These low temperature fluids have the potential to cause suffocation, lung disorders, cold-contact lesions and frostbite, therefore training in their use is important.
a) Temperature Related
• The extremely low temperature of the liquid can cause severe burn-like damage to the skin either by contact with the fluid, surfaces cooled by the fluid or evolving gases. The hazard level is comparable to that of handling boiling water.
• The low temperature of the vapour can cause damage to softer tissues e.g. eyes and lungs but may not affect the skin during short exposure.
• Skin can freeze and adhere to liquid nitrogen cooled surfaces causing tearing on removal.
• Soft materials e.g. rubber and plastics become brittle when cooled by liquid nitrogen and may shatter unexpectedly.
• Liquid oxygen may condense in containers of liquid nitrogen or vessels cooled by liquid nitrogen. This can be extremely hazardous because of the pressure rise on the slightest degree of warming above the boiling point of oxygen ( -183°C ) and the possibility of explosive reaction with oxidisable material.
• Thermal stress damage can be caused to containers because of large, rapid changes of temperature.
b) Vapour Related
• Large volumes of nitrogen gas are evolved from small volumes of liquid nitrogen (x~700) and this can easily replace normal air in poorly ventilated areas leading to the danger of asphyxiation. It should be noted that oxygen normally constitutes 21% of air. Atmospheres containing less than 10% oxygen can result in brain damage and death (the gasping reflex is triggered by excess carbon dioxide and
not by shortage of oxygen), levels of 18% or less are dangerous and entry into regions with levels less than 20% is not recommended.
• Oxygen condensed into leaking containers can explode on heating following resealing or blockage with ice.
Precautions
Some liquefied gases are flammable eg hydrogen and others such as liquefied oxygen promote rapid combustion. The more common problems are due to explosion of the containers. The cryogenic liquids evaporate to form large volumes of gas at room temperatures. During the evaporation process, water vapour can be condensed from the air forming ice which then blocks the vent on the container causing over pressurisation of the vessel.
Regular checks should be made to ensure that the venting mechanism on the container is still operable.
Transportation of containers of cryogenic liquids in confined areas such as cars or lifts should only be undertaken if a risk assessment has been undertaken and the procedure is then approved.
Departments should note that the maximum capacity of a vacuum insulated container for keeping cryogenic liquids in a laboratory should not exceed 160
litres.
If flammable or poisonous cryogenic liquids are to be used in the laboratory, the container shall not exceed Five Litres and provision must be made for special ventilation and where appropriate, gas detectors put in place.
Cryogenic liquids should not be stored in non-ventilated areas such as cold rooms.
Properties: Liquid Nitrogen
• Liquid Nitrogen has a boiling point of -195.8°C
• Volume of expansion liquid to gas (at 15°C, 1 atm.) = 682.1
• Sg = 0.808 (at -195.8°C).
• Density of liquid (normal boiling point, 1 atm.) = 0.807 g/cc
• Colourless, Odourless liquid similar in appearance to water.
Operation
• Always use liquid nitrogen in a well ventilated area, especially when filling a warm container or transfer tube or inserting a warm object, as large volumes of nitrogen
gas are evolved. (Outside normal working hours it is prohibited to travel in a lift with a dewar of liquid nitrogen, failure of the dewar or a large spillage could result in asphyxia in the confined area of a lift at a time when you are unlikely to be found or able to raise the alarm quickly).
• Use only containers or fittings (pipes, tongs etc.) that have been designed specifically for use with cryogenic liquids as non-specialised equipment may crack or fail. In particular, do not use food type vacuum flasks as they can implode resulting in flying glass fragments.
• Protect all glass Dewars against the possibility of flying glass fragments, arising from failure by mechanical or temperature stress damage, by sealing all exposed glass either in an insulated metal can or by wrapping with adhesive tape.
• Always fill warm dewars slowly to reduce temperature shock effects and to minimise splashing. Do not overpressure the storage dewar when filling a globular dewar. Use the minimum pressure required to maintain a flow of liquid.
• Always make sure that containers of liquid nitrogen are suitably vented and unlikely to block due to ice formation.
• Beware of the formation of liquid oxygen in cold-traps that are open to air or the increase of liquid oxygen content in a flask of liquid nitrogen that has been cold for a long period. (Liquid oxygen has a blue water-like appearance). However, most liquid nitrogen containers are closed except for a small neck area and the nitrogen vapour issuing from the surface forms a barrier which keeps air away from the liquid thus preventing oxygen contamination. (An explosion at UMIST was caused apparently by overcooling of Rotaflo taps which leaked and allowed oxygen to condense into a sample tube. Subsequent warming resealed the Rotaflo but blew the tube apart as the oxygen evaporated.)
• Avoid skin contact with either liquid nitrogen or items cooled by liquid nitrogen as serious burns may occur. Beware of wearing gloves, wrist-bands or bracelets which may trap liquid nitrogen close to the skin.
