SIST EN ISO 21049:2005

SLOVENSKI STANDARD
SIST EN ISO 21049:2005
01-april-2005
ýUSDONH6LVWHPLJUHGQLKWHVQLON]DFHQWULIXJDOQHLQURWDFLMVNHþUSDONH,62

Pumps - Shaft sealing systems for centrifugal and rotary pumps (ISO 21049:2004)
Pumpen - Wellendichtungssysteme für Kreiselpumpen und rotierende
Verdrängerpumpen (ISO 21049:2004)
Pompes - Dispositifs d'étanchéité de l'arbre pour pompes centrifuges et rotatives (ISO
21049:2004)
Ta slovenski standard je istoveten z: EN ISO 21049:2004
ICS:
21.140 Tesnilke, mašilke Seals, glands
23.080 ýUSDONH Pumps
SIST EN ISO 21049:2005 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------

SIST EN ISO 21049:2005

---------------------- Page: 2 ----------------------

SIST EN ISO 21049:2005
EUROPEAN STANDARD
EN ISO 21049
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2004
ICS 23.100.60; 23.080; 83.140.50
English version
Pumps - Shaft sealing systems for centrifugal and rotary pumps
(ISO 21049:2004)
Pompes - Dispositifs d'étanchéité de l'arbre pour pompes Pumpen - Wellendichtungssysteme für Kreiselpumpen und
centrifuges et rotatives (ISO 21049:2004) rotierende Verdrängerpumpen (ISO 21049:2004)
This European Standard was approved by CEN on 21 December 2004.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Central Secretariat or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2004 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 21049:2004: E
worldwide for CEN national Members.

---------------------- Page: 3 ----------------------

SIST EN ISO 21049:2005
EN ISO 21049:2004 (E)






Foreword



The text of ISO 21049:2004 has been prepared by Technical Committee ISO/TC 115 "Pumps" of
the International Organization for Standardization (ISO) and has been taken over as EN ISO
21049:2004 by Technical Committee CEN/TC 12 "Materials, equipment and offshore structures
for petroleum and natural gas industries" the secretariat of which is held by AFNOR.

This European Standard shall be given the status of a national standard, either by publication of
an identical text or by endorsement, at the latest by June 2005, and conflicting national
standards shall be withdrawn at the latest by June 2005.

NOTE Attention is drawn to the fact that Clause 10.2.3 permits the use of alternative standards
(e.g. EN 13445-5) for the non-destructive examination of materials

According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary,
Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

Endorsement notice

The text of ISO 21049:2004 has been approved by CEN as EN ISO 21049:2004 without any
modifications.

