GB2060800A - Fitting for double wall tubing - Google Patents

Abstract

In a fitting 14, the inner wall 2 of double wall tubing is conventionally connected with a compression nipple 6<1>. The outer wall carries a collar 15 at its end. The collar, and the outer wall, is held captive between gland nut 18 and an abutment 16, sealing stuffing 19 being provided. Should leakage into the annular space between the walls occur, it can pass to a drain via a drain-port 20. <IMAGE>

Description

SPECIFICATION Fitting for double wall tubing The invention relates to double wall tubing as may find application in fuel lines from injectors in marine diesel engines. It should be noted that the invention is also suitable for other diesel engines and applications other than diesel engines.

Of recent time the Classification Societies have begun to require that high pressure fuel piping on main and auxiliary engines having a bore of 250 mm or above are effectively shielded and secured. Furthermore for vessels with unmanned machinery spaces the requirement is for all high pressure diesel fuel pipes to be shielded and secured irrespective of bore size. These requirements may be met by the use of double wall tubing.

According to the invention there is provided a fitting for connecting double wall tubing to an equipment, the fitting comprising means for securing an end of the outer wall of the tubing in the fitting and means for holding an end of the inner wall of the tubing in communication with the equipment.

The means for holding the inner tube may be of conventional form.

Under normal circumstances there is no requirement for securement, as opposed to mere location, of the end of the outer tubing.

However the working pressure in, for instance, a diesel engine injector feed pipe is such that, in the absence of the securing means, the outer wall, also known as a sheath, may lose its location if it becomes pressurized on account of leaking from the inner wall. This loss of location can occur even in presence of a drain.

Preferably a drain-port is provided in the fitting for draining leakage flow from the annular space between the outer and inner walls of the tubing, the drain-port being in communication with the annular space via a bore for accommodating the inner wall.

A particularly advantageous fitting includes a member having a cylindrical bore, and outlet to the cylindrical bore for putting the drainport in communication with the cylindrical bore and an outlet from the cylindrical bore remote from the inlet, a piston displaceable in the cylindrical bore from a normal position intermediate the inlet and the outlet to a leakage indicating position at the outlet wherein the piston allows leakage flow to pass to the outlet from the annular space via the drain-port and the inlet and a leakage indicating means for indicating that the piston has been displaced in response to leakage.

Such a fitting serves as a leakage indicator.

Many diesel engines have an injector pump on which a manifold may be mounted. Such a manifold provides a convenient mounting point for leakage indicators. Accordingly the latter are preferably provided as a leakage indicator assembly for mounting on an injector pump manifold supplying fuel to a plurality of double wall injector pipes, the assembly comprising a plurality of fittings wherein there is a common connector in the form of a manifold interconnecting the outlets to the common drain line and spacing apart the other components of the fittings at predetermined intervals, the arrangement being such that leakage flow from the inner wall of any one of the injector pipes displaces the piston of the respective indicator to a leakage indicating position and that such leakage flow is directed to the common drain-line.

The leakage indicating means may take a number of forms. The or each piston may actuate its own electrical switch to provide remote indication. In a preferred embodiment, the or each position has a pin which extends out of the indicator in the direction of piston movement upon leakage. The occurrence of leakage is indicated by the pin extending further out of the indicator.

To help understanding of the invention, specific embodiments thereof will now be described with reference to the accompanying drawings in which: Figure 1 is a sectional side elevation of a double wall tubing fitting in accordance with the invention, including detail of a locking wire on a larger scale; Figure 2 is a cross-section on the line Il-Il in Fig. 1 of the double wall pipe showing the fitting in end elevation; Figure 3 is a sectional side elevation of another double-wall tubing fitting in accordance with the invention; Figure 4 is a sectional elevation of a leak indicator incorporating a fitting in accordance with the invention; and Figure 5 is a detail of Fig. 4 showing a piston displaced in response to leakage flow.

Referring first to Figs. 1 and 2, the double wall tubing 1 has an inner wall 2 and an outer wall 3 and terminates in a fitting 4. The inner wall or pressure pipe has a forged on nipple 5 by means of which, with aid of a split collet arrangement 6, the inner wall can be held by the fitting 4 in communication with equipment.

The outer wall or sheath has a circumferential groove 7 close to its end 8. The end is received in counter bore 9 to which it is sealed by an 0 ring 10. A groove 11, complementary to the groove 7 extends around the counter bore on the open end side of the 0 ring. Each groove is approximately semi-circular in section, and together they accommodate a locking wire 12 which secures the outer wall in the fitting 4. A flat 13 is cut away at one side of the counterbore 9 to provide access to the grooves for threading of the wire 12.

Fig. 3 shows another fitting 14 in which the inner wall is secured with a compression nipple 61 instead of the split collet arrangement of Fig. 1. The outer wall 3 has a collar 15 welded onto its end 8 and accommodated in a counterbore 9 in abutment against the end surface 16 of the counterbore. A threaded portion 17 of the counter bore engages a gland nut 18 which bears via sealing stuffing 19 against the side of the collar 15 opposite from the end 16 of the counter bore.

Thus the outer wall is secured in position. The fitting 14 is also provided with a drain-port 20 through which leakage from the annular space 21 between the outer wall 3 and the inner wall 2 can be drained off.

