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Agenda Item: 650-1017
Title: Figure 5-7a - Shell Manhole Flange Flatness and Roughness Tolerance
Date: November 15, 2016
Contact Name: Brandon Rogers
Company: The Mosaic Company
Phone: (225)-806-2079 or (225)-474-9844
E-mail:
Purpose: The purpose of this change is to improve the requirement in the standard calling for a machine finished gasket surface by explicitly detailing this requirement in the main text of the standard and adding a roughness tolerance. In addition, a flange flatness tolerance will be specified. These proposed changes should minimize shell manhole leakage.
Source: Brandon Rogers
Revision: 5
Impact: The business impact of this item is neutral.
Rationale: By moving the machining requirement to the main text of the standard and specifying that the shell manhole flange’s roughness and flatness be achieved to a specified tolerance the standard will be better suited to eliminate manhole leakage and enhance reliability.
Proposal:
Figure 5-7A—Shell Manhole
5.7.5.4 Unless otherwise specified by the owner, shell manhole flanges shall be machine finished, and provide a minimum gasket width of 19 mm (3/4 in.). The gasket facing surface finish for both the cover plate and the flange shall have a roughness value of 3.2 m to 6.3 µm (125 micro in. to 250 micro in.), unless otherwise specified by the purchaser. The gasket faces shall have a flatness tolerance of 0.8mm (1/32 in) maximum deviation from any reference plane. This maximum deviation shall not occur in less than a 20° arc in circular shell manholes or 150 mm (6 inches) for non-circular shell manholes.
The gasket materials shall meet service requirements based on the product stored, maximum design temperature, and fire resistance. Gasket dimensions, when used in conjunction with thin-plate flanges described in Figure 5-7a, have proven effective when used with soft gaskets, such as non-asbestos fiber with suitable binder. When using hard gaskets, such as solid metal, corrugated metal, metal-jacketed, and spiral-wound metal, the gasket dimensions, shell manhole flange, and shell manhole cover shall be designed per API Std. 620, Sections 3.20 5.20 and 3.21 5.21. See 4.9 for additional requirements.
4.9 Gaskets
4.9.1 General
4.9.1.1 Gasket materials shall be specified in Table 3 on the Data Sheet. Unless otherwise specified by the Purchaser, gasket materials shall not contain asbestos.
4.9.1.2 Sheet gaskets shall be continuous. Metal gaskets made continuous by welding are acceptable if the weld is ground flush and finished the same as the unwelded non-welded portion of the gasket. Rope or tape gaskets shall have overlapped ends.