Non-contact gas seal for rotary equipment

Non-contact gas seal for rotary equipment

switched

off and the seal gas supply

opening

force and the closing

balance.

Hence,

is great,

the

against

the rotary

This

design

non-contact

pressure non-contact

Patent

number:

2000

T. Fuse

Assignee:

Nippon

Pillar

In this invention contact

a static

equipment

such

pressure-type

dust-mixed

machine

for

longer

by dynamic

has formed

endfaces.

the

But

machine

this

leakage

machine,

so

equipment While dynamic

has

pressure, rotary

set higher

than

pressure

conditions,

under

low pressure

equilibrium.

out.

Sealing Technology No. 86

In the

in such

non-contact

in Figure

1 is formed

(2)

on

fixed

a rotary

gas seal

so that a rotary shaft

and

a

in a non-contact in between

state with

a fluid

by static pressure.

This

side of a ring-shaped

region between

two seal rings from the non-sealed circumferential fluid

region

region

the

(A) ar

side. In this example, is a high-pressure

gas

and

The

O-rings

portion

cylinder

of the stationary

portion

from rotating permitting within

via the third

in relation the

Multiple in the

pins planted

stationary

are inserted

seal ring

to the seal casing, while

stationary

seal ring

to move

range in the axial direction.

static

form

pressure

of a circle seal

endface

stationary

seal endface,

endface

of

the

generating concentric are

within

stationary

formed which seal

grooves with

the

on

the

is the seal ring.

be

gases.

at

the

high

the machine Under

the

be

working

to maintain

the seal endfaces when

high

force of the

the

balanced

machine

is

O-

in the casing

These keep the stationary

a specific

seal

portion

seal ring has engaging

holes on the back end, into which

wall portion.

are

An inner

ring is held by an outer circumferential of the inner

inner

the backward

two

in the axial direction.

rotation-preventing

seal ring (4) held by a seal casing (3) are

the sealed

(61)

(62).

apart

of the

the

of the seal casing via the

ring (63). The stationary

seals off the sealed region (F) at the outer circumferential

portion by

is held

O-ring

circumferential a

seal ring can slide in the

The static pressure-type

film formed

arranged

63) and In other

very well

than when

conditions,

But

first O-ring

62,

seal ring.

ring portion

forward

axial direction.

ring

circumferential

(61,

rotary

circumferential

seal

second

seal ring is held opposite

state that the stationary

an outer

its inner

the

force would

this, the spring

has to be set higher

in

seal ring via two O-rings

words,

and

This is held in the axial

O-rings

the

in a

the inner

at a high

work

inside

leaking

between

a stationary

the rotary

behind

between

of the casing

by three

placed

fixing

seal ring is placed

portion.

running

portion.

and

formed

portion

seal ring is

concentrically

seal

of the inner cylinder

shaft by sleeve-shaped

space

direction

cylinder

gas seal, the

operated

spring

gap properly

A rotary

forward

inner

with the rotary

The stationary

stationary

casing wall

the

(33) extends

of the seal gas has to be

the opening

great so to counter

and a ring-shaped

shaft

rotary

over

operated

cannot

the pressure

to keep the gas from

of the

the inner

rotary

or

within with

advantages

equipment

The pressure

portion

surrounding

them.

a seal

cylinder

The

through

circumferential

it, and

portion

seal completely

used

when

and

inner

surrounding

the earlier

type non-contact

has problems

pressure.

hand,

with such hazardous

seal

pressure

internal with

employed

be

not

by a static

gas seal with

a easing

shaft

seal

cylinder

circumferential

wall

fixed on the rotary

cylinder

are achieved

seal casing,

the inner

be

flammable

non-contact

can

seal

dynamic

must

toxic,

of the gas from

it

this

the

of gas which

gases. On the other

prevents

former

that

the

gas seal cannot

including

static pressure-type

of the gas

between

means

so

state.

as

an inner

inner

(32) of the casing,

ring-shaped

the casing inner cylinder

maintained

produced

leaking

connecting

stationary

by the gas inside

non-contact

outside,

explosive

is

ring mounted

an inner circumferential

fixed on a rotary

seal

rotates.

are kept in a non-contact

for the kind

leaked

generating

which

non-contact

portion

concentrically

gas

as much

of the gas seal

casing them.

