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

1.02F

formance

from

model tests

or

from

the

performance

at a

single test speed will

not be

permitted. Should

the

man-

ufacturer's

testing facilities

be

limited

to

constant-speed

pump drivers,

a

test curve

may be

developed utilizing

the

constant speed closest

to the

rated condition point

on the

test curve.

In any

event, test data shall

be

suffi-

ciently comprehensive

to

produce guaranteed performance curves showing head versus capacity,

efficiency,

and

brake

horsepower

for the

rated speed plus

or

minus

10

percent

and at one

other lower speed, preferably

at

con-

dition point

C. The

test data shall

be

corrected

to the

rated speed

and the

speed

at

condition point

C by the

meth-

ods

outlined

in the

Hydraulic Institute Standards. Five

certified

copies

of all

original test data, calculations,

and

final

performance

curves shall

be

furnished

to the

Engineer

for

acceptance before shipment

of the

equipment.

The

Contractor shall submit

a

sketch

of the

proposed test setup, along with

a

description

of the

proposed test-

ing

procedure

to the

Engineer

for his

review

at

least

10

weeks

in

advance

of the

proposed testing date.

No

tests

shall

be

performed until

the

test procedure meets with

the

Engineer's approval.

In

addition,

the

Contractor shall

furnish

the

Engineer with

at

least

4

weeks advance written notice

of the

date

and

location

of the

witnessed per-

formance

tests.

The

results

of the

factory tests shall

be

considered

official

and

conclusive

for the

purpose

of

determining

whether

or not the

equipment complies with

the

performance specifications. Final acceptance

of

the

equipment will depend

on

satisfactory operation

after

installation.

4.

MOTOR TEST: Motors shall

be

tested

in

accordance with NEMA

and

IEEE procedures.

The

test shall

include

the

following:

a.

Routine test:

1)

Running—no-load

amperes

2)

Locked rotor amperes

3)

Winding resistance,

DC

4)

High-potential test

at

twice rated voltage plus 1000 volts, with

a

minimum

of

2200 volts

for 1

minute,

winding

to

ground

b.

Complete test:

1)

Rated load temperature rise

2)

Slip

in

percent

3)

Locked rotor amperes

(3

phase,

full

voltage)

4)

Locked rotor torque

5)

Breakdown torque

6)

High-potential test (see

4

above)

7)

Efficiencies

tabulated

at

100,

75, and 50

percent

of

full

load

8)

Power

factor

tabulated

at

100,

75, and 50

percent

of

full

load

The

Contractor shall

furnish

the

Engineer with

five

certified

copies

of the

results

of all

tests.

G.

SHIPMENT

OF

PUMPING UNITS:

Pumping

units

to be

furnished

under this contract shall

be

shipped

to the

site

in

enclosed, weather-tight,

sealed containers

in a

manner designed

to

protect

the

pumping units against damaging stress caused

by

sudden

acceleration

or

deceleration.

A

recording accelerometer, designed

to

record

the

magnitude

of any

sudden impact

in

all

three directions

(X,

Y, Z) on

continuous strip charts, shall

be

shipped with

and fixed to

each assembly

or its

packing

crate. Upon arrival

of

each shipment,

the

accelerometer shall

be

removed

in the

presence

of

representa-

tives

of the

Engineer,

the

Contractor,

and the

equipment manufacturer.

If the

magnitude

of the

maximum accel-

eration exceeds

3.0

times

the

acceleration

due to the

force

of

gravity (3.0

g),

the

assembly

or

subassembly shall

be

dismantled

and

completely inspected.

All

damage shall

be

corrected before

the

assembly

is

incorporated into

the

work.

The

Contractor shall bear

all

costs arising

out of

dismantling, inspection, repair,

and

reassembly.

1.03 ENVIRONMENTAL CONDITIONS

The

equipment

to be

provided under this section shall

be

suitable

for

installation

and

operation

at

elevations

of

about

10 and

150

feet above

sea

level inside weather-protected structures. Outside ambient temperatures

range

between

10 and

95

0

F,

and

reported wastewater temperatures vary between

47 and

65

0

F.

