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GRP better than steel for offshore pipes
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GRP better than steel for offshore pipes A m o c o N o r w a y Oil C o m p a n y b e l i e v e s t h a t r e p l a c i n g s t e e l p i p i n g with GRP w i l l i m p r o v e the availability o f d e l u g e f i r e w a t e r s y s t e m s o n t h e N o r t h S e a oil p l a t f o r m s o f the Valhall field. A m o c o ' s S. W. Ciaraldi, J.D. Alkire and G.G. H u n t o o n d e s c r i b e t h e r e s u l t s o f the c o m p a n y ' s t e s t p r o g r a m m e to verify t h e suitability o f GRP for this a p p l i c a t i o n .
moco Norway Oil Company recently reviewed the Valhall firewater System with the goal of improving System reliability to 100%. The company estimated t h a t the use of glass reinforced plastic (GRP) piping components, which are essentially TABLE 1: Relative comparison of Valhall i m m u n e to s e a wat er corrosion, was the dry deluge firewater most cost-effective approach (Table 1).
A
system options. Option :
Installed cost relatiyeto insulatedGRP
Comments : :: ::
:
: :
: : :: : : :
Replace with insulated GRP
1.0
Preferred option
Maintain steel with high pressure water flushing
1.9
2 year retreatment rate. 1990 cost over field life. Assumes no replacements. Inadequate reliability.
Maintain steel with acid cleaning and wax coating
2.3
3 year retreatment rate, 1990 cost over field life. Assumes no replacements. Inadequate reliability,
Replace with carbon steel
1.1
Inadequate reliability. Maintenance not included.
Replace witlq cupronickel
1.6
May not last for field life. Reliability unknown.
Replace with titanium
1.2
Optimistic estimate, Reliability unknown.
Replace with 6% Mo stainless
1.5
Replace with super dupJex stainlesg
1.7
REINFORCED PLASTICS DECEMBER 1992
Deluge firewater systems are used in the wellhead and process areas of offshore oil pl at form s. For o p e r a t i o n a l reasons, t h e majority of piping in these types of systems does not contain water. Spray nozzles and sprinkler heads are left open. On detection of a fire or a high gas level, a deluge valve opens t hat allows large am ount s of water from a pressurized wet system to flood into the dry piping. A typical oil platform will have many kilometres of dry deluge firewater piping t hat is traditionally made of carbon steels. Dry piping sizes are predominantly less than 200 mm diameter, with most being less th a n 50 ram. Because the systems often use seawater and are continuously exposed to the hostile offshore environment, internal corrosion is common. This leads not only to loss of wall thickness, but to blocking of spray nozzles and sprinkler heads by corrosion products and scales. Amoco n o t i c e d t h a t every two y e a r s s i g n i f i c a n t blocking of s p r i n k l e r h e a d s occurs in the deluge systems on its platforms in the Valhall field. Incomplete draining of the system internally exposed the del uge p i p i n g to o x y g e n a t e d seawater. Several extensive and costly system cleanouts have been required to maintain operat i onal status. F u r t h e r reliability of th e syst em s was r e g a r d e d as q u e s t i o n a b l e , despite the m ai nt enance efforts. Amoco established a dialogue with the Norwegian Petroleum Directorate (NPD) to discuss the use of non-metallic materials for offshore safety systems, a practice restricted by existing regulations. Three fundamental tasks were identified as necessary to justify the use of GRP firewater Systems from a safety viewpoint: • a risk a s s e s s m e n t s t u d y to establish function and acceptance criteria; • a fire survivability verification test programme; and • detailed specifications and quality assurance Systems. A p r o j e c t s p o n s o r e d by oil c o m p a n i e s Amoco, Conoco, Shell and Statoil formu-
0034-3617/92/$3.50 ~, 1992, Elsevier Science Publishers Ltd.
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l a t e d a p l a n to a d d r e s s t h e s e tasks. The p r o j e c t r e s u l t e d in successful safety justification of GRP d r y f i r e w a t e r s y s t e m s a n d NPD c o n s e n t for use of t h e s e m a t e r i a l s for t h e dry deluge s y s t e m s at Valhall.
Risk assessment study The NPD h a s for m a n y y e a r s p r o m o t e d risk a s s e s s m e n t s t u d i e s as t o o l s to i m p r o v e offshore safe.ty (1). The a p p r o a c h w s t e m atically establishes performance criteria, then evaluates performance under accident e v e n t s such as e x p l o s i o n s a n d fires. T h e f u n c t i o n c r i t e r i o n for t h e Valhall firewater system stated that the system pedbrmance should reduce heat radiation levels so t h a t p e r s o n n e l e v a c u a t i o n or e s c a p e is p o s s i b l e u n d e r c e r t a i n a c c i d e n t s c e n a r i o s (2). The time needed lbr escape and e v a c u a t i o n w a s e s t i m a t e d to be 20 m i n u t e s . A s e c o n d a r y f u n c t i o n criterion c o n c e r n i n g p r o t e c t i o n of t h e facilities e s t i m a t e d t h a t a t i m e of 80 m i n u t e s w a s n e e d e d . T h i s i n c l u d e d t h e m a x i m u m d u r a t i o n of a fire event at Valhall u n d e r a s s e s s e d risk criteria. The four m a i n a c c i d e n t c o n s i d e r e d w e r e t h o s e of e x p l o s i o n s , fires, i m p a c t d a m a g e a n d h m g - t e r m durability. The last two w e r e e v a l u a t e d with r e s p e c t to p e r f o r m a n c e in e x p l o s i o n s a n d fires. B e c a u s e of e p o x y resin's good-high temperature properties a n d b e c a u s e of t h e g r e a t e x p e r i e n c e in using e p o x y GRP, only t h e s e m a t e r i a l s w e r e e v a l u a t e d in t h e study. Using a c c e p t e d t h e o r i e s a n d m o d e l s t h e design e x p l o s i o n p r e s s u r e at Valhall was calculated, e x p l o s i o n s having a frequencT of 1 in 10 l)00 y e a r s . S u p p o r t s e p a r a t i o n d i s t a n c e s lbr GRt' p i p i n g m u s t be d e s i g n e d so t h a t d r a g tbrces f r o m this e x p l o s i o n p r e s s u r e will not seriously d a m a g e p i p i n g or p r o t e c t i v e fire insulation. A h i g h - p r e s s u r e gas fire, or .jet fire, a f t e r an e x p l o s i o n w a s c o n s i d e r e d as t h e w o r s t case event. GRP p i p i n g could only survive
Time (minutes) 1 2 5 10 20 60 120
Temperature (~C) 743 880 944 1033 1087 1100 1100
TABLE 2: Time-temperature heating characteristics of the hydrocarbon curve.
