GB2404969A - Complete refrigerant recovery - Google Patents

Abstract

A refrigerant recovery system for a refrigeration circuit 1 comprises a recovery pump 2, a reservoir holder 3, weight scales 4, a vacuum pump 7, and a vacuum gauge 8. A pipe can be connected to either a cylinder of nitrogen 5 or a cylinder of a suitable refrigerant (6, Fig.2) eg R134a. The recovery system is first checked for leaks using the nitrogen supplied from the cylinder 5. The system is then evacuated using the vacuum pump 7. Refrigerant from the cylinder 6 introduced into the recovery system acts as a cushion for refrigerant recovered from the refrigeration circuit 1 using the recovery pump 2. The collected refrigerant is held and stored in the holder 3. The recovery pump may be stopped and restarted to gather all the refrigerant. The vacuum pump may be restarted to remove any trapped air.

Description

TIlE COMPLETE REFRIGERANT RECOVERY SYSTEM This idea was inspired by a

registered Construction and Industry Training Board (C1TB) refrigerant handling course. The attached sheets detail a series of improvements on the current refrigerant recovery teaching techniques. It shows how a trainee can be taught refrigerant handling techniques without any loss of refrigerant to the atmosphere; the idea can then be used by qualified technicians at minimum cost to themselves but maximum benefit to the environment. It could mean an end to the 'minimum allowable' deliberate losses made by refrigeration technicians and a start to the rebuilding of the earths atmosphere.

The principle used for the teaching of the refrigerant handling course was the vapour compression system. The working parts of this type of refrigerator are contained within a sealed circuit that contains a chemical substance called refrigerant, this refrigerant exists in both liquid and vapour form. As a chemical mixture it was the invention of its day, inside the refrigerator as a liquid, its pressure was dropped so that it would boil off at a temperature lower than its surroundings. Passing through a heat exchanger it would cool down the space around it. The low pressure vapour is then pressurized to raise its temperature and boiling point before passing through a second heat exchanger in contact with the ambient air temperature where it is cooled back into a liquid before being returned through the circuit again. :

With very few working parts refrigerators would work away for years, but as with all things some worked very well and others didn't. The popularity of refrigerating things, like food, and other goods meant that refrigerators appeared everywhere and subsequently changed the way we live today.

The fact that some refrigerators were less reliable than others created a whole new problem. The trouble with the component parts of a refrigerator is that they cannot really be tested properly until the circuit is complete and faded with refrigerant, so when a faulty item is fitted it normally means that the fully charged system needs to be emptied before any repairs or replacements can be made. The refrigeration technician is trained in using a suitable recovery pump with the correct accessories to remove the charge with the minimum leakage to atmosphere.

The recovery pump is like a second refrigeration circuit but this circuit is fitted with inlet and delivery shut off valves. When connected and running it is able to move the refrigerant from the refrigerator into a suitable storage container. The diagram below gives an example of one such set up that is being taught to trainee refrigeration technicians.

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| Refrigerant Flow | \ _; Recovery Recovery Pump Cylinder Refiigerator Trainer Fig (i) Refrigerant Recovery from a Refrigerant Trainer (CITB) This in itself is a vast improvement on the opening of a valve or cutting through of a pipe to release the charge to atmosphere and in recent years these practices have become condemned by almost everyone.

But why make such a big deal about the release of a refrigerant charge? Before the industrial revolution the upper atmosphere was in the main made up of oxygen compounds known as trioxygen or ozone. These ozone molecules prevented the damaging ultra-violet rays travelling from the sun reaching the earth's surface. The rays would split the three oxygen atoms apart using up the majority of their momentum in the process. The split would leave an unstable single oxygen atom and a double molecule (02), as there was nothing much else to join up with the single atom would eventually rejoin with a double rebuilding the protective layer.

Refrigerant has always been considered a stable compound and it was the stability of the compound that brought about its downfall. The refrigerant would turn into a vapour when released and although heavier than air in a confined area, it would eventually be picked up, and rise into the upper atmosphere.

In the upper atmosphere, the refrigerant was then able to help the ozone molecules slow down the ultra violet rays but this time when split the compound released an unstable chlorine atom that would then join up with the unstable oxygen atom making chlorine monoxide another stable compound but leaving the remainder of the refrigerant charge and lots of breathing oxygen (02) in the upper atmosphere. None of which was able to slow down the ultra violet rays from the sun.

