WO1998029679A1 - Pipe couplings, and pipelines and piping systems incorporating such couplings - Google Patents

Abstract

A pipe coupling comprises two substantially cylindrical pipe end sections (1, 2) each terminating in a flange (3, 4), an annular sealing member (5) for sandwiching between opposed end faces (6, 7) of such flanges, and circumferential clamping means (8) adapted to generate, on tightening, forces which urge the flanges (3, 4) together along a common axis (9) to compress a sandwiched sealing member (5) to form a sealed joint. Each pipe end section is associated with a member (3, 10) which comprises castellations constituted by axially directed teeth (11) and indentations (12) for accommodating the teeth (11) of the other such member, which teeth (11) and indentations (12) are arranged so as to lie radially outside the sealing member (5) and are so shaped that (a) the teeth (11) are long enough in the axial direction that the castellations (11, 12) must be intercalated in order to allow compression of the sealing member (5) and sealing of the coupling, and (b) such compression of the sealing member (5) and sealing of the coupling can be achieved without the tops of the teeth (11) of one castellation bottoming out in indents (12) of the other castellation.

Description

PIPE COUPLINGS, AND PIPELINES AND PIPING SYSTEMS INCORPORATING SUCH COUPLINGS

This invention relates to a pipe coupling comprising two substantially cylindrical pipe end sections each terminating in a flange, an annular sealing member for sandwiching between opposed end faces of such flanges, and circumferential clamping means adapted to generate, on tightening, forces which urge the flanges together along a common axis to compress a sandwiched sealing member to form a sealed joint. The invention extends to pipelines and piping systems incorporating such couplings.

Pipelines are of course widely used for the conveyance of fluids, and wherever there is a pipeline there is usually a requirement for pipe couplings. In some cases, there is a requirement that a pipeline, including any couplings or other fittings, should meet certain more or less stringent standards . This is particularly the case where the pipeline is to be used in the food industry or in some other field where hygiene is of high importance such as the pharmaceutical industry. This problem may be addressed by manufacturing the piping and fittings in accordance with some generally recognised standard such as German Standard DIN 32676 of September 1990 or British Standard BS 4825, of which Part 3: 1991 is directed specifically to pipe couplings of the type with which this invention is particularly concerned.

It will be appreciated that any pipe coupling for use in such a pipeline should be free not only from contamination by dirt, but also from contamination by materials which may be flowing along an adjacent pipeline of a piping system which may accidentally be coupled into the line under consideration, and it is an object of this invention to provide pipe couplings which may be used to render such accidental incorrect coupling less likely. According to this invention there is provided a pipe coupling comprising two substantially cylindrical pipe end sections each terminating in a flange, an annular sealing member for sandwiching between opposed end faces of such flanges, and circumferential clamping means adapted to generate, on tightening, forces which urge the flanges together along a common axis to compress a sandwiched sealing member to form a sealed joint, characterised in that each said pipe end section is associated with a member which comprises castellations constituted by axially directed teeth and indentations for accommodating the teeth of the other such member, which teeth and indentations are arranged so as to lie radially outside the sealing member and are so shaped that

(a) the teeth are long enough in the axial direction that the castellations must be intercalated in order to allow compression of the sealing member and sealing of the coupling, and

(b) such compression of the sealing member and sealing of the coupling can be achieved without the tops of the teeth of one castellation bottoming out in indents of the other castellation.

The invention provides a separable pipe coupling which can be tightened to give an effective seal provided that the castellations of the respective sections are compatible to the extent that they can be intercalated in order to allow compression of the sealing member on tightening of the clamping means. The provision of different sets of couplings having different castellation patterns allows each line of a system of adjacent pipelines to be connected using couplings from such different sets, thus reducing the likelihood that an accidental cross-connection could be made between two such pipelines. Thus, for example when installing a number of different pipelines at a given site, one could make use of that same number of differently coded sets of couplings. Each length of piping could be pre- fitted with end sections having the appropriate coding and it could then only be connected to another length of piping having an end section with the same coding. The adoption of a system according to the invention can thus provide an element of self-checking during the building of a piping system.

The invention includes a pipeline comprising interconnected pipes which are coupled together by one or more such pipe couplings, and it extends to a piping system comprising two or more such pipelines wherein the respective castellations in pipe couplings of the different pipelines are arranged so that the castellations of couplings of one pipeline cannot be intercalated with the castellations of couplings of any other pipeline, thereby preventing the formation of a sealed joint.

