The following pages of data and physical properties are provided as references in the use and
application of Spiral pipe and fittings.
The complexity of air system design engineering
has changed dramatically since the 1950’s even
though the basic formulas have still remained
the same. There have been significant additional
theories added with new extremely complex
and systematic formulas needed to satisfy these
computations and provide for further enhancement
of the overall systems of today. We have tried to
give you the basic information needed for both
methods. The old rule of thumb method seems to
be the simplest method for smaller and moderate
jobs. For complex jobs, we still recommend a
certified engineer.
The new method of static loss calculations is far too
complex for the average Joe. Therefore, we have
given you the quick reference chart approach to
simplify and speed up the process.
Basic Definitions
The following are used to describe airflow and will
be used extensively in this catalog. Standard air
is defined at standard atmospheric pressure (14.7
psia), room temperature (700 F) and zero water
content; its value is normally taken to be 0.075 lbs/
ft3.
The volumetric flow rate, many times referred to as
“volumes,” is defined as the volume or quantity of
air that passes a given location per unit of time, i.e.
(cfm). It is related to the average velocity and the
flow cross-section area in ft2 by the equation
Q=VA
where Q = volumetric flow rate or cfm,
V= average velocity or fpm, and
A= cross-sectional area in ft2.
Given any two of these three quantities, the third
can readily be determined as follows:
Q=VA or V=Q/A or A=Q/V
There are three different but mathematically related
pressures associated with a moving air stream.
Static pressure (SP) is defined as the pressure in
the duct that tends to burst or collapse the duct
and is expressed in inches of water gage (˝wg).
Engineering Data
Velocity pressure (VP) is defined as that pressure
required to accelerate air from zero velocity to
some velocity (V) and is proportional to the kinetic
energy of the air stream. Using standard air, the
relationship between V and VP is given by
Ó
VP will only be exerted in the direction of airflow
and is always positive.
Total pressure (TP) is defined as the algebraic sum
of the static and velocity pressures or TP=SP+VP.
Total pressure can be positive or negative with
respect to atmospheric pressure and is a measure
of energy content of the air stream, always
dropping as the flow proceeds downstream through
a duct. The only place it will rise is across the fan.
Total pressure can be measured with a pitot tube
pointing directly upstream and connected to a
manometer.
Principles of air flow
Two basic principles of fluid mechanics govern
the flow of air in industrial ventilation systems:
conservation of mass and conservation of energy.
These are essentially bookkeeping laws which state
that all mass and all energy must be completely
accounted for and it is important to know what
simplifying assumptions are included in the
principles discussed below:
1. Heat transfer effects are neglected. However,
if the temperature inside the duct is significantly
different than the air temperature surrounding
the duct, heat transfer will occur. This will lead to
changes in the duct air temperature and hence in
the volumetric flow rate.
2. Compressiblity effects are neglected. However,
if the overall pressure drop from the start of the
system to the fan is greater than about 20 ˝wg, then
the density needs to be accounted for.
3. The air is assumed to be dry. Water vapor in the
air stream will lower the air density, and correction
for this effect, if present, should be made.
