Diaphragm Switch

Manufactured by BinMaster & Distributed by Wm. Neundorfer & Co.

The simple, low-cost, proven point level switch for high-, low-, and plugged-chute detection in bins, silos, and chutes—free-flowing dry bulk solids.

BinMaster’s authorized Diaphragm Switch distributor for the Great Lakes region —
65 years specifying the right model, diaphragm material, and mount for your material, environment, and mounting location.

Get an application-specific recommendation

Tell us about your vessel. Wm. Neundorfer & Co. will spec the right diaphragm switch—model, diaphragm material, and mount—for your material, environment, and process.

or call (440) 350-7460

Trusted across the Great Lakes region since 1959

Local Inventory
stocked in Painesville, OH

65 Years of
Bulk Material Handling Expertise

Serving the Great Lakes Region
OH, PA, WV, NY

Key Specs

Technology

Diaphragm Switch

Electromechanical micro-switch

Installation

Internal and External

Varies based on specific model

Diaphragm Material

3 Materials

3 options to meet the needs of your application.

Why the diaphragm switch is the most economical point-level alarm in Great Lakes grain, feed, cement, and bulk facilities

The lowest-cost reliable level alarm you can install

A diaphragm switch has nothing to calibrate and no signal to aim. Material presses a flexible diaphragm against a sensitive micro-switch, and the switch trips. Wire it to a light, horn, alarm, motor starter, or BinMaster point-level alarm panel — it’s the simplest, lowest-cost way to put a dependable high- or low-level alert on a bin.

Almost nothing protrudes into the vessel (External Install)

There’s no paddle to turn and no probe to insert — just a sealed diaphragm at the bin wall or roof and a micro-switch behind it. No rotating parts, no shaft to bend, and nothing in the flow path to wear or snag. The molded-nylon or die-cast aluminum housing shrugs off dust, moisture, and vibration.

One product family, ordinary location to explosion-proof

The BM-25 covers economical alerts in ordinary (non-hazardous) locations; the BM-45 adds a die-cast aluminum housing with more mounting and voltage options; and the BM-65 carries UL Class II, Groups E, F & G approvals for combustible-dust environments. Match the diaphragm — neoprene, neoprene with nylon mesh, or silicone — to the material’s density and temperature.

Catches plugged chutes before they make a mess

Heavy-spring plugged-chute models (BM-65-FHPC and BM-65-RHPC) alert when a chute or conveyor backs up with material, so you stop the line before the spill, not after — with explosion-proof certification for dusty transfer points.

BinMaster Diaphragm Switch Installed

Models

Three families built on the same proven pressure-switch principle. They differ in housing, the density and temperature range they cover, and whether the location is hazardous.

Model Highlight Applications
BM-25 Economical molded-nylon housing with a silicone diaphragm. Internal or external mount. Ordinary (non-hazardous) locations. Budget high/low alerts on grain, feed, seed, and fertilizer bins
BM-45 Die-cast aluminum housing, neoprene or silicone diaphragm, multiple mounting and voltage options. Non-hazardous. Heavier-duty service and a wider density and temperature range than the BM-25
BM-65 Explosion-proof, UL Class II, Groups E, F & G. Die-cast aluminum, full diaphragm choice, internal or external mount. Combustible-dust and classified areas — grain dust, coal, flour, sugar, plastic powders
BM-65-FHPC External mount heavy spring and rugged diaphragm material to detect material buildup in transfer chutes. When material blocks the chute, the diaphragm activates an alarm connected to a horn, siren, light, or control panel. Alerting on clogged chutes and conveyors before a spill
BM-65-RHPC Internal mount heavy spring and rugged diaphragm material to detect material buildup in transfer chutes. When material blocks the chute, the diaphragm activates an alarm connected to a horn, siren, light, or control panel. Alerting on clogged chutes and conveyors before a spill

Still narrowing it down?

Tell us about your vessel and material—we'll spec the right model for your application.

Configure your diaphragm switch to your application

Diaphragm switches are used across a wide range of materials, vessels, and mounting locations. To keep detection reliable wherever it’s deployed, the diaphragm material and the mounting style are matched to your material’s density, temperature, and the location’s hazard classification. Not sure which configuration fits?  Tell us about your application, and we'll spec the right configuration for you.

Type Best at
Neoprene Abrasion- and chemical-resistant, waterproof, and durable. The default for most ambient dry bulk solids up to 220°F.
Neoprene with nylon mesh Added strength for heavier, denser materials — up to 90 lb/ft³ and up to 270°F. Outstanding resistance to most chemicals, heat, and oils.
Silicone High-temperature service up to 350°F. Chemical, electrical, and mechanical properties stay stable across temperature extremes.

Diaphragm switches mount through the bin wall or roof and are offered for either internal or external mounting. The right choice usually comes down to access and whether you can take the vessel out of service to install.

  • Internal mount — no hole is cut in the bin wall. The switch installs from inside the vessel, so it is best fitted when the bin is empty.
  • External mount — requires cutting a hole in the bin wall. The switch installs, and is later serviced or replaced, from outside without entering the vessel.
  • Housings by family — molded nylon (BM-25) or die-cast aluminum (BM-45, BM-65); BM-65 adds UL Class II, Groups E, F & G certification for combustible-dust areas.

