Flowserve Marathon-Mach 1 - Manual (Page 5)

5
Flow Control Division
Section 1.0
SECTION IV
PRESSURE CONTAINING FASTENERS
MATERIAL SELECTION
Selecting the proper fastener material is the ultimate
responsibility of the customer because the supplier does
not typically know in what service the valves will be used or
what elements may be present in the environment. Flowserve
normally supplies B7 and B7M (carbon steel) for ductile cast
iron and carbon steel valves. For stainless steel and high
alloy valves, B8, Class 2B (stainless steel, Identified as B9)
fasteners are supplied as standard. All fasteners used must
have a minimum yield strength of 65,000 PSI, a minimum
elongation of 12% and be compatible with the process fluid.
Determining compatibility to the process fluid goes beyond
a material being resistant to general corrosion because the
more important consideration is a material’s resistance to
stress corrosion cracking. Depending on the service, it may
make sense to use B7 fasteners on high alloy valves. One
such service would be marine environments because of
stainless steel’s susceptibility to stress corrosion cracking
in chloride environments. Another key aspect of fasteners is
frequent visual inspection. Because of the common practice
of using steel fasteners rather than stainless steel to avoid
chloride stress corrosion cracking, visual inspection is
recommended to monitor the general corrosion of these
fasteners. If jacketing or insulation is used on a valve, it must
be periodically removed for visual inspection of the fasteners.
If you wish assistance in determining the proper fasteners to
use, please refer to the attached chart.
DESIGN & TYPE
Flowserve’s valve design standards adopt ASME B18.2.1
(1996, Addenda 1999) as the standard for fastener type and
design. This national standards requires that finished hex
‘head’ cap screws be used when the head of the fastener is
turned. A finished hex ‘head’ cap screw and a heavy hex cap
screw have a bearing surface under the head to minimize
frictional resistance during tightening. They also comply to
qualified body diameters and fully formed head dimensions.
Cookeville Valve Operation’s policy is to use finished hex
‘head’ and heavy hex ‘head’ cap screws for all pressure
retaining fasteners. This includes top caps, packing adjusters,
plug adjusters, bottom caps, body halves or other pressure
retaining components. Compliance is made with ANSI B18.2.2
(1987, reaffirmed 1993), Square and Hex Nuts, when studs
and heavy hex nuts are required. Additional information on
these items may be obtained from the Flowserve Corporation,
Cookeville Valve Operation, Cookeville, Tennessee.
TABLE I
CAP SCREWS - STUDS
HHCS - Finished Heavy Hex Head Cap Screw Alloy identification stamp required on each piece.
HCS - Finished Hex Head Cap Screw Certification required.
STUD - Stud Alloy Specification (40 KSI Minimum Yield Strength, 12% Minimum Elongation)
Dimensions per ASME B18.2.1
B9 - Stainless Steel per ASTM A193, Class 2B, Grade B8 (AISI type 304)
B16** - Stainless Steel per ASTM A193, 100% hardness tested
B7** - Chromium - Molybdenum Alloy Steel per ASTM A193, Grade B7
B7M - Chromium - Molybdenum Alloy Steel per ASTM A193, Grade B7M, 100% hardness tested
B7MT - Chromium - Molybdenum Alloy Steel per ASTM A193, Grade B7M, 100% hardness tested, Teflon ® coated, Dupont SP11C,
Type B - Color blue or green
C20* - Carpenter C20, CB-3 (UNS NO8020), ASTM B473, 40 KSI Min. Yield Strength, 12% Min. El
HC*- Hastelloy C276 (UNS N10276), ASTM B574
I625* - Inconel 625 (UNS N006625), ASTM B446
I825* - Incoloy 825 (UNS N08825), ASTM B425, 40 KSI Min. Yield Strength, 12% Min. El.
IN* - Inconel 600 (UNS N0660), ASTM B166, 40 KSI Min. Yield Strength, 12% Min. El.
M* - Monel (UNS N04400), ASTM B164, Class A or B, 40 KSI Min. Yield Strength, 12% Min. El.
HB - Hastelloy B (UNS 10665), ASTM B335
I718** - Incoloy 718, AMS 5595B
MKH* - Monel K-500, Cold drawn and aged hardened, QQN-286 and ASTM F468
L7** - Chromium-Molybdenum Alloy Steel per ASTM A320, Grade L7
L7M - Chromium-Molybdenum Alloy Steel per ASTM A320, Grade L7M, 100% hardness tested
L7T** - Chromium-Molybdenum Alloy Steel per ASTM A320, Grade L7, Teflon ® coated, Dupont SP11C, Type B - Color blue or green
L7MT - Chromium-Molybdenum Alloy Steel per ASTM A320, Grade L7M, 100% hardness tested, Teflon ® coated, Dupont SP11C,
Type B - Color blue or green
N200* - Nickel per ASTM B160 (UNS N0220), 40 KSI Min. Yield Strength, 12% Min. El.
B7YC** - Chromium-Molybdenum Alloy Steel per A193, Grade B7, Yellow Zinc Dichromate Plated
* These options should be limited to the 150# valves only.
** 600# valves are limited to these options only.