Relative humidity

is

expected

to

range between

5 and 100

percent.

1.04G

1.04 SUBMITTALS

The

information listed below shall

be

submitted

to the

Engineer

for

review

in

accordance with Section

01300.

The

submittal shall,

as a

minimum, include

the

following data drawings

and

other descriptive material:

A.

Shop drawings

to

describe

and

show pump construction

and

materials.

B.

Pump performance curves showing

the

head, capacity, speed,

efficiency,

and

brake horsepower required

when

operating

at

specified conditions. Pump curves shall include

a

minimum

of

four

pump curves

approximately equally spaced between minimum speed

and

full

operating speed with

a

minimum

of

four

points each including shut-off head

and

maximum capacity.

C.

Reed

frequency

for

motor

and

pump rotors.

D.

Mass elastic system calculations.

E.

Complete calculations

for

bearing

and

shafting

selection necessary

to

determine size, material,

and

styles.

F.

All

motor information

as

outlined

by

this specification.

1.05 INFORMATION

TO BE

PROVIDED

1.

Certified

copies

of all

material test reports.

2.

Certified

copies

of all

performance tests

on

both pump

and

motor.

3.

Manufacturer's certification that

the

pumping units

and

variable-speed control equipment

are

fully

in

con-

formance

with

the

requirements described

and

depicted

in

this project manual.

4. O&M

manual information

in

accordance with Section

01730.

2.01

PART

2—PRODUCTS

2.01 MATERIALS

Component Material

Suction nozzle, volute casing, back

head,

impeller

Cast

iron,

ASTM A48,

Class

3OC,

close

grained

with

2 to 3

percent

nickel

Bearing

frame

and

housing Cast iron, ASTM A48,

Class

3OC

Shaft

Steel,

ASTM A322, Grade 4140,

or

equal

Wear

rings Stainless

steel,

ASTM type 405; minimum

Brinnell

hardness

450, casing; 350, impeller

Shaft

sleeve Stainless steel, ASTM A276, type 405; minimum Brinnell

hardness

500

Bolts, studs, nuts Stainless

steel,

ASTM A276, type

316

2.02 EQUIPMENT

A.

GENERAL:

Each pumping unit shall consist

of a

custom engineered heavy-duty vertical nonclog pump, vertical alternat-

ing

current induction motor,

and all

necessary

shafting,

couplings,

and

support bases.

The

pumping unit shall

be

capable

of

operating

at

variable speed without cavitation

or

damaging vibration over

the

specified range

of

flow

and

head conditions.

The

pumping units shall also

be

suitable

for

adjustable-speed

operation

by

means

of

a

variable-frequency drive

as

specified

in

Section

16158.

B.

PUMPS:

1.

SUCTION HEAD

AND

NOZZLE: Each suction head shall

be

cast separately

from

the

casing

and

shall

be of

one

piece close-grained cast iron containing

2 to 3

percent nickel

and

conforming

to

ASTM A48, Class

30.

Each

suction

elbow shall

be

fitted

with

a

4-inch hand hole

for

access

to the

impeller, shall

be

tapped

and

fitted

with

a 1-

inch

drain cock

and

shall

be

drilled

and

tapped

for a

1-inch

gauge connection.

[Author's

note:

The

manufacturer's

standard

construction provides

a

gauge connection

adjacent

to the

suction

flange.] The

inner contour

of the

hand

hole shall exactly match

the

contour

of the

suction elbow.

The

drain cock shall

be

located

in the

suction nozzle

below

the

hand hole. Each suction nozzle shall

be

equipped with

125-pound

ASA

standard

flange as

follows:

Pumps

Size,

inches

P331,001,

P331,002,

P330,001,

and

P330,002

8

P331,003,

P331,004,

P330,003,

and

P330,004

16

2.