2

---------------------- Page: 4 ----------------------

SIST EN ISO 21049:2005
ISO 21049:2004(E)
RECOMMENDED SEAL SELECTION PROCEDURE (US CUSTOMARY UNITS)
SHEET 1 OF 10


© ISO 2004 – All rights reserved 103

---------------------- Page: 5 ----------------------

SIST EN ISO 21049:2005
ISO 21049:2004(E)
RECOMMENDED SEAL SELECTION PROCEDURE (US CUSTOMARY UNITS)
SEAL CATEGORY, TYPE, AND ARRANGEMENT SUMMARY
SHEET 2 OF 10
Seal category shall be Category 1, 2 or 3 as specified.
The major features of each category are summarized below. Options, where they exist for each feature, are
listed in the text as “if specified”. Clause numbers in parentheses indicate where the requirements are
specified.
FEATURE CATEGORY 1 CATEGORY 2 CATEGORY 3
Seal chamber size. ISO 3069 Type C, ISO 13709. ISO 13709.
(4.1.2) ASME B73.1 and
ASME B73.2.
Temperature range. – 40 °F to 500 °F – 40 °F to 750 °F – 40 °F to 750 °F
(4.1.2)
Pressure range, absolute. 315 psi 615 psi 615 psi
(4.1.2)
Face materials. Premium blister-resistant Premium blister-resistant Premium blister-resistant
(6.1.6.2) carbon vs. self-sintered carbon vs. reaction-bonded carbon vs. reaction-bonded
silicon carbide. silicon carbide. silicon carbide.
Distributed inlet flush When required per 6.1.2.14 When required per 6.1.2.14 Required.
requirements, or if specified. or if specified. (6.2.3.2)
Arrangements 1 and 2 with (6.2.1.2.1) (6.2.2.2.1)
rotating flexible elements.
Gland plate metal-to-metal Required. Required inside and outside Required inside and outside
contact requirement. (6.2.1.2.2) of the bolt circle diameter. of the bolt circle diameter.
(6.2.2.2.2) (6.2.2.2.2)
Cartridge seal sleeve size None 10 mm increments. 10 mm increments.
increments required. (6.2.2.3.1) (6.2.2.3.1)
Throttle bushing design Fixed carbon. Floating Fixed, non-sparking metal. Floating carbon.
requirement for carbon option. Floating carbon option.
Arrangement 1 seals. (7.1.2.2) (7.1.2.2)
(7.1.2.1)
Dual-seal circulation device If specified. If specified. Required.
head flow curve provided. (8.6.2.2) (8.6.2.2) (8.6.2.2)
Scope of vendor qualification Test as Category 1 unless Test as Category 2 unless Test as Category 3, entire
test. faces interchangeable with faces interchangeable with seal assembly as a unit.
Category 3. Category 3. (10.3.1.2.2)
(10.3.1.2.3) (10.3.1.2.3)
Proposal data requirements. Minimal. Minimal. Rigorous, including
(11.2.1) (11.2.1) qualification test results.
(11.2.1)
Contract data requirements. Minimal. Minimal. Rigorous.
(11.3.1) (11.3.1) (11.3.1)

104 © ISO 2004 – All rights reserved

---------------------- Page: 6 ----------------------

SIST EN ISO 21049:2005
ISO 21049:2004(E)
SHEET 2 OF 10 (continued)
Seal type shall be Type A, B, or C as specified.
The major features of each type are summarized below. Options, where they exist for each feature, are listed
in the text as “if specified”. Clause numbers in parentheses indicate where the requirements are specified.
FEATURE TYPE A TYPE B TYPE C
Standard temperature – 40 °F to 350 °F – 40 °F to 350 °F – 40 °F to 750 °F
application range.
(4.1.3)
Hydraulic balance Balanced (e.g. hydraulic Balanced (e.g. hydraulic Balanced (e.g. hydraulic
requirement. balance less than 1). balance less than 1). balance less than 1).
(4.1.3 and 6.1.1.7)
Mounting requirement. Inside the seal chamber. Inside the seal chamber. Inside the seal chamber.
(4.1.3)
Cartridge requirement. Cartridge design. Cartridge design. Cartridge design.
(4.1.3 and 6.1.1.1)
Flexible element style. Pusher (e.g. sliding Non-pusher (e.g. bellows). Non-pusher (e.g. bellows).
(4.1.3) elastomer).
Flexible element orientation. Rotating. Rotating. Stationary.
(4.1.3) Stationary option. Stationary option. Rotating option.
(6.1.1.2) (6.1.1.2) (6.1.1.3)
Bellows material. Not applicable. Alloy C-276 Alloy 718
(6.1.6.6)
Spring type. Multiple-coil springs. Single bellows. Single bellows.
(4.1.3) Single spring option.
(6.1.5.1)
Limit for stationary element 4 500 ft/min 4 500 ft/min 4 500 ft/min
application.
(6.1.1.5)
Secondary sealing element Elastomer. Elastomer. Flexible graphite.
material.
(4.1.3)

