Unit C Specific

Question 1

Hazardous Area Zoning

Answer 1

 Zone 0
Explosive atmosphere (gas,vapour or mist)
is present continuously or for long periods of time or frequently.
 Zone 1
Explosive atmosphere (gas,vapour or mist)
is likely to occur in normal operation occasionally.
 Zone 2
Explosive atmosphere (gas,vapour or mist)
is not likely to occur or only persists for a short period.
 Zone 20
Explosive Atmosphere (cloud of combustible dust) is present continuously, or for long periods or frequently.
 Zone 21
Explosive atmosphere (cloud of combustible dust) is likely to occur in normal operation occasionally.
 Zone 22
Explosive atmosphere (cloud of combustible dust) is not likely to occur or only persist for a short period.

Question 2

Exothermic reaction

Runaway reaction

Answer 2

Exothermic Reaction
 Accompanied by the evolution of heat.
 Must be carefully controlled & monitored to ensure there is no failure of the cooling or stirring systems.
 Will tend to accelerate as the reaction proceeds unless the rate of cooling is sufficient to prevent a rise in temperature.
Runaway Reaction
 Where reactions involve the release of energy in quantities or at rates too high to be absorbed by the immediate environment of the reacting system the increase in temperature causes a thermal runaway reaction.
 Important factors in preventing such
thermal runaway reactions are control of reaction velocity & temperature within suitable limits. These will include considerations such as:
- Adequate heating & particularly cooling
capacity.
- Proportions of reactants & rates of
addition.
- Use of solvents as diluents & to reduce
viscosity of the reaction medium.
- Adequate agitation & mixing in the
reaction vessel.

Question 3

Intrinsic and flame proof equipment

Answer 3

Types of Equipment
Intrinsically Safe Equipment- design ensures that the energy level is insufficient to produce an incendiary spark.
Flameproof Equipment
 Totally enclosed & the casing must be robust enough to withstand internal explosion without igniting the flammable atmosphere in which the equipment is located.
 Suitable for use in Zone 1 or 2 but unsuitable for Zone 0.

Type 'E' Equipment
	Does not arc, spark or generate temperatures high enough to ignite a flammable atmosphere. 
	Suitable for Zone 2.
Type 'N' Equipment
Non-sparking suitable for Zone 2.

Question 4

Work equipment simple risk hierarchy strategy.

Answer 4

	Use 'hardware' measures such as:
- Suitable guards.
- Protection devices.
- Markings & warning devices.
- System control devices.
- Personal protective equipment.
	Use 'software' measures such as:
- Following safe systems of work.
- Ensuring maintenance is only performed      
   when equipment is shut down.
- Provision of information, instruction & 
  training.

Question 5

 Factors to consider when introducing a

planned preventative maintenance system include:

Answer 5

Failure rate predictions.
- Manufacturers data.
- Down-time of plant during maintenance.
- Information from condition monitoring.
- Equipment needed.
- Training of associated staff.
- Maintenance schedules & frequency.
- Systems for non-routine/breakdown  
  maintenance.
- Systems of work.
- Record keeping/maintenance logs.
Condition Based Maintenance
	Relies on monitoring the condition of safety-critical parts & carrying out maintenance whenever necessary to avoid failure.
	Performed after indicators show that equipment is going to fail or that equipment performance is deteriorating.
Factors to be Considered in Developing a Programme for Safety-Critical Components
	Importance in the process.
	Failure during the production process.
	Machine complexity.
	Relationship with other machines.
	Availability of replacement equipment.
	Identification of critical components.
	Environmental factors.
	Maintenance capability within the company.
	Maintainability within the design of the machine.

Question 6

Competence, Training, Information & Supervision ?
Circumstances When Training is Likely to be Required ?
Groups of People Having Specific Training Needs?

Answer 6

 Competence- the ability to undertake
responsibilies & perform activities to a recognised standard on a regular basis, a combination of skills, experience & knowledge.
 Training- an important component of
establishing competency but is not sufficient on its own.

• Induction- on recruitment.
• Changes to work activities.
• Introduction of new technology & equipment.
• Changes in systems of work.
• Refresher training.

 Supervisors- employees who supervise
or manage the use of work equipment should receive adequate health & safety training in how to use work equipment, the risks associated with such use, & the precautions that need to be taken.

 Young & Vulnerable Persons- require
training & proper supervision because of their relative immaturity & unfamiliarity with the working environment.

