Weld testing on Irwell Valley Bridge

Weld testing on Irwell Valley Bridge

Indt WELD TESTING ON IRWELL VALLEY BRIDGE The weld l e s l i n g which was c a r r i e d oal oil the I r w e l l Valley B r i d g e i l l u s t r a l ...

465KB Sizes 0 Downloads 61 Views

Indt WELD TESTING ON IRWELL VALLEY BRIDGE The weld l e s l i n g which was c a r r i e d oal oil the I r w e l l Valley B r i d g e i l l u s t r a l e s the e . v i * ' o u m e n l a l h a z a r d s , s i t e d i f f i c u l t i e s and i n s t Y u m e n t a t i o n p r o b l e m s which have to be o v e r c o m e in o r d e r to ~pply ndt in the f i e l d . Below, the t h r e e w e h l s lo be t e s t e d c~m be s e e n c l e a r l y on a g i r d e r . A c c e s s w¢~s aehie~,ed throu,~h the izole in the middle of the trapeziunz.

k

Construction The IrweLl Valley Bridge will carry traffic across the River Irwell on the M 62 Motorway at Clifton,near Bolton, Lancashire. The bridge will have the following characteristics: 200ft single span; 23 ° skew; clearhead above river of 65ft; 158ft between parapets. The road will rest on seven box girders of trapezoidal cross-section (Fig I). Each girder comprises four sections (two 45ft and two 55ft) which were prefabricated in Middlesborough. The joints were welded on site. The girders are m a d e from plate steel: the bottom flanges are 2in l~rD2:the top flanges are 7/sin BS15; the webs are i/2in BS15 (Fig 2). Welding electrodes were ESAB, O K unitrode which is a low-hydrogen type electrode. In the construction, there were two temporary splice welds, which were necessary for the launch of the girders over the river (Fig 3); the strength of these welds had to be sufficient to bear the tension and compression loads in this unusual m o d e of construction. N D T specifications

12ft t

1,1,

L'------~7/8 inBSl S /(top

flange)

2 in ND2 ( bottom flange) 8ft

A

The Non-Marine Department of Lloyd's, who were the inspectorate appointed by the Lancashire County Council for the shop fabrication and site welding of the bridge, carried out the following testing to the Council's specification: all top and bottom flange welds had to be 100°/otested by g a m m a radiography; web welds had to be 40% tested, except those on the two temporary splice welds which had to be 100°/otested by g a m m a radiography; all g a m m a radiography had to be done under floodlight at night for safety. NDT t e c h n i q u e s Two ndt t e c h n i q u e s w e r e used; g a m m a r a d i o g r a p h y and u l t r a s o n i c s . X - r a d i o g r a p h y was not a t t e m p t e d b e c a u s e the w e l d s w e r e i n a c c e s s i b l e to bulky a p p a r a t u s . G a m m a r a d i o g r a p h y was u s e d for all welds; for m o s t welds, a p o r t a b l e i r i d i u m - 1 9 2

n o n - d e s t r u c t i v e t e s t i n g May 1968

195

1000 PLUS 1000 (AMPS NOT ELEPHANTS)

THE

NEW

SONATEST

EMAG

1000÷1000

MAGNETIC

CRACK

DETECTOR C O M P E N S A T E D AC & DC O U T P U T S : A C C U R A T E O U T P U T I N D I C A T I O N : LOW V O L T A G E A C T U A T I O N : O V E R L O A D CUT OUT: 8" × 12" × 13"

sona|es| 196

non-destructive testing May 1968

48 Ibs.

£ 180

BEACON HOUSE, 113 KINGSWAY LONDON, W.C.2 CHANCERY 9211 (24 HOUR TEL-STOR)

ndtiir x

(610keV) s o u r c e (1.3 1.3ram, mounted on a s p e c i a l t r i p o d stand) was u s e d in an e n c l o s e d c o n t a i n e r method (Fig 4); f o r the two t e m p o r a r y s p l i c e welds, an open i r i d i u m - 1 9 2 s o u r c e was used, so that each of the n u m b e r e d s e c t i o n s (Fig 5) could be e x a m i n e d by one shot: 1, 2 by six lit l e n g t h s of film; 3, 4, 7 and 8 by s e v e n l f t lengths; 5, 6 by four l i t lengths. The m a x i m u m s t r e n g t h of the s o u r c e on s i t e was 6 . 5 C u r i e s . Kodax I n d u s t r e x D film was u s e d at a s o u r c e to film d i s tance of 20in for the bottom flanges; A ~ a - G e v a e r t Struct u r i x D7 film was u s e d at a s o u r c e to film d i s t a n c e of up to 24in for the top flanges and the webs. L e a d s c r e e n s w e r e used to cut out s t r a y radiation during the 1/2-4 hour e x p o s u r e periods.

