Pumping Station Desing - Second Edition by Robert L. Sanks, George Tchobahoglous, Garr M. Jones

that

the

pump

selected

is the

best

fit, and

that

the

motor

and

electrical gear

are

sized adequately.

The

drawings

and

specifications

are

reviewed

by

the

owner,

and the

operators

are

walked through

the

design system

by

system. Final revisions

are

made

before

bidding

the

project.

Critique

Compare Figures 26-3, 17-21,

and

17-22.

The

choice

of

pumping station configuration

for

each

site should

be

based

on

sound judgment

in

which

first

cost

is

balanced against cleanliness

and

Figure

26-3.

Layout

of

redesigned

Clyde

pumping

station,

(a)

Plan

view;

(b)

Section

A-A.

desired control

of

odors

and the

ease

and

cost

of

maintenance.

Some operators prefer that

the

pump discharge lines

be

cross-connected with each other upstream

from

the

check valves (with

a

valve

on

each branch)

and

con-

nected

to the

force

main drain line,

as in

Figure 17-22.

Although

such piping increases

the

number

of

valves,

the

size

of the

valve

vault

and the

project cost,

it

allows

the

operator

to

agitate

the wet

well contents with

one

pump before pumping

to the

force

main with

the

other.

It

also allows

the

operator

to

backflow

one

pump

with

the

other

to

remove clogs without removing

the

pump.

The

pumps could

be

equipped with nozzles

as in

Figure

12-58c,

but

these pumps

are so

small that such

refinements

are of

debatable value.

The

plans

in

Figure 26-3 indicate

a

pyramid-

shaped hopper bottom.

To

keep

the

water

surface

area

as

small

as

possible

so

that scum will

be

readily drawn

into

the

pump intakes

at

pump-down,

the

sides

of the

sump

should

hug the

pump volutes with

no

more than

4 in. of

clearance. Instead

of

being

a

2-ft-by-4-ft

rect-

angle,

the

hopper bottom would

be

improved

if

rounded ends were used

and if the

clearance between

pump

volutes were reduced

to 4 in.

26-2.

Redesigned

Kirkland

Wastewater

Pumping

Station

Designed originally

in

1965,

the

Kirkland Pumping

Station

is

shown

in

U.S. customary units

in

Figures

17-

13

and

17-14,

so the

same units

are

used

in

this section.

The

station

has

been

in

continuous operation since

1967.

The

following example

is a

revised version

of the

existing station,

modified

to

reflect:

(1) wet

well design

developments that provide

the

self-cleaning features

described

in

Chapter

12; (2) the

best

in

current technol-

ogy;

and (3)

more recent

and

stringent reliability stan-

dards.

The

station consists

of

three

2.5

Mgal/d

pumps

operating against

a

total dynamic head

of

189

feet.

The top of the

influent

sewer

is no

more than

6 ft

below

finished

grade.

For

such

a

shallow site, horizon-

tal

pumps were selected

for

both

the

1965

and the

cur-

rent designs. Because they

are

less prone

to

vibration,

horizontal pumps

are

preferred when they

can be

jus-

tified

by

little

increase

in

structure

cost.

Instead

of the

eddy-current

couplings used

in the

original station,

the

revised design

has 125 hp

adjustable-frequency

drives.

A 300 kW

standby generator

is

provided

for

protection against power outages.

The

force main terminates

at an

interceptor sewer

3150

ft

from

the

pumping station site

at an

elevation

123 ft

above

the

soffit

of the

influent

sewer. Calcula-

tions

were performed

by

using PUMPGRAF© [1],

a

computer

spreadsheet

program configured specifically

for

pumping station design work.

Individual

Hydraulic

Losses

Calculations

for

individual hydraulic losses

from

the

pump

inlet

to the

connection with

the

discharge mani-

fold

were performed

first and are

shown

in

Table 26-2.