Not sure which mount fits your vessel?

Tell us about your vessel type, roof angle, and existing fitting size—we'll spec the hardware for your application.

Industries where the diaphragm switch is the low-cost point-level standard

Serving industrial facilities across Ohio, Pennsylvania, West Virginia, and Western New York since 1959. Find your application below — or tell us about your vessel and we'll spec the right model.

Grain and Feed

Corn, soybean meal, wheat, barley, milo, DDGs, and ground feed in elevators, feed mills, and ethanol plants. The economical high/low alert on storage and surge bins.

Common fit:
BM-25 or BM-45 + silicone or neoprene diaphragm

Cement and Aggregate

Cement, fly ash, lime, and aggregate in batch plants and storage silos. Silicone handles hot fly ash; combustible cement dust calls for the explosion-proof BM-65.

Common fit:
BM-65-RHT (hot ash, hazloc) or BM-45-FHT

Plastics and Resins

Virgin and regrind resin pellets, masterbatch, and ground polymer in day tanks, hoppers, and railcar silos. Plastic powders in classified areas use the BM-65.

Common fit:
BM-25 or BM-45; BM-65 where dust is classified

Power Generation

Coal, fly ash, limestone for FGD, and bottom ash. Combustible coal and ash dust call for the explosion-proof BM-65; silicone handles hot ash.

Common fit:
BM-65-RHT or BM-65-FH + silicone diaphragm

Mining and Minerals

Aggregate, salt, lime, fertilizer, frac sand, potash, bentonite, and alumina. Dense, abrasive solids use the nylon-mesh diaphragm for higher bulk density.

Common fit:
BM-45-RH or BM-65-RH (up to 90 lb/ft³)

Bioenergy and Wood

Wood pellets, chips, bark, and sawdust at pellet plants and biomass-fueled facilities. Combustible wood dust in classified areas uses the BM-65.

Common fit:
BM-25 / BM-45 for pellets; BM-65 in dust-classified areas

Food

Rice, oats, sugar beets, flour, and sugar in dry storage. Combustible flour and sugar dust call for the explosion-proof BM-65; silicone suits warmer product.

Common fit:
BM-45 or BM-65 + silicone diaphragm

Don't see your exact industry?

Tell us about your vessel and material—we'll spec the hardware for your application.

FAQ

Use a diaphragm switch when you want the simplest, lowest-cost point-level alert for free-flowing dry bulk solids — grain, feed, seed, fertilizer, pellets, cement, and the like — with almost nothing protruding into the vessel. Use a rotary when you need a more positive paddle-driven indication across a very broad range of densities, or want at-a-glance status. Use a capacitance probe for sticky, fine, or interface applications a diaphragm can’t reliably catch. We sell all three — send us the application and we’ll give you the honest answer, not the expensive one.

Yes — the BM-65 carries UL Class II, Groups E, F & G approvals for combustible-dust environments such as grain dust, coal dust, flour, sugar, and plastic powders. The BM-25 and BM-45 are rated for ordinary (non-hazardous) locations. Confirm your specific dust classification and we’ll select the correct unit for your application.

The BM-25 is the economical model — a molded-nylon housing with a silicone diaphragm for ordinary locations. The BM-45 steps up to a die-cast aluminum housing with a choice of neoprene or silicone diaphragms and multiple mounting and voltage options, covering a wider density and temperature range. The BM-65 adds UL Class II, Groups E, F & G explosion-proof certification for hazardous, combustible-dust areas, including dedicated plugged-chute models.

External mounts require cutting a hole in the bin wall but install and service entirely from outside the vessel — the usual choice for bins that stay in service. Internal mounts don’t require cutting the wall, but installation is done inside the bin, best when it’s empty. Both are offered across the BM-25, BM-45, and BM-65 families; tell us your access and we’ll spec it.

It comes down to material density and temperature. Neoprene is the durable default for most ambient solids up to 220°F; neoprene with nylon mesh adds strength for denser materials up to 90 lb/ft³ and up to 275°F; and silicone handles high-temperature service up to 350°F. Tell us your material, bulk density, and process temperature, and we’ll match the diaphragm.

Yes. The BM-65-FHPC and BM-65-RHPC plugged-chute detectors use a heavy spring and rugged diaphragm to alert when a chute or conveyor backs up with material, so you can stop the line before it overflows. They carry the same UL Class II, Groups E, F & G certification for dusty transfer points.

Yes. A diaphragm switch provides a dry micro-switch contact that wires directly into a light, horn, alarm, motor starter, BinMaster point-level alarm panel, or a PLC input. It’s a point-level (on/off) device rather than a 4–20 mA continuous output — if you need continuous level or inventory across many bins, ask us about SmartBob or radar instead.

Yes. William Neundorfer & Co. performs site visits across Ohio, Pennsylvania, West Virginia, and Western New York. We’ll look at the vessel, the mounting location, the material, and the wiring path, and you’ll have a written recommendation in your inbox within a few days.

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