Heat, Flow & Truckmounts: The ICS Interview

August 14, 2002
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To better understand heat and water flow as they pertain to the carpet cleaning process, ICS Cleaning Specialist went to four of the top truckmount manufacturers and asked them five questions designed to help professionals in the field educate and better inform their clients, and possibly garner some new knowledge for themselves.

courtesy of Steam Genie

ICS Cleaning Specialist: How does introducing heat affect the cleaning process?

Bill Jensen: Most of the soil that we are being asked to remove when cleaning carpets is what was not picked up by a vacuum cleaner. This soil is bonded to the carpet by some type of oil or grease. When subjected to high solution temperatures, these oily soils become easier to remove from carpet fibers. Also, the higher temperatures tend to expand and relax the fibers, allowing them to release the soils much easier.
Shawn Forsythe: Heat is one of the four fundamental factors involved in the efficiency of soil suspension, or the separation of soil from the fibers being cleaned. The others are time, agitation and chemical action. Heat acts to speed up molecular activity, and in doing so, chemical action is increased by a factor of two for every 18 degrees of temperature rise above a theoretical baseline of 118 degrees.
This is not to say that cleaning efficiency is raised at this rate, but that chemical activity is so affected. However, some soil suspension is not directly attributed to chemical activity, but it can be generalized that the hotter the temperature, the greater the ability for the cleaning process to be effective.
Doyle Bloss: The application of heat in the carpet cleaning process has many benefits. One can summarize these benefits into two categories. First, heated cleaning solution directly benefits the construction and appearance of the carpet. Secondly, heated cleaning solution directly benefits the cleaning process and the chemistry of the cleaning process.
Many residential carpets require periodic hot water extraction cleaning as part of their texture retention warranty. Hotter cleaning solutions refresh and restore carpet texture. Watching the carpet cleaning process on a typical residential cut pile carpet can evidence this. The texture immediately responds to the hot water as the carpet is literally "fluffed" up by the cleaning process.
Heated cleaning solution has a larger capacity for the suspension of soil. It increases the rate of molecular expansion and chemical activity of most water-based cleaning solutions. This increased activity normally increases its capacity to clean. Hotter water evaporates faster, reducing customer downtime because the carpet dries faster. Hotter water breaks down water-soluble soiling faster. It reduces overall chemical usage because it reduces the surface tension of the fiber.
Glen Wilson: Heat has a positive effect on the cleaning process in several ways. For starters, the heat helps some chemicals to work faster on surface soils. The heat acts as a catalyst promoting quicker reactions between the chemicals and the soil. Heat also aids in the cleaning process by speeding up the breakdown of soils consisting of grease and oils.
All chemical reactions are accelerated by the addition of heat. As a general rule, the higher the heat, the more effective the cleaner. Of course, some fabrics can be damaged by excessive heat and you must know the heat limitations of the material you are cleaning.
Protein stains are the exception to the general rule. Protein stains such as blood, egg, and gravy should be cleaned with cool water. The heat from hot water can cook the proteins, making them more difficult to remove.

courtesy of HydraMaster

ICS: How much heat is "too much?"

SF: Increasing the temperature does lose value at a point using typical cleaning methods due to two factors. First is fiber incompatibility; certain natural fibers undergo permanent, undesired physical changes at too high a cleaning temperature.
Second is the physical property changes that occur in every liquid heated to the point of vaporization. It is important to maintain the majority of the cleaning agent in a liquid form at the cleansing interface. In a liquid state the solution exists to function as both an agitating and a flushing media. As such, aqueous (water-based) cleaners are often applied with an elevated pressure to impart physical agitation or "hitting action" upon the fiber to displace the soil. Additionally, the solution continues to act as a suspension and flushing media for the soil to be subsequently extracted.
However, if the cleaning agent is made to exceed the temperature where it flashes to vapor upon release to the open environment, the solution is denied these very important attributes. If the solution is so hot that it is only available as a pressurized vapor, it may serve to only "push" soiling deeper in the instant before flashing off, thereby not remaining within or upon the soiled surface to suspend soiling for subsequent removal by either vacuum or absorptive pad.
DB: In the early days of heat exchanger technology with truckmounts, several of these heat exchangers could build up temperature if the technician had set the cleaning wand down for a minute or two. Then a blast of extremely hot water could come shooting out of the wand for a few seconds when the valve on the wand was activated. Today, most heat exchangers use the ability to bypass water or hot air, in combination with sensitive electronic temperature controls, to allow the cleaning technician to accurately choose and maintain a specific cleaning solution temperature.
There are times when the conscientious cleaning technician does want to control or reduce the temperature of the cleaning solution. Because higher temperature activates chemicals, when an adverse chemical reaction is possible, heat may enhance that problem, e.g. a crayon or candle wax can cause colors to run if "hit" first thing with water that is too hot. This is usually overcome simply by identifying these types of spots in advance of the cleaning and dealing with them appropriately.
Some misinformed people have espoused the idea that olefin carpets can be "melted" by high solution cleaning temperatures. Olefin fibers are susceptible to burns created by friction-based heat, such as a heavy piece of furniture being dragged across a carpet. Olefin fibers are not damaged by higher cleaning-solution temperatures.
BJ: I think that once you begin to exceed 250 degrees at the machine, you have reached the point that can begin to cause the cleaner potential problems. However, if it is 15 degrees outside and the solution lines are lying in the snow, that can dramatically change the temperature of the solution as it leaves the wand. Depending on the distance between the jet on the wand and the carpet, you can lose anywhere from 15 to 30 degrees when the solution is atomized at the jet tip.
GW: "Too much" heat is determined by the various materials that are used in the production of the fabric/carpet. Each will react differently to heat. Therefore, it is important to identify the type of fabric/carpet being cleaned and adjust the temperature based upon those findings.

