Application for Rheotherm and RheoVac Instruments

Flow Switches

Rheotherm flow switches provide reliable switch protection in all Inline flow switchtypes of liquid or gas service. From critical monitoring of extremely low flow process additives to loss of flow protection in large water or air lines, we can handle most flow switch applications. With no moving parts in these devices, their long-term reliability is assured. Options for hazardous sites (explosion-proof, intrinsically safe) are available as well. These devices, like all Rheotherm flow instruments, are protected by an ISO-9001:2000 certified Quality Assurance program.

Overview of Flow Switches

Flow switches play an important role in regulating the flow rate of fluids through a system. They perform this function by sending a trip signal to another system element (often a pump) that responds by modifying the fluid flow rate as needed. Flow switches are also used for indication of certain process conditions such as flow/no-flow to alert operating personnel by connecting them to indicator lights or audible alarms.

Every flow switch has a set point, which is a maximum or minimum flow rate. The set point is typically user-adjustable. When the flow of media reaches the existing set point, the switch prompts the pump (or other mechanism) to turn on or off. The switch can be set to trigger in either low-to-high (e.g., trigger when flow goes from 0 to any flow) or high-to-low (e.g., trigger when flow goes to 0 from any flow value) to match the process requirements. This sequence of events results in the increase or decrease of the flow rate, depending on the requirements of the application.

What Kind of Service Can Our Flow Switches Provide?

You name it—all types of liquids and gases, big pipes or small lines, hot or cold. Here is an incomplete partial listing of the types of fluids that Rheotherm in-line flow switches have been used to monitor:

  • Ammonia
  • Antifoam
  • Argon
  • Butane
  • Carbon Dioxide
  • Carbon Monoxide
  • Chlorine
  • Coal Gas
  • Coke Gas
  • Diesel Exhaust
  • Digester Gas
  • Ethane
  • Ethanol
  • Ethylene
  • Ferric Chloride
  • Flare Gas
  • Flue Gas
  • Fluorine Gas
  • Fuel
  • Helium
  • Hydrocarbon Gas
  • Hydrofluorosilicic Acid
  • Liquid Chlorine
  • Methane
  • Natural Gas
  • Oxygen
  • Propane Vapor
  • Propylene
  • Sulfur Dioxide
  • Tungsten Hexafluoride

As one of the leading thermal flow switch manufacturers active today, we’re proud to note that these state-of-the-art devices have been successfully in thousands of installations. They can be found in a broad range of applications, from HVAC systems to water treatment facilities. Industries that currently use our air, liquid, and gas flow switches include:

  • Aerospace
  • Chemical and Petrochemical
  • Natural Gas
  • Oil and Gas Production
  • Wastewater Treatment
  • Pulp and Paper

The Applications section has a complete list of fluids that our low flow switches have been used with. Contact us with any questions about your specific application.

How Are They Installed?
Insertion flow switchOur in-line flow switches for monitoring flows in small lines are usually installed with standard tube fittings, but are optionally available with flanges, NPT, sanitary fittings, etc. Insertion probe flow switches for monitoring large (1” or larger) pipe flows are typically installed with 1” NPT or flange fittings. They can be used in vertical or horizontal lines. For most common applications, the sensor and electronics form an integral unit.

How Do They Work?

Rheotherm flow switches and monitors come with highly advanced thermal flow-sensing technology to ensure optimal performance. Our in-line flow sensors use a straight-through flow tube with a heated and an unheated RTD (Resistance Temperature Detector) attached to the outside of the tube. The insertion probe flow sensors include one tip with a heated RTD and another tip with an unheated RTD. With both sensor styles, the temperature differential between these two RTDs produces the primary flow signal. At high flow rates, flow removes more heat, resulting in a lower differential. At low flow rates, the flow removes less heat, so the differential is higher.

With our inline industrial flow sensors, nothing touches the fluid but the metal sensor wall, and there are no mechanical parts that are susceptible to wearing, sticking, or breaking. We use unstressed components to enable years of low-maintenance operation. The sensor will not be damaged when the process flow stops or when the line empties.

Trip points are field adjustable, so you are always able to adapt quickly to changes in system conditions. Trip response times generally range from 2 to 25 seconds and can optionally be extended with a time delay. Our flow switches can operate in environments in the range of 0–120°F (-18–50°C); optional customizations can extend this range to -20–400°F (-29–200°C). Standard wetted parts are Grade 316 stainless steel, with other materials optionally available. More on Method of Operation (PDF)

Rheotherm sensor

Inline Sensor

Pipe and duct flow sensing

Insertion Sensor

 

What Models Are Available?

We currently offer the following flow switch models:

Model 100CS – Lowest cost industrial option. Integral sensor/electronics with one SPDT relay, which is rated 10 A @ 120 Vac or 5 A @ 24Vdc. CE mark is available. Can be ordered with in-line or insertion probe sensor.

Model 100FS – Separate sensor and electronics with one SPDT relay. Option for second relay for high and low set points. Can be ordered with in-line or insertion probe sensor. This model is also available with an intrinsically isolated sensor for use in hazardous locations. Refer to the Instruments for Hazardous Locations page for more information.

