Gland
Must be lubricated at all times
!
"
#
$
%

'
(
 
Discarge PressureDiscarge Pressure
Stuffing Bo! PressureStuffing Bo! Pressure
Te actual pressure" positi#e or negati#e at te pump suction
connection as measure$ on a gage%
Te actual pressure at te pump $iscarge connection as measure$ on a gage%
&t is e'ual to te pump suction pressure plus total ea$ $e#elope$ (y te pump%
Te pressure acting on te stuffing (o! )ic must (e seale$%
&t is a function of pump impeller $esign an$ te presence or con$ition of
)ear rings%
Stuffing Bo! PressureStuffing Bo! Pressure
•The pressure acting on the stuffing box which must be sealed. •It is a function of pump impeller design and the presence or
condition of wear rings.  
Back vanes - Open impeller 
Balance %oles - &losed impeller 
)ouble Suction
 
*iscosity*iscosity • *enerall+ the higher the viscosit+, the better the
  lubricating characteristics •  product with a viscosit+ of !(,((( SS /"((( cp0
  can be sealed with standard seals • Be+ond "((( cp, the drive unit has to be beefed up to
compensate for the increased shear occurring at the
sealing faces. • 1or high viscous applications2
Single seal with external flush
)ouble seal with external flush • The viscosit+ 3 lubricit+ of water decrease with increased
temperature. bove 4!°& /viscosit+ (.5" cp0 seal faces can
contact each other and wear rapidl+, unless speciall+ designed
 
,ecirculation,ecirculation
SuctionSuction
,ecirculation,ecirculation
/o) Bearing /o) Bearing
Ca#itationCa#itation   2     .
 
• Use 8-10 L! in su"tion #ine
• Operate pump $it minimum &5 psi over vapor
pressure
• Proper#' app#' se#e"ted pipin( p#an )*a "oo# sea#
is a app' sea#,
 
Specific *ravit+ $ )ensit+ of a substance
  )ensit+ of 6ater at 7°&
Specific gravit+ is used to estimate the lubricit+ of light h+drocarbons
 
Pac-Seals Flow Solutions Division
*apour Pressure*apour Pressure
The pressure at which a li9uid will flash into vapor at given temperature
I1 seal generated heat causes the sealing li9uid to boil in seal chamber
 pressure, the li9uid film between the seal faces will vapori:e.
Solution :
• Increase seal chamber pressure with proper b+pass flush line and
 
Operated under cavitating conditions for sufficient length of time:
•;itting of impeller vanes and pump volute •Short bearing life and heav+ loading •Shaft breakage and other fatigue failures in the pump •Short seal life
Damages to mechanical seals can be :
 
Ca#itationCa#itation
i( peed video so$s tat sea# fa"e temperature e/"ursions o""urred $en
(ases $ere dra$n a"ross te sea# fa"es and ' te formation of (as u#es
in te sea# "amer near te sea# fa"es durin( pump "avitation.
ea# performan"e durin( "avitation
ea# "amer
ea# fa"e
viration4 mi#s p-p 7 &.0 1 to 5
ea# fa"e
 
Pac-Seals Flow Solutions Division
Disa$#antages of Compression pacingsDisa$#antages of Compression pacings
•Power consumption is HIGH.
compression packing is '24
=aries with compression on the packings. The ratio of >eakage
of mechanical seal to compression packing is '28((
•#o automatic wear compensation
 
/eaage rates/eaage rates
Pressure
0 - 30 )0 - 600, 30 6
31 - 100 )601 - 900, 10
101 - &50 )901 - 1900, 690
Lea:a(e
Pac-Seals Flow Solutions Division
.eat eneration of lan$ Pacing.eat eneration of lan$ Pacing  The heat generation at the packing can be estimated as :
Q = f π2 P N D2 L   --------------------
  C J
where Q = heat generated !t"#min $%&
f = co-e'cient of friction P = (i)"id press"re at packing (b#in2 gage $Pa&
N = *haft speed rpm
L = *(ee+e (ength co+ered b. packing in $m&
C = /2 $01 for * "nit&  J = mechanica( e)"i+a(ent of heat = 3 ft 4 (b # !t" $/ N4m#s4%&
 The co-e'cient of +ario"s packings at a press"re of /11 (b#in2 $035 kPa& is gi+en be(ow4
;ateria# f  
 
ecanical Sealsecanical Seals
By :rrangementBy :rrangement
ecanical Sealsecanical Seals
By DesignBy Design ;n(alance$
) *aces must be flat to  +ithin # light bands ,#$(
millionth of an inch- Most are ! light band ,!! millionths-
 
@n"one# 300
ast 2-&93 ir"onium
e##o$s
2erami" - Perami"
<un(sten 2aide  D Ci inder 
<un(sten 2aride  D 2o inder 
<un(sten 2aride - Binder#ess
te##ite
 
F 3 2aron CA 2aron )A"id esistant D =,
F 19 2aron
F 1 2aron
H 2aron )Antimon' @mpre(nated,
 AE 2aron )!r' unnin( (rade,
 
Iiton )=#uro"aron,
>rapite fi##ed <ef#on
Ceoprene >rafoi# )!urafite,
Pure <ef#on
1/ring
PointsPoints
;n(alance$ Seals - 0orces :cting on Seal 0aces
Spring /oa$
 
Balance$ Seals - 0orces :cting on Seal 0aces
Spring /oa$
Pac-Seals Flow Solutions Division
<at is a ligt (an$=<at is a ligt (an$=
@t is a unit of measure.
 D One #i(t and J .0000113
 D <$o #i(t ands J .0000&
 D <ree #i(t ands J .00005
 
<o determine f#atness4
te and on one ed(e to
te same and on te
oter ed(e.
 
 
Gasket hang-up occurs when solids build-up sufficiently to impede gasket movement.
he spring!s closing force is disrupted and heavy leakage soon develops.
Solid "uild #p
on Puser Sealon Puser Seal
he secondary seal does not have to move along the shaft or sleeve
to maintain face contact