Preferably, said circumferential clamping means is arranged to bear on conical rear faces associated with each said pipe end section in order to generate said forces which urge the flanges together. This is a particularly simple and convenient way of generating the required seal- compressing forces.

In the most preferred embodiments of the invention, said circumferential clamping means comprises spaced opposed shoulders for co-operating with conical rear faces of the coupling and said shoulders are so axially spaced that the rims of said conical rear faces can only be inserted between such shoulders for clamping when said castellations are intercalated.

It will be borne in mind that pipework and fittings are commercially available in a range of standard sizes whether measured in inches or metrically, and that couplings according to the invention will be manufactured in corresponding sizes, for example to fit piping having an internal diameter in the series 25.4mm, 38.1mm, 50.8mm, 63.5mm, and 76.2mm. Arranging the axial spacing of such shoulders as described ensures that no coupling can be made without intercalation of the castellations when using clamping means of a size appropriate to the coupling. Advantageously, at least one said conical rear face comprises a shoulder which limits inward movement of said circumferential clamping means . By appropriately arranging such a shoulder, it is possible to ensure that it is not possible to form an apparently tight joint even when using a clamping means which would be appropriate for a larger diameter coupling. The presence of such a shoulder can also militate against clamping of an uncoded coupling flange (as previously known) against a castellated member. Preferably, said axially directed castellations are peripheral to the clamping face of each said flange. This ensures that the sealing faces of the flanges, that is, those which bear against the sealing member are clear and unobstructed so making it easier to afford a good seal at the coupling.

Preferably, and in order that a single design of castellation may serve on either side of a coupling, the tooth and indentation coding patterns are circumferentially paired and there are one or more of these coding configuration pairs in each castellation. In this way on any one coupling a simple rotational alignment between the two castellated members will allow a set of coding teeth to enter the indentations of the coding configuration in the opposing backing ring, and this will allow the coupling to be clamped up.

Advantageously, the patterns of castellations on said castellated members are substantially identical. This greatly simplifies machining of those castellated members.

It would be possible to form the teeth of the castellations by separate pins which could be bonded, e.g. brazed, into holes in one of the castellated members for cooperation with correspondingly sized and shaped holes in the other, but in preferred embodiments of the invention, said axially directed castellations are formed integrally with each said castellated member. This promotes simplicity of manufacture while ensuring a robust and long-lasting keying for the coupling.

Coding of the couplings according to this invention may readily be assured by varying the spacing and or number and or circumferential extent of the teeth and corresponding indentations. It is thus possible to provide an extremely large number of possible different codings to suit a wide range of practical applications.

Preferably, one said castellated member is constituted by a said flange while the other is formed by a backing collar which itself has a conical rear face and is, in the joined coupling, sandwiched between said circumferential clamping means and a rear face of the other said flange. This facilitates joining pipe lengths together using the coupling, since the collar may be rotated easily to a proper orientation for intercalation of the respective castellations .

In embodiments comprising such a collar, it is preferred that the rear flange face against which said backing collar is urged by said clamping means is itself substantially planar, the required conicity being provided solely by said backing collar. This promotes simplicity in the manufacture of the flange. It is also preferred that the rear face of a said flange, or its rim, provides shoulders for radially locating said backing collar. This simplifies assembly of the coupling prior to clamping.

Preferably, said backing collar is formed from stainless steel, as indeed is the whole of said coupling, apart, of course from said annular sealing member, which is suitably of an elastomeric material . The use of austenitic stainless steel is preferred.

The sealing means in conventional practice for couplings of this type consists of a elastomeric sealing ring of special profile clamped between the flanges which is so located and arranged that a plain bore through the pipeline is preserved without any gaps or interstices in which bacterial or fermentation products can lodge. In particular the width of sealing face exposed to fluid in the pipeline is narrow and forms part of a radially disposed rectangular tag in section which is firmly clamped between the adjoining faces of the coupling flanges. In this way a gap-less bore is created with the interface between elastomer and the coupling flanges being fully sealed. The sealing ring may be located radially between the flange faces by means of symmetrical beads formed on the two axial faces of the sealing ring radially outward of the tag forming the bore surface. These beads may be semi circular, ' V shaped or other in section and they enter accurately pre formed corresponding grooves in the flange faces. The sealing ring section may extended radially further outward of the locating beads to terminate in another tag portion which comes to lie flush with the outside of the coupling. Alternatively, the sealing ring may continue beyond the outer edge of the flange rim to terminate in a circumferential flap which overlies one or other of the cylindrical outer surfaces of the flanges. These flaps may be colour coded or otherwise marked to identify the sealing ring compound and the purpose of the flap is to make identification visible from the outside through apertures or gaps in the clamping rims so that control inspection can determine the type of seal used in a particular coupling or joint.

Preferably, said sealing member includes a circumferential flap which overlies a peripheral rim of a said flange thereby to locate the sealing member with respect to such flange, and preferably also, the castellations of said castellated members are arranged so as to leave a window through which such flap may be viewed when they are intercalated. Such sealing members may be colour coded or otherwise marked in order to give an indication of the grade of rubber (or other material) used for making the seal, and the provision of such a window can allow such a marking to be checked without unmaking the coupling joint. Advantageously, at their inner circumferences, the sealing faces of said flanges and bores therethrough form sharp corners, and the sealing member has an internal bore of substantially the same diameter as such flange bores, thereby to provide a substantially smooth through-passage in the coupling. This is a particularly valuable feature in hygienic couplings in order to reduce spaces in which food or other material may lodge and decay or otherwise form a source of contamination in the pipeline. In some alternative embodiments of the invention, a coded coupling is provided with a backing collar behind each flange which reaches over the rim of the flange. The backing collar itself has a rim projecting over the flange in the direction of the opposing flange. These rim projections carry the required castellation patterns in male and female configurations so that only matching configurations can enter into each other to allow the flange assembly to be clamped up.

Clamps for this design would be suitably proportioned and would require to be larger in section than those of conventional couplings and they would bite on conical faces formed at the back of each backing collar. Thus when clamped up the clamps press the backing collars together which in turn press together the flanges which in turn clamp up the sealing ring situated between them. In order that a single design of clamping ring may serve on either side of a coupling, the male and female coding patterns may be circumferentially paired and there may be one or more of these coding configuration pairs on each coding collar. In this way on any one coupling a simple rotational alignment between the two backing collars will allow a male set of coding protrusions to enter the female section of the coding configuration in the opposing backing collar, and this will allow the coupling to be clamped up. Where seals of the type are used which carry a flap overlying one of the flange rims the backing collars can be so dimensioned as to accommodate the seal flap in its normal position and also gaps may be formed circumferentially between consecutive coding patterns to allow a visible check of any identification marks which may be present on the seal material. The radial location of the backing collars on the flanges may be secured on the flange rim or other configuration of the flange back faces. It is important in this context that the configuration of the flanges will not be the same as those of conventional uncoded flanges so that a coding system cannot be circumvented by using conventional clamps and simply leaving off the loose backing collars on the two sides of the joint.

As a further feature of this design one or more apertures may be formed in the rim clamps to allow tags or stems or other features which form an integral part of the backing collar to protrude through them and to be visible from the outside. These apertures will be formed in the central portion of the clamps and the tags on the backing collars will be so positioned that they correspond the apertures formed in the clamps. Conveniently, the tags on the assembled coupling may be displaced 180° to each other so that one or other of the tags is visible from either side of the pipeline. On the outer surface of these tags the coupling code can be clearly marked, embossed, stamped or painted and this marking will be clearly and easily visible for the purpose of control .

As a further aid to identification, the tags may have a bar code marked on them which can be identified by an electronic bar code reader. The signal can be read directly or be input into a computer and it will not only identify the flange, but by reference to the joint coding index will be able to identify immediately the liquid or chemical which is carried in the pipeline.

Thus the pipe joint design as a whole maintains the existing use of seals according to current practice and provides a simple and efficient coding system which will prevent incorrect pipe joints as the loose backing collars have to be placed on the pipeline before the flange is screwed, welded, soldered or otherwise fixed into position. The design also allows verification at all times of the joint code and fluid from near or remote positions and this will further contribute to the integral security of the pipeline system as a whole.

In a development of this design the backing collars may be split into two halves along a diameter so that they can be fitted to fixed elements of pipeline which are integral with their flanges at both or all ends. This may be the case for prefabricated bends, T pieces, manifolds or other similar elements. In such cases the slipping on of integral backing collars may not prove possible, but split collars can be fitted behind the flanges and then fastened together by a convenient means to form the required coded backing collar. Conveniently, if the male and female pattern of coding is used once or an integral number of times on a coding collar a correctly chosen diametral split will ensure that integral number of coding pattern groups are contained on each semi-circular backing collar. In the simplest case there would be a single male pattern on one semi circle and a female on the other.