© ISO 2004 – All rights reserved 105

---------------------- Page: 7 ----------------------

SIST EN ISO 21049:2005
ISO 21049:2004(E)
SHEET 2 OF 10 (continued)
Seal arrangement shall be Arrangement 1, 2, or 3 as specified.
The major features of each arrangement are summarized below. Options, where they exist for each feature,
are listed in the text as “if specified”. Clause numbers in parentheses indicate where the requirements are
specified.
FEATURE ARRANGEMENT 1 ARRANGEMENT 2 ARRANGEMENT 3
Number of “seals” per One Two Two
cartridge, see definition of (3.2 and 4.1.4) (3.3 and 4.1.4) (3.4 and 4.1.4)
“seal” in 3.61. (4.1.4)
Uses a barrier or buffer fluid. No Sometimes but not required. Yes, barrier fluid required,
(4.1.4) Liquid or gas buffer liquid or gas permitted.
permitted.
Allows non-contacting (wet No Yes, Figure 4. Yes, Figure 6.
or dry) seals. (4.1.4)
Arrangement 1 throttle Category 1: Fixed carbon. Not applicable. Not applicable.
bushing requirement. Category 2: Fixed, non-
(7.1.2.1) sparking metallic.
Category 3: Floating carbon.
Arrangements 2 & 3 throttle Not applicable. Fixed carbon, if specified. Fixed carbon, if specified.
bushing requirement. (7.2.3) (7.3.3.1)
Arrangement 2 containment Not applicable. Required with dry-running Not applicable.
seal chamber bushing containment seal regardless
requirement. of inner seal design. (7.2.5.1
and 7.2.6.1)
Tangential buffer/barrier fluid Not applicable. If specified, for Categories 1 If specified, for Categories 1
outlet required ? and 2. Required for and 2. Required for
Category 3. (7.2.4.2) Category 3. (7.3.4.3)
Maximum buffer/barrier fluid Not applicable. 15 °F aqueous or diesel, 15 °F aqueous or diesel,
temperature rise. 30 °F mineral oils. (7.2.4.1) 30 °F mineral oils. (7.3.4.1)
Seal chamber pressure/flush Minimum margin of 30 % of Minimum margin of 30 % of None
design requirement. seal chamber pressure seal chamber pressure
(6.1.2.14) above fluid vapour pressure above fluid vapour pressure
or 36 °F margin. or 36 °F margin.
Minimum operating seal 5 psi above atmospheric. 5 psi above atmospheric. None
chamber pressure
requirement. (6.1.2.14)
Minimum gland plate See Table 1. See Table 1. See Table 1.
connection sizes and
orientation.
Minimum barrier/buffer fluid Not applicable. 3 U.S. gal for shaft diameter 3 U.S. gal for shaft diameter
liquid reservoir. 2,5 in and smaller; otherwise 2,5 in and smaller; otherwise
5 U.S. gal [8.5.4.3 a)] 5 U.S. gal [8.5.4.3 a)]
Test requirements. (10.3.1.2.8) (10.3.1.2.9) and (10.3.1.2.11) and
(10.3.1.2.10) (10.3.1.2.12)

106 © ISO 2004 – All rights reserved

---------------------- Page: 8 ----------------------

SIST EN ISO 21049:2005
ISO 21049:2004(E)
RECOMMENDED SEAL SELECTION PROCEDURE (US CUSTOMARY UNITS)
SHEET 3 OF 10
Non-hydrocarbon services
 Operating conditions, recommended seal types and special features
Fluids 1 2 3 4 5 6 7 8
a
Water Water Water Sour Sour Caustic, Caustic, Acids
water water amines amines H SO ,
2 4
crystallize crystallize H PO
3 4
Pumping < 180 < 180 > 180 < 180 < 180 < 180 < 180 < 180
temp., °F
Seal < 300 < 300 < 300 < 300 < 300
chamber
gauge
pressure,
psig
Category 1
seals
Seal < 300 300 to 600 < 600 < 300 300 to 600 < 300 300 to 600 < 300
chamber
gauge
pressure,
psig
Category 2
and 3 seals
Standard Type A Type A Type A Type A Type A Type A Type A Type A
seal type
b b b b
Options Type B ES ES Type B ES Type B ES Type B
when Type C Type C Type C Type C
specified
Required  Circulating Perfluoro- Perfluoro- Amine- Amine- Perfluoro-
special device elastomer elastomer resistant resistant elastomer
features perfluoro- perfluoro- and single
elastomer elastomer spring for
Type A
seals
Special Abrasive Hardface Hardface Hardface Hardface Hardface Hardface Hardface Hardface
features particulates vs vs vs vs vs vs vs vs
for hardface hardface hardface hardface hardface hardface hardface hardface
contami-
c
nants
This selection procedure chooses seal designs consistent with the default positions throughout this International Standard. Listed
options meeting this International Standard might perform equally well.
a
Up to 20 % H SO at 77 °F only. Up to 20 % H PO at 176 °F only. All other acids, including hydrofluoric acid, fuming nitric acid and hydrochloric acid
2 4 3 4
require special engineering agreed between purchaser and vendor.
b
Totally engineered sealing system. Consult vendor to ensure special design considerations are accounted for.
c
Special features listed apply only in mixtures having pH between 4 and 11.

