FLOW CALCULATIONS & RESONANCE FREQUENCY CHECK
Flow to DP
DP to Flow
LIQUIDS (Volumetric)
LIQUIDS (Volumetric)

GASSES (Volumetric)

GASSES (Volumetric)

or

LIQUIDS / GASSES / STEAM (Mass)
LIQUIDS / GASSES / STEAM (Mass)
Symbols & Units
Symbols & Units
DP Differential Pressure (mBar)
S Specific Gravity (Air = 1)
D Density at Actual Conditions
(KG/M3)
  Base Density of Water at 40C
999.972 KG/M3
  Density of Water at 15.550C
999.074 KG/M3
  Density of Air at 00C 1.292 KG/M3
A Pipe Internal x-section Area (cm2)
Tf Actual Temperature (0C)
Pf Actual Pressure (Bar A) (Absolute)
K TORBAR Co-Efficient
(see Table Below)
Normal Conditions 00C, 1 Atmosphere
(1.013 Bar)
QA = Flow (M3/HR)
QB = Flow (NM3/HR) at 00C,
1 ATMOS (1.013 bar)
QC = Flow (KG/HR)
S = Specific Gravity (Air = 1)
D = Density at actual conditions
(KG/M3)
  Base Density of water at 40C
= 999.972 KG/M3
  Density of water at 15.550C
= 999.074 KG/M3
  Base Density of Air at 00C
  1 ATMOS (1.013 bar) = 1.292 KG/M3
A = Pipe internal X-Section Area (CM2)
Tf = Actual Temperature (0C)
Pf = Actual Pressure (bar Absolute)
K = Torbar Co-efficient
(see Table Below)
  Copies of the derivations of these
formulae are available on request
TORBAR CO-EFFICIENT K
PIPE SIZE
MODEL NUMBER
(Internal diameter)
(mm)		 301 601
311 		401 402
411 412
701 702
711 712		 511 512
811 812
50 0.6483    
75 0.7027
 
100 0.7497 0.6174  
150 0.7671 0.6505  
200
0.6647  
250
0.6794 0.6876
300
0.6941 0.7024
350
0.7160 0.7303
400
0.7380 0.7564
450
0.7402 0.7699
600
0.7468 0.7815
900
0.7473 0.7847
1200
0.7475 0.7849
1500
0.7476 0.7850
1800 and above 0.7476 0.7850
FOR SIZES NOT SHOWN ABOVE, DETERMINE K BY EXTRAPOLATION
For Models 121, 122, 123 (all sizes) K = 1

It is important that the answers from these equations are verified with the factory or Torbar accredited supplier before use with your system

 

 

Resonance Frequency Check
This check is not necessary for LIQUID FLOWS. because the maximum allowable DP is reached before resonance occurs (see table opposite) or Models 121, 122, and 123
For Gas and Vapour flows a Resonance Frequency Check MUST be made. Equations have been derived for the various TORBAR models to determine LOWand HIGH critical velocities (VL and VH) which define the narrow resonance band of velocities which should be outside the continuous operating flow range of the TORBAR.
The table below lists those equations to calculate the VL and VH. If the calculation shows VL to VH to be within the continuous operating flow range, then an alternative, suitable model of TORBAR should be selected to give acceptable values of VL and VH.
Always check that the maximum flow DP is less than the 'Maximum Allowable DP' as shown in the opposite table.
TORBAR
MODEL		 CRITICAL
VL (M/SEC) 		VELOCITIES
VH (M/SEC)		 L (METRES) (see below)
301 0.472 / L2 0.728 / L2 ID + WALL + 0.05
311 0.472 / L2 0.728 / L2 ID + WALL + SO
L601 0.472 / L2 0.728 / L2 ID + WALL + 0.02
401 1.843 / L2 2.840 / L2 ID + WALL + 0.08
402 8.08 / L2 12.44 / L2 ID + 2 x WALL + 0.115
411 1.843 / L2 2.840 / L2 ID + WALL + SO
412 8.08 / L2 12.44 / L2 ID + 2 x WALL + SO + 0.05
L701 1.843 / L2 2.840 / L2 ID + WALL + 0.05
L702 8.08 / L2 12.44 / L2 ID + 2 x WALL + 0.10
H701 1.843 / L2 2.840 / L2 ID + WALL + 0.05
H702 8.08 / L2 12.44 / L2 ID + 2 x WALL + 0.10
H711 1.843 / L2 2.840 / L2 ID + WALL + SO + VV + 0.05
H712 8.08 / L2 12.44 / L2 ID + 2 x WALL + SO + VV + 0.10
511 10.88 / L2 16.766 / L2 ID + WALL + SO
512 47.65 / L2 73.43 / L2 ID + 2 x WALL + SO + 0.08
H811 10.88 / L2 16.766 / L2 ID + WALL + SO + VV + 0.05
H812 47.65 / L2 73.43 / L2 ID + 2 x WALL + SO + VV + 0.13
L = UNSUPPORTED LENGTH (METRES)
ID = PIPE INTERNAL DIAMETER (METRES)
WALL = PIPE WALL THICKNESS (METRES)
SO = OVERALL LENGTH OF FLANGED PIPE FITTING (METRES)
VV = OVERALL LENGTH OF ISOLATION VALVE (METRES)

The above equations are derived from TORBAR resonance frequency data and calculations. Full details are available on request.
Maximum Allowable DP
Depending on the model and size of TORBAR there is a maximum figure of Differential Pressure above which the TORBAR should NOT be used due to the imposition of excessive mechanical stresses. Check the table below to ensure that the application is suitable. If the calculated DP exceeds the maximum shown below, then select an other appropriate model to suit the application.

For liquid flow applications where there are continual or frequent process pulsations, then the end-support models should always be selected for pipe sizes over 150mm diameter.
  TORBAR BASE MODEL NUMBER
PIPE SIZE
(Internal Dia.)		 301 311
601		 401 411
701 711		 402 412
701 712		 511
811		 512
812
ins (mm) Maximum allowable DP in mbar
2 (50) 6250



3 (75) 2790



4 (100) 1565 5100


6 (150) 695 2285


8 (200)
1285


10 (250)
820 3250 3400
12 (300)
570 2250 2350
14 (350)
415 1680 1725
16 (400)
320 1285 1335
18 (450)
250 1015 1055 4225
24 (600)
140 570 590 2375
36 (900)
50 250 265 1055
48 (1200)
30 140 145 590
60 (1500)
20 90 90 380
72 (1800)
10 60 65 265
Above 1800 mm - consult factory
FOR SIZES NOT SHOWN ABOVE DETERMINE MAXIMUM ALLOWABLE DP BY EXTRAPOLATION
For models 121, 122, 123 (all sizes) Maximum DP value is 2500 mbar.
The above figures are theoretically derived and include a x10 safety factor over and above basic standards and specification. Full theoretical data with computer programme is available on request.