KOBOLD NBK-03 Bypass Magnetic Level Indicator, up to PN 320

Bypass level indicator that shows the level without auxiliary power

The KOBOLD NBK-03 bypass level indicator family measures, displays and monitors liquid levels in storage tanks, ship tanks, agitator vessels and water tanks. A bypass tube is attached to the side of the vessel; by the law of communicating tubes the level in the tube equals the level in the vessel. A float with embedded magnets follows the liquid and moves a display outside the tube without contact, so the level stays visible as a red column even when the power fails.

The datasheet covers the models NBK-03, -06, -07, -10, -31, -32 and -33. The red and white rollers or balls turn by 180° as the float passes, and a transmitter or limit contacts can be fitted outside the tube for remote signals.

Technical specifications

Display, transmitter and switch options

The roller display is available with POM rollers (-20 to +120 °C) or ceramic rollers (-40 to +400 °C). Ball displays suit lower temperatures and give a 180° view, higher protection (IP66) and better vibration resistance in the silicone-oil filled version. A reed contact resistor chain with a loop-powered transmitter gives a 4 to 20 mA signal; the HART transmitter model H adds LED or LCD display options; a magnetostrictive sensor is fitted where ±1 mm resolution is needed.

Limit contacts are clamped onto the tube. The reed types NBK-RV200 (normally open or closed) and the NAMUR types NBK-RN200 are for -104 to +200 °C medium temperature, while NBK-RH reaches +350 °C. A universal ADI indicating unit can be mounted on the bypass to show the 4 to 20 mA signal.

Selection and ordering

Select the model from the pressure rating and the medium temperature first: the NBK-03, -06 and -07 cover standard pressures with flat or PTFE gaskets, the NBK-10 uses a reinforced graphite gasket, and the NBK-31, -32 and -33 use RTJ seals for high-pressure service with a wider tube. The float is made for a specific medium density, so the density at operating temperature must be given with the order.

Confirm before ordering: tank connection spacing and the centre-to-centre length, density and viscosity of the medium, flange standard and rating, the display material for the temperature range, and any ATEX requirement, which is described on a separate KOBOLD sheet.

Documents and quotation

The KOBOLD NBK-03/-06/-07/-10/-31/-32/-33 datasheet (edition 2/04-2025) is attached to this page. Browse our Level Instrumentation category for related instruments, or compare with the ABB KM26 magnetic level gauge.

For a quotation, send the centre-to-centre length or measuring length, connection size and standard, pressure rating, medium and its density, temperature, and the display, transmitter and limit contact options.