Inversin R. Allen Micro-hydropower Sourcebook

cooperative venture among all the affected farmers.

However, given the social setting, it proved easier to

deal with individual entrepreneurs than to initiate

such ventures.

e inappropriate location of potential sites-The

numerous, high-head sites were usually at impracti-

cal locations--either on steep slopes prone to land-

slides or too far from a village to be convenient.

Observation and understanding of traditional mill

locations and water control rights would have

revealed this problem earlier.

o cost of penstock-High-head sites generally require a

longer and therefore usually costlier penstock pipe.

In several locations where a higher-head site was

technically and socially acceptable, the penstock

alone cost twice as much as the turbine.

turbines has been incorporated in what is now a well-

engineered turbine design.

The design that evolved uses a crossflow

runner

either

200 mm or 400 mm in diameter and is manufactured in

10 standard widths to suit a range of flows (Fig. 10.11).

A single guide vane as wide as the runner is used to

manually control the flow. The runner, housing, transi-

tion piece between the penstock and turbine, and draft

tube are fabricated of steel sheet (Fig. 10.12). A

After a review of these and other factors, it was

decided to develop low-head sites. In the mid-1960s,

BYS had begun its hydropower work with the design,

fabrication, and installation of propeller turbines.

Because of the complexity of the design and the manu-

facturing requirements, however, neither BYS or Butwal

pursued this work. Both BYS and Butwal decided that

their work would center on the fabrication and use of

the crossflow turbine. This type of turbine seemed

more appropriate because it is easier to fabricate. It

could also accommodate a wide range of flows and

heads with only minor design modifications; the same

jigs could be used in fabricating turbines of different

capacity.

Turbine design

Focusing their efforts on turbines for low-head sites

with nearly identical operating conditions enabled BYS

and Butwal to develop one basic design and then to

improve subsequent units on the basis of experience.

Most mills operate under heads of 5-15 m. Experience

gained in the fabrication and installation of numerous

Fig. 10.12, One of

the

first turbtnes fabrfcated by

BEW

being installed at Dobllla.

hydraulic press is used to form the runner blades, guide

vanes, flanges of the housing, and other components

formed by bending. Initially, difficulty was encountered

in locating bearings suitable to support the shaft of the

runner. The limited life of imported bearings bought in

India caused problems until it was discovered that these

were actually old imported bearings, reconditioned and

sometimes resold as originals. A source of new, sealed,

self-aligning bearings made in Japan was later located

in India.

Fig. 10.1 I. A 200 mm-diameter crossflow turbine, with a

length of 560

mm,

fabricated by BEW. When the turbine is

installed, its draft tube is connected to the rectangular

flange shown.

A complete set of mechanical drawings, a list of

required materials, a description of the technical

aspects of the design, and a description of the jigs and

techniques used in the fabrication of the crossflow tur-

bine are included in Small Water Turbine

(97).

Because

230 Case studies

that publication clearly documents the design, technical

details will not be repeated here. Complete machine

drawings for a similar design developed by BYS are

found in Crossflow Turbine, Type: BYS/T3 (4).

After fabrication, the turbine and all sections of the

penstock are tested at the test site adjoining BEW

(Fig. 10.13). Any misalignment, poor threads, or leaks

then can be repaired easily in the workshop. After the

unit is sent to the field, only hand-crafted repairs can

be made.

Fig. 10.13. The test site located at the workshop of

BEW.

Sections of penstock

pipe in

the foreground

are

ready

for

pressure testing.

Design of a typical miil installation

The civil works necessary to convey water from a

stream to the powerhouse are identical to the those

used with irrigation schemes throughout Nepal. A row

of s‘:ones, sometimes interwoven with branches, forms a

temporary diversion structure across part or all of the

stream, and an unlined earth canal conveys water to the

intake of the penstock. Sometimes, water from an

exkiting irrigation canal itself is used, although this

canal might have t3 be widened to ensure an adequate

flow of water. Irrigation canals are cleaned once before

the rice pbanting season each year and then after each

flood during the monsoon season (115).