BASE:

A

rigid steel fabricated base shall

be

firmly

bolted

to the

casing. Large openings

on all

sides shall

permit

free

access

to the

suction

and

hand hole, drain

and

gauge

fittings.

Anchor bolts shall

be

embedded

in the

concrete

floor in

accordance with

the

pumping unit manufacturer's recommendation. Bases

for

pumps

P331,001,

P331,002,

P330,001,

and

330,002 shall

be

designed such that

the

anchor bolt locations match those

recommended

for the

bases

of

pumps

P331,003,

P331,004,

P330,003,

and

P330,004.

2.02B

3.

CASING: Each casing shall

be

made

of

close-grained

cast iron containing

2 to 3

percent nickel

and

conforming

to

ASTM A48, Class

30. A

4-inch hand hole shall

be

provided

on the

discharge nozzle side

of

each casing

to

permit inspection

of the

impeller.

The

inner contours

of

each hand hole cover shall exactly

match

the

contours

of the

casing

in

which

it fits.

Each casing shall

be

provided with

lifting

eyes

or

other

means

for

conveniently attaching hoisting bridles

at not

less

than three

points.

The

surfaces

of all

water pas-

sages shall

be

smooth

and

free

from

all

pits

and

projections which might cause undesirable turbulence. Each

casing shall

be

equipped with

a

1-inch

drain

and

plug. Each discharge nozzle shall

be

drilled

and

tapped

for a

1-inch

gauge connection,

and a

valved

1-inch

air

vent shall

be fitted to the top of

each discharge nozzle. Each

discharge nozzle shall

be

equipped with

a

125-pound

ASA

standard

flanged

discharge

fitting of at

least

the

following

size:

Pumps

Size,

inches

P331.001,

P331,002,

P330,001,

and

P330,002

6

P331,003,

P331,004,

P330,003,

and

P330,004

12

4.

BACK HEAD:

The

back head shall

be so

constructed

as to

allow

the

complete removal

of the

impeller,

shaft,

and

bearings

without

disturbing

the

pump suction

or

discharge piping.

The

back head shall

be

accu-

rately machined

to

provide

a

self-centering

fit

with

the

volute casing

and

frame

and

shall

be

drilled

and

tapped

for the

installation

of a

1-inch

seal water drain designed

to

minimize standing seal water within

the

back head.

The

back head shall contain

a

stuffing

box of

sufficient

depth

to

ensure trouble-free

operation.

Large

[Authors'

note:

This

depends

on

size

of

pump

and

manufacturer.]

openings shall

be

provided adjacent

to the

stuffing

box to

permit packing replacement

and

adjustment.

The

gland shall

be of the

split removable type, con-

structed

of

bronze.

The

stuffing

box

shall contain

a

split bronze lantern

ring and

shall

be

drilled

and

tapped

for a

clear water seal. Each lantern

ring

section shall

be

drilled

and

tapped

for a

1/4-20 thread

to

permit removal

by

means

of a

special threaded tool

to be

furnished

with

the

spare parts.

5.

FRAME:

The

frame

shall

be of

cast iron

and

shall

be

designed

to

carry both radial

and

thrust bearings.

Large openings shall

be

provided adjacent

to the

stuffing

box to

permit packing replacement

and

adjustment.

The

frame

shall

be

provided with accurately machined self-centering

and

self-indexing

fits

with their back

heads

to

ensure proper alignment

of

bearings

and

stuffing

box.

6.

IMPELLER: Each impeller shall

be of the

one-piece, single suction, two-vane

or

three-vane, enclosed,

nonclog

centrifugal

or

nonclog,

mixed-flow

type.

All

exterior surfaces shall

be

accurately machined,

and all

water passages shall

be

smooth

and

free

from

hollows, cracks, pinholes,

and

projections which might incite

or

encourage

cavitation.

Each

impeller

shall

be

keyed

to the

shaft

and

locked

in

place

with

a

threaded

fastener

designed

to

prevent accumulation

of

stringy material.

7.