courtesy of Prochem

ICS: Won't heat damage or otherwise negatively affect some carpet materials, such as wool?

GW: Yes, wool is a natural material, the hair from a sheep, and it can get "the frizzies" from excess heat just like human hair. Seen under a microscope, a hair appears to be made up of many scales. Excessive heat and inappropriate chemicals damage these tiny scales so that they stand up at strange angles - creating the damaged appearance. This damage cannot be reversed once it occurs. Wool should be cleaned at temperatures no hotter than 150 degrees.
Olefin also has a low melting point. It will not be damaged by hot water, but can be damaged by heat from the friction of dragging a piece of furniture. If cleaning with a truckmount, solution hoses can sometimes get hot enough to damage olefin carpet if allowed to contact the carpet.
BJ: I think the biggest potential for damage from a solution that is too hot would be the possible loss of the heat-set twist of the fibers. Also, I have heard of solution lines and quick connects causing damage to surfaces that they are in contact with during cleaning.
SF: Yes, certain natural fibers are adversely affected by too high of a cleaning temperature. Both wool and silk can exhibit shrinkage and permanent texture changes if the fiber's temperature is too high. Typically the yarn manufacturer will stipulate the maximum allowable temperature at which the textile can be cleaned. It should also be noted that certain dyes, regardless of fiber in which it is used, can lack colorfastness at elevated cleaning temperatures. With all this in mind, it is important to know fiber content and to test for colorfastness when a potential problem is tenable.
DB: Most critics of the use of cleaning solution temperature in the cleaning process ignore the fact that during the manufacturing of carpet, carpet is exposed to dry and moist heat and live steam many times that exceeds the cleaning solution temperature that any professional cleaner can maintain. It can be exposed to heat during the heat-setting process, the dyeing process and the finishing process. If hot water itself damaged the carpet fiber, it would never make it out of the carpet mill alive!
It is still generally considered and taught in our industry that wool carpets should be cleaned with solution temperatures no greater than 160 degrees Fahrenheit. Historically, excessive heat on wool was seen as a potential contributor to problems such as shrinkage and cellulosic browning of the backing. When most wool carpets had jute backing, hotter cleaning solution temperatures could contribute to shrinkage or cellulosic browning of the jute backing. In neither case was the wool fiber itself harmed.
Today, since most wool carpet manufactured in the United States that is tufted has a polypropylene backing, there is no problem with using hotter water on wool carpets. We are unaware of any testing that demonstrates that heat hurts the wool fiber itself. If it did, where would the sheep go on really hot days?

courtesy of Steam Way International

ICS: Why is water flow such a hot topic these days?

