2. OVERVIEW OF MAINTENANCE
PHILOSOPHY IN SEZ REFINERY
CRUDE COMPLEX, RIL,
JAMNAGARPrepared by:
NIKHIL KUNDNANEY
Pre Final Year
Undergraduate Student
Department of Mechanical Engineering
Atmiya Institute of Technology,
Rajkot
3. PREFACE
To get a practical knowledge is the motto of every student during his
technical study. Teaching in classroom gives fundamental knowledge of
various subjects but industrial training provide visual observation of what
actually is happening practically. Teaching gives important knowledge but
training develops habits. Theory of any subject is important but without
practical knowledge it becomes useless particularly for the technical
students.
The principal objective of this training for me as a mechanical
engineering student was to know what a mechanical engineer needs to
do in the industry.
This training also helped in linking my classroom to the practical world
outside. This industrial training really filled gaps between practical and
theoretical knowledge.
4. ACKNOWLEDGEMENTS
On the successful completion of my training period, I would like to acknowledge
the support and timely help of some of the personalities, who have really helped
me a lot during this period.
First of all I would like to thank Reliance Industries Limited for giving such a
wonderful opportunity and exposure to industrial environment by giving trainings
to engineering students.
I would like to thank my mentor Mr. Hardik Thumar for his technical guidance
throughout my training period.
I would like to thank the other engineers of the plant Mr. Dinesh Patel, Mr. Satish
Oza, Mr. Khemchand Bhoge and Mr. Dwaipayan Banerjee for sharing their
experiences and knowledge which has really helped in solving practical
concepts.
I would also like to thank The HOD and other faculty members of the mechanical
department of our college for encouraging me to go out and explore the industrial
world.
5. ABOUT THE INDUSTRY
Reliance Industries Limited (RIL) is an Indian conglomerate holding
company headquartered in Mumbai, Maharashtra, India. The company
operates in five major segments: exploration and production, refining and
marketing, petrochemicals, retail and telecommunications. RIL is the
second-largest publicly traded company in India by market capitalisation
and is the second largest company in India by revenue after the state-run
Indian Oil Corporation. The company is ranked No. 107 on the Fortune
Global 500 list of the world's biggest corporations, as of 2013. RIL
contributes approximately 14% of India's total exports. The company's
petrochemicals, refining, and oil and gas-related operations form the core
of its business; other divisions of the company include cloth, retail
business, telecommunications and special economic zone (SEZ)
development. In 2012–13, it earned 76% of its revenue from Refining,
19% from Petrochemicals, 2% from Oil & Gas and 3% from Other
segments. In July 2012, RIL informed that it was going to invest US$1
billion over the next few years in its new aerospace division which will
design, develop, manufacture, equipment and components, including
airframe, engine, radars, avionics and accessories for military and civilian
aircraft, helicopters, unmanned airborne vehicles and aerostats.
6. I was placed in the CRUDE DISTILLATION UNIT of the refinery. My mentor made
a schedule for the 15 days period. He decided to give a basic orientation of the
plant.
He and his colleagues gave me the overview of the plant and what the plant does.
They explained me the job of a mechanical engineer there and gave me
knowledge of mechanical components of the plant. They even took me in the field
area and explained all the processes and working of the equipments practically.
All of the engineers shared their knowledge and experiences for my better
understanding of the processes and concepts regarding the equipments.
OVERVIEW OF TRAINING
7. INTRODUCTION TO OIL REFINERY
Oil Refinery is an industry which refines
crude oil into more useful petroleum
products, such as gasoline, diesel fuel,
asphalt base, heating oil, kerosene, and
liquefied petroleum gas by fractional
distillation.
8. CRUDE OIL
On average, crude oils are made up of the
following elements or compounds:
• Carbon – 84%
• Hydrogen – 14%
• Sulfur – 1 to 3%
• Nitrogen - <1%
• Oxygen - <1%
• Metals - <1% (nickel, iron,vanadium, etc.)
