KUBE Blasting System

Best practices for abrasive blasting

Surface prep is an essential part of any project. Whether you're working on a small-scale project or a large one, having clean surfaces is crucial.

Preparing your surface properly ensures that your paint stays where it belongs and that you won't waste money buying new supplies. Even statistics show you can save yourself a lot of headaches if you prep correctly.

Experts state that more than 75% of all premature coating failures happen because the surface wasn't properly prepared before applying the coating.

Fabricators can use advanced coatings systems, which may be extremely sophisticated, but if they're not properly applied, there's only a 25 per cent chance that the finish will survive long enough to perform at peak efficiency.

02

Methods of Cleaning

Depending on the type of material used for the coated product, the type of application, the overall volume of the project, and the level of quality required for the finished product, there are various ways to prepare surfaces before applying coatings.

Commercial-grade air-powered abrasives remain one of the most common methods for removing rust, mill scales, and other contaminants from surfaces. They impart a uniform finish with microscopic peaks and valleys onto the metal’s outer layer. And they are relatively quick when used by trained professionals.

03

Surfaces cleanliness vs surface profile

These two terms often get mixed up with each other. A clean surface refers to the absence of any type of contamination on the surface of the metal. The class of blasting refers to the level of cleaning achieved after blasting.

Several international standards exist that define various types of blasted surfaces.

These include joint industry standards from the Society for Protection Coating (SPC) and the National Association for Corrosion Engineers (NACE), an organization serving nearly 35,000 members in 130 countries, recognized globally as one of the premier authorities for corrosion control solutions.

Surface profile or anchoring is the condition of the surface after blasting.

When any steel surface is blasted, the abrasives dig into the surface on impact and bounce off. This impact causes a shallow depression, or valley, just a few thousandths of millimetres deep. Some of the peaks between these indentations rise slightly above the original surface level.

In the case of anchoring a metal plate to concrete, the plate must be embedded in the concrete before the concrete can be cured.

Once the concrete has hardened sufficiently, the metal plate is removed, and the remaining concrete is ground down so that only the desired amount of metal remains exposed.

A blasting treatment makes the entire rock or concrete into a rough, porous material. It creates lots of tiny holes throughout the rock or concrete, which provide a good anchor for any type of finish coating.

04

Measure PSI at the nozzle (PSI = psi x pressure)

If you're using compressed air for any reason, keep in mind that the recommended minimum operating pressure is 100 PSI. However, if you want to blast harder, you can go up to 130 PSI. And if you really want to blast hard, you can go up even further.

A profiled surface is one where there are some parts that are higher than the original surface.

If your blaster has a nozzle pressure of 90 psi, then every 1 psi lower than 100 psi means you're losing 1.5% of your efficiency. In a business environment where cost savings are always an issue, 1.5% could be the difference between making payroll and not.

To ensure you have enough air for your project, first, check your compressor gauge to see if it reads the correct psi (pounds per square inch). However, there may be several points of loss throughout your blast system.

To determine whether the water pressure is too low, you can measure the pressure behind the nozzle holder.

To get started, first use an abrasive tool to remove any debris from the valve stem hole. Then, using needle-style pressure gauges, check for leaks by applying gentle pressure to various points. Here is a short step-by-step guide you can follow:

Insert the needle into the nipple at its bottom.
Insert the hypodermic syringe slowly into the blast tube until you get a steady reading of 100 PSI or more; point the tip of the syringe toward the nozzle and slightly angle it so that it doesn't hit the side of the tank.
Record the reading, then remove the needles from the kit, and store them away for use at another time.

You can also check to make sure there aren't any leaks by testing the pressure at both ends of your long hose. You might be surprised to learn just how much pressure can drop through a leaky valve.

You should consider having two air testing kits to check the air entering your blasters and the air leaving them. Always make sure the nozzle is pointed toward the flow of air when doing so. If you're losing too much air, there could be a problem with either your accessories or compressor.

05

Don't overextend your blast nozzles use life

One of the most common misconceptions is that you're going to save money by keeping your old nozzles. The truth is that the price of a nozzle is extremely small compared to the total shop running costs, but the performance of the nozzle can affect the total project costs dramatically.

A Venturi-style nozzle functions much like an internal combustion piston. Compressed air enters one end of the tube and exits out the other end. The air is accelerated so fast that it becomes supersonic before entering the nozzle. Once inside the nozzle, the high-velocity air slows down and mixes with the abrasives. At the exit, the airflow is slowed down again and the abrasives fall back to earth.