• Always wear approved Personal Protective Equipment especially safety glasses to protect against splashes, vapour, failure of glass apparatus resulting in implosion, brittle failure of items cooled by liquid nitrogen.
Personal Protective Equipment
• Protective clothing suitable for handling these liquids shall be provided with particular attention given to gloves and eye/face protection. Aust Standard 1337
Eye Protectors for Industrial Applications recommends a full-face shield be worn.
• Dry asbestos (substitute) or dry leather gloves (when handling equipment that has been in contact with the liquid). NB there is dispute over the advisability of wearing gloves while handling liquid nitrogen because there is a belief that gloves could fill with liquid and therefore prolong hand contact which would make burns more severe. If gloves are worn they should be loose fitting and easily removed.
• Lab coat or overalls are advisable to minimise skin contact, also, wear trousers over shoe/boot tops to prevent shoes filling in the event of a spillage.
Training
All staff using or handling cryogenic liquids must receive training which includes care, selection and use of protective equipment, hazards associated with its use and emergency procedures. New users of liquid nitrogen should receive instruction in its use from experienced members of the academic or technical staff.
The B.O.C. leaflet "Recommended Safety Precautions for Handling Cryogenic Liquids." should be read.
Level of Risk Remaining
There remains a significant risk in using liquid nitrogen from the inadvertent condensation of oxygen into a closed system. It is recommended that whenever possible some other coolant is used e.g. solid carbon dioxide/liquid traps or baths -
the preferred liquids for such baths are isopropanol or glycols. It is strongly recommended that such baths are used in preference to liquid nitrogen when long term storage is envisaged.
Properties: Solid Carbon Dioxide
Sublimation point
-78.5°C
Melting point
-56.6°C
Volume of expansion solid to gas ~900
Hazards
Apart from being unable to condense oxygen, hazards associated with solid carbon dioxide are similar to those described for liquid nitrogen i.e.
temperature related and vapour related. In operation, similar precautions should be taken against cold burns and asphyxiation.
Emergency Procedures
Temperature related
•
For brief, localised contact with cold material - flush the area with water. (Water is used because of its high heat capacity.) Obtain First Aid assistance.
•
More prolonged contact will require medical treatment. Call a First Aider.
Vapour related
•
Following a large spillage of liquid nitrogen, evacuate the area and call for help.
Crane Operator
Dos
(1) Do ensure that you are fully conversant with the relevant Installation, safe operating procedures and Standing Instructions.
(2) Do ensure that you are fully conversant with the controls and characteristics of the crane you are about to operate.
(3) Do carry out a visual check of the crane to determine serviceability.
(4) Do complete the manufacturer’s or owner’s pre-start and operational checklist prior to commencing crane operations.
(5) Do report any defects to your line supervisor.
(6) Do post ‘do not operate’ signs in a prominent position in the operator’s cabin if the crane is out of use for maintenance etc.
(7) Do ensure that the crane engine is isolated and that systems have been depressurised while maintenance is being carried out.
(8) Do confirm the security of the manually activated emergency load release controller to ensure that it cannot be inadvertently activated.
(9) Do be aware of the wind speed and direction.
(10) Do keep within the crane’s operating radius at all times during lifting operations.
(11) Do ensure that you are aware of any obstruction and/or activities that are ongoing within the operating radius of the crane.
(12) Do ensure that the Banksman has taken up position to determine the crane boom proximity to potential collision points when carrying out lifts from areas such as the drill floor.
(13)Do talk to the Banksman to ensure that you are aware of all aspects/requirements of the lifting operation to be undertaken and of the signalling method to be used.
(14) Do ensure that a Banksman is present when stowing the boom in its cradle.
(15)Do function check all hoist and lower control systems prior to commencement of lifting operations.
(16) Do operate the crane controls as smoothly as conditions allow and try to avoid ‘snatch’ as shock loading imposes undue strain on the crane, its equipment and support structure.
(17) Do exercise caution when lowering the crane hook block such that the rope
‘payout rate’ is not exceeded, thus preventing possible damage to the rope.
(18) Do everything possible to operate and maintain the crane in a manner that ensures the complete safety of the crane, the Installation and all personnel in the vicinity.
(19) Do talk to the Crane Operator from the previous shift before he/she leaves the crane to determine if the crane has any defects that require immediate rectification or if there is any other important information that shall be known.
Similarly, at the end of each tour of duty ensure that safety critical information is relayed to relief personnel.
(20) Do ensure that loads are landed safely and the crane is secured if an Installation emergency occurs.
(21) Do ensure that you are familiar with the operation of emergency load release and load lowering equipment (if fitted).
(22) Do ensure that during crane maintenance activities tools, equipment and lubricants are retained in a secure manner. This is particularly important when working at heights. Where hand tools are being used in these circumstances the use of a ‘tool saver’ device is mandatory.
