With regard to flammable liquids explain briefly what is meant by: (i) flash point: (ii) Autoignition temperature: (iii) vapour pressure: flammable limits

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CFPA EUROPE DIPLOMA IN FIRE PREVENTION

Unit 1: Nature and Behaviour of Fire

 

 

Instructions:

Please answer any 5 of the following questions. The number of marks available for each question or part of a question are shown in brackets.

Please send all answers in one document. Do not convert into a PDF or split questions into separate documents.

Suggested bibliography for Unit 1: Nature and Behaviour of Fire

British Standards

BS 4422: Fire – Vocabulary, British Standards Institution.

BS 7671: Requirements for Electrical Installations (The IEE   Wiring Regulations), British Standards Institution.

BS EN 60079-10: Electrical apparatus for explosive gas atmospheres.   Classification of hazardous areas, British Standards Institution.

BS EN 60079-14: Electrical apparatus for explosive gas atmospheres.  Electrical  installations in hazardous areas (other than mines), British Standards Institution.

BS 9999: Code of practice for fire safety in the design, management and use of buildings.

HSE

HSG 51: Storage of flammable liquids in containers, 1998, Health and Safety Executive

Heath and safety booklet HS(G) 140, Safe handling of flammable liquids, Health and Safety Executive.

L138: Dangerous substances and explosive atmospheres regulations 2002, Approved Code of Practice and Guidance, 2013, Health and Safety Executive

Other Publications

  • Library of Fire safety: Volume 2: Fire and Hazardous Materials, FPA
  • RC37 Recommendations for the control of hazards arising from electrical lighting, RISCAuthority
  • Fire  Service  Manual:   Volume  1:   Fire   Service   Technology,   Equipment and  Media, Stationery Office:

-          Physics and Chemistry

  • Fire Service Manual: Volume 2 – Fire Service Operations, Stationery Office:

- Electricity

- Petrochemical Incidents

- Manual of Firemanship: The behaviour of fires – Compartment fires.

  • Many elementary physics and chemistry textbooks may be used as alternatives, or to supplement these publications.

It should be recognised that the answers to all of the questions in this paper are not to be found set out in the above publications. Some answers require the application of basic essential knowledge in a practical environment.

Students are expected to make full use of the reference material listed in the bibliographies and independent research – this will mean making use of the internet and/or good reference libraries. Diploma students receive access to the FPA online library, providing exclusive access to a huge range of FPA publications and guidance documents. However, British Standards are not included in our library and it is the responsibility of the student to find their own means to access these

Questions -

1a. With regard to flammable liquids explain briefly what is meant by: (8 marks)

(i) flash point: 

(ii) Autoignition temperature:

(iii) vapour pressure: flammable limits:

b. Complete the table below and state briefly the relationship between the flash point and auto-ignition temperature of a series of related chemicals, in this example methane, propane, butane and n-pentane. (3 marks)

Name

Chemical formula

Flash point (oC)

Autoignition temperature (oC)

Methane

CH4

 

 

Ethane

C2H6

 

 

Propane

C3H8

 

 

Butane

C4H10

 

 

n-Pentane

C5H12

 

 

you are presented with three identical metal containers of about 5 litres capacity,  each about half full of fuel. The containers have a short neck and are normally closed by a screw cap of about 30mm diameter. The cans contain:

(i) petrol (gasoline, flashpoint -43oC)

(ii) methyl alcohol (methanol, flashpoint 11oC)

(iii) paraffin (kerosine, flashpoint 50oC)

Referring to the vapour pressures of these fuels, explain concisely what would happen if the top was taken off and a lit match was immediately dropped into the headspace of each of the cans. Assume that the ambient temperature, and thus that of the liquids, is 15oC. (9 marks

2a. With regard to combustible solids, define the terms in the table below and indicate the units in which they are normally expressed. (7 marks)

Term

Definition

Units

Density

 

 

Specific heat

 

 

Thermal conductivity

 

 

b. In each case state how a low numerical value for the property would affect the ease with which a solid combustible material can be ignited. (6 marks)

c. Explain briefly the difference between energy and power and state the units in which power is normally expressed. (2 marks)

d. If the fuel consumption of a car, travelling at a steady 60 mph, is 20 mpg what is the power produced by the petrol being burnt in the engine? [Assume that the density of petrol is 0.84 kg/l and the heat of combustion of petrol is 47 302 kJ/kg] (Please show your calculations.) (5 marks)

