Weha TEC740 Mobile Dust Collector: Suction-Arm Capture Guide

Dust is the one shop hazard that does its damage without ever announcing itself. A dropped slab makes noise and generates an incident report. Respirable dust from a grinder produces nothing at all in the moment, which is exactly why it gets tolerated for years. The particles that matter most are too small to see under shop lighting, and they stay airborne long enough to travel past the operator who created them and into everyone else's breathing zone.

Wet methods solve a large part of the problem, but no stone shop runs entirely wet. There is always dry edge work, dry polishing, a repair cut, a touch-up on an installed piece, or a process where water would ruin the workpiece. That is the gap a mobile suction-arm collector fills. This guide covers why source capture beats room ventilation, how the Weha TEC740 is configured, where to place the arm, and what filter and bag discipline looks like.

Why Capture at the Source Beats Room Ventilation

The regulatory backdrop is straightforward. Under the OSHA respirable crystalline silica standard, the permissible exposure limit is 50 micrograms per cubic meter of air as an eight-hour time-weighted average, and the action level that triggers additional obligations is 25 micrograms per cubic meter on the same eight-hour basis. Those are small numbers, and they are averages across a shift, so short bursts of heavy dust generation carry real weight in the final calculation.

General room ventilation works by dilution. It moves large volumes of air through the building and gradually lowers the average concentration everywhere, which sounds effective until you consider the geometry. Dust is generated at a point, and the operator stands directly beside that point. By the time a diluting airstream has mixed the contaminant through the room, it has already passed through the breathing zone of the person who created it.

Source capture inverts that relationship. A hood placed close to the point of generation catches dust while it is still concentrated and moving in a predictable direction, before it disperses into the room at all. The physics rewards proximity heavily: capture velocity falls off rapidly with distance from the hood face, so a hood a few inches from the work does dramatically more than the same hood two feet away. Positioning is the whole mechanism.

Source capture complements wet methods rather than competing with them. Water suppression is the primary control wherever it can be used, and nothing here changes that. But wet cutting produces slurry that dries into settled dust, and there are always operations where water is impractical: dry polishing, seam repair, touch-up grinding on installed work, and cutting where the substrate cannot get wet. A dry collector covers the part of the shift wet controls cannot reach.

Mobility is what separates a suction-arm cart from fixed extraction. Fixed ductwork is efficient and quiet, and it is also expensive to install and painful to modify when the layout changes. A mobile unit goes where the work is this week, serves a station that only runs occasionally, covers a machine while the fixed system is down, and moves to the installation bay. For smaller shops it is often the whole dry collection program.

The Weha TEC740 is built around that role. It runs a 2 HP motor on 220 volt three-phase power at 20 amps, moves 63,566 cf/h of air, which is 1,800 cubic meters per hour, and draws through a 10 in diameter suction mouth on an articulated arm reaching up to 102 in, or 8 ft 6 in. Filtration is a cartridge measuring 18 in in diameter by 39 in long that captures 99.9% of dust, and collected material drops into a disposable trash-bag system.

Positioning the Arm for the Work in Front of You

Buying a collector is easy, and positioning it correctly is where the exposure reduction actually happens. The general rule is the same for every operation: get the suction mouth as close to the generation point as the work allows, put it on the side the dust is already traveling toward, and keep the operator out of the path between source and hood. Reposition the arm every time the work moves. A parked arm is doing very little.

Grinding and Edge Work

Grinding throws dust in a defined direction set by wheel rotation and the angle of attack, which makes it the easiest operation to capture well. Watch where the plume goes on the first pass, then place the 10 in mouth just downstream of it and slightly below the work, since the coarser fraction drops while the fines carry. Keep the hood face parallel to the plume rather than pointed at the wheel and you capture the stream instead of fighting it.

Edge profiling adds the complication of a moving contact point traveling the length of the slab. The realistic approach is to reposition the arm in sections rather than covering the whole edge from one location. With reach of up to 102 in, the arm serves a substantial working zone from a single cart position, so most edges break into two or three setups. Building that into the operator routine matters more than any equipment adjustment.

Hand grinding on installed work is the hardest case, because the collector has to come to a finished space. The cart rolls on four swivel wheels with locking brakes on two of them, so it parks stably on a job site as well as a shop floor, and at 176 lb it is a two-person move up any step. Set the brakes, position the arm, and confirm the mouth stays put through the full stroke of the tool.

Dry Polishing and Finishing

Dry polishing generates finer particulate than grinding and much less visible plume, which makes it deceptively easy to underestimate. The fines are the fraction that stays airborne longest and penetrates deepest, so the operation deserves capture even though it looks cleaner than rough grinding. Place the mouth close and low, and resist pulling the arm back because the dust is not obvious. What you cannot see is what the exposure standard is written about.

Polishing sequences move through progressively finer steps, and the operator handles the piece repeatedly between them. Each handling event re-suspends settled dust from the slab and the bench. Leaving the collector running through the whole sequence, including the handling between grits, captures far more than switching it on only while the tool is spinning. The energy cost of that is trivial next to the exposure reduction it delivers.