The

pump inlet

bell

diameter

in the wet

well

was

selected

on the

basis

of a

conservative limiting veloc-

ity

of 4.5

ft/s even though

the HI

Standards

[2]

pro-

posed

in

1997 allows

5.5

ft/s. Maximum velocities

in

pump

connecting piping were considered acceptable

for

a

variable speed station, where higher

losses

are

only realized when

the

equipment

operates

at

full

speed. Upon completion

of

these calculations, they

were automatically loaded into

the

program

for the

calculation

of

station

system

losses.

Station

System

Losses

Station system head losses

in the

force

main (including

static

lift)

were calculated

from

the

manifold

to the

point

of

discharge

and are

shown

in

Table 26-3. Instead

of

the

asbestos cement pipe used

in the

original project,

HDPE

was the

material selected

for the

force main.

Losses were initially calculated

for a

Hazen-Williams

C

of 140 and

then recalculated

for a C of

120. Individ-

ual

losses

for the

pump inlet

and

discharge piping

in

Table 26-2 were

not

included

in

these calculations.

Pump

Selection

Station system losses were then transferred through

the

program

to the

pump selection program (see Table

26-4),

and a

pump

was

selected

from

a

previously

entered library

of

pump manufacturers' catalog

infor-

mation.

A

plot

of the

selected

performance curves

against station system curves

is

shown

in

Figures 26-4

and

26-5.

The

pump performance curves plotted

on

the figure

have been adjusted

for

individual pump inlet

and

discharge piping losses

of 9.2 ft at 2.5

Mgal/d.

These

values must

be

added

to the

information

on the

plot

to

arrive

at the

correct rating

for the

pump.

In

this

example,

the

pumps

are to be

rated

at 2.5

Mgal/d

at a

total head

of

180

ft. The

pump selection

is

considered

acceptable, because

the

intersection between

the

pump

performance curve

and the

expected range

of

operat-

ing

conditions

lies

well within

the

manufacturer's pub-

lished data. Note that

the

intersection between

the

manufacturer's

curve

and the

station system curves

Table

26-2.

Pump

Intake

and

Discharge

Head

Losses

2.5

=

Starting

Flow

- mgd

Title:

Revised

Kirkland Pumping Station

119.98

=Elev@

Start

-Feet

Brown

and

Caidwell Consultants

140

=

Default

C-Value

>25

New

C;

14

°

HiGrf

LoGrf

PmpCorr

14

=

Default

Diam

-Inch

New D: 14

53.34

=

Target Head

Loss

304.8

=

Default Pipe Length

-

Feet

9

'

185

=

Total

Head

Loss

~

Feet

Date:

06-JuIy

96

ParaEq

=

3169

'

6

=

EqivLnth

(Std=def)

-

Feet

Flow,

Item Description

Diameter,

K or

Fixed

Length,

Loss,

Hyd

Grad,

ft

VeI, V-Hd,

mgd

of

Friction

Loss

in.

Cval

Loss

ft

Item

No. ft

Pmp

-> Dch fps ft

2.5

Bell Mouth Entrance

14

0.05

1

0.01

119.97

3.6 0.2

2.5

9O

0

EIbOW

10 0.3 2

0.23

119.74

7.1

0.78

2.5

Plug Valve

10 0.6 3

0.47

119.27

7.1

0.78

2.5

Reducer

10

0.01

4

0.01

119.26

7.1

0.78

2.5

PUMP

14

0.01

5

0.00

119.26

3.6 0.2

2.5

Increaser

6 1 6

6.03

113.23

19.

6.03

2.5

9O

0

EIbOw

10 0.6 7

0.47

112.76

7.1

0.78

2.5

Check Valve

14 3.5 8

0.71

112.05

3.6 0.2

2.5

Plug Valve

10 0.6 9

0.47

111.58

7.1

0.78

2.5

Branch Flow

Tee 10 1 10

0.78

110.80

7.1

0.78

2.5 11

Table

26-3.

