Thermal expansion and contraction of your carrier pipe is widely known and accepted but it rarely comes up in discussion when sizing your modular seal for pipe penetrations. Thermal expansion varies greatly across the different material types that are common in the construction industry today. Examples include; HDPE, carbon Steel (coated and uncoated), ductile iron & PVC. All of which handle temperature changes differently but the common thread through all of them is that they expand and contract when temperatures go up and down. As an example, let’s use the below typical scenario to discuss this topic.
A 16” NPS Carbon Steel pipe with an OD of 16” though a 20” HDPE century line sleeve that is cast in a concrete wall
The annular space would be 2 inches (uniform) when the pipe sees ambient temperatures. But what if the media in the pipe is steam and the carbon steel pipe could see temperatures over 212F? Does this change the OD of the pipe when in service? What about when service is shut off and the line is idle, does the real time OD return to the ambient temp OD?
If you size the modular seal for the ambient temperature OD and fail to consider the expansion and contraction that will result from the media temperature and fluctuation between in service and out of service the possibility of a loss of seal becomes real. The truth is that there is no perfect solution for this problem. The best we can recommend is to put in place a maintenance procedure that includes a review of the seal periodically to ensure it has maintained good contact with carrier pipe and ID of the penetration.
Example Pressure rating
In many, not all, wall penetration seal applications it is critical to ensure a certain level of pressure rating. The minimum PSI rating a modular seal should be able to hold is 20 psi or 42 feet of head with a safety factor of 4x. This allows the flexibility to handle surge scenarios as water levels and pressures are often dynamic. For extremely high pressure applications, it is important to fix a brace to the wall that can provide additional stability to the modular seal. Walk out vs. leak around the seal. In testing, the Link-Seal was shown to not fail a leak test. At high pressures the seal walked out of the wall penetration over time.
- Fastener corrosion - coating and grade of steel - plastic pressure plates to avoid corrosion
- HDPE sleeves w/ waterstop (no corrosion and better sealability) = waterproofing membrane
- Large annular spaces (intermediate sleeve)
- Off center, multi and/or eccentric pipe penetrations
Pre Cast Pipe Penetrations
Whenever possible, pipe penetrations should be sealed with a mechanical seal. New pipe penetrations and existing pipe penetrations can be sealed with either a Link-Seal or a Compakt Seal.