GB2388373A

GB2388373A - Telecommunications cable joint closure sealant

Info

Publication number: GB2388373A
Application number: GB0304781A
Authority: GB
Inventors: William Dominick Mary Horcan
Original assignee: PALTEXA Ltd
Current assignee: PALTEXA Ltd
Priority date: 2002-03-01
Filing date: 2003-03-03
Publication date: 2003-11-12
Anticipated expiration: 2023-03-03
Also published as: WO2003074623A9; AU2003209962A8; GB2388373B; IES20020157A2; AU2003209962A1; WO2003074623A1; IE20030151A1; GB0304781D0

Abstract

A two-part polyurethane sealant, especially for a telecommunications cable joint closure, one part being an isocyanate and the second part being a tackifier. The isocyanate is preferably di-substituted and is preferably 4,4-MDI. The tackifier is preferably a polyol, most preferably a water-blown polyalkylene glycol. The sealant preferably acts as an insulator. The constituents of the sealant may be mixed in the nozzle of an applicator gun. Also claimed is a method of preventing water presence in a telecommunication cable joint closure and a method for detecting the presence of a leak in the closure. Further claimed is an apparatus for pressure testing the closure.

Description

r À A METHOD AND APPARATUS FOR DETECTION AND PREVENTION OF

WATER IN CABLE JOINT CLOSURES

This present invention relates to a method and apparatus for the detection of and 5 prevention of water in cable joint closures and more particularly in telecommunication cable joint closures.

The most commonly used joint closure in telecommunication access networks is known as the "3IA joint" which is part of the 30 series of joints originally developed by the Channel 10 Company in the U.S. The "31A joint" comprises a dome shaped cover which is clamped over a base unit. A main telecommunication cable enters the joint through an opening within the base unit, with the main telecommunication cable being connected to a number of individual cables. The individual cables exit the joint via other openings on the base unit and are used to connect places of residence, business and so forth to the 15 telecommunication network. At present when "31A joints" are completed, the only method of testing whether the "31A joint" is completed to the required standard i.e. is sealed against water is a visual test.

A high percentage of customer complaints about substandard lines, which are detected by 20 amongst other things a buzzing noise on a telephone line or a crossed-line where another person's conversation can be overheard, can be linked to water leaking into the "31A joint". Most "31A joints" are located in ready access junctions beneath the ground. It has been 25 estimated that on average in any telecommunication access network 30% to 50% or possibly greater of the "31 A joints" are leaking. If the joints are used in a particularly wet envirorrnent, where the underground access junction could fill with water, water can enter the sealed joint by capillary action along the cabling. Water is one of the main causes of problems in a telecommunication access network A telecommunication access network that has a water leakage problem suffers the following problems:

r l :::: :: À:

Contacts and Earth connection shorting. (boss of telephone lines) Dis and inter Dis pairs (paired telephone lines, this is due to water causing corrosion of copper wires by electrolysis over long periods of time) Noisy Pairs (a buzzing noise is heard on the line when in use) S Changed Pairs (other people's conversations can be heard in the background when

using the phone) Night testing by telecommunications companies enable the quality of lines to be monitored. The tests detect the amount of electrical contacts on each individual line. If 10 there are no contacts, there are no faults. Lines with contacts greater than zero are classified as being substandard lines. The amount of electrical contacts on these lines determine the level of poor quality on each line. The higher the voltage of contact, the poorer the quality of the line. As water enters the "31A joints" easily and cause the lines to short i.e have electrical contact, people start to complain as the problems associated with 15 substandard lines soon begin to manifest as noise on the line, crossed lines, no service, no dial tone, no ring or buzzing on the line and so forth.

Where a large number of line faults are reported it is possible that all the faults stem from the same "31A joint" thereby leading to a false recording of the level of faults within a 20 network. Repairing a fault within a joint does not necessarily mean that the problem is solved or that a repeat fault on the same cable will not occur. Areas where upgrade work was completed and visually checked resulted in 30% of the "31A joints" leaking within a short period of time.

25 At present the method of correcting this fault is sealing the area with a sealant.

Some sealants used do not form a strong bond with the materials used in the "3 IA joint", prevent a good seal forming within the "31A joint" and are ineffective against water capillary action. Furthermore, some sealants are difficult to use, as they must be mixed 30 before applying to the leaking area particularly if the sealant is an epoxy resin. Some resins are hand-mixed for use, which invariably leads to errors as the quantity of each constituent in the mix can vary for each joint. The volume and/or mix ratio of each constituent has a direct effect on the physical properties of the resin and if not mixed in the

r l ! correct proportion may result in a substandard product. The curing time on these resins are quite long, usually requiring at least forty minutes to harden sufficiently after being applied to the area. These methods are inefficient and subject to human error.

