The invention is particularly applicable to a coupling for connecting pipework used in the transportation of hydrogen fluoride (HF). HF is a highly corrosive and harmful substance usually in a gaseous form but it can also exist in an aqueous form.

HF is produced in large quantities in industrial chemical plants and is usually then held within tanks. The HF may be transferred from a tank by means of pipework connected to the tank. In order to transport the HF from a plant to for example a customer, it is necessary to form a connection between a tank, and another container such as a bulk transport tanker which will be used to deliver the HF to the customer. In this respect it is usual to connect the pipework from the tank to a filling/discharge line connectable to the bulk transport container in such a way that the connection is fluid tight in order to avoid escape of harmful HF into the atmosphere.

Because of the harmful nature of HF, it is necessary for an operator who is effecting the coupling to wear full personnel protection equipment. This type of equipment includes an air-fed hood, and heavy overall body protection. This means that it is not easy for such an operator to accurately position and tighten couplings which incorporate intricate fastening mechanisms since the operator will be wearing bulky gloves.

According to a first aspect of the present invention there is provided a coupling device for connecting a first conduit to a second conduit, the coupling device comprising: a first, sleeve portion sealingly attachable to the first conduit to form a female connection portion; a second, protruding portion sealingly attachable to the second conduit to form a male connection portion, the second, protruding portion and the first, sleeve portion being sealingly engageable with one another; and a coupling portion adapted to form a connection between the first, sleeve portion and the second, protruding portion thereby to form a fluid tight connection between the first and second conduits, characterised in that the coupling device further comprises at least one elongate member extending outwardly from the coupling portion.

Preferably the coupling portion is a coupling nut having an inner wall and an outer wall, the inner wall being formed with a thread that is engageable with a complementary thread formed on one of the aforesaid sleeve portions.

In use the first and second conduits are positionable within the coupling nut, and are sealingly connected to one another by tightening the coupling nut.

The coupling nut may be tightened in any convenient way but preferably a spanner is used to engage with the coupling nut to rotate it relative to the first and second conduits.

The at least one elongate locating member acts as a means to locate the spanner or other apparatus used to tighten the coupling nut. The spanner is adapted to grip around the external wall of the coupling nut and also to engage with the at least one elongate locating member. The spanner is thus

locked in place on the coupling nut. This arrangement allows the spanner to be operated more easily.

Preferably the coupling device comprises three elongate locating members positioned on the external wall of the coupling nut at substantially equally spaced apart intervals.

The spanner is adapted to engage with each of the three elongate locating members and with the second sleeve portion in order to quickly and effectively to tighten the nut relative to the first and second conduit.

The second, protruding portion and second conduit together define an elongate spigot. The spigot enables an operator easily to locate the male connection portion within the female connection portion, even when the operator is wearing cumbersome all-over body protection.

The dimensions of the male and female connection portions are such that there is a very narrow clearance between the connection portions once the first, sleeve portion and the second, protruding portion have engaged with one another. This reduces the effect of side-loads which means that, when the coupling nut is tightened, there are less likely to be undesirable shear forces exerted on the coupling. Such shear forces could if created weaken the coupling device.

Preferably, the radial clearance between the male and female connection portions will be between 0. 1mm and 0.25mm, although other ranges of clearance may be appropriate in certain circumstances. Optimum clearances will of course depend on the dimensions of the male and female portions.

Preferably, a sealed joint is formed between the first and second sleeve

members by means of a gasket having serrated edges in areas of contact between the gasket and either the first sleeve member or the second sleeve member. The serrated edges serve to strengthen the join between the first and second sleeve members.

Advantageously the thread formed on the inner wall of the nut is a two and a half inch British Standard Whitworth thread having a thread pitch of five threads per inch.

