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14DEFINITION OF ELASTIC PROPERTIES OF FIRE HOSES OF TYPE "T" WITH A
DIAMETER OF 51 MM UNDER TORSION
Larin А.N.
doctor of the sciences, professor National university of civil protection of Ukraine
Chernobay G.A. candidate of sciences, associate professor National university of civil protection of Ukraine
Nazarenko S.Y. doctoral student National university of civil protection of Ukraine
Lipovоy V.А. lecturer
National university of civil protection of Ukraine
ABSTRACT
It is found that mechanical properties, including torsional rigidity of a fire hose, determine it's long-term safe operation. The paper contains results of experimental studies, namely the elasticity properties of the fire hose and torsional rigidity. Research was carried out at an internal pressures of 0.2 Mpa, 0.6 Mpa and 0.4Mpa in a hose that was provided by the compressor. Five loading cycles with two minute intervals were held. The loading was measured via dynamometer. Experimental fragment of the fire hose with an inner diameter of 51 mm and testing length of0.985 m was set on a research facility and a series of tests were held. The results show material stabilization on the 3rd cycle of loading. Experimental results are presented graphically by curves. As a result of present work the torsional rigidity of the fire hose of type "T" with an inner diameter of 51 mm is determined. The obtained results will be used to estimate the residual life of the fire hose.
Key words: hose, pressurized fire hose, working pressure, experiment, rigidity, torsion, elasticity modulus
Formulation of the problem. Pressurized fire hoses are flexible pipelines used for submitting pressurized water and aqueous solutions of fire extinguishing agents, including foamers on a distance. Pressurized hoses, along with other fire equipment, is one of the main types of fire arms and their working state effects largely on the success of fires extinguishing. A high cost of fire hoses determines the appropriate amortization expenses operating hoses sector, which in most cases exceeds the cost of other types of fire equipment operating expenses. Thus measures aimed at determining the residual life of fire hoses, the possibility of repair, reliability and safety of subsequent operation greatly enhance the firefighting capability of fire departments and their operation economic efficiency.
Analysis of recent research and publications. The design of fire hoses, their sizes and characteristics, application areas, operating conditions and experimental methods listed in the corresponding regulations [1]. Analysis of literature related to the calculation methods of pressurized fire hoses showed that they are mostly concentrated on calculation of pressure losses in
air/mm the compressor with pressure P
the network [2-5]. The results of theoretical and experimental research of strength of bearing elements of the pressurized fire hoses, namely reinforcing frame that is fully perceiving the loading due to the presence of the internal hydraulic fluid pressure inside the hose are shown in [6-9].
Problem statement and it's solution. Some features of fire hoses in a real-life operation that significantly affect their reliability especially during long periods of use generated the need to develop scientifically grounded method that allows to determine the residual life of a fire hose, the possibility and necessity of its repair and subsequent use. When carrying out preliminary theoretical and experimental work on the subject of the residual life of fire hoses necessity to determine their mechanical properties including torsional rigidity under static load appeared. To conduct the relevant experimental research work the research facility shown in Figure 1 was used. The facility was mounted in the laboratory of the department of engineering and rescue machinery of the National University of Civil Defence of Ukraine.
fragment of the fire hose
definition of a corner of a twisting ^
loading F >
Figure 1 - Research facility with the mounted fragment of the fire hose
The experimental piece of fire hose of type "T" with internal diameter d = 51 mm, wall thickness 5 = 1.5 mm and test length L = 0.985 m was mounted vertically by relevant devices and a series of twisting tests relatively to the longitudinal axis on an angle 9 with steps of 600 under the action of torque mk, which is the product of the load force F (defined by dynamometer)
and length of the lever R = 0.281 m conducted.
The research was carried out at an internal pressure in a hose (P) P1 = 0.2 MPa, P2 = 0.4 MPa and P3 = 0.6 MPa, which was provided by the compressor, with the five-fold repetition load (modes 1 - 5).
Experimental results at P1 = 0.2 MPa are shown in table 1.
Table 1
Angle of twist deg Pressure in a hose, P1 = 0.2 MPa
Torque mk, Nm
Mode 1 Mode 2 Mode 3 Modes 4-5
0 0.00 - - -
60 1.82 - - -
120 2.65 - - -
180 3.69 0.00 - -
240 5.10 2.92 0.00 -
300 6.56 4.63 2.98 0.00
360 7.94 6.23 4.25 3.34
420 9.59 7.72 6.06 4.80
480 11.0 9.37 7.66 6.04
540 12.1 11.3 9.37 7.58
600 - 14.3 12.1 9.57
660 - - 14.8 13.3
720 - - 16.6 15.9
780 - - - 17.5
The basic (1) mode of loading was conducted on an undeformed fragment of the fire hose. The maximum
value of deformation was AÇ™* = 540° under the load Mtmax=12.1Nm After unloading the residual deformation of
the fragment was AÇ = 180°.
