The KOBOLD NIR-9 is a rotary paddle level switch that detects bulk solids in silos, hoppers, and bins. A slow-turning motor rotates a vane until material blocks it, actuating a micro-switch that signals the level condition. Sensitivity is adjustable across three settings, and operation is not affected by humidity or conductivity.
How the NIR-9 rotary paddle level switch works
A synchronous motor turns the vane at a low speed of 5 rpm. When bulk material reaches the vane and stops its rotation, the restoring force pivots the motor from its rest position and actuates a micro-switch that provides the alarm signal. A second micro-switch then switches the motor off.
When the level falls and releases the vane, a spring returns the motor to its operating position, the micro-switch resets, and the motor restarts. A green LED indicates that supply voltage is present.
Bulk materials and applications
The NIR-9 is designed for point level detection of solids and bulk media in tanks and silos. Documented example materials include cereal, grain, flour, granulated plastics, cement, sand, cocoa, sugar, feed, and perlite. Different vanes and process connections can be supplied to suit the material type and vessel size.
Minimum bulk density and sensitivity
Sensitivity is adjustable to three positions, low, medium, and high, by changing the spring position, with medium as the factory setting. The minimum detectable bulk density depends on the vane type and setting, starting at 2.37 lb/ft³ (0.038 g/cm³) with the foldable vane on the high-sensitivity setting.
- Standard N and reinforced R vanes: 8.74 lb/ft³ (0.14 g/cm³)
- Foldable V vane: 2.37 lb/ft³ (0.038 g/cm³)
- Cruciform X vane: 2.50 lb/ft³ (0.04 g/cm³)
- Aggregate A vane: 28.10 lb/ft³ (0.45 g/cm³)
Vane types and process connections
Five vane types are available: standard N, foldable V, cruciform X, reinforced R, and aggregate A. Standard process connections include 1", 1¼", and 1½" NPT threads, G1 and G1½ threads, and 110 mm and 200 mm flanges. Vanes and other wetted parts are stainless steel.
Temperature, pressure, and materials of construction
The standard NIR-9 handles media temperatures from -4 to 194°F (-20 to 90°C), and the high-temperature NIR-92 version extends this to -4 to 392°F (-20 to 200°C). Operating pressure ranges from -7.25 to 7.25 PSIG (-0.5 to 0.5 bar), and ambient temperature is rated -4 to 140°F (-20 to 60°C).
The housing is polyester-coated aluminum with a threaded cover that rotates 360 degrees. The maximum grain size is 1.96 inches (50 mm), and the enclosure carries IP66 protection.
Electrical connection and switching output
The NIR-9 accepts 24 VDC or 110 VAC supply at 50/60 Hz, with additional voltages available by order code and maximum power consumption of 2 VA. The output is an SPDT micro-switch rated up to 250 VAC, 2 A (125 VA maximum). Two 1/2" NPT conduit entries are provided, and the contact is wired to the C, NO, and NC terminals.
Installation and mounting
Mount the NIR-9 in the tank top for high-level detection, or through the tank wall for high, middle, or empty level. For side installation without a mechanical extension, use the NIR-96. Position the unit out of falling material, and add angled protection where heavy or falling loads occur.
Point the cable gland downward to avoid water intrusion, and keep the vane clear of areas where material build-up can occur. The reinforced NIR-93 is available for empty or middle level in large vessels and for bulk densities above 62.4 lb/ft³ (1 g/cm³).
Hazardous-area (ATEX) version
ATEX-approved NIR-E9 versions are available for hazardous dust atmospheres, carrying the marking II 2/1D Ex t IIIC T85°C Db/Da for Zone 20, 21, and 22 applications. The hazardous-area version is selected through the NIR-E9 order codes and retains the polyester-coated aluminum housing with IP66 protection.
Designed for motor protection and service life
Because a second micro-switch switches the motor off once the vane is blocked, the drive is not held under continuous load. This operating design is intended to help protect the motor and support a longer service life.
Other bulk-media level monitoring options
For other bulk-media level monitoring needs, KOBOLD also offers the NMF membrane level switch, the NVI vibrating rod level switch, and the PLS pendulum level switch.
Common Questions about NIR-9 - Rotating Vane Level Switch for Bulk Media
It is a motor-driven paddle switch for solids. The vane turns continuously until material impedes it; the resulting movement trips a micro-switch for the alarm output, while a second micro-switch stops the motor until the material clears and the vane is free to turn again.
Detection depends on the vane and sensitivity setting. On the high setting, the V vane reaches 2.37 lb/ft³ (0.038 g/cm³), the X vane 2.50 lb/ft³, the N and R vanes 8.74 lb/ft³, and the A vane 28.10 lb/ft³. Lighter materials call for a more sensitive vane.
The standard unit runs from -4 to 194°F (-20 to 90°C); the NIR-92 high-temperature version reaches 392°F (200°C). Pressure capability spans -7.25 to 7.25 PSIG (-0.5 to 0.5 bar), and the largest grain size it accepts measures 1.96 inches (50 mm).
Available threads are 1", 1¼", and 1½" NPT along with G1 and G1½, and flange sizes of 110 mm and 200 mm. Vane choices cover foldable V, cruciform X, standard N, reinforced R, and aggregate A, each supplied in stainless steel.
Supply options include 24 VDC, 110 VAC, and 230 VAC at 50/60 Hz, drawing up to 2 VA. The switching element is an SPDT micro-switch rated to 250 VAC, 2 A (125 VA maximum), and a green LED confirms that power is applied to the unit.
The switch offers low, medium, and high sensitivity, chosen by repositioning the spring, with medium set at the factory. Raise the setting if the motor keeps running after material reaches the vane. Optional vane styles can further improve sensitivity for lighter bulk materials.
Fit it in the tank top for full-level detection, or through the wall to sense a high, middle, or empty point. Keep it clear of falling material, adding angled protection under heavy loads. Aim the cable gland downward against water intrusion, and choose the NIR-96 for side mounting.
Yes. The NIR-E9 series is approved for hazardous dust areas with the marking II 2/1D Ex t IIIC T85°C Db/Da, covering Zone 20, 21, and 22. Like the standard model, it uses a polyester-coated aluminum enclosure rated to IP66 protection.
The code reads as model, extension, vane, fitting, voltage, and option, for example NIR-910NN640: model 91 (standard 65 mm), 0 (no extension), N (standard vane), N6 (1" NPT), 4 (110 VAC), 0 (no special option). The protection-pipe extension requires an N8, G8, F1, or F2 fitting, and flexible extensions need a specified length.