Indian Oil Corporation Ltd., chose 100% Solids Polyurethane Coatings to rehabilitate approx. 2 X 7.5 Kms of 24” Dia Chaksu – Mathura Section of the Salaya Mathura Pipeline. 100% Solids Polyurethane Coatings are the international coating of choice for Pipeline Rehabilitation and covered under NACE International, USA Technical Committee Report,Task Group T-10D-17/T-6A-63, dated July 1999 "Coatings for Repair and Rehabilitation of the External Coatings of Buried Steel Pipelines".
Survey had indicated that the Coal Tar Enamel coating had deteriorated and was in urgent need of rehabilitation. Rehabilitation work was awarded to two companies; M/s Shree Ambha Associates and M/s Jay Gauri Projects. Both companies are long standing contractors of IOCL for pipeline rehabilitation works. Shree Ambha Associates and Jay Gauri selected Purethane, 100% Solids Polyurethane Coatings for the project and in Sept.-Oct. 2008 awarded the supply orders to Amchem. Despite having extensive experience of applying Tape coatings, both companies were new to 100% Solids Polyurethane Coatings. Amchem arranged for supply of the Graco equipment and training of crews of both companies in line with tender requirements. Further, Amchem deployed a skilled applicator at both sites 24X7 to ensure proper application as per written standards. (All pictures of this newsletter are from Shree Ambha Site).
The pipeline was excavated and earth supports retained at approx. 8m intervals to avoid disruption in operation. The deteriorated coating was scraped manually from the pipeline and surface blast cleaned to SSPC SP-10 with 75+ Microns Anchor Profile using Granulated Copper Slag (single use). Blast cleaned pipe was primed with Purethane AR Primer to approx. 25-40 Microns DFT. Primer enhances adhesion, overcomes minor surface preparation deficiencies and provides long (48 hour) “window period” for coating.
Touch dry primed pipes were coated with 1,250 Microns nominal thickness of Purethane®, 100% Solids Polyurethane Coating using state of the art plural component airless spray equipment from Graco Inc., USA. The coating sets in minutes and cures quickly. A single medium spray tip can spray about 120 Litre/ Hour or about 60 RM (running metre) / Hour of 24” Dia pipeline. The Graco equipment can support multiple tips (upto 5)
The applied coating is seamless, very strongly adhered to the surface, extremely tough and has very high electrical resistance. There are no “tenting” or air gaps over weld seams as in case of Tapes. Purethane® can operate at 90° C continuous & 121° C intermittent. Cold applied tapes however can only be used up to 49° C and are likely to sag in hot climates like India. Further the cold tapes are prone to soil stress damage. Purethane® on the other hand has excellent adhesion and can withstand soil stress.
The coating specifications were very detailed and comprehensively made by IOCL. A detailed QA/QC procedure was drawn in accordance with the specification. Daily log sheets were kept for Blast Cleaning, Priming, Coating & Testing. Tests were regularly kept for ambient temperature, surface temperature and dew point. This was done to ensure that the surface temperature always exceeded the dew point by at least 3° C. The following field tests were carried out on the installed coating :
- Dry Film Thickness (DFT) using digital magnetic mil gauge as per SSPC PA 2. Spot variation of up to 1,125 Microns was permitted.
- Holiday test as per NACE International RP 0188-90. Any holidays detected were repaired manually and a complete holiday free coating was provided. Repairs are very easy with the Purethane® systems and practically indistinguishable from the spray applied materials.
- Adhesion Test as per ASTM D 4541 using Positest AT Digitial gauge. A minimum of 1,500 Psi (10,350 KPa) was specified.
The testing was conducted by M/s IRS. Senior officials of IOCL including Executive Director, Western Region visited the site to see the coating works personally. We thank IOCL for the opportunity provided to demonstrate the effectiveness of Purethane® in pipeline rehabilitation.The entire project was complete by end March 09.
Purethane® coatings greatly helped in reducing the cathodic protection current required to achieve protective potential (PSP) which can be seen from following data :
|CP Station Location Chainage||DC Current Volts Sept. 08||DC Current Volts Sept. 09||Current Amps Sept. 08||Current Amps Sept. 09|
|682.17 Kms||42.50 V||4.00 V||19.00 A||1.62 A|
|689.94 Kms||28.20 V||4.14 V||36.00 A||2.00 A|
|700.31 Kms||25.80 V||3.10 V||10.50 A||1.40 A|
Current density now required to achieve PSP is only 0.083 mA/Sq. M which will lead to big cost savings and enhancement of life of the pipeline.
Upon completion of the project the contractors gave big thumbs up to the system. Mr. Sankaran, Chief Executive of Shree Ambha Associates stated :
“Taking into consideration of various aspects such as costing, ease of application, storage, good adhesion strength, good toughness, good impact resistance, we strongly feel that PU Coating with your product, is a step ahead in comparison to other products used for Pipeline Rehabilitation works.”
Mr. Brij Gupta, Managing Director of Jay Gauri Projects (I) Pvt. Ltd stated :
“After applying Purethane Coating on SMPL, we would rate it to be the best solution compared to other types of coating / tapes…. Overall we were very much satisfied with the application of the PU coating and expect a good improvement in the PSP readings. We would prefer to apply this coating in future on cross country pipelines.”
Presently (end 2011), pipeline rehabilitation is ongoing by Amchem’s licensed applicators at several locations for IOCL. Due to its excellent performance, the coating is slated to completely replace traditional Hot and Cold applied Tapes.
Amchem Products Pvt. Ltd
A-79. Sector 58, NOIDA 201 301, India
Tel : 0120 - 2580121 / 4325540
Fax: 0120 - 2581351
E-Mail : firstname.lastname@example.org
Website : www.amchemproducts.com