Hot Work

  

Hot Work 
Any activity that involves open flame, spark or heat is known as hot work.  

Fire Triangle: 

Fire is a chemical chain reaction between Heat, Oxygen and Fuel (HOF)  

Hazards of Hot Work: 
1. Fire and Explosion 

2. Welding fumes and dusts 

3. Skin and eye burn from the sparks or flame 

4. Heat stress specially in summer season 
5. Infrared or UV radiation from the welding arc 
6. Electrocution  
7. Flying particles 
8. Trip over trailing cables 
9. Physical injury from grinders and other tools 

Controls of Hot Work: 

Documents: 
1. Permit to work 

2. Method statement and TRA 
3. Welding machine third party certified 
4. Welder and fire watcher should be 3rd Party Certified 

Area: 

5. Remove all the combustibles and heavy oil deposits from the area and contain the sparks with fire blanket -8 meters.
6. All the valves, drains and canals where possible flammables should be covered - 15m radius.

7. Frequent Gas testing should be done - 15m radius.
8. Barricade the area and put signage 
9. Wet the area with water and pressurized fire water hose should be kept near the hot work area.  
10. Certified and valid fire extinguisher should be there 

Equipment: 
11. Welding machine should be 3rd party certified 

12. GFCI or ELCB should be there 

13. Grounding of the welding machine 25
14. All cables must be properly double insulated 

People: 

16. Welder should wear fire resistant leader PPEs (hand gloves, Apron), face shield 
17. Clean the area after job done 
15. Fire watcher must be present  

Welding Machine Inspection: 

1. Grounding/Earthling 
2. TPC (third party certificate)  
3. ELCB (Earth Leakage Circuit Breaker)  
4. Emergency STOP Button 
5. Drip Tray 
6. Spark arrester (Atec standard- 1 year  validity)  
7. Fire extinguisher 

What is the difference between flammable and combustible substances? 

According to NFPA 30 Classification of flammable and combustible substances: 

•  Flammable - Substances which have a flash point less than 100.0 °F are called flammable. 
•  Combustible - Whereas fuels having a flash point above that temperature are called combustible. 

What are the contents of Welding Fumes? 

Welding fumes consist number of hazardous gases such as: 

•  Nitrous Oxide (Oxides of Nitrogen, NOx). 
•  Carbon dioxide (CO2). 
•  Carbon monoxide (CO). 
•  Shielding gas (e.g., Argon gas used in welding). 
•  Ozone (O3). 
•  Note-   Stainless steel fume is more hazardous than Carbon steel fume due to higher chromium and nickel contents.

Safe Use & Storage of Gas Cylinders: 

1. Pressure regulators that filters the gas and provide constant delivery pressure should incorporate safety diaphragm that burst before bonnet is blown off. (in accordance with BS 5741: 1979) 
2. Pressure gauges with safety backs which reflect bursting should be used. 
3. Gas cylinders shall be color coded in accordance with the content and as per the international color code system such as BS 349 and 1319. 

Oxygen O2 Black 

Propane - Red 

4. Standard hose (BS 5120) that is used to connect torch to gas cylinder shall be kept as short as possible. 
5. Hose shall be in good working condition and should be color coded 

•  Oxygen - Blue 
•  Acetylene - Red 
•  Propane - Orange 

6. Hose check valve (non-return valves), which allows gases to blowpipe but notback from it, shall be fitted to each hose atthe torch.  

7. Flash back arrester (restricts the back flow of gases into the equipment or supply line and stops the flame) must be installed in both oxygen and fuel gas lines.
8. Storage compounds should have 2 means of exit and storage area should be properly  ventilated. 
9. Cut-off valve shall also be incorporated for automatically shutting of the gas supply.
10.  Store cylinders at cool well ventilated and dry area away from the combustibles.
11. Segregate empty and full cylinders 
12. Store cylinders at designated area  
13. with chains 
14. Store cylinders upright with valve outlet seals and valve protection caps 
15. Use cylinder cage and cradle to lift a cylinder 
16. Proper hand truck or cart must be used to move cylinders. 
17. Do not drag the cylinders.  

