KROHNE OPTIMASSSsors User Manual

Corrosion Guide Rev 1.05 Jan 2006
OPTIMASS
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DDIISSCCLLAAIIMMEERR::
KROHNE does not represent or warrant the accuracy of the information included in this guide for end user applications. The data presented is based on published data and field experience. However, only the end-user is aware of the specific chemical makeup of their process and must therefore accept the ultimate responsibility for the suitability of the wetted parts for the process. Responsibility as to suitability and intended use of our instruments rests solely with the end user!
Corrosion & Abrasion Guidelines for Coriolis Meters
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Corrosion Guide Rev 1.05 Jan 2006
Contents:
1 Corrosion of Wetted Parts
1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3
1.2 Material Compatibility . . . . . . . . . . . . . . . . . . . . . . . . .3
1.3 Material Information . . . . . . . . . . . . . . . . . . . . . . . . . .3
1.3.1 What is Stainless Steel? . . . . . . . . . . . . . . . .4
1.4 NACE Information . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
1.5 Galvanic Corrosion with Titanium . . . . . . . . . . . . . . . .4
1.6 Problem Applications . . . . . . . . . . . . . . . . . . . . . . . . . .5
1.7 Using Material Compatibility Tables . . . . . . . . . . . . . .5
2 Abrasion Guidelines
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
2.2 Protecting Flanges with Transition Pieces . . . . . . . . .14
2.3 Managing Fluid Velocity . . . . . . . . . . . . . . . . . . . . . . .14
2.4 Titanium as the standard material . . . . . . . . . . . . . . . .14
2.5 Conditioning the fluid flow . . . . . . . . . . . . . . . . . . . . . .15
2.6 Installation of the Flow Meter . . . . . . . . . . . . . . . . . . .15
2.7 Inclusion of air or gas in the fluid . . . . . . . . . . . . . . . .15
2.8 Consider installing the meter in a by-pass . . . . . . . . .15
2.9 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
3 Environmental Protection
3.1 Housing Specifications . . . . . . . . . . . . . . . . . . . . . . . .16
Corrosion Guide Rev 1.05 Jan 2006
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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. 2 6 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 compo­nents, 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 wet­ted parts (measuring tubes and connections) in the fol­lowing materials:
Oxidising
environment
Tantalum
Chlorides
Titanium
C-276
C-4
Ni-Cr-Mo Alloy
No 20 Alloy (Stainless)
Inconel
316 Stainless
Reducing
environment
Zirconium
Ni-Mo Alloy
C-22
Monel
Monel
304 Stainless
Non Chlorides
Oxidizing
Acids
Increasing
aggressivness
Reducing
Agents
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Corrosion Guide Rev 1.05 Jan 2006
Element Typical Specification
C 0.02 0.030 Max
Mn 0.70 2.0 Max
P 0.025 0.030 Max
S 0.001 0.020 Max
Si 0.40 1.0 Max
Cr 22.4 21.0...23.0
Ni 5.8 4.5...6.5
Mo 3.3 2.5...3.5
N 0.16 0.08...0.2
Fe Balance Balance
Specifications for SS318L
Element Typical Specification
Cr 21.6 20.00...22.5
Mo 13.7 12.5...14.5
W 2.9 2.5...3.5
Fe 4.7 2.0...6.0
Co 1.1 2.5 Max
Mn 0.3 0.5 Max
V 0.13 0.35 Max
Ni Balance Balance
Specifications for Hasteloy C22
Please be aware that 318L is a “shorthand” expression KRONHE have adopted for the material to aid our cus­tomers’ understanding that the material is a low carbon stainless steel of a speciifc composition, in the same way that 316L is used as “shorthand” for UNS S31603.
318L is more expensive to use than 316L, but we need to consider the technical benefits that it brings. 318L has a much higher tensile strength compared to 316L. We use this property in our meter to manage the stress caused by lengthening of the tube under thermal expansion. If we used 316L, the tube would deform well below the +100
0
C maximum we specify for 318L.
The corrosion resistance of 318L is equal to 316L. The standard surface roughness is similar and it can be pol­ished to the same fine surface finish of <0.5 um Ra for hygienic and aseptic applications. 318L is extensively used worldwide, where customers utilise the higher ten­sile strength to reduce wall thickness (and so the cost and weight) of process plant and piping. This means that there should be no reluctance from our customers in accepting this material.
KROHNE is the only company to offer a stainless steel straight tube mass flowmeter.
