mines.

plug for 90 m (295 ft) forall three partitions are shown in Fig.
9. The data for all partitions indicate that the advance rate
decreases with distance travelled. This is due to the resis-
tance of foam plug (as the foam plug propagates further away
from the foam generator) and to the constant driving force of
the foam generator. The driving force is constant for this
foam generator. But it can vary depending on the type of
foam generator.

Inaddition, and more importantly, the second IFTS proto-
type (IFTS-2) showed a significant increase in the advance
rate of the foam plug, compared to the earlier version of the
IFTS and the plywood partition. Even though the distance
that the foam plug had travelled was less with the IFTS-2
compared to the plywood partition at partition breaching, the
foam-producing efficiency was increased. This improved
efficiency (the distance the foam-plug front traveled from the
partition with respect to time) was mainly due to the enlarged
diameter of the resilient feed-tube.

Future studies. Additional experiments are planned to
evaluate the maximum distance a foam plug can travel in an
entry before the device fails (by anchoring the four corners of


Syindrica! feed
‘through hake

Fan

led tea tube.

Collapsible plastic tubing

Slntietable tees
‘ube: seat interface:

30.5 m (200 ft) of entry inde condi-
tions with high-expansion foam com
pared toa weteniry, Phe foam shrunk
0.3. (1 fii from the roof aver the first
hours, {¢ continued to shrink an
additional 0.46 m().5 ft) over the next
96 hours,

‘Tests with inflatable feed-tube
seal first prototype. The PTS was
developed and tested to improve the
time required toerect partitions during
amine fire wear the fire location, Inan
experiment in the Lake Lynn
mental mine Fig. 6), an IFTS (2.6 om
me OF
inflated in an
entry. 2.i mhigh by 3.4m wide (7 x 19
ft te evaluate projuigation distance.
The diesel-powered bigh-expansion

tion falture depends on how well « partition is constructed.
During the above test, she advance cate of foam for the Tir
30.5 1 GOO fy wes 11.7 minin GS ipa). This gradually
72 ouinin (6 Ips when the foam reached 207
ounl af foatn ¢ sed inthis fest
2148 gal:

syed tos indicated shat the advance rae of the Foarn
plug over the first 30.5 er (100 fi was 12% slower in a diry
culry than ing wel entry (theentey eas wetted before the te
more foam Conzemiate ia complete

miARG He Th
was (SEL OB

Aude

ful

also required 3S

foam. generator produced foam that
propagated up the entry (4.5% ri

cluding filling of a-crosseut, Afier the foarn

generator was tumied off. the f Yobe seaidd ttself
‘Fig 7).

Anotherexperiment was co:

ahrousl

wed verth the IETS ine 2.4

m high by 5.0m wide ( This was done to.
determine the rate of advan foun pig

chin d

and the distance the foun would tr
conditions before IPTS failure. The failure crtert
foarn leakage that rolis back over the foamy generator

hs advance rate of the foam for the firsr MES mr C100

y entry

a Was



the exiting foam side of the [FTS to the ribs). Also, tests will
be conducted to determine the effects of entry airflow on the
inflation process and stability of the IFTS in the entry. This
will include whether the dynamic force of the entry airflow
against the IFTS would be counterbalanced by the opposite
force exerted on the IFTS by the foam plug.

In addition, an evaluation will be made of foam generators
with larger driving forces interfaced to the IFTS to determine
the advance rate of the foam plug. Fabricating the IFTS from
other materials, such as Mylar, is also being considered. The
use of other nonporous materials may eliminate the need for
a continuous air supply after the bag is inflated. Tests will
also be conducted to evaluate the extinguishment of experi-
mental mine fires.

Summary

The IFTS was developed for use during an underground
mine fire to rapidly isolate the fire while providing a feed-
tube for a high-expansion foam generator. The first proto-
type validated the IFTS concept, providing a portable (light-
weight and easily transported), rapidly deployed (five to
eight minutes), partition with an integral aperture for passage
of a feed-tube from a high-expansion foam generator.

The second prototype IFTS included a wire insert to
maintain aperture opening. It also included an enlarged
aperture diameter that increased foam production efficiency.
The foam plug travel distance and rate were also significantly
improved.

