sealing options

7/27/2019 Sealing Options

1/5

Sealing Options

Though often overlooked, shaft sealing selection can be just as critical as

pump selection. Shaft seals can take many different forms, but all serve the

common purpose of keeping the liquid in the pump. Here are the most

commonly used shaft seal options for pumps. For additional information

please see theLiquid Containmentpaper in theApplicationssection.

Shaft Seal Description Advantages Disadvantages

Braided

or

formed

rings that

are

compress

ed in the

stuffing

box of

the

pump. A

s the

packing

is

tightene

d, itcompress

es

against

the shaft

and

stuffing

box bore

to create

the seal.

Economical

Excellentfor

sealing

thick,

difficult

to seal

liquids

such as

chocolate

,

molasses,

asphalt,

resins,

tar, and

some

adhesives Seldom

catastrop

hically

fails

Poorseal for

thin

liquids,

especia

lly at

higher

pressur

es Require

s

lubricat

ion

either

externa

lly or

by theliquid

being

pumpe

d; this

means

packin

g must

be

allowe

d to
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2/5

leak

slightly

(weep) Can

damage the

pump

shaft if

adjuste

d too

tightly

A circular

elastome

ric seal

elementin a rigid

outer

housing

Economical

Come ina wide

variety

including

cartridge

triple lipseals for

higher

viscosity

liquids

Typicallylimited

to

lower

pressur

es Poor

for

thin,

non-

lubricating

liquids

or for

abrasiv

es Can

catastr

ophical

ly fail


3/5

Simplifie

d,

mechanic

al seals

usehighly

polished

faces

(one

stationar

y and one

rotating)

running

against

eachother* to

form a

seal.*actually,

seal faces

only touch

when at

rest. While

turning,

they are

separated

by a thin

film of the

liquid being

pumped,

barrier

fluid, or gas

Mechanical seals

come in a

wide

variety of

designs

and

materials

for nearly

every

application.

Offerdesigns

which

can be

easily

replaced

or

repaired

Like lipseals,

cancatastr

ophical

ly fail Higher

end

double

cartrid

ge

seals

and gasbarrier

seals

are

quite

expensi

ve and

require

externa

l

support

equipm

ent.


4/5

A Mag

Drive

pump is a

sealless

pump

that

utilizes a

magneticcoupling

to create

a static

shaft

seal. Driv

e

magnets

(outer)

align

with

driven

magnets

(inner)

and use

magnetic

force to

turn the

shaft

through a

static

containm

ent shell

(canister)

.

MagDrive

pumps

are a

truly

sealless

design

which

ensures

zero

leakage

of liquidor

emission

s, making

them

ideal for

hazardou

s, toxic,

corrosive,

flammabl

e, orexpensiv

e liquids. Extremel

y reliable

for

maximu

m

insurance

against

sealleakage

and

maximu

m seal

life

Moreexpensi

ve than

most

shaftseal

options

, but

this

must

also be

weighe

d

against

theadded

costs of

seal

replace

ment,

includi

ng

labor

and

cleanup. Typicall

y

limited

to

about

500F

/

260C

maximum

(heat

can

perma

nently

damag

e the

magne

ts) Based
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5/5

on the

cost

and

risk of

damage due

to

heat,

monito

ring

devices

are

typicall

y

recommende

d to

protect

these

pumps

from

damag

e.

sealing options

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