4. The weight and volume of the contaminant in
the air stream is ignored. This is permissible for
the contaminant concentrations in typical exhaust
ventilation systems. For high concentrations of
solids or significant amounts of some gases other
than air, corrections for this effect should be
included. (Continued on page 54)
50
www.spiralmfg.com
Engineering Data
Static Pressure (SP) Loss for 90° and 45°
Die-Formed Elbows
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Table 51-1: Duct Pressure Loss Results for Stamped (1.5CLR) Elbows @ 4000 ft/min with .999 (VP)
Size
3”
4”
5”
6”
7”
8”
9”
10”
12”
14”
Straight Duct Loss (inches Water):
10.15
7.04
5.31
4.22
3.49
2.95
2.55
2.24
1.79
1.48
Total Duct Loss (˝wg) 900 Stamped
10.30
7.18
5.46
4.37
3.63
3.01
2.70
2.39
1.94
1.63
0.15
Total Duct Loss (˝wg) 45 Stamped
10.22
7.11
5.38
4.30
3.56
3.14
2.62
2.32
1.86
1.56
0.075
Flow Rate: SCFM
192.5
342.3
534.8
770.2
1068
1396
1732.5
2140
3080
4194
0
Elbow
Loss Factor
Based per 100 feet duct length • viscosity (cP).018 • Inlet pressure (psig) 0 • Temp (F) 70° • Galvanized metal roughness (ft) .0005 • Flow region Turbulent, 4000fpm •
friction factor 0.02 • velocity pressure .999
51
11419 Yellowpine Street N.W. • Minneapolis, MN 55448-3158
Phone: 763-755-7677 • 800-426-3643 • Fax: 763-755-6184
Engineering Data
Static Pressure (SP) Loss for 90° and 45°,
5-Gore and 3-Gore Elbows
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Table 52-1: Duct Pressure Loss Results for Gored (1.5CLR) Elbows @ 4000 ft/min with .999 (VP)
3”
4”
5”
6”
7”
8”
9”
10”
12”
14”
Straight Duct Loss (inches Water):
Size
10.15
7.04
5.31
4.22
3.49
2.95
2.55
2.24
1.79
1.48
Total Duct Loss (“wg) 900 5 Gore
10.39
7.25
5.55
4.46
3.72
3.19
2.79
2.48
2.03
1.72
0.24
Total Duct Loss (“wg) 450 3 Gore
10.32
7.21
5.48
4.39
3.65
3.21
2.72
2.41
1.96
1.65
0.17
Flow Rate: SCFM
192.5
342.3
534.8
770.2
1068
1396
1732
2140
3080
4194
Elbow
Loss Factor
Based per 100 feet duct length • viscosity (cP).018 • Inlet pressure (psig) 0 • Temp (F) 70° • Galvanized metal roughness (ft) .0005 • Flow region Turbulent, 4000fpm •
friction factor 0.02 • velocity pressure .999
52
www.spiralmfg.com
Engineering Data
53
Static Pressure (SP) Loss in
90° Tees & Conical Tees
11419 Yellowpine Street N.W. • Minneapolis, MN 55448-3158
Phone: 763-755-7677 • 800-426-3643 • Fax: 763-755-6184
Engineering Data
Static Pressure (SP) Loss in 45° Laterals
& Branch Entry Loss
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61
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Branch Entries
Outlet
Branch 1
Branch Angle
Branch 2
(Continued from page 50)
Conservation of mass requires that the net
change of mass flow rate must be zero. If the
effects discussed on page 51 are negligible, then
the density will be constant and the net change
of volumetric flow rate (Q) must be zero. Therefore, the flow rate that enters a hood must be the
same as the flow rate that passes through the
duct leading from the hood. At a branch entry,
the sum of the two flow rates that enter the fitting
must be equivalent to the total leaving the fitting.
Note that branch entry loss is assumed to
occur in the branch for calculations. Enlargement regain should not be included in branch
entry enlargements. Any losses due to acceleration of combined flow should be added
to the calculations in the outlet pipe.
Table 54-1: Equivalent Resistance in
Feet of Straight Duct
Size
300
450
Size
300
450
3”
3
4
20”
18
28
4”
4
6
22”
20
31
5”
5
7
24”
22
34
6”
6
9
26”
24
37
7”
6
10
28”
26
40
8”
7
11
30”
28
43
9”
8
13
32”
29
45
10”
9
14
34”
31
48
12”
11
17
36”
33
51
14”
13
20
38”
35
54
16”
15
23
40”
37
57
18”
17
26
42”
39
60
54
www.spiralmfg.com
Engineering Data
Equivalent Resistance & Friction Loss
Quick Reference Charts
Table 55-1: Elbow Equivalent Resistance In Feet Of Straight Pipe By Center Line Radius (CLR)
1.5 CLR
0
0
2.0 CLR
0
0
0
0
2.5 CLR
0
0
0
Size
90
Elbow
60
Elbow
45
Elbow
30
Elbow
90
Elbow
60
Elbow
45
Elbow
30
Elbow
90
Elbow
600
Elbow
450
Elbow
300
Elbow
3”
5
3
3
2
3
2
2
1
3
2
2
1
4”
6
4
3
2
4
3
2
1
4
3
2
1
5”
9
6
5
3
6
4
3
2
5
3
3
2
6”
12
8
6
4
7
5
4
2
6
4
3
2
8”
13
9
7
4
9
6
5
3
7
5
4
2
10”
15
10
8
5
10
7
5
3
8
5
4
3
12”
20
13
10
7
14
9
7
5
11
7
14”
25
17
13
8
17
11
9
6
16”
30
20
15
10
21
14
11
7
18”
36
24
18
12
24
16
12
8
20”
41
28
21
14
28
19
14
9
22”
46
31
23
15
32
21
16
11
24”
57
38
29
19
40
27
20
13
30”
74
50
37
24
51
34
26
17
36”
93
62
47
31
64
43
32
21
40”
105
70
53
35
72
48
36
24
48”
130
87
65
43
89
60
45
29
6
4
7
5
1
3
2
1
4
35
73
49
Losses in Elbows and Fittings. When an air stream undergoes change of either direction or velocity, a dynamic loss occurs.