• Salts - <1%
9. DISTILLATION OF CRUDE
We can separate the components of crude oil by taking advantage of the
differences in their boiling points. This is done by simply heating up crude
oil, allowing it to vaporize, and then letting the vapor to condense at
different levels of the distillation tower (depending on their boiling points).
This process is called fractional distillation and the products of the
fractional distillation of crude oil is called fractions
A fraction from crude oil can be categorized into two categories:
• Refined Product : A crude oil fraction which contains a lot of individual
hydrocarbons (e.g. gasoline, asphalt, waxes, and lubricants)
• Petrochemical Product: A crude oil fraction which contain one or two
specific hydrocarbons of high purity (e.g. benzene, toluene, and
ethylene).
11. PRODUCTS FROM REFINING
• Petroleum Gas – used for heating, cooking, making
plastics
• Naphtha – an intermediate product used to make gasoline
• Gasoline – motor fuel
• Kerosene – fuel for jet engines and tractors and a starting
material for making other products
• Gas Oil or Diesel – used for diesel fuel and heating oil
and a starting material for making other products
• Lubricating Oil – used for motor oil, grease, other
lubricants
• Heavy Gas or Fuel Oil – used for industrial fuel and a
starting material for making other products
• Residuals – coke, asphalt, tar, waxes, and a starting
material for making other products
12. FLOW PROCESS DIAGRAM OF CRUDE
REFINING IN OIL INDUSTRY
TANK
FORM
HEAT
EXCHANGER
Blended
Crude
DESALTER FLASH DRUM
HEAT
EXCHANGER
CRUDE
HEATER
CRUDE
COLUMN
VACCUM
HEAATER
VACCUM
COLUMN
RESIDUE
CRUDE OIL
OUT
PRODUCTS
OUT
PRODUCTS
VACCUM
RESIDUE
TANK
VACCUM
RESIDUE
14. MAIN COMPONENTS/EQUIPMENTS
OF CRUDE REFINING OIL INDUSTRY
• Desalters
• Atmospheric Distillation Tower
• Vacuum Distillation Tower
• Heat Exchangers, Coolers, and Process Heaters
• Tank Storage
• Heater and Boiler
• Gas and Air Compressor
• Turbines
• Pumps, Piping and Valves
15. • Desalters
Crude oil often contains water, inorganic salts, suspended solids, and
water-soluble trace metals. As a first step in the refining process, to
reduce corrosion, plugging, and fouling of equipment and to prevent
poisoning the catalysts in processing units, these contaminants must be
removed by desalting (dehydration). This is done in desalters.
• Atmospheric Distillation Tower
The first step in the refining process is the separation of crude oil into
various fractions or straight-run cuts by distillation in atmospheric and
vacuum towers. The main fractions or "cuts" obtained have specific
boiling-point ranges and can be classified in order of decreasing volatility
into gases, light distillates, middle distillates, gas oils, and residuum.
• Vacuum Distillation Tower
In order to further distill the residuum or topped crude from the
atmospheric tower at higher temperatures, reduced pressure is required
to prevent thermal cracking. The process takes place in one or more
vacuum distillation towers.
16. • Heat Exchangers, Coolers, and Process Heaters
Process heaters and heat exchangers preheat feedstock in distillation towers
and in refinery processes to reaction temperatures. Heat exchangers use either
steam or hot hydrocarbon transferred from some other section of the process for
heat input. The heaters are usually designed for specific process operations, and
most are of cylindrical vertical or box-type designs. The major portion of heat
provided to process units comes from fired heaters fueled by refinery or natural
gas, distillate, and residual oils. Fired heaters are found on crude and reformer
preheaters, coker heaters, and large-column reboilers.
Heat also may be removed from some processes by air and water exchangers,
fin fans, gas and liquid coolers, and overhead condensers, or by transferring heat
to other systems. The basic mechanical vapour-compression refrigeration
system, which may serve one or more process units, includes an evaporator,
compressor, condenser, controls, and piping. Common coolants are water,
alcohol/water mixtures, or various glycol solutions.
