What Are Chain Knockers & Do I Need Them?

“So what’s the deal with chain knockers? Everyone tells me I should be cleaning cast iron with them, but my jetter units works pretty good. Do I need a chain knocker and how do I use one?”

Tuberculated pipe means that minerals in the drain water interact with iron in cast iron pipe and causes minerals to cling to the host pipe. This creats a buildup and the “crud ” that sticks to the host pipe. Jetting doesn’t remove as much of the tuberculation as you should remove to line the pipe, but many contractors assume it’s as good as it gets. In fact, I’ve watched many jetter contractors work for a couple of days trying to clean a tuberculated line with little success. This is where mechanical removal outshines hydraulic removal with water pressure. PSI or pounds per square inch is pretty straight forward regarding pressure and force, but measuring mechanical force to a surface is a little more difficult. Force is a product of speed (acceleration) ¬†and weight (mass) leaving us with force. This force can be substantially higher than pounds per square inch as used in water pressure in a typical Jetter. This is a mechanical force of a material as hard or harder than the surface it is contacting. Water pressure can achieve a high force and can cut pipe, depending on the pipe strength and thickness at a pressure between 30,000 psi and 90,000 psi. These forces are not typically found in standard jetting devices used for cleaning sewer piping. A more typical force is between 1,000 psi and 4,000 psi for clearing a drain line of things like roots, paper, diapers, and other debris flushed down sewer lines. While these pressures work great for that purpose it falls far short of the pressure (force) to remove tuberculated pipe debris, but a water driven chain knocker may remove it. I say may because the acceleration and mass in a water chain knocker is usually less than the mechanically produced mass and acceleration. ¬†There are machines that would develop enough pressure capacity to remove the tuberculation with water, but the roadblock is the condition of the pipe. If the pipe were structurally sound these devices could easily solve the cleaning issue with pressure only, but we often see old cast iron pipe in a less than pristine structurally sound condition making this approach risky for the cleaning contractor especially when approaching 30,000 psi. Coupling the chain knocker with the jetting device designed for sewer cleaning works well.

So, if our pipe is less than structural, won’t the chain knockers poke a hole in the pipe? That’s where centering axels coupled to a chain knocker that is restricted in diameter can give the operator a fine tuned control over getting the pipe back to as made diameters without damaging the pipe wall. The centering axels prevent the chain from striking outside of the parameters he operator sets. Centering axels can be simple brushes attached to the cable such that the chain knocker remains in the center of the pipe instead of dancing around freely. Coupled with the Ultra High Speed cleaning device or a jetting device, the task may be completed pretty quickly with a minimal effort and low investment in tooling.

There are many chain knockers available and we stock several different sizes to meet the different pipe diameters. These processes can be used for all lining methods prior to getting the lining or coating process completed.

Poorly Prepared Surface

Lining or coating over heavy tuberculation is the equivalent of painting over old exterior paint without anypreparation. Doing this sets up the contractor for failure. So concluding today, chain knockers tied to Ultra High Speed cleaning devices can make easy work of your cast iron rehabilitation project. Pipe Lining Supply provides all of these tools to make your life simpler.

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