Conduit Seal Effectiveness

1 CCoonndduuiitt SSeeaall EEffffeeccttiivveenneessss 659 Van Meter Street Cincinnati OH 45202-1568 T: 513 241 1230 F: 513 241 1287 Email: Website: By Scott T. McGlamery, ; and Bret T. Heckman, Department of Electrical Engineering, Hixson, Cincinnati, OH Abstract - When there is a significant temperature difference between two adjacent spaces, maintaining an effective vapor barrier between the spaces is essential to prevent vapor infiltration and condensation in the cold space. Conduit penetrations through walls and ceilings can compromise the vapor barrier if not done properly. This paper reports the results of testing four different Conduit vapor seals. I. Introduction GMP (Good Manufacturing Practice) facilities often contain spaces that are conditioned to low temperatures for product / ingredient storage and to maintain product temperature during processing and packaging.

2 Typical temperature requirements range from 60 F to 0 F or lower. At these temperatures, the dew point in the room is often below the temperature in the adjacent spaces. This makes an effective vapor barrier essential for preventing vapor infiltration and condensation. Vapor and condensation control is particularly critical in any penetration that could provide a niche where microbial growth could occur out of sight and in an area that is difficult to clean. Conduit penetrations are of particular concern, because they are a closed system capable of transferring vapor between spaces, and capable of holding water in a niche that could go unnoticed for a long time. Condensation occurs when a Conduit system is open to a space with warm, humid air, and a space with a dew point below the temperature of the adjacent space.

3 Vapor pressure pushes the water vapor towards the cool, dry end of the Conduit , where the lower temperature causes the vapor to condense inside the Conduit . Over time, the condensation can fill the Conduit and the enclosures they serve with water, creating a dark wet niche that represents a food safety concern. Conduit drains are sometimes used to allow any condensation to drain out of the Conduit system, but the first line of defense should be to prevent the condensation from occurring in the first place. After observing the failure of several types of Conduit seals in the field, either due to workmanship, Effectiveness of the type of seal employed, or other issues, we tested four types of Conduit seals to determine which seal was most effective.

4 The four seal types were: neutral cure silicone, expanding polyurethane foam sealant, duct seal compound, and hazardous location sealing compound. The tests evaluated ease of installation, vapor infiltration, and pressure resistance. II. Test Setup and Procedure Before testing could begin, an apparatus was built to emulate facility conditions. This arrangement consisted of 3/4" Schedule 80 PVC conduits mounted vertically and horizontally. Conductors were cut at 20 long to project out of the top and bottom of the conduits. A Conduit fill of four Thermoplastic High Heat-resistant Nylon-coated (THHN) conductors and a Conduit fill of 12 THHN conductors were used for the experiment. A Conduit body was affixed to one end of the Conduit to replicate a junction point in the Conduit system.

5 In the case of the hazardous location sealing compound, a Class I Div 2 Conduit seal was used. See Figure 1 for the apparatus set up. Figure 1: From left to right Silicone, Expanding Foam, Duct seal , and Hazardous Location Compound Sealant CCoonndduuiitt SSeeaall EEffffeeccttiivveenneessss 659 Van Meter Street Cincinnati OH 45202-1568 T: 513 241 1230 F: 513 241 1287 Email: Website: A. Ease of Installation Each one of the sealants was placed in the vertical and horizontal conduits. Workmanship of installation for each was conducted as good as or better than observed in the field. The sealants were then allowed to cure for at least eight hours or per manufacturer s requirements. The ease of installation and level of workman-ship required was recorded.

6 After testing was completed, the conductors were removed from the seal to test the ability to remove conductors for renovation or replacement. B. Vapor Infiltration The vapor infiltration test assessed the sealant s ability to prevent vapor from passing through the Conduit . The horizontal conduits were mounted vertically for testing. Water was used to simulate vapor infiltration due to the logistical complexities of testing with water vapor. The measured amount of 25mL of water ( 3/4 of water in a 3/4" Conduit ) was poured into the top of each Conduit . The bottom of the Conduit was then observed for any leakage. The vapor infiltration test with 25mL of water was the equivalent to approximately psig of differential pressure on either side of the Conduit seal .

7 C. Pressure Testing Pressure testing was conducted to find the failure point of each sealant. The pressures employed significantly exceed those that would normally be found in a facility. To pressure test, the remaining space at the top of the Conduit was filled with water. Then compressed air was applied to the top of the Conduit to force water through the sealant. Increments of 1, 5, 10, and 15 psig were used to test the product s resilience. In some cases, the pressure was increased beyond 15 psig to find its failure point. III. Analysis A. Ease of Installation Neutral Cure Silicon: The silicone was applied using a standard caulking gun. A 1/4" bead opening was cut on the end of the tube. Next, the tube was inserted into the Conduit body as far as it could go.

8 The caulking gun trigger was pulled to full compression to apply the silicone. The tube cannot be inserted into the Conduit body far enough to make an effective seal . The installation was awkward and cumbersome. See Figure 2. A light pull on the conductors could easily break the seal and remove the conductors. Figure 2: The use of a caulking gun to apply silicon Expanding Foam: The expanding foam straw attachment was inserted two inches into the Conduit . The expanding foam trigger was then held for approximately one second to apply foam. The installation was quick, simple and error proof. A strong pull on the conductors was required to break the seal and remove the conductors. Duct seal : The duct seal was immediately ready for use out of the package requiring no additional tools.

9 Being of a clay-like substance, the duct seal could be broken into pieces and placed around and between the conductors relatively easy. In the 12-conductor Conduit , the number of conductors in the Conduit made it more difficult to install the duct seal . A light pull was required to break the seal and remove the conductors. Hazardous Location Sealing Compound: This compound sealant required damming fibers, water, a mixing container, and measuring and stirring devices. The damming fibers were placed into the Conduit seal to create a dam between the conductors and the Conduit seal walls. The sealing compound was measured and mixed per manufacturer s directions. The sealant was then poured into the Conduit seal CCoonndduuiitt SSeeaall EEffffeeccttiivveenneessss 659 Van Meter Street Cincinnati OH 45202-1568 T: 513 241 1230 F: 513 241 1287 Email: Website: and allowed to cure before further testing.

10 The sealing compound was found to be messy, time consuming to install, and difficult to get around and between conductors in the 12-conductor Conduit . The use of a hammer and chisel was needed to free the conductors from the sealing compound. Damage to the conductors was inevitable upon removal. B. Vapor Infiltration Neutral Cure Silicon: The silicone sealant immediately failed all vapor infiltration tests. It showed little or no ability to contain water. Expanding Foam: The expanding foam sealant was able to prevent all water from passing through to the other end of the Conduit body. To analyze the seal , the foam plug was removed and cut into sections to examine the form s ability to surround the conductors. The foam extended 8 -10 into the Conduit and was able to force its way in between and around all the conductors present in the Conduit .