MATERIALS OF CONSTRUCTION Flashcards
T/F: The actual cost of metals and alloys will fluctuate quite widely, depending
on movements in the world metal exchanges
T
The quantity of a material used will depend on ___-which must be taken into account
when comparing material costs
MATERIAL DENSITY
MATERIAL STRENGTH (MAXIMUM ALLOWABLE STRESS)
Has high maximum allowable stress
Austenitic stainless steel
(304 and 316)
Incoloy
How can costs be compared?
Calculating cost rating factor
Materials with relatively high maximum allowable stress can be used more efficiently than carbon steel
Stainless low alloy steels
The relative cost of equipment made from different materials will depend
on the _____, as well as the basic __-__
cost of fabrication
cost of the material
T/F: Unless a particular material requires special fabrication techniques, the
relative cost of the finished equipment will be lower than the relative bare
material cost
T
- If the corrosion rate is uniform, the optimum material can be selected by
calculating the ___________
annual costs
Annual costs will depend on the _____ and ____ of the equipment
predicted life
purchased cost
Predicted life is calculated from the?
corrosion rate
T/F: * It may prove more economic to install a cheaper material with a high
corrosion rate and replace it frequently, rather than select a more
resistant but more expensive material; but this strategy is only
considered for relatively simple equipment with low fabrication costs and
where premature failure would not cause a serious hazard
T
The more expensive, corrosion-resistant, alloys are frequently used as a
_____
cladding on carbon steel.
- If a thick plate is needed for structural strength, as for pressure vessels,
the use of_____ can substantially reduce the cost.
clad materials
t/f: the prevention of the contamination of a process
stream, or a product, by certain metals, or the products of corrosion,
overrides any other considerations when selecting suitable materials
T
slight rusting that mark the textiles
iron staining
In textile processes, what are used in preference to carbon steel?
Stainless steel or aluminum
For equipment handling acetylene, the pure metals, or alloys containing
_____________ must be avoided to prevent the formation of
explosive acetylides.
copper, silver, mercury or gold,
The presence of trace quantities of mercury in a process stream can cause the
catastrophic failure of brass heat-exchanger tubes, from the formation of a
_____. Incidents have occurred where the contamination
has come from unsuspected sources, such as the failure of ______
mercury-copper amalgam
mercury-in-steel
thermometers
there was evidence that the stress corrosion
cracking of a stainless-steel pipe had been caused by zinc contamination from
galvanized wire supporting lagging
Flixborough disaster
Discovery of the vertical crack of Reactor 5
March 27, 1974
Prior to explosion during the Flixborough disaster, what was discovered?
A vertical crack in Reactor 5 was leaking cyclohexane
When does a 20 inch bypass system ruptured that cause a fire to the nearby 8 inch pipe
late afternoon of June 1, 1974
What explosion happened in Flixborough Disaster?
Vapor cloud explosion
how many fatalities has occured in the control room
18
How many days did the fire still burn?
10 days
The _____ rattled the confidence of every
chemical engineer in the country.
shock waves
- In industries such as the ________, the surface finish of the material is as important as the choice
of material, to avoid contamination.
food
pharmaceutical
biochemical
textile
Stainless steel is widely used, and the surfaces, inside and out, are given
a high finish by
abrasive blasting and mechanical polishing
Surface finishing is done in the purpose of?
hygiene
prevent material from adhering
aid cleaning and sterilization
A good surface finish is important in textile fiber processing to prevent ?
fibers snagging
is the most commonly used engineering
material.
Low carbon steel (mild steel)
It is cheap, available in a wide range of standard forms and sizes, and
can be easily worked and welded.
Low carbon steel (mild steel)
has good tensile strength and ductility.
Low carbon steel (mild steel)
are not resistant to corrosion, except in certain
specific environments
Carbon steels and iron
Carbon steels and iron are resistant corrosion in specific environments such as ?
Concentrated sulphuric acid
caustic alkalis
suitable for use with most organic solvents
Carbon steels and iron
Carbon steels and iron are not suitable in ? because traces of corrosion products may cause?
chlorinated solvents
discoloration
is susceptible to stress-corrosion cracking in certain
environments.
Mild steel
T/F: The corrosion resistance of the low alloy steels (<5% of alloying
elements), where the alloying elements are added to improve the
mechanical strength and not for corrosion resistance, is not significantly
different from that of the plain carbon steels
T
have a high resistance to mineral
acids, except hydrofluoric acid.
High silicon irons
High silicon irons have how much silicon?
