Hose system for high-ressure hydraulic system

The inventon relates to a hose system as indicated in the preamble of claim 1, that will eliminate the risk of an uncontrolled leakage in the event of hose failure.

Background

Hydraulic hoses are in many different connections used for the transport and pressurizing of hydraulic fluids, both in connection with machines, transport equipment and different kinds of operating devices. With the increase in pressure level, and the use of hydraulic systems in areas vulnerable to pollutions from hydraulic fluids, the problems and risks in connections with such systems are increasing. An application in which such systems are currently are widely used is the marine environment, where the spillage of hydraulic fluids may have severe consequences.

The installation of pressure sensors in hose systems, to allow for the detection of a pressure drop caused by hose failure and subsequent generation of a shut-off signal for valves and pumps, is known in the art. However, these efforts have not been able to prevent that hose failure resulting in the loss of hydraulic fluid and consequently inevitable pollution. In addition, such systems are expensive to the extent that they will not be usable for all purposes, e.g. in smaller construction engines and boats.

US patent 4,004,607 (Freese, 1977) discloses, for example, the arrangement of a shut-off valve at the inlet of a pressure conduit adapted for high pressure. The shut-off valve is actuated through a control conduit connected to the system to be protected. The implementation of this solution is complicated, involving unfortunate elements of uncertainty.

Several suggestions are known for the making of double hoses, to increase safety against leakage from hose failure.

International patent application WO 03044413 (Qutub Abe, 2003) discloses the arrangement of an double, outer hose over a pressure hose to increase the durability of the

hose arrangement. However, this will not suffice in preventing failure of the improved hose leading to leakage.

US patent application 2002017330 (Armenia et al., 2002) discloses a double-walled hose having an outlet in the outer hose for fluid from leakage of the inner hose. This solution provides for the possibility of collecting the fluid caused by the leakage. However, to be able to meet the demands of such a possibility the accommodations will be elaborate and it will thus not be realizable in several areas of possible use.

US patent 6,085,796 (Riga 2000) discloses a double-walled hose where the outer hose is able to collect leakages from the inner hose. This will increase the durability of the hose, but will not eliminate the risk of an unexpected leakage in the event of failure of the outer hose. Furthermore, this hose is designed as an integrated unit and will have to be replaced in its entirety in the event of a leakage in the inner hose.

US patent 6,032,699 (Cochran et al. 2000) discloses a double-walled hose, the annulus between the hoses being filled with some inert gas having a higher pressure than the working pressure of the inner hose. With the creation of holes in the inner hose gas will thus leak into the hose from the outer hose. This will be an inappropriate solution for hoses having a high working pressure.

US patent 6,550,499 (Pai 2003) discloses a double-walled hose having a leakage detector arranged within the annulus between the inner and outer hoses. In this case the hoses are tightly coupled together at the ends, which will require a special hose design. Furthermore, in the event of failure of such a double hose, replacing the entire hose system will be necessary.

None of the known hose systems have, used separately or in combinations, turned out to be fully satisfactory, neighter for high-risk, high-pressure systems offshore nor for less demanding purposes on vessels, in construction engines and the like.

Objects

The main object of the invention is to improve existing double-walled hose systems, so that they may be used for the prevention of leakages under difficult conditions of operation,

under high pressure and low accessability, for example in connection with subsea oil installations employing high-pressure hydraulic systems. It is also an object to create a hose system that will be more adequate, both in regard to manufacture and for use under different and less demanding applications, than known systems.

It is desirable that the hose system is, to as large an extent as possible is based on existing standard components. Furthermore, it will be desirable to be able to adopt the detection to different purposes. It will also be desirable to be able to make repairs in a simple and inexpensive manner.

• create an hydraulic system in which it will be possible to detect the types of failure most commonly encountered before they can cause any damages, so that it will be possible to perform maintenance and repairs to prevent a leakage from developing.

The invention

The invention is disclosed in claim 1. By the term "pressure transmitter" is meant any device capable of sensing a rise of pressure in the space between the working hose and the safety hose, and able to generate a signal indicating such a rise, which signal can then be observed by operating and/or maintenance personnel. This may include known pressure gauges, sensors delivering an electric signal to some warning and/or control device as well as simple optical transmitters which through an on/off-signal will give a warning that the safety hose is under increased pressure.

Through this solution several decisive advantages are acheived:

- the hose system may be constructed using available components or components that are easy to manucture

- a high level of safety against leakage of hydraulic fluid is acheived

- using simple means, the ability to make repairs before a leakage will occur is obtained

- during repairs the replacment of parts is limited to the leaking hoses

- repairs are therefore easy to make and can be done using standard replacment parts

- the extra space required, compared to similar known systems, will be insignificant.

The invention also includes the details disclosed in claims 2-6. The invention further includes a method for the repairing of a leaking hose as disclosed in claim 7. Additionally, the invention includes a fitting as disclosed in claim 8.

Further details in connection with the invention will be appearant from the description given below, of an example of the invention.

