Sealing Pipeline Penetrations
What is a Pipe Penetration?
You have open space/annular space that needs to be sealed when you have a pipe passing through a barrier.
Pipe Penetration Sealing – What are you Sealing Against?
(oil, waste water, etc.)
The key factors to take into account when selecting the right material type for your Link-Seal modular seal are as follows: media (water, oil, etc.), temperature, wall thickness of carrier, and is it above or below ground.
Pipe Penetration – Media
When we say media, we am referring to what the Link-Seal modular seal will be coming into contact with as well as what is running through the carrier pipe. This is important to note as it will play a big factor in determining the proper material for the Link-Seal modular seal. For example, if your carrier or service pipe is transporting diesel fuel into a tank it would be simple because the service media and the tank media are the same and therefore the Link-Seal modular seal will be in constant contact with the diesel fuel in the tank and would require a nitrile Link-Seal modular seal for compatibility reasons.
In the event that the pipe leaks and the media in the pipe (diesel fuel) comes in contact with the nitrile Link-Seal modular seal it will maintain its integrity and continue to seal. In a similar example, the diesel service line is simply passing through an exterior wall of a vault that is buried in the earth. This Link-Seal modular seal will actually just be sealing against dirt and ground water predominantly and the service media (diesel fuel) really isn’t critical to selecting the right product.
In this case, we would recommend using our standard EPDM Link-Seal modular seal with stainless steel fasteners to avoid issues with corrosion in this moist environment. In the event that the service pipe leaks or fails the seal will have little impact on the outcome here which is strictly the opposite in comparison to the previous example. If the primary tank containment fails and the diesel fuel is then directly sitting against the Link-Seal modular seal it is critical to have the nitrile Link-Seal as this will be able to hold up to the diesel fuel and prevent a leak at this tank penetration point.
Why Use Plastic Pressure Plates Instead of Steel or Visa Versa?
When it comes to selecting the right material for the pressure plate component of the modular seal you have chosen, it is critical to understand the benefits and limitations of both steel and plastic pressure plates.
Bund Wall Applications
Due to the special circumstances that are present in bund wall applications it is important to ensure you have the right seal from a performance perspective and a safety perspective. Bund Wall applications required both a hydrocarbon compatible seal and a fire safe rated seal. By combining the nitrile seal and the silicone seal into a single assembly, dual seal, we are able to solve both problems at once. The key is to place the oil seal (nitrile) in contact with the media and the fire safe (silicone) on the open, exterior of the wall. This allows for both materials to function as intended while only requiring your team to perform a single install.
The only limiting factor for the OFS model is the available seating area in the wall penetration. In the event of insufficient seating area, please contact Garlock to consult on a wall mounted sleeve to provide the additional seating area required.
Challenges with Centering the Media Pipe Through the Penetration are Common.
The following challenges are commonly faced when installing a pipe through a wall/floor/ceiling penetration:
- Pipe is not centered in the penetration
- Pipe is angled/deflected through the penetration
- The pipe is skewed to one side of the penetration (up, down, left, right)
- The annular space is not uniform through the penetration
- The precast hole and the pipe don’t line up as planned
- There are multiple pipes that need to pass through the same wall penetration
- The wall is not thick enough to provide the necessary seating area for the modular seal
The list above covers many but not all of the challenges that are faced in the field when installing pipe through penetrations where a water/gas/etc. tight seal is required. With the help of a wall mounted sleeve (std. or split design) you can redefine the annular space to create an ideal sealing environment for your modular seal application.
Thermal Expansion
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.
Example
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.
