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

H-6. Chlorination

178.

See

that

the

gaskets

on the

doors

of the

chlorination room

fit

tightly.

179.

See

that

air

packs

are

furnished

and are

operational.

180.

Verify

the

proper operation

of the gas

alarm system.

The

manufacturer's representative should perform

the

necessary checks

and

tests

for the

chlorinator

equip-

ment

and

installation.

These

systems

are

critical, complex,

and

require more detail than

the

abridgement listed

in

Items

181

through 186.

181. Check

the

chlorinator equipment

and

installation with respect

to

•

O-rings

•

Inlet

gas

heater

•

Venting

• Gas

inlet

filter

• All

lines

and

valves

•

Flowmeter

•

Leaks

in

chlorine lines, valves,

and fittings

from

chlorine tanks

to

chlorinator

•

Clean chlorine pressure reducing valve (PRV) cartridge

•

Clean

and

operational vacuum relief valve

•

Clean

and

operational trimmer drain relief valve.

182. Check

the

chlorine evaporator

with

respect

to

•

Proper operation

of

temperature

and

pressure gauges

•

Leaks

•

Clean chlorine

PRV filter

•

Clean chlorine chamber.

A

dirty

or

oily

one is

very dangerous.

•

Clean liquid line

from

tank car.

A

dirty

or

oily

one is

very dangerous.

183. Proper operation

of

ejectors.

184. Check

the

chlorine solution pump

with

respect

to

•

Items

34

through

38

•

Lubricated pump

and

motor bearings.

185. Proper size, type, material,

and

installation

of all

valves.

186. Check

the

chlorine tank connections

with

respect

to

•

Proper size, type, material,

and

installation

of

hose lines

•

Leaks

in

hose lines

•

Leaks

in

pipe nipples

and

valve installed

on the

chlorine tank.

H-7. Complex Drives

Engines,

engine-generator sets, variable-speed drives,

and

controls MUST

be

checked

and

tested

by a

factory

representative.

H-8. Control Panel

and

Electrical

Systems

These tasks should

be

performed

by an

electrical

inspector

or

engineer

and the

electrical contractor foreman.

Supplement

Items

187

through

196

with

"Field

Tests"

in

Section

9-12.

187. There

is

proper voltage

on

each

leg

into

the

panel.

188.

The

voltage

on the

control side

of the

panel

is

proper.

189.

The

pump sequencer

is

operational.

190. Overload protectors

are

properly sized.

191.

All

alarms

are

operational.

192.

All

limit switches

and

pressure switches

are

installed

and

operating.

193.

The

telephone dialer

is

operational.

194.

All

nuts, screws,

and

instrument

and

junction

box

inspection covers

are

tight.

195. Make certain that

all

GFCI outlets have been tested.

196.

Set all

STOP/LOCKOUT

buttons

on the

equipment

to the

STOP

position.

Automatic

Controls,

Devices,

and

Monitors

197.

If

practical, measure

the wet

well

(do not

trust

the

plans)

to

determine volume used

for in

situ

testing

of the flow-

meter,

if

furnished

(see Item 204). Make sure

the flowmeter is

installed properly

and the

recording mechanism

is

operating. Following

the

main pump start-up (Items

321

through 336), check

the

accuracy

of the

flowmeter

volu-

metrically.

If

volumetric calibration

is

impractical

or if

greater accuracy

is

needed,

use

tracers (see Section 3-9).

198.

Any

other devices

not

mentioned above should also

be

tested

for

proper operation.

H-9. Bubbler

Systems

199. Construction debris

and all

foreign materials

are

removed

from

liquid channels

and wet

wells.

200. Check

wet

well

and

channel bubbler pipe

for

extension.

The

bubbler stilling well

is

constructed

in

accor-

dance with

the

contract plans.

201.

All

indicating devices

on the

bubbler panel

are

furnished

and

adjusted properly.

202.

All

connections

from

the

bubbler panel

are

properly made

to the MCC

and/or control panel.

203. Operate

the

compressed

air

system.

Adjust

the

airflow

to the wet

well.

204.

If

practical, admit known amounts

of

liquid

to the

main pumping station well

to

calibrate

it

volumetrically.

Otherwise, measure

the wet

well accurately

and

calculate

the

volume

at HWL and LWL

(for calibration

check

of the flowmeter).

