KROHNE OPTIMASS Sensors Corrosion guidelines EN - Manual (Page 3)

Corrosion Guide Rev 1.05 Jan 2006 3
Oxidizing
Acids
Reducing
Agents
Non Chlorides
Chlorides
304 Stainless
Monel
Ni-Cr-Mo Alloy
C-4
C-276
C-22
Titanium
Ni-Mo Alloy
Zirconium
Tantalum
316 Stainless
Inconel
Monel
No 20 Alloy (Stainless)
Increasing
aggressivness
Oxidising
environment
Reducing
environment
Element Typical Specification
C 0.013 0.035 Max
Mn 1.6 2.0 Max
P 0.028 0.045 Max
S 0.009 0.030 Max
Si 0.38 1.0 Max
Cr 16.84 16.0...18.0
Ni 11.26 10.0...15.0
Mo 2.12 2.0...3.0
Fe Balance Balance
Specifications for SS316L
Element Typical Specification
Al 3.0 2.5...3.5
V 2.5 2.0...3.0
Fe 0.13 0.25 Max
C 0.05 0.08 Max
Ti Balance Balance
Specifications for Titanium Gr9
Stainless Steel
318L
7000 series
All wetted parts: UNS S31803 to
ASTM A789, A790, A479 and A240
(also known as DUPLEX Stainless
Steel SAF2205).
This 318L stainless steel is NACE
approved.
ALL hygienic and aseptic process
connections: 316L UNS 31603 or
equivalent (also NACE approved).
Hastelloy C22
7000 series
All wetted parts: UNS NO6022 to
ASTM B619, B622, B626, B574
and B575
This HC-22 is NACE approved.
Titanium
7000 series
Measuring tube: UNS R56320 to
ASTM B338 titanium grade 9
Flange raised faces: UNS R50400
to ASTM B348 and B265 titanium
grade 2.
Titanium grade 9 is not NACE
approved.
Stainless Steel
316L
3000, 8000 / 9000
series
All wetted parts: 316L UNS 31603
or equivalent.
316L is NACE Approved.
Hastelloy C22
3000, 8000 / 9000
series
All wetted parts: UNS NO6022 to
ASTM B622, B626, B564, B574
and B575.
Hastelloy C22 is NACE approved.
1. Corrosion Of Wetted Parts
1.1 Introduction:
General corrosion guidelines for process vessels,
pipework and parts (such as thermo-wells or MID
flowmeter earthing rings) cannot be applied to Coriolis
mass flowmeters, since they refer to the bulk removal
of material from comparatively thick walled compo-
nents, and they also tend not to address specific
localised corrosion mechanisms.
Greater care must be taken in the case of mass
flowmeters, since the tube wall thicknesses are in the
region of 0.2 … 2mm (depending on meter size), so
the removal of even a small amount of material can
cause a measurement problem or a meter tube
mechanical failure.
Additionally, localised corrosion effects such as pitting
or stress corrosion cracking can occur even without
corrosion of the overall tube. If severe enough, these
effects may cause a meter tube mechanical failure.
For these reasons you will find that many fluids will be
shown as unsuitable in this guide for use with mass
flowmeters when compared to more general corrosion
guidelines.
1.2 Material Compatibility
1.3 Material information
The Optimass meter range can be supplied with wet-
ted parts (measuring tubes and connections) in the fol-
lowing materials: