CEA 4001 - Page 53

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53

F

Figure 5 – Jackwells or sunction pit

8.4.1.2

The

inlet

to

pipes

or

conduit

shall

be

submerged

at

least

1

diameter

below

the

lowest

known

water level.

The

depth'd'

of

water

in

open

channels

or

weirs

(including

the

weir

between

the

settling

chamber

and suction

chamber)

below

the

lowest

known

water

level

of

the

water

source

shall

be

not

less

than

that

specified

in

Table

14

for

the

corresponding

width

'w'

and

flow,

where

the

flow

is

the

maximum

flow

output

of

the pump,

i.e.

the

nominal

flow

for

LH,

OH

and

the

maximum

design

flow

for

HHP

and

HHS.

The

total

depth

of

open

channels

and

weirs

shall

accommodate

the

highest

known

water

level

of

the

water

source.

The

dimension

of

the

suction

chamber

and

the

location

of

suction

pipes

from

the

walls

of

the

chamber,

their submergence

below

the

lowest

known

water

level

(making

any

necessary

allowances

for

ice)

and

clearance from

the

bottom

shall

conform

to

8.3.5

and

Figures

4

and

5.

The

settling

chamber

shall

have

the

same

width

and

depth

as

the

suction

chamber

and

a

length

of

at

least

10d

where

d

is

the

minimum

bore

of

the

pipe

or

conduit,

and

not

less

than

1,5m.

8.4.1.3

The

chamber,

including

any

screening

arrangement,

shall

be

arranged

to

prevent

ingress

of

wind

borne

debris

and

of

sunlight.

8.4.1.4

Before

entering

the

settling

chamber

the

water

shall

first

pass

through

a

removable

screen

of

wire

mesh

or

perforated

metal

plate

having

an

aggregate

clear

area

below

the

water

level

of

150mm²

for

each

1/min

of

pump

nominal

flow

in

the

case

of

LH

or

OH

or

maximum

design

flow

for

HHP

or

HHS

.

8.4.1.5

The

inlet

to

the

pipe

or

conduit

feeding

the

settling

chamber

or

suction

pit

shall

be

provided

with

a strainer

having

an

aggregate

clear

opening

of

at

least

five

times

the

cross

sectional

area

of

the

pipe

or conduit.

The

individual

openings

shall

be

of

such

a

size

as

to

restrict

the

passage

of

a

25mm

diameter sphere.

Provision

shall

be

made

for

the

settling

chamber

to

be

isolated

for

periodical

cleaning

and maintenance.

Duplicate

supplies

shall

be

provided

with

separate

suction

and

settling

chambers.

The

screen shall

be

strong

enough

to

withstand

the

weight

of

water

should

it

become

obstructed

and

have

a

mesh

not greater

than

12,5mm.

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