MIS

1. Maintenance of Instruments and Systems Notes
Prepared By-
Shivaji G. Thube
Instrumentation Engineering Department
Government Polytechnic Mumbai 1

2. 1.1 Maintenance- Definition, Need for Instruments/Control Systems Maintenance.
1.2 Types of Maintenance- Corrective Maintenance, Preventive Maintenance, and
Predictive Maintenance.
1.3 Troubleshooting- Definition, Maintenance versus Troubleshooting
1.4 Basic Troubleshooting Techniques- Logical Analysis, Divide and Conquer, Remove and
Conquer, and Built in Diagnostics.
1.5 Maintenance Department Functions
1.6 Job Planning and Scheduling
1.7 Typical Maintenance Work Order System (Maintenance Plan-daily/weekly/fortnightly
/monthly/quarterly/annually).
Course Outcome: CO1 Study of Instrument Maintenance Tools- Identification, Function,
Operation and Safety Precautions ; Teaching Hours : 06 hrs; Marks: 8 (R- 2, U-4, A-2)
Ch1 Introduction to Maintenance and Troubleshooting
2

3. 1.1 Maintenance: Definition (s)
The maintenance covers activities that are intended to keep equipment in satisfactory
working condition, including tests, measurements, replacements, adjustments, and
repairs
▪ Some describe maintenance as “fix what is broken”
▪ It could be calibration or cleaning; operational, predictive, preventive, remedial, or
scheduled maintenance; testing, or tuning, etc.
▪ Tyes of Maintenance:
• Corrective Maintenance
• Preventive Maintenance
• Predictive Maintenance
• Scheduled Maintenance
• Emergency Maintenance
3

4. 1.1 Need for Instruments/Control Systems Maintenance or So, Why Maintenance ??
▪ To keep instrument (equipment)/control system operative
▪ To maximize performance of instruments efficiently and regularly
▪ Prevent break down or failures
▪ Minimize production loss from failures
▪ Increase reliability of the operating systems
▪ To keep operation safe
4

5. 1.2 Types of Maintenance
(1) Corrective Maintenance, also known as reactive maintenance or breakdown
maintenance; What is Corrective Maintenance? - YouTube
(2) Preventive Maintenance
What is preventive maintenance? – YouTube
Instrumentation Services | Yokogawa America
What Is Preventive Maintenance? The Beginner's Guide to Running PMs
(getmaintainx.com)
(3) Predictive Maintenance, or condition-based maintenance
Predictive Maintenance Solutions | Industrial Asset Management (embitel.com)
5

6. 1. Corrective Maintenance (CM) /Reactive Maintenance
• It is the technical activity carried out after a failure has occurred in instruments and its
purpose is to restore instruments to a working condition either by repairing or replacing
them. OR
• Corrective Maintenance is a maintenance activity undertaken to overcome the failure or
damage found during the preventive maintenance period.
OR
• CM is a type of maintenance task or action is usually performed after instrument /
equipment failure. It’s simply considered as all activities that restore failed or broken-
down instruments to its normal working condition. It is reactive in nature. Whenever any
instrument fails, either it is replaced, repaired, or restored to its operability.
Some Examples:
Repairing of damaged pressure gauge, failed flow switch, control valve with leakage issue,
faulty DP transmitter, etc.
6

7. 1. Corrective Maintenance (CM)
Advantages
i. Lower short-term costs in case less critical and cheaper instruments
ii. Minimal planning required
iii. Simpler process
iv. Best solution in some cases
Disadvantages
i. Unpredictability
ii. Paused operations
iii. Equipment not maximized
iv. Higher long-term costs in case highly critical and expensive instruments or due to
unplanned equipment downtime
7

8. 2. Preventive Maintenance (PM)
PM is a type of maintenance task or action that is usually performed before equipment
failure. It’s simply considered as all activities that maintain assets and prevent them from
failure or breakdown. It is preventive in nature.
Typically, experts suggest that you observe the 80/20 rule. That is to say that only 20% of maintenance should constitute
corrective actions, whilst the remaining 80% should be directed towards preventive (proactive) maintenance.
• Preventive Maintenance, which is regular maintenance performed according to defined
schedules, regardless of the condition of instrument (equipment).
• Examples of preventive maintenance actions include periodic overhauls, inspections,
cleaning and lubrication of parts, and
• Physical Instrumentation Checks,
• Control Loop Checks,
• Calibration of Instruments 8