Generally, water from the canal enters the penstock

directly. A trashrack in front of the penstock inlet

retains the larger floating debris. The forebay is often

simply a transition structure between the canal and pen-

stock and does not serve as a significant settling area

(Fig. 10.14). Most of the waterborne sediment that

might injure the turbine settles in the canal before it

enters the penstock. When a large forebay is unneces-

sary, incorporating one results in additional costs

because of the concrete and labor it requires.

Butwal makes the penstock pipe of 2.5 mm mild steel

sheet in 2 m lengths. Flanges are made by hand-forging

strips of flat iron, and a groove for an O-ring is

machined in one of the two flanges welded to each pen-

Fig. 10.13. A mason complettng work

on a forebay. The

tmshmck is located behind him.

stock segment. O-rings have proven much better than

flat gaskets in providing leak-proof seals. The company

has not provided for thermal expansion of the penstock

used with its low-head installations. Leakage between

the ul;ger end of the penstock and the forebay structure,

s!thouoh expected, has never been a problem. Butwal

tries to select a penstock alignment that avoids any

deviations from a straight line, except for the portion

immediateI--

L r in front of the turbine (Fig. 10.15). If

bends are required, their size is determined by using

rudimentary field measurements.

In existing mills, all the machinery was mounted inde-

pendently on the mill floor. Careless installation of the

machinery frequently caused misalignment of shafts and

pulleys. To minimize this problem, Butwal developed a

single frame on which all the machinery required in an

average mill-a turbine, rice huller,

flour

mill, and oil

expeller--could be attached. In this way, the machinery

could be fitted and aligned in the workshop under proper

supervision. Machinery could also be secured onsite

with a minimum of concrete. Unless a customer owned

processing machinery in an earlier mill (diesel- or

water-powered), machinery for a new mill had to be

purchased through Butwal. This helped to ensure that

all the processiug machinery would be properly inte-

grated into the overall mill design.

Initially, the turbine with a 400 mm-diameter runner

was placed in a recess below floor level to gain addi-

tional head with minimum additional excavation

Case studies 231

Fig. IO. 15. The penstock descends

from the forebay

to a

mill

under

construction.

Fig. 10.16.

At

Ampchaur,

the

turbine

is placed below

floor

level.

(Fig. 10.16). The resulting higher level of the mill house

floor also reduced the possibility of flood waters reach-

ing the floor. In addition, lowering the turbine elimi-

nated the wetting of the mill floor caused by water

dripping from the seals. On the other hand, it made the

turbine somewhat less accessible. The newer, higher-

speed turbine with the smaller, 200 mm-diameter runner

is now more popular and is mounted half a meter above

Fig. 10.17.

A

mill layout using

one of the new turbines

mounted on a common frame with the

proce;jing equip-

ment. An intermediate drive shaft is

not

a usual compo-

nent of the

new

layout. It has

been

included in this instal-

lation

because the

mill owner is considering adding

other

machinery later.

the mill floor on a four-legged stand (Figs. 10.17 and

10.29).

Butwal also changed the layout of the machinery in the

mill. A problem at the first water-powered mills

installed by BYS was that the turbine simply replaced

the diesel engine in the typical installation but left the

basic layout of the mill, with its long intermediate drive

shaft, unchanged (Fig. 10.18). Three or four bearings

supported these drive shafts (Fig. 10.19). These shafts,

up to 6 m long, were rarely straight, and the bearings

failed sooner than expected. An initial solution was to

introduce a new layout for the machinery. It permitted

the low-speed oil expeller to be driven directly off one

side of the turbine and the two smaller machines to be

driven off a short intermediate drive shaft off the other

side of the tllrbine (Figs. 10.17 and 10.28). At present,

by using a 209 mm-diameter runner at most sites, the

speed is high enough for all machines to be driven

directly off the turbine shaft. Use of the intermediate

drive shaft has largely been discontinued, and the tur-

bine shaft has been extended to accept two pulleys on

one side. A third bearing is necessary along the turbine

shaft to support the pulley load. This results in an even

more compact layout (Fig. 10.20). However, misalign-

ment of the third bearing may account for some of the

subsequent problems with fracture of the runner shaft.

