Mobrey PLS Series Rotating Paddle Level Switch for Solids

Rotating paddle level switch for powders, granules and bulk solids

The Mobrey PLS is a rotating paddle level switch for solids, used as a high or low level limit switch in silos and hoppers. It can be mounted from above or through the vessel wall. A small electric motor turns a paddle that rotates freely while there is no material at the paddle. When material stops the paddle, a microswitch actuates an alarm signal and power to the motor is cut, which the datasheet notes extends motor life. When the level falls, the motor returns to its normal position and the paddle rotates again.

The series is intended for granular, pelletized and powdered dry products. The datasheet gives minimum densities of over 160 kg/m3 for high level applications and over 80 kg/m3 for low or intermediate applications, and states that the switch is not intended for liquids.

Technical specifications

Ordering code and options

The model code is PLS followed by five characters. Table 2 selects the type: K standard with two SPDT alarm relays, H high temperature standard, P Safepoint failsafe with a fault relay and one SPDT alarm relay, and T high temperature Safepoint. Table 3 selects the mounting thread, B1 for 1 1/2 inch BSPT (not high temperature) or N1 for 1 1/4 inch NPT, and Table 4 the aluminium alloy housing (3). The voltage code is 0 for 115 Vac, 1 for 240 Vac and 2 for 24 Vdc, and the approval code is A for ATEX dust certification II 1/2 D or Z for no hazardous area approval.

Failsafe Safepoint models use a microcontroller for self-validating diagnostics and monitor motor and shaft rotation, indicating a fault condition on the fault relay.

Installation accessories

Top mount installations often need the paddle to extend to a set level. Solid stainless steel shaft extensions are available from 76 mm up to 1800 mm, and multiple sections can reach 3600 mm. A flexible coupling, about 64 mm long, absorbs heavy loads, side loads and product surges and should always be used with a solid shaft extension, together with a stainless steel shaft guard of the same length. Half couplings (P0112) suit side mounting and full couplings (P0113) suit top mounting; the full coupling is standard on the high temperature option. A mounting plate, for NPT thread switches only, allows mounting to a curved or flat surface. Paddle selection depends on material weight, with separate order parts for heavy, medium and light materials.

How the Mobrey PLS works

A small electric motor turns a paddle inside the vessel. While there is no material at the paddle it rotates freely. When material covers the paddle and stops it, a microswitch actuates the alarm signal and power to the motor is cut. When the level falls, the paddle turns again.

Where the PLS is used

• Silos
• Hoppers
• Powder storage bins
• Granule and pellet handling
• High and low level limit detection

Selection checklist for the PLS

• Material density
• High or low level duty
• Process temperature
• Ambient temperature
• Process thread
• Conduit thread
• Power supply
• Standard or failsafe model

Installation, commissioning and maintenance notes for the PLS

Mount the switch from above or through the vessel wall at the level to be detected. Keep the paddle clear of the fill stream where material could fall on it. Wire the supply and the alarm relays and test the alarm by blocking the paddle. Inspect the paddle shaft and the housing at regular intervals.

Requesting a quotation for the Mobrey PLS

Please send the material, its bulk density, the temperature, the mounting position and the supply voltage. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.

PLS switch type

It is a rotating paddle level switch for solids.

PLS duty

It is used as a high or low level limit switch.

PLS mounting

It can be mounted from above or through the vessel wall.

PLS motor protection

Cutting power to the motor when the paddle stops extends motor life.

PLS suitable products

The series is intended for granular, pelletized and powdered dry products.

PLS liquids

The switch is not intended for liquids.

PLS high level density

For high level duty the material density must be above 160 kg/m3.

PLS low level density

For low or intermediate duty the material density must be above 80 kg/m3.

PLS process connection

The process connection is 1 1/2 inch BSPT or 1 1/4 inch NPT.

PLS conduit connection

The conduit connection is 2 x M20 on the BSPT model or 2 x 3/4 inch on the NPT model.

PLS standard output

The standard model has two SPDT relays rated 15 A at 250 Vac.

PLS Safepoint output

The Safepoint model has one signal relay and one fault relay.

PLS process temperature

The standard model runs from minus 40 to 149 degrees C.

PLS high temperature model

The high temperature model runs up to 399 degrees C.

PLS ambient temperature

The standard ambient range is minus 40 to 93 degrees C.

PLS operating pressure

The maximum operating pressure is 2 bar.

PLS power supply

The supply is 115 Vac, 230 Vac or 24 Vdc.

PLS housing

The housing is powder paint coated aluminium alloy.

PLS wetted parts

The wetted parts are 304 stainless steel.

PLS weight

The standard model weighs approximately 4 kg.

PLS model code

The model code is PLS followed by five characters.

PLS type selection

A table in the datasheet selects the type, such as standard, high temperature or Safepoint failsafe.

PLS mounting thread selection

The mounting thread is chosen as B1 for 1 1/2 inch BSPT or N1 for NPT.

Level switch records for the PLS

Record the vessel, the mounting height, the model code and the date of each alarm test.

Choosing the right PLS model

Choose the model from the material density, the process temperature and whether a fault relay is needed.

Documents and quotation

Confirm the stored material and its bulk density, whether the switch is for high or low level, the vessel wall or roof arrangement, insertion length, supply voltage, process temperature and dust-zone classification. Hazardous-area use applies only to code A versions.

The manufacturer document is attached to this page and listed below. Seven Star LLC is an independent supplier in Muscat and can quote against the model code, quantity and delivery location. Browse more instruments in Level Instrumentation, or see the Mobrey brand page.