1.4 NACE Information
National Association of Chemical Engineers (NACE stan­dard MR0175-2000) is a material requirements standard relating to the general problems of Sulphide Stress Cracking (SSC) of metals directed towards sour environ­ments.
1.5 Galvanic Corrosion with Titanium
This can occur when a titanium tube meter is placed in contact with other metals, for instance in a steel pipeline. As titanium is a “noble” metal, the other mate­rial will normally corrode in preference to the titanium.
In the case of stainless steel pipelines, titanium is very close in the galvanic table therefore galvanic corrosion is unlikely to be a problem and no precautions are nec­essary.
If carbon steel pipelines are used, galvanic corrosion of the carbon steel may occur with certain acids. This cor­rosion process causes small amounts of hydrogen gas to be liberated at the wetted metal-to-metal contact area. This hydrogen gas may then cause embrittlement in the titanium. This can be avoided by electrically insu­lating the Optimass from the pipeline using insulating gaskets, bolt sleeves and washers.
Of course the use of an alternative tube material e.g. Hastelloy C-22 will prevent the problem entirely.
1.3.1 What is 318L Stainless steel?
Many customers have asked “what is the 318L stainless steel that you use in the Optimass 7000 single straight tube meter, and why do you use this material instead of 316L”? Measuring instruments are more normally manu­factured with wetted parts from 316L stainless steel, which is a 100% austenic structure steel, with composi­tion 18% .Chrome, 8% Nickel, 2.5% Molybdenum, with the balance Iron.
318L is a 50% austenitic / 50% ferritic structure steel (typically known as "duplex"), with (typical) composition 22% Chrome, 5% Nickel, 3% Molybdenum, with the bal­ance Iron.
This material is defined under the following internation­al codes:
UNS S31803
ASTM A789, A790, A479, A420
DIN 1.4462
Corrosion Guide Rev 1.05 Jan 2006
5
Remember in all cases KROHNE cannot accept responsibility for the final choice of material. The ulti­mate responsibility lies with the end user. We can only advise based on our experience!
Explanation of data tables
1. Key to symbols used
Symbol Meaning
Suitable, with a corrosion rate less than
0.05 mm (0.002”) per year
X Unsuitable, due to higher corrosion rate
nd No data is currently available
1.6 Problem Applications
Hydrochloric acid (HCl):
This acid normally contains fluoride and chloride impu­rities that will promote stress corrosion cracking in all tube materials. This effect will always cause a meter failure even if there is no bulk removal of tube material. For this reason we do not recommend Optimass meters for any HCl application.
Instead look to alternative instrument technologies such as capacitive MID (Capaflux) or variable area flowme­ters (H250 PTFE).
Methanol:
“Pure” methanol (> 98% purity) tends to cause the removal of the protective oxide layer on a titanium measuring tube thus promoting corrosion. Titanium therefore cannot be used. Stainless steel or Hastelloy C-22 are suitable alternatives for these applications.
Methanol with a minimum 2%, or greater, water content does not exhibit this tendency and can be freely used with all tube materials.
Oxygen gas:
There is a risk of ignition where an oxygen rich (> 35% O
2
) gas mixture is used with a titanium measuring
tube.Always offer stainless steel as an alternative.Remember also that the “degreasing” option for wetted parts should also be offered for use with oxy­gen gas applications.
Passivation of meters
A “passivation fluid” is normally composed of a mixture of nitric acid (HNO
3
) and hydrofluoric acid (HF) and is used to ‘passivate’ (clean) stainless steel pipework in high purity systems, typically found in the pharmaceuti­cal industry. The process removes weld discoloration, dirt, grease, metal particles, etc.
The nitric acid has negligible corrosive effect, but hydrofluoric acid is very aggressive even at levels less than 0.5% for all wetted tube materials. It is recom­mended that any meter is removed and replaced with spool pieces during the passivation process. This is due to the relatively thin wall of mass flow meter tubes; the customer’s pipework being relatively thick is toler­ant to a small loss of material.
1.7 Using Material Compatibility Tables.
Identify the chemical to be used either by name or by the Formula.
Check that you know the concentration of the chemical and that it is within the concentrations listed in column
3.
Identify the best material for the application and then check that this is acceptable for the customer.
2. Where a temperature is given, this signifies suit­ability only up to this point (e.g. 212/100 denotes up to 212
o
F or 100oC). Where no temperature is given, this signifies suitability up to the lower of either the boiling point of the product, or the maximum operating temperature of the Optimass flowmeter concerned.