• Tank Storage
Atmospheric storage tanks and pressure storage tanks are used throughout the
refinery for storage of crudes, intermediate hydrocarbons (during the process),
and finished products. Tanks are also provided for fire water, process and
treatment water, acids, additives, and other chemicals. The type, construction,
capacity and location of tanks depends on their use and materials stored.
17. • Heater and Boiler
Steam is generated in main generation plants, and/or at various process units
using heat from flue gas or other sources. Heaters (furnaces) include burners and
a combustion air system, the boiler enclosure in which heat transfer takes place, a
draft or pressure system to remove flue gas from the furnace, soot blowers, and
compressed-air systems that seal openings to prevent the escape of flue gas.
Boilers consist of a number of tubes that carry the water-steam mixture through the
furnace for maximum heat transfer. These tubes run between steam-distribution
drums at the top of the boiler and water-collecting drums at the bottom of the boiler.
Steam flows from the steam drum to the superheater before entering the steam
distribution system.
• Gas and Air Compressor
Both reciprocating and centrifugal compressors are used throughout the refinery for
gas and compressed air. Air compressor systems include compressors, coolers, air
receivers, air dryers, controls, and distribution piping. Blowers are used to provide
air to certain processes. Plant air is provided for the operation of air-powered tools,
catalyst regeneration, process heaters, steam-air decoking, sour-water oxidation,
gasoline sweetening, asphalt blowing, and other uses. Instrument air is provided
for use in pneumatic instruments and controls, air motors and purge connections.
18. • Turbines
Turbines are usually gas- or steam-powered and are typically used to drive
pumps, compressors, blowers, and other refinery process equipment.
Steam enters turbines at high temperatures and pressures, expands
across and drives rotating blades while directed by fixed blades.
• Pumps, Piping and Valves
Centrifugal and positive-displacement (i.e., reciprocating) pumps are used
to move hydrocarbons, process water, fire water, and wastewater through
piping within the refinery. Pumps are driven by electric motors, steam
turbines, or internal combustion engines. The pump type, capacity, and
construction materials depend on the service for which it is used.
Process and utility piping distribute hydrocarbons, steam, water, and other
products throughout the facility. Their size and construction depend on the
type of service, pressure, temperature, and nature of the products. Vent,
drain, and sample connections are provided on piping, as well as
provisions for blanking. Different types of valves are used depending on
their operating purpose. These include gate valves, bypass valves, globe
and ball valves, plug valves, block and bleed valves, and check valves.
Valves can be manually or automatically operated.
19. • STUDY OF PUMPS
• STUDY OF HEAT EXCHANGERS
CONTENTS
20. STUDY OF PUMPS
• What is a PUMP ?
A mechanical device using suction or pressure
to raise or move liquids, compress gases, or
force air into inflatable objects such as tyres.
22. CLASSIFICATION OF PUMPS
On the basis of no. of suction :
• Single Suction
• Double Suction
On the basis of stages of operation :
• Single Stage
• Multi-stage
On the basis of priming action :
• Self-Priming
• Non self-Priming
On the basis of bearing location :
• Overhung Bearing
• In-Between Bearing
23. MOSTLY CENTRIFUGAL PUMP
ARE USED IN REFINERY BUT
ROTARY AND RECIPROCATING
PUMPS ARE ALSO USEFUL IN
VARIOUS APPLICATION.
24. CENTRIFUGAL PUMP
• The centrifugal pump
operates on the
principle of
centrifugal force.
• Centrifugal pumps
are used to transport
fluids by the
conversion of
rotational kinetic
energy to the
hydrodynamic energy
of the fluid flow.
25. COMPONENTS OF CENTRIFUGAL PUMPS
• Suction Nozzle – Main inlet for fluid to flow in the pump.
