Page 119 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

104 Major Process Equipment Maintenance and Repair

Table 2-2
Thermal lleatment of Shafting After Straightenlng
Thermal
Material lleatment
Type Temperature Tlme
A 479 Type. 410 1100 f 25°F.
class 2
A 276 Type 410 1050 f 25°F.
Condition H
A 434 Class BC 850 f 25 OF. Hold for 1 hour
(4140) per inch of
A 582 Type. 416 1100 f 25 OF. diameter or 2 hours
minimum.
K 500 Mom1 725 + 25°F.
A 4791182 Type XM 19 725 f 25 "E
A 276 Type 3041316 725 f 25°F.
A 564 Type 630 1100*25"F.
17-4 (H1150)

'hrned ground and straightened vertical pump line shaft material is
readily available. However, this shafting may not be straight when re-
ceived due to handling and shipment and should be checked when re-
ceived. The standard material is Type 416 stainless steel, which contains
approximately 12 percent chromium, has good strength and adequate
corrosion resistance for most applications.

Upgrading of Materlals
A generally accepted guide for selection of materials used in centrifu-
gal pumps for process services is contained in API Standard 610, and
reproduced as Tables 2-3A and 2-3B. Minor damage (see Figure 2-30) is
to be expected. However, if excessive corrosion, erosion, wear, or break-
age is observed in a particular pump, the materials of construction should
be reviewed and upgraded to these standards. If unacceptable mainte-
nance costs exist even though the guidelines have been followed, materi-
als should be further upgraded, substituting for example 12 percent
chrome steel for low carbon steel or 18-8 stainless steel for 12 percent
chrome steel to solve corrosion problems. Wear rings can be overlayed
with Stellite or Colmonoy for better wear resistance. Shafts can be up-
graded from Type 416 stainless steel to Type 440 heat treated stainless
steel if more strength is required but corrosion resistance is satisfactory.
If both increased strength and corrosion resistance are needed 17-4 PH,
(Text continued on page 96.)