Steam Flow Rate Transmitter

Food Processing, Pulp and Paper Textile Industries, Chemical Processing
Repeatable Results, Eliminates Guesswork Saves Energy, Speeds Equipment Start-Up
  • Analog Output Signal - 4-20mA
  • Fully Calibrated
  • Mechanical Panel Gauge
  • Stainless Steel Construction
  • Affordable and Reliable
  • Easy to Install
  • True Mass Flow Even With Changing Line Pressure


Designed for the accurate measurement and control of process steam for end-of-the-run applications: steam injection to process ovens, atmospheric blanchers, sparging tanks, direct steam to product tanks, and other applications where steam is exhausted through a pipe manifold or nozzles to near atmospheric pressure.

The steam flow rate transmitter will supply an analog output signal suitable for driving remote digital indicators, chart recorders, or closing the loop to a process controller. Analog output signals may be specified as 0-5VDC, 4-20mA, or 0-20mA. A pressure transducer with additional signal conditioning electronics is packaged within the transmitter housing to provide a linear signal proportional to mass flow rate over the full rate range. Mass flow rate is metered from zero flow to full scale capacity. In addition, a calibrated panel gauge is included for local indication of the steam flow rate.

Electrical connections are made through a watertight connector on the enclosure. Control power and signal wires connect to numbered screws inside the connector cover. The connector will thread to liquid-tight electrical conduit.

Installed in series with the steam piping, the transmitter is inherently simple and rugged. There are no moving parts to maintain or replace. There are no obstructions in the steam flow path.

Internal wetted parts are manufactured from 300 series stainless steel for long-term durability and corrosion resistance. Metering components were selected to withstand demanding industrial use including continuous operation, repeated chemical washdown, and outdoor applications.

Principle of Operation

Principle of Operation

The steam flow rate transmitter does NOT require calibration at a fixed upstream operating pressure. Differential pressure is NOT measured. Mass flow rate is strictly proportional to the pressure at the inlet of the critical flow venturi.

For the system to operate correctly, a small pressure drop across the nozzle is required. The proprietary design is such that the exit pressure may be as high as 90% of the inlet pressure for acceptable operation. Steam to atmosphere and open tank applications easily meet these operating conditions.


The transmitter is an in-line device which will operate in any flow orientation. If desired, the transmitter may be reconfigured in the field to a different flow direction.

The steam flow rate is controlled by throttling on the inlet side of the transmitter. Manual and specialty control valves, or pressure regulators may be used as pressure reducing devices.

When required, non-standard capacities, special construction, or other optional features can be provided.

  • Rated Pressure
    • 150 PSIG Max.
  • Ambient Temperature
    • 40°F to 140°F
  • Absolute Pressure Ratio (Exit to Inlet)
    • 90% Max.
  • Analog Output Signals
    • 0-5VDC, 1-5VDC, 4-20mA, 0-20mA
  • Power
    • 24VDC Nominal, 50mA Max.
  • Accuracy
    • ±5 F.S.
Ordering Information

Steam flow rate transmitters are described by indicating the following combination of product features.

(Product Code)-(Steam Capacity LB/HR)-(Pipe Size)-(End Connections)- (Flow Direction)

Product code is STMT. End Connections F for Flange (raised face). Flow Direction selections are VD (vertical down), VU (vertical up), HR (horizontal right), or HL (horizontal left). Analog Signal selections are 005 for 0-5VDC, 020 for 0-20mA, and 420 4-20mA.

Example: STMT - 1000 - 1.5 - F - HR - 420 is a steam flow rate transmitter with a full scale capacity of 1000 LB/HR, end connections are 1 1/2" Flange, with a horizontal flow direction, downstream to the right. The analog output signal is specified as 4 to 20mA.

Standard Transmitters
(Full Flow at 75 PSI) (Full Flow at 85 PSI)
STMT-250-1 -F-XX STMT-125KG-1 -F-XX
STMT-500-1 -F-XX STMT-250KG-1 -F-XX
STMT-1000-1.5 -F-XX STMT-500KG-1.5 -F-XX
STMT-1500-1.5 -F-XX STMT-750KG-1.5 -F-XX
STMT-2500-2 -F-XX STMT-1250KG-2 -F-XX
STMT-3000-2.5 -F-XX STMT-1500KG-2.5 -F-XX
STMT-5000-3 -F-XX STMT-2500KG-3 -F-XX

Consult the factory for special configurations.