The joining of the semi circular collars behind the flanges can be arranged by pin and socket means, in which the pin may carry a spring ring which can be pushed into the socket to the point where it then enters a groove in the socket hole to form a secure locking retention. Alternatively, the joining of the semi circular collars can be achieved by gluing or dowelling methods, particularly when it may not be required that the backing collar should be re-split for removal purposes.

Such split collars can readily be manufactured, but it should be noted that to allow all half collars with the same coding to be identical to each other it is necessary that the number of pattern sequences around the circumference of the collar should be even. By a pattern sequence is meant a pair of adjoining male and female keying configurations. If the number of these sequences is even it can be readily understood that the two diametrally split half collars will be identical to each other, which is a highly desirable feature for quantity production. While the general design of this coding system envisages the employment of existing sealing rings between the flanges, it could be advantageous to create a special sealing ring section which would fill any cavity which might be formed between the rim of the flanges and the bore of the backing collars coding elements. This would have the advantage of eliminating any void spaces in which dirt and foreign matter could accumulate, even though these spaces would be outside the sealing diameters of the ring itself.

The coding collars and half collars are most preferably in stainless steel or other metals, but they can be envisaged as plastic mouldings. Engineering production methods can be machining, stamping or casting, but the plastic mounding manufacturing method may have the advantage of being sufficiently accurate to require no after working. Also as plastic moulding, features can be introduced such as embossments, beads or grooves to make the assembly of the half collars in particular convenient and straightforward. Plastic half collars with suitable bosses can be envisaged as being screwed together with small screws. Alternatively, circumferential grooves may be provided in the tail sleeve portions of the coding half collars, which when placed into position behind the flange can be held together in proper alignment by a multi-coil spring ring which can be opened up to be slipped into position over the tube portions behind the flanges .

Moulded plastic half collars also have the advantage that they can be accurately semi-circular, which can be difficult to achieve for metal components which may have to be soldered up, turned and machined and subsequently separated again by heating to achieve any similar results. Plastic components can be moulded in high resistant engineering plastics which are capable of withstanding temperatures in excess of 200°C.

A preferred embodiment of the invention will now be described with reference to the accompanying diagrammatic drawings in which: Figure 1 is an exploded sectional side view of elements of a pipe coupling according to this invention prior to assembly and clamping,

Figure 2 is a side elevation showing the elements of Figure 1 assembled ready for clamping, Figures 3 and 4 are respectively axial end views in the directions of the arrows III and IV of Figure 1 of a castellated flange member and a castellated backing collar, and they indicate at I-I the sections shown in Figure 1 and at II the direction of the side elevation in Figure 2, Figure 5 is a view along the axis of an assembled and clamped pipe-coupling, and Figure 6 shows the inner surface of an opened clamp.

In the drawings, a pipe coupling comprises two substantially cylindrical pipe end sections 1, 2 each terminating in a flange 3, 4, an annular sealing member 5 for sandwiching between opposed end faces 6, 7 of such flanges, and circumferential clamping means 8 adapted to generate, on tightening, forces which urge the flanges together along a common axis 9 to compress the sandwiched sealing member 5 to form a sealed joint.

Each pipe end section 1, 2 is associated with a member 3, 10 which comprises castellations constituted by axially directed teeth 11 and indentations 12 for accommodating the teeth 11 of the other such member. These teeth and indentations are arranged so as to lie radially outside the sealing member 5, and they are so shaped that

(a) the teeth 11 are long enough in the axial direction (9) that the castellations 11, 12 must be intercalated in order to allow compression of the sealing member 5 and sealing of the coupling, and

(b) such compression of the sealing member 5 and sealing of the coupling can be achieved without the tops of the teeth 11 of one castellation bottoming out in indents 12 of the other castellation.

The sealing member 5 used in this embodiment has a peripheral flange 51 which on assembly will surround the sealing end face 6 of the flanged (3) pipe end section 1, and it also has on each sealing face an annular bead 52 which will fit inside a correspondingly shaped annular groove 62 or 72 in the respective flange sealing end face 6 or 7. These beads and the flange assist in proper centring of the sealing member 5 between the flanges 3 and 4. In the embodiment shown, the sealing member 5 may be inserted either way round.