Fig. 4 shows a leakage indicating fitting 24 having a double wall tube fitted to a body 26 in which the inner wall 2 is held by a split collet arrangement and the outer wall 3 is secured in like manner to the outer wall secured in the fitting 4 of Fig. 1. The body 26 has a cylindrical outer surface 28 which is received in a yoke 29; where it is secured by a step 30 and a circlip 31. A connector 32 is clamped to the yoke by a cylinder member 33 in the form of a bolt with a shank 34 passing through the connector and a head 35. Extending axially in the cylinder member 34 is a cylindrical bore 36 which communicates at an inlet 37 with a bore 38 in the yoke which in turn communicates with a drain-port drilling 39 in the body 26. The drilling opens into the counterbore 27 which is open to the annular space 21 between the inner and outer walls of the tubing.

Thus the annular space 21 communicates with the cylinder so that leakage flow into the annular space is led to the cylinder. Such flow is shown by the arrow L in Fig. 5. A piston 40 in the cylinder is displaced from its Fig. 4 position to its Fig. 5 position wherein it has uncovered outlet ports 41 to the flow. Thence the flow is led through space 42 in the connector 32 to a drain pipe-not shown. A pin 43 is connected to the piston, and indeed is preferably moulded integrally therewith.

The pin extends through the head 35 to indicate leakage as in Fig. 5 by extending further from the head than the leak-free Fig. 4 position. Leakage can readily be verified by pushing in the pin and the piston. If the leakage flow is still present it will push the pin out again.

Although the indicator of Fig. 4 is self contained, where the body 26 is one of a linear array for instance on a diesel engine injector pump manifold, and the connector 32 is part of a manifold suitably spacing the bodies to fit the pump manifold, leakage in any of the inner walls of the tubes so connected will be indicated by the respective pin.

At the same time leakage from any inner wall will be led to a common drain.

The invention is not intended to be restricted to the details of the above described embodiments. The term "tubing" is not intended to be restrictive on the size of the "tubing" and is intended to include "pipes" where such might be a more suitable term on account of their size. The collar, when provided, may be formed otherwise than as a welded on collar; it may be for instance in the form of a flared end to the outer wall.

Claims (16)

1. A fitting for connecting double wall tubing to an equipment, the fitting comprising means for securing an end of the outer wall of the tubing in the fitting and means for holding.

an end of the inner wall of the tubing in communication with the equipment.

2. A fitting as claimed in claim 1 wherein the outer wall securing means comprises a counter bore in the fitting for receiving the end of the outer wall, an internal circumferential groove in the fitting at the counter bore and a securing clip for engaging in the internal circumferential groove and a complementary groove provided in the outer surface of the outer wall to secure the outer wall.

3. A fitting as claimed in claim 2 including a cut-away portion at the counter bore to expose the internal groove to enable a wire constituting the clip to be fed into the groove.

4. A fitting as claimed in claim 2 or claim 3 including an 0 ring seal and a second internal circumferential groove at the counterbore for accommodating the 0 ring for sealing the outer wall to the fitting.

5. A fitting as claimed in claim 1 wherein the outer wall securing means comprises a threaded counter bore with an abutment surface at its inner end and a gland nut engageable in the threaded counter bore for securing the outer wall by captivating a collar on the outer wall between the gland nut and the abutment surface.

6. A fitting as claimed in claim 5 including sealing stuffing captivatable against the collar for sealing the outer wall to the fitting.

7. A fitting as claimed in any preceding claim including a drain-port for draining leakage flow from the annular space between the outer and inner walls of the tubing, the drain" port being in communication with the annular space via a bore for accommodating the inner wall.

8. A fitting as claimed in claim 7 wherein the bore for the inner wall is counter-bored to provide a continuation to the drain-port of the annular space.

9. A fitting as claimed in claim 7 or claim 8 including a member having a cylindrical bore, an inlet to the clyindrical bore for putting the drain-port in communication with the cylindrical bore and an outlet from the cylindrical bore remote from the inlet, a piston displaceable in the cylindrical bore from a normal position intermediate the inlet and the outlet to a leakage indicating position at the outlet wherein the piston allows leakage flow to pass to the outlet from the annular space via the drain-port and the inlet and a leakage indicating means for indicating that the piston has been displaced in response to leakage.

10. A fitting as claimed in claim 9 wherein the piston is adapted and arranged to actuate an electrical switch and the leakage indicating means is a remote electrical display.

11. A fitting as claimed in claim 9 wherein the leakage indicating means is a pin extending out of the cylindrical bore away from the inlet, the amount of the pin's extension being indicative of leakage.

12. A fitting as claimed in claim 9, claim 10 or claim 11 including a connector for connecting the outlet from the cylindrical bore to the drain line.

13. A fitting as claimed in claim 12 including a body adapted for securing the end of the outer wall and for holding the end of the inner wall, and a yoke having a first bore through which the body extends and a second threaded bore at right angles to the first bore, with which second bore the drain-port communicates; the said member having a cylindrical bore having a threaded shank, in which the bore extends, and a bolt head; the connector having a first bore through which said member extends and a second bore at right angles to the first bore with which second bore the outlet communicates; the connector being held captive between the bolt head and the yoke by the said member which threadedly engages in the second bore in the yoke.

14. A leakage indicator assembly comprising a plurality of fittings as claimed in claim 12 or claim 13 wherein there is a common connector in the form of a manifold interconnecting the outlets to the common drain line and spacing apart the other components of the fittings at predetermined intervals.

15. A fitting substantially as hereinbefore described with reference to Figs. 1 and 2 or Fig. 3 of the accompanying drawings.

16. A leakage indicator substantially as hereinbefore described with reference to Figs.

4 and 5 of the accompanying drawings.