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Pipe materials in comparison - Cost saving factors

Handling of 24 m pipe string with excavatorsPhoto 1: Handling of 24 m pipe string with excavators

For comparison of costs first of all it has to be considered, that the pipe costs are only 10-20% of the total project costs. The main part of project costs are caused by civil engineering works, disturbance of overground infrastructure and of course by soil and water management! That means the influence by using a cheap pipe system to the total project costs is very low. In fact, it should be paid more attention to the fact that for the owner the financial depreciation is responsible for around 30% of the annual costs, which means by using higher quality and reaching longer service life time the costs can be reduced significantly!

Pipe costs
The pipe purchase prices depend a lot from the local market situation. Who is producing local, what are the raw-material costs and how high are the transport costs. But usually all pipe systems are in a range of +/- 20%.

Manual unloading of a Krah pipePhoto 2: Manual unloading of a Krah pipe Placing of a Krah pipePhoto 3: Placing of a Krah pipe

Transport and pipe handling
For transport, uploading and moving small equipment and light vehicles at construction site are sufficient for Krah pipes. Excavator instead of big crane, 4x4 jeep with trailer instead of heavy weight truck. Because Krah Pipes can be telescoped during transport, the transport costs can be reduced significantly if different diameters are required. The Krah Pipe surface is not affected by telescoping-procedure – this is a big cost-advantage against all other pipe materials. Concrete, clay etc. cannot be transported in this way. Furthermore Krah Pipes are delivered in standard length of 6 m, but because of low weight the pipes can be installed easily and the contractor is quicker and increases the rate of laying – this saves money. Concrete pipes on the other hand are delivered in maximum length of 2.5 m and because of their high weight the lifting of large dimensions with a standard excavator is not possible. But for Krah pipes even a manual handling to correct the final position and alignment is possible – take a look at the weight comparison below:

Table of material weight comparisonWeight [kg] comparison of DN/ID 500-2000 [mm]

Additionally Krah pipes are very resistant against impact loads by incorrect handling at construction site. The flexibility and crack-resistance are very good material properties to avoid serious pipe damages. The heavier and bigger the pipes and fittings are, the less impact loads during installation can be avoided totally.

Compaction according to international rules and standardsPhoto 4: Compaction according to international rules and standards Broken concrete conePhoto 5: Broken concrete cone Handling of Krah manholePhoto 6: Handling of Krah manhole

Jointing
The joint is just as important for the complete system as the pipe itself. But for the installation costs it is not decisive. In fact, the total costs are affected by the choice of jointing procedure!

If the joint fails, the system fails!

This is a clear statement for homogenously welded joints, because then the whole pipe string is uniformly constructed and provides in any point the same service life characteristic! No rubber gasket or other materials with reduced service life time is required. Usually for Krah pipes a life service time of 100 years will be considered! Polyethylene and Polypropylene can be welded by an automatic welding process. Krah pipes are delivered with spigot and an integrated Electrofusion-Socket. The Electrofusion-wire costs much less than a rubber gasket and the welding can be done parallel to already laying the next pipe. But also prefabricated pipe strings of 12 or 18 m can be shipped to reduce effort at construction site! At the end the contractor loses no time and money, but wins a lot by using the Krah Pipe Electrofusion!

A welded joint is 100% water-tight, which means no infiltration or exfiltration!
Infiltration, e.g. at sewers, is a big problem for the sewage treatment plant, because the treatment plant must also treat the infiltrated clean water. Exfiltration for potable water supply lines is also a big problem, because valuable asset gets wasted

Fittings
The flexible character of Krah pipes can avoid fittings for changing the laying direction. Krah pipes can be bent in a diameter of approx. 50 x pipe radius. So, for small angles mostly no fitting is necessary – this saves money and time! Further complex fittings and manholes can be prefabricated in the factory and shipped to site, that saves a lot of installation time. Especially in comparison with special concrete fitting, what has to be produced at site!

Krah pipe tailormade fittingsPhoto 7: Krah pipe tailormade fittings Krah tangential manholePhoto 8: Krah tangential manhole Prefabricated Krah manholePhoto 9: Prefabricated Krah manhole

The possibility of using tangential integrated manholes saves a lot of time during installation and a lot of material costs. In comparison to standard solutions easily up to 50% can be saved!

Diameter savings
A smaller diameter can be used, due to the very low roughness and the good hydraulic capacity of Krah pipes, this means also, that the trench can be smaller.

Operation and Maintenance
For maintenance and operation, the operator spends around 25 % of the annual costs. Most of the mentioned damages [graph 1] can be avoided totally by using Krah pipes.

Very interesting for the operator is also that Krah pipes provide much longer cleaning intervals in comparison to e.g. concrete pipes. Krah Sewer pipes are considered as self-cleaning under normal sewer conditions so far the slope is ≥ 1%. But also impact loads by using the Jet-cleaning-procedure is no problem for Krah pipes – in opposite to several other pipe materials the inner surface stays unaffected.

Typical analysis of damages at public sewersGraph 1: Typical analysis of damages at public sewers

Advantages of Krah pipes:

• No break and cracks, because flexible behaviour
• No corrosion
• No leakage, because welded
• No displacement, because welded
• No damaged branch, because welded
• Less blockade because better hydraulic and smooth surface

Cleaning Intervall
Very interesting for the operator is also that Krah pipes provide much longer cleaning intervals in comparison to e.g. concrete pipes. Krah Sewer pipes are considered as self-cleaning under normal sewer conditions so far the slope is ≥ 1%. But also impact loads by using the Jet-cleaning-procedure is no problem for Krah pipes – in opposite to several other pipe materials the inner surface stays unaffected.

Jet cleaning processPhoto 10: Jet cleaning process * Krah pipe inner layerPhoto 11: Krah pipe inner layer * Concrete abrasionPhoto 12: Concrete abrasion * GRP abrasionPhoto 13: GRP abrasion *

* The source of these information and pictures is the Jet Cleaning Report of the IKT Germany from 2004

Conclusion
The experience demonstrates that by using Krah Pipe System the contractor can save up to 20% of installation time because of easy handling!

Due to the life-service-time of >100 years, the operator can reduce the depreciation cost up to 80%. Also Maintenance costs can be reduced up to 50%.

Author:
Dipl.-Ing. Stephan Füllgrabe
written for Krah Pipes Germany