© ISO 2004 – All rights reserved 107

---------------------- Page: 9 ----------------------

SIST EN ISO 21049:2005
ISO 21049:2004(E)
RECOMMENDED SEAL SELECTION PROCEDURE (US CUSTOMARY UNITS)
SHEET 4 OF 10
Non-flashing hydrocarbons
 Operating conditions, recommended seal types and special features
Fluids 1 2 3 4 5 6 7 8
Pumping – 40 to 20 – 40 to 20 20 to 350 20 to 350 350 to 500 350 to 500 500 to 750 500 to 750
temp., °F
Seal < 300 < 300 < 300 N/A N/A
chamber
gauge
pressure,
psig
Category 1
seals
Seal < 300 300 to 600 < 300 300 to 600 < 300 300 to 600 < 300 300 to 600
chamber
gauge
pressure,
psig
Category 2
and 3 seals
a a
Standard Type A Type A Type A Type A Type C ES Type C ES
seal type
a, b a, b a a
Option when Type B ES Type B ES ES ES
specified
Option when Type C Type C
specified
Required Nitrile Nitrile
special O-rings O-rings
features
Special Caustic  Perfluoro- Perfluoro-
features elastomer elastomer
for
Abrasive Hardface Hardface Hardface Hardface Hardface Hardface Hardface Hardface
contami-
c particulates vs vs vs vs vs vs vs vs
nants
hardface hardface hardface hardface hardface hardface hardface hardface
Aromatics  Perfluoro- Perfluoro-
and/or H S elastomer elastomer
2
Amines  Amine- Amine-
resistant resistant
perfluoro- perfluoro-
elastomer elastomer
This selection procedure chooses seal designs consistent with the default positions throughout this International Standard. Listed
options meeting this International Standard might perform equally well.
a
Totally engineered sealing system. Consult vendor to ensure special design considerations are accounted for.
b
Engineered (high pressure) bellows.
c
Special features listed apply only in mixtures having pH between 4 and 11.

108 © ISO 2004 – All rights reserved

---------------------- Page: 10 ----------------------

SIST EN ISO 21049:2005
ISO 21049:2004(E)
RECOMMENDED SEAL TYPE SELECTION PROCEDURE (US CUSTOMARY UNITS)
SHEET 5 OF 10
Flashing hydrocarbons
 Operating conditions, recommended seal types and special features
Fluids 1 2 3 4 5 6 7 8
Pumping – 40 to 20 – 40 to 20 20 to 350 20 to 350 350 to 500 350 to 500 500 to 750 500 to 750
temp., °F
Seal < 300 < 300 < 300 N/A N/A
chamber
gauge
pressure,
psig
Category 1
seals
Seal < 300 300 to 600 < 300 300 to 600 < 300 300 to 600 < 300 300 to 600
chamber
gauge
pressure,
psig
Category 2
and 3 seals
d d a, b a, b
Standard Type A Type A Type A Type A Type C ES Type C ES
seal type
a a, b a a, b a a
Option when ES ES ES ES ES ES
specified
Required Nitrile Nitrile
special O-rings O-rings
features
Special Caustic  Perfluoro- Perfluoro-
features elastomer elastomer
for
Abrasive Hardface Hardface Hardface Hardface Hardface Hardface Hardface Hardface
contami-
c particulates vs vs vs vs vs vs vs vs
nants
hardface hardface hardface hardface hardface hardface hardface hardface
Aromatics  Perfluoro- Perfluoro-
and/or H S elastomer elastomer
2
Amines  Amine- Amine-
resistant resistant
perfluoro- perfluoro-
elastomer elastomer
Ammonia NH - NH - NH - NH - NH - NH - NH - NH -
3 3 3 3 3 3 3 3
resistant resistant resistant resistant resistant resistant resistant resistant
carbon carbon carbon carbon carbon carbon carbon carbon
graphite graphite graphite graphite graphite graphite graphite graphite
This selection procedure chooses seal designs consistent with the default positions throughout this International Standard. Listed
options meeting this International Standard might perform equally well.
a
Totally engineered sealing system. Consult vendor to ensure special design considerations are accounted for.
b
Engineered bellows.
c
Special features listed apply only in mixtures having pH between 4 and 11.
d
Requires special feature (circulating device) above 140 °F, and special feature (perfluoroelastomer) if pumping temperature is above 350 °F.

