How To Use The Spiral Tube Brushes?

The variety of industrial tube brushes and cleaning heads available can be quite confusing for plant managers who are new to maintaining boilers and heat exchangers. Even experienced professionals might need a refresher when moving to a new facility or when new systems are installed. Luckily, there are only three essential things you need to know in order to select the best one for the job.

1. Tube Size

When it comes to tube brushes and cleaning heads, the Inner Diameter (ID) is the measurement that matters the most. ID is the distance from one side of the inside tube wall directly across to the other side. If you don't know the tube ID of the equipment you're cleaning, you can measure it using a mechanical hole gauge or a digital micrometer. If you know the tube wall gauge and Outer Diameter (OD), you can also use our Tube ID Smart Chart. OD includes the thickness of the tube wall itself. So, it's always slightly larger than ID. Heat exchangers typically have smaller diameter tubes, ranging from about 1/4 to 1-1/2 inches. Boilers generally have larger diameter tubes, ranging from 1-1/2 to 4+ inches.

2. Tube Type

Besides the size, there are a few other things you need to know about the tubes that are going to be cleaned. For example, are they straight or curved? As you might expect, straight tubes run straight through the length of the pressure vessel and exit at the opposite end. This is typical for fire tube boilers, as well as many shell and tube type heat exchangers in use today. However, water tube boilers with curved tubes and U-tube exchangers (pronounced the same as YouTube) are also not uncommon. Unlike straight tubes, U-tubes do not exit at the opposite end but instead curve back around and return to the front tube sheet. Curved tubes require a cleaning head that can make its way through the bend.

Some heat exchanger tubes are lined with twisting ridges like rifling. These are known as internally enhanced tubes. The spiraling design allows fluid to flow through the tube more smoothly and efficiently with less turbulence. Dual diameter brushes are engineered to reach the high and low areas of internally enhanced tubes.

It is also crucial to know the type of metal the tubes are made of in the pressure vessel that needs to be cleaned. The tube and brush metals should always be compatible to prevent damage that could shorten the service life of tubes made of soft metals. Non-ferrous metals, which do not contain iron, such as copper, brass, and aluminum, are softer than ferrous metals like steel and stainless steel, which do contain iron. So using a harder steel brush in a softer copper tube will scratch and erode the internal surface, leading to premature corrosion and eventual leaks. Softer bronze brushes can be used with copper and brass tubes. Stainless steel can be used with titanium and copper-nickel alloy tubes (also known as Cupronickel). Plastic nylon brushes are safe to use with any metal.

3. Deposit Type

Different heating and cooling systems, depending on their maintenance history, can accumulate various types of dirt, grime, and slime. For instance, dry black soot may build up in fire tube boiler tubes over time, while mushy gunk and hard scale can form in chillers, absorbers, and water tube boilers. HVAC tube deposits can be classified into the following four basic categories:

Light to Medium Debris:

When maintenance is performed regularly on a seasonal basis, you are likely to encounter only light to medium debris. In such cases, spiral brushes can be effective. They work in conjunction with water delivered through the drive unit shaft to create a flushing action that assists in the cleaning process. When the water flowing back out of the tube becomes clear, it indicates that the tube is clean, and it's time to move on to the next one. Remember to always match the spiral brush metal to the tube metal. Use hard ferrous metals in ferrous tubes and softer non-ferrous metals in non-ferrous tubes.

Soft Powdery Deposits:

In some cases, moderate deposits may require more than just a spiral brush. For rust, scale, and chemical precipitates, an expanding brush with replaceable bristles is a good option. As the head spins on the cleaning unit shaft, the bristle cartridges expand via centripetal force to conform to the interior circumference of the tube. Expanding brushes tend to last longer than spiral brushes. As the bristles wear down, the cartridges simply rise further to maintain contact with the tube wall. Once the bristle cartridges have worn too far, they can be replaced with new ones. They are available in steel, stainless steel, bronze, or nylon to match the tube metal. A swing frame brush offers similar expanding capabilities for larger diameter boiler tubes.

Soft, Wet, and Gummy Deposits:

Microbiological, biofilm, or "mud" is a thicker and heavier gunk that needs to be scraped off the tube walls. An expanding scraper is ideal for sludgy deposits, including marine growth. Just like an expanding brush, the expanding scraper head conforms to changes in the inside diameter of the tube, providing an efficient cleaning action along the entire length of the tube. Scraper cartridges are also easily replaced when they wear out. Unlike the bristles of a brush, the scraper blades are less prone to becoming clogged with wet and gummy debris. When used in conjunction with a flexible holder, an expanding scraper can be used to clean curved tubes in water tube boilers and U-tube heat exchangers. For extremely thick gummy deposits in larger diameter tubes, a cutter head may be necessary.

Brittle or Hard Scale:

For tubes with light limescale or calcium scale build-up, a buffing tool is often sufficient to remove excess debris after an initial pass with an expanding brush or scraper. Heavier soft or hard scale deposits require the use of a cutter head. Cutter heads come in various sizes and shapes, ranging from a single cutter head for thin scale in smaller diameter tubes to those with multiple cutters for removing thick encrustations of hard scale in larger diameter tubes. In systems that have been neglected for a long time and are completely clogged with hard scale and coke, a carbide-tipped cutter bit or drill head on a universal joint may be needed to bore through the blockage. A P-Brush should then be used to complete the cleaning job after punching through the clog.

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