Reuse of frigerant

Recovered refrigerant  may be reused in the same system from which it was removed or it may be removed from the site and processed for use in another system depending upon the reason for its removal and its condition, i.e the level and types of contaminants.

There are many potential hazards in recover of refrigerant are acids, moisture, high boling residues and other particulate matter. Even low levels of these contaminants can refrigrant should be checked before reuse.

Refrigerant from a unit with a burnt-out hermetic compressor is reusable providing it has been recovered with a recovery unit incorporating an oil separator and filters. To check the acid content of any reclaimed oil it is necessary to use a refrigeration-oil-test-kit. Usually it is only a matter of filling a test bottle with the oil to be tested and mixing it with the twst liquid inside If result shows purple: oil is safe. If liguid turns yellow this would show the oil is acidic-and refrigerant/oil should not be used in system. Such material should be sent for reclamation or destruction 

Liquid transfer

If the recovery unit does not have a built-in liquid pump or is otherwise not designed to handle liquid, then liquid can be removed from a system using two recovery cylinders and a  recovery unit. The recovery cylinders must have two ports and two valves one each for liqued and one each for vapour connections. Connect one cylinder liquid port directly to the refrigration system at a point where liquid refrigrant can be decanted. connect the same cylinder vapor port to the recovery unit inlet. Use the recovery unit to draw vapor from the cylinder refrigeration system in to the cylinder. Take care as this can happen quite quickly.
         The second cylinder is used to collet the refrigerant from the recovey unit as it draws it from the first cylinder. If the recovery unit has adequate onbord storage capacity this may not be necessary. once all the liquid refrigrant has been recovered from refrigeration system, the connection are be relocated and the remaining refrigerant recovered in vapor recovery mode. It may be found convenient to fit a liquid sight glass within the transfer line.

Recovery Technologies

Since a recovery unit will remove more fluorocarbon refrigerant from a than any other practicable method, their use should be regraded as the norm and the exception.
Contractors, engineers and equipment owners should ensure that recovery units are adequately available for use , in anticipation that they will be needed.
Their availability, sophistication, variation and demand are increasing and is resulting in their being more widely used.

As with vacuum pumps, recovery unit, will work much more efficiently if connection hoses are kept as short and as large in diameter as possible. A8/3" diameter hose should be the minimum size used and half inch is preferable.
However, not being able to get a recovery unit close to a system is not an acceptable excuse for not using one. If long hoses have to used all that will happen is recovery will take longer.

Recharge Oil Hermatic Compressor

To recharge with a measured amount of the oil. compressor must be removed from the system. and the oil must be drained out from the suction line stub by tilting the compressor. The exact amount of oil must be clear before recharging is stated. Check the instruction manual for correct charge.The avoid too much mixture of refrigerant in the oil and to avoid emission of refrigerant, an oil heater could be installed. After the compressor is reinstalled the system must then be evacuated by means of an access valve of the process tube before recharging with refrigerant and operating. Never use oil from bottles or drums which have been left open. (moisture)

Oli Changing

Most welded hermetic compressor have no means of determining the oil. This type of compressor is primarily designed for installation in factory designed. assembled, and charged system where the systems the oil charge can be accurately measured into the system at the time of original assembly. In case of leak ,if the amount of oil lost is small and can be reasonably calculated, this amount should be added to compressor. If however, there is major loss of oil, the service technician must remove the compressor, drain the oil, and add the correct measured charge before replacing the compressor.

semihermatic and open type compressor are normally equipped with crankcase sight glasses, the oil level should be maintained at or slightly above the center of the sight-glass while operating. An abnormally low oil level may result in a loss of lubrication, while an excessively high oil circulation. The oil level may very considerably on initial start-up if liquid refrigerant is present in crankcase, and the oil level should be checked with the compressor running after having reached established condition.

Ammonia Leak Detection

leak can detected by passing an open bottle or squeeze bottle of concentrated hydrochloric acid in the vicinity of the suspected leak.
Dense white fumes of ammonium chloride will be formed at the leak site.Wet red litmus paper or phenolphthalein paper will undergo a colour change in an ammonia atmosphere and are of help in detecting small ammonia leaks.

VACUUM

As has been stressed above, refrigerant is sensitive to moisture in the system. To understand how water behaves and how to dry out a system, the following natural law must be understood. The boiling point of water varies depending on pressure. In SI unites, pressure are expressed in KPa (Kilopascals). Normal atmospheic pressure is 101.3KPa. But for practical engineering purposes, gauges are often calibrated at 100 KPa for atmospheric pressure. Pressures lower than atmospheric are called partial vacum. Zero on the absolute presser scale is at a pressure which cannot be further reduced. A perfect vacuum is 0 Pa.(Pascal"s) The pascal, rether than the kilo pascal, is used for measuring high vacuums (pressures close to an absolute vacuum). The relationship between absolute and guage pressre is also impornt to understand when preforming a vacuum procedure on your system. Gauges are normally calibrated to read zero at the atmospheric pressure but not always. In this illustration the atmospheric pressure is assumed to stanrd at sea level.

To Be Continue

How to Service Splite type Air Condition

Step 1

Genaral Good Service Practies

NON CONDENSABLES

Gases,other than refrigrant ,are contaminants that frequently found in air conditining and refrigration system.These gases infiltrate sealed system in the following manner: (1) Non-condensable gases are present during manufacture and remain due to incomplete evacuation,(2) non-condenseble gases are desorbed from viarious system meterials of are formed by decomposition of gases at elevated temperatures during system operation,(3) non-condensable gases are enter throught low side (below atmospheric pressure) leak and (4) non-condenseble gases are formed from chemical reactions between refrigrants,lubricant and other components in the refrigerating system,in extreme cases,the refrigranting unit fails.


       Chemically inert gases in thr system,Which do not liquefy in condenser, redue the cooling efficency. The quatity of inert noncondensable gas that is harmful depeds on the design and size of the refrigranting system and nature of the refrigrant Its presence conditributes to higher than normal head pressires and resultant higher discharge temperature. Higher temperatures speed up undersirable chemical reactions. Gases found in hermatic refrigration units includes nitrogen,oxygen,carbon dioxide,carbon monoxide,methen and hydrogen. The first three gases listed originate from incomplate air avacuation oe a low side leak in system. Carbon dioxide and carbon monoxide usually from when organic insulation materials are overheated. Hydrogen has been detected when a compressor is experiencing serious bearing were. Only trace amounts of these gases are present in well-designed,properly functioning eqipment.

Manual relese of non condensables. 1-compressor, 2-condenser, 3-receiver

Our Class Room 

MAINTENCE

Refrigeration system must be inspected and maintained regularly and thoroughty.To minimise emissions. the refrigerant and oil must be transferred with as little loss as possible. The frequency of the necessary inspections and maintenance depends on the intensity of use of the system. on the refrigerant charge,and on the nature of the system. Any leakage detected must be isolated,and refrigerant contained in the letter must be either transferred within the system. or intro a service container for refrigerant. Maintenance includes a check. of proper function and correct setting of the controls and safety devices Specific maintenance  tasks will be covered in chapter 5,by applications

SAFETY CLOTH AND WELDING PHOTO

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