Note: Descriptions are shown in the official language in which they were submitted.
CA 02591680 2007-07-06
FEEDTHROUGH FIBER STRAIN RELIEF
BACKGROUND OF THE INVENTION
Field of the Invention
Embodiments of the invention relate to devices having feedthroughs for optical
waveguides, and more particularly, to hermetically sealed wellhead outlets
with
feedthroughs that are suitable for use in high pressure, high temperature,
and/or other
harsh environments.
Background Art
In many industries and applications, there exists a need to have small
diameter
wires or optical waveguides penetrate a partition such as a wall, bulkhead, or
wellhead
outlet, wherein a high fluid or gas differential pressure can exist across a
feedtrough
device in the partition. Furthermore, one or both sides of the feedthrough
device may
be subjected to high temperatures and other harsh environmental conditions,
such as
corrosive or volatile gas, fluids and other materials. For example, optical
sensors,
particularly sensors for use in bulkheads or wellhead outlets, oil and gas
exploration
and production, can require use of a feedthrough device that can seal an
optical
waveguide at pressures of 20,000 psi and above, and temperatures of 150 C to
250
C. The welihead outlets can include a feedthrough where an optical waveguide
is
concentrically located within a cavity in a housing, and the resulting annular
space is
filled with a suitable sealant. U.S. Patent No. 6,526,212, issued February 25,
2003,
describes in detail an exemplary feedthrough for installation within a
bulkhead.
There exist several challenges associated with constructing a feedthrough
device and fiber management system for use, for example, in a wellhead outlet.
One of
these challenges relates to damage and breakage of the fiber at a point where
the fiber
enters and exits the feedthrough device. The small size of the fiber and the
brittle
nature of glass materials of the fiber generally make any stress points along
the fiber
particularly susceptible to damage. For example, damage to the fiber at a
stress point
1
CA 02591680 2007-07-06
where the fiber exits the feedthrough into a low pressure chamber of the
welihead outlet
can occur due to a significant stress concentration at that location.
Accordingly,
movement of the fiber at this stress point as can occur during handling of the
wellhead
outlet potentially leads to damage of the fiber. Further, the fact that the
fiber is rigidly
held on one side of the stress point and is free on the other side of the
stress point
within the low pressure chamber makes the fiber susceptible to damage at the
stress
point due to micro-bending.
While it is typically desirable to have a length of the fiber extending from
the
feedthrough for purposes such as splicing, any excess fiber extending from the
feedthrough presents storage issues within the wellhead outlet. For example,
excess
fiber disposed within the low pressure chamber can be disorderly such that the
likelihood of damage to the fiber during handling of the wellhead outlet is
high,
particularly at the stress point discussed above. The disordered arrangement
of the
fiber within the low pressure chamber permits micro-bends along the length of
the fiber
extending from the feedthrough and can enable the fiber to become pinched
during final
assembly of the wellhead outlet such as when a cap is inserted on the low
pressure
chamber.
Therefore, embodiments of the invention provide optical waveguide feedthrough
assemblies and fiber management systems, and methods of making such
assemblies,
which overcome one or more of the above-described drawbacks and disadvantages
of
the prior art.
SUMMARY OF THE INVENTION
Embodiments of the invention generally relate to method and apparatus for
feeding on optical waveguide through a partition device, such as a bulkhead of
a
wellhead outlet. For some embodiments, the wellhead outlet includes a first
chamber
having a first port, a second chamber having a second port connected by a path
to the
first port for feeding an optical waveguide through to the first chamber, and
a strain
relief member coupled with the first chamber to limit motion of the optical
waveguide at
2
CA 02591680 2007-07-06
or near the first port. The strain relief member can be a rigid curved tube
coupled to the
first port and/or a fiber management member providing one or more fiber
retention
pathways.
