NZ196084A - Moisture sensing in thermal insulation:electrodes encased in hydrophilic material - Google Patents

Description

1 Q f ft 0 I /bUO NEW ZEALAND PATENTS ACT 1953 COMPLETE SPECIFICATION AFTER PROVISIONAL NO; 196084 DATED: 22 January 1981 IMPROVEMENTS IN AND RELATING TO INSULATING CONDUITS WE, INSAPIPE INDUSTRIES LIMITED a New Zealand company of 55 Station Road, Penrose, Auckland, New Zealand, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to thermally insulated conduits and in particular to a sensor to detect deterioration by the ingress or egress of water into the insulation. A particular application of the sensor is for utilisation with insulated conduit installations to monitor the joins in such 5 installation.

The unwanted presence of water and similar liquids in an insulation layer or jacket of an insulated conduit is a significant problem. This is particularly so where the conduit is buried in situ. Early detection and isolation of the problem zone is very desirable enabling the necessary 10 repair to be readily undertaken to limit any resultant damage.

It is known to provide continuous unsheathed electrical monitor wires along an insulation jacket of a pipe. However, considerable care is necessary during fabrication to maintain the conduits apart such that they can fulfill their function as sensors. Further, in the case of a metal 15 conduit or a conduit having an outer metal casing the sensors must be spaced therefrom otherwise similar shorting problems can arise. Further, one of the most preferred forms of insulation is hydrophobic polyurethane foam. However as it tends to prevent water penetration this also delays detection by sensors embedded therein. Additionally, hydrophobic 20 polyurethane foam tends to form a relatively impermeable skin layer at an interface between itself and other materials. This occurs with metal elements, such as suitable as sensors, embedded therein tending to form a seal thereabout limiting the effectiveness of any such sensor in detecting water in the adjacent body of insulation.

I960 An intention of this invention is to provide a sensor which it is envisaged will at least alleviate the aforesaid problems associated with known electrical sensing means for in particular insulated conduit installation.

According to one aspect of this invention there is provided an 5 hydrophobic polyurethane thermal insulation water penetration sensor broadly comprising a pair of electrodes embedded, in spaced relationship, in a body of hydrophilic polyurethane material with each electrode incorporating terminals enabling the coupling of the electrode in series to an external electrical monitoring conductor.

According to a second aspect of this invention there is provided an in situ conduit installation comprising a plurality of conduit lengths joined end to end, at least two adjoining conduit lengths incorporating pre-insulated thermal jackets of hydrophobic polyurethane material formed between the conduit and a water impervious outer casing 15 terminating short of the ends of the conduit length and a pair of insulated electrical monitoring conductors extending through the insulation jacket in longitudinal conformity with the conduit and also terminating clear of the insulation, in situ, the ends of the specified conduit lengths being joined together and the resultant join encased with an insulation 20 jacket and casing substantially the same as those of the conduit elements being joined and in so doing mounting a sensor as described in the preceding paragraph with the hydrophilic body thereof adjacent the join between the conduit lengths and with the terminals thereof coupled to the respective ends of the conductors extending from the conduit lengths to 25 thus embed the sensor within the hydrophobic material forming the 19608 - ^ " insulation jacket about the join.

In further describing the invention reference is made to the accompanying drawing being a cut-away perspective view of a sensor mounted in a typical in situ situation.

A pair of electrodes 3 are preferably formed from brass metal mesh. The electrodes 3 are of a size appropriate to a particular requirement, for example, as to longitudinally straddle a join 5 between two lengths of conduit 6.

Wire conductor tails 7 are affixed to each end of each electrode 3 to 10 enable in situ coupling as hereinafter described.

The electrodes are embedded, in spaced relationship, in a body of hydrophilic polyurethane foam moulded to any desired shape, for example, a rectilineal block 8 as depicted. The electrodes 3 are disposed longitudinally within the block 8 with the conductor tails 7 extending from the ends 15 thereof. Thus, in situ, in mounting the electrodes 3 to straddle a join 5 the block 8 is similarly disposed.

It is found that with embedding metal elements such as electrodes 3 within a body of hydrophilic polyurethane foam the problem of the formation of an impermeable skin layer at the interface is minimal. This 20 together with the inherent water absorbent characteristics of the hydrophilic polyurethane foam provides an advantageous water sensor.

A preferred utilisation of the sensor is the incorporation thereof within 196084 - 5 ~ pre-insulated conduit elements and also at the joins between such elements in a conduit installation. The following description relates to utilisation of the sensor at an, in situ, formed joined between the two pre-insulated conduit elements. Although not depicted in the drawing 5 the inclusion of a sensor within a pre-insulated conduit will be readily understood.

