EN ISO 21049:2004
(Main)Pumps - Shaft sealing systems for centrifugal and rotary pumps (ISO 21049:2004)
Pumps - Shaft sealing systems for centrifugal and rotary pumps (ISO 21049:2004)
ISO 21049:2004 specifies requirements and gives recommendations for sealing systems for centrifugal and rotary pumps used in the petroleum, natural gas and chemical industries. It is applicable mainly for hazardous, flammable and/or toxic services where a greater degree of reliability is required for the improvement of equipment availability and the reduction of both emissions to the atmosphere and life-cycle sealing costs. It covers seals for pump shaft diameters from 20 mm (0,75 in) to 110 mm (4,3 in).
ISO 21049:2004 is also applicable to seal spare parts and can be referred to for the upgrading of existing equipment. A classification system for the seal configurations covered by ISO 21049:2004 into categories, types, arrangements and orientations is provided.
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)
L'ISO 21049:2003 spécifie des exigences et fournit des recommandations applicables aux dispositifs d'étanchéité pour des pompes centrifuges et rotatives utilisées dans les industries du pétrole, du gaz naturel et de la chimie. Elle est applicable principalement aux services dangereux, inflammables et/ou toxiques pour lesquels un degré de fiabilité plus important est requis afin de permettre d'améliorer la disponibilité des équipements et de réduire les émissions dans l'atmosphère ainsi que le coût du cycle de vie des dispositifs d'étanchéité. Elle couvre des dispositifs d'étanchéité pour des diamètres d'arbre compris entre 20 mm (0,75 in) et 110 mm (4,3 in).
L'ISO 21049:2003 est applicable également aux pièces de rechange des dispositifs d'étanchéité et peut être citée en tant que référence normative dans le cadre de rénovations d'équipements existants. Un système de classification est fourni, permettant de classer en catégories, types et dispositions les configurations des garnitures couvertes par l'ISO 21049:2003.
Črpalke - Sistemi grednih tesnilk za centrifugalne in rotacijske črpalke (ISO 21049:2004)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
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
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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.
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.
ISO 21049:2004(E)
RECOMMENDED SEAL SELECTION PROCEDURE (US CUSTOMARY UNITS)
SHEET 1 OF 10
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
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 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
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 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
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
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
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 21049:2004(E)
RECOMMENDED SEAL ARRANGEMENT SELECTION PROCEDURE (US CUSTOMARY UNITS)
SHEET 6 OF 10
110 © ISO 2004 – All rights reserved
ISO 21049:2004(E)
SHEET 6 OF 10 (continued)
ISO 21049:2004(E)
RECOMMENDED SEAL TYPE SELECTION PROCEDURE (US CUSTOMARY UNITS)
SHEET 7 of 10
Non-hydrocarbon
112 © ISO 2004 – All rights reserved
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 21049:2004(E)
RECOMMENDED SEAL SELECTION PROCEDURE (US CUSTOMARY UNITS)
SHEET 8 OF 10
Non-flashing hydrocarbon
114 © ISO 2004 – All rights reserved
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 21049:2004(E)
RECOMMENDED SEAL ARRANGEMENT SELECTION PROCEDURE (US CUSTOMARY UNITS)
SHEET 9 OF 10
Flashing hydrocarbon
116 © ISO 2004 – All rights reserved
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 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
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)
(300 psi) for Category 1 seals or a gauge pressure of 4,1 MPa (41 bar) (600 psi) for Category 2 and
Category 3 seals requires special engineering. Any product temperature above 260 °C (500 °F) for Category 1
seals and above 400 °C (750 °F) for Category 2 and 3 seals also requires special engineering design
considerations. Therefore, the selection categories are limited to the above pressures and temperatures for
this International Standard.
A.2.1.3 The seal references in this International Standard are:
a) Type A, standard pusher seal;
b) Type B, standard option for Type A, a non-pusher seal with rotating bellows and elastomeric secondary
sealing elements; and
c) Type C, standard non-pusher seal with stationary bellows and flexible graphite secondary sealing
elements.
See Clause 3, Clause 4 and sheet 1 of this annex, for further description.
NOTE Pressure levels listed apply to Category 1, Category 2 or Category 3 as noted on the applicable sheet.