Increases in skin cancer and the finding of the hole in the ozone layer made us all stop and think. Scientists and politicians quickly realised there was a problem; hence after many discussions laws were enforced, and new families of refrigerants were produced with similar properties but no chlorine. Recovery techniques were improved with the introduction of the recovery pump, and a fifed licence meant that technicians were forced to be brought up to date on a three yearly basis. The only problem with these new 'safe' refrigerant mixtures was that although they would not damage the ozone layer they did have a significant global warming effect on the planet. a\

Sometimes closely linked with the ozone problem, global warming is different. It has always been with us as a cloud of natural gasses that hold in the heat from the sun, keeping the ambient temperature at a comfortable level. The industrial revolution and the release of refrigerants have both added to the protective cloud making the planet overheat, this increased warming has given us the diverse weather systems we are subjected to each year, and yet again the fact that refrigerants are so stable means that they cause more harm then other gasses.

The technicians that work on refrigeration circuits have certainly felt the brunt of these findings the stricter guidelines, intense continuous training programmed all add to the expense; but the new initiatives have delayed the catastrophic effects of excessive releases to the atmosphere.

The diagram (Figure 1) shows a recovery circuit taught to potential technicians.

In this set up, the recovery pump sucks the refrigerator dry and pumps the charge into the storage cylinder so the components or faulty circuitry can be worked on. Up to this point there would have been very little release of refrigerant. So we have to ask ourselves the question.

Why spend the time and effort introducing yet another method of refrigerant recovery that can only cost more money? The answer is very simple; as the design of the recovery pump is based on a refrigeration circuit and the flow of refrigerant cannot be reversed. This means that at some point during the procedure the delivery hose on the outlet of the pump will have to be disconnected with a release of refrigerant into the atmosphere.

This release is classed as an "Inadvertent Loss: In practical terms, handling of any refrigerant involves the loss of a small quantity to the atmosphere, even when due care is taken to minimise losses at all times." C1TB revised 2001 | Refrigerant Flow | 1 - 1 1 ' G Refrigerant Trainer Fig (ii) Refrigerant Recovery Back Into a Trainer (CITB) In the classroom there can be no figure given for this amount as it is totally dependent on the experience of the technician and the quality of the equipment used. It has to be said that when any level of doubt is taught in the classroom it can only begin a series of Chinese whispers that could magnify the problem until the standards become a matter of personal preference and rules are forgotten until the next refresher course.

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A lot of the good practice carried out after this course comes down to how conscientious the technician is and how brave they are to stick to their guns when time and money start to interfere with each other. The trouble is, because there is no figure given the technician will be unsure and the public will be too scared to ask. In fact the practice of releasing a satisfactory minimum amount can only be achieved after the technician has become proficient in releasing more than the minimum amount.

Fortunately there are many devices on the market that will help reduce the amount of refrigerant released, for example, new recovery pumps can take in liquid or vapour speeding up the process. They are designed to empty themselves of liquid refrigerant, leaving only a vapour charge inside them and in their delivery lines. (Vspour expands less than liquid when boiling off.) Shorter connecting hoses mean the hoses hold less refrigerant, hoses come fitted with taps, and quick release couplings are available, all of which, help to cut down on the amount of refrigerant being released.

All of these new innovations, yet it would appear that no-one has taken the time to put all of them together to make a system that can be taught and used without any release of refrigerant into the atmosphere. This new idea does; it creates a reasonably cheap set-up that will empty the refrigeration system needing repair, and allow for pressure and evacuation tests to be carried out safely when the repair work is completed. The refrigerant charge can then be replenished if necessary before being pumped back into the now serviceable refrigeration plant. \

The refrigeration plants used hold a charge of either 1 or 2 kgs, depending on the date of their manufacture. The slight differences between the two types have been written in to the instructions. They are all built and designed by reputable refrigeration companies to the specifications given by both ClTB and City and Guilds. The set up shown can also be connected to domestic and larger industrial units with a few simple alterations.

The instruction manual states that ideas like these should be submitted before they become general knowledge. This idea has been in the making for almost two years but our pride would not let it go until we were certain it would work. It has been used in various guises throughout these two years to train RAF technicians in the art of refrigerant handling with zero release of refrigerant. The idea has been improved since its conception, up to the stage it is at now. For the trainees sake each stage has been written out thoroughly and with the extra help from the diagrams we are able to examine our trainees' abilities as they follow the

instructions to their successful conclusion.

