an experimental mean for an associated confidence
coefficient (6). For example, if a sample of 10 sprinklers
were leak pressure tested, the confidence interval with an
associated confidence coefficient could be calculated. If
the confidence coefficient is 95%, then there is a 95%
probability that the true average leak pressure would fall
in the confidence interval. The upper and lower limits of
the confidence interval, I, were calculated from the
expression

x Ss
1,=X+t,

where I, is the upper limit of the confidence interval, I, is
the lower limit of the confidence interval, X is the mean
of the leak pressures of the corresponding new sprinklers,
t, is the Student's statistic at the 100 - p confidence
interval, s is the standard deviation, and n is the number
of samples. This method was used to calculate the confi-
dence interval for the corresponding set of new sprinklers
for each type of sprinkler that had been exposed to the
mine atmosphere. If the individual leak pressure of each
exposed sprinkler did not fall into the confidence interval
of the corresponding new sprinklers, then there is a 95%
probability the exposed sprinkler was subjected to condi-
tions in the mine that reduced its ability to withstand high
static pressure. Each exposed sprinkler was evaluated in-
dividually since it could not be assumed that all of these
sprinklers were subjected to the same conditions, even if
they were from the same mine. Several of the exposed
sprinklers had been physically damaged and some were
extremely corroded. All were standard-response sprin-
Klers. Photographs of a few of the exposed sprinklers are
shown in figure 4.

The exposed sprinklers from mine 1 were 135° F
standard-response sprinklers from manufacturer A. These
sprinklers were in service in the mine for approximately 3
years. Three of the five sprinklers had deflectors that
were slightly damaged. This was probably the result of
being struck by a hard object, which could have also jarred
one of the linkage components that hold down the orifice
cap. The average leak pressure for the new sprinklers was
1,825+140 psig. The confidence interval for the new
sprinklers was from 1,700 to 1,950 psig. None of the leak
pressures of the exposed sprinklers fell into this range.
The leak pressures of the exposed sprinklers ranged from
1,000 to 1,500 psig. They were all mildly corroded and all
of the fusible elements were coated with a layer of caked
tock dust, The leak pressures of four of the five exposed
sprinklers were at least 40% lower than the average leak
pressure of the new sprinklers. This shows that exposure
to the environment at this particular mine had a significant
effect on the ability of these sprinklers to withstand high
static water pressure.

Mines 2 and 3 sent sets of exposed sprinklers that
were 212° F rated from manufacturer A. The set of ex-
posed sprinklers from mine 2 had been in service in the
mine about 3 years and had a range of leak pressures from
<100 to 2,000 psig. The deflector of the exposed sprinkler
that leaked before 100 psig could be applied was slightly
damaged but there was no other visual damage that would
indicate that the sprinkler could not hold 100 psig. The
sprinkler that held only 300 psig had no visual damage and
the sprinkler that held 500 psig had corroded to the point
where a reddish rust had started to form on the metal sur-
face. The two sprinklers that held 1,500 and 2,000 psig
were in the best condition of the sprinklers received from
this mine. The confidence interval for the new 212° F
sprinklers from manufacturer A was from 1,925 to 2,175
psig. Only the sprinkler that held 2,000 psig fell in the
confidence interval for the corresponding new sprinklers,
Three of the five exposed sprinklers were able to withstand
less than 25% of the average leak pressure of the corre-
sponding new sprinklers. The mine environment had a
significant effect on the ability of these sprinklers to
withstand static pressure.

The set of 212° F rated sprinklers from mine 3 were
from manufacturer A. They had been in service in the
mine about 2 years, and all of the sprinklers appeared to
be in good physical condition. The leak pressures ranged
from 900 to 1,700 psig. The three sprinklers that were
able to hold 900 and 1,000 psig had more rust and accum-
ulations in the orifice and were only able to withstand less
than half of the average leak pressure of the corresponding
new sprinklers.

The set of sprinklers from mine 4 were 212° F rated
sprinklers from manufacturer B. The 95% confidence in-
terval for the corresponding new sprinklers ranged from
955 to 1,090 psig. Two of the exposed sprinklers in this
set fell in the confidence interval for the corresponding
new sprinklers, and all of the leak pressures of the exposed
sprinklers were relatively close to the average pressure of
the corresponding new sprinklers. All of the sprinklers
were in good physical condition except for the sprinkler
that held only 600 psig, which had a damaged deflector.
Excluding this sprinkler, the remaining sprinklers were
able to withstand at least 88% of the average leak pressure
of the new sprinklers.

The sprinklers received from mine 5 were 212° F wax-
coated sprinklers from manufacturer B. The exposed
sprinklers had been in service for approximately 5 years
and were in good condition with little or no sign of dam-
age. The confidence interval for new sprinklers of the
same type was 1,075 to 1,165 psig. Two of the exposed
sprinklers fell in the confidence interval, while the other
three sprinklers were only able to withstand about 70% of
the average leak pressure of the corresponding new
sprinklers.


2

in?

UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT

degree Fahrenheit min minute

foot psig pound per square inch
gauge

inch

psig/min pound per square
cubic inch inch gauge per minute



APPENDIX

Table A-1.—Leak pressures of new sprinklers

Sprinkler Leak Sprinkler Leak
Manufacturer ‘Activation Type Pressure, |! Manufacturer Activation Type —~Pressure,
temp, °F psig temp, °F psig
A 135 $ 2,000 B 212 ‘SWC 1,200
A 135 s 1,900 B 212 SWC 1,100
A 135 s 1400 B 212 SWC 1,100
A 135 s 1,700 8 212 SWC 1,100
A 135 s 1700 B 212 SWC. 1,100
A 135 s 1,800 B 212 s,wC 1,200
A 135 8 1,800 B 212 swe 1,000
A 135 8 1,600 B 212 S.WC 1,100
A 135 s 2,000 8 212 s,wc 1,200
A 135 s 1,800 B 212 S,WC 1,100
A 165 F >2,300 c 135 S,GB 1,400
A 165 F >2,300 c 135 $,GB 700
A 165 F >2,300 c 135 $,GB 900
A 165 F >2,300 c 135 $,GB 800
A 165 F >2,300 c 136 F,GB 700
A 212 8 1,800 c 135 F,GB 700
A 212 s 2,200 c 135 F,GB 600
A 212 8 2,100 c 135 F,GB 500
A 212 s 2,200 c 135 F,GB 700
A 212 s 1,900 c 165 s 700
A 212 s 2,100 c 165 s 800
A 212 s 14,100 c 165 s 900
A 212 s 2,000 c 165 s 800
A 212 s 14,500 Cc 165 s 700
A 212 s 2,100 D 165 s 700
8 165 8 1,300 D 165 s 900
8 165 s 900 D 165 s 600
8 165 s 1,200 D 165 s 800
8 165 s 1,200 D 165 s 1,000
8 165 s 1,100 D 165 s 800
8 165 F 400 D 165 s 1,100
B 165 F 800 D 165 s 900
B 165 F 900 D 165 s 1,000
B 165 F 700 D 165 s 800
B 165 F 1,000 D 212 s 1,000
B 212 s 1,000 D 212 s 1,100
B 212 8 1400 D 212 s 1,000
B 212 s 1,200 D 212 8 1,100
B 212 s 1,000 o 212 8 1,000
B 212 s 1,000 io) 212 s 1,000
B 212 s 1,100 D 212 s 1,000
B 212 s 1,000 D 212 s 1,200
B 212 s 1,000 D 212 s 1,100
B 212 s 900 D 212 8 1,100
B 212 s 1,000

F Fast response.
GB Glass bulb.

‘WC Wax coated.
‘Outlier.


EXPERIMENTAL PROCEDURES

LEAK PRESSURE EXPERIMENTS

To conduct the leak pressure experiments, the release
valve on the hydraulic pump was opened to release any
pressure on the system. The quick-connect fitting on the
pump side of the tee fitting was disconnected. The
disconnected section was filled with water through the
fitting for the sprinkler and then the sprinkler was
installed. This section was reconnected to the system and
the release valve on the hydraulic pump was closed. The
pressure was quickly raised in the system to 100 psig and
held for 1 min, Thereafter the pressure on the system was
quickly raised another 100 psig and held for 1 min and the
system was monitored to determine if any leakage
occurred. This procedure was repeated until the sprinkler
leaked. Leakage was defined as more than one drop of
water per minute. At the end of the test, the pressure was
released, the end section of the system was disconnected,

and the sprinkler was removed. Any water or hydraulic oil
in this section was drained. The end section was refilled
with water and another sprinkler was installed.

LONG-TERM PRESSURE EXPERIMENTS

To conduct the long-term pressure tests, the pressure
gauge was installed in the end of the drop nipple with the
larger pipe diameter. The system was filled with water
and a sprinkler was installed. The pressure was raised by
screwing the smaller pipe into the larger pipe, thereby
decreasing the volume and increasing the pressure. The
pressure was raised to the desired point and the apparatus
was mounted on a stand. The apparatus was inspected
daily to check for leakage or change in pressure due to
temperature changes. Slight adjustments, if needed, were
made to the system to maintain the desired pressure for
30 days or until the sprinkler leaked.

RESULTS AND DISCUSSION

LEAK PRESSURE EXPERIMENTS
WITH NEW SPRINKLERS

Experiments were conducted, using the procedure pre-
viously described, on each set of new sprinklers to deter-
mine their leak pressure. The leak pressure is defined
as the maximum pressure the sprinkler could withstand for
1 min without leakage. For example, if the pressure was
raised to 700 psig and held for 1 min and the sprinkler did
not leak, but did leak while increasing the pressure to
800 psig, or the sprinkler could not withstand 800 psig for
1 min without leakage, then the leak pressure was reported
as 700 psig. The data were statistically analyzed to deter-
mine the mean, standard deviation, range, and median leak
pressure for each type of sprinkler. The results are shown.
in table 2, The data were also analyzed using Nalimov’s
Test, for each manufacturer, response type, fusible clement
type, and activation temperature, to determine if any
of the values showing large deviations from the mean val-
ue could be classified as outliers. An outlier is defined
asa data point that docs not fit the data population,

because of equipment malfunction, improper readings,
human error, or some other unknown reason, and may be
removed (5). Of the 89 new sprinklers that were eval-
uated, 5 were classified as outliers and were removed.
The data for cach type of sprinkler are given in the
appendix. The data show considerable variability, espe-
cially when comparing similar types of sprinklers from
different manufacturers and standard- and fast-response
sprinklers from the same manufacturers.

The leak pressures of the different types of new
sprinklers were compared with cach other using the com-
parison of means method. The Student’s t-test was ap-
plied to the hypothesis that the mean of the leak pressures
of the two sprinklers being compared were statistically
equivalent (6). If the hypothesis is accepted for a given
confidence level, 100 - p, there is a (100 - p)% probability
that the hypothesis is true, or that the average leak pres-
sures were equivalent. If the hypothesis is rejected, there
is a (100 - p)% probability that the average leak pressures
are not equivalent. The following comparisons used the
Student’s t-test at a 95% confidence interval.