9. 2. Preventive Maintenance (PM)
1.Physical Instrumentation Checks-
All instrumentation should be checked physically. While a packing leak on a valve, a
damaged transmitter, or a damaged membrane on a regulator eventually will show up on a
computer screen somewhere, it is not always a problem that can be pinpointed to physical
damage, or to what device(s) that have the problem.
2.Control Loop Checks
Part of an instrumentation preventive maintenance program is to check process control loop
response. For example, if you set a flow to 22 gpm, the flow should become 22 gpm. In
tests by control loop experts such as Fisher and others, on average, the typical plant has
about 80% of their control loops respond incorrectly.
3.Calibration of Instruments
Instrumentation devices needs to be calibrated from time to time to make sure they show
the right value.The interval is different from different devices, brands and styles. Some
suppliers give up to 5 or 10 years warranty on the device they sell to stay true, others are
less. 9

10. 2. Preventive Maintenance (PM)
Advantages
i. Increased asset lifetime
ii. Decreased downtime
iii. Higher equipment reliability
iv. Lower long-term costs
v. Increased safety of spaces
vi. Happier Customers
Disadvantages
i. Requires more planning
ii. Requires adjusting routines
iii. Not applicable to all assets
iv. May result in unnecessary interventions
v. May require more outsourcing
10

11. 3. Predictive Maintenance (PdM)
The goal of predictive maintenance is to predict when a malfunction will occur.
Predictive Maintenance, or condition-based maintenance, which uses advanced technologies
for constant monitoring of the operating instrument (equipment) and predicting the
occurrence of failures.
PdM uses advanced techniques such as vibration analysis, oil analysis, acoustics, infrared
tests, or thermal imaging.
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12. 3. Examples of Predictive Maintenance (PdM)
1. Predictive maintenance (PdM) through Vibraon analysis
Applications: rotating equipment and machines, such as compressors, water pumps, and engines in industries
2. Predictive maintenance (PdM) through Acoustic analysis
Applications: pipes and plumbing, condensers, vacuum systems, fans, air compressors
3. Predictive maintenance (PdM) through Thermographic analysis and infrared analysis
Applications: electrical connections and systems, heating systems, fluid analysis, discharge patterns, roof
maintenance
4. Predictive maintenance (PdM) through Oil analysis
Applications: turbines, hydraulic and electro-hydraulic systems, evaluate engines, transmissions, gears,lubricant
levels
5. Predictive maintenance (PdM) through Motor circuit analysis
Applications: assess engine degradation, shaft and rotor alignment, insulation, gears, scan for short-circuits
In the future, CPU temperature analysis will be one of the main ways to test the health of robots.
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13. 3. Predictive Maintenance (PdM)
Advantages
i. This maintenance acts in a timely manner, which reduces downtime and increases asset
availability.
ii. As maintenance is scheduled according to needs, it avoids wasting stock and labor in
unnecessary maintenance.
iii. It helps to better control over maintenance budget.
iv. Optimal use of the equipment throughout its life cycle.
Disadvantages
i. The need to invest in specific monitoring equipment, as well as to train personnel makes
the implementation of this maintenance very expensive.
ii. For assets with low criticality, predictive maintenance may not offer great savings over the
alternatives.
iii. It is not suitable for assets with random failure modes or without initial data to predict
malfunctions (in these cases, it is preferable to start with condition-based maintenance and
gradually make the transition). 13

14. Emergency Maintenance (EM)
We should not, however, mistake corrective maintenance with emergency maintenance,
which occurs at different stages of a breakdown.
The corrective maintenance is carried out at a time when certain physical damage or
disturbance in the normal operation of the instrument (equipment) is notorious (i.e. a
functional failure).
While emergency maintenance occurs after total failure of the instrument(equipment),
which requires urgent maintenance (and has generally higher costs).
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15. Corrective Maintenance (CM) vs. Preventive Maintenance (PM)
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Sr. No. Corrective Maintenance Preventive Maintenance
1
CM is performed after instruments/control
systems failure or after anything goes wrong.
PM is performed before instruments/control
systems failure or before anything goes wrong.
2 It is less complex and simple process because it
does not involve any planning to prevent
instruments/control systems from failure.
It is more complex as compared to CM because it
involves planning to prevent instruments/control
systems from failure.
3
It can be more expensive than PM as some
instruments/control systems failure causes
greater damage to system.
It can be expensive but it prevents instruments/
control systems from failure.
4 It can affect overall system as some instruments
/control systems failure can cause greater loss in
production.
It prevents loss in production by reducing
chances of failure occurrence.
5 CM leads to expensive repairs along with
unscheduled repairs.
PM mainly aims to avoid expensive repairs and
corrective actions.
6
It is performed at random intervals as it is only
performed when a failure occurs.
It is performed at regular intervals as asset
maintenance is important and should be checked
regularly to avoid any failure occurrence.