14-15%
are particularly suitable for use with sulphuric acid at all concentrations and
temperatures
High silicon irons
very brittle
High silicon irons
are the most frequently
used corrosion resistant materials in the
chemical industry
stainless steels
- To impart corrosion resistance to stainless steel, the chromium
content must be above ____,
12%
T/F:The higher the chromium content of stainless steel, the more resistant is the alloy to corrosion in oxidizing conditions
T
is added to improve the corrosion
resistance in non-oxidizing environments
Nickel
Types of Stainless Steels
Ferritic
Austenitic
Martensitic
Ferritic
13-20% Cr, <0.1% C, with no nickel
Austenitic
18-20% Cr, >7% Ni
Martensitic
12-14% Cr, 0.2 to 0.4% C, up to 2% Ni
is the structure desired for corrosion resistance, and it is
these grades that are widely used in the chemical industry.
uniform structure of Austenite (face-centered cubic, with the carbides
in solution)
Commonly used grades of Austenitic stainless steel
304
304L
321
347
316
316L
309
310
the so-called 18/8 stainless steels
304
the most generally used stainless steel.
304
AISI
AMERICAN IRON AND STEEL INSTITUTE
It contains
the minimum Cr and Ni that give a stable austenitic structure.
304
The carbon content is low enough
for heat treatment not to be normally needed with thin sections to prevent weld decay
304
low carbon version of type 304 (<0.03% C) used for thicker welded sections, where
carbide precipitation would occur with type 304.
304L
: a stabilized version of 304
321
What stabilizes type 321
titanium
It has a slightly higher strength than 304L, and is more suitable for hightemperature use
321
Stabilized with Niobium
347
What was added in 316 to improve corrosion resistancein reducing conditions
Molybdenum
examples of reducing conditions in which the addition of molybdenum in type gives corrosion resistance?
dilute sulphuric acid
solutions containing chlorides
a low carbon version of type 316, which should be specified if welding or heat
treatment is liable to cause carbide precipitation in type 316
316L
alloys with a high chromium content, to give greater resistance to oxidation at
high temperatures
309/310
are susceptible to embrittlement due to sigma
phase formation at temperatures above 500°C.
alloys with greater than 25% Cr
is an intermetallic compound, FeCr.
Sigma phase
They have greater strength than the plain carbon steels particularly at elevated temperatures
Austenitic stainless steel
They do not become brittle at low temperatures
Austenitic stainless steel
Thermal conductivity of stainless steel is significantly ____ than that of mild steel
Lower
Thermal conductivity of Stainless steel type 304 at 100°C
16 W/m°C
Thermal conductivity of mild steel @100°C
60 W/m°C
Are non-magnetic in the annealed condition
Austenitic stainless steel
Increasing corrosion resistance order
304
304L
321
316
316L
310
T/F: Higher the alloying content, the better the corrosion resistance over a wide range of conditions strongly oxidizing to reducing but higher cost
T
Problems associated with using stainless steel
Intergranular corrosion (weld decay) and stress corrosion cracking
Stress corrosion cracking in stainless steel is caused by a few ppm of?
Chloride ions
Are used for corrosion resistance when oxidizing conditions exist
Stainless steel
If reducing conditions are likely to occur what will be used?
High nickel alloys
Contains between 29 to 30% nickel and 20% chromium
Super austenitic
Have good resistance to acids and acid chlorides
Super austenitic
They are more expensive than the lower content 300 series, austenitic stainless steels
Super austenitic
Contain high percentages of chromium stainless steel
Duplex and Super duplex
Because their structure is a mixture of the austenitic and ferritic phases
Duplex
They have a better corrosion resistance than the austenitic stainless steels and are less susceptible to stress corrosion cracking
Duplex
Chromium content of duplex stainless steel
20%
Chromium content of super duplex grades
25%
We’re developed for use in aggressive off-shore environments
Super-duplex
Can be readily cast, wrought and machined
Duplex range
The cost of ____ is comparable with 316 steels
Duplex
Super-duplex costs _____ higher than the cost of duplex
50%
Has good mechanical properties and easily worked
Nickel
The pure metal of nickel is not generally used for chemical plant T/F:
T
Main use of nickel
Equipment handling caustic alkalis at temperatures above that at which carbon steel could be used (above 700°C)
Is not subject to corrosion cracking like stainless steel
Nickel
Classic nickel-copper alloy with the metals ratio 2:1
Monel
Most commonly used alloy for chemical plant after stainless steel
Monel
More expensive than stainless steel but is not susceptible to stress-cracking corrosion in chloride solutions
Monel
Can be used to equipment handling alkalis, organic acids and salts and seawater
Monel
76% Ni, 7% Fe, 15% Cr
Inconel
Used primarily for acid resistance at high temperatures
Inconel
Resistant to furnace gases if sulphur free
Inconel
Not suitable for use in sulphiding environments
Inconel
Nickel alloy with higher chromium content (21%) and 25%have better oxidation resistance at higher temperatures
Incoloy
RA-33
Covers a range of nickel, chromium, molybdenum, iron alloys
Hastelloys
Developed for corrosion resistance to strong mineral acids like HCl
Hastelloys
Hastelloys B
65 NI 28 Mo 6 Fe
Hastelloy C
54 NI 17 Mo 15 Cr 5 Fe
Where does copper is used in food industry
Brewing
Relatively soft, very easily worked metal a d is used extensively for small bore pipe and tubes
Copper
Relatively soft, very easily worked metal a d is used extensively for small bore pipe and tubes
Copper
Copper alloyed with zinc
Brass
Copper alloyed with tin
Bronze
Other bronzes
Aluminum Bronze
Silicon Bronze
Attacked by mineral acids except dilute, cold, underrated sulfuric acid
Copper
Resistant to caustic alkalis except ammonia and to many organic acids and salts
Copper
T/F: Brass and bronze have similar corrosion resistance to the pure metal
T
Main use in the chemical industry is for valves, and other fittings, and for heat exchanger tubes and tube-sheet
Copper
Cupro-nickel has how much Cu?
