Cold Process Materials Need Heat Too!

Using a cold process heater to reduce viscosity

Written by John Cleasby and Karen Cleasby
Published January/February 1998 in Western Roofing Magazine

Exactly what is a heat exchange unit? It is a warming kettle or better known as a "pig", specifically designed for heating various cold applied products that are of a high viscosity such as cutbacks (mastics). In order for these materials to be sprayed evenly and efficiently with the least amount of wear and tear on your pump system, they must be reduced to a low viscosity. This is precisely what a heat exchange unit does. It heats the transfer oil that in turn warms the material. When the material is adequately warmed, its viscosity is reduced allowing for a continuous, uniform flow of the material.

Both equipment and material manufacturers alike strongly recommend the use of a warmer when using cold process materials. "A warmer should always be used even during the hot summer months," said John Smernoff of Henry, "this way, the material is flowing continuously to the tip." Representatives of Tremco further explain the necessity of using a heat exchange unit. "Heating the BURmastic between 90 - 100 degrees Fahrenheit improves the ability of the material to spray evenly. By keeping the material at a consistent temperature, regardless of ambient conditions, the material’s ability to spray does not vary. Heating the Burmastic will improve the initial bonding of the system causing it to become tightly adhered in a shorter amount of time."

Many questions asked regarding cold process application are associated with the proper set-up of the heat exchange unit and pump system. The correct composition for the equipment is depict in the following diagram. First set the pump into the 55 gallon material drum. Keep in mind the importance of storing material drums in a heated, dry facility with an average temperature of 70 degrees. This prevents the material from hardening and making it difficult if not impossible to pump. Not to mention the costly wear and tear on the pump system. Representatives of Tremco do not recommend the use "flexible band strap heaters, open flame torching or the use of standard or oil jacketed roofing kettles. In addition, indirect heating through the use of space heaters or "salamanders" can also be dangerous and is not recommended." In the past, band heaters were an acceptable means for warming most drums. However, be aware that there are material manufacturers that line their drums with plastic liners so that the containers are easily disposed of at dump sites. Given this situation, you can imagine if the drum were to over heat using one of the above methods; the plastic liner would melt into the material or at worst, the whole drum could combust! The importance of properly storing and heating the material should never be overlooked.

Next, make sure the heat transfer unit is set up downstream from the pump. This allows gravity to work with the material. Connect the pump to the heat exchange unit using a maximum of 10’ material hose with a 1" I.D. (inside diameter) capable of withstanding 4000 p.s.i. Attach this hose to the inlet valve and attach the spray hose to the outlet. Spray hose is not to exceed 300’ in length. It is necessary to use 1" or ¾" I.D. high pressure hose that is double wire braided with a working pressure of 4000 p.s.i. Keep in mind that the last 25’ to 50’ of hose may be ½" I.D. in order to increase pressure and atomization at the tip. Note that the outlet of the heating unit has a bleed off valve located on it for checking the material and for eliminating any air in the system. Warning - stay clear of the opened bleed off valve because hot material may flow from it. Furthermore, it is important to bleed off any air that may be in the system. This will prevent the material from spraying an inconsistent pattern. It is also pertinent that trapped air pressure be bled out before disconnecting both the inlet and outlet hoses. We at Cleasby Mfg. strongly advise against the practice of using a truck bed as a work staging area for material containers, roofing pump(s), propane tanks and propane operated heat exchange units. Should the job be interrupted or material hoses begin to leak, the material may be exposed to the open flame of the heat exchange unit and could possibly lead to fire and/or injury.

The equipment is now properly set-up. Let the job begin. Using a hand pump for a 55 gallon drum, pump approximately 45 to 50 gallons of grade #46 transfer oil into the warmer. Reserve the remaining oil to be used as needed. We specify a grade #46 because of it’s unique chemical properties. It is resistant to thermal cracking and chemical oxidation as explained by Chevron representatives. It is also non-corrosive, non-toxic and has a low odor level. In other words, it remains "homogenous" and it’s components will not separate after heating. Given these properties, #46 oil will transport heat more efficiently than most and will last longer. Caution, do not over fill the warmer with oil so as to allow for oil expansion. Also, check to make absolutely sure that there is no water contamination of the heat transfer oil. If there is - do not heat! The oil will boil and overflow. In the event of water contamination, we recommend changing the oil. When changing the oil, remember it is a petroleum product and needs to be dispensed of properly. Just a manufacturer’s note, we recommend completely changing the oil once a year whether it is contaminated or not.

At this point, the oil is loaded. Begin heating the unit slowly until it reaches 300 degrees Fahrenheit. Never heat oil more than the manufacturer’s recommendation. OSHA states that the oil must stay 50 degrees below its listed flash point. Some material manufacturers will also specify at what temperature to heat the material. Once the oil reaches temperature, open the bleed off valve before pumping to vent any air in the system. Remember to stay clear of the opened valve. Once a continuous flow of material has been established, close the valve tightly. Now begin the process of pumping the material into the warmer. As the material continually moves through the warmer, heated oil will warm it, reducing its viscosity. The result, a continuous, uniform flow of material.

 There are so many variables that affect the proper installation of any roof system. Just as the heat exchange unit affects the consistency and flow of material, the spray pump is vital for dispensing the material onto the roof. However, this is a whole other topic to be covered in a future article. Our purpose here is to dispel some beliefs that warmers are not necessary when applying cold process materials. John Smernoff of Henry Co. said it best, "A warmer should always be used even during the hot summer months."

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