16. Corrective Maintenance (CM) vs. Preventive Maintenance (PM)
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Sr. No. Corrective Maintenance Preventive Maintenance
7
CM generally increases need for
instruments/control systems preventive actions.
PM generally decreases need for corrective
actions.
8
CM overall decreases lifecycle of
instruments/control systems.
PM overall increases life cycle of
instruments/control systems.
9
This process results in loss of production, loss of
product quality, loss of time.
This process leads to increase in production,
increase in product quality, no loss of production
time.
10 It is not better for safety of employees and
working environment as it increases risk of injury.
It is better for safety of employees and working
environment as it reduces risk of injury.
11 Downtime of assets- instruments/control systems
is more in CM.
Downtime of assets- instruments/control
systems is less in PM.
12
It requires a greater number of employees or
technicians to perform CM.
It requires a smaller number of employees or
technicians to perform PM.

17. Preventive Maintenance (PM) vs. Predictive Maintenance (PdM)
17
Sr. No. Preventive Maintenance Predictive Maintenance
1 Preventive maintenance is usually performed
to prevent instruments from unexpected
failures.
Predictive maintenance is usually performed to
predict failures that might occur so that it can be
prevented from occurrence.
2
This maintenance is done on regular basis.
This is not done on regular basis. This
maintenance is performed whenever needed i.e.
whenever any potential failure is identified.
3 One needs to increase downtime of
instruments to carry out maintenance i.e. one
need to stop primary functions of instruments
to carry out maintenance action.
No downtime of machine is required i.e. one
does not need to stop primary functions of
Instruments.
4 In this, maintenance occurs even if potential
failures are not identified.
In this, maintenance occurs only when potential
failures are identified/predicted.
5 It is less complex process and simple than
predictive maintenance.
It is more complex and difficult than preventive
maintenance.
6 This maintenance action is more costly than
predictive maintenance as regular
maintenance requires more investment.
This maintenance action is less costly than
preventive maintenance
7 It is more time consuming because in this type of
maintenance, one need to perform inspection and
maintenance on regular basis.
It is less time consuming as in this type of
maintenance, one need to perform inspection and
maintenance only when required.

18. Maintenance vs. Troubleshooting
As has been previously stated, maintenance is any activity that is intended to keep equipment in satisfactory
working condition, including tests, measurements, replacements, adjustments, and repairs. It could be
cleaning, maintenance (-corrective, predictive & preventive), calibration, testing, tuning, etc.
Troubleshooting is the process used to find the cause of a malfunction or an erroneous problem behavior in
order to repair the malfunction. It can be visual checks for burnt or broken components, or it can be checking
for blown fuses. After troubleshooting locates the malfunctioning component(s), it can be replaced.
Troubleshooting can consist of measuring voltages, currents, resistance, pressures, temperatures, and so on,
or it can be running on-line and off-line diagnostics on digital control systems.
Eliminating the source of the trouble may also be considered part of troubleshooting, but it is usually called
remedial maintenance or repair.
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19. Maintenance vs. Troubleshooting
One of the goals in sound maintenance program is to have “no unscheduled down time.” In
order to meet this goal, a strong troubleshooting program must be done that gets to the
root of a problem quickly and makes corrections that are lasting.
Troubleshooting is defined as a method for finding a problem and correcting the problem.
The following are some specific guidelines for the troubleshooter:
1. The troubleshooter must use clear and logical approach to find the problem
2. The troubleshooter should work as quickly as possible to resolve the problem
3. The troubleshooter must work economically
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20. Troubleshooting Techniques
• Logical Analysis
• Experience
• Guess
• Is/Is not
• Divide and Conquer
• Remove and Conquer
• Built-in Diagnostics