According to a second aspect of the present invention there is provided a coupling device for connecting a first conduit to a second conduit, the coupling device comprising:- a first, sleeve portion sealingly attachable to the first conduit to form a female connection portion; a second, protruding portion sealingly attachable to the second conduit to form a male connection portion and including, formed on an outer surface thereof, a first thread which is a two and half inch British Standard Whitworth thread having a thread pitch of five threads per inch, the second, protruding portion and the first, sleeve portion being sealingly engageable with one another; and a coupling portion adapted to form a connection between the first, sleeve portion and the second, protruding portion thereby to form a fluid tight connection between the first and second conduits, characterised in that the coupling portion comprises a coupling nut having an outer wall and an inner wall, the inner wall being formed with a second thread which is a two and half inch British Standard Whitworth thread having a thread pitch of five threads per inch that is threadedly engageable with the said first thread.

According to a third aspect of the present invention there is provided apparatus adapted to engage with a coupling device according to the first

aspect of the present invention to effect a fluid-tight seal between the first conduit and the second conduit, the apparatus having an arm, and a head attached to the arm, the head comprising a coupling portion receiving means for receiving the coupling portion, and at least one second receiving means for receiving the at least one elongate locating member formed on the outer wall of the coupling portion.

Preferably, the apparatus is in the form of a spanner.

Conveniently the apparatus includes a torque indicator capable of indicating the torque generated by use of the apparatus when the head is engaged with the coupling device.

In use, an operator may use the apparatus, that preferably is in the form of a spanner, to tighten the coupling portion and thus form a fluid tight seal between the first conduit and the second conduit. Because the spanner is adapted to engage with the coupling portion and to locate with the at least one elongate locating member, the spanner is locked in position relative to the coupling device and there will be little relative movement between the spanner and the coupling nut. In addition, the presence of the at least one elongate locating member facilitates the use of spanner by the operator.

Preferably, the coupling portion receiving means is adapted to receive the spigot formed by the second, protruding portion of the second conduit of the coupling device.

According to a fourth aspect of the present invention there is provided a method of forming a coupling between a first conduit and a second conduit, which conduits are adapted to carry HF.

The invention will now be described by way of example only with reference

to the accompanying drawings in which : Figure 1 is a cross-sectional representation of a coupling device according to aspects of the present invention; Figure 2 is a plan view of the coupling device of Figure 1; Figure 3 is a cross-sectional representation of a spanner according to the third aspect of the present invention; Figure 4 is a front view of the spanner of Figure 3; Figure 5 is an inverted plan of part of the spanner of Figure 3; Figure 6 is an elevational view from one end; and Figure 7 is a side elevational view of another form'of spanner, in accordance with the invention, in position for tightening or loosening of the coupling portion of eg. Figure 1.

Referring to Figures 1 and 2, a coupling device according to the first and second aspects of the present invention is designated generally by the reference numeral 1. The coupling device is used to form a connection between pipework 2 leading from a tank containing hydrogen fluoride, and a filling/discharge line 3 connected to a bulk transport tank. The pipework 2 leading from the tank is sealingly attached to a sleeve portion 4 which forms a female connection portion. The filling/discharge line 3 is sealingly attached to a second, protruding portion 5 which together with the filling/discharge line 3 forms an extended spigot 6 and also a male connection portion 7 that as shown is a hollow cylinder. The male connection portion 7 comprises a flange 8 encircling the outer periphery thereof and having a larger radius than the main body of the male connection portion 7. The flange thus extends from the male connection portion by an amount substantially equal to the thickness of end portion 9 of sleeve portion 4. A gasket 10 is positioned between flange 8 and end portion 9. Gasket 10 is preferably of a type having serrated edges in areas of contact between one or both of the members 4,5.

The outer surface 15 of sleeve portion 4 is formed into preferably a two and half inch British Standard Whitworth thread having a thread pitch of five threads per inch.