Another problem in existing mills involved the use of

flat belts. The shafts and pulleys were rarely aligned,

and poles implanted in the floor or otherwise secured

often were used to prevent the belts from running off

the pulleys (Fig. 10.19). This resulted in loss of power

and rapid wear of the belts. To overcome this problem,

Butwal turned to the use of V-belts throughout its mills.

These belts transmit power more efficiently than flat

belts; require no connectors, which are necessary with

flat belts; and reduce the distance required between

232 Case studies

(a) Conventional layout

I

i bearings

I

flat belt

13:

flat pulley

I

(b) Butwal’s initial layout

rice huller

(c) Butwal’s present layout

Fig. 10.18. These drawings illustrate the evolution of

the

standard equipment layout in a mill. Note that the floor

pulleys. From the drive shaft, a flat pulley to V-pulley

permits easy removal of the belt; individual machines

can then be disengaged while the turbine is running. To

facilitate the replacement of belts, D-section V-belts

with a common length are used throughout the mill.

hwtallation teams

An expatriate DCS director serves as project leader

for

the Small Turbine and Mill Project, but

the

business

chief is responsible for the day-to-day running of the

project. A technical supervisor, accountant, and store-

keeper complete the permanent

office staff.

The

heart of the installation program consists of three

or four teams that undertake work in the field. Origi-

area occupfed by the equipment is reduced, as are the

number of bearings and the ovemll complexity,

nally, each team comprised a team leader who was a

skilled mechanical tradesman (each has had BTI appren-

ticeship training), a mason, and a helper. More

recently, most teams consist of only two people; this

reduces the cost of the installation to the customer.

The only

time a

third person accompanies the team is

when a new employee is being trained.

If it is possible, the team leader is present during initial

discussions with a new customer who wants to install a

water-powered mill. When the team later goes to the

field, it acts independently. It is responsible for the

survey, site selection with the customer, and price quo-

tation. When the team returns from its first field visit,

the leader prepares the layout design and order list for

the sites surveyed. He also supervises his team in the

workshop assembly and in checking and packing all the

Case studies 233

Fig. 10.19.

A

common

sight

in

mills

using

flat

belts-a

metal or wooden stake is used to prevent the flat belt from

slipping off misaligned

pulleys.

This mill

has

a conven-

tional layout with a

long intermediate drive

shaft. The

shaft was also bent,

forcing the removal of

the fourth

bearing.

Fig. 10.20. At this

new

mill, no intermediate

drive shaft

is

used between

the

turbine and agro-processing equipment.

machinery for an installation before delivering it to the

customer for transport. The team is responsible for

installing the machinery and for any necessary followup

repair work. To minimize confusion, it is best if one

team deals with a customer from first contact to final

installation; however, practicalities make this impossi-

ble. By an insistance on uniform information-recording

procedures, it has been possible for one team to survey

and a second team to complete the installation. Parti-

cipation in decision-making has prepared each team to

set up its own independent installation operation if DCS

should decide to discontinue its operation.

Installation of a mill

Site selection

installed the first modem water-powered mills in the

196Os, they have promoted themselves. Villagers famil-

iar with traditional water-powered mills and, more

recently, diesel mills are quick to see the merits of this

compact, trouble-free source of power with low recur-

ring costs. After learning of the mills and their poten-

tial, persons with likely sites express their interest by

visiting the office in Butwal, contacting one of the DCS

teams installing a new water-powered mill in the area,

or notifying an officer of the Agricultural Development

Bank of Nepal (ADB-N), which has branches throughout

the country.

In the dry season, after Butwal has gathered as many

requests as possible from one geographical area or when

a team has

reason

to go near that area for installation

or repair work, the team takes the information needed

to contact the potential customers. The loan officer

from the nearest ADB-N office is also notified and

invited to join in the survey. The team travels by public

transport as near to the site as possible and then contin-

ues on foot, for up to a week in some cases. The team

restricts its surveying equipment to

the

minimum

required for the task--a hand-held sighting level or a

clinometer, a vinyl ribbon staff, a 30 m fiberglass meas-

uring tape, and several square meters of plastic sheet to

&assist in making flow measurements. These can deter-

mine the parameters necessary for layout and design

with adequate accuracy.

