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Home / Abrasive Metering Valves Buying Guide

Abrasive Metering Valves

Your abrasive metering valve is among the most important components of your blasting set-up.

This valve’s importance is often dismissed and contractors unknowingly lose efficiency and profit because they are wasting pressure and abrasives – not to mention jobsite downtime and continual repairs.

The following information is designed to help you understand the importance of your metering valve and make the right buying choice for your operation.

Pressure System Best Scenarios Multiple Blasters? Min Pressure Required Benefits Disadvantages Retrofit
Schmidt Thompson Valve I SCHMIDT THOMPSON I VALVE Pressure-Hold
  • This is the old version of the Thompson Valve, we would only recommend this when you have lots of blast pots with this same valve, otherwise you are best going with the latest generation
Yes 80 psi
  • Cylinder head is prone to cross threading, hard to maintain
Schmidt Thompson Valve II SCHMIDT THOMPSON  VALVE II Pressure-Hold
  • Frequent start/stop blasting, holding the pressure in the pot will save you up to 10% of your abrasive
  • Multiple blasters off same pot
  • Projects using long lengths of hose
  • Gives you a 2 second response time
Yes 80 psi
  • Faster response time to deadman
  • Unable to automatically refill with abrasive
Retrofit Kit
Schmidt Thompson Valve 2 XL SCHMIDT THOMPSON 2 XL (Extended Life) Pressure-Hold
  • If you are using a very abrasives, or abrasive that has lots of dust.
  • If you are using a Thompson Valve right now and having premature wear issues, this valve is a good upgrade.
Yes 80 psi
  • Very low wear
  • Robotic Installations when using large amounts of grit
  • Price
Schmidt TeraValve XL SCHMIDT TERAVALVE XL Pressure-Hold
  • #1 Preferred by Blast Pot Repair Technicians
  • Built from High Tensile Stainless Steel, has very low wear
  • Frequent start/stop blasting
  • Multiple blasters off same pot
  • Projects using long lengths of hose
Yes 75 psi
  • Fewer moving part than Thompson II
    Faster response time to deadman
  • Reduces abrasive consumption
  • Abrasive flow not able to support a blasting robot that uses steel grit
  • Unable to automatically refill with abrasive
Retrofit Kit
Schmidt Thompson Valve I Schmidt Thompson Valve II Schmidt Thompson XL Schmidt TeraValve XL
SCHMIDT THOMPSON I VALVE SCHMIDT THOMPSON VALVE II SCHMIDT THOMPSON 2 XL (Extended Life) SCHMIDT TERAVALVE XL
Resulting Pressure System Pressure-Hold Pressure-Hold Pressure-Hold Pressure-Hold
Best Scenarios
  • This is the old version of the Thompson Valve, we would only recommend this when you have lots of blast pots with this same valve, otherwise you are best going with the latest generation
  • Frequent start/stop blasting, holding the pressure in the pot will save you up to 10% of your abrasive
  • Multiple blasters off same pot
  • Projects using long lengths of hose
  • Gives you a 2 second response time
  • If you are using a very abrasives, or abrasive that has lots of dust.
  • If you are using a Thompson Valve right now and having premature wear issues, this valve is a good upgrade.
  • #1 Preferred by Blast Pot Repair Technicians
  • Built from High Tensile Stainless Steel, has very low wear
  • Frequent start/stop blasting
  • Multiple blasters off same pot
  • Projects using long lengths of hose
Can Serve Multiple Blasters? Yes Yes Yes Yes
Minimum pressure required 80 psi 80 psi 80 psi 75 psi
Benefits
  • Faster response time to deadman
  • Very low wear
  • Fewer moving part than Thompson II
    Faster response time to deadman
  • Reduces abrasive consumption
Disadvantages
  • Cylinder head is prone to cross threading, hard to maintain
  • Unable to automatically refill with abrasive
  • Robotic Installations when using large amounts of grit
  • Price
  • Abrasive flow not able to support a blasting robot that uses steel grit
  • Unable to automatically refill with abrasive
Retrofit Retrofit Kit Retrofit Kit
Pressure System Best Scenarios Multiple Blasters? Min Pressure Required Benefits Disadvantages Retrofit
FLAT FSV ABRASIVE METERING VALVE FLAT FSV ABRASIVE METERING VALVE Pressure-Release
  • Older generation of metering valve design. Still occasionally found on some older blast machines or where preferred by long-term industry operators
No No Inexpensive
  • Inaccurate metering – moving the lever to increase flow increases flow exponentially
  • Valve seized up when used with steel grit
  • Replace with MicroValve III
DONUT ABRASIVE METERING VALVE DONUT ABRASIVE METERING VALVE Pressure-Release For use with coarse metallic abrasive – typically blast room or bridge blasting scenario No No Inexpensive
  • Inaccurate metering
  • Not suitable for use with fine abrasives
  • Replace with MicroValve III or Thompson Valve retrofit kit
SCHMIDT MICROVALVE SCHMIDT MICROVALVE Pressure-Release
  • This is the old version of the MicroValve 3, we would only recommend this when you have lots of blast pots with this same valve, otherwise it is best going with the latest generation
No No
  • Low Price
SCHMIDT MICROVALVE 3 SCHMIDT MICROVALVE 3 Pressure-Release
  • Great for set-ups that use an overhead feed of abrasive to automatically the blast pot.
  • Abrasive can be gravity fed into the pot whenever the pot is depressurized.
  • Typically used when you use a guillotine valve. (But guillotine valves are unsafe)
No No
  • Inexpensive basic set-up
  • Increased propensity to allow moisture into the system
  • Unable to facilitate multiple blasters using same pot
  • Multiple delays while pot repressurizes
Retrofit Kit
Flast FSV abrasive metering valve donut abrasive metering valve schmidt microvalve schmidt mircrovalve 3
FLAT FSV ABRASIVE METERING VALVE DONUT ABRASIVE METERING VALVE SCHMIDT MICROVALVE SCHMIDT MICROVALVE 3
Resulting Pressure System Pressure-Release Pressure-Release Pressure-Release Pressure-Release
Best Scenarios
  • Older generation of metering valve design. Still occasionally found on some older blast machines or where preferred by long-term industry operators
  • For use with coarse metallic abrasive – typically blast room or bridge blasting scenario
  • This is the old version of the MicroValve 3, we would only recommend this when you have lots of blast pots with this same valve, otherwise you are best going with the latest generation
  • Great for set-ups that use an overhead feed of abrasive to automatically the blast pot.
  • Abrasive can be gravity fed into the pot whenever the pot is depressurized.
  • Typically used when you use a guillotine valve. (But guillotine valves are unsafe)
Can Serve Multiple Blasters? No No No No
Minimum pressure required No No No No
Benefits
  • Inexpensive
  • Inexpensive
  • Inexpensive
  • Inexpensive basic set-up
Disadvantages
  • Inaccurate metering – moving the lever to increase flow increases flow exponentially
  • Valve seized up when used with steel grit
  • Replace with MicroValve III
  • Inaccurate metering
  • Not suitable for use with fine abrasives
  • Replace with MicroValve III or Thompson Valve retrofit kit
  • Increased propensity to allow moisture into the system
  • Unable to facilitate multiple blasters using same pot
  • Multiple delays while pot repressurizes
Retrofit Retrofit Kit

