Entruded multitubular device

Details Entruded multitubular device Entruded multitubular device

2000-02-09

2003-05-20

Hook, James (Department: 3752)

Pipes and tubular conduits

Plural duct

Longitudinally extending common wall

C138S118000, C138SDIG001

Reexamination Certificate

active

06564831

ABSTRACT:

This invention relates to an extruded multitubular device, particularly to a heptatubular, dodecatubular and tridecatubular one, to its use in housing and laying of cables, to the procedure and die for the production thereof, to a method for the installation thereof, to joint, and to the use of said joint.
The privatization process in Argentina gave rise to the need of laying cables, essentially Optical Fiber (“O.F.”), with more than one cable at a time.
Thus, at the end of 1991 and beginning of 1992, Telefónica de Argentina required from its suppliers a tubing known as “TRITUBE FOR OPTICAL FIBER CONVEYANCE”, already used in Europe since several years.
Said requirement for the installation of O.F. focused almost exclusively on this product, both from the part of Telefónica and Telecom and other contractors, which decided to operate with these products instead of using separate monotubes.
Upon the appearance of the Tritube, companies were aware of the advantage of operating multiple channels with a single installation cost. This may be seen in telephony, and in all those cases in which more than one O.F. cable or other cable of small internal diameter is to be laid. Examples include Bitubes for data transmission in Oil pipelines, Tritube in data transmission within a same company, tritube for video-cable and many other uses. At present the concept of Planar Multiple Tubes Lines of up to Four tubes (Quatertube).
On the other hand and most recently, other problems arose which required solutions.
Upon the privatizations commencement, installations in large cities were done in the open. Channeling was done by means of trenches after digging-up streets. This resulted in a very messy laying with plural interferences, and further, in the consequent inconveniences as regards transit, safety and environmental damage.
Once the authorities of the City of Buenos Aires, many municipalities of the Great Buenos Aires and other cities throughout the country were aware of the problems arising from this installation procedure, a series of much more stringent directives for the execution of new works was established, in order to promote works organization.
These directives establish that any new laying to be done must hold the corresponding municipal consent, but even then this consent does not enable the digging-up of streets or sidewalks, except for a minimum portion which corresponds to the perforation of a hole. From this perforation site, and with special equipment such as Microtunneling or similar equipment, another perforation located at a certain distance from the first is to be reached. Further, in the City of Buenos Aires at least, works must be accomplished from Monday through Friday during the night (from 8 PM to 8 AM of the following day), at present it being possible to work Saturdays and Sundays all day long. These restrictions provide that both (inlet and outlet) perforations are to be closed and perfectly signalized the moment works are interrupted.
Tunneling implies the use of non-conventional installation technologies, generally known as Trenchless Technology. This system is increasingly frequent in cities or when overcoming an obstacle, that is, cases in which installation by means of conventional technologies is difficult or even impossible. It is important to note that the material specially apt for tubing installation works by means of Trenchless Technology is High Density Polyethylene (HDPE), due to the fact that HDPE tubes are supplied in a continuous form, whether in the form of spools or lengths which are joined by butt welding and the like (as a single tubing without possible leakage points in joints), which tubes are sufficiently flexible in order to absorb trajectory changes, and exhibit an excellent impact resistance, whereby same are specially suitable for any kind of ground and they do not affect environment.
Companies in charge of laying are also required to provide for future channeling series, along with the own laying, which is to be equal to or larger than that used for their own service.
At present works involve seven monotubes with 40 mm OD each, surrounding a central tube of 64 mm OD, as per
FIG. 1
schematic.
This arrangement demands tunnels at least 20% larger than those of 150 mm OD of the system, and further, in order to render the installation feasible, a backreamer must be used which operates in a scale 20-25% larger than this last diameter, and thence we need a tunneling equipment able to perform perforations with diameters larger than 225 mm.
Further, this system's particularity is that the 63 mm tube is firstly placed where the tubes assembly is strapped. At the same time, and in order to ease sliding of tubes packet within the tunnel, works are done with bentonite pumping or bentonite or polymer baths. As this system is not a mass one, it takes part of the pumped bentonite, which then remains amid the tubes. This produces expansions and contractions of the tubes packet between the strapped and non-strapped areas, increasing the assembly diameter in a discontinuous fashion.
Maximum tensile stress the tubes may support during the installation thereof is a function of the HDPE admissible stress before its yield point (yield &sgr;) (tensile value from which material no longer exhibits an elastic behavior, with recoverable distortion, but a clearly plastic behavior, with permanent or non-recoverable distortions), and of the resistance area.
Packet resistant area can be seen in the shown schematics, but only as regards the seven external tubes.
On the other hand, the force required in order to pull the tubes packet along the tunnel, from one perforation to the other, has to be higher than the total resistance force exerted by tubes packet during the displacement thereof, and which depends from two effects: a friction effect and an effect produced by the tubes packet weight during hauling. The friction effect is a function of the friction area and a “coefficient of intrinsic friction” of the tubes packet within the tunnel and the ground which is to be traversed. The weight effect is precisely a function of the packet total weight (tubes of 40 mm diameter+lengths of 63 mm tubes+straps+water and bentonite portion remaining between the tubes) affected by a weighting coefficient.
Net friction area is all that area contacting the tunnel, i.e., the perimeter times the length of the packet to be installed. As expansions and contractions increase the “net contact perimeter” between packet and tunnel and there exists a maximum force that can not be surpassed, there also exists a maximum friction net area which may not be exceeded. Consequently, when the packet is to be hauled, any increase on the contact net perimeter demands the decrease or limitation of the maximum distance between perforations, in order that the maximum hauling force may be smaller than or equal to the maximum resistance force the tubes packet may withstand.
Accordingly, the smaller the weight of the tubes packet to be installed, the smaller the tunnel section and the smaller the resistant force of the system to be used, the lower will be the installation forces (as smaller installation equipment may be used), a longer laying may be achieved (more meters between chambers) and the installation times will be shorter.
A very convenient solution has now been find in order to achieve the final objective of installing a similar quantity of O.F. cables at a much lower cost per meter installed. This solution is the multitubular device of the present invention, particularly the heptatubular, dodecatubular and tridecatubular devices, an HDPE extruded multiple-duct which is more compact and lighter and thence exhibits a constant section.


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patent: 4273065 (1981-06-01), Lindsay et al.
patent: 4343844 (1982-08-01), Thayer et al.
patent: 4474426 (1984-10-01), Yataki
patent: 4496823

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