MIS 024 Solved Guess Paper 2026: Mechanical and Electrical Safety Management (MSCIDS, PGDINDS, PGCINDS)

Hazard identification and criteria for safeguards

Question: (a) Discuss the various aspects that have to be considered for hazard identification and prevention. (b) Enumerate the various criteria for safeguarding.

(a) Hazard identification

There are various kinds of hazards existing in the work place depending upon the machine, movements of the worker, types of clothes the workers wear, working environment causing health hazards etc.

Aspects that have to be looked into (20). Check whether:

1. PPE is needed
2. Machines, pits, holes are guarded
3. Lockout is correct
4. Clothes, jewellery or hair can get caught
5. Sharp edges can injure
6. Interlocking is done properly
7. Eye protection is needed
8. High voltage grounding is needed
9. System turns safe on breakdown
10. Movement is too rapid
11. Worker can be caught in moving parts
12. Worker reaches over moving parts
13. Worker is off-balance
14. Worker is dangerously placed
15. Movements injure hands or feet, or cause strain
16. Worker can be struck by an object
17. Worker can fall to another level
18. Lifting or carrying can injure
19. Dust, chemicals, radiation, heat or noise occur
20. Warning signals are adequate

(b) Criteria for safeguards

1. Prevent contact: The guard must stop hands, arms or any body part from touching dangerous moving parts.
2. Secure: It should not be easy to remove or tamper with. It must be firmly fixed and made of durable material.
3. Protect from falling objects: Nothing should fall into moving parts and fly out like a projectile.
4. Create no new hazards: A guard fails if it creates a new danger of its own.
5. Must not impede the worker: A guard that stops the worker from working comfortably will soon be removed. It must give full visibility of the point of operation.
6. Allow safe lubrication: The machine should be oiled safely without removing the guard.

Conclusion: Hazard identification tells us what can go wrong on a job. A safeguard that meets all six criteria keeps the worker safe without slowing the work.

Risks in MMHE, and fixed vs variable path equipment

Question: (a) Explain the different categories of risks associated with Mechanical Material Handling Equipment (MMHE). (b) Differentiate between fixed path and variable path equipments.

(a) Risk factors in mechanical material handling

Mechanical material handling is the movement of the products or materials or things by using the mechanical equipment's such as trucks, hoists and conveyors etc.

There are four risk factors associated with mechanical material handling:

1. Equipment: Must work within its capacity. Maintain and inspect it regularly. It should follow the planned route and not hit machines or workers. Workers can get trapped in gears, pulleys and belts. Sudden electrical or hydraulic failure can cause a severe accident.
2. Load: Limit the load carried. Mark cautions for flammable, explosive or toxic loads. Fit the load properly so it does not slide down.
3. Workplace: Keep the area spacious. Keep free space so people, machines and moving loads do not collide.
4. Employees: Appoint skilled operators and train them. One mistake can damage the whole unit.

(b) Fixed path and variable path equipments

Broadly material handling equipments can be classified into two categories, namely: Fixed path equipments, Variable path equipments.

Conclusion: MMHE risks come from equipment, load, workplace and employees. Fixed path equipment suits a fixed layout; variable path equipment gives flexibility.

Reliability, MTBF and types of failed systems

Question: (a) Explain reliability and Mean Time Between Failures (MTBF) with suitable examples. (b) What are the different types of failed system? How do you overcome from the failure?

(a) Reliability and MTBF

Reliability is the probability of an item in performing its function in a specified way in a given time period and under specific conditions.

1. Failure rate (λ): The number of failures per unit of operating period (time, events or cycles).
2. Mean Time Between Failures (MTBF): A basic measure of reliability. It is the time passed before a component, assembly or system fails.
3. Formula: For constant failure rate systems, MTBF = 1/λ.
4. Example: If a machine has λ = 0.002 failures per hour, MTBF = 1/0.002 = 500 hours. So it is expected to run about 500 hours between failures.
5. Use in design: No system has nil failure. So failure is measured in MTBF and preventive steps are planned. A high quality switch reduces the chance of failure.

(b) Types of failed systems

Systems are designed to bear failures through redundant (spare) hardware or software:

1. Fail operational: After one failure, a redundant system continues the work. Example: an airplane finishes its mission when one alternator fails.
2. Fail safe: After a failure, the system goes to a safe mode. Example: railway signals turn all lights red; an anaesthesia machine stops the flow.
3. Fail-passive: The system loses its function partly or fully, but can still be controlled manually.

How failure is overcome: fault management techniques

1. Fault avoidance: use reliable parts and interlocks.
2. Fault removal: isolate the faulty part.
3. Fault detection: find faults early.
4. Fault tolerance: built-in redundancy.

Conclusion: Reliability and MTBF measure how long a system works without failure. Fail-safe design and fault management keep people and machines safe.

Earth leakage protective device and earthing

Question: Explain the role of earth leakage protective device and earthing in electrical safety concern. Explain with a schematic diagram.

Earthing/grounding system and earth leakage current

In any electrical installation, an earthing system (or grounding system) connects particular parts of that installation with the Earth's conductive surface mainly for safety and different functional purposes.

Role of earthing

1. Low-resistance path: Grounding makes a low-resistance path to earth. It stops the build-up of dangerous voltage.
2. Clears the fault: If insulation fails, the voltage goes to ground. The fault current blows the fuse or opens the breaker.
3. Earthing system must: (a) keep metal parts at earth potential, (b) keep earth resistance low so protective devices work in time, (c) be strong, rust-proof and tested before use.

Role of the earth leakage protective device

1. What it does: An Earth Leakage Circuit Breaker (ELCB) measures leakage to earth. It compares the current in the phase (live) wire and the neutral (return) wire.
2. How it trips: If the two currents differ, it assumes a fault and trips. It cuts off supply and can prevent electrocution or fire.
3. Regulation 42: Installations with load above 5 kW and exceeding 250 V must have an earth leakage protective device.

The file carries a labelled schematic of an ELCB with equipment earthing alongside this answer.

Conclusion: Earthing gives the fault current a safe path to earth. The ELCB senses the leakage and cuts the supply, so both together protect people from shock.

Safety with circuit breakers, and the Megger test

Question: (a) Write down the various safety points while working with circuit breakers. (b) Write down the safety measures while doing Megger test.

(a) Safety tips for working with circuit breakers

Circuit breakers cut off power when too much current flows. Still, these safety tips must be followed:

1. Switch off all electrical input power: Turn off the main breaker and isolate the panel first.
2. Use personal protective equipment: Wear PPE if there is any arc flash chance.
3. Select a suitable breaker: Match the amperage rating and wiring.
4. Check tools, wire and new parts: Make sure they are not damaged.
5. Be careful of hot parts: The main bus bar may still be live.
6. Inspect before turning on: A licensed technician checks all connections.
7. Perform regular maintenance: Replace old breakers; inspect once a year; trip test every 3 to 5 years.

(b) Megger

Megger is an electrical instrument that is used for testing insulation resistance and machine windings to safeguard all electrical equipment from major damage.

High-voltage systems need 1000 V to 5000 V for this test. The reading is in mega-ohm.

Safety measures while doing a Megger test

1. High-resistance only: Use meggers only for high-resistance work, like insulation checks.
2. Do not touch leads: Never touch the test leads while cranking the handle.
3. De-energise and discharge: Fully de-energise and discharge the circuit before connecting.
4. Disconnect the item: Separate the item from other circuits, if possible.

Conclusion: Isolation, PPE and inspection make breaker work safe. During a megger test, the circuit must be dead and the leads must never be touched.