INTRODUCTION

Automatic sprinkler systems are the primary method
of protecting lives and property from fire in aboveground
facilities. The demonstrated effectiveness of automatic
sprinkler systems along with their reliability and low
maintenance has lead to their increased used in under-
ground mines.

Federal regulations for underground coal mines require
that automatic sprinkler systems (wet pipe or dry pipe),
deluge-type water spray systems, foam generators, or dry
powder chemical systems be installed at all main and sec-
ondary conveyor belt drive areas in underground coal
mines. Sprinkler systems are required to provide pro-
tection for motor drive belt takeups, electrical controls,
gear reducing units, and the 50 ft of fire-resistant, or 150 ft
of non-fire-resistant, belt adjacent to the belt drive, and
sprinklers must be spaced at 8-ft intervals. Each individual
sprinkler shall be activated at a temperature of not less
than 150° F and not more than 300° F (see reference 1,
Part 75, Paragraph 1107-7).

The Federal regulations for underground coal mining
state that components of automatic sprinkler systems shall
be of a type approved by Underwriters’ Laboratories, Inc,
(UL), Factory Mutual Research Corporation (1) Sprin-
Klers must meet or exceed the performance criteria estab-
lished in UL Standard 199 to be listed by UL (2). In
regard to static pressure, UL Standard 199 states that an
automatic sprinkler shall not exhibit any visual leakage at
500 psig or less. In this test, the pressure is increased to
500 psig at a rate not to excced 300 psig/min and held for
1 min. The sprinkler must also be able to withstand,
without rupture, an increasing hydrostatic pressure up to
700 psig at a rate not to exceed 300 psig/min and held for
1 min. In addition, to test the long-term ability to with-
stand high static pressures, UL Standard 199 states that
automatic sprinklers shall not exhibit any leakage when
subjected to a hydrostatic pressure of 300 psig for 30 days.
To test the ability of automatic sprinklers to withstand
large, sudden increases in pressure, the standard states
that sprinklers shall withstand without leakage, 3,000
applications of a pressure surge increasing rapidly from
50 to 500 psig. Sprinklers that comply with the require-
ments of UL Standard 199 are rated at 175 psig. Manu-
facturers designed the sprinklers and the requirements
of UL Standard 199 were developed for these conditions,
However, the highest pressure that the sprinkler can
withstand is not determined. Currently, we do not know
if even a listed sprinkler can withstand the high static
pressure common in deep underground mines or if differ-
ent types of sprinklers from different manufacturers can

‘Sitalic numbers in parentheses refer to items in the list of references
preceding the appendix at the end of this report.

withstand higher pressures than other types of sprinklers
and from other manufacturers. Most commercially avail-
able sprinklers are designed so that the mechanical
pressure normally exerted on the top of the cap or valve
over the orifice is many times that developed by the water
pressure below, so that the possibility of leakage in
aboveground applications is practically eliminated (3).
Again, this is assuming that the sprinklers will be installed
and used under conditions for which they were designed.

However, in a deep underground mine, water supplied
from aboveground sources such as ponds, tanks, or reser-
voirs can result in pressures as high as 1,000 psig because
of the water head. The water head is developed at a rate
of 0.43 psig per foot of change in elevation. For example,
a mine 2,000 ft deep will develop a water head of 860 psig
in its water lines. Pressure-regulating valves are some-
times used to control high static and residual or flowing
water pressures in water systems in underground coal
mines; however, it is very important that the pressure
settings for these devices be correctly determined using the
manufacturers’ instructions. Pressure settings on these
devices are either set by the manufacturer or are field
adjustable. In either case, the valve inlet pressure, re-
quired outlet pressure, and required flow are necessary to
correctly set a pressure-reducing valve. Incorrect pressure
settings can cause inadequate water pressure and flow for
fire-fighting purposes. There are examples where incor-
rect settings of pressure-reducing valves severely hampered
fire-fighting efforts in aboveground installations, such as
during the fire at One Meridian Plaza, in Philadelphia, PA,
in 1990. This office high-rise fire killed three firefighters
and caused millions of dollars in damage (4). Therefore,
it is very important that pressure-reducing valves be in-
stalled, maintained, and periodically tested according to
manufacturers’ instructions.

In some cases, the water supply to an automatic sprin-
Wer system along a conveyor belt drive is also used to
supply water to the mining face for dust suppression and
cleanup. To obtain the needed pressures at the mining
face, a satellite pump may be used, which can generate
several hundred pounds of pressure at the sprinklers.
Using commercially available automatic sprinklers that are
listed with a working pressure rating of 175 psig in under-
ground mines under high static pressure may result in
sprinkler leakage or rupture. If the sprinkler ruptures
because of a large water hammer while someone is in the
area, there is a possibility of injury due to flying pieces
of metal. If the sprinkler ruptures while no one is in the
area, or if it leaks excessively, the waterflow alarm would
activate, resulting in a false alarm. This decreases the


EFFECT OF PRESSURE ON LEAKAGE
OF AUTOMATIC SPRINKLERS

By Mark W. Ryan,' Alex C. Smith,” Richard W. Pro,? and Charles P. Lazzara*

ABSTRACT

The U.S. Bureau of Mines conducted a study to determine if commercially available automatic
sprinklers could withstand the high static pressures in deep underground coal mines without leaking and
if exposure to the mine environment affected their leak pressures. New sprinklers and sprinklers
exposed to the mine environment were subjected to increasing pressures until leakage occurred. The
average leak pressures of the new sprinklers ranged from 640 to 2,300 psig and were significantly
different for sprinklers from different manufacturers and for different types of sprinklers.