5 As published on news.com.av on 10th October 2002, approximately $500 million Australian dollars was spent weather-proofing the national telephone network using an epoxy sealant. It was soon discovered that the sealant conducted electricity which has led to widespread corrosion of the wires. In areas of high humidity and rainfall, corrosion of the wires has accelerated. Crude temporary measures where plastic bags were used to 10 protect the cables from water failed to protect cables in areas with high rainfall. Once water entered the joint, the cables became exposed due to corrosion and short circuited. It is estimated that in suburban areas, a short-circuit in one cable joint can disrupt between thirty to one hundred homes.

15 Alternatively the "31A joints" can be sealed using grommets or heat shrink materials forming a barrier on the base unit and subsequently clamping the dome shaped cover over the base unit sealing the dome shaped cover to the base unit with the aid of an O' Ring.

Breakdown of this type of seal can occur due to improper workmanship, incorrect assembly of grommets or poor skill when applying the heat shrink material.

It is the object of the present invention to seek to alleviate the aforementioned problems.

Accordingly, the present invention provides a sealant for a telecommunications cable joint closure comprising a two-part polyurethane sealant, one part being an isocyanate and the 25 second part being a tackifier.

Preferably, the isocyanate used is a all-substituted isocyanate and the tackifier is a polyol.

Ideally, in the preferred embodiment of the invention the all-substituted isocyanate is 30 4, -4Diphenylmethane-di-isocyanate hardener and the polyol is a water blown Polyalkylene Glycol, the invention is not limited to these constituents any suitable consitituent known to a person skilled in the art may be used.

t' c' her.. Be: ! Preferably the sealant is contained in a two-part cartridge system is applied through a mixing nozzle by an applicator gun. Advantageously the constituents are statically mixed using a gun with mixing nozzle. Ideally, once the constituents of the sealant are mixed, a S foaming two part polyurethane adhesive is formed.

Advantageously the foaming two part Polyurethane adhesive hardens rapidly and is free from tack within fifteen minutes at ambient temperatures and ambient humidity levels.

Tack is the property of an adhesive that allows it to adhere to another surface on immediate 10 contact. It is the "stickiness" of the adhesive while in a fluid or semi-fluid state. When the adhesive is defined as being free from tack, there is no "stickiness" of the adhesive.

Advantageously the Polyurethane adhesive cures to form a very strong hard seal with excellent sealant properties within 24 hours. Ideally in the preferred embodiment of the 15 invention the sealant cures within 12 to 14 hours. Ambient temperatures are defined as being between 23 C and 26 C and ambient humidity is defined as being at 50% relative humidity. However at lower temperatures the tack-free time and curing time may increase.

Advantageously the maximum time limit in which the Polyurethane adhesive becomes tack-free at lower temperatures is 25 minutes.

Advantageously, the temperature at which the sealant cures is sufficiently low that no damage is done to the outer cable sheaths of the individual conductor wires. The sealant has a maximum curing temperature in the range of 40 C to 50 C. The outer sheath of a telephone cable is usually formed from polyethylene, which has a melt temperature of 25 approximately 190 C, the inner conductor wires are also formed from polyethylene, which again have a melt temperature of approximately 190 C.

Advantageously the sealant provides flexibility to allow the cables to retain flexibility within the closure.

Advantageously the sealant acts as an electrical insulator. Ideally, the conductivity of the sealant is within the range of 10 i2 15% siemens per metre. In the preferred embodiment

r of the invention, the polyurethane sealant has a conductivity of approximately 10-i2 siemens per metro. This in effect gives a value where the sealant does not conduct electricity. 5 Advantageously the invention further provides a method of preventing the presence of water in cable joint closures, the method comprising the steps of: (a) cleaning the area of the closure to be sealed; (b) sealing the cleaned area of the closure; (c) attaching a pressure testing apparatus to the sealed joint closure; I O (d) applying leak detection fluid; and (e) activating the pressure testing apparatus to test the closure for leaks.

Ideally this method is primarily used on new cable joint closures being placed into a telecommunication network.

Advantageously the present invention also optionally provides a method of detecting the presence of a leak in cable joint closures prior to preventing the presence of water in cable joint closures the method comprising the steps of; 20 (a) attaching the air pressure testing apparatus to the joint closure; (b) applying leak detection fluid; and (c) activating the pressure testing apparatus to test the closure for leaks.