Example

The invention is described in more detail below with reference to the drawings, where Fig. 1 is a side view showing a transperant image of an end fitting included in one embodiment of the invention,

Fig, 2 is a exploded view showing the parts included in the end fitting of Fig. 1, and

Fig 3. is a side view of a joint for use in one embodiment of the invention.

Figs. 1 and 2 shows an end fitting for a hose system according to the invention. The hose system comprises, in this example, a working hose 11 arranged in a safety hose 12 having a diameter sufficiently large to be able to receive the working hose 11 , including parts that will be disclosed below. The working hose 11 and the safety hose 12 are connected by means of a bushing 13 adapted for coupling to a supply or reception unit 14 for hydraulic fluid, through the use of an opening 15.

The working hose 11 includes an hydraulic hose 16 connected to an end coupling 17 in a manner well known in the art. Similarity, the safety hose 12 includes an hydraulic hose 18 connected to an end coupling 19. It is necessary for the end coupling 19 of the safety hose 12 to have an internal diameter that allows for the passage of the end coupling 17 of the working hose 11.

The bushing 13 includes at one of its ends a threaded sleeve 20 for connection to the opening 15 and at the other end two concentric, threaded sleeves, an inner threaded sleeve 21 for connection to the end coupling 17 of the working hose 11, and an outer threaded sleeve 22 for connection to the end coupling 19 of the safety hose 12.

The bushing 13 includes a suitable element for a wrench, in this example a hex-nut 23 of a known type.

A closed annulus 24 communicating with the space 25 between the working hose 11 and the safety hose 12 is formed between the concentric threaded sleeves 21 and 22. The annulus 24 in the bushing includes a bore 26 extending radially to a collar nipple 27 which in turn, is connected through tubing 28, to a pressure gauge 29, The collar nipple 27 is arranged in a neck portion 35 of the bushing 13.

Initially, during assembly, the working hose 11 is tightly connected to the bushing 13. After the safety hose 12 has been pulled over the working hose, the other end of the working hose 11 may be connected to the supply or reception unit in a similar manner. This includes any working unit that needs to be supplied with hydraulic fluid under pressure for operation or control. The the two ends of the safety hose 12 may then be tightly connected to the bushings 13.

In the event of failure this procedure will be reversed. This means that a leaking working hose 11 can be pulled out of the safety hose 12 and replaced with a new working hose, or a repaired one, without having to replace other parts.

If under operation of the working hose 11 the leakage occurs, leaked hydraulic fluid will be caught in the safety hose 12, which will need to be designed to be able to withstand the working pressure, at least during a time period sufficiently long to allow for the disconnection of the hose system. The pressure gauge 29 will allow monitoring or operational personnel to observe the presence of a leak and start planning and performing shutdown and repairs. This can be done in a way that will reduce the losses during shutdown. In reality, the invention allows for the possibility of extending the time of operation, so that repairs can be made in connection with ordinary maintenance or some planned shutdown.

Fig. 3 illustrates a bushing 30 that may be used for the creation of joints in connection with the hose system according to the invention. The bushing 30 includes ends similar to the hose-connecting parts of the bushing 13 for joining the ends of the working hose 11 and safety hose 12. A collar nipple 32, in a neck part 34, is arranged on one side of the nut 31

for the provision of a pressure gauge, and the two annular spaces are connected to an axially extending channel 33 for the transfer of leaked hydraulic fluids.

The invention may be modified in different ways, especially with regard to the arrangment of the leakage warning. Instead of a pressure gauge that reacts on the hydraulic fluid that might have leaked from the working hose 11 , a sensor or a pressure transmitter outputting an electric signal that may be suitably communicated to some reception point for manual or automatic monitoring may be arranged in the bore 26. Automatic monitoring may involve some form of signalling in addition to the control of an operational system that is able to stop the supply of hydraulic fluid to the working hose 11.

In an alternative embodiment a simple transmitter may be installed in the bore 26, providing a visual signal indicating the presence of a leak having pressurized the safety hose. In many cases, e.g. in connection with construction engines, such a transmitter which is checked during routine checks and maintenance may suffice.

The invention may also be applied in combination with a monitoring of the amount of hydraulic fluid present in the system which will be able to detect a complete hose failure and loss of hydraulic fluid.

Repairs of a hose system according to the invention, in the event of a leak, will be made as follows:

- The safety hose is disconnected at both ends.

- Leaked fluids are drained from the safety hose. - The working hose is disconnected at both ends.

- The damaged working hose 11 is pulled out of the safety hose.

- A replacement working hose is pulled through the safety hose.

- The new working hose is connected through, its end couplings.

- The safety hose is connected through its end couplings. This replacement may be made during an ordinary shut-down of the hydraulic system. In this way repairs of the hose system, and thus the hydraulic system, in the event of some working hose leakage, may be performed during ordinary maintenance work, without resorting to an extraordinary shut-down.

To be able to disconnect the working hose, the safety hose already having been disconnected, it may be necessary to make the working hose a few centimeters longer than the safety hose.

In an alternative embodiment the axially extending channel in the bushing 30 is omitted for the benefit of a pressure sensor at both ends. In this way two parts of a larger system may be monitored separately.