Model 400 – Integral insertion probe sensor and electronics; has two SPDT relays or single relay w/ non-linear analog flow output signal. Calibrated signal optional.

Model 500 flow switch

Model 500 – In-line design with your choice of 1/16” O.D. or 1/8” O.D. flow tube connection options. Low flow switch for certain general-purpose applications; 24 VDC input power only.

Feel free to contact us if you’re uncertain about which model works best with your application.

How Do I Get One?

Submit your flow switch inquiry today using the form on this page, or visit our contact us page for telephone, fax, and email information.

  • No moving parts
  • Exclusive inline TU sensor
  • Advanced signal processing electronics
  • Field adjustable switch point
  • Maintenance-free
  • Easy installation
  • Choice of wetted materials
  • Long-term reliability

 

 StandardOptions
Temperature Process: 0 – 140°F
(-18 – 60°C)
Environment: 0 – 120°F
(-18 – 50°C)
Inline: -20 – 350°F
(-30 – 175°C)
Probe: -20 – 400 °F
(-30 – 200 °C)
Pressure 0 – 1,000 PSIUp to 30,000 PSI
Calibration Accuracy  ± 1% of reading typical
Response Time  1 sec. ; 3 – 5 sec. typ.
(63% of range);
Time constant/delay option
Repeatability ± 0.5% of reading
 StandardOptions
Line SizesInline sensor (flow range dependent):
– Capillary;
– 1/16”; 1/8”; 3/16”; 1/4”
– 3/8”; 1/2”; 5/8”; 3/4”; 1”
Probe sensor:
Pipe/Duct from 1.5” – 72”
(round, square, rectangular)
Other sizes via fittings/adapters
Process ConnectionInline sensor: Plain tube stubs suitable for compression fittings
Probe sensor:
1″ MNPT
– MNPT;
– Tri-Clover (Sanitary);
– SS Flange (1/2” – 2”);
Most other fittings available
Wetted Material316 SS– Hastelloy C-276®;
– Monel®;
– Alloy 20;
– Titanium;
– Tantalum;
– Inconel
 StandardOptions
EnclosureSensor:
– Inline – PVC
– Probe – NEMA 4X (junction box)
Electronics:
– Integrated – NEMA 4X Cast Aluminum
– Remote – NEMA 4
Inline sensor: Stainless steel
Remote electronics
:
– Stainless steel
– NEMA 7 Explosion-proof
Hazardous Environment Remote electronics with 100FS only
FM Approved for:
– Class I, Div. 1, Groups A,B,C,D
– Class I, Zone 1, IIB+H2 (US)
– Class II, Div. 1, Groups E, F, G
– Class III, Div. 1
OutputsSingle SPDT Form C relay
(10A, 125 VAC)
Remote electronics with 100FS only
– Second independent SPDT relay
– DPDT relay
– Time delay on switch
Input Power110/230 VAC ±10V24 VDC ±4V (200 mA)

Inline Sensor Flow Capacities for Liquids

TUBE SIZE
FLOW RATE LIMITSC1/161/83/161/43/81/25/8*3/4*1*
Extended Maximum2605000.412.54.681020
Normal Maximum1302500.250.5123.54.58
Normal Minimum0.030.860.0080.010.030.050.20.30.5
Extended Minimum0.0070.0530.0020.0060.010.020.070.10.2
cc/minGPM

*Limited applications. Consult Factory


Inline Sensor Flow Capacities for Gases

TUBE SIZE
FLOW RATE LIMITSC1/161/83/161/43/81/25/83/41
Extended Maximum0.0271.25511204580125180320
Normal Maximum0.0170.7537153470109160280
Normal Minimum0.00170.020.10.20.40.91.62.53.66.4
Extended Minimum0.00090.00170.050.10.20.50.81.223.2
SCFM

1
2

Probe-type Sensor Flow Capacities for Gases

NPT/2I
VELOCITY LIMITS (ft/min)Liquid*Gas
Maximum15025,000
Minimum0.525

*Liquid Applications limited to Flow Switches only

 

pdf (1) Product Brochure
wordRheotherm Flow Application Data Sheet
(download document)
pdf (1)Rheotherm Method of Operation
pdf (1)Standard Dimensions Insertion Probe Sensor
pdf (1)Rheotherm Sensor Selection Guide
pdf (1)Standard Dimensions Inline (TU/TUL) Sensor
pdf (1)Rheotherm Model Selection Guide
pdf (1)Model 500 Flow Switch Product Brochure
pdf (1)Rheotherm Model 100CS Product Manual
pdf (1)Rheotherm Model 100FS Product Manual

 

Request a Quote

Required fields are indicated with an ‘*’Name*

Email*

Phone

Company

City, State/Prov.

Fluid*

Flow Range* (incl. units)

Fluid Temp.* (indicate °F/°C)

Max Temperature* (incl. units)

Max. Pressure* (incl. units)

Continuous or Batch Flow*
ContinuousBatch
Batch/Pulse Time

Switch Setpoint*

Pipe/Duct/Size*

Process Fittings

Flange Size/Rating

Input Power*

Desired Output* (ctrl-click for multiple)
Additional Requirements
(Hazardous environment, certificates, etc.)