A.2.2 Non-hydrocarbon services — Sheet 3
A.2.2.1 Clean water below 80 °C (180 °F) and below a gauge pressure of 2,1 MPa (21 bar) (300 psi)
The standard seal is a Type A standard pusher with no special features required.
The standard options are either a Type B or Type C metal bellows with no special features required.
A.2.2.2 Clean water below 80 °C (180 °F) and a gauge pressure of between 2,1 MPa (21 bar) (300 psi)
and 4,1 MPa (41 bar) (600 psi)
The standard seal is a Type A standard pusher with no special features required.
Any seal other than a Type A should be specially engineered for high pressure. Seal manufacturers normally
rate their metal bellows designs for gauge pressures of less than 2,1 MPa (21 bar) (300 psi). The seal
manufacturer should be consulted for specific performance data above this pressure.
ISO 21049:2004(E)
A.2.2.3 Water above 80 °C (180 °F) and at a gauge pressure below 4,1 MPa (41 bar) (600 psi)
The standard seal is a Type A pusher with special features. The special features are a single-spring seal with
an internal circulating device to circulate through a Plan 23 closed-loop system. As shown on sheet 7, a
Plan 21 might also be used, especially if an air cooler is used. The elastomer configuration can be either
O-ring or “U” cup.
The alternative seal is a Type A standard pusher with special features to include an internal circulating device
to circulate through a Plan 23 closed-loop system, and a close-clearance bushing in the bottom of the sealing
chamber.
A Plan 23 flushing arrangement is the most efficient way of providing a cool flush to the seal faces. Use of an
internal circulating device to circulate the fluid through a closed-loop cooler allows the cooler to continuously
cool a recirculated stream rather than a continuous (hot) stream from the discharge of the pump (Plan 21).
The cooler now has to cool only that fluid in the loop, and the duty cycle is much less severe than a Plan 21.
A survey in one facility revealed that the average temperature of the inlet flush to the sealing chamber was
50 °C (122 °F). The average pumping temperature of the product was 219 °C (426,2 °F). The idle pump’s
average inlet temperature was 38 °C (100,4 °F). The idle pumps rely only on the thermosyphon through the
cooler to cool the fluid. The cooler shall be mounted in accordance with this International Standard to ensure
proper thermosyphoning.
A.2.2.4 Sour water below 80 °C (180 °F) up to a gauge pressure of 4,1 MPa (41 bar) (600 psi)
The standard seal is a Type A standard pusher with special features. The elastomers shall be changed to
perfluoroelastomer to resist the H S, as H S is generally the agent that sours water.
2 2
The standard option up to a gauge pressure of 2,1 MPa (21 bar) (300 psi) is either the Type B or Type C seal
with the special feature of perfluoroelastomer for the Type B.
The use of Type B or Type C seal above a gauge pressure of 2,1 MPa (21 bar) 21 bar (300 psi) requires
special engineering for the high pressure.
This selection is made to maximize the standardization process, as the Type A seal is recommended for all
pressure ranges. Sour water may become flashing as the temperature and H S content increase.
A.2.2.5 Caustic, amines, and other crystallizing fluids below 80 °C (180 °F) and below a gauge
pressure of 4,1 MPa (41 bar) (600 psi)
The standard seal is a Type A standard pusher with the special features of perfluoroelastomer.
The standard alternative is a Type B metal bellows seal up to a gauge pressure of 2,1 MPa (21 bar) (300 psi)
with perfluoroelastomer.
The use of Type C seals up to a gauge pressure of 2,1 MPa (21 bar) (300 psi) with flexible graphite
secondaries should be specially engineered, as graphite is not recommended for some caustic applications.
For gauge pressures above 2,1 MPa (21 bar) (300 psi) but below 4,1 MPa (41 bar) (600 psi), the use of Type B
and Type C metal bellows seals require special engineering for the high pressure.
Any application in a crystallizing fluid requires the use of a Plan 62 quench or a Plan 32 flush to keep crystals
from forming on the atmospheric side of the seal. Most facilities prohibit a quench from seals unless totally
contained. A Plan 32 flush arrangement is generally not acceptable, as it dilutes the product and is sometimes
expensive to operate. In these conditions an Arrangement 2 dual seal (un-pressurized buffer) should be
considered, using clean water (or other compatible fluid) as a buffer to keep the crystals in solution. The same
special features apply to both the dual seal and the single seals.