21. 1. Troubleshooting Technique- Logical Analysis
Logical analysis leads to some logical steps in the troubleshooting process:
(i) Verification- Verify the problem
(ii) Identification- Locate and identify cause
(iii) Repair- Take recommended corrective action
(iv) Test- Verify the problem corrected or not
(v) Follow-up- Take recommended follow-up steps
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22. i. Verification
Verification is the first step. It is necessary to be very sure that there really is trouble somewhere. Most
often a trouble call comes in when there is no problem at all or when the equipment is fine but the
process is at fault. A change in performance must be verified and the problem checked out before
anything is done.
ii. Identification
After assuring that something is wrong, it is necessary to identify and locate the cause of the trouble.
This step calls for in-depth knowledge of the plant and thorough familiarity with the process. Generally,
a process of isolation is used to track down the problem.
iii. Repair
The next step in the process of troubleshooting is to repair and fix the problem. The problem should
be corrected as quickly as effectively as possible.
iv. Test
Once the problem has been corrected, it is necessary to test that the trouble has indeed been corrected.
A thorough system check is made to be sure that everything is operating as it should. All interested
personnel should be asked whether the problem has been corrected to their satisfaction.
v. Follow-up
The last step in the process is to follow up. This step might require some long term study. Searching
questions should be asked. What was the cause of the problem? Faulty engineering? Faulty installation?
Operator error? Is some change in the process or equipment needed so that this trouble does not occur
again? Following up also means revisiting the problem at some future dates just to be certain
the problem is really solved.

23. i. VERIFY THE PROBLEM
The first step in troubleshooting is to verify that the problem exists.
To determine whether to proceed with troubleshooting, efficiently gather information from every appropriate
source. One valuable resource is the operator who monitors the system. The operator can provide insight into
the system’s performance.
Another information source is historical data, such as maintenance records and trend charts. Consulting the
system’s control diagrams can offer an explanation of how the system should be operating. In addition, a loop
diagram will indicate instrument power supplies, how instruments are connected, and other pertinent data
about the intended operation of each loop.
An example of a system in which tank level is controlled appears in Figure. The level controller receives
information from the level transmitter, then adjusts the control valve to maintain the tank level set point. One
troubleshooting scenario involves a level that has been dropping gradually, and yet the transmitter and
indicators are accurate. Maintenance records show no previous problem with the system.

24. ii. LOCATE AND IDENTIFY CAUSE
The second step in troubleshooting is to locate and identify the cause of the problem. In order to minimize the
time that the process is upset, it is essential that this step be performed quickly. Begin by identifying a minimum
number of possible causes based on the information gathered when verifying the problem. It saves time to
perform the quickest checks of components first.
One way to do this is to divide the system. Separate the portions that are operating correctly and concentrate
only on the portion containing the problem.
In the system shown in Figure, all components except the control valve are operating properly. To identify why
the control valve is not operating properly, the valve is placed in manual and stroked, and the I to P converter’s
output is checked. In this instance, a plugged filter in the air supply line to the I to P converter is the cause.
iii. TAKE/RECOMMEND CORRECTIVE ACTION
After locating and verifying the problem, the next step is to take or recommend action to correct the problem.
The choice of action will depend on the nature of the problem. In the level control system, replacing the
plugged filter will likely remedy the problem. Corrective actions, whether taken or recommended, should
always comply with facility procedures and guidelines.

25. iv. VERIFY PROBLEM CORRECTED
Checking that the problem has been corrected is the fourth step of the troubleshooting procedure. Not only is
this necessary to verify that the problem was solved, it also verifies that no other causes contributed to the
problem. In the system where the plugged filter was replaced, stroking the valve again and verifying proper
operation ensures the problem has been corrected. Further troubleshooting is necessary if it is determined that
the problem has not been corrected.
v. TAKE/RECOMMENDED FOLLOW-UP STEPS
The final step in troubleshooting is to take or recommend follow-up steps. There are two important elements of
this step. The first is to recommend follow-up steps to prevent the problem from recurring. Replacing filters
regularly is one measure that might be recommended for the level control system example. The other follow-up
step is recording the problem and its correction to facility specifications.