•  Store cylinders at least 30m from hot work location and combustible materials in a dry, ventilated place.

•  Keep oxygen cylinders at least 20 feet from fuel gas cylinders.  

Flashback Arrestor: 

A flashback arrestor is a special gas safety device most commonly used oxy-fuel welding and cutting to stop the flame or reverse flow of gas back up into the equipment or supply line and it prevents the user and equipment from damage or explosions. 

•     There are two types of flashback arrester
•     Wet flashback arrestor  
•     Dry flashback arrestor 
• Flashbacks are commonly caused by a reverse flow of oxygen into the fuel gas hose (or fuel into the oxygenhose), producing an explosive mixture within the hose. The flame can then burn back through the torch,into the hose and may even reach the regulator and the cylinder. Flashbacks can result in damage or destruction of equipment, and could even cause the cylinder to explode. 

Chalwyn Valve: 

Operating diesel engines in hazardous environments is a serious safety risk. A release of flammable gas or hydrocarbon vapor can occur at any time and be drawn into the engine's air intake. The most effective way of shutting down a runaway diesel engine is with an automatic air intake shutoff valve.

Spark Arrestor: 

A spark arrester is a device which prevents the emission of flammable debris from combustion sources, such as internal combustion engines, fireplaces, and wood burning stoves. Spark arresters play a critical role in the prevention of wild land fire and ignition of explosive atmospheres. 

Principle Causes of the Spread of Fire or Transmission of Fire: 

•  Conduction: The movement of heat through material. 
•  Convection: The movement of hotter gases up through the air. 
•  Radiation: Transfer of heat through the sun glows. 
•  Direct burn: Combustible material is contact with naked flame. 

Methods for extinguishing the fire: 

There are three main methods to extinguish a fire. These involves removing one of the essential elements of (Fire fuel, Heat and Oxygen):

1. Cooling - removal of Heat (by water generally for class A fire) 
2. Smothering - removal of Oxygen (by using CO2 or DCP) 
3. Starvation - removal of Fuel (by cutting fuel supply) 

PASS method 

PASS is the acronym for Pull the safety pin, Aim nozzle at base of the fire, Squeeze the lever and Sweep side to side. 

Types of Fire: 

•  Class A: Ordinary combustible fire (E.g. Wood, paper, cloth etc.)  
•  Class B: Liquid or liquefiable solids (E.g. Petrol, diesel, kerosene etc.).  
•  Class C: Gaseous fire {E.g. LPG (liquefied petroleum gas), H2S, NG (Natural gas)}. 
•  Class D: Metal fire (E.g. Magnesium, potassium, Zirconium, Titanium, Phosphorous). 
•  Class E: Electrical Fire: Fire involving energized electrical equipment as electrical cable electric motor etc. 

Firefighting Equipment Inspection: 

1. All personal shall know the location of firefighting equipment in their work / camp areas; 
2. Access to firefighting equipment must never be blocked by any material or equipment;
3. All firefighting equipment shall be inspected monthly to ensure it is in place.(Portable Fire Extinguishers), Pressure gauges show adequate pressure (a CO2 extinguisher must be weighed to determine whether leakage has occurred.
4. Pins and seals are in place.  
5. No visual signs of damage.  
6. Fire extinguishers and hoses are to be ready and available in the location of any hot work. 
7. Never use water on fixtures that contain live electrical outlets, such as an electrical breaker panel. 

What is fire extinguisher, its types and application of each, and color coding for different fire 
extinguisher? 
A portable device that discharges a jet of water, foam, gas, or other material to extinguish a fire is called fire extinguisher.

Types of fire extinguishers and their application: 

• Water type extinguisher – Water fire extinguishers have a class A rating and are suitable for fighting fires involving solid combustibles such as wood, paper and textiles.

• AFFF Foam type extinguisher – AFFF (aqueous film forming foam) foam fire extinguishers are highly effective on class A and class B fires (the foam agent helps to prevent re-ignition). Some foam have been dielectrically tested to 35000 Volt (35kV) and can be used on or near electrical appliances.