© ISO 2004 – All rights reserved 109

---------------------- Page: 11 ----------------------

SIST EN ISO 21049:2005
ISO 21049:2004(E)
RECOMMENDED SEAL ARRANGEMENT SELECTION PROCEDURE (US CUSTOMARY UNITS)
SHEET 6 OF 10


110 © ISO 2004 – All rights reserved

---------------------- Page: 12 ----------------------

SIST EN ISO 21049:2005
ISO 21049:2004(E)
SHEET 6 OF 10 (continued)



© ISO 2004 – All rights reserved 111

---------------------- Page: 13 ----------------------

SIST EN ISO 21049:2005
ISO 21049:2004(E)
RECOMMENDED SEAL TYPE SELECTION PROCEDURE (US CUSTOMARY UNITS)
SHEET 7 of 10
Non-hydrocarbon


112 © ISO 2004 – All rights reserved

---------------------- Page: 14 ----------------------

SIST EN ISO 21049:2005
ISO 21049:2004(E)
NOTE See A.4.13 for guidance on selecting Plan 53A, 53B or 53C.
a
The user should evaluate whether to add Plan 13 or not, considering such factors as the inclusion of a bleed bushing,
contamination of the seal chamber with pumped fluid, the need for venting of the seal chamber, and the need to reduce
seal chamber pressure, due to static or dynamic pressure rating of the seal versus the expected static and dynamic seal
chamber pressure.
b
If Plan 31, 32 or 41 is selected and pump is vertical, Plan 13 is also recommended for venting. Users should consider
installation of a “bleed bushing” design, in which an annulus and port cut into the throat bushing is connected to suction to
keep solids out of the seal chamber. Ensure seal chamber is vented prior to start-up.
c
Cooling is needed due to low lubricity at elevated temperature. The recommended flush plan is 23 because field
experience has shown that this plan is much less prone to plugging than Plan 21 due to recirculation of cooler fluid from
the seal chamber. However, the user may wish to reconsider using Plan 21 due to the added seal complexity imposed by
Plan 23 (size and cost) and other factors such as the use of an air cooler for Plan 21 in areas where water cannot be used
or is not available. (An air cooler works better on Plan 21 due to the higher temperature difference between the pumped
fluid and the cooling medium.) The user may also wish to consider the use of Plan 32 if a suitable fluid is available,
especially if the fluid is normally injected into the process anyway (such as make-up water). See the flush descriptions
later in this annex for additional detail.
d
Consider the need to add additional flushing to the process side of the inner seal. Flushing is sometimes needed for
Arrangement 3 FB orientation to provide additional cooling and Plan 11 or 13 may be a suitable choice. Other services
may require a Plan 32 flush if the pumped fluid is extremely corrosive, aggressive or solids-laden. Consider the need for
venting on vertical pumps. Special attention may be needed on Arrangement 3 NC configurations to ensure effective
pump operation. Consult the pump vendor if the pump is vented through the seal chamber, and consider the effects listed
a
in footnote above.

© ISO 2004 – All rights reserved 113

---------------------- Page: 15 ----------------------

SIST EN ISO 21049:2005
ISO 21049:2004(E)
RECOMMENDED SEAL SELECTION PROCEDURE (US CUSTOMARY UNITS)
SHEET 8 OF 10
Non-flashing hydrocarbon