During the repeated loading (2), which was held in two minutes after the first, the maximum value of deformation
was Ap^ = 480° under the load M3max=16.6Nm After unloading the residual deformation of the fragment was Aq>3res=600 The numerical parameters of the following loading modes (4-5), that were conducted with the same two-minute intervals do not differ from one another allowing to average their values. The maximum value of deformation
under the load
M cmax=17.5Nrn After
4-5
M2max=14.3Nm After
was AçÇm^ = 420° under the load unloading the residual deformation of the fragment was Aç>2res=60°
During the third loading (3), which was held in two minutes after the second, the maximum value of deformation
was A<5 = 480 unloading the residual deformation of the fragment was Aq>4
5res=600
Diagrams corresponding to the experimental results under the internal pressure in a hose P1 = 0.2 MPa are shown in Figure 2.
24 H
22
¿0
10 -
Lft ■
z 14 -
O - I? ID ■
£ e ■
1 Mitdeal
■J1= ivLra \ \
— 1 \ 1
\ 1 j
/ M
OT/
U J[
V V c • v Yrr
w -| M odes J -5
is r -1 /
0 to 13« ISO 380 360 541 (00 IV«) 750 780 040
Twisting comer, dcg
Figure 2 - Diagram of loads of the test fragment of fire hose under torsion (pressure in a hose P1 = 0.2 MPa)
If we take a relationship between load and deformation of the fire hose fragment under torsion to be linear in first approximation, it's average rigidity can be defined:
modes 4-5
^ = 0.0365 . 480 deg
mode 1
mode 2
mode 3
N, =
t ma 1 1
AVma
N
Ap™
1 max 1 3
Ap™
^ = 0.0224 ; 540 deg
^ = 0.0341 ; 420 deg
The analysis of charts show that elasticity properties of the fragment under torsion firstly increases and during modes 2-5 are stabilized and become almost identical, which makes it possible to determine it's averaged rigidity under the pressure P1 = 0.2 MPa:
N„
0.0341 + 0.0346 + 2 ■ 0.0365 4 "
0.0354
M
= 2.8
6 .6 480
: 0.0346
M ;
deg'
deg rad
Experimental results at P2 = 0.4 MPa are shown in table 2.
Table 2
Angle of twist deg Pressure in a hose, P2 = 0.4 MPa
Torque mk, Nm
Mode 1 Mode 2 Mode 3 Modes 4-5
0 0.00 - - -
60 3.50 - - -
120 4.82 0.00 - -
180 6.49 4.25 0.00 0.00
240 8.28 6.62 4.77 5.33
300 10.0 8.19 6.37 6.89
360 13.2 10.7 7.99 8.93
420 15.3 13.3 11.7 11.5
480 18.2 17.6 16.0 15.1
540 - 20.1 19.5 18.8
The basic (1) mode of loading was conducted on an undeformed fragment of the fire hose. The maximum
A^ = 480°
value of deformation was
under the load
MImax=18.2Nm After unloading the residual deformation of the
, . Apr,es = 120°.
fragment was ^1
During the repeated loading (2), which was held in two minutes after the first, the maximum value of deformation
ApT = 420°
M2max=20.1Nm After
was under the load
unloading the residual deformation of the fragment was Aç>2res=60°
During the third loading (3), which was held in two minutes after the second, the maximum value of deformation
.max = 36Q°
was under the load M3max=19.5Nm After
unloading the residual deformation of the fragment was almost
Avrem = 0°
absent, i.e. 3
The numerical parameters of the following loading modes (4-5), that were conducted with the same two-minute intervals do not differ from one another allowing to average their values.
Ammac = 360°
The maximum value of deformation was 4 5 under the load M4-5max=18.8Nm After unloading the residual
Amrem = 0°
deformation of the fragment was absent, i.e. 4 5
Diagrams corresponding to the experimental results under the internal pressure in a hose P2 = 0.4 MPa are shown in Figure 3.
GO ISO 240 300 3G0 420 430 340 300
TWistiilg comer, deg
Figure 3 - Diagram of loads of the test fragment of fire hose under torsion (pressure in a hose P2 = 0.4 MPa)
If we take a relationship between load and deformation of the fire hose fragment under torsion to be linear in first approximation, it's average rigidity can be defined:
I
- mode 1
- mode 2
- mode 3
- modes 4-5
I ma
Açm
T max 1 3
Atf
I
AvT'x
= = 0.0379 ; 480 deg
0 .1 №
=-= 0.0479-;
420 deg
9 .5 M
--= 0.0542-;
360 deg
= = 0.0522 . 360 deg
The analysis of charts show that elasticity properties of the fragment under torsion firstly increases and during modes 2-5 are stabilized and become almost identical, which makes it possible to determine it's averaged rigidity under the pressure
P2 = 0.4 MPa:
0.0479 + 0.0542 + 2 • 0.0522 „„^ , M „„ M
NÊB2 =-= 0.0516-= 2.S -.