The customer is presently charged a nominal fee

of

Rs 200* for each site survey to ensure more commit-

ment on his part to following through with the project.

As the number of small local workshops beginning to

fabricate crossflow turbines increases, there is also an

increasing risk that perspective mill owners will take

the survey results to another workshop to have the

machinery fabricated. This initial nominal charge

therefore also

covers

part of the cost of the initial sur-

vey. If a site is found feasible, an additional Rs 1600 is

charged as part of the final quote for the installation.

This covers expenses incurred during preliminary sur-

veys of both feasible and infeasible sites.

In every case, the potential customer must find a loca-

tion where he either owns or can purchase land for the

mill and obtain rights to the required water. For this

reason, it is extremely important that the customer

understand the requirements of head and flow, so that

he can choose likely spots before the survey team

arrives. Ideally, a new customer should visit an operat-

ing water-powered mill to understand the principles

involved. From their experience with irrigation, Nepal-

ese farmers have a good eye for assessing a prospective

location and for sizing the canal needed to

carry

ade-

quate water from the stream to the area selected for

the forebay. This usually enables them to

select a site

with adequate water, if one exists. However, the con-

cept that the head is the elevation difference and not

the slope distance has often been difficult to explain.

Because they are interested in installing a mill, they

With the growing reputation of an. increasing number of

successful water-powered mills, there is no need now to

promote small turbines to get business. Ever since BYS

234 Case studies

* Rs 12 = US $1.00

also frequently overestimate the streamflows available

to be harnessed.

If streamflows are small, even careful flow measure-

ments made at one point in time are

of

little use.

Because irrigation often is practiced in the same area,

however,

the local population usually has a very good

idea of how small the streamflow becomes in an average

dry season and what happens during drought years. Dur-

ing its site visit, the team therefore measures the

streamflow and, from interviewing the local farmers,

determines what proportion of the average- and

drought-year flows this represents. Flow measurements

are made using a temporary wooden weir sealed with a

plastic sheet; the float method is virtually never used.

Frequently, there will not be enough water to run even

one machine for at least several months, but two can be

operated simultaneously for most of the year. This is

carefully explained to the customer. Sometimes a sec-

ond, more suitable, stream can be found in the area.

At other times, the solution has been to look for a site

with a higher head, but in such cases, Butwal often

recommends that the site be rejected. Misunderstand-

ings have been avoided by gathering all available infor-

mation to estimate flows and clearly explaining to the

customer the implications of less-than-expected flows.

With the experience gained in selecting dozens of sites,

the field team can usually tell at a glance if the site is

feasible. Because each typical milling machine

requires

approximately 3 kW of mechanical power, and three

machines are customary in every mill, 3 kW is the min-

imum desirable power and 9 kW is the maximum operat-

ing power that would be necessary. The customer must

decide if he will be satisfied with the output that can be

expected from the available sites.

Site layout

After the customer selects his preferred site, the exact

location of the mill is determined by establishing the

maximum flood level of the nearby stream and checking

the stability of the ground above the mill site to ensure

safety from landslides. It is desirable to minimize the

length of the penstock by selecting a point where the

slope is steep or where the mill house can be dug back

into the ground; however, this must be balanced against

the stability

of

the ground and the difficulty of digging

a canal to the desired point. In many cases, an existing

irrigation canal can be used. Although this simplifies

site development and reduces the cost of an installation,

it also reduces the options for site location. It may also

limit the power potential at the site because the avail-

able head might be lower than the head that could have

been developed by digging a new canal with a more

gradual slope.

At most sites, a spillway is included in the forebay wall

to lead away in a controlled manner any excess water.

In choosing a site for a mill, the location of the spillway

and the course followed by the excess water as it

returns to the stream must be considered. Otherwise,

this water might cause erosion and undermine the nen-

stock or mill.-

The next step is to establish the canal alignment.

If

an

existing irrigation canal cannot be used and a new canal

must be dug, a hand-held sighting level is used to run a

level from the proposed penstock inlet to the stream.

