GAS SAFETY IN BLAST FURNACE

GAS SAFETY IN IRON INDUSTRY(Blast furnace)

1.      INTRODUCTION

The Most potential hazardous element in the process of our plant is MBF gas i.e. the CO content in it, Un less handled carefully it may cause havoc by damaging man and machine. To bring safe condition we must be knowledgeable about CO gas and its characters. More over we must always obey safety rules and adopt safely procedures, safe methods and safe practices while caring out our jobs for operation maintenance and other services. Only then we can have Excellency in our performance for production and productivity with quality. Obey the gas safety rules gas will obey you.

2.     GAS GENERATION, HANDLING AND USE

BF gas is a by-product of MBF operation having good fuel value. It is used for most of our thermal activities in the plant. We use it as fuel to heat the MBF and boiler. It is transported to consumption site by steel pipes and control at several places by butterfly valves and water seals.

Hourly generation of MBF Gas is about 77000-80000 Nm3/Hr with service line pressure 700-800 mmwc. The CO content of this gas is about 22-24% and its calorific value is 650-680 K.Cal/Nm3.

Other gases used in the plant are Oxygen, LPG, and Nitrogen etc in cylinders. All these gases can create danger when handling carelessly.

3.     CO GAS AND IT’S HAZARDNESS

This gas is colorless, test less, odorless with a peculiar smell. Unless one is very much familiar with gas, it is difficult to detect it’s presence without testing instruments. But it has its effect when breathed in along with atmospheric air. Because of affinity of hemoglobin to CO (about 200 to 300 times) the following symptoms in human body is felt within a short period:

·        Headache

·        Nausia

·        Vomiting

·        Feeling giddiness and oppression in chest

·        Mental confusion

·        Difficult in breathing

·        Unconscious and death

The effects of Carbon Monoxide on the human system in different concentrations in atmosphere

Sl. No.	‘CO’ CONCENTRATION IN AIR	EFFECT ON EXPOSURE
1	0.003% (30 PPM)	NO EFFECT ON EXPOSURE OF 8 HOURS
2	0.005% (50 PPM)	IMPERCEPTIBLE FOR 8 Hrs OF EXPOSURE
3	0.01% (100 PPM)	IMPERCEPTIBLE FOR 4 Hrs OF EXPOSURE
4	0.02% (200 PPM)	MILD& FRONTAL HEADACHE AFTER 2-3 Hrs. OF EXPOSURE
5	0.04% (400 PPM)	i. MILD HEADACHE AFTER 1 Hr. OF EXPOSURE ii. OCCIPITAL HEADACHE AFTER 2-3 Hrs. OF EXPOSURE
6	0.08% (800 PPM)	HEADACHE, DIZZINESS AFTER 3-4 Hrs OF EXPOSURE
7	0.16% (1600 PPM)	i. ALL ABOVE SYMPTOMS IN 20 Mins. OF EXPOSURE ii. COLLAPSE UNCONSCIOUSNESS & PROBABILITY OF DEATH IN 2 Hrs. OF EXPOSURE
8	0.32% (3200 PPM)	ALL ABOVE SYMPTOMS IN 05 Mins. OF EXPOSURE, DEATH IN 30 Mins. OF EXPOSURE
9	0.64% (6400 PPM)	ALL ABOVE SYMPTOMS IN 1-2 Mins. OF EXPOSURE, DEATH IN 30 Mins. OF EXPOSURE
10.	1.28% (12800 PPM)	INSTANTANEOUS DEATH IN 1-4 Mins.

Age and physical condition of the body also have their influences. Alcoholism and obesity lower body’s resistance to the age. There is also individual variation depending upon the certain factors influencing absorption. E.g. blood volume, circulatory deficiency, breathing rate, status of health, anemia, old age etc.

