The KOBOLD KSK is an all-plastic variable area flow meter and switch designed for low flow rates of aggressive chemicals and standard fluids. Commonly referred to as a rotameter, it combines American manufacturing quality with economical plastic construction, providing visual flow indication with optional switch points for automated control in chemical processing, water treatment, and general industrial applications.
Water models measure flow rates from 0.006...0.05 GPM up to 0.44...4.4 GPM, air models cover 0.06...0.27 SCFM up to 11.8...62 SCFM, and every version maintains ±4% full scale accuracy at pressures up to 145 PSIG, according to specifications.
How the KSK Variable Area Rotameter Works
Fluid flow raises a float within a tapered tube, a simple, proven principle that delivers direct visual indication without requiring external power or complex electronics. This variable area design ensures consistent performance whether monitoring corrosive chemicals or standard process fluids.
Two Tube Materials for Standard and Aggressive Media
The KSK series offers two material configurations. Polyamide versions provide cost-effective measurement for non-corrosive media, including water, oils, and compatible gases, from 32 to 140°F (0 to 60°C). Polysulfone models excel in demanding chemical environments, resisting acids, alkaline solutions, and temperatures up to 212°F (100°C) with brass or stainless steel fittings and no switch fitted.
This material versatility allows facilities to standardize on one flow meter design across multiple applications, simplifying inventory management and maintenance procedures while helping reduce total ownership costs. Every version uses a PVDF float for universal chemical compatibility and EPDM O-ring seals for broad chemical resistance.
Compact Design for Space-Constrained Installations
With installation lengths as short as 6.5 inches on smaller models, the KSK rotameter fits where other instruments cannot. All-plastic construction eliminates corrosion concerns in washdown environments, the shock-resistant design withstands typical industrial handling, and the meter may be inserted or removed radially for convenient servicing, with clear, easy-to-read scales for instant visual flow verification.
Made in USA, BABA Compliant for Government Projects
Manufactured in the United States, KSK rotameters meet Build America, Buy America (BABA) requirements for federally funded infrastructure projects. This compliance supports eligibility for water treatment facilities, municipal systems, and government installations requiring domestic sourcing, and the combination of American-made quality and competitive pricing provides procurement advantages for public sector applications.
These domestically produced rotameters help ensure consistent availability, backed by KOBOLD's technical support and fast delivery from our USA facility.
Reed or Transistor Switches for Automated Monitoring
Optional bistable switches transform the KSK from a simple visual indicator into an automated monitoring solution. Choose reed contacts for basic on/off control or NPN transistor switches with LED status indication; up to two switches mount directly to the meter body with adjustable setpoints across the full scale range, enabling alarm functions, pump control, or process automation without additional instrumentation.
The reed contact is SPST, normally open or normally closed based on the order code, rated for a maximum of 130 VAC, 10 W/10 VA, and 0.5 A. The transistor option is a bistable Hall sensor with NPN open collector output, operating on 9 to 24 VDC with a maximum signal of 100 mA, and its LED lights when flow is above the setpoint. Both carry IP65 protection.
Direct Reading Scales for Water and Air
Measuring scales are available for water or air. Water scales read directly in GPM, GPH, LPH, or LPM depending on the ordering code, while compressed air scales read directly in SCFM and are calibrated for outlet pressures from 0 to 145 PSIG. Air units are available only with the Polysulfone measuring tube.
KSK Technical Specifications
The specifications below summarize the KSK's documented ratings: water and air measuring ranges, pressure and temperature limits by tube material and fitting type, wetted materials, connection options, and switch ratings, all according to the current KOBOLD datasheet, whose ordering table lists the exact range and scale options for each size.
- Accuracy: ±4% of full scale
- Water ranges: 0.006...0.05 to 0.44...4.4 GPM; pressure drop 0.07 to 0.12 PSI maximum
- Air ranges: 0.06...0.27 to 11.8...62 SCFM, scale calibrated at 0 to 145 PSIG outlet pressure
- Maximum pressure: 145 PSIG
- Media temperature: Polyamide 32 to 140°F (0 to 60°C); Polysulfone up to 140°F (60°C) with PVC fittings, 185°F (85°C) with brass or SS fittings and switch, 212°F (100°C) with brass or SS fittings and no switch
- Materials: Polyamide or Polysulfone measuring tube; PVDF float; EPDM O-rings; connection per ordering code
- Connections: PVC glue socket or female NPT, 3/8" to 1"; brass or 316 SS NPT options on select sizes
- Mounting: vertical, flow up
- Switch options: reed SPST N/O or N/C, max. 130 VAC, 10 W/10 VA, 0.5 A; NPN transistor, 9-24 VDC, max. 100 mA, hysteresis less than 0.24 in (6 mm); IP65; ambient max. 130°F (54°C)
Common Questions about KSK - All-Plastic Low-Flow Flow Meter and Switch
The KSK is based on the well-known suspended float principle: the medium flows from below through a conical plastic measuring tube, raising the float, and the flow rate is read off against the scale. The instruments measure and monitor flows in closed pipes and can be fitted with bistable switches.
The ten meter sizes cover water from 0.006...0.05 GPM at the low end up to 0.44...4.4 GPM, with maximum pressure drops of only 0.07 to 0.12 PSI. Air versions span 0.06...0.27 SCFM through 11.8...62 SCFM depending on meter size and scale calibration pressure.
Air scales are graduated in SCFM and calibrated to a specified outlet pressure between 0 and 145 PSIG, so readings are direct at your actual operating pressure. The ordering code selects the calibration pressure, and only the Polysulfone tube version supports air service, per the datasheet.
Polyamide suits non-corrosive media such as water, oils, and compatible gases and carries the lower cost. Polysulfone is highly resistant to acidic and alkaline solutions and reaches higher temperature ratings, so it is the choice for aggressive chemicals, and it is also required for compressed air scales.
Every model is rated to 145 PSIG. The Polyamide tube operates between 32 and 140°F (0 and 60°C). Polysulfone limits depend on configuration: PVC fittings cap the meter at 140°F (60°C), while brass or stainless steel fittings allow 185°F (85°C) when a switch is mounted and 212°F (100°C) without one.
Two contact types exist: a reed switch, SPST in normally open or normally closed form per the order code, limited to 130 VAC, 10 W/10 VA, and 0.5 A; and a bistable Hall sensor transistor switch, NPN open collector, 9 to 24 VDC and 100 mA maximum, whose LED indicates flow above the setpoint. Protection is IP65.
Slide the switch housing along the meter using the red sliders until the reference edge lines up with the desired scale reading: the bottom edge of the housing for falling flow, or roughly 0.2 in (5 mm) above it for rising flow. To initialize a bistable switch, the float must activate the contact once in each direction.
Install the meter vertically in the piping with flow upward. Remove all transportation safety locks and packing material, keep the unit free of mechanical stress (add support bracing if necessary), protect the measuring tube from external damage and pressure peaks, keep bistable reed versions out of inductive fields, and check connections for leakage right after mounting.
With a clean medium the series is virtually maintenance-free. If deposits form on the inner housing or parts, periodic cleaning is recommended: remove the unit from the piping with a suitable tool and clean it with a suitable cleaning agent, or make use of an ultrasonic bath.
Yes. KSK rotameters are produced domestically, and BABA compliant models are available for federally funded work such as water treatment plants and municipal systems that require domestic sourcing. US production also supports fast delivery and consistent availability compared with imported variable area meters.