FilGURE 1: Insulated GRP piping samples s t a t e u n l e s s pool fire tested as b u t sufficient ',screening tests.
s h o r t p e r i o d s in t h e d r y p r o t e c t e d by fire insulation, fire i n s u l a t i o n could be u s e d to give a n y d e s i r e d dry survival time. When filled with w a t e r a f t e r deluge, survival t i m e of GRI' p i p i n g w a s e s t i m a t e d as being indefinite. GRP p i p i n g m u s t be r e p a i r e d i m m e d i a t e l y if d a m a g e d by h e a v y loads, b u t it is not m o r e sensitive in this r e g a r d t h a n metallic piping. A l t h o u g h GRP is m o r e s u s c e p t i b l e to incid e n t a l d a m a g e by light l o a d s i n d u c e d by p e r s o n n e l , t h e fl'equency of function i m p a i r ing d a m a g e in an e x p l o s i o n or fire e v e n t w a s e s t i m a t e d as less t h a n 1 in 10 000 years. The i m m u n i t y of GRP p i p i n g to s e a w a t e r c o r r o s i o n will let it last lot t h e r e m a i n i n g 20 y e a r life of t h e Valhall field. This t a k e s into a c c o u n t m a r g i n a l loss in p r o p e r t i e s of GRP over time. C a r b o n steel would be e x p e c t e d to lose f u n c t i o n a l i t y within five years. F r o m a v a i l a b l e reliabiliW d a t a b a s e s a n d d e t a i l e d a v a i l a b i l i t y c a l c u l a t i o n s , it w a s e s t i m a t e d t h a t a u t o m a t i c deluge, w h i c h would fill s y s t e m s with w a t e r within 30 sec would fail to o c c u r in a fire e v e n t at a frequen~T of once every 100 000 to 1 million years. However, s h o u l d m a n u a l i n t e r v e n t i o n be required, w a t e r filling could be a c c o m p l i s h e d within a m a x i m u m of 5-10 m i n u t e s . Overall an a p p r o p r i a t e l y e n g i n e e r e d GRP sTstem s h o u l d m e e t t h e f i r e w a t e r w s t e m f u n c t i o n r e q u i r e m e n t s u n d e r all of t h e a c c i d e n t s c e n a r i o s s t u d i e d (2). The t e s t p r o g r a m m e w a s i n t e n d e d to w.'ril~¢ t h i s conclusion, as well as to investigal;e several design specifics not t h o u g h t to h a v e b e e n a d e q u a t e l y a d d r e s s e d in prevqous research.
Verification tests Materials selected for the t e s t p r o g r a m m e were only t h o s e fi)r which levels of f l a m e s p r e a d , s m o k e a n d gas t o x i c i t y r e l e a s e
REINFORCEI) PLASTICS I)ECEMBER 1992
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PECIAL FEATURE
FIGURE 2: Insulated GRP piping during screening pool fire test. d u r i n g fires h a d b e e n well d o c u m e n t e d by suppliers and found acceptable. T h r e e f u n d a m e n t a l l y different t e s t s w e r e c o n d u c t e d on GRP f i r e w a t e r s y s t e m c o m p o nents. Test specifics w e r e b a s e d on the risk a s s e s s m e n t s t u d y a n d t h e close d i a l o g u e e s t a b l i s h e d w i t h NPD. T h e s e t e s t s w e r e p e r f o r m e d o n e p o x y b a s e GRP p i p i n g c o m p o n e n t s of 50 m m d i a m e t e r . The t h r e e fire p r o t e c t i v e i n s u l a t i o n m a t e r i a l s e v a l u a t e d were: • a wire m e s h reinforced i n t u m e s c e n t e p o x y coating; • a s i m i l a r b u t n o n - r e i n f o r c e d coating; a n d • an e x p a n d i n g p o l y m e r w r a p m a t e r i a l . The i n t u m e s c e n t e p o x y c o a t i n g s w e r e applied by h a n d to p i p i n g in t h e initial p r o j e c t p h a s e s . In l a t e r work, p r o p r i e t a r y casting t e c h n i q u e s a n d p r e f o r m e d c o a t i n g shells wel, e used. It w a s f o u n d t h a t a b o u t 8 m m of c o a t i n g w a s r e q u i r e d to give a d e q u a t e p r o t e c t i o n in t h e t e s t s c e n a r i o s d e s c r i b e d below. The effects of an e x p l o s i o n s h o c k w a v e on s t r u c t u r a l m a t e r i a l s c a n be a d e q u a t e l y s i m u l a t e d by slowly s t r a i n i n g m a t e r i a l s in a n oscillatory fashion to deflections c h a r a c teristic of t h e c a l c u l a t e d d r a g forces (3). This is valid for m a t e r i a l s on which explosion w i n d effects are negligible a n d w a s a p p l i c a b l e for all of t h e m a t e r i a l s t e s t e d in this project. GRP s a m p l e s s u b j e c t e d to the s i m u l a t e d e x p l o s i o n t e s t w e r e s t r a i g h t 50 m m p i p e s h a v i n g an a d h e s i v e l y b o n d e d c o n n e c t i o n m i d - s p a n . The GRP p i p e s w e r e fire i n s u l a t e d
REINFORCED PLASTICS DECEMBER 1992
u s i n g t h e m a t e r i a l s d e s c r i b e d above. The s a m p l e s were s u b j e c t e d to f o u r - p o i n t b e n d ing using a hydraulic t e s t i n g m a c h i n e in five cycles, e a c h cycle h a v i n g a lower deflection t h a n t h e p r e v i o u s one. T h e m a x i m u m deflections a p p l i e d w e r e b a s e d on b e n d i n g m o m e n t s w h i c h w o u l d r e s u l t in o u t e r fibre a x i a l s t r a i n s less t h a n or e q u a l to t h e u l t i m a t e a x i a l s t r a i n as r e p o r t e d by t h e GRP m a n u f a c t u r e r . After bending, t h e fire i n s u l a t i o n s w e r e i n s p e c t e d for d a m a g e a n d t h e p i p e s w e r e h y d r o t e s t e d to 1.5 MPa, w h i c h is 1.5 t i m e s t h e w o r k i n g p r e s s u r e of t h e Valhall d r y f i r e w a t e r system. The s a m p l e s w e r e f u r t h e r e v a l u a t