General Installation Information
GENERAL INSTALLATION INFORMATION
Before installing the meter:
• Find an area for installation away from large electrical motors, transformers or other devices that can produce high electromagnetic or electrostatic fields The vortex transmitter contains electric circuitry that can be affected by these interferences
• Proper grounding is required to eliminate electrical noise which may be present within the fluid and piping system or in the near vicinity of the vortex transmitter Use exterior grounding strap for non-conductive piping systems to provide a path to earth ground Properly ground pipes in conductive piping systems
Flow Rate and Range Requirements
Most manufacturers state flow range capabilities by publishing the maximum allowed flow rates Then they provide a turndown ratio to determine minimum flow rate To use the turndown ratio, simply divide the maximum rate by the ratio to determine the minimum rate Vortex flow meters have a 12:1 turndown ratio at a viscosity of 1 cSt Higher viscosities will reduce the turndown
N OTEE:
The 1/4 in NPT and 1/2 in flare end meters have a standard turndown ratio of 8:1
Piping Requirements
Turbulence in the pipeline can affect the accuracy of flow meters Typical sources of turbulence are pumps, valves, change in pipe diameter or changes-in-direction in the line Install the meter away from the turbulence source to avoid turbulence issues These distances are indicated in Pipe Diameters (PD) For example, 10 PD is ten times the inside pipe diameter away from the source of turbulence Follow upstream and downstream distances for all sources of turbulence See
Figure 2 on page
7
,
Figure 3 on page 8
,
Figure 4 on page 9
and
Figure 5 on page 9
for proper piping distance requirements
N OTEE:
Pulsating flow affects accuracy Pressure pulses affect accuracy
Page 6 VRX-UM-00371-EN-02 August 2015
Configuration
1 plane change
1 plane change w/outlet valve
2 plane changes
2 plane changes w/outlet valve
General Installation Information
Piping Requirements
(pipe diameters)
Inlet Outlet
20
5
10
27
5
10
20 Dia
Minimum
Flow
5 Dia
Minimum
Accuracy
(full scale)
±1 00%
Repeatability
(of point)
0 25%
20 Dia
Minimum
Flow
10 Dia
Minimum
Two Plane
Changes
27 Dia
Minimum
Flow
5 Dia
Minimum
Two Plane
Changes
27 Dia
Minimum
Flow
10 Dia
Minimum
Figure 2: Horizontal flow with sensing element in vertical orientation
August 2015 VRX-UM-00371-EN-02 Page 7
General Installation Information
Configuration
1 plane change
1 plane change w/outlet valve
2 plane changes
2 plane changes w/outlet valve
Piping Requirements
Inlet Outlet
20 PD
5 PD
10 PD
27 PD
5 PD
10 PD
20 Dia
Minimum
Flow
5 Dia
Minimum
Accuracy
(full scale)
±1 50%
Repeatability
(of point)
0 25%
20 Dia
Minimum
Flow
10 Dia
Minimum
Two Plane
Changes
27 Dia
Minimum
Flow
5 Dia
Minimum
Two Plane
Changes
27 Dia
Minimum
Flow
10 Dia
Minimum
Figure 3: Horizontal flow with sensing element in horizontal position
Page 8 VRX-UM-00371-EN-02 August 2015
August 2015
Configuration
1 plane change
1 plane change w/outlet valve
2 plane changes
2 plane changes w/outlet valve
Two Plane
Changes
Piping Requirements
Inlet Outlet
20 PD
5 PD
10 PD
27 PD
5 PD
10 PD
Two Plane
Changes
General Installation Information
Accuracy
(full scale)
Repeatability
(of point)
±1 00% 0 25%
27 Dia
Minimum
27 Dia
Minimum
20 Dia
Minimum
20 Dia
Minimum
10 Dia
Minimum
5 Dia
Minimum
10 Dia
Minimum
Figure 4: Vertical flow with a change in direction or valve
25 Dia
Minimum
Flow
5 Dia
Minimum
20 Dia
Minimum
10 Dia
Minimum
2 Dia
Minimum
25 Dia
Minimum
Flow
5 Dia
Minimum
20 Dia
Minimum
5 Dia
Minimum
2 Dia
Minimum
Two Plane
Changes
30 Dia
Minimum
Flow
5 Dia
Minimum
5 Dia
Minimum
25 Dia
Minimum
2 Dia
Minimum
Figure 5: Horizontal flow with a change in pipe diameter
VRX-UM-00371-EN-02
5 Dia
Minimum
Page 9
General Installation Information
Back Pressure
Back pressure, the pressure immediately downstream of the meter, must be maintained above a minimum level to avoid cavitation For most applications this may be ignored if the flow rate is less than 75% of maximum For other applications, use the following formula to calculate the minimum back pressure
Back Pressure = 2 75
∆
P + 1 25 PV - 14 7
Where:
∆
P = Pressure drop in psi at max flow
PV = Vapor pressure in psia of the liquid at operating temp
(For example, the PV of water at 100° F is 0 42 )
BP = Back pressure (downstream of meter) in psig
Example
For water, at 100° F (37° C) in a 1/2 in (12 7 mm) meter, where the maximum pressure drop is 8 psi minimum back pressure is
7 8 psig
BP = (2 75 × 8) + (1 25 × 0 42) - 14 7
BP = 22 + 0 525 - 14 7
BP = 7 825
Outputs
The RVL series meters can be ordered with either an analog output (voltage or current) or a rate frequency output The standard analog output is a 4…20 mA current, an optional 0…5V DC is also available The analog output can be re-scaled in the field using a PC communications cable and programming software, which are both available as P N RVS220-954
N OTEE:
All three outputs use unique circuit boards and cannot be changed in the field
The rate frequency output produces pulses whose frequency is proportional to the flow going through the meter Each meter
has a slightly different output frequency which is listed on the calibration sheet that accompanies the meter See
Table 2
for the long term average full scale output frequency for standard size meters
Meter Size
1/4 in (6 35 mm)
1/2 in (12 7 mm)
1/2 in (12 7 mm)
3/4 in (19 05 mm)
1 in (25 4 mm)
1-1/2 in (38 1 mm)
2 in (50 8 mm)
3 in (76 2 mm)
Average Full Scale Frequency
1055 Hz
820 Hz
570 Hz
284 Hz
292 Hz
144 Hz
148 Hz
61 Hz
Table 2: Full scale output frequency
Pulse Width
0 47 msec
0 61 msec
0 88 msec
1 76 msec
1 71 msec
3 47 msec
3 38 msec
8 20 msec
The frequency output option generates a square wave with an amplitude that matches the input power level The pulse width varies with frequency and is found by using the following formula
PW in sec. =
1
2 x Maximum Frequency (Hz)
K-Factors
The K-factor is the number of pulses that must be accumulated to equal a particular volume of fluid Think of each pulse as representing a small fraction of the totalizing unit
Calibration reports that accompany RVL series meters include a nominal K-factor in both gallons and liters See
“Calibration
Certificate Sample” on page 23
Page 10 VRX-UM-00371-EN-02 August 2015