Wet, Siphon, or Pressure, Which Abrasive Delivery is Best?

When you see a media blasting cabinet, i.e. sandblasting cabinet, with enclosed containment and recycling abrasive, you will find different types of abrasive deliveries to the blast gun. We are going to talk about your specific application of blasting cabinets as well as a suitable abrasive delivery system. We are going to talk about your specific application of blasting cabinets as well as a suitable abrasive delivery system. This post will help to uncover which abrasive delivery – wet or siphon or direct pressure – is best for your application.

Before making a choice or selection, it’s important to know…

What is Abrasive Delivery?

Abrasive delivery refers to the process of delivering abrasive materials to a workpiece for the purpose of cutting, grinding, polishing, or other surface preparation operations. Abrasive materials can include substances such as sand, gravel, diamond particles, or other particles or granules. These materials are used to remove material from a surface.

There are three types of abrasive deliveries for cabinets. Abrasive delivery is how the abrasive gets to the blast nozzle and exits into the cabinet.

1. Wet abrasive blasting cabinets
2. Dry siphon abrasive blasting cabinets
3. Dry pressure abrasive blasting cabinets

Wet Abrasive Delivery

Wet cabinets use an injector suction gun to deliver the slurry consisting of water and suspended abrasive to the part surface. Using a variety of methods and processes, abrasive suspensions can be made but wet abrasive processing capabilities in the high range of 23% percent can help reduce cleaning speed in slow-processed wet cabinets.

The injector gun is equipped with two hoses that are attached to it, one for compressed air supply and one for abrasive delivery to the blast gun. Slurry supplied to the blast gun is accelerated by compressed air inside the gun exiting the nozzle at higher velocity to clean or texture the part surface.

Normally, you know you need a wet cabinet, because you have a specific application. If you’re not sure this applies to you, here’s a few quick reasons you’d want to use wet blasting:

• Elimination of frictional heat that might damage or burn parts
• No abrasive impregnation into the part surface or a chemically clean surface for critical coatings

Wet Blasting or Dry Blasting as Applied

Wet blasting is much slower than dry blasting because no frictional heat is present. In addition wet blasting cabinets normally use finer abrasives, which clean much slower than larger abrasives. Media Blast offers wet blasting models with abrasive sizes up to 80 mesh at high slurry percentage.

As for the advantages, analyzing the above reasons and way, you will understand why companies that refurbish painted automotive wheels use wet blasting cabinets to etch and clean the original coating using finer abrasive for a smoother coated finish while making sure a clean bonding surface is created. 

With this chemically clean surface you eliminate “fish-eye” when the wheel is coated again. Wet blasting is a good choice for remanufactured wheels but so are other applications. For example, critical gold plating, medical implants and other parts damaged by frictional heat should not be dry blasted.

Real World Example: Years ago phone cases were blasted wet to remove all the dirt and pen marks in the cases. After cleaning the cases were heated again and allowed to re-skin creating an almost new case appearance.

Dry Siphon Abrasive Delivery

Pressure cabinets are more expensive, more difficult to operate, and clean more slowly than siphon. This is when compressed air usage, abrasive velocity and abrasive pounds per minute delivery are equal. Dry pressure cabinets can operate with the same abrasives used inside siphon cabinets, but they also use other materials, such as steel shot, and allow through-hole blasting.

Myths about pressure abrasive delivery machines:

• Pressure delivery machines offer the fastest cleaning times
• Pressure delivery is better than siphon delivery

Most pressure machines use a pressure pot to pneumatically accelerate the abrasive that easily exceeds the maximum abrasive impact velocity of any abrasive type being used. This more than likely creates a higher abrasive use rate for pressure due to operator error about maximum abrasive impact velocity. Pressure cabinets generate more frictional heat than siphon, allowing some cleaning applications to require pressure models. If you want to shot peen to the highest peening intensity you must use pressure.

Pro Tip: Pressure cabinets do some things siphon cabinets cannot – through-hole cleaning, operating using certain large or heavy abrasives, etc.

To Sum It Up

Depending on your application, you’ll want a wet, siphon, or pressure abrasive delivery system. What helps decide is what is being blasted and why. When you are informed, it will help in your decision of what is being blasted and why.

Many ill-informed buyers believe that pressure is faster and this might be true with heavy coatings, but remember pressure is also more expensive with sometimes experiencing the inconsistent flow of abrasive material. Working with a knowledgeable manufacturer can help you spend smart and buy the right machine for your needs the first time! Contact us for help selecting the right machine for you!

Pro Tip: The CFM used by a gun or nozzle decides cleaning speed more than the abrasive and blasting pressure… Definitely not the abrasive delivery system.