•  Carbon dioxide (CO2) type extinguisher – They are ideal for electrical fires, as CO2 is not a conductor and they do not leave behind any harmful residue.

•  ABC Dry chemical powder type extinguisher – ABC powder fire extinguishers are extremely versatile and can be used on class A, class B, class C and electrical fires.

•  Water mist type extinguisher – They are highly effective on class A, B, C, F and electrical. 

•  Wet chemical type extinguisher – Wet chemical fire extinguishers are designed specifically for use on class F kitchen fire.

Color Coding for Fire Extinguishers: 

• Water type              Red 

• AFFF Foam             Cream 

• Carbon dioxide      Black 

• ABC Powder           Blue 

• Water mist             White 

• Wet Chemical        Yellow 

Types of firefighting Equipment: 

1. Portable first aid & firefighting appliances. 

2. Fixed installation. 
3. Mobile equipment 

What are four legs of fire safety? 

1. Fire protection 
2. Fire prevention 
3. Quantity control 
4. Preventive Maintenance 

Fire prevention System 
Fire prevention is about taking steps to prevent a fire from happening. For example regular inspection, provision of booths for hot work,housekeeping, properly storing materials etc.

Fire Protection System 
Fire protection is the combination of different fire safety equipment and procedures that are used to control the fire and to protect the people and property. Fire protection often includes equipment like fire alarms, extinguishers and fire sprinkler system.

What is smoke detector? 
Smoke detector: A smoke detector is a device that senses smoke, typically as an indicator of fire. 

Types: 

•  Ionization smoke detector – ionization smoke detector uses a radio isotope,  typically americium-241 (an alpha emitter)to ionize air. A difference is detected in  ionizing process due to smoke and an alarm is generated. 

•  Photoelectric or optical smoke detector –   It contains a source of infrared, visible, or ultraviolet light (typically incandescent light bulb or LED), a lens, and a photoelectric receiver (typically a photodiode). The light emitted by the light source passes through the air being tested and reaches the photo sensor. They receives light intensity will be reduced because light is scattered due to smoke particles. The circuit detects the intensity reduction and generates the alarm. 

•  Carbon monoxide and carbon dioxide detection – fire produces carbon monoxide and carbon dioxide, and they can be detected through these detection systems. They are particularly suitable for dusty and dirty A fire sprinkler system is an active fire protection method that consists pressurized water supply through piping distribution and provides water flow through the sprinkler heads when fire is detected. 

Sprinkler Head 
Sprinkler head is a component of the fire sprinkler system that discharges water when fire is detected or temperature of that location exceeds the predetermined level. It has color-coded heat sensitive glass bulb filled with mixture of alcohol and water or glycerin and water) that works as a plug which prevents water from flowing. The

color of the bulb indicates the activation temperature. When temperature around the sprinkler head exceeds the activation temperature, the bulb breaks and water starts flowing through the head. 

Color-code and activation temp. Of bulb 

Orange -    57 °C       Green -   93°C 

Red    -         68°C       Blue -     141°C 

Yellow -      79°C       Purple -   182°C 

Zone Classification relating Flammable Atmosphere: 

• ZONE-0: Explosive gas atmosphere are present continuously of present long period. 
• ZONE-1 : Explosive gas atmosphere likely to occur normal operation. 
• ZONE-2: Explosive gas atmosphere not likely to occur in normal operation. If it occurs it will only exist for a short time. 

Emergency Response during Fire Emergency: 

•  If you discover a fire; 
•  Stop the work- Make sure all tools placed in a safe manner and equipment and machinery turned off. 
•  Activate the nearest fire alarm if available or call for help before attempting to extinguish a fire (shout: “Fire” “Fire” “Fire”). 

•  Notify Fire station if possible 
•  Attempt to extinguish the fire if the fire is small. 
•  If the fire is too big to control with the equipment at hand, retreat. 
•  Proceed to assembly point for head count (name check).