120 © ISO 2004 – All rights reserved
ISO 21049:2004(E)
A.2.2.6 Acids: sulfuric, hydrochloric, phosphoric acids at less than 80 °C (180 °F) and below a gauge
pressure of 2,1 MPa (21 bar) (300 psi)
The standard seal is a Type A standard pusher with special features. The special features are a single coil-
spring.
The standard option is a Type B or Type C using flexible graphite as a secondary in the Type C.
Due to the thin cross-section of multiple-coil springs and bellows plates, select the most corrosion-resistant
material for the application.
Hydrofluoric, fuming nitric, and other acids are not covered in this selection. Specially engineered designs
agreed between the owner and the seal manufacturer should be used.
Seals for use with acids at temperatures over 80 °C (180 °F) require special engineering.
Seals for use with acids at a gauge pressure above 2,1 MPa (21 bar) (300 psi) require special engineering.
A.2.3 Non-flashing hydrocarbons [absolute vapour pressure less than 0,1 MPa (1 bar)
(14,7 psi) at pumping temperature] — Sheet 4
A.2.3.1 From – 40 °C (– 40 °F) to – 5 °C (20 °F) and below a gauge pressure of 4,1 MPa (41 bar)
(600 psi)
The standard seal is a Type A standard pusher with the special feature of NBR elastomers for the low
temperature service. The NBR shall also be compatible with the pumped fluid.
The standard alternative up to a gauge pressure of 2,1 MPa (21 bar) (300 psi) is either a Type B with the
special feature of NBR elastomers or a Type C with flexible graphite secondaries.
For gauge pressures over 2,1 MPa (21 bar) (300 psi), seal Types B and C require engineered bellows designed
for the high pressure.
The special feature of NBR elastomers is due to the low temperature requirements. The standard
fluoroelastomer is rated at – 17,7 °C (0 °F), but, for the applications of this International Standard,
fluoroelastomer should not be used below – 5 °C (20 °F).
A.2.3.2 From – 5 °C (20 °F) to 176 °C (350 °F) and gauge pressures below 4,1 MPa (41 bar) (600 psi)
The standard seal is a Type A standard pusher with no special features required. (Check elastomer
compatibility charts for pumped fluid).
The standard option for gauge pressures up to 2,1 MPa (21 bar) (300 psi) is a Type B or Type C standard
non-pusher. The Type C seal should be used with flexible graphite secondaries.
The standard alternative for gauge pressures above 2,1 MPa (21 bar) (300 psi) is a Type B or Type C with
engineered bellows for the high pressure.
The standard pusher seal elastomer is fluoroelastomer, which is rated at 204 °C (400 °F). A pumping
temperature of 176 °C (350 °F) is realistic for fluoroelastomer, as the face friction will generate additional heat
and raise the temperature the elastomer must endure.
A.2.3.3 From 176 °C (350 °F) to 260 °C (500 °F) and below a gauge pressure of 2,1 MPa (21 bar)
(300 psi)
The standard seal is a Type C stationary non-pusher metal bellows seal using flexible graphite for
secondaries.
ISO 21049:2004(E)
The standard alternative is a Type A standard pusher with special features including an internal circulating
device and perfluoroelastomer, circulating through a Plan 23 closed-loop system in accordance with the flush
selection diagram.
The Type C seal is selected as the standard due to the temperature range, which is generally the range where
coking occurs. The stationary bellows design easily accepts a steam baffle for anti-coking protection, whereas
a rotating bellows does not.
A Type A seal with an internal circulating device and a Plan 23 closed-loop system maintains the product
temperature below the range where coking occurs.
A.2.3.4 From 176 °C (350 °F) to 260 °C (500 °F) and from a gauge pressure of 2,1 MPa (21 bar)
(300 psi) to 4,1 MPa (41 bar) (600 psi)
A totally engineered sealing system is required for hot high pressure services.
A.2.3.5 From 260 °C (500 °F) to 400 °C (750 °F) and below a gauge pressure of 2,1 MPa (21 bar)
(300 psi)
The Type C seal is selected as the standard due to the temperature range, which is generally the range where
coking occurs. The stationary bellows design easily accepts a steam baffle for anti-coking protection, whereas
a rotating bellows does not.
The standard alternative is a totally engineered sealing system.