of one

comprising

portion,

connecting

portion

load

a circular

ring-shaped

to an impact

conditions

cylinder

(32) concentrically

a

members.

the other.

casing

portion

of damaging

endface

against

pressure

comprises

(31),

a static

spring

due

These

over a

seal

the inside

the non-contact

portion

the possibility

the seal parts

(1) shown

pressure-generating

this seal tolerates

pressure-type

gas seals.

gas seal, as it is

pressure

the seal endfaces

within

in

be sealed

pressure

of these

that the endfaces

from

effective

cannot

so thar one seal endface

dynamic

In principle,

the required to preclude

through

endfaces

non-contact

dynamic

a

are

pressure-type

operation

grooves,

seal

a

state and with no

they

pressure-type

grooves

berween

the

of gas which

dynamic

known,

reduces

The seal casing

seal off the the

with

in which

is mounted.

pressure-type

of

communicating

It also provides

non-contact

possible

portion,

of shortcomings

seal the gas inside

with

Furthermore,

With

for and

of such seals. This

in a non-contact

the kind

The

valves, explosive

had a number

can effectively

maintained

irrespective

region

rotary machine

crash

can operate

and effectively

at that region.

pressure-type

blowers,

rotary

flammable,

the application

new design

sealing

for use in

gases.

limit

seizing.

non-

may damage.

a static

seal casing concentrically

Earlier designs which

suitable

and

toxic,

Co, Japan

as turbines,

agitators

compressors, gases including

used

Packing

gas seal is described,

rotary

range

pressure-type

ring

seal ring, causing provides

fluid

conditions

US 6135458

Date: 24 October Inventor:

sealed

gas seal

force of the spring

seal

gas seal which

wide pressure Title: Static

if the spring stationary

cut off, the

force are out of

Dmd2

I I

A

continuous

seal

municating passes

gas

with

supply

the grooves

through

the

seal

channel

com-

is formed,

which

casing

and

the

stationary

seal ring. Because

of the difference

diameter

between

and

circumferential to

portions,

the

first

pushing

the

rotary

the first

closed

space

This

This arrangement

closes

with

force

to counter

necessary

Furthermore, designed second

pressure

in the sealed

back-pressure back-pressure against

pushes

the rotary

further

in the sealed fluid can

operation

region

be

gas cut off, there

low.

to changes region.

Even when therefore,

opening

force

exhibiting

the spring And

that

when of seal

the spring

to impact

force changes

in the pressure

region,

is high

with the supply

is no concern

The closing

Even under

therefore,

load will allow the seal endfaces other.

force

the pressure

relatively

is suspended,

seal ring

closing

load.

where region,

set

may act as

seal ring. This

the stationary

the spring

conditions

is the

path, so that the

seal ring. This

alleviates

operating

fluid

ring and

with each other

on the stationary

each

during shaft

start-up

these

of the sealed

the pressure

changes

the

force

fluid in this

and

will be well balanced,

a housing assembly,

the

secondary

The

compression surfaces,

with

surface

biasing

of the gland

between

with

the rotary comprises

The O-ring

is generally

housing.

sealing O-ring

is typically

mounted

the O-ring

of the

surface

of

increasing seal ring

the

of the

of the first

A drawback inability

through

of these

This expansion,

seal ring movement

surface

fluid and

force that biases the rotary

secondary

of the stationary

the rotary

‘hang-up’.

to

in sealing engagement

the first seal ring and the inner

the

The spring

seal

other.

track

an axial and member,

radial

the frictional with

component.

the

undesirably

ring, to enable the rings to move relative to each

of the compression

to impart

or other

seal ring

in the axial and

significantly

engagement

spacer

mounted

The area in which

seal ring towards

a sealing

seal face. This

the spacer plate, the stationary

and the fluid

directions,

a

at the rear

a spring,

the stationary

for axially

force on the sealing

place the sealing member

a good sealing function.

