When it comes to choosing tools for large diameter pipe cleaning, there’s no shortage of options. But what considerations should you really focus on to improve performance — and profitability? No matter how well a problem is diagnosed with television inspection equipment or how powerful the jetting pump, you’re still dependent on the jetting nozzle at the end of the hose to do the job. Knowing how and where cleaning power can be lost can help you minimize those losses and clean more effectively.
Although each job is different, there are some general rules that apply broadly. Understanding these will help you choose the right tools for the job, allowing you to work efficiently while keeping your customers happy and your business profitable.
Number of Jets
Pressure is the force that allows water to do its job. But there are many ways pressure can be lost. One is the number of jets on the nozzle. It’s a common misconception that if a nozzle with five jets is good, then a nozzle with 10 jets must be better. In fact, the opposite is true. The more jets the nozzle has, the less force is produced by each one — because your pump’s pressure is divided by the number of jets. If one jet isn’t capable of cleaning the deposits it impacts, then two or 10 of the same jets won’t be any more effective. A nozzle with fewer jets will have harder hitting jets — therefore you want the fewest number of jets that can get the job done.
Although non-rotating nozzles have no moving parts and are therefore low maintenance, rotating nozzles have a major advantage: They will clean a pipe much more thoroughly because the rotation allows the water to cover the entire pipe. A non-rotating nozzle will clean only where the jets are pointed, leaving the rest of the pipe dirty. Because of that, fewer jets can be used on the rotating nozzle, and, as we already know, that means more power to each jet. To maintain jet quality in a rotating nozzle, the rotation speed must be controlled. If the nozzle rotates too fast, the jet will lose strength. In addition, the dwell time — or the time the jet hits the cleaning surface — may be too short. Rotation control can be achieved using a viscous governor or using magnetic or centrifugal mechanisms. In very large diameter pipes, air motors and gear boxes may be required to get a sufficiently low rotation speed. Whatever the method, rotation control is a must when choosing a rotating nozzle.
At the pressures commonly used in pipe cleaning, all water flows will contain some turbulence. Turbulence seriously reduces jet power — and the drop in pressure increases with flow—so it’s important to minimize it. Significant turbulence exists both upstream, before the water exits the jet orifice, and downstream, after it exits. Fortunately, two things can help us avoid the worst effects of these turbulent zones. First, the turbulence that exists upstream of the jet orifice can be reduced by creating a straight run before the water exits the orifice by using pipe nipples — also known as extension arms. The addition of flow-straightening vanes can be a big help. These flow straighteners provide the water with a straight run before it exits the orifice, minimizing upstream turbulence. A number of effective straightener vanes are available.
Second, we have to consider the turbulent zone that exists downstream of the orifice. By placing the jet orifice close enough to the pipe wall, we can make sure that water impacts the pipe wall before power is lost to downstream turbulence. This can be done using a centralizer, which keeps the nozzle centered in the pipe, and if necessary, extension arms. With a jet orifice placed just a few inches from the pipe wall, you can expect a powerful, coherent jet with the power to remove debris and deposits.
If you have ever replaced an old hose with a new, longer one, you may have noticed that jetting with the old hose was more effective. That’s because water loses velocity due to friction as it travels through a hose. So, a shorter hose will have less pressure drop by the time the water reaches the jetting nozzle. Larger diameter hoses can also reduce pressure drop, but they’re heavier and harder to pull. The optimum solution for minimizing pressure loss depends on the pump being used, the length and size of the hose, and other considerations like the distance between access points. For example, in some cases it might make sense to pull a hose to the end of a run then reconfigure the jets and clean while pulling the hose backwards. In another example, a 600-ft, ¾-in. hose matched to a 3,000-psi pump at a flow of 44 gpm can lose 44 percent of its power by the time the water reaches the nozzle. Simply changing to a 1-in. hose will result in a pressure drop of only 10 percent, resulting in 52 percent more power at the nozzle. Matching hose and pump combinations correctly can help ensure you don’t suffer unnecessary pressure loss.
Nozzles deteriorate with use as the water flow slowly erodes the orifice channel. This causes a visible loss of power, since the size of the orifice is key to the force of the stream. In applications of 20,000 psi and below, there are three materials commonly used in jetting nozzles: ceramic, tungsten carbide and hardened stainless steel. Ceramic is probably the most erosion-resistant of the three, but the drawback is that it is very brittle, and therefore breaks easily. Tungsten carbide nozzles wear quickly because of erosion of the cobalt binder used to hold the hard carbide particles together in the composite. Hardened stainless steel has been proven to outlast tungsten carbide in many applications. Anyone who works with tools professionally knows that investing in long-lasting tools is a smart business practice.
Safety should always be a top priority on the job and that’s especially true when working with high-pressure jetting nozzles. To prevent a tool from “backing out” and turning toward the operator, you may need to have a rigid pipe called a stinger added to the jet assembly, making it impossible for the jet to turn around in the pipe. Centralizers for large pipe cleaning can also eliminate the possibility of tool turn around.
As most contractors know, the key to happy customers and profitability is efficiency and effectiveness. There are lots of factors that are beyond our control on the job site, but choosing the right tools for the job is a key decision that is within your control. By knowing what factors can rob you of cleaning efficiency, you can choose tools that will minimize those losses—and allow you to get the job done quickly and effectively.
Bill Shires is director of marketing and business development for StoneAge Tools and Dave Welz is a technical writer.