Advantageously the method of detecting the presence of a leak and the method of 25 preventing the presence of water in cable joint closures is used on cable joint closures that are already in situ in a telecommunications network. Advantageously when the two methods are used together the steps of the method comprise the following; (a) attaching the air pressure testing apparatus to the joint closure; 30 (b) applying leak detection fluid; and (c) activating the pressure testing apparatus (d) cleaning the cleaned area of the closure to be sealed;

1 1 l r l ( 6 (e) sealing the area of the closure; (f) attaching a pressure testing apparatus to the sealed joint closure; (g) applying leak detection fluid; and (h) activating the pressure testing apparatus to test the closure for leaks.

Advantageously, the present invention also provides an apparatus for pressure testing a telecommunications cable joint closure having a base unit and a removable cover unit, the apparatus comprising a hollow housing unit with an attachable inlet valve and an air pump, wherein the hollow housing unit is sealingly mountable to the base unit of the cable joint 1 0 closure.

Advantageously, the housing unit of the pressure testing apparatus resembles a cover unit of the cable joint closure.

15 Ideally, the inlet valve is attached to the hollow housing unit using a manifold where the manifold also has a pressure gauge and a pressure release safety valve attachment.

Optionally the pump used is a foot pump. Alternatively, a suitable electric pump could be used. Ideally, the air from the pump is passed through a desiccator unit prior to entering the 20 pressure testing apparatus.

Ideally, the exterior of the unit being tested is covered with a leak detection fluid.

preferably the leak detection fluid is used to cover the joint between the pressure testing apparatus and the base of the cable joint closure and the exit point of the cables on the base 25 of the cable joint closure.

It is preferable when testing a used cable joint closure, that the cablejoint closure is initially tested for the presence of any leaks. Ideally, the pressure testing apparatus is fitted and sealed to the base of the closure conning a sealed unit. Preferably, the exterior surface 30 of the base of the closure is covered with leak detection fluid. Ideally the pump is operated causing air to flow into the pressure testing apparatus, increasing the pressure within the sealed unit.

l As the pressure within the sealed unit increases, air is forced out through the leaking points on the unit. It is preferable to use a leak detection fluid, which bubbles as the air passes through it' giving a visual indication ofthe location otthe leak. When the leakage point(s) 5 are detected the pressure is released from the unit. The air pressure is released using the pressure release safety valve. Ideally once the pressure has been released, the pressure testing apparatus is detached from the closure being tested.

A new cable joint closure has no holes in the base, therefore it is necessary to drill a hole or 10 holes in the base to facilitate the cables. Once the openings have been made it is necessary to seal around them to ensure no water enters the cable joint closure.

Prior to applying the sealant, it is preferable to clean the cables and interior of the cable joint closure in order to remove grease and dirt that may prevent a good seal forming.

15 Advantageously either wet or dry isoparoffin (PF) wipes are used.

Advantageously the foaming tvv-o-part polyurethane sealant is then applied to the base of the cable joint closure.

20 Advantageously, once the polyurethane sealant has formed a very strong hard seal, the pressure testing apparatus is re-fitted to the base of the closure; the unit is then re-tested for leaks as previously described. This ensures that all of the leaks have been repaired in An, old closure unit and that there are no leaks present in the new closure unit after sealing with the polyurethane sealants.

Advantageously, once all the tests have been completed the base of the cable joint closure is re-connected to the cover unit of the cable joint closure. Optionally a dessicant such as silica gel can be placed within the closure to absorb any moisture that may enter the closure over time.

Ideally the closure is re-tested on a regular basis to ensure no leaks develop over time.

Advantageously the closure is labelled with a dated sticker to facilitate this.

., ' 1.

r l t te ( Advantageously, the method, apparatus and sealant of the invention have successfully undergone three different rigorous testing procedures. The sealant is tested with typical types of closures used within the telecommunications industry to verify and test the sealing performance of the sealant where it is used to seal resin/sealant type closures in addition to 5 repair of leaking 31A Type closures where seal integrity is compromised.

It is of paramount importance that the closures remain watertight and this inevitably hinges on the characteristics of the sealing system. Therefore, the effectiveness of the sealing system is evaluated by subjecting the closure to air tightness and temperature cycling at a 10 sealed pressure. Destructive tests are necessary to obtain information on tensile strength and elongation whereas thermal ageing can provide information on the stability of the apparatus and sealant of the invention.

TEST ONE

15 Temperature cycling in water testing in accordance with British telecom specification

LN450B.

Sealants and closures developed for the external network are required to withstand severe environmental conditions during their design life span. Seasonal and climatic variations in 20 temperature and rainfall are large. During recent winters, temperatures of-30 C and below have been recorded compared with midsummer temperatures of +70 C and above for closures exposed to prolonged periods of sunlight. This clearly demonstrates the need for materials of high thermal stability.