Generally, standard-response sprinklers withstood higher pressures than fast-response sprinklers. The
results indicated that most commercially available sprinklers would withstand the high static pressures
in deep underground coal mines; however, they would not provide the same reliability and safety factor
as sprinklers used aboveground at or below their rated pressure of 175 psig.

The average leak pressures of the sprinklers exposed to the mine environment ranged from 740 to
1,180 psig. The mine environment affected the ability of 66% of the sprinklers to withstand high static
pressures.

New sprinklers were also evaluated at pressures of at least 500 psig for 30 days to determine their
ability to withstand long-term exposure to high static pressures; no leakage was observed.

1Fire prevention engineer.

2Research chemist.

Physical science technician.

‘Supervisory research chemist.

Pittsburgh Research Center, U.S. Bureau of Mines, Pittsburgh, PA.


EXPERIMENTAL APPARATUS

LEAK PRESSURE EXPERIMENTS

The leak pressure experiments were conducted using a
hand-operated, high-pressure hydraulic pump with high-
pressure hydraulic hose connected to a pressure gauge and
sprinkler. The hydraulic pump was capable of generating
pressure up to 10,000 psig and had a hydraulic oil reservoir
of 462 in’. The hoses were equipped with high-pressure,
quick-connect, spring-loaded fittings. Hydraulic hose ran
from the hydraulic pump to the sprinkler and pressure
gauge, which was mounted behind a Plexiglas acrylic sheet
shield. The hydraulic hose from the pump was connected
toa tee fitting. The tee fed a bourdon-tube-type pressure
gauge on one end while a section of hydraulic hose with an
adaptor and 0.5-in pipe nipple on the other end was used
to connect the sprinkler to the hydraulic system. The
pressure gauge measured pressures from 0 to 2,300 psig in
graduations of 20 psig, A photograph of the leak pressure
experimental apparatus is shown in figure 2.

Figure 2.—Experimental apparatus used in leak pressure
experiments.

LONG-TERM PRESSURE EXPERIMENTS

The long-term pressure experiments were conducted
using an adjustable drop nipple, a bourdon-tube-type
pressure gauge, and the sprinkler. The adjustable drop
nipple consists of two sections of pipe; one section, smaller
in diameter, is threaded into a larger diameter section. An
O-ring seals the threaded connection. The open ends of
the two sections of pipe have female pipe threads. The
end of the smaller diameter pipe is 0.5-in, female NPT so
that the sprinkler can be inserted. An adaptor and the
pressure gauge were placed on the other end. Three
sprinklers were tested simultaneously using three
adjustable drop nipples and three pressure gauges. One
pressure gauge read from 0 to 2,300 psig with 20-psig
graduations, and the other two read from 0 to 1,500 psig
with 10-psig graduations. A photograph of the apparatus
used in the long-term pressure experiments is shown in

figure 3.

Figure 3.—Experimental apparatus used in long-term pressure
experiments.


RI| 9451 | = REPORT OF INVESTIGATIONS/1993

Effect of Pressure on Leakage
of Automatic Sprinklers

By Mark W. Ryan, Alex C. Smith, Richard W. Pro,
and Charles P. Lazzara

_ UNITED STATES DEPARTMENT OF THE INTERIOR |



Comparison of Sprinklers From Same Manufacturer

Next, automatic sprinklers from the same manufacturer
with the same response type and fusible element design,
but different activation temperatures, were compared. The
average leak pressure of the 135° F and 212° F standard-
response sprinklers from manufacturer A were 1,825+140
and 2,050+140 psig, respectively. Although these values
are very similar and are within 11% of each other, they
were not determined to be statistically equal by the t-test.
However, the relatively high values indicate that both
sprinklers would be able to withstand high static water
pressures,

The average leak pressures of the 165° F and 212° F
standard-response sprinklers from manufacturer B were
1,140+150 and 1,022+83 psig, respectively. The average
leak pressures of these sprinklers were determined not to
be statistically equivalent. The average leak pressures of
the 165° F and 212° F sprinklers from manufacturer D
were 860+150 and 1,060+70 psig, respectively. It was
determined that the average leak pressures of these sprin-
Klers were not statistically equivalent.

These comparisons show that different activation
temperatures within a particular manufacturer have some
effect on the ability of sprinklers to withstand high static
pressures. In all of the comparisons, the values were
similar and within at least 20% of cach other; however,
none were found to be statistically equivalent. The small
differences were expected because the manufacturer,
response type, and fusible element design were all the
same. The activation temperatures of the sprinklers were
the only variable in these comparisons. The activation
temperature is controlled by the small amount of metal
alloy that holds the fusible element together, which may
have affected the sprinkler’s ability to withstand pressure.
The melting temperature of the metal alloy can be
changed by the composition of the alloy, which may
change its strength.

Comparison of Standard- and
Fast-Response Sprinklers

The average leak pressures of standard- and fast-
response sprinklers from the same manufacturer with the
same activation temperature, but different fusible clement
design, were also compared to determine if there is a dif-
ference in their leak pressures. The release mechanisms
of fast-response sprinklers are more sensitive to heat,
therefore activating in a shorter period of time than
standard-response sprinklers at a given activation tem-
perature. The average leak pressures of the 165° F
standard- and fast-response sprinklers from manufacturer
B were 1,140+150 and 760+230 psig, respectively. ‘The
average leak pressures of the standard- and fast-response

sprinklers from manufacturer B were determined not to be
equal at a 95% confidence level. The average leak pres-
sures of the 135° F glass-bulb, standard-response sprinklers
and the 135° F glass-bulb, fast-response sprinklers from
manufacturer C were 950310 and 64090 psig, respec-
tively. However, the Student’s t-test determined that the
average leak pressures of these sprinklers were equivalent
at a 95% confidence level. This is attributed to the large
standard deviation of the standard-response sprinkler.
Overall, the fast-response sprinklers had average leak
pressures lower than those of standard-response sprinklers.
The only exception to this is the fast-response sprinklers
from manufacturer A, which at greater than 2,300 psig had
the highest average leak pressure of any of the sprinklers
tested. The fusible clement design of these sprinklers was
dramatically different from the other sprinklers, and may
have been responsible for the differences in leak pressures.