WEARING RINGS: Removable wearing

rings

shall

be

provided

for

both

the

impeller

and the

suction

head

of

each pump. Wearing

rings

shall

be

nongalling, heat-treated stainless steel with

a

chrome content

of not

less than

11

percent. Impeller

rings

shall have

a

Brinell hardness

of not

less than 300. Casing

ring

hardness shall

exceed impeller ring hardness

by not

less

than

100

points

on the

Brinell

scale.

The

impeller

and

suction head

rings

shall

be so

designed

as to be

easily

and

readily replaceable. Wearing

rings

shall preferably

be

attached

by

screwed fasteners.

8.

SHAFT: Each pump

shaft

shall

be of

heat-treated, high-strength steel, turned, ground,

and

polished.

Shafts

shall

be of

ample strength

and

stiffness

to

operate without distortion

or

vibration throughout

the

range

of

service

specified.

The

section

of

shaft

fitting

between radial

and

thrust bearings shall

be of

sufficient

section

to

limit

deflection

at the

impeller centerline

to not

more than

6

mils when

the

pump

is

operating

at the

minimum sus-

tained

flow,

continuous-duty point,

as

defined

under paragraph 1.02D.

Shaft

deflection

shall

be

calculated using

the

following

relationship:

2.02B

Y

-

y

r(V,a

3

-frVV|

A

max

^F

\

J

7

3&^l

b

y

a

1

Cj

where

7

max

=

deflection, inches

E

=

modulus

of

elasticity,

psi

30 x

10

6

psi for

carbon steel

28

x

10

6

psi for 316

stainless steel

a

=

shaft

length,

inches,

from

impeller

centerline

to the

centerline

of the

radial bearing

b

-

shaft

length, inches, impeller centerline

to

shaft

sleeve shroud

at

radial bearing

c =

shaft

length between bearings, inches

/

a

=

moment

of

inertia

of the

shaft

just outboard

of the

radial bearing,

in.

4

/

b

=

moment

of

inertia

of the

shaft

under

the

shaft

sleeve,

in.

4

/

c

=

moment

of

inertia

of the

shaft

between

the

radial

and

thrust bearings,

in.

4

W

r

=

radial force, pounds

=

KHD

2

B

2

where

H

=

total head, pounds

per

inch

D

2

-

impeller diameter, inches

B

2

=

impeller width, including shrouds, inches

-°4-©l

where

Q

=

pumped

flow at

condition

C

Q

n

=

capacity

at the

pump's best

efficiency

point

9.

REPLACEABLE SHAFT SLEEVE:

The

section

of

each

shaft

or

impeller

hub

which extends through

or

into

the

stuffing

box

shall

be fitted

with

a

replaceable, hardened chromium stainless-steel sleeve with

a

Brinell

hardness

of not

less than 500.

The

sleeve shall

be

held

to the

shaft

to

prevent rotation

and

shall

be

gasketed

to

prevent leakage between

the

shaft

and the

sleeve. Minimum

shaft

sleeve thickness shall

be

1

I

2

inch.

10.

BEARINGS: Each pump shall

be fitted

with

two

sets

of

shaft

bearings conservatively designed

to

with-

stand

all

stresses

of the

service specified herein. Bearings shall

be of the

antifriction grease-lubricated type.

The

bearing nearest

the

impeller shall

be

capable

of

carrying

all

radial thrust loads, while

the

outboard bearing shall

be

capable

of

carrying some radial load

as

well

as the

unbalanced hydraulic thrust.

All

bearings shall

be

rated

in

accordance

with

AFBMA

L-IO

for a

continuous

(24

hours/day) duty

life

of not

less than

50,000

hours

at the

most

severe loads imposed

by the

specified continuous-duty conditions (condition points

A and C,

paragraph

1.02D).

Calculations substantiating

the

bearing selections shall

be

submitted

to the

Engineer with

the

pump sub-

mittals. Pressure grease

fittings

shall

be

provided

for

bearing lubrication. Only standard commercial bearing

sizes shall

be

used. Grease

fittings

shall

be

Alemite hydraulic type.