assembly

an axial biasing

and

fluid

seal to help bias the stationary

plate generate

the

seal

employ

mounted

and

the rear surface

is configured sealing

seals typically

assembly

member

front

seal ring or the front surface

mechanical

housing

and the rear surface

first seal ring. Either

member

rear

seal ring

in minimising

the rear

plate,

the

member

and

to

of the seal faces and thus

assists

sealing

compresses a

systems

of the rotary

between

assembly

the compression

member

assembly. includes

front

member

of the compression

between

fluid sealing

assembly

member

a resilient

surface inner

sealing

to

passes.

leakage.

and O-ring.

assembly,

the seal rings and the gland

secondary

fluid

the stationary

the movement

ring. The manipulation

secondary

a seal face. The

provides

sealed

in existing

the leakage,

seal ring face towards

shaft includes

sealing

each with

sealing assembly

between

radial

thereby

a secondary

two seal rings

which

of leakage across the seal faces.

of the stationary

require

fluid sealing

and a rotatable

mech-

of the seal faces occurs

desirable

tracks

secondary

of the shaft.

seal for providing

closely

Existing

for low-

which

it is generally

of the gap width

this

non-contacting

and stopping

of non-contacting

a gap through

To limit a

when

For

form

limit the amount

can

periods

speeds.

or for conditions

starting

A mechanical

and

or during at low

conventional

speed operation

a gland

faces,

operation

anical seals, separation

Since passage of the sealed fluid is unavoidable,

of

hydro-

seal

face seals are unsuitable

frequent

between

to provide the

of seal face abrasion

is rotating

reason,

seals,

areas

in seal designs which

of

amount

compression

in proportion

closing

occur

face in some

on rotation

separation

mechanical

region

lead-in

dynamic

of the seal faces.

drawbacks

For example,

During

the seal faces

non-contacting

exhibit

rely primarily

the

force is

seal

sealed

closed space commutate a back-pressure

force

the opening

stationary

the

through

load,

the closing

the seal faces. The

and abrasion

Conventional

substantial

load alone.

the

so that

the spring

a case where

by the spring

the

separates

rubbing

performance.

a force

against

that

gap allows fluid between

however,

the seal endfaces.

thus reduces

in comparison

obtained

produces

seal ring

force

to prevent

in

outer

the seal gas supplied

stationary

seal ring.

second

lifting resultant

seals is the

seal ring

seal ring

because

typically

occurs

contraction generated

to closely of seal face

when

either

or other

typical

during

operation,

of

the gland assembly. Conventional

Skondary sealing for face seals

a pressure-

rotating

shaft and a stationary

is usually

mechanical

sealing assembly for

positioned

to the housing pressurised

Date: 19 September 2000

Conventional

Inventors:

C.A. Kowalski

et al.

Assignee: A.W. Chesterton Massachusetts,

Company,

sealing

USA

shaft,

sealing

between

In particular, which

relates to seals for providing a housing

and a rotating

it relates to mechanical

a fluid is introduced

between

fluid shaft.

Conventional a fluid

reduce

frictional

non-contact between

pumping

Raleigh

step grooves,

formed

faces of the seal rings to develop

0

rings concentrically

disposed from

contact

with

one seal ring remains

each other.

stationary,

process

to

as spiral

or

in one of the seal a hydrodynamic

environment

prevents

by biasing

faces into physical

the

seals

typically

characteristics

to

the

the seal ring

contact

result of the repeated the faces, abrasion

with it. The

leakage

fluid

Usually,

while the other

pressurised seals

the The

rings each have seal faces that are biased

into physical

the shaft and rotates

faces

about

each other.

seal

mechanical

such

lace-type

a pair of annular

mechanical

the seal ring

grooves,

seals include

ring contacts

of

loss of

housing.

include

spaced

the

butted

the

portions

wear. Such face seals typically

employ

from

face seals in

the faces of the seal.

utilise

seals, which

and axially

sealing This invention

shaft,

from

at the shaft exit, to prevent

mechanical

mechanical

the rotating protrudes

fluid

a

The seal

The seal is typically

process

to

seal between

housing.

about in and

housing.

Patent number: US 6120034

equipment

and fluid-tight

is mounted

stationary

face seal

seals are employed

of mechanical

provide

which Tide: Secondary

mechanical

in a wide variety

of

sealing

with each other. As a

physical

contact

between

of the seal faces occurs exhibit

the

external

undesirable

and wear

and leakage.

Sealing Technology No. 86