Bench layout supports or defeats the whole effort. Position the cart so the arm reaches the work without crossing the operator's body or fouling the tool cord, and keep the path clear so the unit can move without unplugging half the bench. The control panel carries three 110 volt outlets, which lets the polisher and a work light run from the collector itself and keeps cords off the walking route.

Dry Cutting and Repair Cuts

Dry cutting is the highest-generation dry operation in most shops, and it is usually done because water is not an option: a repair cut on an installed top, a cut where the substrate cannot get wet, or a quick trim where setting up wet is impractical. That justification does not lower the dust output. If anything it raises the priority of hood placement, because airborne concentration during a dry cut is as high as anything the shop produces.

Blade rotation throws material along a predictable line, so place the mouth to intercept that line rather than aiming it at the blade itself. Where the tool has its own shroud and port, use both: the shroud captures what it can at the blade, and the arm picks up what escapes and what re-suspends from the cut line. On a plunge or stop-start cut, escape happens at entry and exit, so bias the hood toward the working end.

Housekeeping around dry cutting is part of the control, not a separate task. Settled dust returns to the air with every sweep, every compressed air line, and every piece of stock moved across the bench. Never use compressed air to clean a bench or clothing. Use the arm itself to clear the immediate work area at the end of a cut, then wet-wipe or vacuum the station. The collector earns its keep between cuts as much as during them.

Manufacturer specifications for the Weha TEC740 mobile suction-arm dry dust collector.

Fitting the Unit into Shop Power, Layout and Workflow

Power comes first, because it is the constraint that cannot be worked around on delivery day. The unit runs on 220 volt three-phase power at 20 amps, so confirm three-phase availability, the location of suitable receptacles, and how the cart will move between them before the equipment arrives. Shops that plan several properly placed drops end up with a collector that gets repositioned freely. Shops that plan one drop end up with a mobile unit that never moves.

Footprint and height drive where the cart can live. At 28 in long by 40 in wide by 88.5 in high, it needs a real parking spot and clearance under any low structure, ductwork run, or mezzanine on its travel path. Walk the intended route before purchase, including doorways and the transition between shop and yard. At 176 lb on four swivel wheels it rolls easily on smooth floors and becomes a two-person job across thresholds.

The three 110 volt outlets on the control panel are more useful than they first appear. Running the grinder or polisher from the collector means the tool and the extraction travel together, so an operator cannot end up with the tool plugged in and the collector three benches away. It also reduces cords crossing the floor around a station, which matters where people carry stone on foot and a snagged cord is a genuine hazard.

Think about where the exhaust air goes as well as where the dust comes from. Discharged air creates local currents, and a discharge aimed at a nearby bench lifts settled dust straight back into the room. Keep the unit clear of open doors, fans, and makeup air paths that would pull capture away from the hood. Cross-drafts are the most common reason a correctly sized collector underperforms, and they are usually free to fix.

Coordinate the mobile unit with whatever fixed and wet controls the shop already has rather than treating it as a parallel system. Map the operations that generate dry dust, note which are already covered by a shrouded tool or fixed extraction, and assign the mobile collector to the gaps. That map is also the starting point for an exposure assessment, and it shortens the conversation with an industrial hygienist considerably.

Filter Care, Bag Changeout and Program Discipline

A cartridge filter measuring 18 in in diameter by 39 in long carries substantial media area, and capture efficiency of 99.9% of dust depends on that media staying in usable condition. Loading is gradual and the symptoms are subtle: airflow drops before anyone notices, and the operator compensates by moving the hood closer without knowing why. Build a scheduled check into the maintenance routine, and log it so trends across months are visible rather than anecdotal.

Clean the cartridge according to the manufacturer's instructions and nowhere near the shop floor. Never blow a loaded stone-dust cartridge out with compressed air in an occupied space, because that single act can put more respirable material into the room than a full shift of grinding. Inspect the pleats for tears, holes, and blinded areas, and replace rather than repair. A compromised cartridge quietly turns an extraction unit into a dust redistribution system.

The disposable trash-bag system is convenient, and it is also the moment of highest exposure risk in the whole cycle. A bag full of dry stone dust releases material readily when it is disturbed. Change bags with the unit off, seal the bag before removing it rather than after, avoid dropping or compressing it, and move it straight to a covered disposal container. Treat changeout as a task requiring respiratory protection, not a housekeeping errand.

Assign the task rather than leaving it to whoever notices. Dust equipment maintenance falls through the cracks precisely because the equipment keeps running while it degrades, unlike a saw that simply stops. Name an owner, set an interval, keep a log at the machine, and stock spare cartridges and bags before they are needed. A collector waiting a month for a filter gets pushed into a corner, and the work it covered goes back to being uncontrolled.

Equipment is one leg of a silica program and not the whole thing. The rest is exposure assessment, written control methods for each task, training that explains why the controls exist, respiratory protection where engineering controls alone do not get exposures low enough, and medical surveillance where the standard requires it. A shop that can show which control covers which operation, with maintenance records to match, is in a far stronger position.

Dry collection is one piece of a shop-wide dust strategy. See the full equipment range at dynamicstonetools.com, review respirators and protective gear in the safety equipment collection, and read the full specifications for the Weha TEC740 mobile dust collector before sizing your dry stations.