Abrasive Metering Valves

Maintaining a steady flow. Gain an understanding of the different types of metering valves available and which ones lead to high performance.

All blasting systems require the installation of a metering valve to introduce the abrasive media into the compressed air flow that leads to the blasting nozzle. Without a consistent supply of abrasive to the air supply the blasting operator will experience lower than expected productivity and produce an inconsistent blasting pattern.

Some contractors still believe that pushing as much abrasive as possible through the nozzle maximizes productivity. In reality, blasting with too much abrasive can actually lower productivity due to the amount of abrasive in the airflow decreasing the exit velocity of the particles at the nozzle. This loss of particle speed drastically reduces and decreases the cleaning capacity the abrasive has, when it reaches the blast surface. Production rates will then decrease and abrasive is will be wasted. To avoid this problem, abrasive is metered into the airflow in a steady controlled supply that promotes efficient blasting performance.

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Most Common Metering valves

The secret to saving thousands of dollars of abrasive, is to have a metering valve that allows you to use as little abrasive as possible

Schmidt Thompson II Valve™

The Thompson Valve is globaly recognsied to be a superior abrasive metering valve to anything else available on the market. Giving accurate abrasive metering while giving the blasting operator an instant start/stop response.

The Thompson II Valve is a fail-safe valve, giving optimum operator safety. On shut off, it cuts the abrasive flow to the nozzle and seals the tank at the same instant. Building on the original, market leading Thompson Valve the Thompson II Valve™ offers an even higher level of performance, enhanced serviceability and longer life.

This is the metering valve of choice for abrasive blasting specialists. The Thompson Valve is adjusted via the knob ontop of the valve. The Typical setting for blasting with Garnet is 4 turns of the knob.

Schmidt MicroValve III™

This ingeniously simple abrasive metering valve can meter your abrasive flow much more accurately than any conventional valve. In fact when retrofitted onto an old Blast Machine, operators tell us that the pot lasts twice as long, before running out! The MicroValve, like the Thompson Valve is adjusted via a small knob ontop of the valve.

The MicroValve is used in a pressure release blasting system, which exhausts all the air when the operator releases the control deadman handle. This valve is typically used in conjunction with a Schmidt ComboValve

Flat Sand Valve

The Flat sand valve has been on the market for many years. They are operated via a lever, which meters the abrasive by adjusting the size opening. 

Donut Metering Valve

The Donut metering valve is adjusted by screwing down the two nuts on either side of the rubber donut, this action restricts the opening that the abrasive passes through. 

Getting the right setting for optimal performance.

Look at the abrasive flow coming out of your nozzle. An efficient air/ abrasive mixture will be only slightly visible, appearing as a colored haze in the air stream. If you see a lot of color in this flow, there’s too much abrasive (and not enough air) in the mixture. Why? Your abrasive metering valve is open too far. When this happens, your cleaning efficiency is lowered, valuable abrasive is wasted and you’re losing money. Create the best mixture by starting off with no abrasive and slowly open up the metering valve, until you can only just start to see the color change in the air exiting the nozzle. That’s all the abrasive you need for fast and effective blasting.

To take out some of the time, guesswork, and waste out of metering abrasive to optimize its flow rate, includes a new virtual position indicator (VPI). The VPI is an external indicator that accurately displays the position of the plunger relative to the abrasive orifice inside the valve. Additionally, graduations show the number of turns the metering knob has been adjusted. This gives the operator more precision and consistency when adjusting the abrasive flow for different application conditions, nozzle sizes, blast pressures, and abrasive size and types.

John Smith, San Diego, USA