25 Thermal cycling and accelerated thermal ageing tests have been devised to provide extra data used in evaluating the reliability of products working at these extremes. Closures of course experience stresses in addition to those caused by climatic variations. Closures located alongside busy roads are subjected to vibrations, which can be severe. And those placed in unsuitable geographical locations may also be exposed to stresses from cable 30 creepage and other causes. Data obtained by torsion testing, flexure, impact, static loading etc. is compiled to evaluate a closures ability to withstand such stresses as well as those produced by external working methods.

l l : Accordingly a CW1587 cable was installed and sealed into a 31A cable joint closure in accordance with the method of the invention, using the pressure testing apparatus and sealant of the invention. The closure was senIed ncl the flee end of the cable.,as 5 connected to a pressure monitoring system. The pressure within the closure while being monitored continuously was increased to 400mbar (40 kPa). The joint closure was subjected to main functional testing in water through a simulated twentyfive year life expectancy of the joint closure. This involved monitoring the pressure of the closure while the closure went through fifty cycles of temperature testing in water between the 10 temperatures of 5 C and 50 C. There was a dwell time of two hours at each temperature.

Any loss of pressure that was not attributable to the monitoring equipment would indicate the presence of a leak, hence failure. No pressure loss was detected during this testing procedure. TEST TWO

15 Functional Test for Water and Air Tightness.

A closure was completed in accordance with the method of the invention using a suitably sized cable and the pressure testing apparatus and sealant of the invention. The completed closure was pressurized to lOOkPa (+/-lOkPa) and immersed in a bath of water at an 20 ambient temperature for 30 mins(+3 mins,-O mine). Any visible loss of air, not attributable to monitoring equipment will indicate a failure of this test.

The sealant provided an air tight seal as no air was detected leaking out through entry holes at base of the closure after sealing the closure with the sealant.

In addition ingress of water into the sealed closure was examined.

This test was performed by attaching a dome with a pressure valve to the base of the closure, where the cables were inserted and sealed into the closure in accordance with the 30 invention. Air was then pumped into the sealed closure to a pressure of I OOkPa (+/-1 OkPa) Leak detection fluid was applied to the base of the closure to check for leaks.

( A humidity indicator was positioned on the inside of the sealed closure to check for water Ingress. 100 cable joint closures were set up and tested with a multiple of cable sizes and numerous 5 cables in each joint to check for water ingress. No leaks were found on any of the closures.

No loss of pressure was recorded and no humidity was detected on the inside of the joint.

TEST THREE

10 Axial Tensile- 1000 Newton Pull Test A CWl587 cable was installed and sealed into a Sleeve 31A Ready Access Closure using the method, apparatus and sealant of the invention. The closure was then placed in the axial tensile rig, the free end of the cable was connected to a pressure monitoring system 15 and the closure was pressurised to 400mbar. The closure was then subjected to an axial tensile load of lkN via the cable for a period of 5 minutes.

During the test, the pressure was continuously monitored. Any loss of pressure not attributable to the monitoring equipment would indicate failure against British Telecom 20 Specification LN450B. No pressure loss was detected during this testing procedure.

TEST FOUR

Gas Blocking of Dexbond Sealant in External Joints to BT Specification RC307

25 A CW1587 cable was installed and sealed into a Sleeve 31A Ready Access Closure in accordance with the method of the invention, using the apparatus and sealant of the invention. The sealant was permitted to flow around the cable interstices. The closure cap was not fitted, to allow any gas to vent to atmosphere. The opposite end of the cable was installed into an OTIAN Generic Joint 2A closure, which was used as a pressure chamber.

30 The cable end was left open to allow the penetration of gas along the length of the cable sample. The gas (5% Hydrogen, 95% Nitrogen) was then connected to the pressure chamber

:: and regulated to 30kPa. The sample was left on test for 48 hours. During and immediately after this period, no gas was detected using a Hydrogen Leak Detector 8012.

The inicntiorl will now DC described by way ot example only and with reference to the 5 accompanying drawings in which: Figure 1 is a front view of the pressure test apparatus of the invention; Figure 2 is a plan view of the pressure test apparatus of Figure 1; and Figure 3 is an exploded perspective view of the desiccation pump mechanism.

Referring to the drawings and initially to figure 1, there is shown a pressure test apparatus indicated generally by the reference numeral I. The pressure test apparatus 1 has a hollow 15 cylindrical body 5 to which a dome 5a is attached enclosing one end of the hollow cylindrical body 5. The dome 5a is defined as the top of the pressure test apparatus 1.

Remote from the dome 5a is the base of pressure test apparatus 1.