BRIEF DESCRIPTION OF THE DRAWINGS
So that the manner in which the above recited features of the present
invention
can be understood in detail, a more particular description of the invention,
briefly
summarized above, may be had by reference to embodiments, some of which are
illustrated in the appended drawings. It is to be noted, however, that the
appended
drawings illustrate only typical embodiments of this invention and are
therefore not to
be considered limiting of its scope, for the invention may admit to other
equally effective
embodiments.
Figure 1A is a view inside a first chamber of a wellhead outlet showing a
rigid
curved tube extending from one of three ports into the first chamber and
having a fiber
therein.
Figure 1 B is a cross sectional view of a strain relief member in accordance
with
the present invention.
Figure 2 is a view inside a first chamber of an alternative wellhead outlet
illustrating a fiber extending from one of three ports into the first chamber
and along a
fiber retention pathway of a fiber management member.
Figure 3 is a cross-section view of the wellhead outlet in Figure 2 showing an
internal cover disposed between a cap of the first chamber and the fiber
management
member.
DETAILED DESCRIPTION
Embodiments of the invention generally relate to a mechanism for feeding an
optical waveguide through a partition of a device such as that of a wellhead
outlet that
inc(udes two separate chambers. A passage between the two chambers defines
ports
within each chamber for feeding the optical waveguide between the two
chambers.
3
CA 02591680 2007-07-06
U.S. Patent No. 6,526,212, issued February 25, 2003, describes an exemplary
feedthrough that can be used within a bulkhead if a wellhead outlet according
to
embodiments of the invention described below. Embodiments will be described
with
reference to wellhead outlets as a particular, but not limiting, application
example in
order to facilitate understanding. However, those skilled in the art will
recognize that
the strain relief mechanism and fiber management system described herein may
be
used to advantage in a wide variety of other applications, for example, where
fiber is
routed between two chambers using a rigid feedthrough.
Figure 1A shows an inside of a first chamber 101 of a wellhead outlet 100. A
first chamber cap (not shown) covers the first chamber 101 upon further
assembly of
the wellhead outlet 100. The wellhead outlet 100 includes a rigid curved tube
102
(shown transparent) extending from a port 106 into the first chamber 101. The
rigid
curved tube 102 encompasses a fiber 104 therein and directs the fiber 104 from
the
port 106 while limiting motion of the fiber 104 at or near the port 106.
The tube 102 may be made of any suitable rigid or semi-rigid material, capable
of guiding the fiber 104 as it exits into a chamber. The tube 102 may also be
affixed or
coupled to the port by any suitable means (e.g., pressed on, threaded on,
attached by
adhesive etc.). For some embodiments, as illustrated in Figure 113, the tube
102 may
be formed by attaching a flexible (e.g., Teflon) protective sheath 132 to a
rigid metal
tube 134 via heat-shrink elements 136 and 138. Small amounts of epoxy may be
disposed between the heat-shrink elements 136 and the sheath 132 to prevent
relative
motion therebetween. In this configuration, the tube 102 may then be attached
to the
feedthrough 112 (shown in Figure 1A) via a weld.
While the wellhead outlet 100 shown has two additional ports 108, 110 spaced
from the port 106 having the fiber 104 fed through, any of the devices
disclosed herein
can provide a single port or any number of ports for feeding the fiber through
the
device. In general, a path through the wellhead outlet 100 couples the ports
106, 108,
110 to respective ports of a second chamber (see, Figure 3). For some
embodiments,
the first chamber 101 defines an area of low pressure relative to an area of
high
4
CA 02591680 2007-07-06
pressure defined by the second chamber. Those skilled in the art will
recognize that,
while not shown, for some embodiments, the strain relief member and techniques
described herein may also be applied to a waveguide portion extending into the
second
(high pressure) chamber. Furthermore, the fiber 104 can be sealed within the
port 106
or the path by a feedthrough 112 such that the wellhead outlet 100 separates
these
pressures.
