Flow Switches

Rheotherm flow switches provide reliable switch protection in all types 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, long term reliability is assured.  Options for hazardous locations (intrinsically safe/explosion-proof) are available.

What Kind of Service?
You name it – all types of liquids and gases, big pipes or small lines, hot or cold. The application section has a complete list of fluids.  Contact Us about any application you have.

How Are They Installed?
Our in-line flow switches for monitoring flows in small lines are typically 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. Can be used in vertical or horizontal lines. For most common applications, the sensor and electronics are an integral unit.

How Do They Work?
Our in-line sensors use a straight-through flow tube with a heated and an unheated RTD attached to the outside of the tube. The insertion probe flow sensors have one tip with a heated RTD and a second tip with an unheated RTD. With either sensor style, the temperature differential between the two RTDs provides the primary flow signal. At high flow rates, flow removes more heat resulting in a lower differential. At low flow rates, flow removes less heat so the differential is higher. Nothing touches the fluid but the metal sensor wall, and there are no mechanical parts to wear, stick or break. Trip points are field adjustable. More on Method of Operation (PDF)

Inline Sensor

Insertion Sensor

What Models are available?
Model 100CS – Lowest cost industrial option.  Integral sensor/electronics with one SPDT relay.  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.

Model 400 – Integral insertion probe sensor and electronics; has nonlinear output signal option.

Model 500 – Flow switch for certain general purpose applications; 24 VDC input power only.

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

• FEATURES
• SPECIFICATIONS
• FLOW RANGES
• DOCUMENTATION

• 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

 

	Standard	Options
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 PSI	Up 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
	Standard	Options
Line Sizes	Inline 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 Connection	Inline 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 Material	316 SS	– Hastelloy C-276®; – Monel®; – Alloy 20; – Titanium; – Tantalum; – Inconel
	Standard	Options
Enclosure	Sensor: – 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
Outputs	Single SPDT Form C relay (10A, 125 VAC)	Remote electronics with 100FS only – Second independent SPDT relay – DPDT relay – Time delay on switch
Input Power	110/230 VAC ±10V	24 VDC ±4V (200 mA)

Inline Sensor Flow Capacities for Liquids

	TUBE SIZE
FLOW RATE LIMITS	C	1/16	1/8	3/16	1/4	3/8	1/2	5/8*	3/4*	1*
Extended Maximum	2	60	500	0.4	1	2.5	4.6	8	10	20
Normal Maximum	1	30	250	0.25	0.5	1	2	3.5	4.5	8
Normal Minimum	0.03	0.8	6	0.008	0.01	0.03	0.05	0.2	0.3	0.5
Extended Minimum	0.007	0.05	3	0.002	0.006	0.01	0.02	0.07	0.1	0.2
	cc/min			GPM

*Limited applications. Consult Factory

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Inline Sensor Flow Capacities for Gases

	TUBE SIZE
FLOW RATE LIMITS	C	1/16	1/8	3/16	1/4	3/8	1/2	5/8	3/4	1
Extended Maximum	0.027	1.25	5	11	20	45	80	125	180	320
Normal Maximum	0.017	0.75	3	7	15	34	70	109	160	280
Normal Minimum	0.0017	0.02	0.1	0.2	0.4	0.9	1.6	2.5	3.6	6.4
Extended Minimum	0.0009	0.0017	0.05	0.1	0.2	0.5	0.8	1.2	2	3.2
	SCFM

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Probe-type Sensor Flow Capacities for Gases

	NPT/2I
VELOCITY LIMITS (ft/min)	Liquid*	Gas
Maximum	150	25,000
Minimum	0.5	25

*Liquid Applications limited to Flow Switches only

 

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