205. Make bubbler system calibration adjustments

as

necessary.

206. Allow channel

and wet

well levels

to

rise. Check level indication

at the

liquid level control

and

verify

accuracy

by

comparing

to

liquid level

as

measured with

the

calibrated rod.

207. Allow

the

liquid

to

rise

to the

maximum level.

If the

bubbler system calibration requires readjustment,

reverify

the

entire range

of

bubbler system calibration.

Refer

to the

specifications

for

proper level setting.

H-10.

Vacuum Priming

Systems

There

are

three types

of

vacuum priming systems.

The first is a

simple eductor type used with water

or air to

remove

the air

from

the

main pump casing

and to

draw liquid

from

the wet

well.

The

second type

is a dry

vacuum pump with

a

protective tank installed between

the

vacuum pump

and the

main

pump.

The

tank

is

equipped with

an

electrode. Before starting this system, water must

be

emptied

from

the

protective tank. When

the

vacuum pump

is

energized,

a

vacuum

is

created

in the

tank,

so air and

then liq-

uid

is

drawn

from

the

main pump casing. When

the

protective tank

fills

with liquid

from

the

main pump cas-

ing

to the low

level

of the

electrode,

the

vacuum pump

is

automatically deenergized

and the

main pump

is

primed.

The

third type

is a

package system that basically consists

of one or two

water-displacement, wet-type

vacuum

pumps, vacuum tank, vacuum valve, vacuum relief valve, water level switches,

and

pressure

switches

and

gauges.

The

"wet-type pump"

is

dependent

on a

continuous supply

of

cool, clean

"service

water," which enters

the

vacuum pump

on the

suction

side,

is

discharged with

the

compressed gas,

and

thus

draws

air and

water

from

the

vacuum tank, main pump casing,

and wet

well.

The

device then shuts down

automatically.

Eductor

Type

Systems

208. Main pump casing nozzle should have

shut-off

valve

and a

quick-disconnect

fitting

installed.

209.

The

quick-disconnect

fitting on the

water

or air

priming hose must match casing nozzle disconnect.

210. Priming hose must

be

pressure rated

for the

water

or air

used

and

must

be in

good condition.

211. Priming hose must have

a

manual

shut-off

valve

and

sufficient

pressure

to

evacuate

the

pump casing

air

and

draw liquid

from

the wet

well.

Dry

Vacuum

Pump

Systems

212. Separate

the

pump coupling.

213. Energize

the

control

and

local START button

to

bump

the

motor. Compare

the

motor rotation with

the

arrow

on the

vacuum pump.

214. Deenergize

the

system.

215. Check vacuum pump lubrication.

216. Manually turn

the

vacuum pump

in the

direction shown

by the

rotational arrow.

217. Check

motor-vacuum

pump alignment.

218. Reconnect

the

vacuum pump coupling.

219. Replace

the

coupling guard.

220. Inspect piping between vacuum pump

and

protective tank. Piping should

be

installed near

or at the top of

the

protective tank.

221. Inspect piping between protective tank

and

main pump.

222. Inspect

the

electrical connection

to the

transformer required

for the

electrode

installed

in the

protective

tank.

The

electrode system operates

on low

voltage.

223.

The

protective tank must have

a

drain with

a

shut-off

valve.

If the

system

is

specified

as an

automatic drain

type,

a

normally closed solenoid must

be

furnished

on the

drain piping

and

must

be

electrically connected.

The

solenoid opens when

the

motor

is

deenergized, which drains

the

vacuum tank.

224. Inspect

the

protective tank liquid sight glass

and

determine whether

its

elevation corresponds with

the

bot-

tom

of the

electrode.

225. Open

all

vacuum pump suction

and

discharge valves.

226. Fill

the

protective tank with water

so

that

the

bottom

of the

electrode

is

submerged.

227. Energize

the

vacuum pump.

The

unit should

not

operate.

If it

does, immediately deenergize

the

vacuum

pump

and

correct

the

wiring.

228.

After

all

corrections

and

trial runs

are

completed, open

the

main pump suction

shut-off

valve.

229.

Do not

open

any

pump discharge valves.

230. Energize

the

vacuum pump system,

and

check

the

vacuum gauge reading.