• Impeller - Attaches to the end of the shaft to impart energy to the
fluid being pumped. Available in open, semi- open and closed
designs.
• Volute Casing - Derives is name from a spiral shaped casing
surrounding the pump impeller. It converts velocity energy to
pressure energy.
• Discharge Nozzle – Min outlet for fluid to flow out of the pump.
• Shaft – Main motion transferring element connected at impeller
and motor rotor.
26. • Seal – Mechanical element to stop the fluid in the impeller to flow
inside through shaft end.
• Bearings - Supports the rotating shaft and allows it to turn with a
minimum amount of friction. Could be either sleeve or anti-friction type
• Oil Rings – Component which gives oil for lubrication of anti-friction
bearing.
• Wear Ring - Wear ring provides an easily and economically renewable
leakage joint between the impeller and the casing. The clearance
between the impeller wear ring and casing wear ring is maintained and
if it becomes too large, the pump efficiency will be lowered causing
heat and vibration problems due to flow recirculation and in the worst
condition can cause the cavitation.
31. IMPORTANT TERMS RELATED TO
CENTRIFUGAL COMPRESSOR
• NPSH
• CAVITATION
• SPECIFIC SPEED
• BEP
32. NET POSITIVE SUCTION HEAD - NPSH
PUSH FLUID TO PUMP
• PRESSURE OVER THE FLUID
• STATIC HEAD OF FLUID ABOVE PUMP
CENTRELINE
• ATMOSPHERIC PRESSURE
• VELOCITY HEAD
PUSH FLUID BACK
• FRICTION LOSS IN PIPING
SYSTEM
• VAPOUR PRESSURE OF
LIQUID
THE AMOUNT OF ENERGY IN THE LIQUID AT THE PUMP CENTRE LINE
NPSH AVAILABLE – SYSTEM CHARACTERISTIC
33. NPSH required – pump characteristic
Energy required to overcome frictional losses from pump
suction to impeller vanes
Determined by NPSH test
Varies with pump design, size
Varies with operating flow
Margin of Safety=NPSH A - NPSH R
NPSHA should be greater than NPSHR
Factors affecting NPSH :-
• Insufficient submergence
• Air entrainment
• Suction piping (dry-pit pumps)
• Hot liquid
34. CAVITATION
When suction head available becomes less than the required
head, the phenomenon of CAVITATION occurs.
When the pressure inside the pump goes below the vapor
pressure of the fluid or when the temp. of the fluid rises, liquid
turns into gaseous phase. These vapor bubbles when proceeds to
high pressure region (tip of impeller vane), they burst out and
gives the vacancy to the liquid in the immediate vicinity of it. All
the liquid gushes out to that vacant space with a very high
velocity and damages the impeller.
Cavitation causes the increased vibrations and violent noise. It
severely damages the impeller and creates increased operation
and maintenance problems.
35. SPECIFIC SPEED & SUCTION SPECIFIC
SPEED
An index relating flow, total head, and rotational speed for
pumps of similar geometry. Specific speed is calculated for
the pump performance at best efficiency points with
maximum impeller diameter. Specific speed is expressed
mathematically by the following equation.
36. BEST EFFICIENCY POINT
Best efficiency point is also known as the “sweet spot”.
Operation at BEP results in lowest operating cost and
longest service life
38. RECIPROCATING PUMP
A reciprocating pump is a
positive plunger pump. It is often
used where relatively small
quantity of liquid is to be handled
and where delivery pressure is
quite large. In reciprocating
pumps, the chamber in which the
liquid is trapped, is a stationary
cylinder that contains piston or
plunger Piston pump, plunger
pumps, and diaphragm pumps
are example of reciprocating
pump.
39. MAIN FEATURES OF RECIPROCATING
PUMP
• Positive displacement of liquid
• High pulsation caused by sinusoidal motion of
the piston
• High volumetric efficiency
• High starting torque
40. ROTARY PUMPS
A rotary vane pump is a positive-displacement pump that
consists of vanes mounted to a rotor that rotates inside
of a cavity. In some cases these vanes can be variable
length and/or tensioned to maintain contact with the
walls as the pump rotates.
