Production Process:
The HDPE is initially extruded by 2 extruders, one of which, is in charge of melting and injecting the inner layer while the other extruder is responsible for the injection of the outer layer. Then, the molten HDPE will go through a "Die Head"� and after passing through two channels, the outer layer will be formed by "Vacuum Forming"� system. Therefore, the outer layer is shaped by molten HDPE being sucked up towards the inner surface of the mould blocks by a vacuum pump. At the same time, the inner and outer layers will be welded and then the hot pipe will exit the machine, which will be further cooled off downstream.

In-Line Coupling:
The joining system is one of the most important features of TL products, which makes it very much distinguishable from other corrugated pipes. TL produces its pipes with �In-Line Coupling Technology�, which is formed during the extrusion as part of the pipe from the same extruder melt as the pipe itself. So, both the Bell and Spigot sections are embedded in the pipe length itself, and consequently there is no more need to have Belling machine downstream, which results in much higher production speed. In other words, to couple different length of pipes, one needs to only push the Bell and Spigot sections towards each other. The 2 gaskets (O-rings) inside the coupling will ensure that the coupled section is tight and sealed properly and will keep water in or out under normal gravity flow operating pressures. Also, the coupling section itself has double layers (In-line Double Skin Coupling technology), which makes this section as strong as the pipe itself. This type of coupling results in dramatic saving (approx. 30%) due to greatly reduced time and cost involved, when compared to other coupling methods available at present time. Moreover, unlike other coupling methods, TL pipes have the same size (outer diameter) throughout the length, which means, different parts of the pipe will undergo exactly the same pressure, so no extra load will be exerted for example on the Coupling section.

Strength & Ring Stiffness:
The corrugation of the outer surface, provides TL pipes with very high ring stiffness, which is required for any pipe that is to be used underground. TL currently produces its pipes with diameters ranging from 200 mm to 1400 mm and is also capable of manufacturing these pipes in two different standards:
1) according to "PrEN13476" at pressures of SN4 and SN8.
2) according to "DIN16961" at pressures of 16 KN/m2 and 31.5 KN/m2.
Another unique characteristic of TL pipes is that, for changing over between different pressure standards (e.g. from SN4 to SN8), the "Mold Block Insert Technology"� is employed which means manual adjustments in the production line (in order to vary the pressure standard) is not required any more, resulting in much smoother and uniform, interior and exterior surfaces along the pipe.
The flexibility and impact absorbing properties of TL pipes, make them more resistant against the influence of e.g. earthquake-induced vibrations or sudden increase of load on a section of the pipe, etc. This is probably the main reason why corrugated pipes are very popular for being used underground.

Unique Outer Layer Profile:
TL produces its pipes with a very unique profile, which is unlike any other Double Wall corrugated pipes. This design is aimed at maximizing the pressure that the exterior wall can withstand as well as minimizing the total weight of the pipe.

Chemical & Corrosion Resistance:
The raw materials used in producing TL pipes, do not exhibit a uniform chain structure and therefore they are immune from acid and basic media, exhibiting high resistance to chemicals (HDPE preserves its physical and chemical stability up to 60^C).

Optimum Hydraulic:
The smooth inner wall of TL pipes with the maximum "�coefficient of roughness" of less than 0.007 mm, ensures maximum flow with minimum drag and particle deposition, in long-term use.

Abrasion Resistance:
Abrasion is the wear caused by the combined mechanical actions of erosion and corrosion. Abrasion test indicates that HDPE pipes experience only a negligible increase in abrasive wear, compared to Steel, Cast Iron and other rigid pipes.

Weather Resistance: TL pipes contain additive which protects pipes from Ultraviolet light. This gives these pipes, the maximum weather resistance in practice.

Impact Resistance: TL Corrugated pipes can easily take the knocks and bumps during handling, moving and installation. The combination of non-brittle HDPE and its unique corrugated exterior design, makes TL pipes capable of sustaining impact at almost any condition.

                                          

Quality of TL
TL is committed to provide the best quality products to its customers and as part of its ongoing research and development program, aimed at increasing quality and reducing the costs of these products for the customers, TL owns the most modern and complete quality test laboratory in the middle-east which is equipped with testing machines purchased from IPT, Germany, and thus in order to ensure that the TL products do comply with the international standards, continuous tests are carried out on these pipes by professional quality control teams. Some of these tests are listed in the following table:
1 Density ISO 1183 2 MFI ISO 1133 3 Carbon dispersion ISO 11420 4 %Carbon black ASTM 1603 5 Oven test ISO 12091 6 Ring Stiffness (short-term) ISO 9969 7 Ring Flexibility EN 1446 8 Ring Stiffness (long-term) DIN 16961 9 Dimension PrEN 1376,DIN 16961 10 Impact EN 744
Moreover, TL comprehensively benefits from consulting with some well-known research institutions such as: University of Manchester, University of Colorado and PPI institution to make the quality of its products, the number one in the world. In fact, the technology used in TL machineries is exactly the same as that used in some of the most modern pipe manufacturers in the world including UPONOR HANCOR, WAVIN and KWH, etc. In conclusion, at TL, quality is not sacrificed at any cost.
Certificates & Approvals

TL is proud to have the following certificates & Technical approvals from world's leading research/industrial instituions:

I. Technical approval from Iranian Ministry of Construction and Infrastructure [download]
II. ISO 9001:2000 certificate from Bureau Veritas, UK [download]
III. Approval from the Iranian Standard Organization [download]
IV. Technical approval from the University of Manchester, UK [download]
V. Approval from Corma Inc. representative in Iran [download]
VI. Technical approval for laboratories from Iranian Standards&Industrial Research Institution [download]
VII. Certificate of ASTM organizational membership from USA [download]
VIII. Member of the American Society of Mechanical Engineers (ASME) [download]
IX. Member of the UK Institute of Mechanical Engineers (IMechE) [download]
X. Member of the International Code Council (ICC) [download]
XI. Member of International Engineering and  Technology (IET) [download]
XII. Member of British Standard Institution (BSI) [download]