11.

BALANCE: Each rotating assembly, including coupling,

shaft

impeller with wearing rings,

and

impeller

nut,

shall

be

dynamically balanced prior

to final

assembly.

[Editor's

note:

This

stringent

specification

requires

the

manufacturer

to

assemble

and

disassemble

the

rotor several times, requires

the use

of

balancing machines

not

usual

in a

production

line,

and

results

in

only

a

little

added

precision. Individual balancing

of

components

(not

assemblies)

and

dynamic

balancing

only

for the

impeller

and

coupling

may be

adequate.

Mass

unbalance

forces

are

insignificant

compared

with

hydraulic unbalance

forces.]

When

properly balanced, each rotating element shall meet

the

following minimum criteria

at

speeds varying

from

50

percent

of the

maximum

up to

maximum operating

speed.

When properly balanced, each rotating ele-

ment

shall meet

the

following

at

every point throughout this range:

2.02B

Maximum

speed,

rpm

Maximum

amplitude

peak

to

peak,

inches

600

0.0035

720

0.0033

900

0.0025

1200

0.002

1800

0.0013

The

Contractor shall

furnish

five

certified copies

of all

logs

to

demonstrate that

all

rotating elements have

been balanced

in

accordance with these specifications.

All

balancing logs shall

be

submitted

to and

accepted

by

the

Engineer

as a

condition precedent

to

shipment

of the

equipment

from

the

factory.

C.

VERTICAL DRIVE SHAFTS:

Each pump shall

be

provided with

two

sections

of

tubular

shafting

for

connection

to the

motor driver.

Shaft-

ing

shall

be

complete, with

flexible

couplings sized

to

carry

the

loads

of the

intended service

and a

shaft

guard

which

shall extend

3

feet

above

the

pump

frame

or 7

feet

above

the floor,

whichever

is

greater.

The

bearing shall

be of the

heavy-duty, self-aligning spherical-roller, expansion type

3

capable

of a

free

vertical movement

of

1

I

2

inch

and

shall

be

designed

for

AFBMA

L-IO

continuous-duty

life

of not

less than

50,000

hours with

I

1

I

2

degrees misalignment.

All

grease

fittings

shall

be

mounted

in an

approved readily accessible location.

The

shaft-

to-hub

connection

of

each

end

shall

be by

means

of a

keyless mechanical device which exerts

an

external

clamping

force

on the

connections

and

which does

not

require

the

application

of

heat

for

removal

of the hub

from

the

shaft.

Shafts

shall employ universal-type

flexible

couplings

and

shall have grease-lubricated needle bearing univer-

sal

joints

and

splined slip joints. Universal-joint-type

shafts

shall

be

offset

to the

manufacturer's recommenda-

tions

and

shall

be as

manufactured

by the

H.S. Watson Company, Twin Disc, Inc.,

Parrish

or

equal.

[Authors'

note:

Balancing

is

specified

in

2.02B.II

and

2.02D.7.]

D.

ELECTRIC MOTOR DRIVERS:

1.

GENERAL: Each motor shall

be

designed

for

variable-speed service

in

conjunction with

the

variable-

frequency

drive controllers

as

specified under section

16158.

Motors shall

be

designed with torque characteris-

tics

equal

to

those required

for the

pumping units,

and

total load applied

to the

motor

by the

driver equipment

and

variable-frequency drive system shall

not

exceed

90

percent

of the

motor's nameplate rating. Each motor

shall

be

designed

to

withstand

a

reverse overspeed

of 150

percent

of

rated synchronous

speed.

Motors shall

be

three-phase, squirrel-cage induction types designed

for 460

volts,

60 Hz, and

maximum

kVA

inrush

current shall

be

NEMA Code

F.

Each motor shall

be of

vertical, solid-shaft,

"P"

base construction

and

shall,

as a

minimum, meet

the

requirements

of

NEMA

M61-1978.