We cannot design a perfect refrigeration system that will never leak; in the same way that we cannot make a perfect human being who will not make mistakes. As instructors at RAF St Athan we found it very difficult to teach the release of refrigerant as a good thing especially considering our larger system" use a recovery system with 10' long 3/" wide hoses. We do believe we can teach a zero tolerance to minimum leakage that can be practiced outside of the classroom and if made law can be easily upheld by the trained technician and enforced by the police and public alike. \

There is a second hand domestic appliance shop that does good deals on nearly new refrigerators, the front of the shop displays all of the almost latest models while in the lockup at the back of the shop a three foot high pile of refrigerator condensers covers the floor, waiting for the scrap man. With no recovery equipment in sight the only way these condensers can have been removed is by cutting the pipe and releasing the refrigerant to atmosphere. It is time this despicable practice was brought to an end.

Student PreDaration for the Practical 1: - This Refrigerant Handling Task is to be earned out after the student fully understands the operation and function of the component parts of their retngeration plant The familiansation handout Will help the student and a qualified instructor will be on hand to answer any questions All tasks must be successfully completed during a two- day practical session under standard workshop conditions with full supervision, following all of the necessary safeW precautions.

À Each student working alone is to set up his or her working area with, v' An R134a refrigerant trainer.

An 11134a refrigerant cylinder.

/ A set of serviceable electronic scales 150kg.

Personal protective equipment, to include, overalls, safety boots, impervious gloves and goggles.

One serviceable R134a refrigerant recovery pump.

A 4kg R134a refrigerant recovery still.

One cylinder of oxygen free nitrogen (OFN) complete with regulator.

Two 4 valve manifold gauge sets.

One quick release coupling.

A suitable leak detection kit (bottle of snoop).

/ A serviceable 62 cubic foot per minute vacuum pump.

Vacuum gauge calibrated in Torrs.

/ A Total test kit for R134a.

/ A standard workshop toolkit.

Student Instructions: - The following practical tasks are written in the correct order and are designed to cover all stages of refrigerant recovery from, and recovery back into, a serviceable Feedback or Polar Pumps 1 or 2kg Refrigeration Trainer, complying win and exceeding current European regulations EN 378.

Safety Warning: - If at any time you are instructed to stop cease work immediately and wait until a full explanation Is given, before carrying on.

1.5.1 Refrigerant Recovery from the Refrigeration Plant (1) (With an Empty Still (3)) The handout (Annex A) used to familiarise the student with the rig contains two exercises that give the student instructions on how to determine the quality of the refrigerant within their system. Question I explains the importance of checking gauges before running the unit and task No 6 explains how to deal ninth a non-condensable gas. The following tasks are designed to give the technician the ability to safely remove the tested refrigerant from a sealed serviceable system, so that it can be worked on. The refrigerant charge can be weighed, replenished, if necessary and re-used without any release of refrigerant to the atmosphere.

a) Zero the scales and measure the Tare weight of the still. (3) b) Determine if there is enough space available to take refrigerant charge from the trainer. (1) (Either 1 or 2 kg of R134a) Using the flexible hoses fitted to the manifold gauge sets, connect the recovery pump between the trainer and the recovery still in accordance with Fig 1.

* NOTE; THE RECOVERY Pl1MP (2) CAN TAKE REFRIGERANT IN EITHER FORM LIQlJlD OR VAPOUR, THE WAY IT lS RECOVERED DEPENDS ON THE TYPE OF TRAINER BEING USED. TllE OLDER RIGS ARE FITTED WITH A TAP VALVE ON THE OUTLET OF THE LIQUID RECIEVER, THE NEWER RIGS DO NOT, AND IIAVE TO BE CONNECTED VIA THE TWO-WAY SERVICE VALVE, FINED TO THE LIQUID RECIEVER. BOTH OF THESE VALVES WILL BE REFFERED TO AS Vl THROUGHOUT. ALSO NOTE THAT ON THESE NEWER RIGS THE REFRIGERANT WILL BE RE-INTRODllCED THROUGH A QUICK

RELEASE COUPLING AND THE SCHNEIDER VALVE CONNECTION FITTED

UPSTREAM OF THE FILTER DRIER. AS THE OPEN AND CLOSING

INSTRUCTIONS DIFFER SLIGHTLY STUDENTS WITH THE NEWER RIGS MUST

FOLLOW THE EXTRA SET OF INSTRUCTIONS WHEN THEY SEE THE ASTERISK

(*) FOR EXAMPLE.

