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Field Test of the Curing Monitoring System in synthetic CIPP Liners

BERGISCH GLADBACH/GERMANY, August 12, 2014 - The Curing Monitoring System (CMS)  is an innovative temperature measurement technique for the cured-in-place pipe (CIPP) in trenchless sewer rehabilitation. In contrast to the common used selective temperature measurement in the manhole area, the CMS is measuring the temperature without gaps as a local temperature profile in the longitudinal direction of the position second by second from the start until the end of the rehabilitation measure.

This in-situ measurement enables an event oriented process management with the advantages for the installation companies and the customers to measure the thermal curing process during the manufacturing of the liner and to keep it as a quality record.

The measurement system is applicable as well for liners with thermal curing as for liners with UV curing. In case of UV curing, the information on the temperature development in the laminate and the position of the light chain is of utmost importance for the decision on the drawing speed.

The temperature measurement system is composed of a controller, an optical measurement cable (sensor cable) and a powerful application software. The sensor cable is generally drawn into the sewer in advance to the liner and connected to the controller via an optical plug connection. The measured temperature data are evaluated and visualized by the software.

Figure 1 shows a schematic overview of the local zone view and the thermograph view as a 3D plot (temperature as a function of place and time).

measurement of the thermal liner curing as local zone view and as thermograph 3D plot

 Figure 1: Measurement of the thermal liner curing as local zone view and as thermograph  3D plot (temperature as function of place and time)

The sensor cable is conceived in order to be drawn directly from the cable drum into the duct. The sensor cable is delivered in lengths of 1950m (6400ft) as to serve for approximately 40 rehabilitation measures per drum. The sensor cable is prefabricated and delivered with an optical plug to enable a quick and easy connection to the CMS controller onsite.  At the flange of the drum a (blue) socket (see figure 2) is mounted to which a robust connection cable (not shown) can be fixed so that the complete measurement system is ready for use in only a few steps.

CMS system - controller and sensor cable

Figure 2: CMS system – controller and sensor cable (drum with optical box)

The company OSSCAD is selling the CMS temperature measurement technique worldwide to manufacturers of needle-felt liners and fibre-glass reinforced GFK liners, installation companies and municipalities. The CMS procedure has been successfully used in Europe, the United States, South America and Australia in more than 1800 positions with more than 200km buried sensor cable length. The first field test was done in November 2007 at an urban drainage company in Cologne in cooperation with IKT, Institute for Underground Infrastructure [1], [2]. The positive acceptance has confirmed our efforts to further develop and get in place the CMS technique as measurement procedure for the CIPP rehabilitation of sewers [3], [4], [5]. To do this, it is important for us to pick up the field experiences and the suggestions for improvements from our customers in order to integrate them into the future developments of the CMS products.

Field tests with the market leader of CIPP rehabilitations

The needle-felt liners are sewn into the sewer by inversion. Before doing so, a so-called pre-liner is drawn into the sewer. The pre-liner facilitates the inversion, protects the liner material with regard to sharp edges and impedes a penetration of the resin-impregnated liner material into the environment. After the feeding of the sensor cable into the sole area, the pre-liner is positioned with compressed air (approx. 0,3bar) and the inversion is started. After that the curing starts. Decisively for a professional curing is the achievement of the so-called least temperature. The least temperature is necessary to push the exothermal reactions in the resin-impregnated liner material and to start the curing process. That is why traditionally thermo elements are positioned in-between pre-liner and outer sheath of the liner.

CIPP rehabilitation with compressed air curing

Figure 3: CIPP rehabilitation with compressed air curing (field-test)

The temperature values of the CMS controller are shown per software as RGB colours in form of a 3D plot (temperature as a function of place and time). Figure 4 shows the timely temperature course of selected liner places (left graph) as well as the current local temperature course in the sole area along the position.

3D-plot of the pre-heating phase of the liner3D-plot of the measurement interval from the heating phase to the cooling down phase

Figure 4:  3D-plot of two measurement intervals (picture on top: pre-heating phase of the liner, picture below: from the heating phase to the cooling down phase).