In the embodiment illustrated, the teeth 11 and indents 12 constituting the axially directed castellations surround the clamping faces 6, 7 of the two flanges 3, 4 without encroaching over them.

As will be seen from Figures 3 and 4, the patterns of castellations on the two castellated members 1, 10 are substantially identical . They are formed integrally with each said castellated member, suitably by milling after the respective member, either the flanged (3) pipe end section 1 or the backing collar 10, has been turned. It is especially suitable to manufacture the castellated member on a Computer-Numerically-Controlled lathe. Such a CNC lathe may be controlled by a main program which governs the manufacture of the basic member which at that stage is un- castellated, and by one of a number of sub-programs each of which is designed to control the milling of a different set or pattern of castellations.

The coding pattern shown in each castellation comprises four narrow teeth 11a which may be arranged to enter four narrow indentations 12a on the other respective castellated member. There are also five broad teeth lib on each castellation of which three may be arranged to enter correspondingly broad indentations 12b located between the four narrow teeth 11a of the other respective member. At the top and bottom of each of the castellations shown in Figures 3 and 4, there is provided a further broad indentation 12c which is somewhat larger than the broad tooth lib which it will accommodate when the two castellations are intercalated. When the two castellations are intercalated on assembly of the coupling as shown in Figure 2, the result of this arrangement will be to leave a window 13 through which the flange 51 of the sealing member may be viewed after assembly.

As shown, one said castellated member is constituted by a flange 3, integral with the pipe end section 1, while the other is formed by a backing collar 10 and is, in the joined coupling, sandwiched between said circumferential clamping means and a rear face of the other flange 4.

The rear face 31 of the flange 3 is conical, as is a portion 101 of the rear face of the backing collar 10.

These conical faces are arranged to co-operate with the circumferential clamp 8 shown in Figures 5 and 6. The illustrated embodiment of clamp comprises two generally semi-circular arms 81 which are joined together by pivotal links 82 at one end and may be tightened by means of a screw 83 at the other end. These two arms 81 (which may be identical apart from an attachment point for the screw) are each provided with a slot 84 whose side walls 85 define shoulders which, on tightening of the screw 83 when assembled around a coupling, bear against the conical faces 31, 101 and ride down them, driving them together and thus clamping the sealing member 5 tightly between the sealing end faces 6, 7 of the flanges 3, 4. The rear face of the flange 4 against which the backing collar 10 is urged by the clamp 8 is itself substantially planar, and conicity is provided solely by that backing collar.

The walls 85 are inclined so that the slot is of truncated 'V shape in section, and the sides of the 'V cooperate with the coned axial rear end faces of the coupling in such a way that when the clamps are tightened circumferentially they will at the same time pull radially inwards and in this action will pull the flanges together in tight sealing engagement by virtue of the conicity. The opposed shoulders provided by the walls 85 of the grooves 84 in the circumferential clamp 8 are spaced apart by a distance ("slot width") L . The rims of the conical rear faces 31, 101 of the coupling have an axial length ("rim length") 2. The slot width L and the rim length 1 are chosen, together with the axial length of the teeth 11 so that the rim of the assembled coupling can only be inserted into the slot for clamping when the castellations are intercalated. If the castellations are not intercalated, the increased rim length is greater than the slot width, and the rim of the coupling cannot be inserted into the slot for clamping and sealing. This, of course, assumes that the clamp and coupling are of correspondingly appropriate sizes.

The clamp 8 may be applied to the coupling in such an orientation that a window 13 is visible between the links 82.

It will be appreciated that the clamp may be constructed differently. For example, it could be manufactured in three or even more main sections . The conical rear face 101 of the backing collar 10 terminates in a shoulder 102 which limits inward movement of the clamp. Such a feature can be arranged to militate against assembly and clamping of a coupling using an oversized clamp. It might be possible to apply such an oversized clamp, with its correspondingly greater slot width, over the rim of a coupling even without intercalation of the castellations, but the presence of the shoulder 102 can be arranged to limit tightening of the clamp so that the coupling is still loose. In the event, the coupling would remain loose and this would be an immediate indication that an error in coupling had been made. The rim 41 of the rear face of flange 4, provides a shoulder for radially locating backing collar.