If the

gauge reading

is

above

635 mm (25

in.)

of

mercury

and the

pump

is a

rotary vane type, immediately shut down

the

system

and see

whether

all

required valves

are

open. Note: Above

686 mm (27

in.) this type

of

unit will destroy itself,

and

high

vacuum

is

very dangerous

to the

piping

and the

protective tank.

Wet-Type

Vacuum

Systems

231. Separate

the

pump coupling.

232. Energize

the

control

and

local START button

to

bump

the

motor. Compare motor rotation with

the

arrow

on

vacuum pump.

233. Fill

the

pump with water

up to the

shaft

level. Never start

the

motor with liquid level above this

shaft

line

because

of the

high power consumption.

234. Rotate

the

pump

shaft

by

hand

and

check

for

binding.

If the

pump does seize, gently

tap the

shaft

end to

free

the

impeller.

If the

trouble

persists,

fill the

pump with

a

solvent approved

by the

manufacturer

to

loosen scale binding

and

rotate

the

pump

shaft

by

hand.

235. Check alignment

of the

shaft.

236.

The

equipment must

be

level

because

of the

water-filled pump.

237. Packing-equipped pump glands must

be finger

tight only.

Adjust

after

the

unit

is

operating

as

specified.

238.

Reassemble

the

coupling

and

guard.

239. Check motor

and

vacuum pump lubrication.

240.

All

gauges

and

switches should

be

made operational.

Adjust

switches

and

valves

as

specified.

241. Determine that

the

piping

is

connected properly.

242. Disconnect

the

piping

to the

main pump, energize

the

system,

and

operate

for

several hours. Make adjust-

ments

to find the

optimum operating conditions.

•

Packing gland drip

and

temperature.

•

Motor amperes

are

below motor

nameplate

rating.

•

Pump temperature

is

acceptable.

•

Amperes used versus motor nameplate amperes rating.

243. Deenergize

the

system.

244. Reconnect

the

piping

to the

main pumps.

245. Reenergize

the

system. Again inspect

the

packing, amperage, motor temperature, vacuum gauge reading,

and

pump temperature.

The

pump must

be

able

to

reach

the

design vacuum

in the

time specified without

a

motor overload.

246.

If the

pump cannot reach design vacuum,

it may be

necessary

to

increase

the

water

flow

into

the

pump

slightly.

Check motor amperage during

the

time this

is

done.

H-11.

Compressed

Air

Systems

Compressed

air may be

used

for

air-operated check valves, air-to-oil cylinder check valves,

and

bubbler sys-

tems.

The air

lines must

be

furnished

with

shut-off

valves, pressure relief valves,

and

pressure-reducing valves

as

specified

and

required. Then

follow

the

procedure below:

247. Separate

the

driven equipment coupling.

248. Check alignment, grouting,

and

doweling

of

components.

249.

See

that

all

piping

is

properly supported

and

under

no

strain.

250. Rotate

the

compressor

shaft

several times

by

hand

to

check

for

rubbing

or

binding.

If an

automatic belt-

operated lubrication system

is

furnished,

push each lubricator site feed plunger

a

number

of

times

and

rotate

the

shaft

one-quarter turn. Repeat this procedure until

the

shaft

has

been turned

a

full

360°.

251. Energize

the

motor

and

check

the

direction

of

rotation against

the

rotational arrow.

252. Reconnect

the

coupling.

253. Fill

the oil

bath open-type intake

air filter

with

oil to the

level indicated with

a

lubricant recommended

by

the

manufacturer.

If a

dry-type

air filter is

used, clean

the

medium.

254. Check

the

compressor

and

motor

for

lubrication.

255.

Set

pressure switches

on the air

receiver

as

specified

for the

lead compressor,

the lag

compressor,

and the

alarm.

256.

If the

compressor

is a

water-cooled unit, open

the

bypass line around

the

automatic water solenoid valve

and

water temperature

flow

regulator. Turn

on the

cooling water supply

and fill the

jacket

and

cooler com-

pletely. Bleed

the

system

of air and

close

the

bypass line.

257. Open

all

drain valves

in the air and gas

piping

to

remove

any

liquid. Close

the

drain valves.

258. Check

the

operation

of all

manual valves.

Adjust

packing glands

(if

furnished)

as

necessary. Close

the

bypass

valve

at the air

dryer.