4. CO GAS DETECTION AND PROBLEMS

There must be a periodical inspection and checking for any gas leakage from gas handling equipments. More over the test for gas leaking must be conducted immediately after having doubt. This test and detection must be conducted by authorized person with standard detecting instruments. The following safety tools and applications are must for the purpose:

For Detection:-

·        Canapy birds

·        CO Detector

·        Digital CO indicator

·        Tox guard (for co presence in atmos)

·        Explosive Gas Detector

For Protection:-

·        Gas Mask- blower type

·        Oxygen type gas mask

·        Oxygen respiration

·        First Aid Box

·        Stretcher

·        Caution and warning boards

5. GAS HAZARDOUS LOCATIONS IN THE PLANT

The followings locations must be avoided always or be approached with safety precautions:

1.      MBF Top

2.      Cast house very near to Tuyere

3.      GCP, VDF, actuator of venture

4.      Dust Catcher and its bottom bell valve and fresh extracted flue from dust deposit

5.      “U” seals and drain pots in clean gas line

6.      Burners of Stoves and Boiler

7.      Bleeder valves in gas line

6. PREVENTION AND CONTROL OF EXPLOSION AND FIRE IN GAS LINE

EXPLOSION:-Explosion is the rapid and uncontrolled combustion of fuel air mixture in a confined space resulting sound and sudden build up of pressure

Explosion occurs when

1.      The gas and the air mixture are within their explosive range

2.      The heat must be enough to ignite the resulting mixture of gas and air

3.      The mixture of gas and air is not sufficient to ignite the explosive mixture, there will be no explosion

Gas	Lower explosive limit	Upper explosive limit
BFG	Of gas in the mixture 35%	Of gas in the mixture 73.5%

Prevention of Explosion:-

1.      Avoid the formation of explosive mixture by purging the gas main with steam

2.      Prevent the suction of air in the gas main

3.      Naked lights must not be used near any de-pressurized gas mains unless the same have been thoroughly purged

4.      It is prohibited to have source of ignition near gas valves, gas line joints, gas holders and gas impulse lines

5.      In case of furnace going down for the repair, gas pipes to the furnace should be disconnected wherever possible and water seal on blank plates should be inserted into the mains

6.      Welding and cutting jobs on the gas line should be done only after these are purged and line is isolated by water seal or blank plates before the place where the welding or cutting job is to done. It is necessary to take clearance from the Process Department before doing any welding or gas cutting job.

7.      Routine maintenance of gas lines, taking quick action for stopping leakages when found proper ventilation of enclosed spaces, quick steam purging arrangement and good house-keeping help to prevent explosion.

FIRE DUE TO BF GAS

Action to be taken in case of fire in Gas Line

If the gas line catches fire during work on through some cracks as because of some leakage, it should be extinguisher with water, co2 extinguisher. The portion of the gas main affected must be cooled down with water and only after the fire is extinguished should the affected main be isolated for carrying out the repairs. The leakage of gas, which has resulted in fire, must be stopped after the fire is extinguished.

          It should be remembered that the gas pressure in the mains must be reduced below 100 mmwc where fire is still there.

          Inform MBF Control Room in case of all fire in Gas line

7. GENERAL SAFETY PRECAUTIONS

1.      No unauthorized person is allowed to enter I the gas hazard area.

2.      Unless any demand, always avoid to go to near to gas handling lines and equipments such as MBF top, Dust Catcher, GCP, gas lines and Bleeder valves. Entrance to gas Hazard area is normally prohibited

3.      No body must take rest or be wormed near MBF

4.      No single person must not go to gas hazardous area for inspection and work

5.      No body with empty belly or with body ailment should be allowed to work in the position with gas hazard

6.      No naked flame is allowed to gas leaking suspected area.

7.      Test the suspected leaking point with soap water only

8.      Report Shift In charge immediately about the gas leakage and arrest the leakage without time loss by safety procedure

9.      go for any maintenance in gas line after getting the clearance from proper authority

10. .Go away from the place where you smell a peculiar smelling with uneasy feeling to a different clear air site

11. When you see somebody unable to move with gas poisonings do not help him alone. Seek the help of others to remove him immediately from that place. If necessary use gas mask