4 deg rad
Experimental results at P3 = 0.6 MPa are shown in table 3.
Table 3
Angle of twist 9, deg Pressure in a hose, P3 = 0.6 MPa
Torque mk, Nm
Mode 1 Mode 2 Mode 3 Modes 4-5
0 0.00 - - -
60 4.01 - - -
120 5.43 0.00 0.00 0.00
180 7.00 5.84 5.65 5.80
240 8.82 6.92 7.31 7.59
300 10.5 9.59 9.10 9.06
360 12.8 12.2 11.5 11.9
420 14.9 14.7 13.9 14.1
480 18.8 18.2 17.9 17.9
540 - 20.3 21.6 22.1
The basic (1) mode of loading was conducted on an undeformed fragment of the fire hose. The maximum
value of deformation was Aç^* = 480° under the load M1max=18.8Nm After unloading the residual deformation of the
fragment was Açr;s = 120°.
During the repeated loading (2), which was held in two minutes after the first, the maximum value of deformation
was Aç2mœc = 420° under the load M2max=20.3Nm After unloading the residual deformation of the fragment was almost
absent, i.e. Aty™* = 0.
During the third loading (3), which was held in two minutes after the second, the maximum value of deformation
was ApT* = 420° under the load M3max=21.6Nm After unloading the residual deformation of the fragment was
Apr;s = o.
The numerical parameters of the following loading modes (4-5), that were conducted with the same two-minute intervals do not differ from one another allowing to average their values.
The maximum value of deformation was Ap™ = 420° under the load M45max=22.1Nm After unloading the residual
deformation of the fragment was Ap™m5 = 0.
Diagrams corresponding to the experimental results under the internal pressure in a hose P3 = 0.6 MPa are shown in Figure 4.
-1 Müdes 4-1
|P3-0,6IV iPal'
s\
-1 Viodc 1| -A.
— 1 Mode 3|-
r/ s
/ \
/ i i
a sa 120 ISO 240 300 3G0 420 4BD 540 GOO
Twisting comer, deg
Figure 4 - Diagram of loads of the test fragment of fire hose under torsion (pressure in a hose P3 = 0.6 MPa)
If we take a relationship between load and deformation of the fire hose fragment under torsion to be linear in first approximation, it's average rigidity can be defined:
L8 = 0.0392 ;
480 deg
M
N, _
t max 1 1
- mode 1
Aç
N2 =
- mode 2
- mode 3
j max I*
= — = 0.0483-— ;
Açmax 420 deg '
I r 2 .6
N _ —3— _-= 0.0514-
Açmax 420 deg '
N,
t max
1 4-5
- modes 4-5
^ = 0.0526 ; 420 deg'
The analysis of charts show that elasticity properties of the fragment under torsion firstly increases and during modes 2-5 are stabilized and become almost identical, which makes it possible to determine it's averaged rigidity under the pressure P3 = 0.6 MPa:
0.0483 + 0.0514 + 2• 0.0526 M „ „ M
N b 3 =-= 0.0512-= 2.9 -.
4 deg rad
For further research it is useful to define the elasticity modulus ( ) of the fire hose under torsion:
kh = N L,
where IP - the polar moment of inertia of the hose defined in first approximation:
_n((d + 2ä)4 - d4 ) _n((i + 2-1.5)4 - 514 ) =
= 171 3m 4 _ 0.171 -6 m4
The elasticity modulus of the hose under torsion corresponding to the internal pressure is:
- P1 = 0.2 MPa:
K _NiBIL _ 2.9 ^ ,°;985 ^ _1 .76B _1 .7MPa;
IP 0.171 d P2
0.4
kf _N iB2 L _ 2.S —0 985 , =1 . 1 6B =1 . 1 MPa;
P3
0.6
MPa:
MPa:
kf _NiB3L _ 2.9 —0 985 , _® .96B _® .9MPa.
Conclusions. Definition of elasticity properties of fire hoses of type "T" with internal diameter of 51 mm under static torsion load is carried out for upcoming theoretical and experimental studies of the residual life of fire hoses.
The results of investigation show an increase in fire hose
rigidity under torsion after a few (1-2) cycles of «loading -unloading», after which the elasticity properties are stabilized.
With the increase of an internal pressure in a hose it's elasticity modulus under torsion initially increases and then stabilizes at i41 K1 MPa.
A significant change of elasticity properties of the fire hose within the initial cycles of «loading - unloading» and their stabilization during further tests significantly reduced which together with a decrease of residual deformations brings the behavior of a hose material under torsion close to elastic one.
Change of material properties of the fire hose during successive deformational cycles of «loading - unloading» is reversed, intervals between deformational cycles result in a partial recovery of mechanical properties, bringing them to their original values.
LITERATURE
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