259. Start

the

compressor

in

automatic mode.

260. Check

and

adjust

pressure-regulating valves

as

specified

for

regulators

to the

wet-bulb bubbler system,

regulators

to

HVAC

equipment, air-operated cylinder check valves,

and

air-to-oil cylinder check valves

as

specified.

261. Check

the

pressure

on the

compressor loader.

262. Check

air

receiver pressure gauges, condensate site glasses, drain valve,

and

automatic moisture eliminator.

263. Check operation

of the air

dryer, cooling

dry filters,

automatic condensate discharge valve,

and the

com-

pound

gauge indicating pressure

and

temperature

of

refrigerant.

264. Check

all air

lines

for

moisture

and

drain them.

265. Turn

the

compressor control

to

OFF, then decrease

the

system pressure

to

less than design conditions

and

note

annunciator alarm.

266. Return

the

compressor

to

automatic operation. Observe

the

automatic starts

and

shutoffs

of the

compres-

sor at

design pressures.

267.

Check

and

adjust

the

temperature

switches.

The

switches

should

be set at

approximately

6 to

8

0

C

(10 to

15

0

F)

above expected normal operating temperatures.

268. Observe

the

discharge

air

temperature.

It

should

be

approximately equal

to the

expected

discharge temper-

ature

for the

operating pressure

as

shown

on the

manufacturer's data sheet.

269. Observe

the

water outlet temperature

and

wait

for it to

stop rising before making

corrections.

270.

Adjust

water

flow

through

the

aftercooler

(if

installed)

to

maintain approximately

38

0

C

(10O

0

F)

outlet

air

temperature.

271. Reduce

the

pressure

and

note

the

lead

compressor's

automatic start.

272. Reduce

the

pressure

and

note

the lag

compressor's start.

273. Check operation

of the

duty transfer switch.

274.

After

a

unit

has

been operating

for

approximately

2 h,

slowly lower

the

setting

of

each temperature switch

until

the

switch opens

to

shut down

the

driver. Readjust

the

switch

to 6 to

8

0

C

(10 to

15

0

F)

above this shut-

down

point

and

restart

the

unit. Repeat

this

procedure with

each

temperature switch.

275.

After

all the

checks have been made

and the

equipment

is

operating smoothly,

the

unit

is

ready

for

service

in

the

system.

H-12.

Hydropneumatic

Tank

Systems

The

optimum

water-air

ratio

for any

size tank

and

operation condition

can be

found

by

applying Boyle's law,

which

is

expressed mathematically

as

P

1

V

1

=P

2

V

2

(H-I)

where

P is

pressure

and V is

volume.

The

design engineer

has

selected

the

hydropneumatic tank

for a

specific

pressure-level relationship. Obtain

the

information

and be

sure

it is

understood before beginning

a

check

of the

system.

Follow

the

procedure below:

276. Check

the

water receiving tank

and

clean

it.

Flush

the

incoming water lines. Check

the

backflow

preventer.

277. Fill

the

water receiving tank. Check

the

drain,

overflow,

and float-operated fill

valve.

Adjust

as

necessary.

278. Check

the flow-through

chemical feeder

(if

installed)

for

seal-water

treatment.

279. Check

the

duplex strainer,

seal-water

pumps, hydropneumatic tank,

and

main pump

seal-water

piping

and

valves.

280. Check

the

hydropneumatic tank. Flush

the

tank

and

piping with water.

281. Check seal-water pump

and

motor bearing lubrication. Check pump packing.

282. Disengage

the

pump coupling.

283. Energize

the

motor

and

compare

the

direction

of

rotation with rotational arrow

on the

pump.

284. Turn

the

pump

by

hand

in the

direction

of the

arrow

and

check

for

binding.

285. Reconnect

the

pump coupling.

286. Fill

the

hydropneumatic tank

to

specified

maximum water level.

287. Check

the

hydropneumatic tank relief valve against specification (usually factory-set

to

tank pressure

rating).

288. Inspect check valve

and

hydropneumatic tank

air

lines

for

proper

functioning.

Open

air

valve

and

raise

tank

air

pressure

to

maximum operational pressure. Close

air

valve.

289.

Set

pressure switches

as

specified

(by

draining tank)

to:

• Set

automatic-start seal-water pumps

•

Stop seal-water pumps under manual control

• Set

seal-water pressure alarm.

