1. KRAH AG : STRUCTURED WALL PIPE TECHNOLOGY
WISA Appropriate Technology Conference, Cape Town
3 September 2007
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2. Who and What is Krah? Krah AG of Germany commenced 1969
40 polyolefin pipe plants worldwide
Reference list over 260 major projects
Structured wall - gravity pipelines (KPS)
Structured wall - pressure pipes (KPPS)
Diam mm- 16kN/m2 or 2500kPa
Comply with applicable standards
Standard pipe designs profiles
Customised designs can be computed
APPROPRIATE for SA CONDITIONS

3. KPS STRUCTURED WALL

4. What are the Attributes?
Good hydraulics – smooth inner surface
Tough – abrasion and impact resistance
Chemical resistance – chemically inert
Inspection friendly – bright yellow liner
Safe joint – integrated electro-fusion
Flexible – will flex not fracture
Light weight – fast cheap construction
Design is a permutation of 5 attributes
100 year life – environmentally correct
APPROPRIATE for INFRASTRUCTURE

5. 2700 mm DIAMETER

6. Are the Designs and Standards Adequate?
Hydraulic design ATV-DVWK-A110E a 79 page comprehensive document Sept. 2001
Structural design ATV-DVWK-A127E a 91 page comprehensive document Aug. 2000
Dimensions and Technical DIN /2
System specification prEN /2/3
Design software includes all in-situ soil strength in the “soil pipe structure”
Manufacture control software integrated with design software to prevent errors.
APPROPRIATE TECHNOLOGY for SA

7. PIPES and MANDRELS

8. Design is a Permutation of Five Attributes
Equivalent solid wall pipe is, eq = (Ix . 12)^1/3
w=wall thickness
pd=profile width
sd=core tube diameter
pc=core encapsulation
e=neutral axis of wall pc sd e w pd

9. LARGE INTRICATE FITTING – note flange thickness

10. Is It a Complete System?
Bends, branches, laterals, reducers, house connections and in-line or tangential manholes
Design software “Easy Pipe” integrated with manufacturing software “Mickey”
Complete design detail submitted to client for adjudication and approval
Electro-fusion bar code in each socket
Joint clamped; pressure + temperature
Traceability of every weld and pipe

11. ALL SIZES LIGHT and EASY to HANDLE

12. RESULTS OF EASY PIPE DESIGNS
RUN 1: Standard Installation
This is typical the in excess one that is done when data are not had on the work, assuming conditions of standard installation.
RUN 2: Very Low cover depths
In this run the value of the minimum cover depths is modified, taking minimun value accepted by EASY PIPE, that is 0.5 mts.
RUN 3: Very deep cover depths
In this run the value of the max. Cover depths, taking it to 7.00 is modified mts
RUN 4: Water table
In this run the water table is added, to a height of 2 mts over the max. level of the seat bed.
RUN 5: Combination of all RUNS
Here all the changes done in the previous runs are put into play, is to say the parameters of RUN 1 but changing: the minimum cover depth to 0.5 mts, the Maxima cover depth to 7.00 mts and 2.00 the water table level to mts over the seat bed.

13. GRAPH OF RESULTS

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CONCLUSIONS
The results show that, contrary to the intuition, the annular rigidity that need the tubes for certain condition of installation he is not constant, but that will depend on the diameter of such (to see graph). This must to the different interaction tube-settles (fundamental to obtain a joint package structural) that takes place in each measurement and thus it demonstrates that the rigidity of the tube only has an intervention limited in the structural resistance of the set.
Take note also how it substantially increases to the necessary rigidity before the combination of high cover depth and water table, which increases exponentially when the phreatic level rises.
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