Temperature rise shall

not

exceed

80

degrees

C

above

a 40

degrees

C

ambient when operated

at

full

load. Insulation shall

be

NEMA Class

F, and the

motor

shall have

a

1.15

service

factor.

Enclosures shall

be

NEMAWPI.

Each motor shall

be

provided with

a

minimum

of

two

lifting

eyes.

2.

THERMAL PROTECTION: Thermal protector sensing elements shall

be of the

same manufacture

and

shall

be

coordinated with

the

thermal protecting relay.

The

sensing elements shall

be

embedded

and

sealed

in

the

end

winding

of

each stator phase.

The

sensing elements

of all

three phases shall

be

connected

in

series

and

the end

leads brought

out to a

conduit

fitting as

shown.

The

thermal protector relay contacts shall

be of

ample capacity

to

operate

the

motor starter control circuits

as

shown.

The

protector relay shall drop

out on

overtemperature.

Information

shall

be

supplied

to the

Engineer regarding

the

characteristics

of the

thermal device

and its

required control circuit protective device.

The

thermal devices shall

be

designed

to

operate

at 10

degrees

C

above

the

total temperature specified

in

paragraph

2.02D.1.

3.

SPACE

HEATERS:

Each motor shall

be

provided with

a

space heater. Heaters shall

be

carriage type

or

flexible

wraparound

type installed adjacent

to the

core iron. Heaters shall

be

rated

120

volts, single phase.

The

2.02D

space heater terminals shall

be

separately wired

to a

terminal block

or

pigtails

in the

power conduit box. Space

heater rating

in

watts

and

volts shall

be

noted

on the

motor nameplate.

4.

BEARINGS: Motor bearings shall

be of

high-precision manufacture, antifriction type designed

for an

AFBMA

L-IO

continuous-duty

life

of

70,000

hours. Bearings shall

be

provided with pressure-type lubrication

fittings

with removable plastic

cap

protective covers

and

grease drain with threaded, removable drain plugs.

5.

CONDUIT BOX: Motors shall

be

fitted

with

a

cast-iron conduit

box

provided with threaded hubs. Con-

duit

boxes shall

be

provided with gaskets

at the

base

and

between

the

halves

of the box and

shall

be

capable

of

360

degree rotation

for

mounting

and for

bonding

of a

ground conductor employing

a

stud

or

grounding

pad

inside

the

box.

A

separate cast-iron signal conduit

box

shall also

be

provided

for

temperature detection leads.

6.

MOTOR SUPPORT PEDESTAL: Each motor shall

be

mounted

on a

support pedestal designed

to

carry

the

motor weight

and the

weight

of the

vertical

shafting

plus

all

dynamic loads associated with

the

operation

of

the

unit.

The

pedestal shall

be

designed with adequately sized openings

to

permit access

to the

upper universal

joint

of the

drive

shaft.

The

openings shall

be

protected

by

easily removable stainless

steel

guards.

The

guards

shall

be of

comparable quality

to the air

grille

on the

motor.

7.

BALANCE: Each impeller

and

each rotating assembly, including coupling half,

shaft

and

rotor shall

be

dynamically

balanced prior

to final

assembly.

Dynamic

balancing shall

be

accomplished

by

supporting

the

rotating element

in its

bearings

and

turning

the

element

at

speeds

varying

from

50

percent

of

maximum

up to

maximum operating

speed.

When properly bal-

anced, each rotating element shall meet

the

following criteria

at

every point

in

this range:

Maximum

operating

speed,

rpm

Minimum

amplitude

peak

to

peak,

inches

600

0.0010

720

0.0010

900

0.0010

1200

0.00075

1800

0.0005

The

Contractor shall

furnish

five

certified

copies

of all

logs

to

demonstrate that

all

rotating elements have

been balanced

in

accordance

with

these

specifications.

All

balancing logs

shall

be

submitted

to the

Engineer

for

his

review

and

acceptance

as a

condition relevant

to final

shipment

of the

equipment.