Force

Main

Head

Losses

for

C=

140

5

=

Starting

Flow

-

mgd

Revjsed

Kirk

|

and

p

umping

Station

119.98

=Elev@

Start-

Feet

Title: Brown

and

Caidwell Consultants

120

=

Default C-Value

> 25 New C:

120

HiGrf PmpCorr

14

=

Default Diam

-

Inch

New D: 14 =

Target

Head

Loss

1000

=

Default Pipe Length

-

Feet

169.49

=

Total

Head

Loss

-

Feet

Date:

06-luly-96

ParaEq=

3341.6

=

EqivLnth(Std=def)

-

Feet

Flow, Item Description Diam,

K or

Length, Item

Loss,

HydGrad,

ft VeI

V-Hd,

mgd of

Friction

Loss

in.

Cval

Fixed

Loss

ft No. ft Pmp -> Dch fps ft

5

Fixed Static head

122 1

123.00

289.48

5

9O

0

EIbOw

14 0.6 2

0.49

288.99

7.2 0.8

5

Straight

Pipe

14 120 25 3

0.35

288.64

7.2 0.8

5

9O

0

EIbOW

14 0.3 4

0.24

288.40

7.2 0.8

5

Straight Pipe

14 120 140 5

1.95

286.45

7.2 0.8

5

45°Elbow

14

0.25

6

0.20

286.25

7.2 0.8

5

Straight Pipe

14 120

1040

7

14.47

271.77

7.2 0.8

5

9O

0

EIbOw

14 0.3 8

0.24

271.53

7.2 0.8

5

22°Elbow

14 0.1 9

0.08

271.45

7.2 0.8

5

Straight Pipe

14 120 975 10

13.57

257.88

7.2 0.8

5

9O

0

EIbOw

14 0.3 11

0.24

257.64

7.2 0.8

5

Straight Pipe

14 120 995 12

13.85

243.79

7.2 0.8

5

Outlet Loss

14 1 13

0.81

242.98

7.2 0.8

5 14

lies

to the right of the

pump's best

efficiency

point.

As

speed

is

reduced

in

variable speed operation,

the

point

of

intersection

of the

curves passes through

the

pump's

zone

of

best

efficiency.

After

an

acceptable pump selection

was

found,

the

program

was

used

to

evaluate pump performance

at

variable speed,

and

these data

are

shown

in

Table

26-5

and

in

Figure 26-5.

As

indicated,

the

minimum operat-

ing

speed

is

approximately

1300

rev/min,

which corre-

sponds

to a

rate

of

discharge

of 0.6

Mgal/d.

Hydraulic

Profile

Next,

a

plot

of the

force main

and

hydraulic profiles

was

constructed,

as

shown

in

Figure

26-6.

The

purpose

of

this

exercise

was to

provide

a

visual portrayal

of

hydraulic

conditions

in the

system

at

both minimum

and

maximum

system

capacity. From

an

inspection

of the

plot,

it was

found

that

the

hydraulic profile remains well above

the

force

main

profile

from

the

pumping station

to the

point

of

discharge under

all

operating conditions.

In

addition, there

appeared

to be no

high points

or

knees that would

be the

location

of

column separation

in a

hydraulic transient con-

dition. Finally,

the

pipe line

profile

does

not

touch

the

mir-

ror

image line,

so

column separation does

not

appear

to be

a

problem

(see

Section

7-1).

For a

21

-in.

force main con-

structed

of

HDPE,

the

wave propagation velocity

is

about

a

third

of

that

for

ductile iron

or

cement asbestos

(refer

to

Chapter

7).

Based

on

inspection

of the

force

main/hydrau-

lic

profile

plots

and the low

wave propagation velocity,

no

formal

transient analysis

was

judged

to be

necessary.

Geometry

The

station capacity

is 5

Mgal/d

or

7.75

ft

3

/s.