e d by p o o l fire testing. No s i g n i f i c a n t d a m a g e r e s u l t e d to t h e piping, a d h e s i v e b o n d s or to t h e fire i n s u l a t i o n m a t e r i a l s by t h e e x p l o s i o n s i m u l a t i o n , as i n d i c a t e d by successful p r e s sure t e s t i n g a n d good fire t e s t p e r f o r m a n c e (4-7). Thus, b a s e d on t h e Valhall design explosion pressure and the bending mom e n t s u s e d in t h e t e s t s , ' s a f e ' s u p p o r t s e p a r a t i o n d i s t a n c e s w e r e calculated. The Valhall s u p p o r t d i s t a n c e s d e t e r m i n e d in this f a s h i o n w e r e c o m p a r a b l e to or g r e a t e r t h a n t h o s e r e q u i r e d by h a n g i n g w e i g h t c o n s i d e r a tions, a n d t h e r e f o r e h a v e m i n i m a l effect on firewater system piping construction. Two v a r i a t i o n s on h y d r o c a r b o n pool fire t e s t s w e r e u s e d f o r e v a l u a t i o n of GRP f i r e w a t e r systems. During t h e initial p e r i o d of tests, t i m e - t e m p e r a t u r e h e a t i n g c h a r a c t e r istics followed t h e h y d r o c a r b o n (HC) c u r v e as d e f i n e d b y t h e NPD a n d t h e U K ' s D e p a r t m e n t of E n e r g y (Table 2). B a s e d on risk a s s e s s m e n t s t u d y r e s u l t s t h a t s h o w e d e x t r e m e l y high deluge reliability, a 5 m i n u t e fire e x p o s u r e t i m e for p i p i n g in the dry condition was used and was considered a c o n s e r v a t i v e a p p r o a c h . After t h i s period, flowing w a t e r at 1.0 MPa w a s i n t r o d u c e d into t h e GRP p i p i n g s y s t e m s a n d m a i n t a i n e d for t h e r e m a i n i n g d u r a t i o n of tests. The two p o o l fire t e s t s c e n a r i o s u s e d different h e a t i n g c h a r a c t e r i s t i c s a n d t o t a l t e s t d u r a t i o n . The first r e l a t e d to p e r s o n n e l safety, h e n c e HC curve h e a t i n g w a s m a i n tained. This t e s t gave a h e a t flux of 150-200 k W / m 2. A m i n i m u m d u r a t i o n of 20 m i n u t e s w a s used, c o r r e s p o n d i n g to t h e Valhall e s c a p e / e v a l u a t i o n time. The s e c o n d t e s t t y p e w a s r e l a t e d to p r o t e c t i o n o f facilities a n d w a s p e r f o r m e d for a m i n i m u m of 80 m i n u t e s , t h e m a x i m u m p o o l fire d u r a t i o n p o s s i b l e at Valhall. B e c a u s e s h o r t - t e r m s t r u c t u r a l steel failu r e s could be e x p e c t e d unless w a t e r deluge r e d u c e d t e m p e r a t u r e s to b e l o w 650°C, t h e
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t e s t t e m p e r a t u r e w a s r e d u c e d to 650°C a f t e r the initial 5 m i n u t e dry e x p o s u r e w i t h a h e a t flux of 50-75 k W / m 2. This w a s m a i n t a i n e d until t e s t conclusion. The 650~C facilitiesp r o t e c t i o n r a t i o n a l e w a s b a s e d on t h e definition t h a t GRP f i r e w a t e r s y s t e m survivability s h o u l d be a b o u t e q u a l to t h a t of u n p r o t e c t e d s t r u c t u r a l steels e x p o s e d to fire (i.e. t h e p r e s e n c e of d e l u g e w a t e r a n d t e m p e r a t u r e r e d u c t i o n s to below 6 5 0 C is relied upon for the extended duration survival of b o t h t h e f i r e w a t e r s y s t e m a n d steel s t r u c t u r e s ) . T e s t i n g by t h i s l a t t e r s c e n a r i o is r e f e r r e d to as s i m u l a t e d deluge p o o l fire testing. Many p o o l fire t e s t s w e r e c o n d u c t e d in t h e p r o g r a m m e , u s i n g ()pen a d d closed furnaces. A o n e - q u a r t e r scale offshore m o d u l e at t h e S I N T E F fire l a b o r a t o r i e s in T r o n d h e i m , Norway, w a s used for s y s t e m tests. I n s u l a t e d GRP p i p i n g s a m p l e s c o n s i s t i n g of s t r a i g h t 50 m m p i p i n g with m i d - s p a n a d h e s i v e l y b o n d e d c o n n e c t i o n s w e r e u s e d as s c r e e n i n g t e s t s (Figures 1 a n d 2). More c o m p l i c a t e d p i p i n g s a m p l e s w e r e u s e d for closed f u r n a c e t e s t s a n d t h o s e c o n d u c t e d in t h e SINTEF m o d u l e mode, t h e l a r g e s t of w h i c h m e a s u r e d 1.5 x 4 m (Figures 3). All of the m a j o r c o m p o n e n t s r e q u i r e d for GRP f i r e w a t e r s y s t e m c o n s t r u c t i o n w e r e u s e d in t h e s e tests. T h e s e i n c l u d e d s t r a i g h t p i p i n g with b o n d e d c o n n e c t i o n s , fittings (elbows, tees, etc.), a n c h o r s , s u p p o r t s , s p r a y n o z z l e s / s p r i n k l e r heads, flanges a n d a n e x p a n s i o n loop. Results of t h e pool fire t e s t s are c o n t a i n e d in n u m e r o u s r e p o r t s (6-9). The i n s u l a t e d GRP f i r e w a t e r s y s t e m p i p i n g s a m p l e s w e r e a b l e to m a i n t a i n 1.0 MPa p r e s s u r e a n d t r a n s p o r t w a t e r t h r o u g h o u t all of t h e t e s t s p e r f o r m e d , even in e x t e n d e d s i m u l a t e d deluge t e s t s c o n t i n u e d for u p to 6 hours. A few m i n o r w a t e r leaks w e r e o b s e r v e d at flanged connections, but based on the f u n c t i o n c r i t e r i a e s t a b l i s h e d in t h e risk a s s e s s m e n t , t h e GRP p i p i n g s y s t e m s m e t all of the p e r f o r m a n c e r e q u i r e m e n t s n e c e s s a r y for Valhall d w deluge f i r e w a t e r systems.