The inflatable feed-tube seal offers a potential tool for
firefighters to rapidly fight fires in passageways with high-
expansion foam. As always, a fully implemented emergency
and preparedness plan is critical in dealing with and reducing
the probability of a mine fire. @

References

Conti. R.S., 1994, “Firesighting resources and fire preparedness for underground coal
mines,” US Bureau of Mines IC 9410, 23 pp.

Cont. R.S., and Lazzara, C.P., 1994, “Inflatable Partition for Fighting Mine Fires,” US
Patent Application Serial No. 08/148,310.

Havener, F.E., 1975, “Application of high-expansion foam to fight underground mine fires,”
Coal Age, February, Vol. 80, No. 2, pp. 144-147.

Jamison, W. B., 1893, Management Overview, Fighting A Coal Mine Fire, Jamison
Engineering, 26 pp.

Jamison, W.B., 1993, Operating Manual For Your High-expansion Foam Generator,
Jamison Engineering, 43 pp.

Jamison, W.B., 1993a, private communication.

Mattes, F.H., Bacho, A., and Wade, L.V., 1983, *Lake Lynn laboratory: Construction,
physical description and capability,” US Bureau of Mines IC 8911, 40 pp.

Mitchel, D.W., 1990, Mine Fires, Maclean Hunter Publishing Co., 167 pp.

Nagy. J.. Murphy, &.M., and Mitchell, D.W., 1960, “Controlling mine fires with high:
‘expansion foam,” US Bureau of Mines RI 5632, 28 pp.

Roberts, A.F., 1989, “Review paper: Mine fires,” Proceedings, 23rd International Conter-
‘ence of Safety in Mines Research Institutes, Washington, DC, Sept. 11-15, pp. 3-19.
Timko, Rd. Derick, F.L., and Thimons, E.D., 1987, “Analysis of a fire in a Colorado coal
mine — A case study,” ngs, 314 US Mine Ve ‘Symposium, University Park,
PA, Oct, 12-14, Ch. 63, pp. 444-452,

Triebsch, G.F., and Sapko, M.J., 1990, "Lake Lynn laboratory: A state-of-the-art mining

research laboratory.” Proceedings, (international) Symposium on Unique Underground
Structures, Denver, CO, June 12-15, Ch. 75, pp. 1-21



Inflatable partitions

for high-expansion foam generators

RS, Conti

Abstract — The US Bureau of Mines (USBM) has devel-
oped an inflatable feed-tube seal (IFTS) for high-expansion
foam generators. The IFTS is a lightweight, portable, rect-
angular inflatable bag that can be used by firefighters to
rapidly seal large openings, such as those in underground
mines, and to simultaneously provide a feed-tube for a high-
expansion foam generator. Thus allows fire-fighting foam to
freely flow to the fire site and control or extinguish the fire.
Studies indicated that a high-expansion foam plug will travel
183 m (600 ft) down an entry with a 4.5% rise in elevation,
before leakage of foam from around the inflatable partition.

Introduction

When an underground mine fire cannot be directly com-
batted due to heat, smoke or hazardous roof conditions, high-
expansion foam (HEF) may be one way to remotely quench
the fire. Foam is a convenient means of conveying water to
a fire (Havener, 1975). It quenches/extinguishes a fire by
diluting the oxygen concentration through the production of
steam. It blocks air currents to the fire and radiant energy
from the fuel (Nagy, Murphy and Mitchell, 1960). Water
retention is the most important property of any foam. The
more water the foam can retain, the better its fluidity, spread,
resistance to bubble collapse and ability to withstand the
effects of heat and products of combustion. High water
retention also means less foam is required,

As foam moves down an entry, a continuous shrinkage
process occurs. A foam bubble cannot exist touching a dry
surface. It will collapse, wetting the surface so that the next
foam bubble can replace it. As a foam plug advances, there
is aconstant bubble collapse. This shrinkage is not large and
takes place on the leading edge of the foam plug. It is also
useful, since the foam wets and cools all dry surfaces, thus
controlling or extinguishing the fire.