The actu-ll intake to the power canal would then be

slightly upstream of this point; the exact location is a

function of both the length of the canal and the nature

of the terrain. Digging the canal is entirely the cus-

tomer’s responsibility. The villagers’ experience with

irrigation qualifies them more than outsiders to deter-

mine the cost and feasibility of the alignment. The cus-

tomer also consults with villagers who specialize in

canal digging and frequently hires them to excavate

sections requiring rock-cutting. In almost

every

case,

the customer can determine the necessary dimensions

and slope of the canal when given the fraction of the

streamflow it must convey.

After the site has been selected and the canal elevation

determined, the elevation needed to keep the mill floor

safe from flooding must be established. This choice is

best left up to the customer, because he has the best

knowledge of the site and must live with the conse-

quences of the choice. The area to be excavated for the

mill floor and tailrace canal can then be marked out.

The head and other information required to design the

penstock is obtained by making a series of measure-

ments, generally using the hand-held sighting level and

the ribbon tape that is supported on a bamboo or other

Fig.

10.21. The

team surveys using a hand-held level

and a

vinyl surveying tape suspend& from a pole.

Case studies 235

suitable pole (Fig. 10.21). An elevation profile is then

run along the expected penstock alignment from the

proposed turbine location to the end of the proposed

or existing canal elevation. All the information is

recorded on a sketch of

thz

site in the field notebook.

For future reference, a permanent mark on the root

of a tree or large stone is also made and its position

recorded in the field notes. Although direct measure-

ments of the length and profile of the penstock can sel-

dom be made without excavation, they can be calcu-

lated by making several simple linear and angular meas-

urements.

within a certain period after he has been told it is

ready, Butwal may sell it to another customer. In such

cases, Butwal is no longer bound by the quotation given

the original customer. BEW gives a six-month guaran-

tee on its machinery and DCS gives a one-year guaran-

tee against errors in installation, provided the work was

done according to instructions from the leader of the

Butwal installation team. For the Indian processing

machinery, no guarantee is given.

It is important to examine and note the soil and rock

formations for possible problems in excavating for the

mill house, draft tube, tailrace canal, or penstock pipe.

A bend in the penstock pipe can usually be avoided by

shifting the site slightly; however, if a bend is required,

more careful measurements must be made.

The terms of the quotation and the details of the guar-

antee are explained to the customer. He must tmder-

stand exactly what DCS will provide and undertake. He

must also understand precisely what are his responsibili-

ties (Table 10.1). He must beware that he must receive

from the Department of Cottage Industries one license

to build and then another

to operate

the

mill. He must

place a firm order with the required advance before

DCS can take any further action.

If the streamflow is large enough that only part of it

will need to be diverted for tha mill’s use, the design

flow will depend on the head available and the power

required. The maximum flow easily conveyed in a tradi-

tional unlined irrigation canal is about 200

P/s.

The flow

for the most convenient canal design is 80-120 l/s.

Quote for the installation

Fo:merly, customers had to include an advance

of

Rs

2500 in “earnest money” with their orders before

DCS would take any action; however, customers often

waited until the last minute to arrange for a loan and

this led to cashflow problems on the part of DCS. Since

mid-1981, an advance of 50% of the DCS quotation

along with a letter of guarantee from the ADB-N has

been

required. This

procedure places more pressure on

the customer to expedite the

process.

After all the information has been

recorded

in the field

Most

customers turn to the ADB-N for financing. With

notes, the technical supervisor complete3 a price quota-

an interest rate of 11% and a loan repayment period of

tion based on the survey. Except for the penstock pipe

seven years, it offers better financial terms than com-

which varies considerably in price, most items cost

mercial banks. This loan also requires physical property

roughly the same from site to site. The cost of an

as collateral. A typical loan covers all the machinery

installation also depends on the types of processing

and installation costs, 85% of the land purchase, and

machinery to be included, but most customers want all 65% of the cost of the labor necessary to undertake the

three-a flour mill, rice huller, and oil expeller. The

excavation and to install the machinery. A typical

quotations are valid for only three months, after which

ADB-N loan covers about 80% of the entire project

a new quote must be obtained for the loan procedure. If

cost. Of the first 65 mills, only four have been paid for

the customer does not take delivery of the machinery without loans. The ADB-N has officers and personnel at