26. 2. Troubleshooting Technique- Divide and Conquer
This method uses experience and training to divide the system into two pieces and check to
see which section is performing correctly and which is not, then doing it again and again until
the problem is solved. Sometimes the choice of location is one of convenience, i.e., where is
it easiest to break into the system? When in doubt, break the system in half.
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27. 3. Troubleshooting Technique- Remove and Conquer
In complex interconnected systems it is sometimes difficult to determine what box is causing
the problem. A method to solve this kind of problem is to remove the boxes one at a time
until the problem goes away. An alternate is to remove all the boxes and add them back one
at a time to determine when the problem comes back.
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28. 4. Troubleshooting Technique- Built-in Diagnostics
Most modern microprocessor-based equipment has built-in diagnostics. They don’t always cover all the real-world
problems one might encounter, but properly used they can be of great benefit. Some of this equipment is user-
programmable. This gives users the opportunity to build in their own diagnostic routines. A little foresight in this area can
greatly improve the maintainability of complex machinery. An example of this might be a PLC with additional diagnostic
programming to provide troubleshooting information about the machine the PLC is controlling. Close-coupled rack-
mounted DOS machines or state language machines can provide considerable flexibility in the programming for machine
diagnostics.
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29. Maintenance Department Functions A maintenance department is expected to perform a wide
range of functions including..
• Planning and repairing equipment/facilities to acceptable standards
• Performing preventive maintenance; more specifically, developing and implementing a regularly scheduled work
program for the purpose of maintaining satisfactory equipment/facility operation as well as preventing major Problems
• Preparing realistic budgets that detail maintenance personnel and material needs
• Managing inventory to ensure that parts/materials necessary to conduct maintenance tasks are readily available
• Keeping records on equipment, services, etc.
• Developing effective approaches to monitor the activities of maintenance staff
• Developing effective techniques for keeping operations personnel, upper-level management, and other concerned
groups aware of maintenance activities
• Training maintenance staff and other concerned individuals to improve their skills and perform effectively
• Reviewing plans for new facilities, installation of new equipment, etc.
• Implementing methods to improve workplace safety and developing safety education-related programs for
maintenance staff
• Developing contract specifications and inspecting work performed by contractors to ensure compliance with
contractual requirements

30. • Conduct tasks related with maintenance and operations team.
• Develop and execute preventative maintenance programs.
• Conduct instrumentation evaluation and troubleshooting for electrical, pneumatic, electronic as well as programmable
logic control (PLC) systems.
• Ensure to commission instrumentation effective following with repair and replacement.
• Conduct test related to functional performance on instrumentation as needed by facility changes.
• Involve in evaluation of instrument performance to identify optimization and enhancement opportunities.
• Ensure conformance with environmental and safety requirements commensurate with executing required instrument
maintenance or replacement activities.
• Maintain and update awareness of modifications to regulatory needs related to conduct of maintenance and
construction of instrument.
• Ensure to interpret and suitably use ISA and CSA codes along with API installation practices and standards.
• Comply with classification and prioritization system for completion of work order.
• Assist planning plus operations staff to identify skills and resource needed to complete planning and reactive work
activities.
• Comply with every approved operation and maintenance procedures.
• Perform with maintenance planners as schedule work load.
• Conduct on-going aseptic maintenance and clean room area.
• Comply with all instructions for job tasks completion.
Maintenance Department Functions

31. JOB PLANNING AND SCHEDULING
• Job planning is an essential element of the effective maintenance management.
• A number of tasks may have to be performed prior to commencement of a maintenance job; for
example, procurement of parts, tools, and materials, coordination an of parts, tools, and
materials, identification of methods and sequencing, coordination with other departments, and
securing safety permits.
• Although the degree of planning required may vary with the craft involved and methods used,
past experience indicates that on average one planner is required for ertery twenty craftpersons.
Strictly speaking, formal planning should cover 100% of maintenance workload but emergency
jobs and small, straightforward work assignments are performed in a less formal environment.
• Thus, in most maintenance arganizations 80 to 85% planning coverage is attainable.
• Maintenance scheduling is as important as job planning.
• Schedule effectiveness is based on the reliability of the planning function.
• For large jobs, in particular those taJUiring multi-craft coordination, serious consideration must be
given to using methods such as Program Evaluation and Review Technique (PERT) and Critical Path
Method (CPM) to assure effective overall control.

33. Maintenance work order
• Corrective maintenance is generally considered non scheduled or emergency
maintenance if it affects the productivity of the plant.
• Emergency maintenance work order is written to document the parts and Labor
hours used and to be added to the history file
• Corrective maintenance can be scheduled maintenance when the device or
system does not affect the productivity of the plant

35. Thank You
&
Questions ?
35