Unlike friction losses in straight duct, fitting losses are due to internal turbulance rather than skin friction. Hence roughness of material has but slight effect over a wide range of moderately smooth materials. Fitting losses can be expressed as
equivalent length of straight duct; or as a fraction of velocity pressure; or directly in inches of water gage (˝wg).
Table 55-2: Friction Loss In Inches Of Water (˝WG) Per 100 Feet Of Spiral Pipe
Velocity FPM
Duct
Velocity FPM
Velocity FPM
Dia.
3500
4000
4500
5000
Duct
Dia.
3500
4000
4500
5000
Duct
Dia.
3500
4000
4500
5000
3”
7.75
9.99
12.50
15.27
17”
0.93
1.20
1.51
1.84
44”
0.29
0.38
0.47
0.58
4”
5.46
7.03
8.80
10.75
18”
0.87
1.12
1.40
1.72
46”
0.28
0.36
0.45
0.55
5”
4.16
5.36
6.70
8.19
20”
0.77
0.99
1.23
1.51
48”
0.26
0.34
0.42
0.52
6”
3.33
4.29
5.36
6.55
22”
0.68
0.88
1.01
1.34
50”
0.25
0.32
0.40
0.49
7”
2.76
3.55
4.44
5.43
24”
0.61
0.79
0.99
1.21
52”
0.24
0.31
0.38
0.47
8”
2.34
3.02
3.78
4.61
26”
0.56
0.72
0.90
1.01
54”
0.23
0.29
0.37
0.45
9”
2.03
2.62
3.27
4.00
28”
0.51
0.65
0.82
1.00
56”
0.22
0.28
0.35
0.43
10”
1.78
2.30
2.88
3.51
30”
0.47
0.60
0.75
0.92
58”
0.21
0.27
0.34
0.41
11”
1.59
2.05
2.56
3.13
32”
0.43
0.56
0.70
0.85
60”
0.20
0.26
0.32
0.39
12”
1.43
1.84
2.30
2.81
34”
0.40
0.52
0.65
0.79
13”
1.30
1.67
2.09
2.55
36”
0.37
0.48
0.60
0.74
14”
1.18
1.53
1.91
2.33
38”
0.35
0.45
0.56
0.69
15”
1.09
1.40
1.75
2.14
40”
0.33
0.42
0.53
0.65
16”
1.01
1.30
1.62
1.98
42”
0.31
0.40
0.50
0.61
Ó°Ç{
This equation gives the friction losses, expressed as “wg per 100 feet of pipe, for standard air of 0.075 lbm/ft3 density flowing
through average, clean, round galvanized pipe having approximately 40 slip joints per 100 feet (k = 0.0005 ft.).
55
11419 Yellowpine Street N.W. • Minneapolis, MN 55448-3158
Phone: 763-755-7677 • 800-426-3643 • Fax: 763-755-6184
Engineering Data
Static Pressure (SP) Loss for Spiral Pipe
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56
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Compression & Deflection Properties
of Spiral Pipe, Static Pressure (SP) Loss in
Flexible Rubber Hose
Engineering Data
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11419 Yellowpine Street N.W. • Minneapolis, MN 55448-3158
Phone: 763-755-7677 • 800-426-3643 • Fax: 763-755-6184
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Engineering Data
Diameter, Gauge & StrengthProperties;
Collapsing & Bursting Pressures
Diameters, Gauge, and Strength
Properties of Spiral Pipe
Nominal
Diameter
(inches)
Bursting Pressure
(Seam Failure)
P.S.I
Steel Guage
Std.
