18 TH INTERNATIONAL CONFERENCE ON COMPOSITE MATERIALS OVERWRAP COMPOSITE REPAIRS OF OFFSHORE RISERS AT TOPSIDE AND SPLASH ZONE A.Y.L. Leong 1 , K.H. Leong 1, *, Y.C. Tan 1 , P.F.M. Liew 2 , C.D. Wood, W. Tian 3 & K.A. Kozielski 3 1 PETRONAS Research, Lot 3288/3289 Off Jalan Ayer Itam, 43000 Kajang, Selangor, MALAYSIA. 2 PETRONAS Carigali Sdn Bhd, Sarawak Operations, Jalan Sekolah, 98100 Lutong, Sarawak, MALAYSIA. 3 CSIRO, Bayview Avenue, Bag 10, Clayton, VIC 3169, AUSTRALIA. * Corresponding author (kh_leong@petronas.com.my) Keywords : overwrap repair, wet and dry conditions, offshore, riser, pipeline 1 Introduction fully or partially restore the pressure capacity of a corroded or ruptured pipe, with the added corrosion This paper describes the work carried out to protection benefit [4]. Good adhesion between the develop, test and field-demonstrate a polymer resin composite repair and the corroded substrate is composite overwrap system capable for use in the essential for effective load transfer between the pipe repair and/or corrosion protection of pipelines and and the composite overwrap. It is also important risers in the oil and gas industry. The system is that the adhesion is sufficiently good to prevent the designed to be applicable in dry conditions, e.g. for ingress of water into the repair-substrate interface. pipelines and sections of risers at and close to the This requires the cleaning and profiling of the platform; in wet conditions, e.g. risers at the splash substrate surface prior to bonding of the composite zones; and in fully submerged underwater wrap. On onshore dry applications, abrasive conditions, e.g. for subsea pipelines. It is also the blasting is commonly used, but for underwater intention of this research to develop a system that applications, other methods such as sub-aquabrade can be used in hot service conditions of up to has been reported to be much more effective [5]. approximately 100°C. Hence, based on ISO 24817 † , Sen et al. [6] reported a repair undertaken on to which the resin system is developed and qualified, partially submerged corrosion damaged concrete it is necessary that a minimum glass transition piles with both glass and carbon fibre reinforced temperature (T g ) of 130°C is achieved. composites, and hydraulic power tools were shown to be effective for removing marine growth and 1.1 Overwrap repair surface cleaning. Fibre reinforced polymer (FRP) composites Early thermosetting systems can only be have high specific strength and stiffness. Combined applied on dry surface and is adversely affected by with their corrosion resistance, it makes them an moisture and surface contaminants. Two chemical attractive material choice for weight sensitive types generally used for pipeline repair are epoxy structures in environment of high atmospheric and polyurethane (PU) resins [7,8]. PUs have the corrosivity. Bonded FRP repairs have been widely advantage of curing at ambient temperatures via used in retrofitting of civil concrete structures but moisture activation, but the downside is that they are their application to offshore steel structures is hydrolysed relatively easily in water and they have limited due to a lack of long-term performance relatively low T g values. In contrast, epoxy resins database for life prediction [1,2]. Offshore are more moisture stable and can be formulated to platforms are essentially civil structures, albeit provide high T g and environmental stability using operating in a harsher environment. The important aromatic amino compounds [9]. physical and in-service properties of thermosetting polymer composites for civil application have been 2 Experimental – From Laboratory to Field reported by Hollaway [3]. In the current research, epoxy-amine systems Engineered FRP or composite overwrap repair, were formulated and, in the initial stages, screened which can be applied in-situ without hot work, can based on their (i) ability to cure underwater; (ii) pot life; (iii) T g ; and (iv) adhesion to steel. † ISO/TS 24817:2006 Petroleum, petrochemical and natural gas Once optimised, the resin formulation was industries -- Composite repairs for pipework -- Qualification and design, blended in scaled-up batches of 20kg in a jacketed installation, testing and inspection
