Note: Descriptions are shown in the official language in which they were submitted.
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ir,vention relate~ to tubing, e~ ially tubing suitable
for conv~ying fluid~, either liquid or ga~eotls, whil~t mainta$ning
the t~peraturQ o~ the ~oll~eysd fluids sub~tantially constallt.
Such tubing i9, for exa~le, u~ed i~ the che~i~:al prcsce~sing
and p~troleum r~fining indtl~tri~3 :for conveying sa~ple,Q o~ fluid3
from procees lir~e~ or reaction ~e~els to ~3a~pling ~n~tr~nt~s s~ch
a~ chro~atrcgrap~e, ~pectrometera a~d pressure or ten~p~rature
sen~or~. It i8 nace3~ary that the ~luid ~a~ples taken ~ould be
Dai~tai~ed at a relative~ le~rated te ~ rature i~ order to keep
th~ Q~ity of t~e ~luid a~ low as pos~ible a~d also, in the ~a~e
of gase~, to e~s~re tha~ ~nden~atio~ doe~ ~ot occur. Typically
such tub~ng c~mpriBes a relativ~ly ~le~ible tubular line m~ber
made, for exa~ple, ~ro~ stainless ~teel, ~i~h i8 provided with
electrical heati~g wirea which are dispo~ed in engage~ent with the
tubular line ~ember, typically by laying t~e~ parallel or by
~rappi~ them helically about the line me~ber. Such a~ arraRgeme~t
:~ can also be used ae pro~ect~on against freezi~g.
The a~sembly formed by th~ tubular li~e ~e~b~r a~d its
a~ociated heatin~ ~lem~nt(q) is provided with i~sulation and a
: pr~t~ive oo~ering, as d~scribed, for ~xample, in U.S. Patent
~o. 3,355,572. The composite t~bing me~ber thus produc~d ha~
: pro~ed oatisfactory in ~a~y applicatio~s, ~ut the i~ulation u~ed
until ~ow has be~n e~tirely ~ati~ actory a~d, furtherm~re, ths
heati~g sl~ents used have ~ot, i~ all ca~e~, been able to meet
the require~ant~ of cartai~ spe~i~ic application~.
S~M~ARY OF THE I~V~IO~
The prese~t inve~tion provide~ a compoeite tubi~g membe~.
.: ccmprising
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(a) a tubular line mem~er,
(b) heating means disposed externally of said line member
and
(c) insulation comprising at least two layers, each of
which comprises foam material and, preferably,
reinforcing material.
At lea~t two layers within the insulation are preferably
in helically counter-wra~ed relationship, i.eO ~o that one layer
iB wra~ped in a sense opposite to that of the other, the present
inventîon ~ein~ based, _ter alia, on our ohservation that
especially suitable insulation for sampling line tu~es can be
obtained by helically counter-wrap~ing at least two layers of
foam material. Such a helically counter-wrapped configuration
ensures that the insulation rem~ins tight and free of lea~age
paths.
In some cases it may not be necessary or desirable to
provide separate reinforcing material. For example, certain
insulation matexials, e.g. polypro~ylene foam, have sufficient
~tructural integrity to be used without additional reinforcemen~
However, each layer will preferably comprise both a low
density foam material and reinforcing material so as to include both
i~ thermally insulating and reinforcin~ materials and the arrangement
~ will be such as to prevent the thermally insulating low densi~y
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foam material from being crushed by over-wrapped reinforcing
material. Thus the insulation prefera~ly comprises at least
two layers each which is formed from a thermally insulating
low density foam material and a reinforcing material, the
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; arrangement of the foam and reinforcing materials in the layers
and the arrangement o~ the layers heing such that each section of
the insulation comprises both foam material and reinforcing
material in over-wrapped relationship. Such an arrangement can
readily be obtained by helically counter-wrapping the layers,
especially i~ each layer contains the foam material and the
reinforcing material in side-by side relationship. However,
other arrangements may be used to take advantage of this aspect
of the present invention.
10In one preferred form of ~he present invention the layers
of the insulation are formed by helically wrapping a laminated tape
comprising a width of low density foam material and a width of high
density foam material. A further layer of laminated tape is then
wrapped helically in the opposite direction about the article so
~ormed to produce a final tubular insulating member, the low
; density foam material supplying the necessary thermal insulation
and the high density material providing the nec~ssary structural
integrity.
Of course, each layer of such insulation could ~e formed by
wrapping two separate tapes rather than a single laminated tape.
The foam material is typically a polyurethane although other
materials, e.g. polyethylene,polypropylene or rubber, may b~
employed.
By "low density material" there is herein meant material
having a density of not more than 41bs/cubic foot and by "high
density material" there is herein meant material ha~ing a density
of not less than 61b~/cubic foot. Prefera~ly the density of the
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low density materi~l lies in the range of frcm 1 to 21bs/cubic
foot and the density of the high density mater~al lies in the
range of from 6 to 101bs/cubic foot.
In another preferred embodiment of the present invention
the reinforcing material compriaes plastics rope or tubing, for
example, polypropylene or nylon rope which is helically wrapped
together with the low density foam material. Thus in this
embodiment each layer can be formed by first helically wrapping
low density tape and then, in the same sense, helically wrapping
the polypropylene rope. It may be advantageous, in other cases,
to wrap the low density foam material and the xope simultaneously
in side-by-side relationship.
