American Petroleum Institute: Standard 682, 4th Edition Shaft Sealing Systems for Centrifugal and Rotary Pumps
Part 3 - Specifications
Knowledge Series
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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 specifications:
▪ Gland Specifications
▪ Sleeve Specification
▪ Drive Collar/Set Screws Specifications
▪ Seal Chamber Bushing Specifications
▪ 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 Design Specifications
To improve plant safety, equipment reliability, and create a cleaner environment, API 682 specifies minimum expected seal design characteristics:
“All mechanical seals, regardless of type or arrangement, shall be of the cartridge design...” ~API 682, 4th edition, 6.1.1.1
Gland Specifications
Gland (End Plate) : Pressure-retaining component(s) similar to a flange, which connects the stationary assembly of a mechanical seal to the seal chamber. (API-682 Chapter 3.1.42)
▪ The MAWP (Maximum Allowable Working Pressure) of the seal pressure casing shall be equal to or greater than that of the pump pressure casing on which it is installed (6.1.2.8)
▪ Glands shall be fastened with (quantity) 4 attachment studs, and unless specified, shall be provided with holes (not slots) for attachment studs. (6.1.2.8, A)
▪ Studs are to meet (or exceed if necessary) API 610 size requirements
▪ Glands shall make metal to metal contact at the ID and OD of bolt circle
Gland Specifications
▪ All mating joints between the gland plates, seal chambers, and pump casings shall incorporate a confined gasket to prevent blowout. (6.1.2.26)
▪ Glands shall include either an ID or an OD pilot
OD Registered Pilot
ID Registered Pilot
Sleeve Specifications
All mechanical seals, regardless of type or arrangement, shall be of the cartridge design, without hook sleeves. (6.1.1.1)
▪ Shaft to Sleeve fit of F7/h6 in accordance with ISO-286-2, correlating to a clearance of 0.020-0.093 mm [0.0008-0.0037 in] (6.1.3.2)
▪ Sleeve OD and ID shall be concentric within 25 µm [0.001 in]
▪ Sleeves shall be relieved along their bore, leaving locating fit at or near each end. (6.1.3.9)
Sleeve Specifications
▪ Sleeves shall be made of one piece and sealed at one end (6.1.3.1)
▪ Auxiliary sleeves (2-piece sleeve) shall be connected with features such as shoulders, holes to receive dog points or pins, or examples of such clear means so that proper axial positioning of rotating elements is maintained. (6.1.3.10)
Auxiliary Sleeve Connection
Sleeve Specifications
▪ Shaft to sleeve O-Ring secondary sealing shall be located at the impeller end of the sleeve (6.1.3.5)
▪ Shaft to sleeve sealing located at the outboard end of the sleeve (common for flexible graphite) shall be captured between the sleeve and the shaft (6.1.3.6)
Sleeve Specifications
▪ Sleeves shall have a minimum radial thickness of 2.5 mm [0.10 in] at their thinnest section (excluding setting plate grooves outside of the gland)
▪ Minimum Sleeve thickness in the area of component drive set screws are also defined within the standard
Drive Collar/Set Screws Specifications
External part of the seal cartridge that transmits torque to the seal sleeve and prevents axial movement of the seal sleeve relative to the shaft (3.1.25)
▪ “Drive collar set screws shall be of sufficient hardness to securely embed in the shaft. Unless otherwise specified the design shall be suitable for a maximum shaft hardness of 38 HRC (353HB)” (6.1.3.12)
▪ Drive collar set screws shall be of sufficient number and size to ensure that rotational drive and axial positioning are adequate for the service conditions with a holding power sufficient to hold at minimum, 150% of the axial thrust generated by the maximum pressure rating of the seal.
▪ 9 or more set screws require customer approval
Seal Chamber Bushing Specifications
▪ Bushings shall be renewable and designed such that they cannot be forced out by hydraulic pressure (6.1.2.15)
▪ Bushing materials and clearances shall be suitable for the service and approved by the purchaser. (6.1.2.16)
▪ Close clearance seal chamber throat bushings can be used with appropriate piping plans…
▪ To increase or decrease seal chamber pressure;
▪ To isolate the seal chamber fluid; and/or
▪ To control the flow into or out of the seal chamber.
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
