Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Th~s invention relates to a wrappinq ~tructure fo~
.~protectin~ pipe~, p~ticularly steel pipelines ~hicb may ~e '' -
~ub~ected to impaat by hard ob~ects,.for example rocko and ~ -
pe~bles. :
~t i~ well ~nown.that Jteel pipel$ne~, whether-buri d
~n the ground, or restinq on the ~urfac- of th ~ea-bed, c~n
. ~ be protectea with coating~-compos$t~ons or wrappinqJ. In or~e*
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' . .to prevent localiaed corro~ion occurring at.holas or tearJ $n
~ the~a protective coatinga or wrappings, cathodic protection
I0~ often employed a~ a ~econd line of defence. This cathod$c -
.- protect~on.involve~ placing'adiacent to the pipe an anodè of '
a.metal which is bigher than iron in the electroohemical Jer1e~,
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';~'' or~the impre~ioniof.electrical current. The cathodic : -
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- ''''-'~protact~on io normally only réquired when the protective
'~ 15 coatin~ or wrapping become~ d~maged, althouqh, of couroe..with
..~ ..a buriod or Jubmarine piEeline one ~cannot know whether thlJ
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. ~' ha~b-p;-nel. ~ . ' - ~.
.'~ - When a pipeline-pro~tected by a coating or'wrapping
laid in rooky terrain or a ~b- oil conta~n~ng sharp and-
abrasive aggregates, it i8 aes1rable to protect the protective
.. soating or wrapplng against damage by abrasion or impact withsuch roc~ or aharp aggregate by means of a barrier sufficiently
-robust to protect the coatin~ or wrapping againqt damage by
m~ such i~pact or ~bra d on. TS~J i~ clearly des~rable even thoug~
- 25 a cathodic protection may also be.provided, because qu~te
. . ~e w re damage may otherwise occur in the pipe laylng operat~on.
at the same time, the barrler must permit a system of cathodic
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protection to function by allowing the electrical current that is generated
to reach any areas of metal which are exposed as a result of localised
damage to the protective coating or wrapping which may, despite the barrier,
have occurred.
It is an aim of the invention to provide a wrapping structure which
may be used to provide such a barrier.
According to the present invention, there is provided a wrapping
structure for protecting a pipe to be laid below the ground or sea against
damage by abrasion or impact while allowing a cathodic protection system
for the pipe to function, the structure having a plurality of ribs and
a plurality of apertures between the ribs, the ribs having a height of
at least 0.2 cm perpendicular to the plane of the structure, the apertures
each having an area of up to 6.5 cm2 and together occupying from 40% to 90%
of the area of the structure, and the structure being of flexibie plastics
material and being elongate so as to be wrappable helically, or while extend-
ing longitudinally, around the pipe with the surfaces of the ribs which are
the parts of the structure in contact with the pipe being rounded and
lying in a generally cylindrical surface and the structure, when so wrapped,
offering an exterior discontinuous surface which is free of projections.
The wrapping structure is preferably made of a polymer. At least
the following polymers can be used: polyethylene, polypropylene, poly-
vinylidene chloride, polyvinylchloride, polychloroprene and synthetic and
natural rubbers can also be used.
It is particularly preferred for the wrapping structure to be of a
polymeric resilient material. A particular example of such a material which
is suitable is air entrained polyethylene.
The purpose of this preferred feature is to provide for the
wrapping structure to be better able to absorb the impact of rocks or other
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articles falling on the pipe, either when situated for use, or prior to
being located in the desired position, with the minimum displacement or
damage to the normally provided pipe wrap or the protective coating.
The ribs are rounded on one side of the structure. The ribs can be
provided to project on one side of the structure, the structure then includ-
ing a web in which the apertures are formed and which connects the ribs, the
ribs preferably being parallel to each other. Alternative embodiments
include two sets of parallel ribs, the ribs of the sets being inclined,
preferably at right angles to each other. In this case the web is not
essential and all ribs are rounded on the one side of the structure, the
other side being generally planar. The centre lines of the ribs preferably
lie in a single plane when the structure is laid flat, so that the rounded
surfaces thereof will also lie in a single plane, with the result that when
the structure is pulled tight on a pipe there are no projections to cut into
the previously applied wrappings thereon.
The structure is to be wrapped around a pipe, to protect the
normally provided coatings and wrappings, the rounded sides of the ribs
facing inwardly so that only a small proportion of the structure is in
physical contact with the pipe, or, more particularly, the exterior coating
thereon, thus using the minimum contact area. This means that the exterior
surface of the barrier is spaced from the pipe, so that sharp aggregate
will in general be kept well clear of the pipe even if it can penetrate
the apertures to some extent. The apertures will be quite small, up to
1 square inch (6.5 cms2) in area and preferably more than 0.4 cm2 in area,
and comprise 90% to 40%, preferably about 50% of the area of the struct~re.
After pipe laying, the apertures permit the passage of the electrical
current in a cathodic protection system.
The structure is preferably at least 36 inches (1 metre) wide,
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but narrower structures can be used if desired. Any length can be provided.
The ribs may be 1/8 to 1/4 inch, (0.3 to 0.6 cm) wide parallel to the general
plane of the structure and preferably have a maximum depth, perpendicular
to the structure of 3/8 inch ( 0.9 cms). They may be spaced apart trans-
versely of their length to give a gap about equal to their width. The
ribs are preferably parallel both for ease of formation and ease of
application, and may be continuous.
The wrapping structure of the invention may be helically wound
round a pipe, but if desired it can be wrapped round a pipe so that the
ribs are parallel with the axis of the pipe; in the latter case adjacent
edges of structure abut each other, and it can be kept in place by inter-
lacing the adjacent edges with a cord or rope or by the use of non-metallic
clips, or using self-locking straps or tapes provided, for instance, with a
ratchet mechanism.