The base of the pressure test apparatus 1 comprises a circular rim 5b. The inner surface of 20 the circular rim 5b is flush with the inner surface of the hollow cylindrical body 5, the circular rim 5b extends outwardly from the inner surface beyond the circumference of the main cylindrical body 5 of the pressure test apparatus 1 anti provides stability end support.

for the pressure test apparatus I in a standing position. The base 5b also provides a screw thread on the inner surface that enables the pressure test apparatus to be screwed onto a 25 "31 A joint" forming a pressure seal.

Positioned on the exterior surface of the hollow cylindrical body 5 is a pressure gauge 2, an inlet valve 3 and pressure release safety valve 4. In this example the pressure gauge 2, inlet valve 3 and pressure release safety valve 4 are positioned at an upper point on the 30 hollow cylindrical body 2 near the dome 5a of pressure test apparatus 1. The pressure gauge 2 is not limited to this position on the pressure test apparatus 1, any convenient position determined by a person skilled in the art can be used.

l Referring to Figure 2, the pressure gauge 2, inlet valve 3 and pressure release safety valve 4 are connected to the hollow cylindrical body 5 of the pressure test apparatus 1 using a manifold 7 with 6.3mm fittings. The manifold 7 has a four way output 7a - 7d. The 5 pressure release safety valve 4 is attached at 7a, the pressure gauge 2 is attached at 7b and the inlet valve 3 is attached at 7c. Point 7d on the manifold 7 is inserted through a hole on the hollow cylindrical body 5 of the pressure test apparatus I and held securely in position by a nut 8.

10 The hole through which the manifold 7 is attached to the hollow cylindrical body is sealed to prevent any leakage of air when the pressure test apparatus 1 is in operation. The pressure release safety valve 4 is set at 34.5 kPa +/- 10%, thus when in operation if the pressure within the manifold hence the pressure test apparatus I exceeds the value, the valve opens releasing the pressure. The pressure gauge 2 measures pressure with a range 15 of 0-15 psi (0-103kpa), however the pressure that is produced is limited to 5 psi (34.5kpa).

In this example the pressure gauge 2 is attached to the manifold 7 at 7b using a back entry, however the pressure gauge 2 - manifold 7 connection point is not limited to this position, any suitable connection point can be used. The inlet valve 3 attached to the manifold 7 at 20 7c is a female connector (6.3mm x 6.3mm) with a 9.5mm quick release coupling for safety.

The pump mechanism comprising a foot pump (not shown) and desiccator cartridge system 100 of Figure 3 is attached to the pressure test apparatus I via the inlet valve 3 on the manifold 7 of Figure 2.

Figure 3 is an exploded perspective view of the desiccator cartridge system 100. A first hollow tube 23 is completely encircled by a second hollow tube 24. In this example the first hollow tube 23 is an acrylic tube whilst the second hollow tube 24 is formed from a suitable alloy material. A circular gasket 22 is positioned at each end of the hollow tubes 30 23 and 24. The diameter of the circular gaskets 22 are equivalent to the diameter of the second hollow tube 24. Ideally, the circular gasket 22 is formed from silicon rubber, however any suitable sealant material known to a person skilled in the art can be used.

::: f A baize filter 21 is attached to each of the circular gaskets 22 at each end of the hollow pipes 23 and 24. The baize filter 21 is not limited to baize any suitable material can be used. The,lollo-w- pipes 23 and 24, the circular gaskets 22 and the baize filters 21 are all 5 held securely in position using plates 20. Where plates 20 are positioned beside each baize filter 21. Each plate 20a and 20b is rectangular in shape. Three threaded bars 11 pass through the plates 20 at points 12 located off centre on the face of plate 20. Each of the threaded bars 11 are secured using nyloc nuts 10 on the face of plates 20 that is remote the baize filter 21.

The nyloc nuts 10 are tightened such that all of the component parts, that is the hollow tubes 23 and 24, the circular gaskets 22 and the baize filters 21 intermediate the plates 20 are held tightly together preventing both air and water from entering or leaving the desiccator cartridge system 100.

The desiccator cartridge system 100 attaches to the pump (not shown) using plates 20 and pump legs 30. The plates 20 are secured tO pump legs 30 using a nut and bolt mechanism 25. The bolts 25 pass through an opening 15 on the plates 20, the opening 15 is positioned remote from openings 12.

The air from the pump is transported to the desiccator cartridge system 100 using a flexible tube 35 fitted with two elbow connectors 31 and 54 respectively the pump is connected to the first elbow connector 31 which is then attached to the flexible tube 35 at the end remote from the desiccator cartridge system 100. The end of flexible tube 35 closest to the 25 desiccator cartridge system 100 attaches to elbow connector 54. The second elbow connector 54 inserts into a "junction 53, which connects to the desiccator cartridge system 100 via an opening 14 on plate 20a. The third connection point of "junction 53 is fitted with a safety relief valve 52.

