Installation time ranges from almost immediate "plug and play" quick socket fusion to multiple hours of on-site welding, depending on the system. When installing a pipe system, it is important to plan for and include leak-detection, inspection, and pressure-testing procedures. The keys to making the right decisions and lowering project risk are:
The automatic leak-detection and reporting system can be located between the inner and outer pipe and at the lowest point of the system. Leaks can also be detected and observed through multiple inspection ports located at the lowest level of the pipe system or at a collection double-containment sump. Because electronic systems can fail, to be truly proactive and safe any system design should include frequent visual inspections for leaks as mandated by toxic substance control regulations.
A complete visual pipe inspection for both carrier and containment systems should be performed before pressure testing, including welds, joints, cracks, and slopes. Once the visual inspection has been completed, a pressure test can be conducted as follows:
Once the carrier pipe is installed, it is essential to certify the pipe and to confirm that it can handle the design pressure. For a gravity-flow system, most plumbing codes require a 1/8 inch per foot slope and a working head pressure test for 15 minutes. Other systems may require that the system be certified at a higher pressure rating; this will allow more flexibility for future pipe inspections with higher-pressure media, especially when a suspected leak cannot be located with a borescope. Choosing the correct pipe material will determine the system’s ability to handle higher pressure testing.
When the carrier pipe has passed both the pressure test and an inspection by a certified professional, the containment pipe can be closed and tested. Usually, this requires a lower pressure rating test than the carrier pipe. In some systems, the containment pipe is tested when the carrier pipe is charged.
In general, inspections and testing can be progressive or sectional. This is determined at various project phases.
Underground and aboveground containment piping systems both have pros and cons.
Pro: In some applications, underground fluid-transfer systems rely on gravity flow, avoiding pump and installation costs.
Con: Underground double-walled containment piping in an elongated system can hide a slow leak for a long time before it finds its way to the end or lowest point of the piping system. Pinpointing a particularly small leak’s location can be a challenge, especially when it’s not detectable via a borescope inspection. Additionally, false alarms can occur when an automatic leak-detection system can’t differentiate between a dangerous toxic leak and harmless condensation between the inner and outer pipes. Frequent manual inspection and testing can preclude these false readings, averting unnecessary stress and expense.
Pro: Aboveground systems make leak detection simpler, if only because manual observation is straightforward. An inspection leg with a sampling port can be added to the pipe system to collect fluid leaking from the containment system. Additionally, the containment pipe in a polypropylene system can be clear polypropylene; stainless steel pipe can include a dead leg to check for carrier pipe leaks.
Con: A toxic leak in an aboveground system—especially above a building complex—can enter the public water system through a roof drain or site water runoff. Precautions such as a secondary containment pipe or containment pit may be required to prevent accidental damage to the physical plant and mitigate danger to employees.
Bashar Madani, PE, is Vice President and Director of Engineering at Advanced Professional Engineering Consultants, Inc., where he manages operational aspects of complex projects from initial analyses to completion and commissioning. Madani earned a BS in mechanical engineering and an MS in engineering management from California State University, Long Beach, and has 25 years’ experience as a licensed professional and commissioning manager in pharmaceutical, commercial, and industrial sectors.
He has been a chair and speaker at the facility design, upgrade, and expansion conference at the Pharmaceutical and Biotechnology Middle East conference in Dubai, as well as a member of the American Society of Heating, Refrigerating and Air-Conditioning Engineers guideline 62.1 committee, the American Society of Mechanical Engineers, the National Society of Professional Engineers, the National Fluid Power Association, and the US Green Building Council. He has been an ISPE member since 2006.