3a. Briefly explain Ohm’s Law (2 marks)

  1. A 750 Watt electric convector heater is plugged into a 240 Volt power supply. A trolley
  2. passing over the flex from the heater to the plug has caused the insulation to distort and has reduced the resistance between the live and neutral wires to 60 Ohms

(i) What is the rate of heat production (in Watts) at the point where the cable is damaged? (Please show your calculations.) (1 mark)

(ii) The plug fitted to the heater flex carries a l3 amp fuse, is this the correct rating for the appliance? (2 marks)

(iii) Would the correctly rated fuse have `blown` as a result of the fault? (Please show your calculations.) (1 mark

d.  Some large factories have three-phase electrical installations. Explain briefly what you understand by this form of installation and how it might benefit a factory, (4 marks)

e. Electric lighting is often overlooked as a potential source of ignition. List factors that might lead to an electric light becoming a source of ignition. (5 marks)

f. List the problems associated with the use of electric adaptors in the workplace and why their use should be minimised. (5 marks)

4. a.  Explain what is meant by a `flashover` and a `backdraft`? Give a practical example of  the circumstances in which each of these events could occur. (10 marks)      

backdraft is a rapid or explosive burning of superheated gasses in a fire, caused when oxygen rapidly enters an oxygen-depleted environment

b. Describe what is meant by a detonation and a deflagration. (4 marks)

        Detonation: 

Deflagration: Are the following events deflagrations or detonations and what characteristic features would you expect to find following an explosion resulting from:

(i) methane leaking from a domestic gas supply (2 marks)

(ii) leaking propane entering a drainage system (2 marks)

(iii) a terrorist bomb (2 marks)

5.      a What is the inverse square law? Give an example of how it relates to fire safety and outline a factor other than the spread of heat where the inverse square law also  impacts on fire safety in premises. (6 marks)

b.  Illustrate the development of a fire by drawing a curve indicating heat production versus time and label the significant features. Show how the production of heat would be affected in the event of the compartment being protected by a water sprinkler installation. (6 marks)

c.  Explain what is meant by a t2 fire and how the concept is used in fire safety management. (8 marks)

In order to initiate combustion in solid materials it is usually necessary to raise their temperature by means of an external heat source. Under certain conditions, however, some materials may generate the necessary heat internally.

a. What properties must a material have for spontaneous heating to occur under certain conditions? (4 marks)

b.  What is meant by ‘critical size’ in the context of self heating? (4 marks

c. Give two examples of materials that can exhibit self heating. In each case indicate the mechanism that causes the heating and outline the precautions that should be taken  to prevent combustion occurring. (8 marks)d.    What is a pyrophoric material? Give an example and state how pyrophoric action differs from spontaneous heating discussed above. (4 marks)

“All answers should be in the candidate’s own words. Any answers which are or appear to be made up by direct copying from the legislation or guidance documents will not have marks awarded

CFPA EUROPE DIPLOMA IN FIRE PREVENTION

UNIT 1:  NATURE AND BEHAVIOUR OF FIRE

SUGGESTED AIM

to ensure that students have a basic understanding of the chemical and physical  processes relating to the ignition of materials and propagation of fire. The unit also requires students to demonstrate an understanding of various technical terms and phenomena associated with the combustion process.

PROPOSED SPECIFIC OBJECTIVES FOR STUDENTS

  • To demonstrate an understanding of definitions relating to the ignition of flammable liquids and gases and be able to demonstrate this understanding in response to questions concerning the application of their knowledge in a practical scenario.
  • To demonstrate an understanding of the terms associated with the nature of materials and their thermal properties and the implications of these when they are subjected to an ignition source.
  • To recognise how heat is produced by an electrical source and demonstrate an understanding of the principles of fuses in response to a simple practical scenario.
  • To have a basic awareness of single phase and three phase power supplies
  • To show a detailed understanding of how lighting and the misuse of electrical extension leads may lead to an occurrence of fire.
  • To understand the phenomenon of very rapid fire spread by comparing and contrasting flashover and backdraft. Also to recognise the difference between a deflagration and a detonation and demonstrate this by reference to practical scenarios.
  • To demonstrate an understanding of the inverse square law and its application to fire protection installations as well as radiant energy sources.
  • To have a basic understanding of the meaning of a t2 fire and the application of this term by fire engineers.
  • To have a detailed appreciation of self heating, how the phenomenon occurs, the types of materials that may be prone to this effect and how risk of self heating may be minimised.

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