290. Operate seal-water pumps manually

to

check operation.

Refill

the

tank.

291. Override

the

seal pump

and

manual control pressure interlock

by

holding

the

pump start pushbutton. Note

water elevation, operating pressure,

and

annunciator high water alarm.

292. Drain

the

tank

and

note

the

high-water-alarm

clearing level.

293. Place

the

seal-water pump

in

automatic mode. Continue

to

drain

the

tank until

the

lead pump starts. Allow

the

lead pump

to

refill

the

tank. Note pressure

and

level

at

shut-off.

294. Repeat

the

automatic test with

the

second pump

in the

lead position.

295. Repeat

the

automatic test

and

simulate lead pump failure-to-start. Note standby substitution

for

lead pump

and

annunciator alarm. Return

to

normal.

296. Repeat failure-to-start test with

the

second pump

in the

lead

position.

Note annunciator alarm. Return

to

normal.

297. Check

the

tank air-add system

for

panel

function.

298.

Adjust

the

seal-water regulator

to the

main pump

to

regulate

the

pressure

as

required.

299.

See

that

all

manual valves

to

main pumps

and

auxiliary equipment

are

open.

300. Check main pump packing,

seal-water

solenoid,

sight

flow

indicator, control circuit timer,

and

auxiliary equip-

ment

as

part

of the

main pump test sequence.

Main

pump packing

gland

bolts

should

be

only

finger

tight.

H-13.

Main

Pumps, Final Pre-Start-Up Checks

The

procedure depends

to

some

degree

on

whether

the

pumps

are

constant speed (C/S)

or

variable speed

(V/S).

Variable-speed equipment should

be

checked only

by the

manufacturer's representative. Pumps

furnished

with

wearing rings should never

be

operated dry. Read

the

manufacturer's instructions

for the

type

of

lubricants

and

for

cooling

(if

required)

and

make sure

the

bearings

are

lubricated properly. Follow

the

procedure below:

301. Energize

the

seal-water system

and be

sure that water

is flowing to the

stuffing

box or

seal box.

302.

Stuffing

box

gland

for

packing

is

only

finger

tight.

303. Air, oil, air-oil,

or

water

is flowing to the

check valve cylinder.

304. Manual check valve weight

or

spring

is

adjusted,

and fine

tune

after

operation.

305. Remove

the

coupling guard, separate

the

pump coupling

half,

and

check

the

alignment between

the

pump

and

the

driver.

306. Check motor

and

pump lubrication.

307. Energize

the

master control panel.

308. Energize

the

local control button

and

equipment

and

bump

the

motor

to

determine pump rotation relative

to the

pump arrow

and

pump nozzle.

309.

If

pump rotation

is

incorrect, lock

out the

pump

at the

local control, deenergize

the

pump control,

and

correct.

310. Reenergize

the

pump control

and

push START button

to

bump

the

motor

and

recheck rotation.

311. Rotate

the

pump

shaft

manually.

312. Reassemble

the

pump coupling

and

replace

the

coupling guard.

313. Shut

off

the

suction

and

discharge pressure gauges.

314. Repeat Items

302

through

313

for

each main pump.

H-14.

Wet

Well

and

Testing

of

Main

Pumps

315.

Refer

to

bubbler system start-up.

316. Check controls

for

START/STOP levels. Readjust

as

required.

317. Electrically jumper

out

(bypass)

the

actuator

for the

discharge control valve

to

determine whether

the

valve

is

open

and

note opening

and

closing times. Readjust speed controls

as

required.

318. Close

all

pressure gauges

to the

liquid being pumped.

319. Energize

the

seal-water system

and

determine that

the

water

is flowing to the

stuffing

or

seal box.

320. Energize

the

pump control.

321. Energize

the

START button

of

local control. (Note that

the

pumps

are

noisy

at

this

shut-off

condition.)

322. Open

the

manually operated discharge valve slowly,

and fill the

discharge header

and the

force main

or

transmission pipeline slowly. Check

for

undue motor

and

pump noise

and

vibration.

323. Open

shut-off

valves

for

discharge

and

suction pressure gauges; bleed

all air

from

the

pressure gauge pip-

ing

or

tubing;

and

compare head

at

shut-off

and flow,

head,

and

power

at

operating conditions with

the

pump

performance curve.