From

the

principles presented

in

Chapter

12, the

cross-

Name

Fairbanks

Morse

Nonclog,

4"

5414/5424

Crv/lmp—

T4D1

B,

3"

solids

Impeller

Rng

12.0

to

15.5

Speed

Rng

1 1

50

to

1

785

1

5.5

=

Impeller

for

Curve Points

1

785

=

Speed

for

Curve Points

Point/

Head,

Flow,

Eff/NPSH

ft

gpm

Head/Stg

290.00

0.00

267.00

400.00

62.00 248.00 800.00

70.00 232.00 1200.00

71.50 222.00

1400.00

72.80 212.00

1600.00

72.30

200.00 1800.00

70.50 188.00

2000.00

67.00 170.00 2200.00

64.00 158.00 2300.00

List

Up To 12

Points

In Any

Order.

Put

1st

Pump

Curve

Labels

First

Column

(Optional).

Imported

Data->Hi-Grf

Lo-G

rf

Pump Curve Calculations

2

=

Number

Pumps

For

Fixed Speed Pumps,

Omit

2nd,

3rd & 4th

Speeds

Data

For

Plot

14.70=

Impeller

for

Plot

1785.00=

Speed

for

Plot

=

Optional

2nd

Speed

=

Optional

3rd

Speed

=

Optional

4th

Speed

Pump Curve

Correction,

O if not

used

9.18feetPmpPipgLoss

2.50

mgd

Flow Used

Overriding

System Head Curve Data

0.00

mgd

=Design Flow

100.00

=

C-

Value

for

Friction

Loss

11

.01

feet

=Frtn

Loss

@

DgnFlo

50.00

feet

=High

Static Head

50.00

feet =Low Static Head

120.00

=Low

C-

Value

140.00

=High

C-

Value

1

.40

=Peak Factor

Sys

Head

C

=

120.00

Hi-SysHd Curve Label

C

=

140.00

Low-SysHd Curve Label

1

785.00

1 st

Pump Curve Label

Table

26-4.

Pump

Selection

for Two

Pumps

Operating

ENTER

PLOT DATA RIGHT: Title

-->

Revised Kirkland Pumping Station

ENTER

PUMP DATA BELOW: Brown

and

Caldwell

Consultants

Delete

or

Add --> 2nd

Pump Curve Label

Curve

Labels

--> 3rd

Pump Curve Label

To

Suit

--> 4th

Pump Curve Label

sectional area

of the wet

well above

the

trench should

be

sufficient

to

limit

the

average forward (plug

flow)

velocity above

the

trench

to 1

ft/s

for any

inflow.

At

the

maximum

inflow

of 5.0

Mgal/d

a

cross-sectional

area

of

7.75

ft

2

is

required,

and at

half

the flow

with

the

inlet pipe half

full,

the

required cross-sectional

area above

the

trench must

be no

less

than 3.88

ft

2

.

In

Figure

26-4.

Pump

and

system

curves

for two

pumps

in

parallel.

Revised

Kirkland

Wastewater

Pumping

Station.

this design,

the

second criterion

is the

more critical

and

results

in

locating

the top of the

trench

4.0 in.

below

the

invert

of the

influent

pipe.

If the

sides

are

allowed

to

slope

at

45°,

the wet

well above

the

inlet

pipe

can be

made

5 ft

wide. Note that installing

the

sluice gate requires

a flat

surface

at

least

12 in.

wider

than

the

diameter

of the

inlet

pipe.

Figure

26-5.

Pump

and

system

curves

for a

single

vari-

able-speed

pump.

Revised

Kirkland

Wastewater

Pump-

ing

Station.

Figure 26-6.

Plot

of

force

main

and

hydraulic

profiles.

Revised

Kirkland

Wastewater

Pumping

Station.

Pump

Intakes

The

dimensions

of a

ductile iron bend

and flare

were

judged

to be

unfavorable

(see Example 12-4, Part

B), so

a

special

fitting

consisting

of a

short radius steel

90°

bend

welded

between

a 14 x 10

reducer

(with

an OD of 14 in.

or

1

.