TABLE I0.L Dldaiun cr reqxmdbIli#ea for the fnatd&tion of a watercpowemd mill

Tasks undertakeu by Butwal Responsibilities

of

the mill owner

0 perform initial survey

l

design and fabricate turbine, penstock,

and other required hardware

l

obtain the necessary license to build and operate a mill

l

purchase the land and right-of-way for the power canal and

tailrace (as needed)

l

purchase, inspect, and pack the milling,

hulling, and oil expelling machinery for

transport

as

needed

l

provide technical guidance and

assistance in installing and

commissioning of the plant

l

arrange for water rights

l

locate sufficient cash to cover at least a portion of total cost of

the installation and apply for a loan

for

the balance necessary

l

organize local labor to undertake the necessary work

l

train one of the local persons designated

as mill operator how to operate and

maintain the machinery

o undertake the necessary excavation and collection of locally

available materials (sand, stone, gravel)

l

transport all the hardware and materials from Butwal to the site

236 Case studies

every level who actively promote a loan program for

water-powered mill development, having withdrawn a

similar program for diesel mills. When an application

has been received, a loan officer gathers information

about the econcmic feasibility of the project before

approving the loan. A customer who secures a loan

from the ADB-N receives a coupon, which he then sub-

mits to DCS. With this guarantee of payment, DCS will

deliver and install

the

mill, collecting payment directly

from the ADB-N upon submission of the bill signed by

the customer.

Generally, nearly a year elapses between the time a

team from Butwal visits the proposed site and the time

the customer places his order. During this time, the

customer surveys the land for his proposed site, gains

clear title to that land, and arranges for water rights

and the necessary financing.

Design, fabrication, and delivery

.4fter the customer places his order, the technical

supervisor fills

out

an order form. Based on the field

notes and sketches, any necessary modifications are

made to the standard designs. Only items that require a

special design, such as a penstock bend, need to be

redrawn. Items from India, such as grain-milling

machines, belts, pulleys, and bearings, are kept in stock

because of unreliable delivery times (Fig. 10.22). Items

Fig.

10.22.

A

recently received

stock of oil expellers from

India at Butwal.

such as penstock pipe, intermediate drive shaft, and

mounting frames are usually ordered in quantity for

str ck. Orders for items not already in stock, including

the turbine and penstock bends, are placed with BEW,

which fabricates them.

A year’s supply of grease and a tool kit adequate for

complete maintenance are supplied to the customer.

This solves the problem of a customer’s buying poor-

quality grease and the wrong tools. It also allows a field

team to perform maintenance work onsite even if it

does not bring its own tool kit.

After the customer has placed his order, he is also

responsible for preparing the site. The canal must be

built if an existing canal will not be used, the site for

the powerhouse has to be excavated, and all the neces-

sary materials that are available locally-stones, sand,

and aggregate-must be gathered in preparation for the

final construction effort (Fig. 10.231.

Fig. 10.23. A

major responsibility of the

mill owner

is

to

undertake the

necessary

excaation.

Here the excavation

for

the

tailrace

is under way, and excavation for the mill

house has been completed.

When the customer is ready, he must make full payment

for the equipment before it leaves the shop. Before the

equipment is packed

for

delivery, all the machinery,

parts, and supplies are checked against the order list.

One of the field teams assembles and checks parts

which are then packaged in loads that porters can carry.

The order is then ready to hand over to the owner, who

is responsible for arranging for porters to carry the

materials to the site (Fig. 10.24).

In addition to paying the outstanding balance on the

equipment, the customer pays the installation charge.

Formerly, the per-day installation charges were paid

after the mill was installed to give the customer some

leverage and to ensure his satisfaction with the work.

Because there has been some difficulty in collecting this

sum after the work has been completed, payment is now

Case studies 237

Fig.

10.24. After the site ercavntion has

been

completed

and

the

equipmeni

fabricated at

Butwal, porters carry

the

necessary

materials to

the site. The two section! of pen-

stock

shown weigh

about 100 kg.

required in advance. This sum is based on an installa-

tion time estimated at 30 days; if it is less, any over-

payment is refunded after completion

of the work.