It will be appreciated, that although two layers will in
general be sufficient to meet the insulation raquirements, in
some a~plications it may be a~propriate to use three or more layers,
es~ecially where flexibility o the composite tubing member is
relatively unimportant. In such cases, each adjacent pair of
layers will preferably be in helically-counter-wra~ped relation-
ship.
The insulation produced by wrap~ing the various layers may
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be finally~covered by an outer sheath of plas~ics material, e.g.
polyvinyl chloride or polyethylene, and i~ will be appreciated
that other materials may ~e included within the insulation of the
line member for specific purposes, for example it may be
appropriate to add a braid material, for example fibreglass braid
or tape, to provide high temperature thermal insulation.
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The heating means may comprise, for example, one or more
electrical heating wires wrappea helically about the tubular line
member and, ad~antageously, held in position by binder strands
made fxom nylon fibre or tape material. Alternatively, one or
more Or the heating wires may be arranged to run parallel to the
longitudinal axis of the tubular line member. However, in the
preferred forms of the presen-t invention the heating element
comprises a self-regulatine heating strip which increases its
electrical resistance as the temperature increases and which is
preferably provided with its own mechanical protection. An
especially suitable self heating strip which may be wrapped helically
around the tubular line member or which may be run parallel to
the longitudinal axis of the line member is that sold commercially
under the name "Auto-Trace" by Chemelex Inc., a subsidiary of
` Raychem Corporation, and which is described, for example, in
British Patents ~os. 1,449,261, 1,449~262 and 1,456,047.
Howe~er~ other heating means may be used in the present
invention, including for example non-electrical heating means,
e.g. a thin pipe through which steam or another heating fluid
is passed.
The thickness of the low density foam material and the
reinforcing material will vary according to the application but,
in general, the thickness of the material used in each layer will
lie in the range of from 1/8 inch to 3/8 inch gi~ing a total
thickness of at least 1/4 inch.
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It will be appreciated that the ins~lation u ed in ~he
present inve~ti~n can ea~ily be applied to the line memker and
it~ a~sociated heating means. ~ow~ver, i~ ~om~ cases, it ~ay be
ad~antageou~ to fonm a prefabricated two-layer~d insulatio~
memker into which the line m2mber may be pu3~ed or drawn to
~Gnm th~ ~inal compo8ite arti~le.
Figure 1 ~hows a fir~t ~orm o composite tubular article
: ~ a~cordance wit~ the pres~t inve~tion:
Figure 2 ~h~w~ a second for~ o~ ~ompo~ite tubular article
in ac¢ordance with the present invanti~:
Figure 3 is a cro~s-oection ta~n along the line 3-3
o~ Fig~re 1: and
Figure 4 3hows part of a haating el~me~t s~itable for
U3~ i~ the pr~sent i~ventio~.
I~ Figur~ 1 ~here i8 illustrated a compo~ite ~a~pli~g line 1
c~mpr~ g a ~ubular li~e me~r 2 made, for exa~pl~, ~ra~ ~ain-
les~ ~teel or a ~la~ticæ material su~h a pol~t~tra~l~or~ethyle~e
or ~yl~n, provld~d with an electrical heating element 3 secured
in po~itlo~ with relatio~ to the t~bular li~e member 2 by
tape 4 ~o t~at it occupies a positi~n s~b~ta~tially parallel
to the lo~sit~dinal axi3 0~ the tubular li~e ~e~ber 2
In accordance with the pre~e~t i~ention the a~s~mbl~ o~ the
line m~mber 2 and th~ heating ele~nt 3 i~ in~lated by
first wrappi~g a laminate~ tape 5 comp~ ng a ~idth 6
o~ lo~ dansity polyuretha~e ~oam and a ~acon~, ~ar~owe~,
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width 7 of high density poly~lrethane foam, about the assembly
and then wrapping a similar tape 8 over the wrapping 5 but
in an oppos.ite sense. The insulation so obtained is finally
protected by means of an outer plastics sheath 9.
Turning now to Figure 2 there is shown a somewhat similar
assembly 11 in which the tubular line member 12 is.provided with a
helically wound electrical heating element 13 held in position
by tape 1~. ~he assembly so produced is insulat.ed by means of a
helically wrapped tape 15 of low density polyurethane foam
. 10 reinorced by several windings 16 of polypropylene rope w}lich has
. been helically wrapped about the layer 15 in the same sense.
A second layer o~ the same construction is then wrapped in the
opposite sense over the first layer. Once again the insulation
is Pinally protected by means of an outer plastics sheath 17.
Finally, in Figure 4 there is shown the end of a heating
element suitable fox use in the present invention. This comprises
two spaced apart parallel electrodes 21 and 22 embedded in a
car~on-filled polymeric composition and protected by an insulating
layer 23 and a metal braid 24 tin some cases the metal braid may
-20 be omitted). Such a heating element is described, for exam~le,
: in aforementioned British Patents ~OSr 1,449,261, 1,449,262 and
1,456,047, and is especially suitable for uæ in the present
invention.
~ Whilst the present invention has been described with
: 25 specific reference to tubular samplin~ line memkers it will be
appreciated that it is àlso ap~licable to other fields and,
equall~, .;.t will be apprec;.ated that the word "tubular" as used
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herein does not limit the invention to hollow right cylindrical
members, but is in~ended to cover members of irregular and/or
varying cross-section as well as members having one or more
branches, such as Y-shaped, T-shaped and X-shaped members.
Further modifications and variations in accordance with
the present invention will be apparen~ to those skilled in the
art.
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