MechChem Africa May-June 2021

⎪ Maintenance and asset management ⎪

Tube and drain cleaning – what you need to know

Hawk Pumps, manufacturers and distributors of quality high-pressure pumping and cleaning equipment, shares insights into high-pressure tube and drain cleaning and the different nozzles used to remove the different substances causing restrictions and blockages.

Where sand is the main problem, flounder nozzles rise up and over blockages for the rear facing nozzles to fluidise the blockage, which enables the water flow to carry the sand back to the manhole.

P ipe cleaning machines have various requirements in order to function at their best. Some of the problems these machines need to be able to overcome include the following: • Boiler and heat exchanger tubes gener- ally get a layer of various types of scale that restrict water flow and reduce heat transfer. This lowers the flow and increases the amount of fuel needed to overcome the insulating effect of the scale. • Slurry transfer pipes in various indus- tries tend to become restricted by solids deposited on the internal walls of the pipes. • Waste drain pipes in industry, hotels, hospitals andgarages suffer fromdepos- its of grease and other sticky materials, especially from kitchen waste. • Sewers are notorious for clogging, usu- ally from foreign objects being flushed into the system. • Rain water drain pipes and stormwater drains tend to have litter and sand set- tling in the bottom of the pipes, eventu- ally blocking them completely, causing flooding during rain storms. Pipe cleaning machines all have one thing in common: they need special nozzles designed for each specific application. High pressurepumpmachines are readily available or can be custom designed, but the choice of the correct nozzle, water flow and pressure is very important.

The various types of nozzles have a few things in common. Most have jets facing backwards, which serve two main purposes; to pull the hose into the pipe and to clean the pipe’s walls. For cleaning walls, the jets tend to face backwards and outwards at a large angle. Sometimes, a forward facing jet is not necessary, which allows larger, rear facing jets to be fitted. If the problem is a blockage, a forward facing jet is important, because the rear facing ones don’t spray out- wards as much, making it harder for the forward pulling power to overcome the negative effect of the forward jet. Boiler tube nozzles usually require relatively low volumes at higher pres- sures to cut through the scale, which can be extremely hard. They don’t depend much on rear jets and don’t have front ones, but rather have side jets on a spinning body. Occasionally, when the tube is all but blocked, a chisel nozzle with sharp hardened facets in front is needed to physically break the scale with forward facing jets. These nozzles are fitted to rigidpipes, rather thanflexiblehoses. The pumps needed here have lowvolumes of about 20 ℓ /min at 500 bar pressure. Slurry transfer pipes require simple ‘bomb’ shaped nozzles with rear facing jets. Here, depending on the pipe diameter, a medium volume pump, typically 80 ℓ /min of flow at about 150 to 200 bar is used. Occasionally, a nozzlewith spinning chains will be needed to improve the cleaning effect. Waste drainpipes are alsousually cleaned using ‘bomb’ nozzles and require pumps simi- lar to the slurry pipe applications. If the pipe is blocked, a nozzle with a front jet is called for, while hardblockages need cutter nozzles. Sewers vary in diameter and have dif- ferent degrees of blocking. For normal domestic sewers, a 30 ℓ /min pump at 150 to 200 bar will suffice. The nozzles required are simple mini-bombs with forward and rear facing jets. Mains sewers are of a large diameter – up to 300 mm but usu- ally about 200mm– and these require a minimumof 80 ℓ /min at 150 to200bar. A 120 ℓ /minpumphelps topull thehosebet- ter, especially where the sewer has a long space between manholes. Cutter nozzles,

chain flail nozzles and bomb nozzles are all used in this application. Rainwater and stormwater drains require much larger pumps. They usually need 150 to 200 ℓ /minat150to200bar. Bombnozzles can be used, but where sand is the main problem, the ‘flounder’ nozzle is the most effective. This nozzle consists of a block of metal with a pointed front and usually four rear facing nozzles. When the nozzles reach sand, they tend to ride up and over it and, in doing so, cause the rear jets to agitate and fluidise the sand. The large volume of water carries the sandback to themanholewhere it is removed, either physically or by means of a jet pump that only needs a small portion of the pump flow to push the sand out. Hawk is a manufacturing company that primarily creates industrial high-pressure pumping and cleaning equipment. They also manufacture spraying solutions, including industrial nozzles. One of Hawk’s biggest differentiators is that they have the capacity to manufacture and custom design machines tailored to specific customer needs. Hawk serves a wide range of customers from virtually every industrial sector, includ- ing processing plants, factories, workshops, contract cleaners, drain & sewer cleaners, car, truck & bus washes, mines, agricultural and more. hawkpumps.co.za Chain flail nozzles are needed for cutting through and removing accumulated roots and debris from sewers.

Bomb nozzles with front, rear or both front and rear facing jets are used for drain and sewer pipe cleaning, depending on the material that needs to be removed.

May-June 2021 • MechChem Africa ¦ 9