BJ: Some manufacturers utilizing heat exchangers to heat their water have had to reduce flow in order to achieve higher temperatures; they are not capable of maintaining these temperatures under normal flow rates. You must have enough solution flow to do an adequate job of flushing the soil from the carpet. Both heat and flow are important pieces of the pie.
DB: Water flow affects the type of heating system you use. Heat-exchange truckmounts will generally limit their water flow to 1.5 gallons per minute. The solution/pressure system is always capable of more, but if you increase water flow, the heat exchanger, even on the best heat exchange systems made, will not be able to maintain temperatures at the machine greater than 200 degrees. Truckmounts that want a higher rate of water flow, but which also want to maintain cleaning solution temperature above 200 degrees, must use propane or fuel oil heating systems.
What is the value of water flow rates? Flushing. The more water you move through the carpet, the higher the level of soil flushing and cleaning solution removal. Using a lower water flow, when you encounter a dirty carpet you will more than likely take two "wet" passes with your cleaning wand. You will then usually take two "dry" passes. The dirtier the carpet is, the more passes you generally take to get it clean to your and the customer's satisfaction.
Compare this to only needing one wet pass with a truckmount equipped with a higher water flow rate. You actually clean the carpet with less water with higher water flow, because the higher water flow flushes the carpet clean with fewer passes. Less water means less drying time. When you combine the benefits of cleaning solution temperature with the benefits of water flow, you maximize your cleaning capacity while minimizing drying times.
GW: Water flow is an important topic these days due to the attention being focused on mold. The pressure, and subsequent water left behind in the carpet, will have a dramatic effect on the growth of mold. High humidity along with excess water left in the carpet after cleaning will allow mold development. Proper air movement, along with dehumidification, is sometimes necessary to help prevent the development of mold.
SF: High water flow generally exhibits greater ability for the cleaning solution to flush and suspend soils while simultaneously minimizing re-deposition. However, until recently, "high-flow" cleaning methodology was thought to be only achievable with the power of a truck-mounted system. This was because brute force vacuum power is reasonably able to recover the water flow effectively and minimize the egress of solution to areas where excess moisture could be potentially damaging.
Innovative portable manufacturers have devised differing means by which to meet the overall requirements of high-flow cleaning. By sheer numbers, portables still comprise the majority of equipment in use. Because efficiencies of electric blower motors have increased, along with the pioneering mechanics that put the vacuum source in close proximity to the carpet/wand interface, high-flow portable extraction is now possible, thus discussion of the subject to be greatly on the rise.

ICS: What is the relationship between water flow and the problem of "overwetting?"

DB: Overwetting is generally caused by one of two things. The first is when the solution and water flow rates applying moisture to the carpet are not in equilibrium with the recovery capacity of the vacuum system. Almost every manufacturer of any type of hot water extraction equipment takes this factor into consideration of the design of their equipment. They will make sure that the vacuum system is fully capable of removing the maximum amount of water that is applied to the carpeting.
Recovery rates vary. If the technician were using the equipment properly, without "rushing" through the job, the equipment itself would not be the main culprit in overwetting. The exception to this would be if the technician is not cleaning and checking the filter screens in the waste tank of the machine. If you restrict the air movement of the vacuum system, you can cause overwetting and extend drying times
The second, and much more likely, cause of overwetting is when the soiling conditions, including spots and spills, are excessive. In order to get the carpet "clean," the conscientious technician takes multiple wand passes across the carpet, trying to improve the appearance and get it "clean."
SF: "Overwetting" is a condition whereby materials of the carpet's construction, not designed or desired to be impacted by the cleaning process used, are either wetted or are wetted in such a way that it be comes difficult to remove the moisture before damage to the textile occurs. Carpet backing is generally subject to damage by moisture and cleaning compounds/agents if allowed to stand in contact.
Overwetting can be avoided by systematic effort to either minimize moisture in the first place, or to affect removal of such very rapidly. Accordingly, when high water flow is used as a means of cleaning, it must be controlled with efficient removal of the solution with a certain urgency. This is often done with the use of high airflow/lift vacuum recovery systems combined with good operator recovery technique. Most powerful truck-mounted systems are purported to excel at providing the means for rapid and powerful vacuum recovery. More recently, some portable equipment has proven to be effective at allowing for high-flow cleaning while being able to extract in proper proportion.
BJ: I believe that overwetting comes from operators who have to make too many cleaning passes because they are using their solution detergent as their primary cleaner instead of a pre-spray or traffic lane cleaner. Detergents contain high levels of surfactants, or wetting agents. They should be considered rinse or flushing agents.
If you are relying on your rinse detergent to do the bulk of the cleaning, you will frequently need to do multiple passes, and those wetting agents will penetrate a little farther into the carpet with each pass guaranteeing long dry times.
GW: The cleaner must be properly trained to apply the correct amount of rinse extraction solution and the appropriate techniques for recovery of the solution that is applied. An excessive flow of water can develop into an overwetted situation and will require extra effort for its removal.
An important aspect of water is that it is a blessing in cleaning and a devil to pay if left as a residue. In the case of a carpet that has been overwetted due to flooding or in an effort to address excessive soil conditions, it is most important to remove as much of the water as possible with extra drying strokes, air movers and dehumidifiers, if needed. Humidity, pressure, vacuum, waste-tank efficiency, all play an important part in water removal.


Bill Jensen has been in the carpet cleaning industry since 1971. He has been with HydraMaster for the past 12 years, and is currently the director of sales.

R. Doyle Bloss is the senior vice president for Steam Way International in Denver. He has an intense interest in providing practical applications to help the professional cleaner and restorer find profitable solutions and better understand technical cleaning issues

Glen Wilson is the products manager-equipment for Prochem. He has nine years of sales and marketing experience.

Shawn Forsythe is the vice president of research and development for Steam Genie, Inc. He has been in the technical portion of the industry for almost 20 years, and also serves as secretary/treasurer of the Carpet & Fabricare Institute.

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