Do Nots
(1) Do not operate the crane until you are certain that personnel descending from the crane or its structure are well clear/outwith the swing path of the crane superstructure and have signalled the all-clear to you.
(2) Do not authorise access to the crane or its superstructure until the crane has been brought to a complete halt.
(3) Do not lift loads outside or inside the working radius of the crane.
(4) Do not depend on limits or cut-outs to stop the boom or load-line motions.
(5) Do not continue with a lifting operation if you lose sight of or radio contact with your designated Banksman.
(6) Do not lift loads from baskets or containers until all personnel have come out of the unit concerned.
(7) Do not interfere with Rated Capacity Indicators (RCIs) or other safety equipment attached to the crane. This is illegal.
(8) Do not allow personnel to ride on crane hook blocks or on loads.
(9) Do not leave the crane control cabin when there is a load suspended on the hook.
(10) Do not use the crane if a fault or defect is liable to compromise the safety of personnel or lead to the possible damage of equipment.
(11) Do not tamper with or adjust any equipment on the crane unless you have the technical qualification, are competent and/or are authorised to do so.
(12) Do not lift loads of large surface areas, eg steel plates in high wind conditions. Always assess the effect the weather conditions could have on the behaviour of the load.
(25) Do not lift wire ropes, cables or other material/equipment of a similar nature that are not already spooled on drums provided for that purpose.
DUTIES OF DRIVERS / OPERATIORS ENGAGED
THROUGH CONTRACTUAL AGENCY
a. Before commencing work, the driven shall personally inspect and test the vehicles for its roadworthiness, paying particulars attention to the (i) tyro pressure (ii) brakes (iii) horn (iv) AVAS (v) lights. If he finds any defect which is likely to make the driving unsage, he shall report the matter to the competent persons & shall not operate the vehicle till the defects are remedied.
b. The driver /b operator shall abide by rules, regulations & bylaws and other rules applicable to him.
c. No driver / operator shall enter the mine without wearing foot wears & safety helmet.
d. The driver / operator shall carry with him identity card containg. Number in ‘B’
form, photo. & other details.
e. Driver / operator shall get his attendance marked and vehicle checked at the barrier before entering the mine. He shall not carry with him other person as a passenger or helper.
f. The driver shall handle the truck/dumper carefully & keep it under control at all times. He shall negotiate downhill gradients un low gear so that minimum of braking is required.
g. He shall not drive too fast shall avoid distraction & shall drive defensively.
h. He
shall
obey
all
the
orders/inaructions
as
given
by
field
supervisors/overman/mining sirdar.
i. When approaching a loading machine, the driver of the truck shall sound the audible warning single and shall not attempt pass the loading machine. Until he has received a proper audible signal in reply.
j. Before passing a road or railway line, he shall reduce his speed, look in both directions along the road or line only if it is safe to do so.
k. the driver not operate the truck in reverse unless he has a clean view of the area .He shall give warning signal before reversing the vehicle.
l. The driver shall not drive too close behind a vehicle m. The driver shall see that ;
n. (i) The vehicle is not overloaded.
CONTRACTORS WORKERS
Mining is a hazardous job. Safety of employees working in mining & allied operations is the main concern of the mine management. The same safety Rules & Regulations are applicable for both departmental & contractual workers. As a principal employer the management is equally responsible for safety of contractual workers.
Now a day most of the works are being out sourced, mostly through private companies/ contractors. These companies/
contractors use to deploy semi-skilled or unskilled workers. With less salary these workers are being deployed for more than the stipulated duty hours, that too in an unhealthy working environment. These are some of the causes which lead to accident of contractual workers. Good work practice is one of the most demanding features in preventing accidents.
From accident statistics it reveals that about 80% of accidents occur due to human factor. Hence more stress is given on educating the work forces in good work practices, better working environment
& house keeping.
It is a trial to include some safety tips & code of practices for different contractual workers deployed in mines. The safety tips & code of practices collected, complied & included in this booklet will help in reducing accidents, if followed sincerely.
The contractual workers deployed by different contractors in different jobs & departments may be sub-divided as below to facilitate in framing safe work instructions for their job.
o Coal transportation work
o Civil work
o E&M work
o Mining & excavation work
o Security Services
SWI-1:
General practices for each & every contractor worker.
1) Every person working in mines must be Vocationally Trained (IVT).
2) Every person must be medically examined before appointment (IME).
3) Name & other details with photograph must be entered in form
‘B’ register maintained in mines.
4) The employee must mark his attendance ‘IN’ before starting work & mark his attendance ‘OUT’ on completion of work.
5) He must start work after consultation with the supervisor.
6) Perform your duties while you are physically & mentally fit.
7) In case of any injury, get First-Aid & inform the matter to higher authorities.
8) If any body doing any unsafe work, inform the matter to higher authorities.
9) Do not come to duty in intoxication.
10) Do not wear loose clothing.