324.

If the

pumping station

has no flowmeter, flow can be

measured

by the

methods described

in

Section 3-9.

325.

If the

stuffing

box is

leaking excessively, tighten

the

gland slowly.

Be

sure that

a

small, steady stream

is

leaking

from

the

packing during

a

24-h

break-in

period.

326. Close

the

discharge

shut-off

valve slowly enough

to

avoid water hammer.

327. Deenergize

the

pump.

328. Remove

the

jumper

from

cylinder solenoid check valve.

The

valve should

close.

329. Determine that check valve limit switches

are

operating properly.

330.

Set the

check valve

differential

pressure switch

as

required.

331. Open

the

discharge

shut-off

valve.

332. Energize

the

pump

and

note

the

time

of

check valve opening. Readjust

if

required.

333. Deenergize

the

pump

and

close

suction

and

discharge

shut-off

valves. Close

all

valves

to

pressure switches.

334. Repeat Items

317

through

333

for

each pump.

335.

After

each pump

has

been tested individually, open

all the

suction

and

discharge valves

and

operate

the

station

as

specified.

336.

In a V/S

pumping station with

wet

well levels

set at the

normal level

of flow in the

incoming sewer pipe

(see Figure

12-35),

adjust

the

acceleration

of the

pump speed control (usually

by

reducing

it) so

that surg-

ing

of flow in the

influent

sewer does

not

occur.

H-15.

Cleaning

Wet

Wells

The

operational

and

timed sequence used

for

ejecting scum

and

settled solids

in wet

wells

for

solids-bearing

waters must

be

established. Either clear

or

dirty water

can be

used.

Hopper-Bottom

Sumps

337.

Set the

pump control

to

MANUAL

(or

lock

out the low

level

STOP

switch)

and

pump

the

water level

down

as far as it can go

with either

one or

both pumps operating. Look

for a

number

4 or 5

surface vortex

that

would

(or

does) draw

floating

material into

the

pump(s).

The

vortex should persist

for 5 or 6

sec-

onds—long

enough

to

engulf most

of the

scum.

In a

properly designed sump,

the

hopper bottom concen-

trates sludge

so

near

to the

pump intake that sludge should

be

ejected

in

every pump cycle.

338. Test

the

wash water hose

to see

that

flowrate and

pressure

are

sufficient

to

scour grease

off

the

walls

of the

sump.

Trench-Type

Sumps

Depending

on the

circumstances,

it may

take several trials

to

reach

a

satisfactory operating sequence

of

storage,

sluice

gate setting,

and

pump operation. Three scenarios

are

possible:

(1)

inflow

rate,

Q, is

greater than

the

capacity,

Q

p

,

of the

last pump;

(2) Q

equals

or is

somewhat less than

Q

p

;

and (3) Q is

much less than

Q

p

.

There

is

no

need

to

test

the first two

scenarios,

and the

sluice gate

is not

needed.

The

operator simply runs

the

last

two

pumps

at

full

speed

for a

short time

(a

minute

or

two)

after

the

hydraulic jump reaches

the toe of the

ogee ramp.

The

third

scenario requires:

(1)

water storage

sufficient

to

complete

the

cleaning cycle

and (2) the

release

of the

stored water under

the

sluice gate

at a

rate

of

about

50% to 80% of the

capacity

of the

last pump.

339. Obtain

from

the

designer

the

sluice gate setting required

to

release

an

adequate

flow and

operate

the

sluice

gate

to

obtain that setting before testing with water.

Adjust

the

automatic stop

(if

there

is

one)

at

that set-

ting.

If no

stop

is

installed, close

the

sluice gate, then open

it for as

many seconds

as are

required

to

reach

the

proper setting.

340. Obtain

from

the

designer

the

time required

to

store

a

sufficient

volume

of

water

for

various

influent

flow-

rates. Water

can be

stored

by

closing

the

sluice gate

or by

shutting

off the

pumps.

In

either way,

the

pumps

must

be

stopped

for

awhile, because

a

trench-type

wet

well

can

usually

be

dewatered

in

about half

a

minute,

whereas storage (depending

on

influent

flowrate)

takes much longer.

341.

