Page 165 - Machinery Component Maintenance

148 Machinery Component Maintenance and Repair

All piping flanges are designed to take 1/16 in. thick asbestos gaskets.
The 1/16 in. thickness assures sufficient compressibility to accommodate
slight facing irregularities while having a sufficiently high seating load to
prevent blowout. One-sixteenth in. thick asbestos gaskets should always
be used with ANSI B 16.5 flanges unless a specific design check has been
made to verify another thickness.
Spiral-wound and double-jacketed asbestos gasket thickness should
comply with API 601.

Flange Bolt-Up

General Installation and Inspection Procedure

This segment covers recommended procedures relating to the prepara-
tion and inspection of a joint prior to the actual bolt-up. Obviously, high
temperature piping joints in hydrogen-containing streams are less forgiv-
ing than those in more moderate service. Critical flanges are defined as
joints in services in excess of 500°F and in sizes above six in. in diame-
ter:

Identify critical flanges and maintain records. A suitable record form
is attached in Figure 4-3. A suggested identification procedure is to
use the line identification number and proceed in the flow direction
with joints #1, #2, etc.

Prior to Gasket Insertion

Check condition of flange faces for scratches, dirt, scale, and protru-
sions. Wire brush clean as necessary. Deep scratches or dents will
require refacing with a flange facing machine.
Check that flange facing gasket dimension, gasket material and type,
and bolting are per specification. Reject nonspecification situations.
Improper gasket size is a common error.
Check gasket condition. Only new gaskets should be used. Damaged
gaskets (including loose spiral windings) should be rejected. The ID
windings on spiral-wound gaskets should have at least three evenly
spaced spot welds or approximately one spot weld every six in. of
circumference (see API 60 1).
Use a straightedge and check facing flatness. Reject warped flanges.