In this post, we discuss an all-important subject matter – sludge in heat transfer systems. We focus on three effective ways to eradicate it. Before we dive into that, it is important to explore the genesis and implications of sludge within heat transfer systems. So, what exactly is sludge? It is a viscous dark material that coats heat transfer surfaces as well as the lower sections of holding tanks and expansion tanks. Sludge is formed when air mixes in with your heat transfer over time, resulting in the formation of dark gunk.
Essentially, a reaction known as ‘Oxidation’ occurs causing the heat transfer fluid to turn dark and increases in thickness. In an advanced state, highly viscous materials eventually turning into hard or waxy deposits in the system. This formation reaction is particularly known to occur progressively at high temperatures (in excess of 93°C / 200°F). In a nutshell, three key elements are known to fast-track oxidation and the development of sludge. They are air (oxygen), high temperature and time. There are many industrial applications that mirror these conditions. Take for instance, an exposed expansion tank without an inert gas blanket, an open bath chiller or a temperature control unit that is periodically exposed to air. Over time and with most industrial application running at higher temperatures, heat transfer fluid becomes oxidized and sludge emerges as the degradation progresses.
So, what does this all mean for your heat transfer system? You may have at least three main issues on the horizon. The first bothers on maintenance and downtime. A messy and sticky sludge coat of considerable thickness may cause you to shut down for unplanned maintenance, leading to the loss of production and profits. Don’t forget to account for the actual cost of maintenance. The costs definitely add up.
On a second note, there are energy cost implications that arise from the presence of sludge in your loop. Sludge adds an extra layer of heat transfer resistance thereby causing inefficiencies, and increased energy costs. Thirdly, sludge leads to an increase in the viscosity of your heat transfer fluid. The thicker the thermal fluid gets, the poorer it becomes when it comes to heat transfer coefficients. Basically, you may witness system alarms related to imprecise temperature control. At this point, it is needless to state that sludge formation must be adequately handled.
Our philosophy for sludge management at Relatherm Heat Transfer Fluids starts with prevention – preventing the sludge from forming in the first place. You should consider the use of a high-performance thermal fluid fortified with effective anti-oxidation additives. By virtue of its industry leading additive technology, Relatherm Heat Transfer Fluids are designed for maximum oxidation protection. More specifically, we offer a heat transfer fluid that has cleaning agents infused in it. They are called RelaClean and RelaClean FG. These are preventative maintenance thermal fluids that clean as they run in industrial and food-grade equipment respectively. They clean light to moderate varnishes very well and therefore limit the probability of sludge buildup.
Furthermore, there are other measures that help limit oxidation and sludge. Incorporate an expansion tank into your system if you don’t already have one. If you can help it, ensure that your expansion tank is not operating at a temperature higher than 93°C / 200°F. Moreover, injecting an inert gas pad in the air space above the thermal fluid in the expansion tank is very effective in protecting your fluid from oxidation.
Combine preventative maintenance with periodic heat transfer fluid testing and analysis and you have the requisite information you need to monitor, prevent and manage sludge buildup. Consult your fluid provider for help with this. Relatherm offers a ThermoFluid Care Program that you can always rely on. It includes free comprehensive heat transfer fluid testing and analysis. We report on parameters like Total Acid Number (TAN is an indicator of oxidation), viscosity and Flash Point. We are also able to conduct simulated distillation tests, Infrared Spectroscopy tests and Moisture content analysis.
If your heat transfer fluid is already overspent and sludge already exists in your system, do not despair. All hope is not lost. We know three tried and tested methods for beating sludge and getting your system back to a clean state. They are presented in the paragraphs below.
The first cleaning method on our list is mechanical or manual cleaning. This entails taking apart your heat exchanger, heater coils, or other heat transfer system including associated piping/lines and pumps. Afterward, you physically clean out the sludge with a scraper, wire brush or other mechanical devices capable of removing the sludge. This approach is not applicable to inaccessible systems. It is also time consuming and labor-intensive.
If your equipment is less likely to be effectively cleaned manually, then you should really consider chemical cleaning. There a few system cleaners on the market that are very effective in this regard. Your heat transfer fluid provider will likely have a solution for you. Relatherm Heat Transfer Fluids offers the most effective solvent cleaners designed for restoring and reviving heat transfer systems affected by fluid oxidation and sludge. We recommend RelaClean SC for heavily fouled systems containing sludge and hard deposits. It is a fast-acting cleaner that dissolves sludge and brings back your system online within hours. RelaClean LC is a concentrate cleaner that is used in large systems for which a full fill is cost-prohibitive. At a 10% treat rate, it disintegrates sludge and cleans your system. R-Clean is for cleaning out sludge and other degradation by-products from systems utilizing PolyAlkylene Glycol-based heat transfer fluids. More information on all our heat transfer system cleaners are presented here.
If you are interested in learning more about sludge mitigation and eradication or you have a system-specific question, we are always happy to help. Contact Relatherm Heat Transfer Fluids today.