E.

SPARE PARTS:

Furnish

to the

Owner

the

following spare parts

for

each size pumping unit:

1

each, each type

of

coupling

2

sets,

all

gaskets

1

each, impeller

hub or

shaft

sleeves

1

each, impeller

2

sets, complete replacement

all

packing

1

each, lantern

rings as

specified

1

set, each type

of

bearing

1

each,

stuffing

box

gland with bronze bolts

and

nuts

1

set, special tools

as

required

for

pumping unit disassembly

PART

3—EXECUTION

3.01 INSTALLATION

The

pump supplier shall provide

the

complete pumping system

and

factory-trained personnel

to

supervise

installation

and

initial operation

of all

components.

The

pumps shall

be

aligned, connected,

and

installed

at the

3.01E

locations shown

and in

accordance with

the

manufacturer's recommendations. Pump supplier shall certify that

the

equipment

is

installed

in a

manner

to

ensure proper operation.

3.02 CERTIFICATION

Manufacturer

shall supply certified pump performance curves demonstrating compliance with

the

perfor-

mance specified herein.

3.03 TESTING

After

the

completion

of

installation, each pumping unit shall

be field

tested

to

ensure compliance with

the

performance

requirements

as

specified.

**END

OF

SECTION**

Note:

The

following

is not

part

of

the

original

specification.

It is

offered

as an

example

of

how

competitive

equipment

could

be

evaluated. Strictly

speaking,

the

following provision should

be

located either

in

Parti

of

the

section

or in the

general provisions

of

the

contract.

4.01

EVALUATIONOFBIDS

Evaluation

and

Selection. Each proposal will

be

evaluated

for

selection

by the

Owner based

on the

informa-

tion given

in the

proposal

and

data submitted

in the

brochure.

The

proposed pumping unit will

be

evaluated

on

the

basis

of first

cost

and on

present worth

of

estimated operating cost. Operating costs will

be

determined

by

computing

the

cost

of

power

as

detailed below:

A.

Life

of

pumping unit:

25

years

B.

Interest rate:

8

percent

C.

Power cost:

$0.06/kWh

D.

Annual operation

1.

Design point: 2200 hours

2.

2nd

point:

1300

hours

3.

3rd

point:

900

hours

The

guaranteed wire-to-water

efficiency

at the

design point

and the

wire-to-water

efficiencies

at the 2nd and

3rd

design points stated

in the

brochure will

be

used

to

estimate

the

operating

costs.

[Authors note:

The

stated

energy

rate should

be the

real

cost

per

unit

for

power

and

should,

therefore,

include

the

transformer

losses,

the

power factor

and

time

of

usage penalties,

and the

demand charges averaged over

the

estimated monthly

(or

annual)

energy

consumption.]

Additional factors

affecting

selection will

be

delivery time, operating curve characteristics, NPSH require-

ments,

and

compatibility with existing plant equipment

to

reduce need

for

additional spare parts, availability

of

service,

and

familiarity

of

plant operators with

the

equipment.

The

Purchaser reserves

the right to

select

any

proposal

or

alternative

he

deems

in his

best interest.

The

Bidder shall allow

the

OWNER

or his

representative

to

witness

the

acceptance tests.

[Authors'

note:

The

specifier

must

key

this statement

to the

acceptance test

procedures.]

Appendix

D

Common Blunders

EARLE

C.

SMITH

D-1.

Figure 27-1

Figure

27-1

is a

composite

of

several sewage pumping stations constructed between 1970

and

1980.

The

draw-

ing

represents

a

classic case

of

"file-drawer" engineering.

A

standard design

was

used

in

which

the

motors

are

raised

to

prevent

flood

damage.

But

this pumping station

is on a

hillside

and has a

door

and

windows,

so

motor

flooding

is

not a

problem.

The

blunders

are

real

and

actually were made. They include:

1.

The

design

of the

suction piping

in the wet

well

is the

worst

possible.