Figure 4 shows the three curing phases (pre-heating phase, heating phase and cooling-down phase) of the steam process in the timely temperature courses of the 3D plot. The entrance manhole A and the exit manhole B are located at the particular end of the temperature profile. The distance between both manholes is of approx. 46m length. Single liner places along the local temperature profile can be selected by means of markers and the corresponding timely temperature course can be shown as graph. A homogenous curing of the liner shows a regular local temperature course with a constant RGB colour.

The 3D plot shows two thermal incidents along the position. In 26m distance of the local temperature profile a cold spot is visible and at the end of the position a sink is detected over a length of approx. 5m. The comparison of the 3D plots in figure 4 shows that condensate is growing with increasing steam curing in direction of the manhole A. The CMS measurement confirms that despite the thermal incidents a very homogenous thermal curing along the total length of the liner has been reached. The minimum temperature of 58° has been reached during the curing period at all liner places.

The 3D-plot can therefore be used as quality proof for a professional liner curing and for a successfully CIPP rehabilitation.

The installer (operator) expects clear decision support if the pre-set least temperature along the position given by the liner manufacturer will be reached or if the warmth input has to be readjusted. To make this decision according to the demand, the zone view has been developed. The position is therefore split in equidistant local zones. The temperature data are assigned to the relevant zones, are evaluated and marked in terms of colour. The smallest possible zone (subzone) is 15cm. The reference values for the switching of the zones have to be put into the CMS measuring system by the installer when starting it. The reference values are set in relation to the current curing temperature of the single liner zones. Figure 5a shows the zone view with main- and subzones related to the thermal incidents mentioned above. The operator recognises in the zone view that ORANGE zones are given and that the steam input has therefore to be continued. In the zone view of figure 5b all zone colours are set on GREEN so that the operator can be visually informed about the fact that the least temperatures have been reached at all liner places.
This means that the rehabilitation measure can be successfully completed even if there are (unforeseen) thermal incidents. In case the least temperature is reached sooner than expected, the commonly used security impact can be reduced and the duration of the warmth input is shortened. That way, energy cost and CO2 emissions can be reduced significantly.

main zones and sub zones before reaching the last temperature in the area of the cold spot and the sink

Figure 5a: Main zones and sub zones before reaching the least temperature in the area of the cold spot and the sink

main zones and sub zones after reaching the last termperature in the area of the sink

Figure 5b: Main zones and sub zones after reaching the least temperature in the area of the sink

By means of the so-called curing view an additional visualisation tool has been developed which takes into consideration the criterion of the warmth input. In order to judge the thermal curing, the manufacturer can additionally take into consideration the exposure time of the temperature at the liner places by saving the timely temperature history of the single liner places.

Figure 6 shows the curing view. The red graph shows the operator the local course of the maximum reached temperature and the black graph represents the current temperature at the outer layer along the liner. For the calculation of the warmth input, only temperature values above a freely-to-configure (horizontal, orange line) temperature threshold, multiplied with the timely exposure are taken over. The green area shows the exposure time (left scale) as a result of the warmth entry related to the single liner places.

The curing views of figure 6a and 6b show the corresponding measured temperature data related to the zone views here above. The temperature threshold is configurable and corresponds at this liner project to a least temperature of 58°C. The two thermal incidences due to the cold spot and the condensate in the area of the sink are clearly locally distinguishable. The thermal incidences withdraw warmth from the steam process so that the warmth entry is smaller (smaller green area.)

The curing view has – as the 3D plot and the zone view – an animation function showing the measured data timely one after the other in order to display again different states of the curing process.

