American Petroleum Institute: Standard 682, 4th Edition Shaft Sealing Systems for Centrifugal and Rotary Pumps
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This Fluid Sealing Association Knowledge Series training presentation introduces the American Petroleum Institute: Standard 682, 4th Edition. This is part of a series of presentations of this industry standard. This presentation describes API-682 seal configurations:
Seal Nomenclature
Seal Category
Seal Type
Seal Arrangement
Seal Configuration
▪ This FSA training material is made available for informational purposes only and is made available “AS IS.” It is intended to serve only as a summary of the content of the API-682 standard and not as a substitute for or to replace or supersede the actual language of the API standard.
▪ For the full language of the API-682 standard, please refer to the actual standard and/or refer to API’s website for further information: https://www.api.org/products-and-services/standards. FSA disclaims any and all liability for any injuries or damages to persons or property resulting from reliance upon this informational summary.
Seal Nomenclature
API 682 sets a standard language to define Mechanical Seals
API 682 Mechanical Seal language describes the seals intended use.
Mechanical Seal nomenclature is broken into 4 general sections
▪ Category (API-682 Chapter 4.1.2)
▪ Type (API-682 Chapter 4.1.3)
▪ Arrangement (API-682 Chapter 4.1.4)
▪ Configuration (API-682 Chapter 4.1.5)
Seal Category
Seal Category Defines Equipment Conditions
Category 1 Seal
Intended for use in non-API 610 pump seal chambers, preferably meeting the dimensional requirements of ASME B73.1, and ASME B73.2 seal chamber dimensions and their application is limited to seal chamber temperatures from –40 to 260°C (–40 to 500°F) and gauge pressures up to 2 MPa (20 bar, 300 psi)
Category 2 Seal
Intended for use in seal chambers meeting the chamber envelope dimensional requirements of API 610. Their application is limited to seal chamber temperatures from –40 to 400°C (–40 to 750°F) and gauge pressures up to 4 MPa (40 bar, 600 psi). Seals are designed to meet the requirements of API-682.
Seal Category
Category 3 Seal
Provides the most rigorously tested and documented seal design. They meet the seal chamber envelope requirements of API 610 (or equal). Their application is limited to seal chamber temperatures from –40 to 400°C (–40 to 750°F) and gauge pressures up to 4 MPa (40 bar, 600 psi).
*API 610 - Centrifugal Pumps for Petroleum, Petrochemical and Natural Gas Industries
ASME B73.1 - Specification For Horizontal End Suction Centrifugal Pumps For Chemical Process
ASME B73.2 - Specification For Vertical In-Line Centrifugal Pumps For Chemical Process
Seal Category
Scope of Vendor Qualification Test
Test as category 1 unless all the following have been tested to Category 2 or 3:
A) Core seal components
B) Adaptive hardware
C) Seal type
Test as category 1 unless all the following have been tested to Category 3:
A) Core seal components
B) Adaptive hardware
C) Seal type
D) Configuration faces (1.3.5)
Seal Types
Seal Type Defines Internal Components
Type A Seal – Cartridge pusher seal with multiple springs and elastomeric O-ring secondary seals
Type B Seal – Cartridge metal bellows seal with elastomeric O-ring secondary seals
Type C Seal – Cartridge metal bellows seal with flexible graphite secondary seals
Seal Types
Seal Type A
Balanced, internally-mounted, cartridge design, pusher seal with multiple springs.
Secondary sealing elements are elastomeric O-rings.
Seal Types
Seal Type B
Balanced, internally-mounted, cartridge design, metal bellows seal.
Secondary sealing elements are elastomeric O-rings.
Seal Types
Seal Type C
Balanced, internally-mounted, cartridge design, metal bellows seal.
Secondary sealing elements are flexible graphite.
Seal Types
Balance Requirement
and 6.1.1.7)
(i.e. Hydraulic balance less than 1) Mounting Requirement (4.1.3)
Seal Arrangement
Seal Arrangement Defines Component Set
Arrangement 1 - Seal configurations having one seal per cartridge
Arrangement 2 - Seal configuration having two seals per cartridge assembly, utilizing an externally supplied buffer fluid in the space between the seals at a pressure less than the seal chamber pressure.
Arrangement 3 - Seal configurations having two seals per cartridge assembly, utilizing an externally supplied barrier fluid at a pressure greater than the seal chamber pressure.
Seal Arrangement
Number of Core Seal Components per Cartridge (Annex I)
L (3 US Gal) for shaft diameter 60 mm (2.50”) and smaller; Otherwise, 20 L (5 US Gal) (8.3.6.2.5)
Test Requirements (10.3.2.2) Annex I
Seal Configuration
Face to Face (3.1.32) Dual seal in which both mating rings are mounted between the flexible elements.
Face to Back (3.1.31) Dual seal in which one mating ring is mounted between the two flexible elements and one flexible element is mounted between the two mating rings, and the pump process fluid is on the OD of the inner seal and barrier or buffer fluid is on the ID of the inner seal and OD of the outer seal.
Back to Back (3.1.7) Dual seal in which both flexible elements are mounted between the mating rings, the sealed fluid is on the ID of the inner seal, and the barrier or buffer fluid is on the OD of the inner and outer seal.
Seal Configuration
Face to Back
Back to Back
Face to Face
Further Information
American Petroleum Institute Standard 682
For further information and detail please review the API 682 standards document.
Request a copy of the “API Std 682” from the API Publication