J e t fire tests J e t fire t e s t s were u s e d to e v a l u a t e t h e p e r f o r m a n c e of i n s u l a t e d GRP f i r e w a t e r s y s t e m c o m p o n e n t s e x p o s e d to c o n d i t i o n s r e p r e s e n t a t i v e of a b u r n i n g gas leak f r o m pressurized process equipment. These tests w e r e p e r i b r m e d at SINTEF. The j e t fire t e s t m e t h o d is c h a r a c t e r i z e d by t e m p e r a t u r e s u p
to 1250:C, t o t a l h e a t f l u x ()IF a b o u t 320 k W / m e a n d f l a m e / g a s v e l o c i t i e s of 45-60 m / s e e (10). J e t fire GRP s a m p l e s w e r e s t r a i g h t 50 m m p i p e s h a v i n g a n a d h e s i v e l y b o n d e d connection m i d - s p a n . The s a m p l e s w e r e i n s u l a t e d with t h e m a t e r i a l s d e s c r i b e d above. B a s e d on the risk a s s e s s m e n t reliability s t u d y a n d p e r s o n n e l e v a c u a t i o n times, t h e s a m p l e s w e r e t e s t e d f o r 5 m i n u t e s in t h e d r y c o n d i t i o n a n d t h e n filled w i t h f l o ~ i n g w a t e r at 1.0 MPa tbr the b a l a n c e of the 20 m i n u t e m i n i m u m t o t a l t e s t d u r a t i o n ( t e s t s w e r e in fact r u n for 30 m i n u t e s t o t a l ) . All of t h e s a m p l e s t e s t e d m a i n t a i n e d t h e ability to transport w a t e r a t 10 b a r g t h r o u g h o u t the d u r a t i o n of the tests, without o b s e r v a b l e w a t e r weeping. B a s e d on the risk assessment function criterion with r e s p e c t to p e r s o n n e l p r o t e c t i o n , t h e insul a t e d GRP s a m p l e s m e t all p e r f o r m a n c e r e q u i r e m e n t s for Valhall dry f i r e w a t e r syst e m p i p i n g (11-12).
Specifications/quality GRP f i r e w a t e r s y s t e m s p e c i f i c a t i o n s w e r e b a s e d on findings of t h e risk a s s e s s m e n t a n d verification t e s t p r o g r a m m e , as well as on t h e collective e x p e r i e n c e s of t h e p r o j e c t c o - s p o n s o r s , m a n u f a c t u r e r s a n d installers. Reliability a n d q u a l i t y a s s u r a n c e w e r e s t r e s s e d in the specifications, r e s u l t i n g in requirements above those normally applied to GRP utility piping. S o m e h i g h l i g h t s of t h e s e r e q u i r e m e n t s follow. M a x i m u m use m u s t be m a d e of t h e latest i n t e r n a t i o n a l l y a c c e p t e d GRP s p e c i f i c a t i o n s references.
REINFORCED PLASTICS DECEMBER 1992
FIGURE 3: One of two insulated GRP firewater system samples pool fire tested using simulated deluge scenario. The systems contained all components required for offshore installation.
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PECIAL FEATURE
FIGURE 4: Insulated GRP piping sample before jet fire testing.
Materials manufacturers, prefabricators, fire insulators, and system installers are required to have quality assurance (QA) systems equal to or exceeding those detailed in ISO 9001 and 9002 specifications. Manufacture of firewater system materials is defined as a 'special process,' for which higher standards apply. Significant portions of engineering design and acceptability of fire test results must be
References (1). Norwegian Petroleum Directorate, Regulations Concerning the Implementation and Use of Risk Analysis in the Petroleum Activities with Guidelines, Stavanger, Norway, August 1990. (2). Technica A/S, Relative Merits of Conventional Steel Versus GRE in Firewater System Risk Assessment, Project No. N558, Stavanger, Norway, 23 August 1990. (3). T.A. H-verstad, Explosion and Fire Testing, Report Part 13, Final Report Specifications and Test Methods, in Norw e g i a n , SINTEF FCB R e p o r t STF65 A88027, Trondheim, Norway, 1988. (4). G. Drangsholt, Simulated Explosion Test of Three GRE Pipes Insulated with Pittchar, Fauvuseal and Chartek III, SINTEF NBL Report No. STF25 F91012, Trondheim, Norway, 10 April 1991. (5). G. Drangsholt, Simulated Explosion Test of Two GRE Pipes Insulated with Pittchar and Chartek III, SINTEF NBL Report No. STF25 F91039, Trondheim, Norway, 17 October 1991. (6). O. S-tre, Fire Water Pipes in Composites, Final Report -- Phase 1, Advanced
:l
R E I N F O R C E D PLASTICS D E C E M B E R 1992
based on a facilities-specific risk assessment study. These requirements are attached as an appendix to the specifications, which cannot be fully utilized without this information. Minimum education and experience levels are r e q u i r e d for GRP firewater system designers. Bonders must be trained by the pipe manufacturer and must pass a series of job-specific qualification tests. Detailed stress analyses of piping systems by numerical methods are required. Pipe bonding must be witnessed by a qualified inspector, who prepares written documentation of procedures applicable to the work. All bonds are uniquely identified and traceable to specific bonders and inspector. To t r o u b l e s h o o t complete dry system retrofits, a prototype pilot system of fire insulated GRP piping was installed at Valhall in December 1991. This dry system consisted of about 300 m of 50-200 mm diameter piping and 90 spray nozzles and sprinkler heads. No major problems were encountered during installation. • A fuller version of this article was presented by the authors at the Offshore Technology Conference, Houston, Texas, USA, May 1992.
Materials Project No. 201, Sandefjord, Norway, 6 May 1991. (7). J. Sundt, Composite Fire Water Systems, Valhall Optimization Studies, Advanced Materials Project No. 201-2, Sandetjord, Norway, 1 October 1991. (8). G. Drangsholt, Fire Test on Insulated GRE Pipes with Sprinkler/Spray Nozzle A t t a c h m e n t and Flanges in t h e Pilot Furnace, SINTEF NBL Test Certificate Task No. 251574.00, Trondheim, Norway, 9 November 1991. (9). G. Drangsholt, System and Trial Test on a GRE Deluge F i r e w a t e r System, SINTEF NBL Report No. STF25 F91013, Trondheim, Norway, 16 April 1991. (10). G. Drangsholt and R. Wighus, Test Conditions for an Impinging Jet Fire, Preliminary Study, SINTEF NBL Report No STF25 F90017, Trondheim, Norway, 1990. (11). G. Drangsholt, Jet Fire Tests on Four Insulated GRE Pipes, SINTEF NBL Report No. STF25 F91009, Trondheim, Norway, 25 April 1991. (12). G. Drangsholt, Jet Fire Tests on Two Insulated GRE Pipes, SINTEF NBL Report No. STF25 F91036, Trondheim, Norway, 25 April 1991.