For a

range

of

influent

flowrates, the

designer must calculate

the

sequential times

to

activate

the

sluice

gate, shut

off the

pumps,

and

start

the

pumps again (see Examples 12-4

and

12-5).

342. Test items

339 to 341

with

either clear

or

dirty water.

Adjust

sequential times

and

sluice gate settings

so

that

the

hydraulic jump travels

from

the toe of the

ogee ramp

to the

last pump

in a

reasonable length

of

time

(15

to 40

seconds). Correct calculated values

by

observations

as

necessary

and

supply operators with

instructions

and

timing sequences

for the

various

influent

flowrates to be

expected.

343.

If

there

is

one, adjust

the

power monitor

in the MCC (or the

limit switch

on the

check valve lever)

to

stop

each pump

as it

loses

suction near

the end of the

cleaning cycle.

344. Test

the

wash water hose

to see

that

flowrate and

pressure

are

sufficient

to

scour grease

off the

walls

of the

sump.

345.

If the

station

does

not

have

a flowmeter,

supply operators with charts

or

tables relating

flowrate to

speed

(for

V/S

pumps)

or to

time between pump start

and

stop (for

C/S

pumps).

H-16.

References

1.

Hydraulic

Institute Standards

for

Centrifugal,

Rotary

&

Reciprocating Pumps, 14th

ed.

Hydraulic Institute, Cleveland,

OH

(1983).

(See also later editions.)

2.

Pumping Manual,

6th ed.

Trade

&

Technical Press, Ltd, Morden, Surrey, England

(1979).

3.

Karrasik,

E.

J.,

W. C.

Krutzsch,

W. H.

Eraser,

and J. P.

Messina. Pump Handbook,

2nd ed.

McGraw-Hill,

New

York

(1986).

Appendix

I

Addenda

GARR

M.

JONES

CONTRIBUTORS

Roberts.

Benfell

Arnold

R.

Sdano

1-1.

Fire

Safety

in

Pumping Stations

Several codes (NFPA

820,

NFPA

70,

NFPA

101,

to

name

a

few) provide guidance

for fire

protection

for

instal-

lations such

as

pumping stations.

In

addition

to

these

documents,

the

designer should

consider

the

following:

Choice

of

Materials

• Be

careful

in the

choice

of

materials that could

add to the

fuel

load

(the

amount

of

burnable material present)

in a

structure.

Plastic, although

useful

for

corrosion protection

and

resistance, will

burn

if

ignition occurs.

The

products

of

combustion

from

plastics

are

often

toxic

and

corrosive

and

become more

so

when they contain

fire

retardants.

• Be

suspicious

of

materials that could auto combust, such

as

some forms

of

activated carbon.

If

these materials

are

used, make certain that they

are

isolated

from

other combustible materials.

Fire

Suppression

Systems

•

Storage areas, such

as

those

for

records, lubricants,

and

fuels,

should

be

separated

from

other areas

of the

structure

by

two-hour rated

fire

walls

and

should

be

served

by

independent ventilation systems. Appropriate

fire

suppression systems should

be

considered

for

these areas.

•

Cable trays

and

other locations where electrical conductors

are not

protected

by

conduit should

be

monitored

by

rate

of

temperature rise, particle

ion,

and

smoke detection systems.

• In

large installations, consider dividing

the

electrical systems into identical halves

and

placing

the

switchgear

in

separate

fire-rated

rooms

to

avoid

the

prospect

that

an

electrical

fire

will disable

the

entire facility.

• In

critical

facilities,

install sprinklers over cable trays.

1-2.

Application-Engineered Equipment

Consider

specifying

application-engineered equipment

for

those facilities considered

to be

critical

to the

overall

function

of the

installation. Included

in

this category

are the

main pumps

and

motors, engine-generators,

and

engine drives

for

pumps.

The

hallmark

of

application-engineered equipment

is the

design

of

machines

for the

specific

installation

and

application. Generally,

a

greater level

of

conservatism

is

employed

to

provide equip-

ment

more robust

(and

therefore more reliable with longer

life)

than that obtainable

from

standard machines.

The

following

are

suggestions

for

improving

the

performance

of

typical machines.

Pumps

• A

maximum permissible pump

shaft

deflection

of

0.05

mm

(0.002

in.)

at the

pump seal

is

suggested

for any

operating

condition

specified.

Pumps

can

usually

be

modified

to

accept larger bearings

and

shafts.