Types of rotary pumps-
• Screw
• Gear
• Lobe
• Sliding Vane
41. MAIN FEATURES OF ROTARY PUMP
• Positive displacement
• Self priming
• Fairly constant discharge
• Less vibration
• Weight per unit flow is less compared to recip
type
• Less no. of parts, making it less complicated
52. PUMP MAINTENANCE
Pump maintenance is an activity done to insure
smooth running of pumps for a long period of time
by repairing or replacing damaged equipment
before an obvious problems occur.
Types of pump maintenance :
• Breakdown or Run-to-failure Maintenance
• Preventive or Time-Based Maintenance
• Predictive or Condition-Based Maintenance
• Pro-Active Maintenance
53. BREAKDOWN MAINTENANCE
The basic philosophy behind breakdown maintenance in pumps is
that it :
• Allows machinery to run to failure.
• Repair or replace damaged equipment when obvious problem
occur.
Advantages of breakdown maintenance :
• Breakdown maintenance works well if equipment shutdowns don’t
affect production and if labor and material costs don’t matter.
Disadvantages of breakdown maintenance :
• It is an unplanned maintenance activity.
• It causes unexpected production interruption.
• It requires high parts inventory to react quickly.
• It is the most inefficient maintenance operation.
54. PREVENTIVE MAINTENANCE
Preventive maintenance in pumps is a schedule maintenance activity
at predetermined time interval to ensure smooth running of the same.
It helps to replace or repair damaged equipment before obvious
problems occur.
Advantages of preventive maintenance :
• It works well for equipment that don’t run continuously and
personnel have enough knowledge, skill and time to perform the
preventive maintenance work.
Disadvantages of preventive maintenance :
• It might be possible that the scheduled maintenance may be done
too early or too late.
• Preventive maintenance can also reduce production due to
potentially unnecessary maintenance.
• It increases the possibility of diminished performance through
incorrect repair technique.
55. PREDICTIVE MAINTENANCE
Predictive Maintenance is another type of maintenance for pumps which
is scheduled when mechanical or operational condition of the pump
warrants. Repairing or replacing the damaged equipment is advised
before an obvious problem occurs.
Advantages of predictive maintenance
• This works well if personnel have enough knowledge, skill and time to
perform the predictive maintenance work.
• It also gives some lead time to purchase materials for necessary repair.
Disadvantages of predictive maintenance
• Improper condition assessment may actually increase maintenance
work.
• Requires procurement of equipment and training of in-house personnel.
56. PROACTIVE MAINTENANCE
The basic philosophy behind proactive maintenance is that it utilises
predictive/preventive maintenance techniques with root cause failure
analysis to detect and pinpoint the precise problems, combined with
advanced installation and repair technique, including potential
equipment redesign or modification to avoid or eliminate problems from
occuring.
Advantages of proactive maintenance :
• Repairs to equipment can be scheduled in an orderly fashion and
improvements can be made to reduce or eliminate potential
problems from occuring.
• It also brings substantially increases production capacity.
Disadvantages of proactive maintenance :
• Requires procurement of equipment and training of in-house
personnel or outsourcing this work to a knowledgeable contractor to
perform duties.
57. When PM (Preventive Maintenance) is done a checklist is given to the
contractor to perform the assigned tasks. This checklist consists of the
following points.
• Removal & refitting of coupling guard.
• Check free rotation of pump.
• Check tightness of casting belts.
• Check tightness of foundation bolts.
• Check tightness of thrower grub screw.
• Check tightness of piping support clamp.
• Cleaning of breather.
• Cleaning of strainer in seal flush.
• Check wear, damage, rust, paint visually.
• Check coupling condition of bolts.
• Check oil quantity and replace if required.