re eaction vesse el. The resin n was then p pre-impregna ated 2.2 2 Prepreggin ng in nto a chopp ped strand mat (CSM) ) backed pl lain The resin n was pre-im mpregnated into a wove en w woven E-gl lass fabric. The p pre-impregna ated E- glass fabric c with a th hin chopped d strand m mat (p prepreg) tap es were used d to produce e specimens for bac cking using g a comm mercial pre- -impregnatio on m mechanical, corrosion an nd thermal c characterisat tion ma achine equip pped with a (modified d) resin bath h, a and testing. he ating statio ons and a fabric tak ke-up system m In add dition to materials testing a and (se ee Fig. 1). A After an ini itial process optimisatio n, characterisati c ion, this rese earch also de emonstrated the res sin content o of 50wt% w as achieved resulting in a effectiveness e of the ne ewly develo oped overw wrap no minal tape w weight of 46 60g per linea al metre. Th he re epair system m in the field d. The field demonstratio ons pre e-impregnate ed 300-mm w wide tapes (p prepreg) wer re h have been pla anned to prog gress in stag ges; from dry y, to sea aled in alum minised bag gs and kept t at sub-zer ro wet/splash z w zone and fi inally to fu ully submerg ged tem mperatures b before they ar re delivered to site. a applications. Only the dry y and splash h zone corros sion p protection fie eld demonstr rations are r reported in t this paper. p 2.1 Resin che 2 emistries The com mposite requ uirements de escribed in the in ntroduction preclude the use of uretha ane fo formulations and simp ple epoxy/al liphatic am mine s ystems that are generally y unsuitable due to their r T g c constraints and/or rel latively po oor durabil lity. Therefore, a T a new chem mical appro oach has be een Fig. 1. Prepr regging of cho opped strand m mat (CSM) in nvestigated t together with h an active a aromatic am mine backed wo oven tape. as a hardene a r to provide e high T g an nd adequate pot li ife. Modera ately reactive e aromatic ha ardener (E 1 00) testing 2.3 3 Character risation and w was utilised with a mix ture of less soluble epo oxy Differenti ial Scanning g Calorimetr ry (DSC) an nd re esins such a s a high mol lecular weigh ht di-functio onal Dy ynamic Mec chanical Th hermal Anal lysis (DMTA A) s olid epoxy (DER 662) and a stand dard diglyci idyl we ere used t to evaluate e the perc centage cur re ethyl bisphen e nol A (DGEB BA) liquid re esin (DER 33 31). con nversion and d to determin ne the resulti ing T g of bot th Nanoclay w N was added f for viscosity y modificat tion the e neat resin n matrix ma aterial and t the composi te w whilst a silan ne cure prom moter was u used to enhan nce ma aterial. re esin adhesion n strength to o wet steel su ubstrate [10]. Coupon t testing were e conducted based on te est A com mposite imp regnation r resin and t two sta andards spec cified in the e ISO 24817 7. The test ts, v versions of p primer resin n, one for dr ry and one for wh hich cover te ensile, shear and lap she ear evaluation n, w wet/submerge ed applicatio on, were sele ected for furt ther we ere carried ou ut on lamina ates that wer re either cure ed development d and testing. . The comp posite resin w was in air or in artificial se eawater, i.e. . under full ly formulated fo fo or factory pre e-impregnati ion into E-gl lass sub bmerged co onditions, to o simulate its intende ed fabrics and h fa has an ambie ent pot life o of about 3 da ays, op erational env vironments. whereas the w primers w were formula ated as 2-p part Hydrostat tic test pi ipe specim mens with a epoxies with e h a pot life of 45 - 90 minutes. T The ma achined 80% % wall thinnin ng defect, pe er ISO 2481 7, p primer is applied im mmediately after surf face An nnex C, and d a through wall (hole e) defect, p er preparation o p of the substra ate to protect t it against fl ash ISO O 24817, An nnex D, were e also prepar red and teste ed ru usting whilst t at the same e time filling g up any surf face in this research h, but only se elected result ts are reporte ed d defects and d displacing wa ater, thereby ensuring be tter in this paper. c contact betw ween the com mposite ove erwrap and the Salt spra ay tests w ere carried out as p er s teel substrate e, in this cas e the riser. AS STM B117 ( (unscribed) t o evaluate th he efficacy o of the e overwraps s to rehabil litate damag ged and age ed cor rrosion prote ection coatin ngs. The sp pecimens wer re
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