PECIAL
FEATURE
GRP better than steel for offshore pipes A m o c o N o r w a y Oil C o m p a n y b e l i e v e s t h a t r e p l a c i n g s t e e l p i p i n g with GRP w i l l i m p r o v e the availability o f d e l u g e f i r e w a t e r s y s t e m s o n t h e N o r t h S e a oil p l a t f o r m s o f the Valhall field. A m o c o ' s S. W. Ciaraldi, J.D. Alkire and G.G. H u n t o o n d e s c r i b e t h e r e s u l t s o f the c o m p a n y ' s t e s t p r o g r a m m e to verify t h e suitability o f GRP for this a p p l i c a t i o n .
moco Norway Oil Company recently reviewed the Valhall firewater System with the goal of improving System reliability to 100%. The company estimated t h a t the use of glass reinforced plastic (GRP) piping components, which are essentially TABLE 1: Relative comparison of Valhall i m m u n e to s e a wat er corrosion, was the dry deluge firewater most cost-effective approach (Table 1).
A
system options. Option :
Installed cost relatiyeto insulatedGRP
Comments : :: ::
:
: :
: : :: : : :
Replace with insulated GRP
1.0
Preferred option
Maintain steel with high pressure water flushing
1.9
2 year retreatment rate. 1990 cost over field life. Assumes no replacements. Inadequate reliability.
Maintain steel with acid cleaning and wax coating
2.3
3 year retreatment rate, 1990 cost over field life. Assumes no replacements. Inadequate reliability,
Replace with carbon steel
1.1
Inadequate reliability. Maintenance not included.
Replace witlq cupronickel
1.6
May not last for field life. Reliability unknown.
Replace with titanium
1.2
Optimistic estimate, Reliability unknown.
Replace with 6% Mo stainless
1.5
Replace with super dupJex stainlesg
1.7
REINFORCED PLASTICS DECEMBER 1992
Deluge firewater systems are used in the wellhead and process areas of offshore oil pl at form s. For o p e r a t i o n a l reasons, t h e majority of piping in these types of systems does not contain water. Spray nozzles and sprinkler heads are left open. On detection of a fire or a high gas level, a deluge valve opens t hat allows large am ount s of water from a pressurized wet system to flood into the dry piping. A typical oil platform will have many kilometres of dry deluge firewater piping t hat is traditionally made of carbon steels. Dry piping sizes are predominantly less than 200 mm diameter, with most being less th a n 50 ram. Because the systems often use seawater and are continuously exposed to the hostile offshore environment, internal corrosion is common. This leads not only to loss of wall thickness, but to blocking of spray nozzles and sprinkler heads by corrosion products and scales. Amoco n o t i c e d t h a t every two y e a r s s i g n i f i c a n t blocking of s p r i n k l e r h e a d s occurs in the deluge systems on its platforms in the Valhall field. Incomplete draining of the system internally exposed the del uge p i p i n g to o x y g e n a t e d seawater. Several extensive and costly system cleanouts have been required to maintain operat i onal status. F u r t h e r reliability of th e syst em s was r e g a r d e d as q u e s t i o n a b l e , despite the m ai nt enance efforts. Amoco established a dialogue with the Norwegian Petroleum Directorate (NPD) to discuss the use of non-metallic materials for offshore safety systems, a practice restricted by existing regulations. Three fundamental tasks were identified as necessary to justify the use of GRP firewater Systems from a safety viewpoint: • a risk a s s e s s m e n t s t u d y to establish function and acceptance criteria; • a fire survivability verification test programme; and • detailed specifications and quality assurance Systems. A p r o j e c t s p o n s o r e d by oil c o m p a n i e s Amoco, Conoco, Shell and Statoil formu-
0034-3617/92/$3.50 ~, 1992, Elsevier Science Publishers Ltd.
S
PECIAL FEATURE
l a t e d a p l a n to a d d r e s s t h e s e tasks. The p r o j e c t r e s u l t e d in successful safety justification of GRP d r y f i r e w a t e r s y s t e m s a n d NPD c o n s e n t for use of t h e s e m a t e r i a l s for t h e dry deluge s y s t e m s at Valhall.
Risk assessment study The NPD h a s for m a n y y e a r s p r o m o t e d risk a s s e s s m e n t s t u d i e s as t o o l s to i m p r o v e offshore safe.ty (1). The a p p r o a c h w s t e m atically establishes performance criteria, then evaluates performance under accident e v e n t s such as e x p l o s i o n s a n d fires. T h e f u n c t i o n c r i t e r i o n for t h e Valhall firewater system stated that the system pedbrmance should reduce heat radiation levels so t h a t p e r s o n n e l e v a c u a t i o n or e s c a p e is p o s s i b l e u n d e r c e r t a i n a c c i d e n t s c e n a r i o s (2). The time needed lbr escape and e v a c u a t i o n w a s e s t i m a t e d to be 20 m i n u t e s . A s e c o n d a r y f u n c t i o n criterion c o n c e r n i n g p r o t e c t i o n of t h e facilities e s t i m a t e d t h a t a t i m e of 80 m i n u t e s w a s n e e d e d . T h i s i n c l u d e d t h e m a x i m u m d u r a t i o n of a fire event at Valhall u n d e r a s s e s s e d risk criteria. The four m a i n a c c i d e n t c o n s i d e r e d w e r e t h o s e of e x p l o s i o n s , fires, i m p a c t d a m a g e a n d h m g - t e r m durability. The last two w e r e e v a l u a t e d with r e s p e c t to p e r f o r m a n c e in e x p l o s i o n s a n d fires. B e c a u s e of e p o x y resin's good-high temperature properties a n d b e c a u s e of t h e g r e a t e x p e r i e n c e in using e p o x y GRP, only t h e s e m a t e r i a l s w e r e e v a l u a t e d in t h e study. Using a c c e p t e d t h e o r i e s a n d m o d e l s t h e design e x p l o s i o n p r e s s u r e at Valhall was calculated, e x p l o s i o n s having a frequencT of 1 in 10 l)00 y e a r s . S u p p o r t s e p a r a t i o n d i s t a n c e s lbr GRt' p i p i n g m u s t be d e s i g n e d so t h a t d r a g tbrces f r o m this e x p l o s i o n p r e s s u r e will not seriously d a m a g e p i p i n g or p r o t e c t i v e fire insulation. A h i g h - p r e s s u r e gas fire, or .jet fire, a f t e r an e x p l o s i o n w a s c o n s i d e r e d as t h e w o r s t case event. GRP p i p i n g could only survive
Time (minutes) 1 2 5 10 20 60 120
Temperature (~C) 743 880 944 1033 1087 1100 1100
TABLE 2: Time-temperature heating characteristics of the hydrocarbon curve.