• Check gland packing.
• Check sealing oil.
• Check flushing line for choking.
• Check cleaning around pump.
• Check cooling water flow and attend leak.
• Check shaft deflection.
• Alignment with motor/turbine.
58. STUDY OF HEAT
EXCHANGERS
• What is a HEAT EXCHANGER ?
A heat exchanger is a device that is used to transfer thermal energy
(enthalpy) between two or more fluids, between a solid surface and a
fluid, or between solid particulates and a fluid, at different temperatures
and in thermal contact. In heat exchangers, there are usually no external
heat and work interactions.
• Why do we use HEAT EXCHANGER ?
Heat exchangers are used to transfer heat between two fluids.
60. TYPES OF HEAT TRANSFER EQUIPMENT
• COOLER – Cools using water or air, without phase change.
• CHILLER – Refrigerates below that obtainable with water.
• CONDENSER – Condenses vapour/ vapour mixture.
• STEAM HEATER – Uses steam for heating.
• STEAM GENERATOR – Produces steam from water.
• REBOILER – Uses steam/hot fluid to heat, for distillation
column.
64. HEAT EXCHANGERS
Types of shell and tube type heat exchanger most commonly used in
refinery and petrochemicals :
1. U-TUBE Exchanger –
• Tube Expansion independent of other tubes.
• Tubes difficult to clean.
65. 2. FIXED TUBE SHEET EXCHANGER –
• Cheapest and most economical.
72. • The Tubular Exchanger Manufacturers Association, Inc. (TEMA) is trade
association of leading manufacturers of shell and tube heat exchangers,
who have pioneered the research and development of heat exchangers for
over sixty years.
• The TEMA Standards and software have achieved worldwide acceptance
as the authority on shell and tube heat exchanger mechanical design.
• TEMA is a progressive organization with an eye towards the future.
Members are market-aware and actively involved, meeting several times a
year to discuss current trends in design and manufacturing. The internal
organization includes various subdivisions committed to solving technical
problems and improving equipment performance. This cooperative technical
effort creates an extensive network for problem-solving, adding value from
design to fabrication.
TEMA
73. R C B Fundamental Standards -
• Class R – Used for severe requirement of
petroleum related processing applications.
• Class C – Used for moderate requirements
of commercial and process applications.
• Class B – Used for chemical process
service.
TEMA designations for shell and tube heat
exchanger -
• STATIONARY HEAD TYPES – A,B,C,D
• SHELL TYPES – E,F,G,H,J,K
• REAR HEAD TYPES – L,M,N,P,S,T,U
75. FRONT HEAD
• A type
Easy to open for tube side access
Extra tube side joint
• B type
Must break piping connections to open
exchanger
Single tube side joint
• C type
Channel to tube sheet joint eliminated
Bundle integral with front head
• N type
Fixed tube sheet with removable cover
plate
• D type
Special closures for high P applications
76. SHELL TYPE• E type
Most common configuration w/o phase
change
• F type
Counter current flow obtained
• G type
Lower delta-P
• H type
Thermo-syphon reboiler
• J type
Old reboiler designs
• K type
Phase separation
• X type
Lowest delta-P`
77. REAR END
• L type
Same as A-type front head
• M type
Same as B-type front head
• N type
Same as N-type front head
• P&W type
Not normally used
• S type
Floating head with backing ring
• T type
Floating head pull-through shell
• U type
Removable bundle w/o FH
78. TUBE-TO-TUBESHEET JOINTS
Heat exchangers are used to facilitate the process of heat transfer between the
fluids. The shell and tube type heat exchangers are the most widely used for
various industrial cooling applications such as in petrochemical and fertilizer
plants. In such type of construction, the tubes, tube sheet and tube-to-tube sheet
joints are based on principles of both mechanical as well as thermal design.
The tube to tube sheet joint is the most critical joint in a heat exchanger. The
applicable code of construction specifies some of the standard tube to tube sheet
weld joint configurations and various tests to be performed primarily from the
mechanical design considerations.