Choosing The Perfect Abrasive Metering Valve

If you’re a project manager or site foreman – here’s an important question you should find out if you don’t already know.  What generation of abrasive metering valve do you have on your blast pots?

It may surprise you that your metering valve is one of the most significant indicators of your efficiency and profit.   This is one of the most important (yet neglected) considerations on the majority of jobsites we visit.  It’s so important in fact – that if you’re a project manager looking to turn ONE DIAL to improve your team’s performance – we suggest investigating your abrasive metering valve.  It’s to your financial advantage to understand the metering valve you’re using and why it’s most likely costing you hundreds of dollars a day in inefficiencies.

First… here’s a general layout of the abrasive metering valves currently in use. These are listed from least efficient to most efficient across the broad range of blasting applications.

Efficiency of various metering valves

So, what makes one metering valve any better than another?  ONE metric.   Which valve saves you the most money? And this metric should be evaluated on the following 4 criteria:

  1. Wasted Abrasive
  2. Clean-up Costs
  3. Productivity/Downtime
  4. Needed Repairs/Replacement Parts

We’ve explained these costs in a previous Primed Insight if you’d like to learn more.  But suffice it to say, thousands of dollars can be lost each day simply by saving $200 on the purchase of a cheap metering valve. This is something every project manager should pay attention to.

A popular misunderstanding is all these valves represent different methods of metering. That is not correct. Each column is actually a generational improvement on the previous valves.

Think of the above valves through this perspective:
Perspective of valve technologies


Engineering and materials have improved with each product upgrade.

  • The metering has gotten more precise – conserving abrasive
  • Breakdowns and repairs have drastically reduced with each generation

Now, as we’re presented things, it may seem that the silver bullet to everyone’s problems is simply to buy this most current valve – The Axxiom Schmidt TeraValve.

And it probably is our top recommendation.  It not only improves efficiency across the broadest range of industrial applications, but surprisingly, it also costs less than its predecessor – The Thompson 2 Valve.

However, for high flow jobs that use multiple #10 nozzles or in blast room situations using a robot, the Thompson 2 is actually our top recommendation.

