Wear and abrasion can be expensive problems for companies using pneumatic conveying systems, both in terms of cost for replacement parts and in labor costs during system downtime. This is especially the case for bends within these systems. Wear is one of the most common problems in pneumatic conveying systems and because of this, we are frequently asked the question: “What can I do to help reduce wear of our pneumatic conveying elbows?”
In this article, you’ll find guidance and advice on different things you might consider to reduce the wear of your pneumatic conveying elbows.
Adjust the Velocity of your Conveying System
When it comes to wear, velocity is Enemy Number 1. Elbows at the end of long runs of pipe are the ones which wear out the fastest, and this is due to velocity (or more specifically due to Boyle’s Law, a gas law stating that the pressure of a gas increases as volume decreases under a constant temperature). There are two ways to counter the effects of velocity and reduce wear:
- Use shorter conveying line runs in your system. While this is not usually an option for existing systems, it is something to consider when planning a new conveying line.
- Decrease the air power. Small changes in velocity can have a big effect on wear. If you can turn down the power to just above the minimum value required for successful conveying it can make a real difference to the amount of elbow wear you experience.
Change the Elbow Radius
There are several variables that can affect the efficiency of bends in a system, and the style of the elbow tends to have most effect. While there is some debate about the effectiveness of using long radius elbows, the facts show they prevent wear-through more effectively than short radius elbows. This is not because they change the trajectory of the conveying particles. The particles still shoot out straight from the inlet to impact the back of the elbow. However, by having a longer radius, the wear area is spread out farther down the back, extending the life of the elbow. This will depend on the application, but almost without exception, using a long radius elbow is better than using short radius sweep elbows in terms of reducing wear.
Use Tougher Elbows
Using the wrong type of elbow often not only affects system wear, but also system pressure drop and product degradation. Sometimes abrasion problems are caused by using elbows that aren't equipped for the task at hand. If you’re using aluminum tube elbows and find that they wear quickly, then simply switching these out for steel tube elbows might solve the problem. Or you may be using a 16Ga elbow, in which case you could consider moving to a thicker gauge tubing or schedule of pipe to help reduce wear.
If fitting a thicker elbow is going to cause a ledge because of the different inner pipe diameters, then those “ledges” can be turned down and smoothed out to match the other lines. While simply changing elbow material or wall thickness change won’t help against tough abrasion problems, it can be an easy way to make a difference in certain applications.
Use Elbows with Wear-Resistant Linings
Elbows using wear-resistant linings are very effective, and there are all kinds of elbows for all kinds of applications. This includes ceramic linings, cement linings, composite lining, AR alloys, replaceable backs, and more. Using elbows that have abrasion-resistant linings are usually the most cost-effective solutions. Even better, many of these special elbows will fit perfectly into your conveying system without making any alteration to the conveying lines.
Use Specialized Elbows
There are several types abrasion-resistant fittings to choose from. These elbows are usually very short radius and often work by mechanical means. Vortex elbows, dead-end tees, and Ni-hard fittings are a few examples of specialized fittings. These can be great options for certain applications but also have their own drawbacks. They can be more expensive, take longer to procure, and affect the overall pressure in your system. Furthermore, these fittings can cause some turbulence on the outlet side of the elbow that may have to be addressed.
Find the Weak Spot in your Pneumatic Conveying System
Occasionally, elbows wear out because of weak points in the design of a pneumatic conveying system. For example, if your elbows are put in the system with threaded ends, that is a weak point. Those elbows will only stay in your system for as long as the thinly walled grooves hold out. Additionally, it is not unusual to see elbows wear underneath compression couplings. Moving to elbows with flanged ends, abrasion resistant spools, or simply increasing the tangent length on abrasion resistant elbows can eliminate these kinds of weaknesses.
As we’ve seen, there are many things you can do to reduce wear on your existing elbows, but sometimes your best option is simply a more effective replacement part. It’s really important to look for a solution that’s right for your needs and speak to companies with knowledge, expertise, and experience who offer a range of products for you to choose from.
At Progressive Products, we won’t sell you anything you don’t need – we’ll sell you the best quality solution that’s right for your system. If you need a replacement elbow, contact us to find the right one for you.