Apart from said annular sealing member, the whole coupling, preferably including the clamp 8, is formed from stainless steel, suitably an austenitic stainless steel.

In the pipe coupling, at their inner circumferences, the sealing faces 6, 7 of the flanges and the bores through them form sharp corners 63, 73, and the sealing member 5 has an internal bore 53 of substantially the same diameter as such flange bores, thereby to provide a substantially smooth through-passage in the clamped coupling.

The cylindrical pipe end sections 1, 2 can be welded or otherwise secured, for example by expansion, to the pipes which it is intended to join. The coupling is most suitably manufactured in accordance with German Standard DIN 32676 of September 1990 or British Standard BS 4825: Part 3: 1991, or the current version of one of those Standards, or the current corresponding National or International Standard.

Claims

1 A pipe coupling comprising two substantially cylindrical pipe end sections each terminating in a flange, an annular sealing member for sandwiching between opposed end faces of such flanges, and circumferential clamping means adapted to generate, on tightening, forces which urge the flanges together along a common axis to compress a sandwiched sealing member to form a sealed joint, characterised in that each said pipe end section is associated with a member which comprises castellations constituted by axially directed teeth and indentations for accommodating the teeth of the other such member, which teeth and indentations are arranged so as to lie radially outside the sealing member and are so shaped that (a) the teeth are long enough in the axial direction that the castellations must be intercalated in order to allow compression of the sealing member and sealing of the coupling, and

(b) such compression of the sealing member and sealing of the coupling can be achieved without the tops of the teeth of one castellation bottoming out in indents of the other castellation.

2 A pipe coupling according to claim 1, wherein said circumferential clamping means is arranged to bear on conical rear faces associated with each said pipe end section in order to generate said forces which urge the flanges together.

3 A pipe coupling according to claim 1 or 2 , wherein at least one said conical rear face comprises a shoulder which limits inward movement of said circumferential clamping means . 4 A pipe coupling according to any preceding claim, wherein said circumferential clamping means comprises spaced opposed shoulders for co-operating with conical rear faces of the coupling and said shoulders are so axially spaced that the rims of said conical rear faces can only be inserted between such shoulders for clamping when said castellations are intercalated.

5 A pipe coupling according to any preceding claim, wherein said axially directed castellations are peripheral to the clamping face of each said flange.

6 A pipe coupling according to any preceding claim, wherein the tooth and indentation coding patterns are circumferentially paired and there are one or more of these coding configuration pairs in each castellation. 7 A pipe coupling according to any preceding claim, wherein the patterns of castellations on said castellated members are substantially identical .

8 A pipe coupling according to any preceding claim, wherein said axially directed castellations are formed integrally with each said castellated member.

9 A pipe coupling according to any preceding claim, wherein one said castellated member is constituted by a said flange while the other is formed by a backing collar which itself has a conical rear face and is, in the joined coupling, sandwiched between said circumferential clamping means and a rear face of the other said flange.

10 A pipe coupling according to claim 9, wherein the rear flange face against which said backing collar is urged by said clamping means is itself substantially planar, the required conicity being provided solely by said backing collar.

11 A pipe coupling according to claims 9 or 10, wherein the rear face of a said flange, or its rim, provides shoulders for radially locating said backing collar. 12 A pipe coupling according to any preceding claim, wherein, apart from said annular sealing member, said coupling is formed from stainless steel.

13 A pipe coupling according to any preceding claim, wherein said sealing member includes a circumferential flap which overlies a peripheral rim of a said flange thereby to locate the sealing member with respect to such flange, and the castellations of said castellated members are arranged so as to leave a window through which such flap may be viewed when they are intercalated.

14 A pipe coupling according to any preceding claim, wherein at their inner circumferences, the sealing faces of said flanges and bores therethrough form sharp corners, and the sealing member has an internal bore of substantially the same diameter as such flange bores, thereby to provide a substantially smooth through-passage in the coupling.

15 A pipeline comprising interconnected pipes which are coupled together by one or more pipe couplings according to any preceding claim. 16 A pipeline according to claim 15, wherein the respective castellations at each said pipe coupling are substantially identical .

17 A piping system comprising two or more pipelines according to claim 15 or 16, wherein the respective castellations in pipe couplings of the different pipelines are arranged so that the castellations of couplings of one pipeline cannot be intercalated with the castellations of couplings of any other pipeline, thereby preventing the formation of a sealed joint.