Now in case you think we’re just trying to sell you a more expensive valve – here’s an insight within an insight…

Because we’re a business like you, profit and loss is something we must also manage.  That’s why we have installed over 200 Tera Valves on our vast rental fleet. You can imagine that renting blast pots comes with quite a bit of maintenance and repair when they’re returned. We discovered that simply by installing Tera Valves on our rental pots, those maintenance costs dropped 75%.

THAT’S why we recommend TeraValves.  They’re a superior product.

And in case you’re interested – this link leads to a Tera Valve retrofit kit so you can upgrade your current pot to the latest and greatest generation of metering valves.

If you have questions as to which valve is best for your pot and applications – just reach out and ask. That’s our job!

Other Top Considerations

BEWARE: Knock-off Metering Valves

It may surprise you that this valve is one of the most significant indicators of your efficiency and profit. It affects the safety of your operators, how much abrasive you waste, and various pressure concerns.  Rule of Thumb: The cheaper your valve costs on up-front – the more it will end up costing you in downtime, repair parts, wasted abrasive, and potential harmful accidents.

We only Schmidt Axxiom valves because they are the highest quality, safest, most efficient and reliable metering valves in the industry.  Because they are of such high quality, Axxiom’s competitors are constantly producing knock-off valves trying to duplicate Axxiom’s superiority.  But don’t fall for it.  Buying knock-off valves will end up costing you much more in the end.

Your Valve Determines Your Pressure Status

Pressure Hold or Pressure Release?

Each of our standard blast machines has the option of having a pressure hold system or a pressure release.

Pressure Hold

A Pressure Hold blast pot simply means that when the blasting operator releases the deadman handle to stop blasting, abrasive and airflow cease traveling down the blast hose toward the nozzle. However, the blast pot itself remains fully pressurized and ready to send the air and abrasive once the deadman is reactivate. Retaining blast pot pressure reduces the amount of time needed to commence blasting – because the operator doesn’t need to wait for the entire pot to repressurize.

Pressure Release

A Pressure Release blast pot simply means that when the blasting operator releases the deadman handle to stop blasting, the pressure inside the pot that drives the air and abrasive is released into the surrounding atmosphere. This “depressurizes” the blast pot completely. This depressurization requires a bit more time to cut-off the flow of air and abrasive than a pot that retains pressure. Likewise, it takes a bit longer, once the operator reactivates the deadman, for the pressure to build in the pot to facilitate the flow of air and abrasive to the nozzle to resume blasting.

Pressure Hold Benefits

  • Safer and faster stop / start

  • Smoother start / stop

  • Reduces abrasive consumption and waste

  • Reduces moisture problems

  • Great for continual / high production blasting

  • Great for projects using lengthy hoses

  • Necessary to support 2 or more blasters

Pressure Release Benefits

  • Overhead Feed of Abrasive

    This is great for set-ups that utilize an automatic overhead fee of abrasive into the blast pot when it’s depressurized.

Pressure Hold Disadvantages

  • Refill Breaks

    A Pressure-Hold system requires temporary shut-down of blasting operations to refill the blast pot with abrasive

Pressure Release Disadvantages

  • Slower stop / start activation

    These delays inhibit production and compromise safety
  • Typically wastes more abrasive

  • Invites moisture into the pot

  • Unable to serve more than 1 blaster

Common Issues With Abrasive Metering Valves

  • Metering Valves are built to meter your abrasive, that being said, they are wear items, as they control the flow of your abrasive. Regular maintenance checks are paramount to ensure you don’t wear out your valve prematurely.
  • Most common cause for premature wear is when you choke the blast pot to overcome moisture issues. This forces abrasive out of the pot, which isnt the design intention of the valve. Metering Valves are designed to be like an egg timer, releasing the abrasive, flowing simply by gravity.
  • Pressure release type systems are simple and reliable but slower to respond, as each time you engage your deadman, the whole pot needs to re-pressurize before blasting can begin (5-15 seconds)
  • Pressure hold systems are faster to respond (less then 2 seconds) but more complex, making having a competent service personnel mandatory.
  • Some abrasive metering valves have a tendency to jam if being used with fine abrasive, as the abrasive gets between the plunger and the sleeve. This could be from recycled abrasive which contains material in it that is finer than as originally supplied. The selected grade may be powder-like. If you are having this issue its recommended that you try the Tera Valve, as it is designed for this application.
  • Abrasive Metering Valves can be impossible to remove for maintenance if there considerable of abrasive in the blast pot. This can be overcome a couple of ways. The simplest way is to add a union end ball valve to the blast pot and attach the metering valve to it. This allows the abrasive flow to be cut off and the valve removed. The valve will still require unscrewing with a wrench to remove. An additional component that can be added is a TriClover Quick Connector. This is in effect a clamp that allows you to quickly drop the valve. It is designed to be used by hand by may require a wrench to loosen. The downside of adding these items to your blast pot is that they add height to your valve assembly and you may not have sufficient height underneath the pot for the combined assembly.
  • Abrasive Metering Valves can be subject to wear because of differential pressure. Differential pressure is a problem caused by pressure in the hose being different to the pressure in the pot. Pressure can be higher or lower in the pot or the hose. The basic operating principle of a blast pot is that abrasive falls by gravity out of the pot and into the air stream. For this to happen the pressure needs to be the same in the pot and in the hose to allow the abrasive to gently flow into to the air stream. Once the equalization is disturbed abrasive is forced through the valve (either up or down) under pressure. This results in accelerated premature wear. This usually caused by air leaks in your blast pot or deadman system.