70%
Good resistance to corrosion erosion a d are used for heat exchanger tubes particularly where seawater is the coolant
Cupro-nickel alloys
Has higher resistance to corrosion but lacks mechanical strength than it’s alloys
Pure aluminium
Main structural alloys used
Duralumin or Dural
Dural is aluminium and _ Alloy
Copper
Composition of Dural
4% Cu and 0.5% Mg
Have tensile strength equivalent to mild steel
Dural
T/F: Pure metal can be used as a cladding on during plates to combine corrosion resistance of pure metal and strength of Alloy
T
Corrosion resistance of aluminium is due to the formation of?
Thin oxide film
Suitable for use in strong oxidizing conditions
Aluminium
Attacked by miineral acids and alkalis
Aluminium
Aluminium is suitable for concentration of HNO3 greater than
80%
Widely used in the textile and food industry
Aluminium
Used for storage and distribution of demineralised water
Aluminium
one of the traditional materials of
construction for chemical plant but has now,
due to its price, been largely replaced by
other materials, particularly plastics.
Lead
It is a soft, ductile material, and is mainly
used in the form of sheets (as linings) or pipe
Lead
- It has a good resistance to acids, particularly
sulphuric.
Lead
now used quite widely in the chemical industry, mainly for its
resistance to chloride solutions, including sea water and wet chlorine.
Titanium
rapidly attacked by dry chlorine, but the presence of as low a
concentration of moisture as 0.01% will prevent attack
Titanium
depends for its resistance on the
formation of an oxide film
Titanium
is also used in other halide services, ex. in
liquid phase oxidation processes, such as the
manufacture of terephthalic acid, that use bromide
as catalyst or promoter
Titanium
Alloying titanium with_____significantly improves the corrosion
resistance, particularly to HCl.
palladium (0.15%)
being increasingly used for heat exchangers, for both shell
and tube, and plate exchangers, replacing cupro-nickel for use with sea
water.
Titanium
corrosion resistance of tantalum is similar to that of
glass
Called metallic glass
Tantalum
- It is expensive, about five times the cost of
stainless steel, and is used for special
applications, where glass or a glass lining
would not be suitable.
Tantalum
are used to repair glasslined equipment
Tantalum plugs
used in the nuclear industry, because
of their low neutron absorption cross-section and resistance to hot water
at high pressures.
Zirconium and Zirconium alloys
finding use where resistance to hot
and boiling acids is required: nitric, sulphuric, and particularly
hydrochloric
Zirconium
used for vessels and equipment handling hydrofluoric
acid
Silver linings
for special applications in the food and pharmaceutical
industries where it is vital to avoid contamination of the product.
Silver
rarely used as a material of construction because of its high cost.
Gold
It is highly resistant to attack by dilute nitric acid and hot concentrated
sulphuric acid, but is dissolved by aqua regia (a mixture of concentrated
nitric and sulphuric acids).
Gold
attacked by chlorine and bromine, and
forms an amalgam with mercury
Gold
- It has been used as thin plating on condenser
tubes and other surfaces
Gold
- It has been used as thin plating on condenser
tubes and other surfaces
Gold
has a high resistance to oxidation at high temperature
Platinum
One of its main uses has been in the form of an alloy with copper, in the
manufacture of the spinnerets used in synthetic textile spinning
processes.
Platinum