•

Specify bearings with

L-IO

ratings

of

100,000

hours

for any

loads imposed

by any

specified operating condi-

tion. Some engineers insist that

life

is

actually increased

by

specifying

an

L-IO

rating

of

50,000

hours

because

of the

reduced tendency

for

skidding

in the

more heavily loaded bearing. Others maintain that skid-

ding

is not a

problem

(or at

least unlikely)

in

bearings turning

at

1725

rev/min

or

less.

•

Specify

either austenitic cast iron (ASTM A439)

or

that nickel

be

included

in

iron castings (2-3%

is

sug-

gested)

for

improved resistance

to

corrosion

and

erosion.

Alternatively, consider applying ceramic coatings

such

as

Thortex

Cerami-Tech

[1]

to

internal pump surfaces

to

reduce wear

and

erosion (see page 758).

•

Specify cast stainless steel

or

aluminum bronze

for

impellers where

NPSH

A

margins

are

borderline

to

reduce

erosion

due to

cavitation.

The

more

flexible

ceramic coatings (such

as

Thortex

Cerami-Flex

[I])

on

ordinary

impellers

might also serve

at

less cost.

•

Require

the

pump rotor unbalance

to be no

greater than grade G2.5

per ISO

Standard

1940/1.

•

Require

the

pump

and

driver supplier

to

perform

a

torsional analysis

for

systems with engine drivers

of

250 kW

(335

hp) or

larger

or for

synchronous motors

of 500 kW

(670

hp) or

larger.

Motors

•

Specify

NEMA Class

H

insulation,

but

require

the

motor

be

designed

for a

Class

B

temperature rise. Note, how-

ever, that

the

thicker insulation requires wider slots

and

thereby

reduces

the

amount

of

iron

and the

efficiency.

•

Require

a

1.15

service factor over nameplate rating,

but

prohibit

the use of the

service factor

for

driving

the

machine

at any

specified operating condition.

•

Specify inverter

duty

motors

for all

variable speed applications.

•

Specify

IEEE

efficiency

compliant motors

for

cooler

operation.

•

Consult

the

vendor

for

derating motors

at

altitudes above 1000

m

(3000

ft).

Engines

•

Derate engines

to

allow

no

more than

85% of the

manufacturers

continuous duty rating.

• Pay

attention

to

elevation

and

temperature conditions

to

make certain engines

are

selected

properly.

•

Insist upon

a

thorough mass elastic system analysis.

• Do not

allow controls

to be

mounted

on the

engine.

Generators

•

Specify

the

same construction

as

detailed above

for

motors.

•

Require solid state

field-forcing

regulators.

•

Specify generator loading criteria specific

to the

application—that

is, if the

generator

is to

start

75 kW

(100

hp)

motors

in

sequence,

so

state. Require

the

manufacturer

to

produce

a

voltage transient study

to

dem-

onstrate that

the

generator

and

engine have been selected

for the

actual starting duty.

1-3.

Air-Vacuum Valves

for

Wastewater Service

Historically,

air

release

and

vacuum relief valves

for

wastewater service have been expensive

to

maintain

and

are

prone

to

jamming either open

or

closed

due to

grease

and

debris.

In

side-by-side tests

in a

system known

for

considerable

difficulty

with

traditional

air-vacuum

valves,

a new

design, Vent-O-Mat®

series

RGX

[2],

was

found

to be

much more reliable

and

easier

to

maintain.

After

testing,

a

large number

of

these valves were pur-

chased

for

installation

in the

system tested. Note that

the

period between cleanings

of

conventional

air-vacuum

valves

is

typically

one to

three months whereas

the

permissible period between cleanings

of the RGX

valve

is

said

to be at

least

six

times longer.

A

somewhat

different

style, Series RBX,

is

intended

for

water service.

Prod-

uct

information comes

with

software

to

help

the

engineer select

the

proper size valve

for a

specific application.

1-4.

Machine

Foundations

and

Installation

Experience

has

shown

that

commonly accepted practices

for

preparation

of

machine foundations

and for

machine

alignment have

not

been adequate

in

many instances. Lack

of

adequate

care

in

preparation

of the

foun-

dation

has

resulted

in

poor support

of the

equipment, progressive misalignment

of the

machines,

and

high main-

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

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