FilGURE 1: Insulated GRP piping samples s t a t e u n l e s s pool fire tested as b u t sufficient ',screening tests.
s h o r t p e r i o d s in t h e d r y p r o t e c t e d by fire insulation, fire i n s u l a t i o n could be u s e d to give a n y d e s i r e d dry survival time. When filled with w a t e r a f t e r deluge, survival t i m e of GRI' p i p i n g w a s e s t i m a t e d as being indefinite. GRP p i p i n g m u s t be r e p a i r e d i m m e d i a t e l y if d a m a g e d by h e a v y loads, b u t it is not m o r e sensitive in this r e g a r d t h a n metallic piping. A l t h o u g h GRP is m o r e s u s c e p t i b l e to incid e n t a l d a m a g e by light l o a d s i n d u c e d by p e r s o n n e l , t h e fl'equency of function i m p a i r ing d a m a g e in an e x p l o s i o n or fire e v e n t w a s e s t i m a t e d as less t h a n 1 in 10 000 years. The i m m u n i t y of GRP p i p i n g to s e a w a t e r c o r r o s i o n will let it last lot t h e r e m a i n i n g 20 y e a r life of t h e Valhall field. This t a k e s into a c c o u n t m a r g i n a l loss in p r o p e r t i e s of GRP over time. C a r b o n steel would be e x p e c t e d to lose f u n c t i o n a l i t y within five years. F r o m a v a i l a b l e reliabiliW d a t a b a s e s a n d d e t a i l e d a v a i l a b i l i t y c a l c u l a t i o n s , it w a s e s t i m a t e d t h a t a u t o m a t i c deluge, w h i c h would fill s y s t e m s with w a t e r within 30 sec would fail to o c c u r in a fire e v e n t at a frequen~T of once every 100 000 to 1 million years. However, s h o u l d m a n u a l i n t e r v e n t i o n be required, w a t e r filling could be a c c o m p l i s h e d within a m a x i m u m of 5-10 m i n u t e s . Overall an a p p r o p r i a t e l y e n g i n e e r e d GRP sTstem s h o u l d m e e t t h e f i r e w a t e r w s t e m f u n c t i o n r e q u i r e m e n t s u n d e r all of t h e a c c i d e n t s c e n a r i o s s t u d i e d (2). The t e s t p r o g r a m m e w a s i n t e n d e d to w.'ril~¢ t h i s conclusion, as well as to investigal;e several design specifics not t h o u g h t to h a v e b e e n a d e q u a t e l y a d d r e s s e d in prevqous research.
Verification tests Materials selected for the t e s t p r o g r a m m e were only t h o s e fi)r which levels of f l a m e s p r e a d , s m o k e a n d gas t o x i c i t y r e l e a s e
REINFORCEI) PLASTICS I)ECEMBER 1992
S
PECIAL FEATURE
FIGURE 2: Insulated GRP piping during screening pool fire test. d u r i n g fires h a d b e e n well d o c u m e n t e d by suppliers and found acceptable. T h r e e f u n d a m e n t a l l y different t e s t s w e r e c o n d u c t e d on GRP f i r e w a t e r s y s t e m c o m p o nents. Test specifics w e r e b a s e d on the risk a s s e s s m e n t s t u d y a n d t h e close d i a l o g u e e s t a b l i s h e d w i t h NPD. T h e s e t e s t s w e r e p e r f o r m e d o n e p o x y b a s e GRP p i p i n g c o m p o n e n t s of 50 m m d i a m e t e r . The t h r e e fire p r o t e c t i v e i n s u l a t i o n m a t e r i a l s e v a l u a t e d were: • a wire m e s h reinforced i n t u m e s c e n t e p o x y coating; • a s i m i l a r b u t n o n - r e i n f o r c e d coating; a n d • an e x p a n d i n g p o l y m e r w r a p m a t e r i a l . The i n t u m e s c e n t e p o x y c o a t i n g s w e r e applied by h a n d to p i p i n g in t h e initial p r o j e c t p h a s e s . In l a t e r work, p r o p r i e t a r y casting t e c h n i q u e s a n d p r e f o r m e d c o a t i n g shells wel, e used. It w a s f o u n d t h a t a b o u t 8 m m of c o a t i n g w a s r e q u i r e d to give a d e q u a t e p r o t e c t i o n in t h e t e s t s c e n a r i o s d e s c r i b e d below. The effects of an e x p l o s i o n s h o c k w a v e on s t r u c t u r a l m a t e r i a l s c a n be a d e q u a t e l y s i m u l a t e d by slowly s t r a i n i n g m a t e r i a l s in a n oscillatory fashion to deflections c h a r a c teristic of t h e c a l c u l a t e d d r a g forces (3). This is valid for m a t e r i a l s on which explosion w i n d effects are negligible a n d w a s a p p l i c a b l e for all of t h e m a t e r i a l s t e s t e d in this project. GRP s a m p l e s s u b j e c t e d to the s i m u l a t e d e x p l o s i o n t e s t w e r e s t r a i g h t 50 m m p i p e s h a v i n g an a d h e s i v e l y b o n d e d c o n n e c t i o n m i d - s p a n . The GRP p i p e s w e r e fire i n s u l a t e d
REINFORCED PLASTICS DECEMBER 1992
u s i n g t h e m a t e r i a l s d e s c r i b e d above. The s a m p l e s were s u b j e c t e d to f o u r - p o i n t b e n d ing using a hydraulic t e s t i n g m a c h i n e in five cycles, e a c h cycle h a v i n g a lower deflection t h a n t h e p r e v i o u s one. T h e m a x i m u m deflections a p p l i e d w e r e b a s e d on b e n d i n g m o m e n t s w h i c h w o u l d r e s u l t in o u t e r fibre a x i a l s t r a i n s less t h a n or e q u a l to t h e u l t i m a t e a x i a l s t r a i n as r e p o r t e d by t h e GRP m a n u f a c t u r e r . After bending, t h e fire i n s u l a t i o n s w e r e i n s p e c t e d for d a m a g e a n d t h e p i p e s w e r e h y d r o t e s t e d to 1.5 MPa, w h i c h is 1.5 t i m e s t h e w o r k i n g p r e s s u r e of t h e Valhall d r y f i r e w a t e r system. The s a m p l e s w e r e f u r t h e r e v a l u a t e d by