Installation

The customer notifies the installation team from Butwal

to come after he has ensured that all the machinery is

at the site, that all materials noted on the project cost

form have been stockpiled near the site, and that all

necessary excavation work has been completed

(Fig. 10.25). The owner usually underestimates the dif-

ficulty of transporting

several

tons

of

machinery and

materials and the seasonal difficulty of locating porters.

Weighing 110 kg, the gear box for the oil expeller is the

single heaviest part and requires an exceptionally strong

porter. If the load can be supported on a sling, two por-

ters can to carry it. Because the trails are narrow and

steep, however, a load that must be carried by more

than one person is often passed up in favor of more con-

venient weights and sizes. The team takes any special

equipment needed for the installation, such as ropes,

Ffg. 10.25

Before the

instalIatfon team

arrives from Rut-

wal,

all

the

necessary

materials have &en

tmnsported to

the site.

mason’s tools, and a level. All of this fits easily into

their backpacks.

A per-day installation fee of Rs 180 is charged for the

work performed by the installation team. This rate,

which is considered extremely high

for

these remote

areas, encourages the customer to do as much of the

work as possible in advance and to supply labor to

reduce the installation time. Because the masonry

requires curhg time, it takes priority over other jobs.

The tailrace canal is prepared first, using stone masonry

for the floor ard dry stone for the sidewalls and top.

To install the penstock, turbine, and

draft

tube, Butwal

uses a unique approach that eliminates the need for

detailed and costly site surveys. These components are

first assembled and bolted together near their final

location and then temporarily braced by wooden cross-

frames or piles of stones (Fig. 10.26). The empty pipe is

strong enough to be self-supporting. The entire assem-

bly is then maneuvered around slightly until a suitable

alignment is found. Although this may be the most dif-

ficult part of the installation, this approach makes it

possible to circumvent boulders or other obstacles that

might have been encountered during the excavation. It

also makes it possible to compensate for small discrep-

ancies between the configuration of the penstock-tur-

bine-draft tube assembly designed according to data

gathered during the initial survey and the layout

of

the

area actually excavated. To facilitate this task further

when penstock bends are used, the bolt holes in one

flange of the bend are slotted to permit another degree

of freedom. In addition, an extra 1 m length of pen-

stock is supplied if needed. Any excess length

can

be

cut

off with a hacksaw blade. This method allows any

minor deviations to be accommodated easily, thereby

eliminating the need to interrupt work for several weeks

for a return to the Butwal workshop to fabricate

or

modify the penstock bends. After the turbine shaft has

been leveled, to reduce bearing loads and to simplify

alignment of the other machines, the turbine and draft

tube are secured in a foundation and the penstcck sup-

ports are built up.

238 Case studies

Fig.

10.26. The penstock, turbine, and dmft tube are all

assembled

and properly aligned before they

are set in con-

crete. A portion of the tailmce

canal has already been

completed.

The machines are all assembled on a mounting frame

and set in place (Figs. 10.27 and 10.28). Correct spacing

is assured by placing the belts on the pulleys. To ensure

that the shafts are parallel and the pulleys in line,

alignments must be done carefully using a string and

level. The string is stretched parallel to the turbine

shaft and the line shaft is adjusted parallel to it. The

string is also used to line up the V-belt pulleys from

their machined outer surface (Fig. 10.29). The mounting

frame is supported on rocks, allowing sufficient space

around the anchor bolts to place the concrete without

disturbing the frame.

The mill owner and whoever he has designated to help

operate the mill are encouraged to participate in fitting

and mounting the milling machines and transmission sys-

tem to understand how the parts fit together. The team

leader uses this opportunity to explain the need for

proper belt tension, adjustment of the machines, and

clean and adequate lubrication.

The team usually spends from three to four weeks at a

site to complete the installation. Because a few days

must be allowed for the masonry to cure before testing,

Fig. 10.27. The tailmce and

forebay have been completed

and

the processing equipment is being installed.

Fig. 10.28. All the equipment has been aligned and set in

concrete.

there are often a few free days between completion of

the installation and testing. This time is used to under-

take surveys of new sites nearby or to followup on mills

that may be already operating in the area.

After completing the installation, the team makes all

Case studies 239

Inversin R. Allen Micro-hydropower Sourcebook

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