Comparison of Glass-Bulb- and
Fusible-Type Sprinklers

The 135° F standard-response glass-bulb sprinklers from
manufacturer C and 135° F standard-response fusible-type
sprinkler from manufacturer A were compared to deter-
mine if there is a difference in their leak pressures due to
the activation mechanism. The average leak pressures of
1,825 + 140 psig for the sprinkler from manufacturer A and
950+310 psig for the sprinkler from manufacturer C were
significantly different. The average leak pressures were
determined not to be statistically equivalent. As men-
tioned above, the sprinklers from manufacturer A had the
highest average leak pressures compared with those from
the three other manufacturers, so the glass-bulb sprinklers
were also compared with other fusible-type standard-
response sprinklers with different activation temperatures,
The 135° F standard-response glass-bulb sprinklers from
manufacturer C were compared with the 165° F standard-
response fusible sprinklers from manufacturers B and D.
The Student’s t-test determined that the average Icak
pressures of all of these sprinklers were statistically
equivalent to each other at the 95% confidence level.
Although the leak pressures of the sprinklers were deter-
mined to be equal, the high standard deviation of the
glass-bulb sprinklers also shows the variability associated
with sprinklers of this type and manufacturer.

Comparison of Wax-Coated Sprinklers

The average leak pressures of the 212° F sprinklers
from manufacturer B and the wax-coated version of those
sprinklers were also compared. They were found to be
similar at 1,022+83 and 1,120+65 psig, respectively. The
wax coating, as expected, had a minimal effect on the
sprinkler’s leak pressure.


Table 2.Results of leak pressure experiments with new sprinklers

Sprinkler Mean, Standard ‘Range, ‘Median,
Manufacturer Activation ‘Response Comments No. tested psig deviation, psig psig
temp, °F type psig
A 135 s NAp 1g 1,825 140 1,600-2,000 1,800
A 165 F NAp 5 >2,300 NAp >2,300  >2,300
A 212 s NAp 1g 2,050 140 1,800-2,200 2,100
B 165 s NAP 5 1,140 150 900-1,300 1,200
8B 165 F NAp 5 760 230 400-1,000 800
8 212 s NAp 1g 1,022 83 900-1,200 1,000
B 212 s we 10 1,120 65 —1,000-1,200 1,100
c 135 s GB 4 950 310 700-1,400 850
Cc 135 F Ga 5 640 90 500- 700 700
Cc 165 s NAp 10 780 85 700- 900 800
D 165 s NAp 10 860 150 600-1,100 850
D 212 s NAp 10 1,060 70 1,000-1,200 1,050

F Fast response.

GB Glass bulb.

NAp Not applicable.

$ Standard response.
WC — Wax coated.
‘Excludes outliers.

Comparison of Similar Sprinklers
From Different Manufacturers

First, the leak pressures of the automatic sprinklers with
the same activation temperature, response type, and fusible
element type, but different manufacturers, were compared.
Although the fusible element type was the same for
sprinklers that were compared, the engineering design,
manufacturing process, and materials of the fusible
elements were different for each manufacturer. The aver-
age leak pressures of the 165° F standard-response sprin-
Klers from manufacturers B, C, and D were 1,140+150,
78085, and 860+150 psig, respectively. The data were
consistent for each set of sprinklers, as indicated by the
low standard deviation, indicating good reproducibility
within a sprinkler type from the same manufacturer.
However, there was a noticeable difference in the average
leak pressure of the sprinklers from different manufac-
turers. The leak pressures of the sprinklers from manu-
facturers C and D were determined to be statistically
equal, while the leak pressures of the sprinklers from
manufacturer B were shown to be statistically higher.

The average leak pressures of the 212° F standard-
response sprinklers from manufacturers A, B, and D were
2,050+140, 1,022+83, and 1,060+70 psig, respectively.
The average leak pressures for sprinklers from manufac-
turers B and D were determined to be statistically equal.
The average leak pressure for the 212° F sprinklers from
manufacturer A was double the average leak pressure of
the sprinklers from manufacturers B and D.

The average leak pressures of the 165° F fast-response
sprinklers from manufacturers A and B showed a signifi-
cant difference. The sprinklers from manufacturers A and
B had average leak pressures of greater than 2,300 and
760 +230 psig, respectively. The limit of the gauge used in
the test apparatus was 2,300 psig, and all of the sprinklers
tested from manufacturer A were able to withstand at
least that pressure without leaking. Obviously, the 165° F
fast-response sprinklers from manufacturers A and B were
determined not to be statistically equal. The 165° F fast-
response sprinkler from manufacturer A also had the high-
est average leak pressure of all the sprinklers tested.