The coupling device further comprises a coupling nut 11 that in the embodiment shown is of a hollow, cylindrical shape (as is evident from the figures) and is engageable with both the first sleeve portion 4 and the second, protruding portion 5. The coupling nut 11 comprises an outer wall 12 and an inner wall 13 which inner wall is formed into a two and half inch British Standard Whitworth thread having a thread pitch of five threads per inch ie. a complementary thread to that of portion 4. On outer wall 12 of coupling nut 11 are positioned three elongate locating members 14 extending outwardly therefrom. The locating members extend from the in- use upper end of coupling nut 11 when the latter is oriented as shown in the figures. The locating members are positioned at substantially equally spaced apart intervals around the outer wall 12.

The nut 11 further comprises a central aperture 17 shaped to fit over spigot 6 and to rest on the side of flange 8 that is remote from connection portion 7. The nut 11 is thus easily positionable on spigot 6, and is prevented from falling therefrom by flange 8.

Turning now to Figures 3 to 6, a spanner according to a third aspect of the present invention and adapted to be used to tighten and loosen the coupling device 1 is designated generally by the reference numeral 100.

The spanner 100 comprises an arm 110 and a head 120 which in this embodiment is hollow, although it could also be solid for different applications. The head 120 is formed with three locating member receiving portions 130 each in the form of an open ended recess, and a spigot receiving portion 140 in the form of an open ended recess in the top of head

120. In use, the spanner head is configured such that it will engage with the spigot and also the three location members 14.

An operator initially positions spigot 6 in spigot receiving portion 140, and then orientates the spanner 100 so that each of the location members 14 are located within portions 130. Once the spanner 100 is positioned in this way, it is locked firmly in place, facilitating the operation of the spanner in tightening or loosening the nut 11. It is then relatively easy for an operator to cause the coupling device 1 to rotate about the longitudinal axis of the spigot 6 by applying pressure on the arm 110. This will enable the coupling nut 11 to be screwed into place by virtue of the screw thread formed on the inner wall 13 of the locking nut 11, which engages with the complementary screw thread 15 formed on the outer wall of the first sleeve portion 4.

The force applied by the operator will be applied evenly around the coupling device 1 since the force will be distributed by the three locating members 14. The effect of rotating the coupling nut 11 by means of the spanner 100 pushes the first sleeve member towards the second sleeve member. This applies pressure on the gasket 10, and the serrated surfaces (if present) of the gasket form a fluid tight seal between the first and second sleeve portions.

Referring now to Figure 7 there is shown a variant of the spanner 100'in use to tighten the coupling between a tank outlet line (first conduit) 2 and a filling/discharge line (second conduit) 3.

Spanner 100'has an arm 110'and a head 120'that are similar to the counterpart components 110,120 in Figures 3 to 6. However arm 110' differs from arm 110 in that, between its ends, arm 110'incorporates a torque indicator 115.

In the embodiment of Figure 7 indicator 115 is in the form of two flexibly connected arm parts 111 and 112. The parts 111 and 112 are rotatably connected in a per se known manner by a so-called ratchet or"clicker"type of torque indicator.

Other forms of torque indicator (such as but not limited to a needle gauge type) may alternatively be used to indicate the torque generated by rotation of the spanner 100'about the elongate axis of line 3.

In use of spanner 100'to tighten the coupling nut 11 the user of the spanner 100'may refer to the torque indicator 115 in order to ascertain when the nut 11 is correctly tightened (ie. so as to ensure an effective seal between the sealingly engageable components, without the risk of damage caused to such components by over-tightening of nut 11).

For the avoidance of doubt, at least the following may be varied, within the scope of the invention, in accordance with the knowledge of the skilled worker: the external shape of the coupling nut and, as necessary to provide complementary engagement therewith, the shapes of the recesses in the head 120 of spanner 100; the member profile/size and positioning of the locating members 14; the choice of complementary threads defined on the coupling nut 11 and sleeve member 4.

Also for the avoidance of doubt although the component 6 is described as a spigot, in practice it may be a continuous filling/discharge line as mentioned hereinabove.