GB2138917A

GB2138917A - Flexible hose

Info

Publication number: GB2138917A
Application number: GB8410645A
Authority: GB
Inventors: Andrew Peter David Cox
Original assignee: Dunlop Ltd
Current assignee: Dunlop Ltd
Priority date: 1983-04-27
Filing date: 1984-04-26
Publication date: 1984-10-31
Also published as: GB2138917B; GB8410645D0

Abstract

The invention relates to dual carcass type hose of a kind which may be used under water and which comprises a leak detector 4 mounted externally of the hose to detect any fluid leakage through an inner 1 of the two carcasses 1, 2. The leak detector 4 communicates with the hose via a fluid passage 9 and to enable in situ removal or installation of a leak detector without ingress of water to between the main and secondary carcasses valve means 11 is provided in said fluid passage. Preferably the fluid passage is provided with a one-way valve to prevent flow of fluid in a direction from the valve means to the hose. <IMAGE>

Description

SPECIFICATION Improvements in or relating to flexible hose This invention concerns improvements in or relating to flexible hose and in particularto flexible hose of the type comprising a main fluid retaining carcass and a secondary fluid retaining carcass enclosing at least part of the length ofthe main carcass to prevent escape offluid leaking through the main carcass.

Flexible hose of the type referred to above is particularly usefulfortransporting fluids the escape of which would constitute a severe health or safety hazard and is especially suited to applications where the hose is required to withstand a considerable amountofflexing in use, rough handling during connecting operations and severe weathering,for example as may occur when the hose is used to transport oil from a tanker moored offshore to an installation onshore.

Although the secondary carcass may be constructed to provide a load-bearing capability sufficient to allow operation ofthe hose to continue unaffected should fluid leakfrom the main carcass, it is desirable to provide a means of detecting such leakage so that the damaged hose may be replaced before failure of the secondary carcass occurs.

In our UK Patent Publication No. 17480 there is described a flexible hose of the type referred to above provided with a leak detector mounted externally of the hose, preferably on an end fitting to which the hose is connected. Fluid leaking from the main carcass passes to or pressurises the leak detector which is operable to generate a warning signal when the pressure ofthe leaked fluid exceeds a predetermined value.

The present invention is directed to an improvement in the flexible hose described in our UK patent publication no 2117480 and comprises the provision, in the fluid passage for connecting an externally mounted leak detectorto the hose, of valve means operable to isolate the leakdetectorfrom the hose thereby enabling a leak detectorto be removed or installed with the hose in situ.

The invention will now be described in more detail, byway of example only, with reference to the accompanying schematic drawing in which the single figure is a cross-section of one end of a flexible hose assembly according to the present invention.

The hose assembly shown in the accompanying drawing comprises a flexible hose 11 having a main fluid retaining carcass 1 and a secondary fluid retaining carcass 2 surrounding the main carcass 1 overthe whole length thereof, a respective end fitting 3 at each end of the hose 11 to which the main and secondary carcasses 1 and 2 are secured and a respective leakdetector4 mounted on each end fitting for detecting fluid leaking from the main carcass 1.

The main and secondary carcasses 1 and 2 each comprise an inner liner, a reinforcement structure and an outercover, the outer cover of the secondary carcass 2 forming the outer cover ofthe hose. The reinforcement structures ofthe main and secondary carcasses are both constructed to be capable of withstanding the operating pressure of fluid transported through the hose independently of one another so that in the event of the main carcass failing the presence of the secondary carcass will allowthe hose to continue operation. Forfurther details of the construction of the hose the reader is directed to our UK Patent Publication No 2117479.

The end fitting 3 comprises a nipple portion 5 received within the bore of the hose and an end flange portion 6forsecuring the hose assemblyto a successive hose assembly orto a fixed fluid inlet/ outlet. The radially outer surface of the nipple portion 5 is provided with five axially spaced ribs 7a, b, c, dand e and the main carcass 1 engages the firstthree ribs 7a, band c remote from the end flange 6 and abuts against the fourth rib 7d. The secondary carcass 2 engages the fourth and fifth ribs 7dand 7e.

The fourth rib 7disformed with a continuous annular groove 8 in the radially outer surface thereof.

Groove 8 leads via a bore (not shown) internal of the rib 7dto an axially extending small bore steel tube 9 which in turn leads to the leak detector4 mounted externally ofthe hose on the end fitting 3 by means of a bracket 10. Fluid leaking from the main carcass 1 is retained by the secondary carcass 2 and flows along the length of the hose between the carcasses 1 and 2to either end fitting where it enters groove 8 and flows via tube 9 to the associated leak detector 4which is operable in response to the pressure of the leaked fluid to generate a warning signal. Forfurther details ofthe construction of the leak detector 4 the reader is directed to our UK Patent Publication No.2117480.