79. For example,
As per ASME Sec VIII Div-2, following are the design considerations for a
typical tube to tube sheet joint in case of a heat exchanger.
[a] Tubes used in the construction of heat exchangers may be considered to
act as stays which support or contribute to the strength of the tube sheet
[b] Tube to tube sheet joint shall be capable of transferring the applied tube
loads.
[c] The design of tube to tube sheet joint depends on type of joint, degree of
examination, and shear load tests, if performed
In a tube to tube sheet joint, mechanical design is usually based on the shear
strength of the joint and the tube thickness is based on the thermal design.
Hence, tube to tube sheet is a perfect example of trade-off between thermal
and mechanical design principles. However, over and above the
requirements of standard codes, a number of additions factors needs to be
considered while designing tube-to-tube sheet joint for a specific application
including service conditions, manufacturability, access for inspection,
equipment life and ease of repair.
80. Tube To Tube sheet Designs are of three types :
• Expanded
• Seal Welded
• Strength Welded
81. Design P,
bar G
Design T,
O
C
< 41 < 350
Use expansion with grooves.
> 41 < 350
Use expansion with seal weld.
any > 350
Use strength weld and contact expansion ( without grooves ), irrespective of design pressure.
> 50 -
Expansion shall be performed for the entire thickness of the tubesheet. Caution shall be taken
not to expand tubes beyond backface of tubesheets.
Notes :
* Expansion of TTS joints shall be performed after any heat treatment in which the temperature of the joint exceeds 200o
C.
* All strength welds shall have a minimum of two layers.
Reduction ratio of tube thickness shall be …..
* 5-10% for CS, LAS and high alloy tube material.
* 4-8% for copper alloy tube materials.
* Where exchanger contains lethal substances.
* Cyclic service.
* H2 service where hydrogen partial pressure exceeds 6.8 bar.
Conditions
Petrokemya's Specification requirements regarding tube-to-tubesheet joints
In any of the following conditions, TTS joints shall be seal welded as a minimum :
* Where mixing of shell and tube side fluids could possibly cause problems such as explosion or contamination.
Tube-To-Tube Sheet Joint Criteria
82. MATERIALS OF CONSTRUCTION
• SHELL/CHANNEL/SHELL COVER
CS, Alloy steel, corrosion resistant clad steel
• TUBES
CS, Alloy steel, SS, Non-ferrous
• BAFFLES
CS generally
• TUBESHEETS
CS, Alloy steel, corrosion resistant clad steel, Cupronickel, SS
83. HEAT EXCHANGER FAILURES
• What is heat exchanger failure?
Failure to deliver the function which it is intended to
perform brings heat exchanger failure.
• What are the types of HX failures?
Mechanical Failure
Corrosion Failure
Process related Failure
84. VIBRATION
• Tube-to-tubesheet joint leaks
• Baffle hole grooving into tube external surface
• Loosening of gasket boltings
• Wear due to collision of tube-to-tube
VELOCITY
• Erosion of tubes at entry side, internally (tube side)
• Erosion of tubes on outside surface (shell side)
• Erosion of inlet/outlet nozzles
• Erosion at baffle hole-to-tube interface
MECHANICAL FAILURES
85. • Uniform attack, uniform thinning.
• Stress Corrosion Cracking, susceptible material and corroding
environment.
• Pitting-Localised attack in the form of pits, under deposit
corrosion (e.g. low velocity areas)
CORROSION FAILURES
•Fouling-Low velocities
•Gumming/Deposits-Operating conditions
•Thermal Shock-Tube-to-tube sheet joint leaks
•Starvation-Tube failure, if material not compatible
PROCESS RELATED
86. HEAT EXCHANGER FAILURES AND REPAIRS
So, in general heat exchanger failure can be of :
• Tube leak
• Tube to tubesheet joint leak
• Gasket leak (Shell/TS or TS/Channel or Floating head)
• Corroded (thinned down shell/channel/tubesheet)
For the given types of failures the repair can be carried out in the
following ways :
• Maintenance procedures (plugging/welding/expansion)
• Upgradation in metallurgy
• Replacement with existing metallurgy with...