The

entrance headloss

is

high,

and the

configuration

tends

to

cause

vortexing.

An

elbow

and a

bell

entrance turned down should

be

added.

2.

The

"pumps

off"

level

is too

low, which causes vortexing

and

cavitation.

3. The

lead pump "on" level

is

below

the

shaft

seal,

which tends

to

draw

air

through

the

stuffing

box and

causes

the

pump

to

"air

bind."

4.

The

inlet allows

the

sewage

to

drop

from

a

great height, which

increases

the

static head, wastes energy,

and

causes

foaming

and

odors

(by

sweeping

out

H

2

S).

Bubbles caused

by the

cascade

may air

bind

the

pump

and,

perhaps,

the

force main.

5. The

check valve

has no

external lever.

The

operator cannot tell whether

it is

open

or

closed.

A

lever

can

indicate clogging

and can

sometimes

be

manually operated

to

dislodge trash.

6. The

check valve

is on a

vertical pipe. Grit

and

rags settling

on it

when

the

pump

is off may

prevent

it

from

opening

fully.

When

the

cover

is

removed

for

cleaning,

the

operator will probably

get a

bath

of filthy

water.

This type

of

installation

is

prohibited

by the

Ten-State Standards

[I].

7. The

gate valve

is on a

vertical pipe.

The

bonnet will

fill

with grit,

and the

valve will eventually

fail.

8.

The

magnetic

flowmeter is in the

wrong location.

A

straight section

of

pipe,

five

diameters

in

length, should

be

placed between

the flowmeter and the

reducer.

The flowmeter

should

be on the

manifold

to

measure

the

flow

from

all the

pumps.

9.

The flowmeter

will probably clog because

the

pump passes

a

3-in. sphere.

10.

There

is no

shut-off

valve

after

(above)

the flowmeter to

allow

its

removal

for

repair.

11.

The

long

shaft

has no

steady bearing

and is too

slender

to be

without

an

intermediate support.

12.

There

is no

lifting

eye, hoist,

or

other

lifting

apparatus

to aid in

dismantling

the

pump.

D-2. Figure 27-2

An

actual pumping station

in the

United States (similar

to

several constructed

in

Saudi Arabia), shown

in

Figure 27-2,

is

so

badly designed

that

the

equipment

had to be

installed before

all the

concrete could

be

cast!

The

blunders include:

1.

The

height

in the

pump room

is

inadequate

for

lifting

the

hollow-shaft motor

off the

pump

shaft.

2.

There

is no

removable hatch

in the

roof

for a

crane

to

lift

the

pump.

3. The

mounting-plate hole

is not

large enough

to

allow

the

removal

of the

pump.

4. The

pumps

are

mounted

in

line with

the

inflow—a

poor arrangement. (Exceptions

are

given

in

Sections

12-

6 and

12-7

and

Chapter 17.)

5. The

suction bells

are too

close together

[2].

6. The

150-mm

(6-in.) clearance between

the

suction bell

and the floor is too

small

[3] as

indicated

by the

then-prevailing Hydraulic Institute Standards

[2,

3].

7. The

"off"

level

is too

low, which causes

vortexing.

8.

There

is no

ladder

or

steps

for

access

to the

sump.

9.

There

is no

hatch

for

access

to the

sump.

10. The

generator

is too

small

to

start even

one

pump.

D-3.

References

1.

Ten-State Standards. Recommended Standards

for

Sewage

Works,

Great

Lakes-Upper

Mississippi River Board

of

State

Sanitary Engineers. Health Education Service, Inc., Albany,

NY

(updated periodically).

2.

Hydraulic Institute Standards

for

Centrifugal,

Rotary

&

Reciprocating Pumps, 13th

ed.

Hydraulic Institute, Parsippany,

NJ

(1974).

3.

Hydraulic Institute Standards

for

Centrifugal,

Rotary

&

Reciprocating Pumps, 14th

ed.

Hydraulic

Institute,

Parsippany,

NJ

(1983).

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

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