p o o l fire testing. No s i g n i f i c a n t d a m a g e r e s u l t e d to t h e piping, a d h e s i v e b o n d s or to t h e fire i n s u l a t i o n m a t e r i a l s by t h e e x p l o s i o n s i m u l a t i o n , as i n d i c a t e d by successful p r e s sure t e s t i n g a n d good fire t e s t p e r f o r m a n c e (4-7). Thus, b a s e d on t h e Valhall design explosion pressure and the bending mom e n t s u s e d in t h e t e s t s , ' s a f e ' s u p p o r t s e p a r a t i o n d i s t a n c e s w e r e calculated. The Valhall s u p p o r t d i s t a n c e s d e t e r m i n e d in this f a s h i o n w e r e c o m p a r a b l e to or g r e a t e r t h a n t h o s e r e q u i r e d by h a n g i n g w e i g h t c o n s i d e r a tions, a n d t h e r e f o r e h a v e m i n i m a l effect on firewater system piping construction. Two v a r i a t i o n s on h y d r o c a r b o n pool fire t e s t s w e r e u s e d f o r e v a l u a t i o n of GRP f i r e w a t e r systems. During t h e initial p e r i o d of tests, t i m e - t e m p e r a t u r e h e a t i n g c h a r a c t e r istics followed t h e h y d r o c a r b o n (HC) c u r v e as d e f i n e d b y t h e NPD a n d t h e U K ' s D e p a r t m e n t of E n e r g y (Table 2). B a s e d on risk a s s e s s m e n t s t u d y r e s u l t s t h a t s h o w e d e x t r e m e l y high deluge reliability, a 5 m i n u t e fire e x p o s u r e t i m e for p i p i n g in the dry condition was used and was considered a c o n s e r v a t i v e a p p r o a c h . After t h i s period, flowing w a t e r at 1.0 MPa w a s i n t r o d u c e d into t h e GRP p i p i n g s y s t e m s a n d m a i n t a i n e d for t h e r e m a i n i n g d u r a t i o n of tests. The two p o o l fire t e s t s c e n a r i o s u s e d different h e a t i n g c h a r a c t e r i s t i c s a n d t o t a l t e s t d u r a t i o n . The first r e l a t e d to p e r s o n n e l safety, h e n c e HC curve h e a t i n g w a s m a i n tained. This t e s t gave a h e a t flux of 150-200 k W / m 2. A m i n i m u m d u r a t i o n of 20 m i n u t e s w a s used, c o r r e s p o n d i n g to t h e Valhall e s c a p e / e v a l u a t i o n time. The s e c o n d t e s t t y p e w a s r e l a t e d to p r o t e c t i o n o f facilities a n d w a s p e r f o r m e d for a m i n i m u m of 80 m i n u t e s , t h e m a x i m u m p o o l fire d u r a t i o n p o s s i b l e at Valhall. B e c a u s e s h o r t - t e r m s t r u c t u r a l steel failu r e s could be e x p e c t e d unless w a t e r deluge r e d u c e d t e m p e r a t u r e s to b e l o w 650°C, t h e
S PECIAL
FEATURE
t e s t t e m p e r a t u r e w a s r e d u c e d to 650°C a f t e r the initial 5 m i n u t e dry e x p o s u r e w i t h a h e a t flux of 50-75 k W / m 2. This w a s m a i n t a i n e d until t e s t conclusion. The 650~C facilitiesp r o t e c t i o n r a t i o n a l e w a s b a s e d on t h e definition t h a t GRP f i r e w a t e r s y s t e m survivability s h o u l d be a b o u t e q u a l to t h a t of u n p r o t e c t e d s t r u c t u r a l steels e x p o s e d to fire (i.e. t h e p r e s e n c e of d e l u g e w a t e r a n d t e m p e r a t u r e r e d u c t i o n s to below 6 5 0 C is relied upon for the extended duration survival of b o t h t h e f i r e w a t e r s y s t e m a n d steel s t r u c t u r e s ) . T e s t i n g by t h i s l a t t e r s c e n a r i o is r e f e r r e d to as s i m u l a t e d deluge p o o l fire testing. Many p o o l fire t e s t s w e r e c o n d u c t e d in t h e p r o g r a m m e , u s i n g ()pen a d d closed furnaces. A o n e - q u a r t e r scale offshore m o d u l e at t h e S I N T E F fire l a b o r a t o r i e s in T r o n d h e i m , Norway, w a s used for s y s t e m tests. I n s u l a t e d GRP p i p i n g s a m p l e s c o n s i s t i n g of s t r a i g h t 50 m m p i p i n g with m i d - s p a n a d h e s i v e l y b o n d e d c o n n e c t i o n s w e r e u s e d as s c r e e n i n g t e s t s (Figures 1 a n d 2). More c o m p l i c a t e d p i p i n g s a m p l e s w e r e u s e d for closed f u r n a c e t e s t s a n d t h o s e c o n d u c t e d in t h e SINTEF m o d u l e mode, t h e l a r g e s t of w h i c h m e a s u r e d 1.5 x 4 m (Figures 3). All of the m a j o r c o m p o n e n t s r e q u i r e d for GRP f i r e w a t e r s y s t e m c o n s t r u c t i o n w e r e u s e d in t h e s e tests. T h e s e i n c l u d e d s t r a i g h t p i p i n g with b o n d e d c o n n e c t i o n s , fittings (elbows, tees, etc.), a n c h o r s , s u p p o r t s , s p r a y n o z z l e s / s p r i n k l e r heads, flanges a n d a n e x p a n s i o n loop. Results of t h e pool fire t e s t s are c o n t a i n e d in n u m e r o u s r e p o r t s (6-9). The i n s u l a t e d GRP f i r e w a t e r s y s t e m p i p i n g s a m p l e s w e r e a b l e to m a i n t a i n 1.0 MPa p r e s s u r e a n d t r a n s p o r t w a t e r t h r o u g h o u t all of t h e t e s t s p e r f o r m e d , even in e x t e n d e d s i m u l a t e d deluge t e s t s c o n t i n u e d for u p to 6 hours. A few m i n o r w a t e r leaks w e r e o b s e r v e d at flanged connections, but based on the f u n c t i o n c r i t e r i a e s t a b l i s h e d in t h e risk a s s e s s m e n t , t h e GRP p i p i n g s y s t e m s m e t all of the p e r f o r m a n c e r e q u i r e m e n t s n e c e s s a r y for Valhall d w deluge f i r e w a t e r systems.