High-expansion foam cannot control a fire unless the
foam plug reaches the fire (Jamison, 1993). Attempts have
been made to push foam plugs into the burning entry down-
wind of the fire. However, the tremendous heat and gases on
the downwind side of the fire tend to break the foam and most
becomes heated into steam and blown down the entry away
from the fire. However, foam pushed into the fire on the
upwind side of the fire has a greater chance of reaching and
cooling the fire.

Time is critical when dealing with fire. It is imperative

that any ventilation change (Mitchell, 1990; Roberts, 1989)
be made with caution. High-expansion foam generators may
not produce quality foam (bubbles may not form) if the intake
air is contaminated with smoke (Jamison, 1993a).

In two recent mine fires, foam was successful in control-
ling the fire, at least temporarily. Ina fire that occurred in a
Colorado coal mine (Timko, Derick and Thimons, 1987),
miners started fighting the fire with an 1 1.3m?/sec (24,000 cu
ft/min) diesel-powered foam generator and 15 208-L (55-gal)
drums of foam concentrate. Additional foam concentrate
was obtained from several other mines and a local vendor.
Unfortunately, there was not enough of foam to quench the
fire. As soon as the foam was depleted control of the fire was
lost.

At the Montour No. 4 mine fire (Jamison, 1993b) in
Pennsylvania, foam was made for most of three days. More
than 15.1 kL (4000 gal) of foam concentrate and | ML
(270,000 gal) of water were depleted during that period. It
was stated that “The foam took over successfully at a critical
time and reduced one of the largest mine fires on record to a
safe sealing operation (Jamison, 1993b).”

To effectively use the foam method for remotely fighting
fires in underground mine entries, it may be necessary to
construct — some distance from the fire site — a partition or
seal in fresh air. This is done to separate the foam generator
and its operators from smoke and toxic fire products. In
addition to limiting exposure to smoke and toxicity, if a
partition is not constructed, foam could flow back over the
foam generator, rendering the fire attack futile. The problem
is especially acute when the fire is located uphill on a sloping
entry.

In past practice, concrete block, wood, plastic sheeting,
brattice or similar materials have been used for such parti-
tioning (Fig. 1). However, mine entries often have irregular
dimensions that the partition must conform to to avoid
leakage around the periphery. Building these partitions can
be time consuming. In addition, after the partition is made,
a hole must be cut to allow passage of the high-expansion
foam from the foam generator to the fire site. This can be
labor-intensive and time-consuming. It may also be danger-

R.S. Conti is an electronics engineer, US Bureau of Mines, Pitts-
burgh Research Center, Pittsburgh, PA. SME nonmeeting paper 94-
320. Manuscript July 1994. Discussion of this peer-reviewed and
approved paper must be submitted, in duplicate, prior to Sept. 30,
1995.


Fig. 2 — Inflatable partition for high-expansion foam generators.

high by 2.9 m wide or 6.5 x 9.5 ft).
Several limitations of using the foam
plug method included:

+ The time required to assemble the
equipment near the fire location.

+ The limited distance foam can be
transported, including up and down
sloping passageways.

+ Electrical power requirements
(fan motor used to produce foam) near
the fire area and the effect of the foam
plug on ventilation.

Despite these limitations, the un-
derground experiments indicated that
foam was effective in controlling or
extinguishing the fires.

Additional information on fire-
fighting resources and fire prepared-
ness for underground coal mines can
be found in reference (Conti, 1994).

Inflatable feed-tube seal

To address the problem of recon-
structing a partition, the inflatable feed-
tube seal (IFTS) was developed by the
USBM (Conti and Lazzara, 1994).
The IFTS is a lightweight, portable,
rectangular inflatable bag that is used
in conjunction with high-expansion
foam generators. It rapidly seals large
openings, suchas those inunderground
mines (Fig. 2). The IFTS can be
deployed in several minutes to simul-
taneously seal the entry and provide a
feed-tube for a high-expansion foam
generator.

The portable IFTS is easily trans-
ported to a burning mine passageway
and inflated by an air blower or other
source of compressed gas. The IFTS
seal is made from a water- and heat-
resistant, lightweight fabric (0.076 mm
or 0.003 in. thick), such as chemically

‘ous, depending on fire conditions (the accumulation of flam-
mable gases on the other side of the partition). The through-
hole in an improperly sealed partition often results in a
substantial leakage around the high-expansion foam feed
tube due to the backpressure of the advancing foam plug.