30 A further opening 14a on plate 20a is sealed with a plug 50. The further opening 14a enables a second pump to be attached if greater pressure is required. Alternatively it provides a second opening for a pump inlet should something happen the first opening.

: f: r: Advantageously the plug 50 acts as a further safety device should the pressure build up become too great.

The air from the pump exits the desiccator cartridge system 100 via opening 14b on plate 5 20b. An elbow connector 40 is attached to opening 14b on plate 20b, a piece of flexible tubing 41 fitted with a non-return valve 42 is attached to the elbow connector 40. The flexible tubing is fitted with a quick release plug 44 at the end of the tube remote the elbow connector 40. The quick release plug 44 fits into the inlet valve 3 of the pressure test apparatus I of Figures I and 2.

Once the foot pump and desiccator cartridge system 100 are connected to the pressure test apparatus 1, the equipment is ready for use in detecting the presence of water in cable joint closures. The pressure test apparatus I is specifically shaped to mimic the cover of a 31A telecommunication joint closure, therefore the process of the invention will be explained in 15 detail with reference to this type of joint closure. However the apparatus and process of the invention can be readily adapted to suit any type of joint closure.

The method of detecting and repairing a used cable joint closure is afollows: 1. Initial testing The existing cover of the "31A joint" is removed.. The pressure test apparatus I is positioned over the joint and is subsequently clamped to the joint forming a seal. In effect the pressure test apparatus I mimics the cover of the "31A joint". Leak detection fluid is placed around the seals of the "31A joint" including the seal between the "31A joint" and 25 the pressure test apparatus 1.

Air is pumped into the sealed pressure test apparatus 1 and "31A joint" by a foot pump.

The foot pump is connected to the desiccator cartridge system 100 (Figure 3) and the inlet valve 3 (Figures I and 2) as previously described. The pressure is monitored using 30 pressure gauge 2 (Figures I and 2). The pressure is limited to 5 psi (34.5kPa), the pressure release safety valve 4 (Figures I and 2) on the pressure test apparatus I are set to a safety pressure level of 5 psi (34.5kPa+l- 10%). If there are leaks present in the "31A joint" the

( air is forced out through the seals, the leaks detection fluid bubbles as the air is forced through the seal. The air pressure is maintained at 5 psi (34.5kPa) during the test to ensure that all leaks are detected.

5 The pressure release safety valve 4 (Figures I and 2) is removed and the pressure released from the pressure test apparatus I and the "31 A joint".

2. Prevention of leaks - 10 A two part Polyurethane sealant is used to bond to the cable and "31A joint" thus repairing the leaks. The main elements of the sealant are 4, -4 Diphenylmethane-di-isocyanate hardener with water blown Polyakylene Glycol. When mixed the constituents give rise to a foaming two part Polyurethane adhesive with sealant properties. This sealant is used to bond to a variety of surfaces including Polycarbonate, Perspex, uPVC, Nylon, High impact 15 polystyrene (HIPS), Fibreglass with polystyrene (GRS) and Plastic (ABS). No deterioration of these materials has been detected with use of this sealant. The sealant has been successfully tested to LN450B British Telecom Standard Test, Water Block test and 1000 Newton pull test 20 Method of Use The cable and surrounding area within the "31A joint" is cleaned using a Isoparafin (PF) wipe. l he PF wipe comprises a lint free cloth impregnated with PF solution. The areas cleaned by the PF wipe are then clean and degrased allowing for a clean bonding area. The "31A joint" is then filled with the two part sealant. The two part sealant is delivered using 25 a known delivery gun and mixing nozzle. The constituents of the sealant are individually contained within tubes. The gun is engineered to force the constituents out of their individual tubes and premix at a one to one ratio within the mixing nozzle.

The outer base of the "31 A joint" is sealed with Amalgamating tape. If there are any spare chambers within the "31 A joint", i.e. areas that do not have cable, an article mimicking the 30 presence of cable is inserted to ensure the sealant does not spill into them. The sealant forms a bond with the cable and the "3 l A joints" after a number of minutes. The sealant hardens within ten minutes. After fifteen minutes the sealant has become tack-free and a

At: t rim a secure seal is fimnly formed between the sealant, the cables and the "31A joint", forming a barrier against moisture and gas preventing water and air from entering into the joint closure. 3. Retest 5 The pressure test apparatus 1 (Figures 1 and 2) is then reapplied over the "31A joint" and sealed to the "31A joint". The same procedure as therefore is followed to ensure that the leak(s) are sealed and no water can get into the "31A joint".