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
22
22
22
22
22
22
22
22
22
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
20
22
24
26
28
30
32
34
36
42
48
Max.
22
20
18
18
18
18
18
18
18
18
18
18
18
18
18
18
18
18
18
18
18
18
18
18
18
18
18
Std.
*
500
350
275
220
175
150
135
115
95
85
80
72
65
58
53
47
41
48
42
37
33
30
28
27
29
25
Max.
*
*
*
*
*
460
375
325
275
240
220
185
170
160
145
140
120
100
87
78
68
60
55
52
48
37
32
Calculation of wall thickness to diameter ratio:
Internal Negative
Pressure To Collapse
Standard Pipe
In. ˝wg
**
**
**
**
**
**
304
193
111
83
66
47
44
39
36
35
33
33
33
***
***
***
***
***
***
***
***
PSI
**
**
**
**
**
**
11.0
7.0
4.0
3.0
2.4
1.7
1.6
1.4
1.3
1.25
1.2
1.2
1.2
***
***
***
***
***
***
***
***
­ / ®
Example: For 24 gauge steel and duct diameter of 13”.
­ / ® = .0296/13 = .0023
Above reference, for lower charts, to predict
bursting and collapsing pressures.
Gauge
Mean Thickness
16
.0635
18
.0516
20
.0396
22
.0336
24
.0276
26
.0217
1 PSI = 27.7 ˝wg
1 ˝wg = .0361 PSI
Properties are approximate, based on both
empirical and extrapolated data
*Did not fail at 500 PSI ** Did not fail at -14.7 PSI (-407 in. H2O)
*** Less than 1.2 PSI
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58
59
176.715
201.062
226.981
254.470
314.160
380.134
452.390
530.930
615.754
706.860
804.250
907.922
1017.878
1134.118
1256.640
1385.446
1520.534 10.5593
1661.906 11.5410
1809.562 12.5664
1963.500 13.6354
2123.722 14.7481
2290.226 15.9044
2463.014 17.1043
2642.086 18.3478
2827.440 19.6350
15”
16”
17”
18”
20”
22”
24”
26”
28”
30”
32”
34”
36”
38”
40”
42”
44”
46”
48”
50”
52”
54”
56”
58”
60”
11419 Yellowpine Street N.W. • Minneapolis, MN 55448-3158
Phone: 763-755-7677 • 800-426-3643 • Fax: 763-755-6184
5891
5504
5131
4771
4424
4091
3770
3462
3168
2886
2618
2363
2121
1892
1676
1473
1283
1106
942
792
655
530
473
419
368
321
236
164
133
105
80
59
41
26
15
300
6872
6422
5986
5567
5162
4772
4398
4039
3696
3367
3054
2757
2474
2207
1955
1718
1497
1290
1100
924
764
619
552
489
430
374
275
191
155
122
94
69
48
31
17
350
7854
7339
6842
6362
5899
5454
5027
4616
4224
3848
3491
3150
2827
2522
2234
1964
1710
1475
1257
1056
873
707
631
559
491
428
314
218
177
140
107
79
55
35
20
400
8836
8257
7697
7157
6637
6136
5655
5193
4752
4330
3927
3544
3181
2837
2513
2209
1924
1659
1414
1188
982
795
709
628
552
481
353
245
199
157
120
88
61
39
22
450
EXHAUST GRILLES
9818
9174
8552
7952
7374
6818
6283
5771
5280
4811
4363
3938
3534
3153
2793
2454
2138
1844
1571
1320
1091
884
788
698
614
535
393
273
221
175
134
98
68
44
25
500
10799
10091
9407
8747
8111
7499
6912
6348
5808
5292
4800
4332
3888
3468
3072
2700
2352
2028
1728
1452
1200
972
867
768
675
588
432
300
243
192
147
108
75
48
27
550
650
700
750
800
900
1000
HORIZONTAL SUPPLY DUCTS
1200
11781
11009
10263
9543
8849
8181
7540
6925
6336
5773
5236
4725
4241
3783
3351
2945
2566
2212
1885
1584
1309
1060
946
838
736
641
471
327
265
209
160
118
82
52
29
12763
11926
11118
10338
9586