Question 7

NDT advantages and disadvantages

Answer 7

TEST ADVANTAGES DISADVANTAGES

DYE
PENETRANT CHEAP & CONVENIENT
SUPERIOR TO VISUAL EXAM.
FOR ALL NON-POROUS MATERAILS

SURFACE DEFECTS ONLY
DEFECTS MUST BE OPEN TO THE SURFACE

ACOUSTIC
CAN BE USED TO STUDY THE FORMATION OF CRACKS DURING A PROCESS & PRECISELY LOCATE THE SOURCE

RELIES ON COMPLEX EQUIPMENT & SKILLED OPERATORS

ULTRASONIC
PRECISE LOCATION OF INTERNAL & EXTERNAL DEFECTS. SIZING OF MANY DEFECTS POSSIBLE

EXPENSIVE EQUIPMENT
DEPENDANT ON A POWER SUPPLY

RADIOGRAPHY
PERMANENT,PICTORIAL,EASILY
INTERPRETED IMAGES OBTAINED.
LOCATES MAJORITY OF INTERNAL DEFECTS.

SAFETY HAZARDS.EXPENSIVE X-RAY SETS. THICKNESS LIMITS(MORE SO WITH X-RAYS) POWER SUPPLY REQUIRED

EDDY CURRENT
RAPID DETECTION OF SURFACE OR SUB-SURFACE FLAWS. CAN MEASURE DEPTH OF SHALLOW FLAWS.

CANNOT OPERATE CLOSE TO OTHER FREE SURFACES E.G THIN SHEET. CANNOT FIND DEEP FLAWS. REQUIRES POWER SOURCE

MAGNETIC PARTICLE
MORE SENSITIVE THAN DYE PENETRANT. CAN ALSO FIND SUB-SURFACE DEFECTS

FERROUS METALS ONLY. CANNOT FIND DEFECTS AT ANY SIGNIFICANT DEPTH. REQUIRES POWER SOURCE

Question 8

3 stages of fork lift truck training

Answer 8

Training of lift truck-operators should include:
 Basic Training- basic skills & knowledge required for safe operation of the type of lift truck & attachments which the driver will use.

 Specific Job Training- knowledge of the workplace, any special requirements of the work to be undertaken which the driver will use.

 Familiarisation Training- on the job where the driver operates the truck using the skills learned, under close supervision & under normal working conditions.

Question 9

Risks/ incidents with MEWP’s

Answer 9

MEWP’s incidents:
 Collapse
 Overturning
 People being thrown from the carrier
 Carrier being trapped against fixed structures
 Collision-pedestrians,overhead cables or nearby vehicles.

These incidents arise from the following primary causes:

	Equipment failure.
	Ground conditions.
	Outiggers (not used or faulty)
	Trapping against a fixed structure.
	Being struck by vehicle.
	Load/unload under power.
	Overloading a carrier.
	Carrier struck by a load.

The risk of falling from a MEWP is from sudden movements caused by:

 Impact
 Ground movement
 Failure of a stability-critical part
 Over-reaching

Question 10

Control Measures- for the use of access & work at height equipment involve:

Answer 10

Control Measures- for the use of access & work at height equipment involve:
 Space & Strength- corresponding to the maximum number of persons & maximum working load.
 Fitting of a suspension or supporting system- to avoid excessive platform movements due to boom flexing that could cause trapping accidents.
 Control system to incorporate emergency stop devices & hold-to-run controls & allow control of movements by workers in the carrier.
 Prevention of tilting- if there is a risk of the occupants falling.
 Trapdoors- securely fastened to the work platform so that no inadvertent opening is possible either downwards or to slide sideways.
 Protective Roof- if there is a risk of falling objects endangering persons occupying the carrier.
 Marked with the maximum number of persons and maximum working load.

Question 11

Portable Electrical Equipment

Conditions & Practices Likely to Lead to Accidents

Answer 11

 Incorrectly made connections.
 Damaged or missing insulation, exposing live conductors.
 Insulation failure, resulting in leakage of currents & live metalwork.
 Servicing equipment without disconnecting supply.
 Misuse of the equipment.
 ‘Unauthorised’ equipment brought into the work environment by employees.