12. Safety appliances must be in good working order and be kept it an easily approachable marked area.

13. Follow the standard instructions for maintaining MBF gas pressure at different positions and it’s critical higher or lower limit

14. Conditions and sequence must be maintained before all owing BFG in burner of stove and boiler to avoid explosion

15. Gas line pressure and sequence of operations must be maintained for bleeding or stem purging.

16. While bleeding or purging, see that there is no man in the direction that gas air mixture blows

17. Cordon off gas leaking area and fix caution and danger board

8.     SAFETY PRECAUTIONS AND PROCEDURE TO WORK IN GAS HAZARD LOCATIONS

Special safety precautions and procedure must always be followed for any job to be done in gas hazard locations earlier. Before taking clearance from process department no body should go in the gas hazard location. Near any de-pressurized gas mains or equipment naked light must not be used. Steam purging is necessary to avoid formation of explosive mixture before welding or cutting job. Keep open the corresponding relief valve to avoid sudden build up of pressure in a confined space

9.     CAUSES LEADING TO GAS EXPOSURE AND EXPLOSION

1.      Ignorance about the gas safety, CO gas and its effect

2.      New man arrival (shift changing)

3.      During shut down and start up of MBF

4.      During inspection and maintenance

5.      Faulty gas pressure control (beyond critical limit)

6.      Confusion about preventive method and procedure

7.      Disobedience, carelessness and hurries

8.      Non adherence to safety rules

9.      Non adherence to gas handling procedure

10. Ignorance of using life saving appliances

11. Negligent supervisor for judgment and watchfulness during work carried on gas hazard area

12. Doubtful supervisor not consulting with superiors the event of new conditions arises

13. Non protection of safety appliances and wrong testing tools

10. CARBON MONOXIDE EXPOSURE - FIRST AID:-

DO’S

1.       The affected person should immediately removed from the gaseous atmosphere to FIRST AID

2.     Any tight fitting clothes, shoes, and belt must be REMOVED

3.      Any PHYSICAL EXERTION by the affected person must be avoided

4.     If conscious, the affected person must be REASSURED

5.      MEDICAL UNIT must be informed and the affected person should be sent in an AMBULANCE ONLY.( Medical Unit: DIAL   )

6.      Oxygen inhalation if required should be started immediately by a trained person

7.      Concerned supervisor and safety personal should be informed

DON’TS

1.      Do not give warm milk or food to the affected person

2.      Do not crowd around the affected person. Give him fresh air

3.     Do not Panic

11.  CARBON MONOXIDE POISONING – CLINIC SIDE

The air we breathe contains 21% of Oxygen at normal atmosphere pressure (760 mm Hg). With respiration air enters into the minutest microscope sacs (units) of lungs called “Alveoli”. It is in the alveoli that the oxygen of the air gets absorbed by the hemoglobin of blood to form a compound called oxy hemoglobin (O2+Hb=OHb). Oxygen requirement of the tissues of the body is thereby met oxy hemoglobin.

          Unfortunately, hemoglobin has 200 to 300 times more affinity for CARBON MONOXIDE than Oxygen. Carbon Monoxide when breathed along with air into the lungs, combines readily with hemoglobin to form CARBOXY HEMOGLOBIN (CO+Hb=COHb) and thereby deprives the blood of its oxygen carrying capacity. Thus the body tissues suffer from lack of oxygen (ANOXAEMIA). The symptoms, which occur in carbon monoxide poisoning, is directly proportional to the degree of anoxaemia.

          According the percentage of CO in the atmosphere and the period of exposure, percentage of COHb in blood increases giving rise to certain symptoms. They are HEADACHE, NAUSEA, DIZZINESS, COLLAPSE, UNCONSCIOUS and even death. Other factors that lower body resistance to the gas are OBESITY and ALCOHOLISM. Circulatory deficiencies, anaemia, rate of respiration are some other factors influencing CO absorption

          An Instrument called MINI SMDKERLYZER marked by Bedfont helps in assessing the percentage of COHb in blood by simple breath test.