There are two main types of liners used in blast nozzles - tungsten carbide (WC) and silica nitride (Si3N4), both of which are extremely durable, but they eventually wear out.

You can probably guess where we're going with this. But let's start at the beginning. Check the water flow rate using a water meter.

When measuring a nozzle, we consider it to be worn when it has reached one size larger than its initial size. So, for example, if you're using a 12 mm nozzle, but you've measured it at 9 mm, then you know that the nozzle is now worn out.

You can use an orifice-size analyzer gauge to measure the diameter of the nozzles. Here's how to do it:

Use soft marking utensils such as a crayon, pen, or marker to cover all sides of the taper of the gauge.
Inserting the round part of the gauge into the back of the nozzle until it stops.
Rotating the tool two to three times in one direction before rotating it back to its original position helps prevent clogging.
When removing the nozzle from the sprayer, look at the scratches on the gauge. These scratches will tell you which nozzle orifice was used.
If the diameter indicated by the test is greater than the diameter of the nozzles, discard it and replace it.

06

Selecting the right blast hose

Failure to select hoses correctly will cripple any blasting job and jeopardize a successful outcome by decreasing the nozzles' pressure, slowing down output, and increasing energy and abrasive usage.

The key takeaway: Never utilize undersized blast hoses! An undersized blast hose raises internal resistance, decreasing the airflow and abrasive mixture. In some instances, this may reduce the nozzles' velocity drastically.

One of the main reasons why people don't use bigger air blasters is that they are too expensive to buy and that they take up too much space when not in use. However, these issues are easily outweighed by the extra cost incurred by using smaller air blasters. Even for a short-term job, it would be better to spend more money than less money.

If your blast line is 45 metres long, you'll lose about 45 psi between the ends of the line. That means if you start with 120 psi in the line, you'll have 75 psi at the nozzle. Switch to a 4 cm ID line and you can maintain 110 psi at the nozzle. Using the 1 psi = 1.5% productivity" rule, that 39 psi drop represents 59% productivity.

07

Choose the right abrasive for your surface type.

A major mistake is to focus solely on the cost of the abrasive when choosing an abrasive for a particular job. You'll usually be surprised by just how small a role the abrasive plays in the overall cost of the project.

To determine which abrasives to choose for a particular job, you first must figure out the true costs per square foot of the project. A formula developed at the US Naval Academy can help:

Using two needle-style pressure gauges to check the water level in the blasting tank.

By using this equation, you can evaluate abrasives from a completely new angle. If you use it properly, it can reveal which abrasives are most effective for cleaning up concrete.

Before making your final decision about abrasives, consider these two questions. First, how fast should I blast each abrasive? And second, how much abrasive do I need to remove per hour? These two questions will help determine the type of abrasive you need to buy and the amount of abrasive you'll need to order.

When using a worn venturi in a blow gun, the resulting jet stream has a concentrated centre spot.

08

Keep Blasting cost-effective

The first step is to determine if your nozzle needs replacement. You can do this by measuring the inside diameter of the nozzle against the outside diameter of your barrel.

If the two numbers differ by more than 6 mm, then replace the nozzle. The second step is to measure how much material you're removing per minute. If you find yourself doing more than 20 pounds per hour, then you may need to upgrade your equipment.

If you're not removing enough material, then try increasing the flow rate. However, keep in mind that higher rates mean increased consumption. Finally, check your cost per pound. If you're spending $10 per pound, then you might want to reconsider your strategy.

These best practices will help you stay within budget when using air abrasives for sandblasting, grinding, polishing, and deburring applications.

09

KUBE BB SERIES Blast System

is an industry-leading Roller Conveyor Automated Shot blasting system., purposefully designed to reduce costs, reduce downtime, and improve your productivity.

The TF is an effective choice for fabricators and OEMs who need to remove scale and rust from steel profiles and sheets.

The system is available in a variety of configurations, from 4 to 12 throwing wheels, ensuring the proper preparation of each surface before painting.

Its modern compact design takes up less workspace and can be installed without major civil works in certain circumstances.

TF Series can also be equipped with powerful direct-drive motors from 11kW upwards. The system's tank has the ability to provide industry-leading brush/blow-off and secondary recovery solutions, ensuring maximum shot retrieval.

To learn more about KUBE TF Series, get in touch with our team here.