A.2.3.6 From 260 °C (500 °F) to 400 °C (750 °F) and from a gauge pressure of 2,1 MPa (21 bar)
(300 psi) to 4,1 MPa (41 bar) (600 psi)
The only acceptable alternative is a totally engineered sealing system.
A.2.4 Flashing hydrocarbons [vapour pressure above 0,1 MPa (1 bar) (14,7 psi) at pumping
temperature] — Sheet 5
A.2.4.1 From – 40 °C (– 40 °F) to – 5 °C (20 °F) and a gauge pressure below 4,1 MPa (41 bar) (600 psi)
The standard seal is a Type A standard pusher with special features. The special feature is an NBR
elastomer. Ensure NBR is compatible with the pumped fluid.
The standard alternative is an engineered sealing system with an engineered metal bellows for the flashing
service.
Metal bellows seals in flashing service are prone to fatigue failure, induced by “stick-slip” if marginal vapour
suppression occurs. If metal bellows are desired, the seal should be a totally engineered sealing system with
special attention to vapour suppression under all operating conditions of the pump, such as start-up, shutdown
and plant upsets.
A.2.4.2 From – 5 °C (20 °F) to 176 °C (350 °F) and a gauge pressure below 4,1 MPa (41 bar) (600 psi)
The standard seal is a Type A standard pusher with special features to maintain adequate vapour
suppression. If the temperature is above 60 °C (140 °F), an internal circulating device and Plan 23 closed-loop
system should be considered as an alternative to help reduce flashing at the seal face. If the temperature is
above 176 °C (350 °F), perfluoroelastomer should be used.
The standard alternative is a totally engineered sealing system with an engineered metal bellows.
Vapour suppression by cooling is always preferred over pressurization. Therefore, a Type A seal with internal
circulating device and Plan 23 closed-loop system is selected if the temperature is above 60 °C (140 °F). The
122 © ISO 2004 – All rights reserved
ISO 21049:2004(E)
60 °C (140 °F) limit is based on the cooling-water temperature in the hot months, where little cooling of a
product below 60 °C (140 °F) will occur. Various locations may choose a higher or lower limit based on the
maximum cooling-water temperature in that specific location.
A.2.4.3 From 176 °C (350 °F) to 400 °C (750 °F) and below a gauge pressure of 2,1 MPa (21 bar)
(300 psi)
The standard seal is a Type C seal. The standard alternative is a totally engineered sealing system.
A.2.4.4 Above 176 °C (350 °F) and a gauge pressure from 2,1 MPa (21 bar) (300 psi) to 4,1 MPa
(41 bar) (600 psi)
The seal should be a totally engineered sealing system.
A.3 Tutorial seal selection — Sheet 6
A.3.1 Sheet 6 is intended only as a guide to some of the aspects that might be considered in the selection
of a seal arrangement. The user should evaluate the cost benefits and risk associated with any selection.
A.3.2 Question 1 is whether there are any regulations effective at the site of the equipment which require
specific hardware. This hardware could include low-emission single seal or dual seals. The question is intended
to alert the user so that he can investigate the possibility that specific designs might be required.
A.3.3 Question 2 alerts the user to examine the pumped stream to determine if any owner or operator
standards exist that would dictate or help define the required arrangement from the owner or operator. These
standards might deem the stream hazardous and require specific methods of control or limits of exposure on
emissions, even if local regulations do not. Seal designs shall then employ the required hardware or be
designed to meet the required emission limit.
A.3.4 Question 3 addresses selection of arrangement for acids. If the stream is not acid, question 3 will skip
to question 5.
A.3.5 Question 4 selects the arrangement for an acid stream as either a single seal or a pressurized dual
seal. Unpressurized dual seals are not recommended, due to the potential for build-up of acid in the buffer
system or containment seal chamber.
A.3.6 Question 5 addresses materials which may pose a personnel hazard, such as rich (in H S) amine
streams, to highlight the need for control beyond a single seal without external flush. The highlight is needed
because specifications often overlook the need for added control measures on this type of stream.
A.3.7 Question 6 is similar to question 5, except it addresses streams for which an Arrangement 1 seal will
not meet safety requirements of the owner concerning a potential vapour cloud or fire risk.
A.3.8 Question 7 addresses the need for additional sealing control on those streams which will not meet
local emission requirements wi
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