These comparisons show that there is definitely a
difference in the ability of sprinklers from different
manufacturers to withstand high static water pressure.
The difference in their ability to withstand high static
pressures is most likely the design of the fusible element
and the materials used in the fusible element. The design
of the fusible element of the sprinklers and most likely the
materials used were different for each manufacturer, as
well as different for the standard- and fast-response
sprinklers from the same manufacturer. The sprinklers
from manufacturer A were able to withstand much larger
static pressures than sprinklers from the other three
manufacturers. The sprinklers from manufacturers B and
D were essentially equivalent to each other; however, they
were able to withstand only half of the pressure withstood
by the sprinklers from manufacturer A. Sprinklers from
manufacturer C had the lowest average leak pressures of
the four manufacturers tested.


reliability of the sprinkler system, increases maintenance
of the system, and discourages the use of automatic sprin-
Kler systems in areas other than those currently required
by Federal regulations, such as haulageways and along
longwall faces.

In this report, the U.S. Bureau of Mines examined the
ability of commercially available sprinklers to withstand
the high static water pressures typical in deep underground
coal mines. This work is part of a larger program to

evaluate the effects of the underground mining environ-
ment on the performance of automatic sprinkler systems.
The larger program also includes examining the effect of
the mine environment, ventilation, response time index
(RTD), temperature rating, and fire size on the activation
time of sprinkler systems. The results obtained from this
program will help the Bureau to improve fire safety in the

mining industry, thus enhancing the safety of the Nation’s
miners.

SPRINKLERS

The leak pressures of 12 different types of new, com-
mercially available automatic sprinklers from four different
manufacturers (designated as manufacturers A, B, C, and
D) were evaluated. Also, six types of automatic sprinklers
that had been exposed to the underground coal mine envi-
ronment were evaluated. These exposed sprinklers were
obtained from nine different mines and had been installed
in the mines for different lengths of time, ranging from
1to 5 years. Table 1 shows the sprinklers that were
tested.

Table 1,—Automatic sprinklers tested!

Manufacturer Activation Response Comments No.
temp, °F type tested
Rovere 135 $s EH, LT 10
165 F ur 5
212 8 EH 10
Bees 165 s ut 5
165 F ut 5
212 8 EH 10
212 s WC, EH 10
Coes 135 8 GB, LT 4
135 F GB 5
165 s ut 5
Deveeeeee 165 s EH 10
212 s EH 10

EH Exposed sprinklers tested also.

F Fast response.

Glass bulb.

LT Long-term tested.

S Standard response.

Wax coated.

{Unless noted, all sprinklers were fusible type.

Six types of new sprinklers that were evaluated were
chosen to correspond to the six types of exposed sprinklers
that were received from the operating mines. The other
six types were chosen to give a broad range of sprinklers

available, as far as response type, activation temperature,
activation mechanism (glass bulb or fusible link) and
manufacturers. All of the sprinklers had 0.5-in orifices
and 0.5-in National Pipe Threads (NPT). All of the
sprinklers, except as noted in table 1, were of the fusible
type. Fusible-type sprinklers usually use an arrangement
of links and levers that are soldered together and held
over the sprinkler orifice cap by the frame arm. As the
increased temperature of a fire causes the solder to melt,
the links and levers separate and release the cap over the
sprinkler orifice, allowing water to discharge and strike the
deflector. The glass-bulb sprinklers use a frangible bulb
that is partially filled with a liquid, leaving a small air
bubble. Heat causes the bubble to be compressed into the
liquid and the pressure to rise until the bulb shatters. This
releases the cap over the sprinkler orifice, allowing water
to discharge and strike the deflector. Examples of fusible-
and glass-bulb-type sprinklers are shown in figure 1.

Figure 1—Examples of glass-bulb (A) and fuslble-type (8)
sprinklers.


CONTENTS

Abstract .
Introduction .
Sprinklers . . .
Experimental apparatus
Leak pressure experiments .......
Long-term pressure experiments .. .
Experimental procedures ....
Leak pressure experiments . .
Long-term pressure experiments .. .
Results and discussion ..... sbeeees
Leak pressure experiments with new sprinklers .
Comparison of similar sprinklers from different manufacturers
Comparison of sprinklers from same manufacturer ... .
Comparison of standard- and fast-response sprinklers . .
Comparison of glass-bulb- and fusible-type sprinklers
Comparison of wax-coated sprinklers ..........
Long-term pressure experiments with new sprinklers .
Leak pressure oxperiments with exposed sprinklers .
Pressure ratings .
Conclusions .
References
Appendix .

ILLUSTRATIONS

Examples of glass-bulb and fusible-type sprinklers . .
Experimental apparatus used in leak pressure experiments . .

Experimental apparatus used in long-term pressure experiments
Examples of exposed sprinklers .

PYnNr

Automatic sprinklers tested ...... beeen ene eens bees
Results of leak pressure experiments with new sprinklers ..
Results of leak pressure experiments with exposed sprinklers .
Leak pressures of new sprinklers

Per

Page

Beaowwayanunnnaeaune


oo

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es

Figure 4.Examples of exposed sprinklers. A, Damaged sprinkler; B, damaged sprinkler; C, exposed sprinkler (left) versus new
sprinkler (right); D, sprinkler plugged with pipe scale, stones, and/or other foreign material,

Mines 6 and 7 sent sets of exposed 165° F standard-
response sprinklers from manufacturer D. Mine 6 sent
five sprinklers and mine 7 sent two sprinklers. The con-
fidence interval for the new 165° F standard-response
sprinklers from manufacturer D was from 750 to 970 psig.
In the set with five sprinklers, the leak pressures ranged
from <100 to 1,300 psig. The sprinkler that leaked before
100 psig could be applied had a damaged deflector and
damage and rust around the orifice cap and upper portion

of the threads. This indicates that this sprinkler may have
been leaking while in service in the mine. The deflector
of the sprinkler that was able to hold only 600 psig was
severely damaged and could be made to spin on the frame
arm, The leak pressures of the other three sprinklers
were 900, 1,000, and 1,300 psig, which cither fell in or
exceeded the pressures specified by the confidence inter-
val. These sprinklers were in good condition. Unless
physically damaged, cxposed sprinklers from this mine


operated as designed. The mining environment had a sig-
nificant effect on the ability of these sprinklers to
withstand high static pressures.