17

ft) and a

steel

flange was

selected.

The

trench

was

made

2.33

ft

wide

—

equivalent

to 2

bell diameters.

Intake

Submergence

Submergence,

governed

by

Equation

12-1,

was

calcu-

lated

to be 3.0 ft.

(Details

of a

somewhat similar

cal-

culation

are

given

in

Example 12-4, Part

D.) As LWL

is to be set at the

invert

of the

inlet pipe,

the

pump

intakes

should

be at

least

3.0 ft

below

the

invert

or

2.72

ft

below

the top of the

trench.

The two

pump

intakes nearest

the

influent

sewer should

be

placed

D/

2 (7

in.)

above

the floor. The

depth

of the

trench

should

be 2.5 D or

2.92

ft.

The

pump

farthest

from

the

influent

sewer should

have

its

inlet located

D/4 or 3.5 in.

above

the floor of

the

trench.

The

minimum center-to-center spacing

of

pump

intakes should

be at

least

2.5 D or

2.92

ft.

Plans

The

plans, shown

in

Figures 26-7 through 26-9, illus-

trate

the

conceptual design

for the

revised station.

Because

the

station must

be

located

on a

very small

site,

the

pump inlets were located

at the

minimum per-

missible separation

so as not to

encroach

on the

space

needed

for the

engine-generator.

The

pump inlet

pip-

ing

for

Pumps

2 and 3

were skewed

to

permit

the

Table

26-5.

Operation

of a

Single Pump

at

Variable Speed

ENTER

PLOT DATA RIGHT:

Title

-->

Revised Kirkland

Pumping

Station

ENTER

PUMP

DATA BELOW: Brown

and

Caldwell

Consultants

Name

Fairbanks Morse

Imported

Data->Hi-Grf

Lo-Grf

Nonclog,

4"

5414/5424

Pump Curve Calculations

„

/,

-r^r^iD

0»

i-j

1 =

Number

Pumps

Crv/!mp—T4D1B,

3"

solids

.-

...

,

c

,

D

M

For

Fixed Speed

Pumps,

Omit

2nd,

3rd & 4th

Speeds

Impeller

Rng

12.0

to

15.5

Data

For

Plot

14.70=

Impeller

for

Plot

Speed

Rng

1150

to

1785

!

7

85.OO

=

Speed

for

Plot

15.5

=

Impeller

for

Curve Points

1600.00

=

Optional

2nd

Speed

1

785

=

Speed

for

Curve Points

1450

-°°

=

Optional

3rd

Speed

NmbrStgs

=

1.00

1300.00

=

Optional

4th

Speed

Point/

Head,

Flow,

Eff/NPSH

ft

gpm

Head/Stg

Rump

Curye

Correction/

0

jf

not

used

290.00

0.00

9-

1

8

feet

Pmp

Pipg

Loss

267.00

400.00

2.50

mgd

Flow Used

62.00 248.00 800.00

70.00

232.00

1200.00

Overriding

System

Head

Curve Data

71.50 222.00

1400.00

0-00

m

gd

=Design

Flow

72.80

212.00

1600.00

1

°°-

00

=

C-Value

for

Friction

Loss

72.30

200.00

1800.00

11

-

01

f

get

=

Fr

tn

Loss

@

DgnFlo

70.50 188.00

2000.00

50.00

feet

=High

Static

Head

67.00

170.00

2200.00

50.00

feet

=Low

Static

Head

64.00 158.00 2300.00

120.00

=Low

C-Value

140.00

=High

C-Value

List

Up To 12

Points

In Any

Order.

1

-40

=Peak Factor

Sys

Head

Put 1st

Pump

Curve

Labels

First

4.50

=Curvature factor

Column

(Optional).

