IRJET- Design and Analysis of Anchor Block and Penstock Pipe of a Hydroelectric Project

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 05 Issue: 03 | Mar-2018 www.irjet.net p-ISSN: 2395-0072
© 2018, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 1063
DESIGN AND ANALYSIS OF ANCHOR BLOCK AND PENSTOCK PIPE OF A
HYDROELECTRIC PROJECT
Rishiraj P Moni1, Bijimol Joseph2, Dangy George3, Jithin Jose4
1,3,4 B Tech Student, Dept of Civil Engineering, Viswajyothi College of Engineering and Technology, Kerala, India
2 Assistant Professor, Dept. of Civil Engineering, Viswajyothi College of Engineering and Technology, Kerala, India
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Abstract - KSEB Ltd. has been executing a hydroelectric
project naming Thottiyar hydroelectric project with an
installed capacity of 40 MW envisaged to produce an annual
energy of about 90 million units. This is a runoff the river
scheme. This project is situated in Idukki districtinDevikulam
Taluk. The project has a head of about 470m and having long-
water conducting system, of about 1.5KM .Out of this 1.5km,
1.25KM is penstock pipe having 14 anchor blocks. Anchor
blocks are typically used in waterworks applications where
thrust restraint of a pipeline is desired and wherever there
occurs any vertical or horizontal bends. Penstock pipes are
used to carry water to Power House from reservoir for
generation of electricity. These pipes are supported at bends
by anchor blocks and at intermediate by rocker or saddle
support. These pipes are designed for internal pressure,
support movements, reactions etc. This project deals with the
design of sample anchor blocks and design of penstockpipesat
several locations at different heads, and analysing them,
taking into account the water hammer effects. Detaileddesign
procedures are available in references noted .The preliminary
details of this site for executing the project is intended to
obtain from KSEB Ltd. on request for study purpose.
Key Words: Penstock, anchor block, water hammer,
thrust, rocker
1. INTRODUCTION
The function of the anchor block is to fix the penstockanddo
not allow the pipe with any direction of movement. The
installation site of the anchor block is usually at the
connection of forebay pool and pressure pipe, connection
between pressure pipe and power house,andwhenpressure
pipe changes its direction. The change of direction can be
vertical or horizontal. In either cases anchor blocks should
be provided. They are designed to ensurethethrustrestraint
of water. The penstock between the anchors are supported
by rocker supports.
Penstock pipes are also called pressure pipes, they are used
to carry water from the forebay or reservoir to the
powerhouse. These pipes should be designed for the water
pressure the desired levels, mostly at the anchor block. The
design aspects are explained in the noted references. These
penstock pipes are site welded or fabricated at site.
The main force of that decides the design of penstock at
lower levels near to the power house is waterhammereffect.
When a fully running machine or turbine comes to a sudden
stop due to any technical difficulties, or whenvalveforwater
inlet is to be closed, the running water generates a huge
amount of energy and this water waves back to the upward
direction inside the penstock. This is the worst case of
pressure acting in the penstock. To ensure safe operation of
penstock, a surge tank isintroduced in the water conducting
system so that this extra pressure is accommodatedbysurge
tank. But in our case, The Thottiyar HEP doesn’t haveasurge
tank, instead we assume the amount of water hammer at
valve closure and design the penstock at lower levelsforthis
pressure.
Fig -1: Penstock pipe
Fig -2: Anchor Block
2. SCOPE OF THE PROJECT
The design of anchor blocks and penstock is not part of any
B.Tech curriculum. The design procedures and works here
are done by staffs of KSEB Ltd. Since this design is

completely a new knowledge to fresher, they canexplorethe
civil engineering applications that theystudiedthroughtheir
academic years. The designing procedures are bit long u
have to rely upon softwareslikeMicrosoft word,Exceletc.so
apart from the basic civil engineering knowledge, computer
based software knowledge can also be acquired.
The engineering drawing includesLSofPenstock,IndexMap
of the area, and Reinforcement details of the Anchor Block
etc. so different kinds of engineering drawingknowledgecan
be acquired.
3. METHODOLODGY
3.1 Data Collection
Preliminary data such as index map, location map, L.S of
Penstock was obtained from KSEB Ltd.andwasstudied.Data
includes chainages of different anchor block at different
point, their elevation, location of center line of anchorblocks
and turbine at powerhouse.
The salient features of the work are
Basin: Periyar
River: Thottiyar (Deviyar), a tributary of Periyar River
Full Reservoir Level : +522.424m
Minimum draw down level : +516m
Type of Structure :ConcreteGravity
Total Length : 222 m
Top Length of overflow section : 82.50m
Normal Bed Level of River : +513
Crest Level of overflow section : +520.424
Top of None overflow section : +523.164
Height of overflow section above bed level: +7.50m
Maximum Water Level : +522.164
Upstream profile : vertical
Downstream profile : Ogee curve up
to Tangent point
and then a slope
of 0.70H to 1V
3.2 Studying the Design Procedure
The design of Anchor block is done according to IS
5330:1984. The design of penstock is done using IS Code:
11639(Part 1):1986. The code says about the numerous
forces acting in the anchor block both in pipe full condition
and pipe empty condition. The penstock design forces are
also mentioned in the code. The sample design was done by
hand calculation.
3.3 Design and Analysis
The design and analysis of the anchor block and penstock
was done in Microsoft Excel. The initial values were fed
accordingly until a stable design was obtained. Then the
dimensions for the anchor block was finalized.
Table -1: Design Forces on Anchor Block
3.3 Design Conclusion
Fig- 1: Plan of Anchor Block
Fig-2: Section AA of Anchor Block

Fig-3: Section CC of Anchor Block
Fig-4: Note
4. CONCLUSION
The design for a sample Anchor Block by providing
minimum dimensions as per the IS code was done and this
failed the stability criteria. An increase in dimensions made
the anchor block satisfy the stability criteria. The penstock
design was done, and proportional increase in thickness
from upstream to downstream ranging from 12mm to 42
mm respectively.
REFERENCES
[1] Manual on design fabrication Erection and
maintenance of steel penstocks (Hydel Civil design
directorate, Central Water and Power Commission-
New Delhi)
[2] IS Code 5330: 1984 Criteria for Design of Anchor
Blocks for Penstocks with Expansion Joint
[3] IS Code 11639(Part 1): 1986 Criteria for Structural
Design of Penstocks

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