GB2031542A - Improvements in and relating to hoses - Google Patents

Abstract

A non-rigid hose whose walls comprise a strong carcass 12 enclosed in a flexible material 14 is provided with a rigid flange in at least two annular parts 16, 34 which when attached together constitute a jaw arranged to hold captive the carcass which enters it via a tapering section. A cylindrical bush 36 extending into the hose improves the connection between the hose and the flange. <IMAGE>

Description

SPECIFICATION Improvements in and relating to hoses This invention relates to non-rigid hoses, and in particular to those of large diameter and capable of operating at elevated pressure.

One important use of hoses of the type described in this specification is for loading and unloading marine tankers from a buoy at sea. Such a buoy generally employes two types of non-rigid hose one, floating, for use between the buoy and the tanker, and the other without buoyancy for use between a fixed sub-sea connection and the buoy. In such applications the hose often has a diameter of 400 to 600 mm or larger and must withstand pressures of more than 10 bar in addition to severe tensile and bending forces.

Typically, such hoses are made of rubber with multiple layers of steel or fabric reinforcement.

Additionally the hose is provided with a tough outer surface layer which is light- and sea water resistant and an inner layer which is resistant to attack by the products likely to be handled. Either end of each section is provided with a rigid flange which may be bonded and/or bolted to the walls of the hose.

As these hoses are difficult to make, each one generally comprises a number of relatively short sections which are connected together to provide the required length. Whilst much progress has been made in providing a satisfactory hose, its useful life is often governed by the relative weakness of the attachment of flanges to the walls of the hose, mainly due to the constant bending of the hose.

A very significant improvement to the connection between the flange and the hose walls was made in our patent no. 1.527.767 (K 5299/K 5254) which describes a rigid flange mounted on a non-rigid hose. The flange there is in two parts which, in use, are attached to hold the hose captive by means of its carcass or reinforcement which is clamped between the two parts. By providing a taper between the two parts at the entry of the carcass such a flange permitted the required flexibility between the flange and the hose whilst providing a very strong connection between them.

However, although much improved, the attachment of the flange is still often the most limiting factor in the life of the hose and the present invention seeks to improve the above mentioned flange connection still further.

In accordance with the invention a non-rigid hose whose walls comprise a strong carcass enclosed in a flexible material is provided with a rigid flange in at least two parts which when attached together constitute a jaw arranged to hold captive at least a part of the carcass which enters the said jaw via a tapering section, characterized in that the flange is provided with an annular bush extending into the hose to a distance of between 3/4 and 21/2 times the wall thickness of the hose further than the outer part of the flange.

The advantage of the bush is that in providing additional, but not excessive support on the inside of the hose it better prevents the hose from breaking away from the flange and also more uniformly transmits the bending forces on the hose to the flange and vice-versa.

As mentioned above the hose may or may not be provided with buoyancy, depending upon its destined use. In calculating the distance to which the bush extends into the hose past the outer element, no account should be taken of the additional wall thickness of the hose due alone to the added buoyancy material.

Normally the flange is bonded to the hose, for example by vulcanising the flexible material, which is generally rubber, to the flange which is generally in stainless steel. The provision of the bush within the hose helps to maintain this bonding intact much longer than previously and thus prevents exposure of the carcass material which may be susceptable to corrosion or attack, especially where the hose is used in sea water.

In order to provide an effective jaw on the flange the latter is generally made in at least two parts, namely a main body member which also comprises the flange itself and a clamping element. The carcass is conveniently bent radially outwardly to be clamped in the jaw formed between the body member and the clamping element.

The invention is particularly useful for relatively short hoses where bending of the hose can be relatively extreem.

In a preferred embodiment of the hose, its outer surface is protected by a layer of reinforced sea water- and ultra-violet light-resistant rubber. This provides a barrier against sea water ingression and the reinforcement acts as a crack arrestor and resists scuffing during use. This outer layer is sealingly attached, conveniently by mechanical means, to the flange and thus helps to protect the bond between the outer surface of the bush and the body of the hose.

The carcass of the hose, comprises a substantial reinforcement embedded in natural rubber with hoop or spiral internal and external reinforcementto prevent collapse from outside pressure and internal pressures.

The substantial reinforcement comprises a number of layers or plies of fabric or steel braid whose axis is arranged to be at an angle of approximately 55 to the centre line of the hose, alternate layers being opposite in pitch.

Usually, the hose is additionally provided with an inner reinforced layer of oil-resistant rubber. The light reinforcement in this layer is useful principally as a crack arrestor, particularly in cases where the hose is over-stretched or buckled.

An embodiment of a hose in accordance with the invention will now be described by way of example with reference to Figure 1 oftheaccompanying drawing which is a cross sectional side elevation of such a hose. Figure 2 shows a slightly different embodiment of a hose in accordance with the invention.

The hose whose walls comprise a carcass 12 enclosed in a natural rubber body 14 is provided with a stainless steel flange 16 which holds the hose captive by means of the carcass 12.

The carcass 12 consists of four layers of twined thin steel cables bonded to and embedded in the natural rubber of the body 14. Each cable in this case comprises seven smaller ones each consisting of four wires twisted together. Not only does this arrangement provide great strength but also a large surface for bonding with the natural rubber. The cables comprising each of the layers are wound at an angle of approximatey 55 to the hose axis, alterna timely to the right and to the left. This angle is chosen because under pressure loading it provides substantially equal strength in the hoop as well as in the axial direction. The layers are as far as possible equally spaced radially.Near to the flange it is usual to provide two additional intermediate layers of reinforcement 18, though often of smaller dimension than the main layers of the carcass.