IMPORTANT CONSIDERATIONS FOR CHOOSING THE RIGHT ABRASIVE METERING VALVE

How continuous will your blasting be?

This has a major impact on the purchasing decision as to whether purchase a pressure hold or pressure release system. A pressure hold system is much quicker to activate and deactivate. The hold in the term pressure hold means when the deadman handle is released, pressure is held in the blast pot. The stopping of the blast is achieved by cutting the air coming into the pot (but not releasing the air that is already in there), air into the hose and abrasive into the metering valve. By holding the air already in the pot while blasting ceases, restarting the process is relatively quicker. It is quicker to shut down as well because it is not dependent on all the air being released from the pot to stop the blasting. Quicker system response is beneficial in stop/start blasting. Examples of stop/start blasting include: difficult access (working off scaffolding) and small parts requiring turning.

What metering system does your preferred valve have?

Some abrasive metering valves use a plate sliding across an orifice to meter abrasive flow. The problem with this is, that as the orifice is opened up, the volume of abrasive increases exponentially (i.e. the increase in increase increases). A system where a piston slides inside a cylinder means that the amount the abrasive increases in volume stays the same as the valve is opened up.

Primed Insights & Knowledge Articles

How To Properly Set The MicroValve

Watch Video

Issues With Abrasive Metering

Watch Video

Make Metering Valve Removal Easy!!

Watch Video

Abrasive Particle Size Testing

Watch Video

Frequently Asked Questions

  • I am blasting small components in a blast room/blasting a tank off a scaffold. Which valve system is best for my requirements?

    Either of these blasting tasks require a pressure hold system for faster stopping and starting of the blasting process. A Tera or Thompson Valve is the best valve for your application, giving you faster start/stop responses.

  • I am a powder coater who likes to blast with abrasive with considerable amount of ``fines`` in it. This is because powder coating does not flow over a profiled surface as well as a wet coating and I need a finer profile. Which valve is best for me?

    For powder coaters, who use abrasive with lots of the recycled “fines” we would recommend you use the Tera Metering Valve. This valve has the latest wear-proof technology of a wiper seal on the plunger, which allows it to be effective and give it a long life when using fine abrasive.

    No metering valve is going to stand up forever against dust. Dust is the highest wearing particle that ever comes in contact with the valve.

  • What other components might I require in addition to the metering valve when replacing the valve on my blast pot?

    You may require a pusher-line kit to connect the metering valve to the choke valve. This consists of a length of air hose and the fittings required to make the connection. This is because the new valve may have a different geometry to the old valve. This also an opportunity to replace the existing nipple that connects the valve to the blast pot (usually a standard water fitting) with a specifically designed blast pot connector. This is manufactured from an abrasion resistant steel, with the correct threads cut into it and has a tapered face on it to seat well down into the top of the valve. This connector protects both the pot and the valve. You may also a threaded quick coupling to go on the outlet of the valve to connect the blast hose to.

  • You mentioned differential pressure in ``Common Problems``. How do I prevent this happening?

    Look, listen and spray. The biggest cause of differential pressure is air leaks causing a pressure drop in the pot or the hose. An observant eye and an attentive ear will be your best tools for this. Be observant of changes in the behavior of your blast pot. A spray bottle with soapy water in it will and the soapy water sprayed onto the fittings and valves will create a stream of bubbles from the leak. Also check the hand-hole gasket and pop-valve when the pot is pressurized. If there is a pile of abrasive sitting in the dome it will “bubble” if the pop-up is leaking.

  • How easy are Abrasive Metering valves to service?

    Generally speaking pressure release systems are simpler than pressure hold systems and consequently require less maintenance and are easier to work on. Take into consideration remoteness of your blasting locations and maintenance team experience when making an Abrasive Metering Valve purchasing decision.

    There are many online videos at www.blastone.com on how to repair your metering valves, so if you know how to change the tire on your vehicle, you can easily handle repairing a metering valve (with the help of our videos)

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