Question 12

Electrical Risks from Important Portable Appliances:

 Portable Generator

Answer 12

A means of providing an alternative when mains supply is not available. When in use:
 keep the generator dry, do not use in rain or wet conditions.
Plug appliances directly into the generator or use a heavy duty, outdoor-rated extension cord.
 Don’t try to power building wiring by plugging generator into a wall outlet- this will bypass some of the built-in circuit protection devices.

Question 13

Electrical Risks from Important Portable Appliances:

Arc Welding

Answer 13

• uses a power supply to create an electric arc between an electrode and the base material to melt the metals at the welding point. When the welding arc is connected:
   Connection between power source and workplace to be as direct as possible.
   Use insulated cables and connection devices of adequate current-carrying capacity.
   Do not use extraneous conductive parts as part of the welding return circuit unless part of the workplace itself 
  Ensure current return clamp as near as possible to the welding arc.

Hazards of Portable-Electric Tools
	Use of unsuitable equipment.
	Use of defective equipment.
	Misuse of equipment.
	Inadequate maintenance.

Question 14

Control Measures

Reducing the Risk of Electric Shock with Portable Equipment:

Answer 14

• Earthing all exposed metal parts.
• Using all insulated casings.
• Using double insulation.
• Using reduced voltage.
• Providing sensitive earth-leakage protection to limit the duration of shock.

Question 15

Portable Appliance Inspection & Test HSG

107 summarises the actions to be taken:

Answer 15

 Have a system of maintenance for
portable (and transportable) equipment.
 Identify the portable electrical
equipment that needs to be maintained & obtain information on where it is to be used & how.
 Decide what to do about ‘unauthorised
equipment’ brought in by employees.
 Provide straightforward training &
information to help employees carry out user checks.
 Set up formal visual inspection system.
 Consider brief written guidance relating
to the visual inspection, what to look for & procedures to follow when faults are found.

Question 16

Safe Methods in Roof Work

Precautions During Work on Fragile Roofs

Answer 16

 Fragile roof: any roofing structure not specifically designed to carry loads or without the strength to carry loads other than those produced by the weather. Cement, asbestos, glass, reinforced plastics & light-tongued & grooved wood covered with roofing felt are all materials which have collapsed under the weight of a worker.

 Use roof ladders (crawler boards) to distribute the load of the worker over a wide area & so enable the structure to sustain the load safely.
Precautions During Work on Flat Roofs
Flat roof- less than 10 degrees pitch, erect guard rails & toe boards.
Precautions During Work on Sloping Roofs
Sloping roof- pitch greater than 10 degree
 Roof edge barriers.
 Special working platforms.
 Roof ladders.
Means of Temporary Access
Cradles
 Use- where it is impracticable or uneconomic to provide scaffolding & where maintenance work, such as cleaning or light repairs, is necessary on tall buildings or structures.
 Safety Features
Hinged Suspended Platforms
 Counterweight firmly attached to the outrigger.

Question 17

Designing Surfaces To Reduce Slipping

Answer 17

 Floors & traffic routes should be of sound construction & adequate strength.
 Floors should not be overloaded.
 Surfaces of floors & traffic routes should be free from holes, slopes or slippery materials.
 Holes, bumps or uneven areas should be made good.
 Slopes should not be steeper than necessary.
 Surfaces of floors/traffic routes which are likely to get wet or be subject to spillages should be of a type which does not become unduly slippery or coated with a slip-resistant material.
 Floors near machinery should be slip-resistant & kept free from slippery substances or loose materials.
Arrangements made to minimise risks from snow & ice.
 Floors & traffic routes should be kept free of obstructions.
 Effective drainage provided where a floor is liable to get wet.

Question 18

Precautions & Safe Working procedures for Lone Working

Answer 18

The precautions & safe working procedures will depend on the work activity, lone workers should not be put at more risk than other employees.
Precautions should take account of:
 Normal work.
 Foreseeable emergencies, such as fire, equipment failure, illness & accidents.
Employers should identify situations where people work alone & ensure that controls are in place if there is a need for a single worker to:
 Handle temporary access equipment, such as portable ladders or trestles.
 Handle machinery & goods.
 Lift objects too large for one person.
 Operate essential controls for the safe running of equipment or workplace.
 Work in a situation where there is a risk of violence.
Particular Problems Facing Lone Workers
 Medical Conditions
Employers need to:
- Check that lone workers have no medical conditions that may make them unsuitable for working alone.
- Consider both:
- Routine
- Foreseeable emergencies.