4. Final Stage Once the pressure test apparatus 1 (Figures 1 and 2) is removed aRter testing, a signed an 10 dated silica gel bag is placed in the joint. The silica gel absorbs any residual water/moisture that remains in the joint or around the cable. The O-ring which forms a seal between the "31A joint" and the cover is cleaned and the cover is replaced. If the O-

ring is damaged, it is replaced prior to replacing the "31 A joint" cover.

The method of sealing a new cable joint closure is as follows: 15 When a new cable joint closure is being used, openings for the cables are formed by drilling holes in the base of the joint closure. The cables are placed in position and held in place, using putty or any similar type material. The putty holding the cables is positioned on the exterior surface of the base of the joint closure.

Once the cables are held in position steps 2 to 4 of the method of detecting and repairing a 20 used cable joint closure are followed.

A number of trials have taken place where the sealant, method and apparatus of the invention have been used on a number of 31 A cable joint closures. They are as follows: EXAMPLE ONE

This trial was conducted in a town area, where one hundred joints were surveyed over 25 three and a half days. Fifty six of the joints tested were leaking and needed to be sealed.

Of the fiRy six joints, two joints could not be sealed as they were beyond repair. Two new

44 I'! 41: -:

f' : A:

joints were made to replace the old joints, and the two new joints were then sealed according to the method of the invention. Table One provides a summary of the test

results in this area.

. - Total number of joints tested 100 Type 4 joint 31 A 95 31M 2

31C 3

No 4 joints leaking and sealed with Dexbord 31A 55

31M 1

Total 56 (56%) No. ofioints which needed to be remade 2 (2%) No. of joints which required new clamps or 'O' 7 (7%) rings to seal them _ Total number of faultyioints 65 (65%) Number of joints with water in them 15 (15%) Table One

5 56% of joints in this sample of the D-side of the access network were found to be leaking Fifty three joints sealed perfectly. In three cases there were slight leaks after sealing. It was suspected that the "O-ring" or cracked inner casing may have caused these problems.

Seven joints had evidence of water ingress, replacing the "O-ring" solved this problem.

10 EXAMPLE TWO

The second trial took place on an "old" access network, Table two synopsises the results of the initial findings at this location

': l Total "31A Dints" leak tested 21 J Leaked at unused indentation in the base I Leaked due to insufficient resin used I Leaking at the base not cleaned properly 6 Leaked due to a broken seal 1 Leaked at base due to resin not set properly I Total Leaking 10 _ "31 A joints" Leaking "old" Access Network 50% Table Two

50% of "31A joints" in this sample of"old" access network were found to be leaking EXAMPLE THREE

This trial took place on a newly built housing estate, Table three synopsises the results of 5 the initial findings.

Total "31Ajoints" leak tested 15 Leaked due to rubber seal damaged 1 Leaked due to No Resin 1 Leaking at the base (not abraded) 2 Total Leaking 4% "3 IA joints" Leaking on New Building 25% Table Three

25% of"31A joints" in this sample of new buildings were found to be leaking The leaking joints in the above trials were repaired and retested to ensure that water could 10 no longer leak into the "31A joint" using the process of the invention. Silica gel bags were placed in each of the joints tested. Six weeks later a further re-test was carried out on all of the joints. The silica gel within the joints remained blue (a change to

::: white/colourless/pink would indicate the presence of water). Testing with the pressure test apparatus l (Figures I and 2) indicated that no leaks were present.

EXAMPLE FOUR

A number of "31A joints" were tested on a third housing estate. Out of seven "31A joints" 5 tested, two were found to be leaking, one was in good condition and four were previously upgraded and were structurally in good condition. The two leaking "31A joints,' were repaired using the process of the invention described above. The estate was revisited and all "31 A joints" were found to be in good condition with no water presence detected within the j Dint.

10 EXAMPLE FIVE

A number of other spot tests were conducted on joints at different location within a city environment, there were a mixture of "31A joints" and 32B joints. Of nine joints tested, three joints leaked. The joints were repaired and re-tested using the process of the invention. It was determined that all joints were successfully repaired.

It will of course be understood that the invention is not limited to the specific details as herein described, which are given by way of example only, and that various alterations and modifications may be made without departing from the scope of the invention as defined in the appended claims.

HA MU

Claims

CLAIMS:

1. A sealant for a telecommunications cable joint closure comprising: a two part polyurethane sealant, one part being an isocyanate and the second part being a tackifier.

5 2. A sealant as claimed in Claim 1, wherein the isocyanate is a allsubstituted

isocyanate. 3. A sealant as claimed in Claim I or Claim 2, wherein the isocyanate is 4,-4 diphenyl methane-di-isocyanate. 4. A sealant as claimed in any one of the preceding claims, wherein the tackifier is a 1 0 polyol.

