FILTER SIZING Corrective factor
The correct filter sizing have to be based on the variable pressure drop
depending by the application. For example, for the return filter the
pressure drop have to be in the range 0.4 - 0.6 bar.
The pressure drop calculation is performed by adding together the
value of the housing with the value of the filter element. The pressure
drop in the housing is proportional to the fluid density (kg/dm
3
); all
the graphs in the catalogue are referred to mineral oil with density of
0.86 kg/dm
3
.
The filter element pressure drop is proportional to its viscosity (mm
2
/s),
the corrective factor Y is related to an oil viscosity different than 30
mm
2
/s.
∆pc = Filter housing pressure drop [bar]
∆pe = Filter element pressure drop [bar]
Y = Multiplication factor Y (see correspondent table),
depending on the filter element size, on the filter element
lenght and on the filter media
Q = flow rate (l/min)
V1 reference viscosity = 30 mm
2
/s (cSt)
V2 = operating viscosity in mm
2
/s (cSt)
∆pe = Y : 1000 x Q x (V2/V1)
∆p Tot. = ∆pc + ∆pe
Application data:
Top tank return filter
Filter with in-line connections
Pressure Pmax = 10 bar
Flow rate Q = 120 l/min
Viscosity V2 = 46 mm
2
/s (cSt)
Oil viscosity = 0.86 kg/dm
3
Required filtration efficiency = 25 μm with absolute filtration
With bypass valve and 1 1/4” inlet connection
From the working pressure and the flow rate we understand it should be
possible using the following top tank return filter series: MPT, MPH and FRI.
Let’s proceed with MPT series.
The size 20 doesn’t achieve the required flow rate, therefore we
have to consider the size 100. The final version of size 100 (101, 104,
110, 120 and 114) will be then defined in function of the mounting
characteristics.
Sizing data for single cartridge, head at top
Calculation examples with HLP Mineral oil Variation in viscosity
*
0.40
0.30
0.20
0.10
0
MPT 110 - Length 3 - 4
Δp bar
0
60 120 180 240 300
Flow rate l/min
G 1 1/4”
Filter housings ∆p pressure drop.
The curves are plotted using mineral oil with density of 0.86 kg/dm
3
in compliance with ISO 3968. ∆p varies proportionally with density.
Reference viscosity 30 mm
2
/s
Corrective factor Y, to be used for the filter element pressure drop calculation.
The values depend to the filter size and lenght and to the filter media.
1
2
3
MF 400
MFX 400
1
2
3
4
MF 100
MFX 100
1
2
3
4
MR 250
1
2
3
4
MR 850
1
2
3
4
5
MR 100
1
2
3
4
5
MR 630
1
2
MF 180
MFX 180
Filter
element
Type
Absolute filtration Nominal filtration
A03 A16A06 A25A10 P10 P25 M25
M60 M90
H Series N Series
1
MF 030
MFX 030
2
MF 190
MFX 190
1
MF 750
MFX 750
CU 025
CU 040
CU 100
CU 250
CU 630
3.20
2.00
1.90
28.20
17.33
10.25
6.10
5.35
4.00
2.60
1.84
0.60
0.37
0.27
0.23
19.00
11.70
7.80
5.50
4.20
3.10
2.06
1.48
1.30
0.74
3.67
1.69
74.00
1.69
1.08
78.00
25.88
15.20
3.25
1.96
1.06
2.75
1.87
1.60
24.40
12.50
9.00
5.40
4.85
3.28
2.20
1.56
0.43
0.26
0.18
0.16
17.00
10.80
6.87
4.97
3.84
2.48
1.92
1.30
1.20
0.65
3.05
1.37
50.08
1.37
0.84
48.00
20.88
14.53
2.55
1.68
0.84
1.39
0.88
0.63
8.67
6.86
3.65
2.30
2.32
1.44
1.08
0.68
0.34
0.23
0.17
0.13
6.90
4.40
3.70
2.60
2.36
1.32
0.82
0.60
0.48
0.30
1.64
0.68
20.00
0.60
0.49
28.00
10.44
5.14
1.55
0.85
0.42
1.33
0.85
0.51
8.17
5.70
3.33
2.20
1.92
1.10
1.00
0.56
0.25
0.21
0.17
0.12
6.30
4.30
3.10
2.40
2.15
1.14
0.76
0.56
0.40
0.28
1.56
0.54
16.00
0.49
0.36
24.00
10.00
4.95
1.35
0.72
0.33
1.06
0.55
0.49
1.50
1.07
0.86
0.44
0.13
0.11
0.05
0.04
4.60
3.00
2.70
2.18
1.90
0.92
0.38
0.26
0.25
0.13
1.24
0.51
9.00
0.44
0.26
9.33
3.78
2.00
0.71
0.42
0.17
0.96
0.49
0.39
4.62
3.05
1.63
1.19
1.38
0.96
0.77
0.37
0.12
0.08
0.04
0.03
2.94
2.94
2.14
1.72
1.60
0.83
0.33
0.22
0.21
0.10
1.18
0.43
6.43
0.35
0.21
9.33
3.78
2.00
0.71
0.42
0.17
0.87
0.45
0.35
3.96
2.47
1.32
0.96
1.20
0.83
0.64
0.23
0.09
0.07
0.04
0.03
2.52
2.52
1.84
1.47
1.37
0.73
0.27
0.17
0.16
0.08
1.06
0.39
5.51
0.31
0.19
8.51
3.30
0.17
0.59
0.36
0.13
1
2
3
MF 020
74.00
29.20
22.00
50.08
24.12
19.00
20.00
8.00
6.56
16.00
7.22
5.33
9.00
5.00
4.33
6.43
3.33
1.68
5.51
2.85
1.44
4.40
2.00
1.30
0.22
0.13
0.11
1.25
1.10
0.96
0.82
0.15
0.13
0.12
0.11
0.03
0.03
0.02
0.02
1.60
1.37
1.34
1.34
1.34
0.09
0.08
0.08
0.08
0.04
0.26
0.12
3.40
0.11
0.06
1.25
1.25
1.10
0.25
0.09
0.04
CU 850
Return filters
*
∆pc = 0.03 bar ( see graphic below, considering size 100 with the
max available lenght to get the lowest pressure drop)
∆pe = (2.0 : 1000) x 120 x (46/30) = 0.37 bar
∆p Tot. = 0.03 + 0.37 = 0.4 bar
The selection is correct because the total pressure drop value is inside
the admissible range for top tank return filters. It is of course possible
trying to find a different solution, according to the mounting position
or to other commercial need, repeating the previous steps while using
a different series or lenght.
6.88
4.00
2.50
2.00
Introduction
20