The curing view provides – as it does the 3D plot – a quality proof for the professional curing of the liner.

curing view before the reaching of the least temperature in the area of the cold spot and the sink

Figure 6a: Curing view before the reaching of the least temperature in the area  of the cold spot and the sink

Curing view after having reached the least temperature in the area of the cold spot and the sink

Figure 6b: Curing view after having reached the least temperature in the area of the cold spot and the sink

Verification of the mechanical liner properties

As a result of the different dimensions and constructions of the tube liners as well as the different damages of the old ducts, the sensor cable has to cover a big scope regarding the mechanical effects.

In order to fulfil those mutual demands, the company OSSCAD has developed – aside the FlatTemp standard sensor cable (dimension 3mmx6mm) – the so-called UltraFlatTemp sensor cable with a cable size of 1,5mm and a width of 6mm. Moreover the so-called FlatTempPlus sensor cable with a cross-sectional profile of 3,2mm x 7,6mm has been newly developed (see figure 7). For smaller liner diameter and smaller wall thicknesses the UltraFlatTemp sensor cable is used and for big liner diameters > DN 1500 the FlatTempPlus sensor cable is appropriate.

CMS sensor cables (UltraFlatTemp, FlatTemp and FlatTempPlus)

Figure 7: CMS sensor cables (UltraFlatTemp, FlatTemp and FlatTempPlus)

The mechanical parameters have been determined by means of the three-point bending test (see figure 8). The results in the laboratory show that there is no impact on the E-module by the obstruction of the sensor cable at the outer side of the liner.

Determination of the mechanical properties in the three-point bending test

Figure 8: Determination of the mechanical properties in the three-point bending test [6]

Summary and Outlook

The field tests of the Curing Monitoring Systems (CMS) have been successfully finished within the scope of the curing of synthetic CIPP liners. By means of the CMS application software thermal irregularities can be clearly detected. The 3D plot and the curing view provide a quality proof for a professional rehabilitation. The use of the zone view gives the manufacturer clear decision criteria – also in case of difficult measures and in case of sites with unforeseen thermal incidents during the rehabilitation measure.  

Summing-up it can be stated that the CMS is characterized by a simple use, robust system components and a powerful software that offers a high potential for innovations:
• Monitoring of the thermal curing process in the longitudinal direction of the liner during the rehabilitation measure
• Colour-coding of the required and achieved least temperature and the demanded timely warmth entry of the liner and therefore unique decision support for the installer
• Quality proof of the thermal curing process over the entire length of the liner and the total duration of the rehabilitation measure

It is scheduled that in a next step the system will be enlarged for the curing with warm water and for the UV curing. Focus is laid on the thermal measurement of the curing in case of warm water curing of synthetic fibre liners and on the examination of the drawing speed in light curing GRP (glass reinforced plastics) liners.

References and indication of sources

[1] Bosseler , B., Abnahme von Liningmaßnahmen - Materialnachweise und Bewertung der Linerqualität, IKT Institutes für Unterirdische Infrastruktur, BMBF Abschlussbericht, March 2009
[2] Diburg, B., Bosseler, B., Glombitza, U., Temperaturmessung bei Kanalsanierungen unter Einsatz von Schlauchlinerverfahren, Praxisanwendung bei einem warmwasserhärtenden Nadelfilzliner in Recklinghausen, bi UmweltBau, Kongressausgabe Deutscher Schlauchlinertag, Pforzheim, April 2009
[3] Glombitza, U., Behlau, M., A new temperature measuring set-up to control the lining curing during the sewer renovation, International No-Dig 2011, 29th International Conference and Exhibition, Berlin, 2-5 May 2011
[4] Glombitza, U., Fiber Optic Cure Verification (FCV) Ensures Quality, Longevity of CIPP Liner Installations, North American Society for Trenchless Technology (NASTT), No-Dig Show 2012 Nashville, TN March 11-15, 2012
[5] Glombitza, U. Curing Monitoring System zur Verbesserung der Prozessführung bei der Kanalsanierung mittels Schlauchlinern, DWA Kanalisationstage, Dortmund, Deutschland, Dezember 2012
[6] Website to the picture:

Ulrich Glombitza