Why (CIPP) alternatives are required for pressure piping systems
RestoLine personnel have experience installing over 300 km of gravity and pressure (CIPP) liners throughout Singapore, Hong Kong, Malaysia, and the United States. Having vast experience in trenchless system design and field installations it becomes apparent that no trenchless remediation method is viable for all scenarios encountered in compromised pipeline rehabilitation.
A new inspection initiative nationally adopted by various utility departments show unsettling data related to defects found in (CIPP) installations that are not visible or overlooked by traditional means of CCTV inspection. This method removes operator error and relies on a sensor array that detects electrical flow through any area of exfiltration (Torricelli’s and Ohm’s law), this allows for the identification of the leak location and size (total volume loss per minute).
Data recorded during the electronic inspection of 45 km of installed CIPP liners (2011-2016):
| Inspection for CIPP Certification & Acceptance | Year to Date 7-31-2016 |
Life to Date 2011 -2016 |
|---|---|---|
| CIPP Liners with Defect Flows | 66% | 84% |
| CIPP Liners with ZERO Defect Flow (Leak-Free) | 34% | 16% |
| Defect Flow By Severity | ||
| More than 1 GPM | 55% | 62% |
| More than 2 GPM | 49% | 54% |
| More than 3 GPM | 46% | 51% |
| More than 4 GPM | 45% | 47% |
| More than 5 GPM | 42% | 43% |
| Over 10 GPM Increased Leakage Than Pre-CIPP | 37% | 34% |
| Over 20 GPM Increased Leakage Than Pre-CIPP | 25% | 21% |
Why are CIPP installations with a claimed design life between 50 – 100 years leaking?
Many agencies are changing their specifications to incorporate electronic inspection pre and post rehabilitation when using CIPP. This is mainly due to post CIPP defects (generally resulting in leakages) that are not recognizable with standardized CCTV inspection. The majority of the defects observed post-CIPP occurs from labor related errors throughout the liner preparation and installation process. The charts below highlight the CIPP installation procedure (5 stages), with the potential defects that are most commonly encountered post-cure.
Defect Summary:
| CIPP Installation Procedure | Potential Error | Defective Result | PipeGuard™ Alternative |
|---|---|---|---|
| 1. Jetting to clear debris and clean the internal pipe wall, followed by pre-line cctv inspection. 2. Internal diameter measurements are taken at both ends of the section to be lined (manholes or access pits) 3. Contractor orders CIPP materials, felt tubing is manufactured precisely to fit the host pipes Inner diameter with less than 3% deviation available to accommodate for internal inconsistencies. 4. Note: Aged piping systems that have been subjected to external loadings result in cross-sectional deformation and ovality that exceeds the 3% tolerance of the felt tubing, these defects are commonly not detected with visual inspection and overlooked. |
1. CIPP felt lining is manufactured to fixed dimensions, there is very little error band to compensate for the pipe ovality which often exceeds the felt tubes tolerance. CCTV alone is not capable of determining minor diameter reductions or the extent of ovality, these values are necessary to ensure successful lining installation with CIPP. | 1. When the liner is inverted and attempts to conform to the ID of the host pipe an annulus or void will be created between the OD of the CIPP and the host pipe ID. This will result in ridges and seams that run longitudinally down the liner; these areas become points of failure that are well known to result in leakage and affect effluent transmission. | 1. Robotically installing a PipeGuard™ lining will result in a manufactured to fit, self-supporting continuous polymer lining inside of the existing host pipe with over > 3000 psi adhesion to the substrate. |
| CIPP Installation Procedure | Potential Error | Defective Result | PipeGuard™ Alternative |
|---|---|---|---|
| 1. The felt tube is impregnated with a two part resin system (wet-out) and is delivered to site, (packed in water and ice). 2. Minimal time is left to install the liner; this is due to the thermosetting reaction of resin system saturated through the CIPP liner. |
1. During the wet-out process to impregnate the felt tube there is the potential for bad and poorly mixed resin, emulsification, dry sections and voids. 2. The resin saturated liner can gel beyond an acceptable level prior to inversion. |
1. Resin specific failures are generally not visible until the internal coating and seam sealants erode away, after reinstating the line this would be a point of failure that would lead to leakage during operation. Existing infiltration during the lining process can wash out resin and create uplift which must be robotically cut by milling or (UHP) water blasting. 2. In some cases complete collapse will occur if the lining is not suitable from prolonging the inversion process. In many cases the lining will semi-cure making CIPP liner removal impossible, this leads to either trenches and pipe replacement or days of (UHP) water blasting to remove the CIPP liner. |
1. PipeGuard™ Lining systems are manufactured on-site by a proprietary dispensing system, material properties are programmatically monitored at the lining rig and inside the pipe on the application tooling. The control system eliminates human error from the installation by de-actuation of the tooling in the event of system failure or other anomalies. |
| CIPP Installation Procedure | Potential Error | Defective Result | PipeGuard™ Alternative |
|---|---|---|---|
| 1. After site preparation is completed the on-site personnel are ready to begin the inversion process which is achieved by means of air or water pressure. 2. The lining is inverted; this turns the felt tube inside out forcing the resin impregnated liner through the host pipe. |
1. Piping related constraints consisting of steep gradients, inclines, diameter reduction, inconsistencies and pipe geometry encountered such as bends > 15° 2. External liner damage due to miss-handling during site preparation or as it passes through the inversion assembly. |
1. Encountering these pipeline conditions lead to an un-even distribution of inversion pressure, the result in a non-uniform cure thickness of the liners cross-section. The final cured liner will consist of wrinkling and folds of excess liner material if over-sized; if undersized there will be voids between the liner and host pipe. All defective areas are a potential point of failure resulting in leakage and affect internal flow. 2. Damage to the external liner results in internal defects after inversion (the liner is turned inside out), pinholes, cuts and damage to the surface can create pressure loss scenarios, resin washout, leakage and worst case partial or full collapse. |
