Safe Handling Of Cryoganic Liquid

Safe Handling of Cryogenic Liquid

INTRODUCTION To deal with the production and utilization of low temperature in the region from absolute zero to 123 0C we come in contact with cryogenics. Cryogenic is the word made from two Greek words having meaning, “The making of cold”. Some of cryogenic liquid are helium nitrogen oxygen etc.

Cryogenic have to property to solidify the

surrounding air. Cryogenic have wide application in the chemical field. (i)

Nitrogen preserves the flavor of packed foods by chemical action.

(ii)

Preservation of blood of human being.

(iii)

Liquid hydrogen and liquid oxygen are used for the rocket fuels. These cryogenic have wide application in the chemical field

it has also hazardous if it not handled carefully so handling of cryogenic is important point. These liquids have received a big boost in recent years but at the same time they are very hazardous from handler’s safety point of view. Hence in this report safe handling of cryogenic liquid is focused and studied. C.O.E.&T.,Akola

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Safe Handling of Cryogenic Liquid

CRYOGENIC LIQUIDS Cryogenic liquids are defined as liquid with a normal boiling point below –2400F (-1500C). Oxygen and nitrogen form a major portion of cryogenic industry. Other cryogenic liquid are;  Helium, argon, krypton, xenon, neon  Hydrogen  Acetylene, ethylene, ethane etc. Properties of cryogenic liquid Cryogenic liquid deal with the behaviors of materials at low temperature. It has some special properties as given below; (i) They exist at temperature of –1000F (-60 0C) to –4000F (-2690C) (ii) They get vaporized only when volume increases by 700 to 800 times. (iii) Most cryogenic liquid are odorless, and testless. Most liquid have no color except liquid oxygen which is light blue. (iv) When cryogenic liquid exposed to the atmosphere they create a highly visible dense fog. (v) Cryogenic liquid can achieved by the liquefaction of gas. C.O.E.&T.,Akola

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Safe Handling of Cryogenic Liquid

METHOD OF LIQUEFACTION OF GASES At room temperature and atmospheric pressure of liquid are condensed by cooling. But in some cases it happens only on compression or combination of compression and cooling. For example: ammonia, sulfur dioxide methyl chloride etc. One or more of following three ways to produces liquid may carry out the liquefaction; (i)

Exchange of heat with colder stream.

(ii)

Expansion through throttle value.

(iii)

Adiabatic expansion against a piston or in turbines.

C.O.E.&T.,Akola

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Safe Handling of Cryogenic Liquid

APPLICATION OF CRYOGENIC LIQUID (A) Oxygen (-1830C) (i)

Liquid oxygen is used in significant amount for welding and cutting.

(ii)

Liquid oxygen has may uses in paper mill including paper pulp bleaching black liquor oxidation.

(iii)

Oxygen and used in steel and iron industry in very large portion.

(iv)

It is used for water waste treatment.

(v)

It is used for disposed and conversions of refuse to usable by product.

(B) Nitrogen (- 195.80C) It is most common cryogenic liquid. i)

Nitrogen has great application in chemical and food industries.

ii)

It is often used in petrochemical and chemical facilities as a blanket, purge or dry gas because it is inert and water free.

iii)

It is also used for manufacture of semiconductor and other clean process.

C.O.E.&T.,Akola

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Safe Handling of Cryogenic Liquid iv)

It play major role in flash freezing of food to minimize product damage dehydration.

v)

Nitrogen gas in injection into an aluminium can containing non carbonated drinks to provide the internal pressure necessary to minimize denting.

vi)

It is used for steel industry for blanketing and bright annealing.

vii)

It is used for testing oil recovery in old oil fields.

(C) Hydrogen (-2520C) i)

Hydrogen along with liquid oxygen fuel for NASA’s orbiter and many other non-solid fuel rockets.

ii)

It is also used in petroleum and petrochemical process.

(D) Helium (-269.90C) (i)

Helium coldest of routinely handled cryogens.

(ii)

Vapour pressurised helium is used in space shuttle program during take off for forcing liquid oxygen and liquid hydrogen from external fuel tank into orbiter engine.

C.O.E.&T.,Akola

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Safe Handling of Cryogenic Liquid (iii)

Helium has made magnetic resonance imaging (MRI) technology possible for hospitals.

(E) Argon (- 185.70C) Argon is used almost exclusively as a gas. It is used in two areas ; i)

An additive for the primary metals industry and

ii)

As a shielding gas for welding.

C.O.E.&T.,Akola

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Safe Handling of Cryogenic Liquid

DISADVANTAGES AND HAZARDS OF CRYOGENIC LIQUID 1) Their extremely low temperatures can produce cryogenic burns of skin delicate, tissue as eyes. 2) The vapours coming from these liquids are extremely cold and can product burns. 3) The extremely cold material may stick fast to skin and tear the flush when you attempts to with draw it. 4) Soft and pliable objects such as rubber or plastics are easily broken when contacted with cold material. 5) Extremely cold cryogens such as helium and hydrogen can ever freeze or solidify the surrounding air. 6) Oxygen above 23.5% in air creates an enriched atmosphere ripe for combustion. 7) Oxygen container below 16% by volume can cause dizziness rapid heart beat, nausea, vomiting, metal confusion loss of consciousness and death.

C.O.E.&T.,Akola

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Safe Handling of Cryogenic Liquid

SAFETY PRECAUTION (A) Handling (1) Always handle cryogenic liquids carefully. (2) Never allow any unprotected part of your body to touch un-insulated pipes or vessels containing cryogenic liquid. (3) Use longs to immerse and remove objects from cryogenic liquid. (4) Rubber and plastic may become very brittle in extreme cold Handle these items carefully when removing them from cryogenic liquid.