Spent uranium or tungsten carbide shield

T e m p o r a r y s p l i c e s w e r e , in addition, c h e c k e d u l t r a s o n i c a l l y by the b a t t e r y o p e r a t e d Sonatest TE6A with s h e a r - w a v e 50 ° p r o b e s at 2.5MHz. The coupling was P o l y c e l l p a p e r - h a n g i n g paste.

20-214i

T e s t conditions The r e q u i r e d weld t e s t s c o v e r e d 420ft of flange w e l d s and 500ft of web welds. In addition, Radiological Inspection L a b o r a t o r i e s L i m i t e d conducted u l t r a s o n i c t e s t s on 96ft of t e m p o r a r y s p l i c e welds. Between 12 and 30 r a d i o g r a p h i c s h o t s w e r e obtained on e a c h night of i n s p e c t i o n (depending on the w e a t h e r which ;.;as poor throughout). Usually, the top and bottom f l a n g e s w e r e welded f i r s t and t e s t e d b e f o r e the w e b s w e r e welded and examined.

Plate steel

Film

4

1

2

Results

The r e s o l u t i o n of the g a m m a r a d i o g r a p h i c technique was b e t t e r than 2°/°, as m e a s u r e d by the ISO I m a g e Quality Indicator. In o v e r 900ft of welds, which w e r e e x a m i n e d r a d i o g r a p h i c a l l y in Ift s t r i p s , only one fault was d e t e c t e d . This fault was a c r a c k in a t e m p o r a r y s p l i c e weld which was also r e v e a l e d by the Sonatest TE6A. Thus, at the ndt stage, a f t e r the c o m p l e m e n t a r y d e s t r u c t i v e m e c h a n i c a l t e s t s , l e s s than 1% of w e l d s r e q u i r e d attention. This f a c t is a t r i b u t e to the high s t a n d a r d of welding a c h i e v e d and should r e a s s u r e p r o s p e c t i v e t r a v e l l e r s o v e r the Irwell Valley Bridge.

~Positions of radiographic / ~lp'm~ntelmdPs°rar Y /,

//

Acknowledgements W e wish to thank Mr. J. M. Dean, Acting County Surveyor and Bridge master for permission to publish this information; also Richard Costain (Civil Engineering) Limited for photographs; Dorman Long Limited the steelwork contractor, for

l

6

5

a r r a n g i n g the s i t e - v i s i t ; Welding E n g i n e e r of D o r m a n Long, for d e t a i l s of the w e l d s and testing; Mr Boden, D i r e c t o r of Radiological I n s p e c t i o n L a b o r a t o r i e s L i m i t e d , f o r d e t a i l s of the ndt t e c h n i q u e s .

NDT BY ULTRASOUND AT 100MHz ?

In ndt, the r a n g e of u l t r a s o n i c f r e q u e n c i e s is usually l e s s than 25MHz, but at this upper l i m i t the r e s o l u t i o n is about 0 . 2 5 m m which i s too c o a r s e for many applications. The a p p a r a t u s shown in Fig 6 is u s e d to i n v e s t i g a t e the e x t e n sion of the range to 100MHz, with a c o r r e s p o n d i n g i n c r e a s e in r e s o l u t i o n . The t r a n s d u c e r i s a s i n g l e - c r y s t a l CdS plate bonded to a q u a r t z r o d and p o l i s h e d down to the r e q u i r e d t h i c k n e s s . This t r a n s d u c e r is s u s p e n d e d in w a t e r through which the u l t r a s o n i c pulse t r a v e l s to the s t e e l s p e c i m e n . In Fig 6, the l a r g e r p u l s e on the o s c i l l o s c o p e s c r e e n r e p r e s e n t s the amplitude of the u l t r a s o n i c p u l s e on e m i s s i o n f r o m the t r a n s d u c e r ; the s m a l l e r p u l s e r e p r e s e n t s the amplitude of the u l t r a s o n i c p u l s e at the t r a n s d u c e r a f t e r r e f l e c t i o n f r o m the upper face of the s t e e l s p e c i m e n . T h e s e a m p l i tudes have been u s e d to e s t i m a t e the attenuation of I00MHz u l t r a s o n i c w a v e s in w a t e r , s i n c e the s m a l l e r pulse can be a l t e r e d by changing the d i s t a n c e b e t w e e n the t r a n s d u c e r and the s t e e l s p e c i m e n . As yet, t h e r e has not been suffi-

c i e n t r e s o l u t i o n to obtain s i g n a l s f r o m within the s t e e l s p e c i m e n , but r e s e a r c h continues. N o n d e s t r u c t i v e T e s t i n g C e n t r e , AERE, Harwell, Didcot, B e r k s h i r e , England (shown at The P h y s i c s Exhibitio~ 1968) n o n - d e s t r u c t i v e t e s t i n g May 1968

197