The results of the leak pressure experiments indicate
that most of the automatic sprinklers evaluated would not
leak when subjected to pressures found in deep under-
ground mines. However, automatic sprinklers installed in
deep underground coal mines can be exposed to three
times their rated pressure of 175 psig. This leaves only a
small safety factor between the average leak pressure and

the pressure to which the sprinkler is exposed. The sprin-
klers are exposed to an environment where physical dam-
age and harsh atmospheric conditions are likely. Because
of these factors, consideration should be given to devel-
oping performance standards for existing sprinklers that
can withstand high static pressure or designing new sprin-
klers to be used under high static pressures in under-
ground coal mines. This would ensure that sprinklers used
underground provide the same reliable, low-maintenance
fire protection that they provide aboveground.

REFERENCES

1. US. Code of Federal Regulations. Title 30—Mineral Resources;
Part 75—Mandatory Safety Standards—Underground Coal Mines; Sub-
paragraphs 75.1100 and 75.1101; July 1, 1988.

2. Underwriters Laboratories Inc. (Northbrook, IL). UL 199, Stand-
ard for Automatic Sprinklers for Fire-Protection Service. 7th ed., 1982,
p. 40,

3. Fleming, R. Automatic Sprinklers. Ch. in Fire Protection Hand-
book, ed. by A. E. Cote and J. L. Linville. Nat. Fire Protect. Assoc.,
17th ed., 1991, pp. 5-174 to 5-185.

4, Klem, T. High-Rise Fire Claims Three Philadelphia Fire Fighters.
NFPA J,, v. 85, No. 5, 1991, pp. 64-89.

5. Anker, A. Detection of Outliers by Means of Nalimov’s Test.
‘Chem, Eng,, Aug. 1984, pp. 74-75.

6. Luckas, E. Probability and Mathematical Statistics, An Intro-
duction. Academic, New York, NY, 1972, 242 pp.


Library of Congress Cataloging in Publication Data:

Effect of pressure on leakage of automatic sprinklers / by Mark W. Ryan ... [et al].
Pp. cm. — (Report of investigations; 9451)

Includes bibliographical references (p. 12).

1. Mine firesPrevention and control. 2. Fire sprinklers—Testing, 3. Water

Jeakage—Measurement. I. Ryan, Mark W. II Series: Report of investigations
(United States. Bureau of Mines); 9451.

TN23.U43 [TN315] 622 s—de20_[622’.82] 92-28895 CIP



Report of Investigations 9451

Effect of Pressure on Leakage
of Automatic Sprinklers

By Mark W. Ryan, Alex C. Smith, Richard W. Pro,
and Charles P. Lazzara

UNITED STATES DEPARTMENT OF THE INTERIOR
Manuel Lujan, Jr., Secretary

BUREAU OF MINES
T S Ary, Director


LONG-TERM PRESSURE EXPERIMENTS
WITH NEW SPRINKLERS

In the long-term pressure experiments, six of the dif-
ferent sprinklers were able to withstand at least 500 psig
for 30 days without leakage. As mentioned earlier, UL
standards require sprinklers to withstand a pressure of
300 psig for 30 days to be listed. The 135° F standard-
response and 165° F fast-response sprinklers from manu-
facturer A were able to withstand at least 1,000 psig for
30 days. The 165° F standard-response sprinkler from
manufacturer B was able to withstand at least 1,000 psig
for 30 days, while the 165° F fast-response sprinkler from
manufacturer B was able to withstand at least 500 psig for
30 days. The 165° F standard-response, fusible sprinkler
from manufacturer C was able to withstand 500 psig for
30 days, while the 135° F standard-response, glass-bulb
sprinkler from manufacturer B was able to withstand at
least 750 psig for 30 days. These experiments also showed
the difference between the sprinklers from the four manu-
facturers, as both of the sprinklers from manufacturer A
were able to withstand at least 1,000 psig for 30 days.
Also, for each manufacturer, except A, the standard-
response sprinkler was able to withstand a higher static
pressure than the fast-response sprinkler for the 30-day
period.

The results of the leak pressure experiments with the
new sprinklers showed that the manufacturer was the most.
significant factor when comparing an automatic sprinkler’s
ability to withstand high static pressures typically found in
deep underground coal mines. This is probably due to the
difference in the design, materials, and manufacturing
procedure of the fusible elements. The sprinklers from
manufacturer A were clearly superior in their ability to
withstand high static pressure. The sprinklers from manu-
facturers B and D were essentially equivalent to each
other; however, they were able to withstand only half of
the pressure withstood by the sprinklers from manufac-
turer A. Sprinklers from manufacturer C had the lowest
average leak pressures of the four manufacturers tested.
The response type, standard or fast, was also found to
have a significant effect on the sprinkler’s ability to with-
stand high static pressures.

LEAK PRESSURE EXPERIMENTS
WITH EXPOSED SPRINKLERS

Leak pressure experiments were conducted on auto-
matic sprinklers obtained from nine different operating
coal mines. The sprinklers were exposed to the mine
environment for periods ranging from 1 to 5 years. The
results of these experiments are shown in table 3.