114 © ISO 2004 – All rights reserved

---------------------- Page: 16 ----------------------

SIST EN ISO 21049:2005
ISO 21049:2004(E)
NOTE See A.4.13 for guidance on selecting Plan 53A, 53B or 53C.
a
The user should evaluate whether to add Plan 13 or not, considering such factors as the inclusion of a bleed bushing,
contamination of the seal chamber with pumped fluid, the need for venting of the seal chamber and the need to reduce
seal chamber pressure, due to static or dynamic pressure rating of the seal versus the expected static and dynamic seal
chamber pressure.
b
If Plan 31, 32 or 41 is selected and pump is vertical, Plan 13 is also recommended for venting. Users should consider
installation of a “bleed bushing” design, in which an annulus and port cut into the throat bushing is connected to suction to
keep solids or polymerizing agents out of the seal chamber. Ensure seal chamber is vented prior to start-up.
c
Cooling is needed due to temperature limits of the standard secondary elastomers for Arrangement 1 and possibly for
Arrangement 2 (consult the seal vendor). Consideration may be given to changing to perfluoroelastomer if cooling is not
possible. The recommended flush plan is 23 because field experience has shown that this plan is much less prone to
plugging than Plan 21 due to recirculation of cooler fluid from the seal chamber. However, the user may wish to re-
consider using Plan 21 due to the added seal complexity imposed by Plan 23 (size and cost) and other factors such as the
use of an air cooler for Plan 21 in areas where water cannot be used or is not available. (An air cooler works better on
Plan 21 due to the higher temperature difference between the pumped fluid and the cooling medium.) The user may also
wish to consider the use of Plan 32 if a suitable fluid is available, especially if the fluid is normally injected into the process
anyway (such as make-up water). See the flush descriptions later in this annex for additional detail.
d
Consider the need to add additional flushing to the process side of the inner seal. Flushing is sometimes needed for
Arrangement 3 FB orientation to provide additional cooling, and Plan 11 or 13 may be a suitable choice. Other services
may require a Plan 32 flush if the pumped fluid is extremely corrosive, aggressive or solids-laden. Consider the need for
venting on vertical pumps. Special attention may be needed on Arrangement 3 NC configurations to ensure effective
pump operation. Consult the pump vendor if the pump is vented through the seal chamber, and consider the effects listed
a
in footnote above.

© ISO 2004 – All rights reserved 115

---------------------- Page: 17 ----------------------

SIST EN ISO 21049:2005
ISO 21049:2004(E)
RECOMMENDED SEAL ARRANGEMENT SELECTION PROCEDURE (US CUSTOMARY UNITS)
SHEET 9 OF 10
Flashing hydrocarbon


116 © ISO 2004 – All rights reserved

---------------------- Page: 18 ----------------------

SIST EN ISO 21049:2005
ISO 21049:2004(E)
NOTE See A.4.13 for guidance on selecting Plan 53A, 53B or 53C.
a
The user should evaluate whether to add Plan 13 or not, considering such factors as the inclusion of a bleed bushing,
contamination of the seal chamber with pumped fluid, the need for venting of the seal chamber, and the need to reduce
seal chamber pressure, due to static or dynamic pressure rating of the seal versus the expected static and dynamic seal
chamber pressure.
b
If Plan 31, 32 or 41 is selected and pump is vertical, Plan 13 will also be recommended for venting. Users should
consider installation of a “bleed bushing” design, in which an annulus and port cut into the throat bushing is connected to
suction to keep solids or polymerizing agents out of the seal chamber. Ensure seal chamber is vented prior to start-up.
c
Cooling is recommended to suppress flashing within the seal faces. Due to cooling water temperatures, this is usually
only effective above the temperature shown. Below this temperature, or as an alternative to adding cooling, the user may
wish to use experience at their site or other alternatives such as high flushing rates, distributed flush systems, increased
seal chamber pressure, or combinations thereof, to obtain satisfactory seal life. There may also be the opportunity to use
Plan 32 if suitable flush fluid is available or, if experience is available, consideration of a change to Arrangement 3 may be
appropriate.
d
Consider the need to add additional flushing to the process side of the inner seal. Flushing is sometimes needed for
Arrangement 3 FB orientation to provide additional cooling, and Plan 11 or 13 may be a suitable choice. Other services
may require a Plan 32 flush if the pumped fluid is extremely corrosive, aggressive or solids-laden. Consider the need for
venting on vertical pumps. Special attention may be needed on Arrangement 3 NC configurations to ensure effective
pump operation. Consult the pump vendor if the pump is vented through the seal chamber, and consider the effects listed
a
in footnote above.