The invention also provides a pipe laid or to be laid below the
ground or sea, the pipe being protected by a wrapping structure having a
plurality of ribs and a plurality of apertures between the ribs, the
structure being flexible and being wrapped around the pipe, with the
surfaces of the ribs which are the parts of the structure in contact
with the pipe lying in a generally cylindrical surface, and the apertures
being exteriorly uncovered.
The present invention will now be described, by way of example,
with reference to the accompanying drawings, wherein:
Figure 1 is a top-plan view of a portion of a length of a pipe
wrapping structure of the present invention;
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FigQr~ 2 iB a crooo,-~ectional view of the structure
dhown in Figure l;
,
. F1gures.3A and 3B s~ow two methods of fixinq of the.
pipe wrap~ing structure shown in Figure~ 1 and 2~ ana
. , Figure 4 ~how~ another form of pipe wrapping Jtructur ~,
.~ according to,the in~ention.
Referring'$nltially to Figure~ 1 nd 2 -~h- pipe
. . .''. '~tructure 10 comprises~an elongate web 11 with a plurality
.' , -' o~ long1tud~nally extending, laterally spacea p rallel'-roun~d
N : ,-,. ribs 12 on 0ne side. Intermediate the r.ibs 12, elongate
"....... , . Aper*ur.es i3 are proviaed in rows in the web.: Ao ohown ln ~ : -
'. ''' ~Figure'l the aperture~ 13 in ad~acent rows are s~agg-red. . ~
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~ with respect to'each other. ' ' . . -'
,,,." . . ~he wrapping ~ructure, whidh may be of a polymeric
. material'or other ~u~,able material, may be made.by -xtru-ion
: '. or moulding. .If.de~ired the elon~ate aper~ure~'13 may be
,--
: ~ ,formed by punchlnq.after the web 11 with the rib~ 12 integ~
therewith has been ~ormed.
. : -. The pipe wrapping ~tructure ~hown in Fiqures l and 2
. may be wrapF~d. helically about a pip 14'to be covere~ (F$gur
3B)-~or,may be arranged 80 that the ribs 12 extend generally
'; p~ llel to the longitudinal axi~ of the pipé 14 aa in'
.: Figure 3A. In either arrangement only the riba 12 cont~ct ~h
,~ur~ w e~of t~e pipe,14 with the web 11 apaced from the pi~
25," ' '~nd the area.of contact between #he wrappl~g ~tructur- lO.~nd
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-:'~' , the pipe 14 i8 kept to a n~n~ um. ~ , ,
~ In th-.case o~ the ~iPe w~4pping ~tructure lO b lng
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secured with the rib-q 12 parallel to the longitudinal axi~ of
~he pipe 14 the longitudinal edge~ of .the web, or we~s in
the case of two or more lengths of material being used, to
iyLrrouDd the pipe, are held in butting relationship ~ lac-~
;'l~;.which pa~s through the apertures adjacent to the'butt~ng.
edge~ of the web'or we~ or by meanq of non-metallic cl~p~ which .
.'encircle the wrapping structure 10 when ~n position about
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. ' ~ the pipe an~ clamp it to tbe pipe 14. An alternative i~ to uJe
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'.' :.- ; ~trap_ or tapes which self-lock, e.g. by be~ng provided'with a
10'......... ratchet mechaniQm. ' ~ . ............................ .. `
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In the embodimcnt ~b#wD in Figures 1 and 2, the'ribs
are 1/4 inch (0.6 cm) wide at their maximu~ width, exten~
- the same amount upwardly fro~ the web and are spaced
, ,, , :: approximately ~H ~1.25 cm) ketween centres., The apertures
'15,' , 1-3~are made ao large as po~sible consistent with maint~inin~.
,,. , ~he~,desired ~trength ~n the web and yet ~mall enough~'.~ en~uro
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, . ;~th ~raggregate-io kept clear of the pipe aurfac-. Thi~
. . 'ensures that if cathodic prDtection has to be used t,hen .the. ,`,
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`,', ''~ large nu~ber of aperture~ permit the paJ~age of the
2b ~ ! electrical current theretbrough. Typically the aperture~ ar- -
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, -,. 5/8~ ~1.6 cms~ long, 1/4~ ~.6 cm) wide and are ~eparat d
- , length,'wise by'}/8" (0.3 cm). The apertur-s thu~ compriJe
ust uDder half thei area of the weib.
Figure 4 shows an-alternative embodiment of wrapping
. ..'~i5'' ; ' ~tructure according..to the invention comprising two ~et~ o~
arallel ribe' ext~nding at right angles to one ,ano~her.
;' - -., ~ Rectangular apertures.(41) are accordingly provided in.~he
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structure, and it will be seen that the ribs- are rounded to
one side of the structure, this being the ~ide which will be
placed upon a pipe. The other side of the structure i8
substantially planar. The wrapping structure of thia- Figure
i~ again attached by clips, laces or straps ~ a pipe with the
rounded siaes of the ribs in contact therewith, or i~ helically
; nd on the pipe. In one embodi~ent accord~ng to Figure 4,
~the ribs have a maximum depth of about 0.4 cms, and~a w~dth
~ ~ - of 0.7, the apertures being i.2 cms long by 0.5 cms wid-.
io Although two alternative embodiments of the wrapping
~structure 10 have been descr~bea it should be undèrsbood that
the wrapping structure may take many other forms. In gener~l -
the wrapping structure has a small area of surface contact
~ ;~ with the pipe and at the same time provide~ a large ov-rall
passage for the flow of electrical current in the event
of cathodic protection having to be used.
~referably the wrapping structure will be of the
order of 36 lnche~ (approximotely 90 cms) wide. Any length
o structure can be provided. -
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