The erection of any partition reduces the ventilated
airflow and can cause the fire to burn fuel-rich. This
can be hazardous if the unburned volatiles are ignited.
Due to this potential explosion hazard, advance plan-
ning is essential, as is training and preassemblage of
correct materials (foam generator and concentrate, wa-
ter supply, partition, etc.). To minimize this hazard, the
use of the foam generator should occur immediately
following the erection of the partition.

Earlier tests conducted by the USBM (Nagy, Murphy and
Mitchell, 1960) using foam to control and extinguish experi-
mental underground coal, wood and oil fires indicated that a
foam plug could travel 488 m (1600 ft) in a level entry (2m

treated, rip-stop nylon. The shape and
size depend on the passageway dimensions. For example, for
a mine entry 2.1 m high by 5.8 m wide (7 x 19 ft), the seal
would take the shape of a slightly oversized rectangular bag
about 2.6 m high by 6.1 m wide and 3.1 m long (8.5 x 20x 10
ft), weighing 8.2 kg (18 Ibs).

Traversing the seal is a collapsible cylindrical aperture
lined with the fabric of the bag. A collapsible plastic feed-
tube is passed through the aperture to convey foam from one
side of the seal to the other. The pressure of the foam in the
tube will exceed the pressure of air in the seal. This keeps the
aperture open, When the foam generator is turned off, the
aperture collapses.

Figure 3 shows the inflatable feed-tube seal while being
deployed in a mine entry to contain a fire. The seal is air
inflated (to about 0.14 kPa or 0.02 psi) by a fan attached to the
seal with an air tube. When inflated, the seal blocks the entry
(Fig. 4).

‘A collapsible plastic feed-tube extends through the aper-


Fig. 5 — Inflated feed-tube seal coupled to the foam generator.

ture (about 3.1 m or 10 ft long). Atthis
stage, the aperture is collapsed, clos-
ing the aperture and the feed-tube. Air
pressure in the seal is maintained by
the fan and air tube. One end of the
collapsible plastic feed-tube is then
connected to the high-expansion foam
generator (Fig. 5). The generator ex-
pands the feed-tube due to the pressure
of the generator’s fan. This allows the
high-expansion foam to freely flow
through the seal, down the entry to the
fire site.

Experimental section

Experiments with high-expansion
foam and the IFTS were conducted at
the USBM’s Lake Lynn laboratory ex-
perimental mine (Mattes, Bacho and
Wade, 1983; Triebsch and Sapko,
1990). This isa former limestone mine
converted to a multipurpose mining
research facility for fire and explosion
prevention research. The entry dimen-
sions of the underground mine range
from 1.8 to 2.4 m high (6 to 8 ft) and
from 5.3 to 6.7 m wide (17 to 22 ft).
The average cross-sectional area is 12
m? (129 sq ft).

High-expansion foam tests. Tests
conducted in the Lake Lynn experi-
mental mine showed the required foam
concentrate necessary to produce suf-
ficient high-expansion foam to fill a
mine entry. The tests used a
2.8-m/sec (6000 cu ft/min) diesel-
powered, high-expansion foam gen-
erator with a 2% foam concentrate
solution (expansion ratio is 850:1). The
operating parameters were set at 3.15
L/sec (50 gpm) of water and 0.551
MPa (80 psi) water pressure at the
eductor. It required 2.2 minutes to fill
30.5 m (100 ft) of a 5.8 m wide by 2.1
m high (19 x 7 ft) entry, (372 m? or
13,300 cu ft). Therefore, in 1 hour,
11,356 L (3000 gal) of water and 227 L
(60 gal) of foam concentrate would be
used with this foam generator.

Tests in the Lake Lynn experimen-
tal mine also showed that a high-ex-
pansion foam plug traveled down and
completely filled an entry (with a4.5%
tise inelevation). Thisincluded across-
cut with the above dimensions. The
foam plug also traversed corners and
obstacles, such as wood cribs.

Using a plywood partition, the foam
spread 207 m (680 ft) before the parti-
tion failed (the failure criterion was
foam leakage from the foam feed tube
hole or around the partition, that rolled
back over the foam generator). Parti-