Choosing Proper Nozzles for High-Pressure Waterjet Cleaning
Original article by MSW MAG / About the Author: Jim Aanderud is owner of Innerline Engineering, a video pipeline inspection company based in Corona, Calif.
Understanding nozzles and how they work is a key step to becoming a successful pipeline cleaning operator. Knowing the proper use of each nozzle will ensure that you always select the right one for each job. It’s important to note that it may take up to 10 different nozzles to successfully clean in 90% of the situations encountered.
There should be no guessing when selecting a nozzle for cleaning operations. Nozzles are designed for specific cleaning applications. If they are not used for their intended purposes, then they won’t be as effective.
In order to understand nozzles, contractors must first understand the relationship between pressure and flow ratio. In general, drain cleaning and debris removal, you want low pressure and high flow. As debris accumulates, you want sufficient flow to move the material down the line.
As you move into harder material such as encrustation, mortar, or even solidified grease, you want to operate at a higher pressure and lower flow to dislodge the material.
Keep in mind that a single nozzle is seldom sufficient. You need to change nozzles as conditions change. For example, once encrustation and mortar is removed from the pipe wall, you need to switch to a nozzle that can move the material to the downstream manhole to be vacuumed out.
Many cleaning operators have a favorite nozzle they use in a variety of conditions. Just because it cleans well in one situation, they assume that it will work in every other situation. But this is certainly not the case and an operator’s cleaning effectiveness may fall short.
Jet trajectory is critical to nozzle selection. Jet angles in the 30 to 45 degree range are ideal for cleaning pipe walls. However, they provide minimal thrust and are unable to move the debris down the line. Jet angles in the 0 to 10 degree range are primarily designed for thrust to propel a nozzle up the line. Most penetrators will have jet angles in this range because they are designed to shoot up the line as fast and as forcefully as possible to punch through a root blockage. These angles are also the most efficient for moving debris. A jet in the 15 to 20 degree range can clean the pipe wall, propel the nozzle and move the debris, but using two nozzles for each job would be more efficient.
Many of today’s nozzles incorporate a combination of jet angles to perform multiple functions simultaneously. They can clean the pipe wall and move debris while providing the thrust necessary to perform these tasks.
When selecting a nozzle, consider the type of cleaning you will be doing. Are you clearing blockages, removing heavy sediment, cleaning the radiuses of the pipe walls, removing grease or roots, or eliminating tuberculation and mineral deposits? Each of these requires a different type of nozzle:
Breaking blockages: Penetrating nozzles have a single function: Shoot up a line and break through a blockage. Their low-degree jet pattern delivers maximum thrust to provide as much penetrating power as possible. Most penetrators also have forward jets, which increase penetrating effectiveness.
Cleaning debris: Nozzles that move debris down the line also have a low-degree jet pattern. Some of these nozzles will incorporate multiple angles, but their primary function is to move heavy sediment as efficiently as possible down the line so the material can be vacuumed up.
Radius cleaning: Radius cleaning is required when there are bends in the pipe. Many nozzles tend to leave debris along the inside of the radius. Effective cleaning under these conditions requires a nozzle with 45-degree jets to knock debris off of the pipe wall. This process must be followed with a 10-degree nozzle to move the debris out of the pipe.
Grease cleaning: There are various nozzle types that work effectively for cutting through and removing grease from a pipeline. Spinning nozzles are the best option for these jobs. Most spinning nozzles incorporate 30- to 75-degree jets for cutting and 10- to 20-degree jets for thrust. Chain flails also work well to knock the grease from the pipe wall. After a chain flail has been used, a cleaning nozzle is needed to move the grease down the line.
Light to medium roots: Slow rotational spinning nozzles work well with light to medium roots. Older rotating nozzles tended to spin too fast and didn’t work as effectively as the slow spinning nozzles available today.
Heavy roots: Chain flails and root saws are the most effective tools when dealing with heavy roots. If possible, a camera should be used in conjunction with these mechanical nozzles in order to ensure that the pipe is not being damaged.
Nozzles are broken down into three tiers based on efficiency for moving water. Tier one nozzles have orifices drilled out in different locations and sizes and at different angles, which can mean inefficient flow dynamics and less performance. When the water enters the nozzle, it hits into the back of its interior, then bounces out in the opposite direction while exiting through the drilled holes. During this process, a considerable amount of energy is lost. These nozzles are relatively inexpensive and don’t last as long. Over time, the drilled jet holes wear out and the nozzle becomes ineffective.
Tier two nozzles are more expensive, but have better flow dynamics than tier one nozzles. They have replaceable inserts that also straighten the jet streams as they exit the nozzle. When the jet orifices wear out, these nozzles can be restored to their full operating capacity by replacing the inserts.
Tier three nozzles are designed to maximize the efficiency of water flow. Flow dynamics are designed to significantly increase the water pressure exiting the jets. Under certain conditions, these nozzles can increase cleaning efficiency. Their only downside is the fact that they can be very costly. However, the cost is usually offset by increased efficiency.
Nozzle design has made huge strides in recent years. By understanding how nozzles work and staying informed of available technology, cleaning operators can clean lines more efficiently and effectively.