J e t fire tests J e t fire t e s t s were u s e d to e v a l u a t e t h e p e r f o r m a n c e of i n s u l a t e d GRP f i r e w a t e r s y s t e m c o m p o n e n t s e x p o s e d to c o n d i t i o n s r e p r e s e n t a t i v e of a b u r n i n g gas leak f r o m pressurized process equipment. These tests w e r e p e r i b r m e d at SINTEF. The j e t fire t e s t m e t h o d is c h a r a c t e r i z e d by t e m p e r a t u r e s u p
to 1250:C, t o t a l h e a t f l u x ()IF a b o u t 320 k W / m e a n d f l a m e / g a s v e l o c i t i e s of 45-60 m / s e e (10). J e t fire GRP s a m p l e s w e r e s t r a i g h t 50 m m p i p e s h a v i n g a n a d h e s i v e l y b o n d e d connection m i d - s p a n . The s a m p l e s w e r e i n s u l a t e d with t h e m a t e r i a l s d e s c r i b e d above. B a s e d on the risk a s s e s s m e n t reliability s t u d y a n d p e r s o n n e l e v a c u a t i o n times, t h e s a m p l e s w e r e t e s t e d f o r 5 m i n u t e s in t h e d r y c o n d i t i o n a n d t h e n filled w i t h f l o ~ i n g w a t e r at 1.0 MPa tbr the b a l a n c e of the 20 m i n u t e m i n i m u m t o t a l t e s t d u r a t i o n ( t e s t s w e r e in fact r u n for 30 m i n u t e s t o t a l ) . All of t h e s a m p l e s t e s t e d m a i n t a i n e d t h e ability to transport w a t e r a t 10 b a r g t h r o u g h o u t the d u r a t i o n of the tests, without o b s e r v a b l e w a t e r weeping. B a s e d on the risk assessment function criterion with r e s p e c t to p e r s o n n e l p r o t e c t i o n , t h e insul a t e d GRP s a m p l e s m e t all p e r f o r m a n c e r e q u i r e m e n t s for Valhall dry f i r e w a t e r syst e m p i p i n g (11-12).
Specifications/quality GRP f i r e w a t e r s y s t e m s p e c i f i c a t i o n s w e r e b a s e d on findings of t h e risk a s s e s s m e n t a n d verification t e s t p r o g r a m m e , as well as on t h e collective e x p e r i e n c e s of t h e p r o j e c t c o - s p o n s o r s , m a n u f a c t u r e r s a n d installers. Reliability a n d q u a l i t y a s s u r a n c e w e r e s t r e s s e d in the specifications, r e s u l t i n g in requirements above those normally applied to GRP utility piping. S o m e h i g h l i g h t s of t h e s e r e q u i r e m e n t s follow. M a x i m u m use m u s t be m a d e of t h e latest i n t e r n a t i o n a l l y a c c e p t e d GRP s p e c i f i c a t i o n s references.
REINFORCED PLASTICS DECEMBER 1992
FIGURE 3: One of two insulated GRP firewater system samples pool fire tested using simulated deluge scenario. The systems contained all components required for offshore installation.
S
PECIAL FEATURE
FIGURE 4: Insulated GRP piping sample before jet fire testing.
Materials manufacturers, prefabricators, fire insulators, and system installers are required to have quality assurance (QA) systems equal to or exceeding those detailed in ISO 9001 and 9002 specifications. Manufacture of firewater system materials is defined as a 'special process,' for which higher standards apply. Significant portions of engineering design and acceptability of fire test results must be
References (1). Norwegian Petroleum Directorate, Regulations Concerning the Implementation and Use of Risk Analysis in the Petroleum Activities with Guidelines, Stavanger, Norway, August 1990. (2). Technica A/S, Relative Merits of Conventional Steel Versus GRE in Firewater System Risk Assessment, Project No. N558, Stavanger, Norway, 23 August 1990. (3). T.A. H-verstad, Explosion and Fire Testing, Report Part 13, Final Report Specifications and Test Methods, in Norw e g i a n , SINTEF FCB R e p o r t STF65 A88027, Trondheim, Norway, 1988. (4). G. Drangsholt, Simulated Explosion Test of Three GRE Pipes Insulated with Pittchar, Fauvuseal and Chartek III, SINTEF NBL Report No. STF25 F91012, Trondheim, Norway, 10 April 1991. (5). G. Drangsholt, Simulated Explosion Test of Two GRE Pipes Insulated with Pittchar and Chartek III, SINTEF NBL Report No. STF25 F91039, Trondheim, Norway, 17 October 1991. (6). O. S-tre, Fire Water Pipes in Composites, Final Report -- Phase 1, Advanced
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R E I N F O R C E D PLASTICS D E C E M B E R 1992
based on a facilities-specific risk assessment study. These requirements are attached as an appendix to the specifications, which cannot be fully utilized without this information. Minimum education and experience levels are r e q u i r e d for GRP firewater system designers. Bonders must be trained by the pipe manufacturer and must pass a series of job-specific qualification tests. Detailed stress analyses of piping systems by numerical methods are required. Pipe bonding must be witnessed by a qualified inspector, who prepares written documentation of procedures applicable to the work. All bonds are uniquely identified and traceable to specific bonders and inspector. To t r o u b l e s h o o t complete dry system retrofits, a prototype pilot system of fire insulated GRP piping was installed at Valhall in December 1991. This dry system consisted of about 300 m of 50-200 mm diameter piping and 90 spray nozzles and sprinkler heads. No major problems were encountered during installation. • A fuller version of this article was presented by the authors at the Offshore Technology Conference, Houston, Texas, USA, May 1992.
Materials Project No. 201, Sandefjord, Norway, 6 May 1991. (7). J. Sundt, Composite Fire Water Systems, Valhall Optimization Studies, Advanced Materials Project No. 201-2, Sandetjord, Norway, 1 October 1991. (8). G. Drangsholt, Fire Test on Insulated GRE Pipes with Sprinkler/Spray Nozzle A t t a c h m e n t and Flanges in t h e Pilot Furnace, SINTEF NBL Test Certificate Task No. 251574.00, Trondheim, Norway, 9 November 1991. (9). G. Drangsholt, System and Trial Test on a GRE Deluge F i r e w a t e r System, SINTEF NBL Report No. STF25 F91013, Trondheim, Norway, 16 April 1991. (10). G. Drangsholt and R. Wighus, Test Conditions for an Impinging Jet Fire, Preliminary Study, SINTEF NBL Report No STF25 F90017, Trondheim, Norway, 1990. (11). G. Drangsholt, Jet Fire Tests on Four Insulated GRE Pipes, SINTEF NBL Report No. STF25 F91009, Trondheim, Norway, 25 April 1991. (12). G. Drangsholt, Jet Fire Tests on Two Insulated GRE Pipes, SINTEF NBL Report No. STF25 F91036, Trondheim, Norway, 25 April 1991.