Like the port 106, the two additional ports 108, 110 can include their own
rigid
curved tubes and fibers after further assembly of the wellhead outlet 100,
which is not
shown. For some embodiments, the fiber 104 can be a single waveguide or
multiple
waveguides. Accordingly, each of the ports 106, 108, 110 enables feeding one
or more
optical waveguides through the wellhead outlet 100 to the second chamber.
During assembly of the wellhead outlet 100, the tube 102 threads onto the
fiber
104 and is positioned proximate the port 106. If the feedthrough 112 is
present, an end
of the tube 102 can affix to an end of the feedthrough 112, such as by using a
curable
adhesive. For other embodiments, the tube 102 affixes directly to the port 106
or an
adjacent portion of the first chamber 101.
Rigidity (or semi-rigidity) of the tube 102 substantially eliminates movement
of
the fiber 104 at a stress point where the fiber 104 exits the port 106 or
feedthrough 112.
Additionally, the tube 102 guides the fiber 104 along a gradual bend out of
the port 106
and along a perimeter of the wellhead outlet 100. Optionally, the tube 102 may
further
guide the fiber 104 into a pathway of a fiber management member, which is
described
below. Therefore, the tube 102 provides one example of a strain relief member
since
the tube 102 protects the fiber 104 at the stress point, thereby substantially
eliminating
the possibility of damage to the fiber 104 at the stress point during
handling.
Figure 2 illustrates an inside of a first chamber 201 of an alternative
wellhead
outlet 200 having a fiber management member 202. The fiber management member
202 provides fiber retention pathways within the first chamber 201 for a
length of a fiber
204 extending from a port 206 into the first chamber 201. For some
embodiments, the
fiber management member 202 defines a generally planar member disposable
within
5
CA 02591680 2007-07-06
the first chamber 201 and having an outer diameter portion extending toward
the
perimeter of the first chamber 201. Openings (e.g., cut outs 213) in the fiber
management member 202 can allow the fiber 204 and any other fibers (not shown)
extending from optional ports such as additional ports 208, 210 to pass from a
feedthrough 212 to a face of the fiber management member 202 where the fiber
204 is
to be organized.
Protrusions 203 on the outer diameter portions of the fiber management member
202 provide a surface for wrapping the fiber 204 around. Thus, the fiber 204
remains
orderly, with minimum bending, and within an area between an inner diameter of
the
first chamber 201 and an outer diameter of the protrusions 203. In addition,
the guiding
of the fiber 204 from the port 206 by the fiber management member 202 prevents
micro-bending and otherwise stabilizes the fiber 204 at the stress point where
the fiber
exits the feedthrough 212 or port 206. Therefore, the fiber management member
202
provides another example of a strain relief member.
While not shown, one skilled in the art will recognize that the strain relief
member
102 described above with reference to Figures 1A and 1B may also be
incorporated
into the wellhead outlet 200 shown in Figure 2. For some embodiments, such a
strain
relief member may guide an optical waveguide extending from a feedthrough 212
into
the first chamber up to the outer diameter of the fiber management member 202.
Figure 3 shows a cross-section of the wellhead outlet 200 after assembly with
an
internal cover 300 disposed between a cap 302 of the first chamber 301 and the
fiber
management member 202. As referenced above with respect to the general
structure
of a wellhead outlet, Figure 3 also illustrates a path 304 through the
wellhead outlet 200
that connects the port 206 of the first chamber 201 with a port 306 of a
second chamber
308. The cover 300 assists in fiber management within the first chamber 201 by
further
surrounding the fiber 204 wrapped on the fiber management member 202.
Accordingly,
the cover 300 prevents the possibility of the fiber 204 being pinched during
insertion of
the cap 302 onto the first chamber 201.
6
CA 02591680 2007-07-06
While the foregoing is directed to embodiments of the present invention, other
and further embodiments of the invention may be devised without departing from
the
basic scope thereof, and the scope thereof is determined by the claims that
follow.
7