In accordance with the present invention the steel tube 9 is connected to the leak detector 4via a one-way valve 11 and a short length (ie length less than the length of tube 9) of flexible tube 12 releasably secured tothevalve 11.Thevalve 11 mounted on an end of the tube9 allowsfluidtoflowfrom thetube9tothe leak detector 4 but prevents the flow of fluid in the reverse direction. Accordingly the leak detector 4 may be removed by disconnecting tube 12 from the valve 11 and a replacement leak detector fitted with the hose in situ, and this replacement may be effected even when the hose forms part of a submerged hose-line because reverse flow offluid into the tube 9 is prevented.

Itwill be appreciated from theforegoing that the provision ofthe one-way valve in thatfluid passage for connectingaleakdetectortothehoseenablesa leak detectorto be removed or installed without having to close down the entire hose-line in which the hose is incorporated, thus contributing to a saving in operating costs.

The one-way valve 11 may be of any known construction. Alternatively the one-way valve 11 may be replaced by an on/offvalve which may likewise be of any known construction.

Preferably additional valve means (not shown), such as an on/offvalve, is provided in the flexible tube 12 near to that end ofthetube which is releasably securableto the one-way valve 11. This valve may be closed priorto removal of the leak detector so as to stop water or otherfluid flowing through the flexible tube to the leak detector in the case of underwater installations. Likewise the valve preferably is closed during installation of a leak detector and opened only when tube 12 has been connectedto valve 11. Accordingly when installing the leak detector under watertheflow of sea water into tube 12 may be avoided.

Particularly, but not necessarily only, in constructions where the valve means 11 if an on/offvalve and no additional valve means is provided in the passage between the valve means 11 and the leak detector, the volume offluid passage between the valve means and leak detector is less than one half and more preferably less than one quarter ofthevolume of the fluid passage between the valve means and hose.

Although the invention has been described above as particularly suitable for hose of a kind installed to operate underwater, it is to beunderstoodthatthe invention may be applied also to hose used in other situations, such asfloating hose, or at land based sites where ingress of foreign matter into the fluid passage between the hose and detector is to be avoided.

Claims

1. Aflexible hose assembly comprising a hose having a main fluid retaining carcass and a secondary fluid retaining carcass enclosing at least part ofthe length ofthe main carcass to prevent escape offluid leaking through the main carcass, a fluid passage for fluid communication between said hose and a leak detector mounted externally of the hose, and valve means provided within said fluid passage and operableto isolatethe leakdetectorfrom the hose.

2. Aflexible hose assembly according to claim 1 wherein the valve means is operable to prevent flow of fluid in a direction from the valve means to the hose.

3. Aflexible hose assembly according to claim 1 or claim 2wherein the valve means is a one-way valve.

4. Aflexible hose assembly according to claim 1 or claim 2 wherein the valve means comprises an on-off valve.

5. Aflexible hose assembly according to anyone ofthe preceding claims wherein said fluid passage extends to an end region of the hose.

6. Aflexible hose assembly according to any one ofthe preceding claims wherein the hose comprises an end fitting to which a leak detector may be mounted in fluid communication with said fluid passage.

7. Aflexible hose assembly according to claim 6 wherein the end fitting comprises a nipple portion received within the bore of the hose, the radially outer surface of said nipple portion being provided with at least one annular rib having a continuous annular groove formed in the radially outer surface of the rib and arranged in communication with an end of said fluid passage.

8. Aflexible hose assembly according to any one ofthe preceding claims and arranged in combination with a leakdetectorsuchthatthe length of fluid passage between the valve means and hose is greater than the length of the fluid passage between the valve means and leak detector.

9. Aflexible hose assembly according to any one ofthe preceding claims and arranged in combination with a leak detector such thatthevolume of fluid passage between the valve means and leak detector is less than one nalf and preferably less than one quarter ofthevolumeofthefluid passage between the valve means and hose.

10. Aflexible hose assembly according to any one ofthe preceding claims wherein each end ofthe hose is provided with a respective end fitting and leak detector in fluid communication with an end of the hose.

11. Aflexible hose according to any one ofthe preceding claims wherein between said valve means and the leak detectorthere is provided additional valve means.

12. Aflexible hose according to claim 11 wherein said additional valve means comprises an on/off valve.

13. Aflexible hose assembly constructed and arranged substantially as herein before cfescribed with reference to the accompanying drawing.