In fabricating a pre-insulated conduit element 9 a thermal insulation jacket 10 preferably of an hydrophobic polyurethane foam is formed as a jacket 10. The jacket 10 is foamed into an annulus between a conduit 6 10 and an outer casing 11. To enable in situ joins 5 preferably the ends of the conduit 6 extend clear of the insulation jacket and outer casing 11 substantially as depicted in the drawings.

In accordance with this invention in the pre-insulated forming of an element 9 a pair of electrically insulated electrical monitoring conductors 7— are 15 disposed through the insulation jacket in longitudinal conformity to the conduit 6. As with the conduit 6 the conductors 7— extend clear of the ends of the casing 11 and insulation 10.

Conductors 7, 7- incorporate an insulation sheathing and thus the positioning thereof within a pre-insulated element 9 as aforesaid wherein 20 either conduit 6 or casing 11 is of metal is readily achievable as the shorting therebetween or with conduit 6 or casing 11 as appropriate is readily avoidable.

In addition to conductors 7, 7— a reference conductor 12 is similarly incorporated within a pre-insulated conduit element 9 to facilitate detecting which of several sensors in an installation has been activated, that is, detecting water. Reference conductor 12 by-passes the sensors within an installation and by utilising a conventional Varley-loop technique between either of the conductors 7a and the conductor 12 the appropriate isolation of an activated sensor can be achieved.

Following formation of a join 5 a sensor block 8 with electrodes 3 embedded therein is mounted adjacent the join and the appropriate connections made between conductor tail 7 and conductors 7a such that electrodes 3 are incorporated in series with the associated conductors 7a. An outer casing element such as casing 11 is placed about the join as to form a continuation of the casing 11 and an in situ-charge of hydrophobic polyurethane foam formed in the resultant cavity to thus encase the sensor block 8 and adjoined ends of the conduit 6 to thus effectively continue the insulation jacket 10. It is found that no particularly significant impermeable skin barrier is formed between the interface of the hydrophilic block 8 and the hydrophobic jacket 10 in which block 8 is encased in the in situ insulation of the join. Thus an effective sensor is both created and appropriately disposed.

As referred to above, in inserting the conductors 7a if required one or more sensor blocks 8 can be coupled thereto as to become lodged along the length of a pre-insulated conduit 9. However water ingress or egress is more likely to occur at joins undertaken in situ such as at junction between lengths of conduit 6. It will be appreciated that while an end to end join 5 is depicted a multiple join for example a "T" junction may be similarly joined in situ and sensor blocks 8 and associated conductors 7a appropriately provided.

Claims (7)

WHAT WE CLAIM IS:

1. An hydrophobic polyurethane thermal insulation water penetration sensor comprising a pair of electrodes embedded, in spaced relationship, in a body of hydrophilic polyurethane material with each electrode incorporating terminals enabling the coupling of the electrode in series to 5 an external electrical monitoring conductor.

2. A sensor as claimed in claim 1 embedded within a body of hydrophobic material forming a thermal insulation jacket between a conduit and a water impervious outer casing terminating short of the ends of the conduit, the terminals of each electrode being coupled to respective 10 insulated electrical monitoring conductors extending through the insulation jacket in longitudinal conformity with the conduit and also terminating clear of the insulation.

3. An in situ conduit installation comprising a plurality of conduit lengths joined end to end, at least two adjoining conduit lengths 1-5 incorporating pre-insulated thermal jackets of hydrophobic polyurethane material formed between the conductor and a water impervious outer casing terminating short of the ends of the conduit length and a pair of insulated electrical monitoring conductors extending through the insulation jacket in longitudinal conformity with the conduit and also terminating 20 clear of the insulation, with, in situ, the ends of the specified conduit lengths being joined together and the resultant join encased with an insulation jacket and casing substantially the same as those of the conduit elements being joined and in so doing mounting a sensor as claimed in claim 1 with the hydrophilic body thereof adjacent the 25 join between the conduit lengths and with the terminals thereof 19608 -8- coupled to the respective ends of the conductors extending from the conduit lengths to thus embed the sensor within the hydrophobic material forming the insulation jacket about the join.

4. A conduit installation as claimed in claim 3 wherein an 5 insulated reference conductor is mounted in conformity to the sensor conductors save the reference conductor by-passes any sensor, the reference conductor enabling comparative Varley-loop testing of the sensor conductors.

5. A conduit installation as claimed in claim 3 or claim 4 wherein 10 at least one of the pre-insulated conduit lengths incorporates a sensor as claimed in claim 2.

6. A sensor substantially as herein described with reference to the accompanying drawings.

7. A conduit installation substantially as herein described with 15 reference to the accompanying drawings.