Whilst natural rubber is largely preferred for the body 14 because of its good bonding characteristics with steel, styrene butadiene rubber can also be used with precaution.

Of the various forces which the hose is likely to encounter those of axial tension and bending are the most common. These can cause the carcass, because of its construction, either to expand or contract in diameter, and further reinforcement is added to counteract this tendency. On the inner side of the carcass steel hoops 20 are provided at intervals. On the outer side of the carcass these can be matched either by outer hoops (not present in the embodiments shown) of the same width as the inner hoops 20 and disposed in the same radial plane, or as shown, by a spiral wire 22 wound around the carcass and being in a plane substantially perpendicular to the axis of the hose.

On the outside of the natural rubber body 14 the hose is provided with an outer cover 24 of chloroprene or another sea- and sunlight-resistant rubber which has a woven rayon breaker ply 26 which is embedded in mid thickness of the cover. Ideally, the breaker ply should not take any force as its main purpose is to prevent crack propagation. The fibres of this layer ideally describe crossing helices on the hose body which due to their relative elasticity change shape as the hose is loaded or bent.

On the inner side of the natural rubber body 14 the hose has a neoprene, or similar oil-resistant liner 28.

Like the cover 24 the liner has a breaker ply 30 embedded in mid-thickness, which acts to prevent crack propogation.

The flange 16 comprises two main parts, namely, a main body member 32 and an annular clamping element 34. The body member comprises an annular bush 36 which is arranged to fit within the hose and to have approximately the same internal diameter as the latter, and a radially outwardly projecting flange 38 provided with a number of bolt holes 40 each provided with close-fitting sleeve 42. These sleeves 42 not only act to locate the clamping element 34 but also to prevent water from entering the space between the two parts. An additional rubber seal 44 set in an annular recess 46 between the two parts prevents water from entering this space from the periphery of the flange.

The hose is connected to the flange by laying the liner 26 over the inner sleeve 36 and bonding the two together. The end of the sleeve is transferred at 48 to prevent any sharp edge from cutting into the liner. At the inner end of the body member 32 the outer surface slopes outwardly at 50 at approximately 15 and then bends round and back on itself in a clamping zone 52. It is in this zone that a rounded annular projection 54 on the clamping element 34 forms a jaw which is arranged to received the gradually outwardly-bent carcass 12 and to hold it captive in the flange. The inner surface 54 of the annular element is tapered at an angle of 121/2 to produce a flared or funnelled entry to the jaw.

A watertight seal with the flange is finally made by attaching the outer cover 24 to the clamping element by means of screws 56.

The bush 36 projects into the hose to a sufficient distance to prevent it from bending at such a sharp angle near to the flange that the bonding between the hose and the flange could be broken or alternatively that the outer cover 24 could be torn loose from the flange. It has been found that for this to be so two criteria should be met. The first is that there should be the gradual taper leading up to the jaw, and the second is that the annular bush should extend into the hose to a distance dfrom the part of the flange supporting the outside of the hose equal to of at least 3/4 of the wall thickness tofthe hose itself. In the example shown, d = 11/2 t, which is considered to be the optimum. If however the distanced is too great on the other hand, say d > 3 t, the bush can have an adverse effect on the hose due to its rigidity over too great a distance in the region of a flange, which imposes excessive bending on the remainder of the hose, including very high local forces at the end of the bush.

Figure 2 is in al respects similar to figure 1 except for the attachment of the cover 24 and the liner 28 to the clamping element 34 and the body member 32 of the flange 16 respectively.

Unlike the arrangement in figure 1 the cover 34 is not mechanically attached to the clamping element 34. In additional, the liner 28 remains entirely on the inside of the flange member and in itself provided with an integral sealing joint 60 so that no product carried in the hose can come into contact with the flange. The body 14 of the hose and lining may be bonded to the flange as required.

Claims (8)

1. A non-rigid hose whose walls comprise a strong carcass enclosed in a flexible material provided with a rigid flange having an annular jaw which is arranged to hold captive at least a part of the carcass which enters the said jaw via a tapering section, charaterized in that the flange is provided with an annular bush which extends into the hose to a distance of between 3/4 and 21/2 wall thicknesses of the hose further than the outer part of the flange.

2. A hose as claimed in claim 1 in which the bush extends into the hose radially inside the majority of the thickness of the carcass.

3. A hose as claimed in claim 1 or 2 in which the annular part extends into the hose to a distance of between 1 and 2 wall thicknesses.

4. A hose as claimed in any preceding claims in which the annular part extends into the hose to a distance of 11/2 wall thicknesses.

5. A hose as claimed in any preceding claims in which at least a part of the carcass is bent outwardly to be held captive by the jaw.

6. A hose as claimed in any preceding claims in which its outer surface is protected by a cover which is sealingly attached to the flange.

7. A hose as claimed in any preceding claims in which the hose is provided with an internal liner which is bonded to the bush.

8. A non-rigid hose substantially as specifically described with reference to either figure 1 or figure 2 of the accompanying drawings.