(B) Personal protection equipment (1)

Personnel must be thoroughly familiar with the properties and safety consideration before being allowed to handled a cryogenic liquid and it’s associated equipment.

(2)

Recommended personal equipment should be used. It include

(i) A full-face shield over safety glass. C.O.E.&T.,Akola

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Safe Handling of Cryogenic Liquid (ii) Thermal insulated or leather gloves Glove should be lower fitting so they are able to be quickly removed if cryogenic liquid is spilled on there insulated gloves are not made to permit the hands to be put into cryogenic liquid. They will only provide short-term protection from accidental contact with the liquid. (iii) Long sleeve shorts (iv) Trousers without cuff. (v) Safety shoes.

C) Special hydrogen precautions: (i)

Don’t permit smoking or open flames in any anywhere liquid hydrogen is stored or handled.

(ii)

All major stationary equipment should be properly grounded.

(iii)

Liquid hydrogen should not be poured from one container to another or transferred in an atmosphere of air, it this is done oxygen in the air will condense in the liquid hydrogen presenting possible explosion hazards.

C.O.E.&T.,Akola

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Safe Handling of Cryogenic Liquid (iv)

Liquid hydrogen also has the potential of solidifying are that can block safety relief and other opening that lead to rupture of container.

(v)

Every effect must be made to avoid spills, regardless of the rate of ventilation.

D) Special Inert gas precautions (1) The potential for asphyxitation must be recognized when handling inert cryogenic liquid. (2) People should not be permitted in atmospheres containing less that 19.5% oxygen without applies air. (3) Liquid helium has the potential to solidify air, which can block pressure relief devices, and other container opening this can result in pressure build up that may rupture the container.

E) Special oxygen precaution (1) Do not permit smoking or open flames in any areas where liquid oxygen is stored or handled.

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Safe Handling of Cryogenic Liquid (2) Do not permit liquid oxygen or oxygen enriched air to come in contact with organic material or flammable or combustible substances of any kind. (3) Faces contaminated with combustible do not walk on or roll equipment over the spill area. Keep the sources of ignition away for 30 minutes after all fast or fog has disappeared. (4) Any clothing has been soaked with liquid oxygen shall preferable be removed immediately and aired for at least an hours. (5) Personnel should stay in a well-ventilated area and avoid any sources of ignition until their clothing is completely free of any excess oxygen.

F) Fighting Fires 1) The best fire fighting technique is simply to shut off the flow of oxygen liquid 2) If electrical equipment is involved in the fire be sure the power supply is disconnected before fighting the fire with water. 3) Use carbon dioxide or dry chemical extinguishers 4) Use large quantities of water in spray form C.O.E.&T.,Akola

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Safe Handling of Cryogenic Liquid

STORAGE OF CRYOGENIC LIQUIDS 1) Cryogenic liquid are stored, shipped and handled in several types of container depending on quantity of required storage quantity very from a few liters to many thousands of gallons. Container are designed and manufactured according to the applicable codes and specification for the temperatures and pressure involved. The type of container in use are (i)

Dewar

(ii)

Cryogenic liquid cylinder

(iii)

Cryogenic storage tank

(i) Dewar: Figure shows a typical vacuum jacketed dewar a lower fitting dust cap over the outlet of the neck tube prevents atmosphere moisture from plugging the near and allow gas produced from vaporized liquid to escape this type of container is non pressurized. The most common unit of measure for the capacity of dewar is liter 5 to 200 liters dewars are available product may be removed from small dewars by pouring while large size well required a transfer tubes C.O.E.&T.,Akola

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Safe Handling of Cryogenic Liquid

Fig. 1 A Typical Dewar

(ii) Cryogenic liquid cylinder:

figure shows a typical cryogenic

liquid cylinder. Cryogenic liquid cylinder are insulated vacuum jacket pressure vessel they come equipped with safety relies valves and rupture disc to protect the cylinder from excessive pressure build up. These containers operate at pressure up to 350 psig and have capacities between 80 to 450 liters of liquid

C.O.E.&T.,Akola

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Safe Handling of Cryogenic Liquid Product may be withdrawn as a by passing liquid through an internal vaporizer or as a liquid under it’s own vapour pressure.

Fig. 2

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Safe Handling of Cryogenic Liquid (iii) Cryogenic storage tanks: typical custom installations include a tank vaporizer pressure control manifold tanks may be spherical or cylindrical shape. They are mounted in fixed locations as stationary vessel or on railroad car or truck chassis for easy transportation. Size range from 500 gallons to 420000 gallons all tanks are powder and vacuum insulated in annular space tanks are equipped with various aircraft to control product fill pressure build up pressure relief, product withdrawn and tank vaccum Tanks are design to ASME specification for the pressure and temperature involved.

C.O.E.&T.,Akola

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Safe Handling of Cryogenic Liquid

CONCLUSION As we come across the various cryogenic liquid there properties, use disadvantages and safety precaution It is found that they require safety handling the handling of liquid is not new science or highly trained laboratory technician required. Today’s cryogenic liquid are handled in large and very small quantities they are handled under laboratory condition they are handled in steel mills and waste water treatment plant they are handled at atmosphere pressure and under very high pressure lastly they are handled daily like most any fluid that can pose danger when mishandling.

C.O.E.&T.,Akola

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Safe Handling of Cryogenic Liquid

REFERENCE Books  (1)

Shreve’s chemical process industries By:

(2)

George T. Austin

Outline of chemical Technology By:

Dryden

Websites  (1)

www.airproduct.com

(2)

www.cryogenic.com

(3)

www.safetygram.com

C.O.E.&T.,Akola

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