© ISO 2004 – All rights reserved 117

---------------------- Page: 19 ----------------------

SIST EN ISO 21049:2005
ISO 21049:2004(E)
RECOMMENDED SEAL ARRANGEMENT SELECTION PROCEDURE (US CUSTOMARY UNITS)
Buffer/barrier fluid selection
SHEET 10 OF 10
The following should be considered when selecting a barrier/buffer fluid:
 compatibility of the fluid with the process pumpage being sealed so as not to react with or form gels or
sludge if leaked into the process fluid or the process fluid into the barrier/buffer fluid;
 compatibility of the fluid with the metallurgy, elastomers, and other materials of the seal/flush system
construction;
 compatibility of the fluid assuming it reaches the process temperature (high or low).
On pressurized barrier fluid systems where the method of pressurization is a gas blanket, special attention
shall be given to the application conditions and barrier fluid selection. Normally, gas solubility in a barrier fluid
increases with increasing pressure and decreases with increasing barrier fluid temperature. As pressure is
relieved or temperatures rise, the gas is released from solution, and may result in foaming and loss of
circulation of the barrier fluid. This problem is normally seen where higher viscosity barrier fluids, such as lube
oils, are used at gauge pressures above 150 psi.
The viscosity of the barrier/buffer fluid should be checked over the entire operating temperature range with
special attention being given to start-up conditions. The viscosity should be less than 500 cSt at the minimum
temperature to which it is exposed.
The following barrier-fluid performance facts should be considered.
a) For services above 50 °F, hydrocarbon barrier/buffer fluids having a viscosity below 100 cSt at 100 °F
and between 1 cSt and 10 cSt at 212 °F have performed satisfactorily.
b) For services below 50 °F, hydrocarbon barrier/buffer fluids having a viscosity between 5 cSt and 40 cSt at
100 °F and between 1 cSt and 10 cSt at 212 °F have performed satisfactorily.
c) For aqueous streams, mixtures of water and ethylene glycol or propylene glycol are usually adequate.
Commercially available automotive antifreeze should never be used. The additives in antifreeze tend to
plate out on seal parts and cause failure as a result of gel formation.
d) The fluid should not freeze at the minimum ambient temperature at the site.
Fluid volatility and toxicity of the fluid shall be such that leakage to the atmosphere or disposal does not
impose an environmental problem. In addition,
 the fluid should have an initial boiling point at least 50 °F above the temperature to which it will be
exposed;
 the fluid should have a flash point higher than the service temperature if oxygen is present;
 ethylene glycol may be considered a hazardous material and/or hazardous waste when used as a barrier
fluid.
The fluid should be able to meet the minimum 3-year continuous seal operation criteria without adverse
deterioration. It should not form sludge, polymerize or coke after extended use.
For hydrocarbon streams, paraffin-based high purity oils having little or no additives for wear/oxidation
resistance, or synthetic-based oils have been used successfully.
Anti-wear or oxidation-resistance additives in commercial turbine oils have been known to plate out on seal
faces.
118 © ISO 2004 – All rights reserved

---------------------- Page: 20 ----------------------

SIST EN ISO 21049:2005
ISO 21049:2004(E)
A.2 Tutorial clause
A.2.1 Seal selection justification
A.2.1.1 All seal selections by service were made with the following considerations in mind:
a) to produce a reliable sealing system that has a high probability of operating 3 years of uninterrupted
service, meeting or exceeding environmental emission regulations;
b) personnel and plant safety in hazardous services; and
c) to minimize spare parts inventory required for insurance stock.
A.2.1.2 All selections were made using experience of engineering, purchasing, operating, retrofitting and
maintaining mechanical seals in various services and locations. The selections were made to ensure that the
best seal for the service will be installed. Surely, a seal not specified by this International Standard is
operating successfully in a given service somewhere. This International Standard does not attempt to prevent
the selection of other seals. However, if a seal not specified by this International Standard is chosen, special
engineering is recommended for successful operation.
Any seal operating with a seal chamber gauge pressure above a gauge pressure of 2,1 MPa (21 bar)
...