8863
8168
7502
6864
6254
5672
5119
4595
4098
3630
3191
2779
2397
2042
1716
1418
1149
1025
908
798
695
511
355
287
227
174
128
89
57
32
13745
12843
11973
11133
10324
9545
8796
8079
7391
6735
6109
5513
4948
4414
3910
3436
2993
2581
2199
1848
1527
1237
1103
977
859
748
550
382
309
244
187
137
95
61
34
14726
13761
12828
11928
11061
10227
9425
8656
7919
7216
6545
5907
5301
4729
4189
3682
3207
2765
2356
1980
1636
1325
1182
1047
920
802
589
409
331
262
200
147
102
65
37
15708
14678
13683
12723
11798
10908
10053
9233
8447
7697
6981
6301
5655
5044
4468
3927
3421
2950
2513
2112
1745
1414
1261
1117
982
855
628
436
353
279
214
157
109
70
39
17672
16513
15394
14314
13273
12272
11310
10387
9503
8659
7854
7088
6362
5675
5027
4418
3848
3318
2827
2376
1964
1590
1419
1257
1104
962
707
491
398
314
241
177
123
79
44
19635
18348
17104
15904
14748
13635
12566
11541
10559
9621
8727
7876
7069
6305
5585
4909
4276
3687
3142
2640
2182
1767
1576
1396
1227
1069
785
545
442
349
267
196
136
87
49
59
23562
22017
20525
19085
17698
16363
15080
13849
12671
11545
10472
9451
8482
7566
6702
5891
5131
4424
3770
3168
2618
2121
1892
1676
1473
1283
942
655
530
419
321
236
164
105
27489
25687
23946
22266
20647
19090
17593
16157
14783
13470
12217
11026
9896
8827
7819
6872
5986
5162
4398
3696
3054
2474
2207
1955
1718
1497
1100
764
619
489
374
275
191
122
69
1400
29453
27522
25656
23857
22122
20453
18850
17312
15839
14432
13090
11814
10603
9458
8378
7363
6414
5531
4712
3960
3273
2651
2364
2094
1841
1604
1178
818
663
524
401
295
205
131
74
1500
EXHAUST MAINS
QUANTITY OF AIR FLOWING, IN CFM
600
SUPPLY FLUES AND RISERS
EHAUST RISERS AND VENT STACKS
35343
33026
30788
28628
26547
24544
22620
20774
19007
17318
15708
14176
12723
11349
10053
8836
7697
6637
5655
4752
3927
3181
2837
2513
2209
1924
1414
982
795
628
481
353
245
157
88
1800
39270
36696
34209
31809
29496
27271
25133
23082
21119
19242
17453
15752
14137
12610
11170
9818
8552
7374
6283
5280
4363
3534
3153
2793
2454
2138
1571
1091
884
698
535
393
273
175
98
2000
43197
40365
37629
34990
32446
29998
27646
25390
23230
21167
19199
17327
15551
13871
12287
10799
9407
8111
6912
5808
4800
3888
3468
3072
2700
2352
1728
1200
972
768
588
432
300
192
108
2200
47124
44035
41050
38170
35395
32725
30159
27698
25342
23091
20944
18902
16965
15132
13404
11781
10263
8849
7540
6336
5236
4241
3783
3351
2945
2566
1885
1309
1060
838
641
471
327
209
118
2400
GASES AND FUMES
Reproduced in part by permission from Handbook of Air Conditioning Heating and Ventilating, The Industrial Press, New York.
9.6212
8.7267
7.8758
7.0686
6.3050
5.5851
4.9088
4.2761
3.6870
3.1416
2.6398
2.1817
1.7672
1.5763
1.3963
1.2272
1.0690
0.7854
0.5454
0.4418
153.938
63.617
9”
0.3491
14”
50.266
8”
0.2673
78.540
38.485
7”
0.1964
113.098
28.274
6”
0.1364
12”
19.635
5”
0.0873
0.0491
10”
7.069
12.566
4”
Sq. Ft.
AREA
Sq. In.
3”
Dia.
In.
Velocity FPM
Q = CFM
V = VELOCITY
A = AREA IN FT2
Q = VA
Capacity of Round Pipe 3 to 60 Inches Diameter, 300 to 2400 FPM
www.spiralmfg.com