The first temperature given is always in Fahrenheit and the second in Centigrade/Celsius.
3. Always check the relevant technical data sheet for the maximum operating temperature of the meter series and wetted material.
4. For the purposes of corrosion resistance, stain­less steel grades 316L and 318L can be consid­ered as both being the same.
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Corrosion Guide Rev 1.05 Jan 2006
Fluid Chem. Formula Concentration
Stainless Steel
Max
oF/o
C
Hastelloy C-22
Max
oF/o
C
Titanium
Max
oF/o
C
Acetaldehyde CH3CHO 100% 200/93 200/93 300/149
Acetate CH3CO2CH3 100% 400/204 400/204 400/204
Acetic Acid CH3COOH 20% 400/204 300/149 260/127
Acetic Acid CH3COOH 50% 160/71 210/99 260/127
Acetic Acid CH3COOH 80% 160/71 210/99 260/127
Acetic Acid CH3COOH 95% X 200/93 210/99
Acetic Acid CH3COOH 100% X 200/93 200/93
Acetone CH3COCH3 100% 400/204 140/60 200/93
Acetyl Chloride CH3COCI 100% 70/21 99/37 220/105
Acetylene CH2 100% 400/204 220/105 79/26
Adipic Acid (CH2)5(COOH)2 100% 50/10 200/93 428/220
Air
Aluminium Chloride AlCl3 10% X 220/105 200/93
Aluminium Chloride AlCl3 40% X 220/105 X
Aluminium Chloride AlCl3 100% X 158/70 X
Aluminium Fluoride AlCl3 20% X X X
Aluminium Nitrate AlNO3 100% 302/150 X 208/98
Aluminium Sulphate Al2SO4 6.50% X 285/140 220/105
Aluminium Sulphate Al2SO4 40% X 285/140 220/105
Aluminium Sulphate Al2SO4 100% X nd 200/93
Ammonia (anhydrous) dry NH3 always 100% 248/120 248/120 77/25
Ammonia (aqueous) NH3 + water 30% 158/70 158/70 X
Ammonia (aqueous) NH3 + water 50% 86/30 302/150 X
Ammonium Acetate NH4CH3COO 15% 220/105 220/105 77/25
Ammonium Acetate NH4CH3COO 55% 170/77 nd nd
Ammonium Bicarbonate NH4HCO3 50% X nd 212/100
Ammonium Carbonate (NH4)2CO3 50% X X
Ammonium Chlorate (NH4)ClO3 30% nd nd 122/50
Ammonium Chloride NH4Cl 40% X 221/105 221/105
Ammonium Fluoride NH4F 25% X 170/77 nd
Ammonium Hydroxide NH4OH 45% X X 170/77
Ammonium Nitrate NH4NO3 28% 280/137 80/27
Ammonium Oxalate (NH4)C2O4 10% X 75/24 75/24
Ammonium Perchlorate NH4ClO4 20% 170/77 X 285/140
Ammonium Phosphate (NH4)3PO4 10% X 140/60 248/120
Ammonium Phosphate (NH4)3PO4 100% X 140/60 140/60
Ammonium Sulphate (NH4)2SO4 10% X 220/104 248/120
Ammonium Sulphate (NH4)2SO4 100% X X 248/120
Aniline C6H6NH2 100% 509/265 248/120 230/110
Aniline hydro chloride C6H5NH2xHCl 25% X nd 212/100
Aqua Regia HCl / H2SO4 100% X X X
Argon Ar 100%
Barium Carbonate BaCO3 100% X X 77/25
Barium Chloride BaCl2 25% X 158/70 122/50
Barium Hydroxide Ba(OH)2 10% 225/107 225/107 77/25
Barium Nitrate Ba(NO3)2 20% 150/65 X 77/25
Benzene C6H6 100% X X 240/116
Benzoic Acid C6H5COOH 10% X 180/82 248/120
Benzoic Acid C6H5COOH 100% X 180/82 248/120
Benzyl Chloride C7H7Cl 100% X X 140/60
Boric Acid BH3 10% X 320/160 320/160
Boric Acid BH3 100% nd nd 77/25
Bromine Liquid Br 100% X X X
Butyric Acid CH3(CH2)2COOH 100% X 260/127 225/107
Calcium Carbonate CaCO3 100%

Calcium Chloride CaCl2 75% X 221/105 O 221/105
Calcium Chloride CaCl2 100% X 392/200 X
= Compatible
X = Not Compatible nd = No Data Available
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