Made in USA Paddle Flow Switch for Industrial Liquid Monitoring
The KOBOLD PSR/PS is a paddle type flow switch for liquids that provides simple, economical, and reliable flow monitoring in industrial applications. It is manufactured in Pittsburgh, Pennsylvania, comes in brass or stainless steel construction, and BABA compliant models are available for federally funded projects.
This industrial grade flow switch operates through a simple, proven mechanical principle. Flowing liquid presses against a paddle attached to a balance arm, and a permanent magnet at the opposite end of the arm actuates a reed contact housed outside the flow media. The contact can be set as normally open or normally closed, so the switch status can be used to control flow.
High-Pressure Performance with Material Options
Two body styles cover pipe sizes from 1/4" to 8". The inline PSR is offered with 1/4" NPT to 1-1/2" NPT fittings, while the insertion style PS mounts through a 1/2" NPT connection and is designed for installation in 2" to 8" pipes.
Available in both brass and stainless steel construction, the PSR/PS handles a wide variety of media. Wetted parts use corrosion resistant materials, including a 304 stainless steel paddle and a 301 stainless steel leaf spring, with NBR seals on brass models and FKM seals on stainless steel models. According to specifications, stainless steel bodies in 1/4" through 1" sizes are rated to 3625 PSIG and brass bodies to 1450 PSIG, while 1-1/4" and 1-1/2" sizes are rated to 580 PSIG in stainless steel and 360 PSIG in brass. Media temperature spans -4 to 158 °F (-20 to 70 °C) for brass with NBR seals and -4 to 230 °F (-20 to 110 °C) for stainless steel with FKM seals.
Adjustable Switch Points for Application Flexibility
The externally adjustable switch housing eliminates the need to shut down systems for setpoint changes. Operators fine tune the switching range by repositioning the contact unit along marked adjustment aids, and the design allows either normally open or normally closed operation from the same standard contact.
Switching tolerance is ±15%, with increasing and decreasing flow values defined for every model. Standard and special switching ranges run from 0.6...1.2 GPM on a 1/4" PSR up to 185...242 GPM on a PS monitoring a 6" line, so a single product family serves everything from small cooling circuits to large water distribution systems.
Designed for Reliability
IP65 ingress protection keeps dust and water away from the external switch electronics, and the contact tube is made of glass reinforced polyamide for electrical insulation and durability. Models PSR-..05 through PSR-..25 add a pressure resistant forged case.
A baffle plate system made of spring stainless steel precludes bending of the paddle even when flow runs well beyond the switching range, and the baffle plate itself is exchangeable. This design helps protect the instrument through process upsets and simplifies long term maintenance.
BABA Compliance for Federal Projects
The PSR/PS paddle flow switch qualifies as a BABA compliant product, manufactured in Pittsburgh, Pennsylvania. That status supports procurement on projects subject to Build America, Buy America domestic content requirements, and cCSAus certified contact ratings support installations across the United States and Canada.
Applications Across Industrial Markets
Common applications include cooling and lubricant circuits, dry running protection for pumps, prevention of low water levels, and monitoring for pipe breakage. HVAC systems rely on it to protect chillers, manufacturing plants verify lubricant flow, water treatment facilities watch for line breaks, and fire suppression and eye wash stations confirm adequate flow.
Horizontal mounting is recommended, and published switching values are valid for horizontal installations. Straight inlet and outlet runs of at least five pipe diameters help ensure stable, repeatable switching. Because operation is purely mechanical, the switch needs no power beyond its own contact circuit, which keeps installation simple and operating cost low.
Common Questions about PSR/PS - Paddle Flow Switch
Liquid moving through the line deflects a paddle fixed to a balance arm that rides on a pre stressed leaf spring. A magnet at the arm's far end trips a bistable reed contact sealed in a movable housing away from the media, so the circuit opens or closes as flow rises and falls.
PSR models thread directly into the line in seven connection sizes, 1/4" NPT through 1-1/2" NPT. The PS version carries a 1/2" NPT mounting thread and inserts into larger lines, from 2" through 8" pipe, typically through a tee or fitting on the run.
Maximum pressure depends on body material and connection size. Brass units are rated 1450 PSIG in 1/4" through 1" sizes and 360 PSIG in the 1-1/4" and 1-1/2" sizes. Stainless steel units carry 3625 PSIG and 580 PSIG ratings for those same two size groups.
Temperature limits follow the seal material. Units with NBR seals handle media from -4 to 158 °F (-20 to 70 °C), and units with FKM seals handle -4 to 230 °F (-20 to 110 °C). Ambient temperature is rated -4 to 158 °F (-20 to 70 °C) in either case.
Yes. Slightly loosening the two screws that secure the locking washer at the top of the casing frees the contact unit to slide, with blue/white and red arrows serving as guides for the normally closed and normally open settings. Moving the unit with or against the flow direction sets minimum or maximum switching values.
An SPST contact is standard, rated 2 A at 20 VAC or 0.18 A at 230 VAC, 40 W maximum under cCSAus. The optional SPDT version is rated 0.13 A at 150 VAC or 0.5 A at 40 VAC, 20 W maximum. PVC jacketed cable runs 5 ft (1.5 m) standard, or 10, 15, or 21 ft on SPST models.
Yes. KOBOLD builds the PSR/PS at its Pittsburgh, Pennsylvania facility, and versions that satisfy BABA sourcing rules can be specified for government funded infrastructure work that requires them. The product line is also flagged for quick delivery, which helps when project schedules are tight.
Any mounting position is permitted except for PSR-..32 and PSR-..40, which are horizontal only, and listed switching values assume horizontal runs. The top half of the switch must sit vertical to the pipe axis, the arrow on the fitting must match flow direction, and 5 x DN of straight pipe belongs before and after the device.
With clean media the instrument remains virtually maintenance free. Ferritic particles can deposit on the magnet and larger dirt particles can block the balance arm, so a magnet filter such as KOBOLD model MFR is recommended for iron bearing media, along with periodic cleaning of the paddle arm and upper housing.
The switch carries cCSAus certification covering its maximum contact ratings, for both the standard SPST version and the optional SPDT version. Separately, the enclosure is rated IP65 against dust and water intrusion, a rating that applies to the switch housing rather than to the electrical contacts themselves.
Product Specifications
PSR Switching Ranges
0.6...1.2 GPM to 11.9...18.0 GPM
PS Switching Ranges
13...16 GPM to 185...242 GPM
Fittings
1/4"...1-1/2" NPT Thread
Max. Pressure
1450 PSIG (Brass) / 3625 PSIG (SS)
Max. Temperature
230 °F (110 °C)
Reed Switch Contact
SPST Standard, SPDT (Optional)
Product Features
Certifications/Approvals: cCSAus
Sample Application Areas: Chillers, Cooling Circuits, Pump Protection, Water Fire Suppression, Eye Wash Stations & More
BABA (Build America, Buy America) compliant models available
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Common PSR - PS Questions