Propose change in operating conditions
Design change
Accept degradation rate (based on economy)
87. FAILURE - Tube leak
REPAIR -
• Cutting of leaky tube for investigation
• Plugging the leaky tube(s)
Common taper-plugs used
J-plug welded
FAILURE - Tube to tubesheet joint leak
REPAIR –
• Roll expanded
Re-rolling, if expansion limits not exceeded
Drilling out old tube, reinserting new tube and expansion
If groove damaged, plug the tube
• Seal-Welded
Grind upto the root
Re-weld using suitable filler wire
Roll expand, leaving 10mm from front of tubesheet
88. FAILURE - Gasket leak
REPAIR –
• Damaged gasket
Proper gasket with standard installation and tightening procedures
• Damaged gasket seating faces
Restore the gasket seating faces with weld-overlay followed by restoring
requisite surface roughness
FAILURE - Corroded Shell/Tubesheet/Channel/Baffles
REPAIR –
• Shell
Overlay (same metallurgy/corrosion resistant) using suitable filler wire
Window cutting and replacement
• Erosion corrosion at tube-to-tubesheet joint
Drill out the tube
Provide J-plug and weld fill-up using suitable electrode.
89. DEGRADATIONS
Degradation is the act of lowering something. In heat
exchangers shell, shell cover, tubes and tubesheets get
degraded due to the following reasons :
• SHELL/SHELL COVER
Hot sulfidation (>270°C, H2S)…..uniform metal loss
NA corrosion (>230°, NA)…..”lake-type” metal loss
Wet H2S/HCl corrosion…..cracking/metal loss/pitting
Steam condensate corrosion…..grooving/pitting
Amine corrosion…..metal loss/cracking
Erosion corrosion due NH4HS and/or solid particles in fluid…..metal loss
Galvanic corrosion at baffle resting locations…..localised attack
CUI due to water seepage…..uniform metal loss/pitting
90. • TUBES
SCC of brass tubes (ammonical environments)…..cracking
Hot sulfidation (>270°C, H2S)…..uniform metal loss
Erosion corrosion at tube ends due NH4HS and/or solid particles in
fluid…..metal loss
Grooving around baffle locations
Steam condensate corrosion…..grooving/pitting
Bulging/warping on exposure to high temperature above design
Fatigue/corrosion fatigue due to pulsating vapours
• TUBESHEET
Galvanic corrosion at pass partition grooves…..localised loss
Hot sulfidation (>270°C, H2S)…..uniform metal loss
Erosion corrosion at tube-to-tubesheet joint…..metal loss
Steam condensate corrosion…..grooving/pitting
De-alloying…..localised/uniform metal loss
91. HEAT EXCHANGER TESTING
Heat exchanger testing is done to check for the integrity of the same.
There are basically two types of test :
• Hydro-test -
Tube side
Shell side
• Pneumatic test -
Generally, not undertaken
Low pressure leak test, as initial leak detection
92. AES type :
•Drop channel cover/rear dome.
•Remove FH cover.
•Install test ring.
•Fill shell side with water. [Shell Side Hydro-test]
•Observe for tube leaks/Shell-tubesheet leaks.
•Install FH cover and channel cover.
•Fill tube side with water. [Tube Side Hydro-test]
•Observe for FH gasket leaks/channel-tubesheet/channel-cover gasket leaks or
tube leaks.
•Install rear dome. Fill shell side with water. [Shell Side Hydro-test]
•Observe for Shell-rear dome gasket leak.
HEAT EXCHANGER TESTING
NOTE :- Pressure condition while testing is generally the max. operating
pressure which varies for every exchanger.
