Yokogawa Pressure Transmitters Mass Flow (Multivariable)

A Multi-variable transmitter combines a differential pressure transmitter, a gauge pressure transmitter, a temperature transmitter, and a flow computer into one unit.

The flow computer is programmed with application information and uses the three measured inputs to calculate the Mass Flow.

Like the Volumetric Flow, Mass Flow accuracy is determined by the accuracy entire system. This accuracy not only includes the hardware, but also the accuracy of the process parameters used to program the flow computer.

  • EJX930A

    EJX930A thumbnailDesigned specifically for high static pressure applications, this transmitter precisely measures differential pressure, static pressure, and process temperature; then uses these values in a high-perfomance on-board flow computer to deliver fully compensated Mass Flow.


  • EJX910A

    EJX910A thumbnailThis transmitter precisely measures differential pressure, static pressure, and process temperature; then uses these values in a high-perfomance on-board flow computer to deliver fully compensated Mass Flow.


  • FSA120

    FlowNavigator (FSA120) is a unique software tool that helps you get the most out of the EJX910A / EJX930A Multivariable Transmitter by supporting the configuration of the discharge coefficient, primary device bore, upstream internal pipe diameter, gas expansion factor, density, and viscosity data needed to perform full compensation and dynamic calculation of the mass flow.

    FSA120 thumbnail

Mass Flow Pressure Transmitters Introduction

Level transmitter configuration can be very time consuming. Calculations required to determine proper range values for traditional transmitters can become complex due to the physical layout of an application.

With maintenance shops getting smaller, finding equipment that allows us to do more with fens becomes a priority. DPharp transmitters with advanced software functionality can eliminate these complex calculations.

Mass Flow Pressure Transmitters Application

Using typical smart or conventional products, all the following must be considered:

The specific gravity of the process SGP
Precise location of 0% and 100%

Specific Gravity of the capillary fill fluid
(or sealing fluid used in impulse piping)

SGFF
Exact orientation oi the transmitter to the vessel H2
Vertical distance between the process conn. H1

Depending on the application, the vessel may be open (referencing atmosphere) or closed (under a blanket pressure).

Elevation is typically used when the vessel is closed. To reference the blanket pressure, a low side remote seal may be used (or a wet leg). The capillary on remote seal creates a negative force on the transmitter equal to the vertical height times the specific gravity of the fill fluid.

Elevation = (H1 + H2) x SGFF

Suppression is a positive pressure created on the high-pressure side of the transmitter typically due to the transmitter being positioned below the 0% process connection. Suppression is present in both open arid closed vessels. Suppression is equal to the vertical distance between the 0% process connection and the transmitter times the Specific Gravity of the fill livid.

Suppression = H2 x SGFF

Span is the vertical distance between the process connections times the process medium’s Specific Gravity.

Span = H1 x SGP

Figure 1: Closed Tank
Figure 1: Closed Tank

Now that you have the ElevationSuppression, and Span, the calibration values can be calculated for the 0% (Empty) arid the 100% (Full).

Cal Value (0%) = Suppression – Elevation

Cal Value (100%) = (Suppression + Span) – Elevation

Example: (using figure 1)

SGP 0.9 H2 10 inches
SGFF 0.8 H1 20 inches

Cal Value 0%) = Suppression – Elevation
Cal Value (0%) = (H2 x SGFF) – (H1 + H2 x SGFF)
Cal Value (0%) = (10 x 0.8) – (20 + 10) x 0.8
Cal Value (0%) = 8 – 24
Cal Value 0%) = -16 inH2O

Cal Value (100%) = (Suppression + Span) – Elevation
Cal Value (100%) = ((H2 x SGFF) + (H1 x SGP)) – (H1 + H2) x SGFF
Cal Value (100%) = ((10 x 0.8) + (20 x 0.9)) – (20 + 10) x 0.8
Cal Value (100%) = (8 + 18) – 24
Cal Value (100%) = +2 inH2O

Therefore, Calibrated Range would be:

-16 inH2O  +2 inH2O
0% 100%
Empty Full