Table 3.—Results of leak pressure experiments
with exposed sprinklers

(All sprinklers standard response)

Sprinkler Leak Confidence
Manufacturer Activation pressure, —_ interval,’
temp, °F psig psig

1... A 135 1,000
1,000 1,700-1,950

Mine

1,500
1,000
<100
1,500
500 > 1,925-2,175
300
2,000
3... A 212 900
1,000

1,400

900

1,700

4. B 212 600
1,100

1,200

900

7212 900
1,100

1,100

900

800

6... D 165 900
<100
1,300
600
1,000
1,000,

v0 > 750- 970

1,200
900 1,010-1,110

900
8... D 212 900
1,000
1,100
1,100
900
1,000
600
900 > 1,010-1,110
1,100
1,000

1,925-2,175

955-1,090

1,075-1,165

750- 970

1,010-1,110

‘Confidence interval of the average
tresponding new sprinklers; confidence coefficient of 95%.
Wax coated.

The leak pressures of the exposed sprinklers were
compared with the confidence interval of the average leak
pressure of the corresponding new sprinklers, The confi-
dence interval method determines a confidence interval for


were not affected by the mine atmosphere. The two
165° F sprinklers from mine 7 were in relatively good
condition and either came close to the lower limit or
exceeded the confidence interval.

Mines 7, 8, and 9 provided sets of exposed 212° F
standard-response sprinklers from manufacturer D, The
confidence interval for the new 212° F sprinklers from
manufacturer D was between 1,010 and 1,110 psig. The
set from mine 7 contained three sprinklers and all were in
good condition, The leak pressure of one of the sprinklers
exceeded the confidence interval, while the other two were
close to the lower limit of the interval. The effect of the
environment of this mine on these sprinklers was minimal,

In the set from mine 8, the leak pressure of two of the
five sprinklers fell in the confidence interval and the other
three were close to the confidence interval. These sprin-
Klers had been in the mine approximately 2 years and all
were in good condition. The effect of the mine environ-
ment on the performance of these sprinklers was not

ificant.

In the set from mine 9, one of the sprinklers fell in the
confidence interval; however, one of the other four sprin-
Klers was able to withstand only 600 psig. The deflector
on this sprinkler was severely damaged, which could be the
reason for its poor performance. The mine environment
was definitely a factor in the performance of this sprinkler,
although the effect on the rest of sprinklers was not as
obvious.

Overall, the leak pressures of 66% of the sprinklers
received from underground mines did not fall into the con-
fidence interval for their corresponding new sprinklers,
indicating a reduction in their ability to withstand high
static water pressure. For seven of the nine mines from
which sprinklers were obtained, the sprinklers that did not
fall into the confidence interval had leak pressures, on the
average, 20% less than the average leak pressures of their
corresponding new sprinklers. Considering that these
sprinklers had been installed in the mine for no more
than 5 years, and on the average 2 or 3 years, the mine

environment had a significant effect on the automatic
sprinklers’ ability to withstand high static pressure.

In several cases, the exposed sprinklers that did not
withstand high static pressures were physically damaged,
while in other cases the sprinklers looked no different than
the other sprinklers from that mine. Because of the poor
visibility and cramped conditions in an underground coal
mine, sprinklers installed in mines are more susceptible to
being struck by various objects. Sprinkler guards are avail-
able and should be used where this is a problem. Also,
the sprinklers may be subjected to large water hammers in
an underground water system. This may reduce their abil-
ity to withstand high static pressures while causing no
visible physical damage to the sprinkler. If the sprinklers
are physically damaged, they should be replaced as soon as
possible. For some of the exposed sprinklers, in addition
to the poor performance in the leak pressure experiment,
the physical damage of the deflector would have adversely
affected the discharge pattern of the sprinkler.

PRESSURE RATINGS

The average leak pressures of the new automatic
sprinklers evaluated in this study were much greater than
their rated pressures. However, the average leak pressures
were not high enough to provide sprinklers used in deep
underground mines the same safety factor as sprinklers
used aboveground at or below their rated pressures. For
a sprinkler to be UL listed with a 175-psig maximum
working pressure rating, it must withstand 500 psig without
leakage. To provide the same safety factor, a sprinkler
with a 400-psig maximum working pressure rating would
have to withstand at least 1,145 psig without leakage. Of
the 12 types of new sprinklers evaluated in this study, only
4 sprinklers had an average leak pressure of at least
1,140 psig. It is safe to assume that the remainder of
these sprinklers would not be able to withstand the
pressure needed to be listed with a 400-psig maximum
working pressure rating.

CONCLUSIONS

Experiments were conducted to evaluate the effects of
high static water pressure on the performance of commer-
cially available automatic sprinklers. Different types of
new automatic sprinklers from four different manufactur-
ers were compared as well as automatic sprinklers that
had been exposed to the mine environment. The average
leak pressures of the new sprinklers ranged from 640 to
2,300 psig and showed a statistically significant difference
between sprinklers from different manufacturers, as well
as between different types of sprinklers. Generally, the
standard-response sprinklers were able to withstand higher

static pressure than the fast-response sprinklers. The
average leak pressures of the standard-response sprinklers
ranged from 780 to 2,050 psig, the fast-response sprinklers
from 640 to >2,300 psig. In addition to the leak pressure
experiments, six types of sprinklers were able to withstand
at least 500 psig for 30 days without leaking.

The leak pressures of 66% of the sprinklers received
from nine underground coal mines did not fall into the
confidence interval for their corresponding new sprinklers.
In addition, several of the sprinklers obtained from the
mines were physically damaged and would have not