C =

120.00

Hi-SysHd

Curve Label

Delete

or Add -->

c

=

140.00

Low-SysHd Curve Label

Curve

Labels

-->

1785.00

1 st

Pump Curve Label

To

Suit

-->

1600.00

2nd

Pump Curve Label

1450.00

3rd

Purnp

Curve Label

1300.00

4th

Pump Curve Label

Figure

26-7. Ground floor plan.

Revised

Kirkland Pumping Station.

Figure

26-8. Section A-A.

Revised

Kirkland Pumping Station.

pumps

to be

located

with

a

clear separation

of 3.5 ft

between

bases.

The wet

well

has

been revised

to

include

an

ogee

ramp

and a

motor-operated sluice gate

to

improve

the

effectiveness

of the

cleaning operation. Instead

of

locating

a

grated

walkway

over

the

pump inlet chan-

nel as in the

original design,

a

walkway alongside

the

channel

makes access

far

more convenient

for

house-

keeping chores (such

as

hosing grease

off the

walls).

Instead

of a

spiral stair (permissible under then-

prevailing

codes),

a

conventional stairway

for

access

from

grade level

to the

pump room

is

used

in the

revised design.

All

station auxiliaries (water pumps,

hydropneumatic

tank,

air

compressors)

are

located

on

an

L-shaped bench along

the

south

and

east walls.

To

conserve space

at

grade level,

all

cabinets

for

electri-

cal

equipment (instead

of

being located

in a

separate

room with

a

controlled climate)

are to be

furnished

with

an

internal cooling system.

Critique

The

suction bells, spaced

at 2.5 D on

centers, could,

perhaps,

be

spaced

at 2.0 D on

centers

(as

shown

for

unconfined

wet

wells

in an

older edition

of the HI

Standards

[3])

and

thereby save

14 in. of wet

well

length.

But the

greater spacing

is

more conservative,

and

still

keeps

the wet

well very short. Whether

to

keep this spacing

and

splay

or

bend

the

suction pipes

or to use

rectilinear piping

(as in the

original shown

in

Figure

17-13)

and a

much longer

wet

well

is a

mat-

ter of

engineering judgment.

One

disadvantage

of the

plans shown

is

that

if the

suction piping

for

Pump

No. 3

ever clogs,

it

would

be

more

difficult

to rod out

debris

than

it

would

be for a

straight

pipe.

The

need

for

rodding, however,

is

rare because

of the

protec-

tion

afforded

by

setting

the

pump intakes

at

relatively

small

floor

clearances.

The

pump intake piping will

be fitted

with

flush-out

connections

to

permit clearing

the

pipe

with high-pressure water. Mitered bends

of a

radius long enough

to

pass rodding equipment could

be

used

as an

alternative. Another disadvantage

is

that, because

of the

elbow connection,

the

distance

from

the

back wall

to the

center

of the

pump intake

is

1.0 D

instead

of the

preferred

0.75

D. The

latter

dis-

advantage

can be

overcome

by

adding vertical

fillets

at

the

corners

of the

back wall

to

inhibit vortex for-

mation

in the

stagnant water downstream

of the

intake.

26-3. Jameson Canyon

Raw

Water

Pumping

Station

The

Jameson Canyon Pumping Station

was

con-

structed

to

replace

an

existing installation

at the

Cache

Slough Reservoir, which receives water

from

the

Figure

26-9. Section B-B.

Revised

Kirkland

Pumping Station.

Sacramento River system

and

delivers

it to the

City

of

Vallejo,

California, Fleming Hill Water Treatment

Plant.

In

addition

to the new

pumping station,

the

project

included construction

of a

parallel pipeline

from

the

reservoir

to the

treatment plant

on an

align-

ment

through Gordon Valley.

The

original station,

which

has

been retained

and

modified

to

function

as a

reserve

facility,

was

found

to be

troublesome because

of

capacity-limiting inlet conditions

and

other defects.

In

addition

to

Pumping Station Desing - Second Edition by Robert L. Sanks, George Tchobahoglous, Garr M. Jones

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