5. A sealant as claimed in any one of the preceding claims, wherein the tackifier is a polyalkylene glycol.

6. A sealant as claimed in any one of the preceding claims, wherein the tackifer is a water-blown polyalkylene glycol.

15 7. A sealant as claimed in any one of the preceding claims, wherein the sealant is free from tack within fifteen minutes at temperatures between 23 C and 26 C.

8. A sealant as claimed in any one of the preceding claims, wherein the sealant cures to form a hard seal within 12 to 14 hours at temperatures between 23 C and 26 C.

9. A sealant as claimed in any one of the preceding claims, wherein the time for the 20 sealant to become tack-free increases as the temperature decreases.

10. A sealant as claimed in any one of the preceding claims, wherein the time for the sealant to cure increases as the temperature decreases.

11. A sealant as claimed in any one of the preceding claims, wherein the sealant has a curing temperature range of 40 C to 50 C.

:f r 12. A sealant as claimed in any one of the preceding claims, wherein the sealant acts as an electrical insulator.

13. A sealant as claimed in any one of the preceding claims wherein the sealant has a conductivity range of low 15% siemens per metre.

5 14. A sealant as claimed in any one of the preceding claims, wherein the sealant has a conductivity apparatus of approximately 10 2 siemens per metro.

15. A sealant as claimed in any one of the preceding claims, wherein the sealant provides flexibility when cured.

15. A sealant as claimed in any one of the preceding claims, wherein the constituents of I O the sealant are statically mixed in a mixing nozzle of an applicator gun to form the twopart polyurethane sealant.

17. A method of preventing water presence in a telecommunication cable joint closure, the method comprising the steps of: (a) cleaning the area of the closure to be sealed; 15 (b) sealing the cleaned area of the closure; (c) attaching a pressure testing apparatus to the sealed closure; d, applying Ic 1- detection fluid to the exterior surface of the closure; and (e) activating the pressure testing apparatus to test the closure for leaks.

18. A method for detecting the presence of a leak in a telecommunication cable joint 20 closure, the method comprising the steps of: (a) attaching a pressure testing apparatus to the closure; (b) applying leak detection fluid to the exterior surface of the closure; and (c) activating the pressure testing apparatus to test the closure for leaks.

l ::t 'I: ' le I; 19. A method for detecting leaks and preventing preventing water presence in cable joint closure, the method comprising the steps of: (a) attaching a pressure testing apparatus to the closure; (b) applying leak detection fluid to the exterior surface of the closure; 5 (c) activating the pressure testing apparatus to test the closure for leaks; (d) cleaning the area of the closure to be sealed; (e) sealing the cleaned area of the closure; (f) attaching a pressure testing apparatus to the sealed closure; (g) applying leak detection fluid to the exterior surface of the closure; and 10 (h) activating the pressure testing apparatus to test the closure for leaks.

20. A method for preventing water presence in cable joint closure as claimed in Claim 17 to Claim 19, including using the sealant as claimed in Claim 1 to Claim 16 to seal the closure. 21. An apparatus for pressure testing a telecommunications cable joint closure having a 15 base unit and a removable cover unit, the apparatus comprising a hollow housing unit with an attachable inlet valve and an air pump, wherein the hollow housing unit is sealingly mountable to the base unit of the cable joint closure.

22. A pressure testing apparatus as claimed in Claim 21, wherein a manifold is provided on the hollow housing unit to which the valve inlet is attachable.

20 23. A pressure testing apparatus as claimed in Claim 22, wherein the manifold includes a pressure gauge.

24. A pressure testing apparatus as claimed in either Claim 22 or Claim 23, wherein the manifold includes a pressure release safety valve.

: l 25. A pressure testing apparatus as claimed in anyone of Claims 21 to 24, wherein the pump is a mechanical pump or an electrically operated pump.

26. A pressure testing apparatus as claimed in any one of elai.ms 21 tc 25,,hervir. the air from the pump is passed through a desiccator unit prior to entering the pressure testing 5 apparatus.

27. A pressure testing apparatus as claimed in anyone of Claims 21 to 26, wherein the pressure testing apparatus is used in conjunction with the sealant of Claims I to 16 and the methods of detecting leak and preventing the presence of water in a cable joint closure of Claims 17 to 20.

10 28. A method for detecting and preventing the presence of water in a telecommunications cable joint closure substantially in accordance with the invention as i herein described with reference to the drawings.

29. An apparatus for pressure testing a telecommunications cable joint closure substantially in accordance with the invention as herein described and with reference to 15 and as shown in the accompanying drawings.