1. Robotic PipeGuard™ application equipment has been designed to navigate complex geometries and exceed the lining distance limitations of (CIPP). Internal piping configurations can be easily traversed while maintaining even lining distribution throughout the substrate. |
| CIPP Installation Procedure | Potential Error | Defective Result | PipeGuard™ Alternative |
|---|---|---|---|
| 1. Once the tail section of the lining reaches the end of the lining length, the contractor will accelerate the curing process. 2. Full curing process begins either by circulating steam or hot water throughout the internal CIPP. The cure time is based on diameter, lining length, and total resin volume. 3. Note: In many cases this process is rushed given the mentality of the contractor, their goal is to aim for 2 inversions per day or +- 600 m per week. |
1. Uneven heat distribution throughout the liner during the cure process creates the potential for over or under heating of the lining. 2. Given the nature of the lining, adhesion between the CIPP liner and host pipe is often none or minimal. 3. Pressure loss inside the lining can occur due to liner damage during installation or equipment failure. |
1. If under-cooked there will be inadequately cured sections with in-sufficient structural and mechanical properties; over-cooked and overheated sections will result in boiling points and openings. Both scenarios create points of failure resulting in leakage. 2. If the liner does not properly conform to the substrate with adequate adhesion there is potential for fractures, cracking and partial or full collapse due to negative pressure. 3. If pressure loss occurs during inversion and is not quickly solved this will result in complete collapse or uplift which runs throughout the substrate. |
1. The reaction time of PipeGuard™ linings upon application is roughly 4 seconds, this allows for customized (DFT) build-up of 20 to > 500 mils in one single pass. Each subsequent lining pass required to build the necessary design thickness ultrasonically tests the adhesion and film thickness of the applied lining as the machine navigates the host pipe. |
| CIPP Installation Procedure | Potential Error | Defective Result | PipeGuard™ Alternative |
|---|---|---|---|
| 1. Personnel determine the lining has fully cured, they trim the tail sections behind the liners entry and exit point. 2. Manually controlled robotic cutters enter the host pipe to reinstate lateral connections that were lined through during the inversion process. 3. Top-hats (lateral packers) are then installed to provide termination for the laterals, this prevents lining delamination from occurring due to process effluent permeating the annulus between host pipe and liner that forms after reinstating the laterals. 4. End seals are then installed that overlap the CIPP end and host pipe access, this serves the same purpose as the top-hats (prevent permeation from occurring between host pipe and lining). Unfortunately CIPP end seals do not prevent effluent penetration and crevice corrosion from occurring at the termination or connection points. |
1. Manually cutting out the CIPP lined through laterals can lead to improper service re-connections and unintentional liner cuts. 2. Top-Hat installation requires immense worker skill; this process has limited success and often ends with a faulty installation not detectable with CCTV inspection alone. 3. End-Seal lining termination for the CIPP liners do not address the installation requirements necessary for pressure piping applications. |
1. Unintentional liner cuts or inadequate opening of laterals will become points of leakage. 2. Improper top-hat installation into branches and connections will often not be noticeable during cctv inspections, these also result in a potential point of leakage. 3. The existing design of end-seal terminations for CIPP liners will absolutely have effluent penetration at the connections which lead to crevice and stress corrosion; long term, all flow facing terminations will become points of failure resulting in leakage. |
1. The spray applied PipeGuard™ lining will feather into the connected sections without compromising the pipes flow, this eliminates the necessity for connection reinstatement with manually controlled robotic cutters and top-hat installations for termination. 2. RestoLine has multiple customized end-seal configurations that are used for various flange and field connections after the lining process. Our end-seal design prevents any type of penetration at the flange face that would result in crevice corrosion or further deterioration. |
CIPP Liner Design and Testing Comparison:
The nature of the resin systems used with CIPP average high creep values. To compensate for high creep, adjustments are made to the formulation that increase the mechanical properties of the cured system. Typically this is accomplished by adding fillers which also reduce the shrinkage during the cure process. The necessity for the added structural strength is to decrease the CIPP lining thickness per design calculation, minimizing the final ID. The fully cured CIPP liner has high structural properties with very low ductility.
PipeGuard™ polymeric linings have low creep values and maintain increased ductility and elongation. Compared to CIPP these values allow for a reduced lining thickness, increased abrasion and chemical resistance, prohibit cracking and fractures due to deflection and loading.
The CIPP sample plate preparation methods used for 3rd party testing are not an exact representation of the liner installed inside the host pipe. It’s very common knowledge that the CIPP curing process used on-site produces a structurally subpar lining compared to lab constructed samples that are issued for testing. These samples consist of rectangular felt sections that are wet-out in ideal conditions then cured in lab conditions, this process is required to produce a sample for testing that will meet the tender spec.
RestoLine’s robotically installed PipeGuard™ lining system eliminates the necessity for a pro-longed “ideal” cure. This allows for sample plates to be taken directly from the host pipe after the liner installation, documented then submitted for 3rd party QA/QC testing.