* Check V1 is fully back seated. 1 2-

c) To ensure the integrity of the recovery circuit and to ensure the lines are free from any non-condensable gasses.

À Check V1 is closed.

* Check V1 is hilly back seated.

À Close M1.2, M2.1 and M2.2.

À Open all other valves.

The "spare', hose connected to M1.4 is fitted with a shut-off tap from now on it will be referred to as the fly hose. This hose can be moved between the various services used during the task. For example during the following tasks the fly hose at M1.4 will be moved between a Nitrogen cylinder, (5) refrigerant cylinder (6) and M2. 1 as necessary. To start with connect the hose to a nitrogen cylinder (5) via a pressure regulator. (Fig 1) WARNING; ALWAYS WEAR PROTECTIVE GOGGLES WlIEN DEALING WITlI NITROGEN UNDER PRESSURE.

d) Carry out an initial pressure test, with the Nitrogen, taking the pressure to between 15-30 lb/in2 if there are no obvious leaks increase the pressure up to 75 Ib/in2. Allow the pressure to hold for ten minutes, and then slowly release the Nitrogen through M2. I to a positive pressure of lb/in2. t3

e) The vacuum pump (7) can accommodate this positive pressure if introduced gently to it, so following the instructions given in the CITB Study Notes p48, (Annex B) evacuate the recovery system using the combined triple/deep vac method. For this task the fly hose will need to be moved between the nitrogen cylinder (5) and M2. l.

À During the final evacuation, the fly hose should be connected to M2.1.

À Close M1.4, its shut off tap and M2.1.

À Disconnect the hose from M2.1.

À Re-connect the fly hose to the vapour connection of an R134a cylinder. (Fig 2 Item 6) À With the vacuum pump (7) still running open M1.4 and the hose tap to pull any residual air from the line.

À Switch off the pump.

À Holding a good vacuum throughout, check M2.1 is closed. Close M1.2 and M2.2.

f) Slowly opening the vapour valve on the R134a cylinder, (6) introduce a vapour charge to the equivalent of 35 F-saturated pressure for Rl34a throughout the open recovery lines, and the vapour will act as a cushion for the liquid when it is introduced.

À Close all valve connections.

À Close the refrigerant cylinder's (6) vapour valve. 1Lt

g) The trainer's (1) reLngerant charge can be recovered from it as either a liquid or a vapour À Turn the three way switch to RILCOVllR À Open R2.

À Switch on the recovery pump. (2) À Empty the refrigerant vapour from M1.4 by opening R1, M1.3, M1.4 and the hose tap.

À Close the shut off tap and M1.4.

À Disconnect the hose from the refrigerant cylinder (6) and re!connect to M2.1.

WARNING; DO NOT OPEN M2.1 OR THE SBUT OFF TAP À Then in sequence open V1, M1.1, M1.3 and R1. The refrigerant will begin to move to the recover pump. (2) * Turn Vl to the mid position.

À Open M2.3, M2.4 and S1. The liquid refrigerant can now be observed in the sight glasses of the manifold gauges and the still (3) will start to fill up.

The refrigerant will be removed from the trainer (1) and the weight of the still (3) should increase by the amount stated on the trainer's data plate. I! the scales (4) do not increase by this amount ask for assistance from your instructor before taking any farther action.

À The pump (2) will automatically adjust between liquid and vapour as the trainer (1) empties.

À The recovery pump (2) will start to pull a vacuum in the suction side, when it does, close all valves in the same order as they were opened Closing R2 after switching off the recovery pump. (2) is h) When the recovery pump (2) is stopped trapped refrigerant will start to boil off inside the trainer's almost empty system increasing the pressure on the gauges. When the needle settles, re- start the recover pump (2) and using the same sequence pull the system into a further vacuum, this may take more than one attempt. When the needles hold steady, and with the valves still open (pump (1) ruining) carry out the following: À Close V1, M1.1, M1.3, and R1.

* Fully backseat Vl.

À Slowly turn the dial on the recovery pump (1) to SELF-CLEARING, the pump will empty itself of liquid and there will only be vapour left in the delivery lines.

À Close M2.3, M2.4 and S1.

À Switch off the recovery pump (1) and close R2.

i) When the fly hose was connected to M2. 1 air will have become trapped between the tap and the connection. To remove the air, À The suction side of the recovery circuit will be in a vacuum.

À Start the vacuum pump. (7) À Open M1.2, M1.4 and the hose tap.

À Listen for the change in tone from the vacuum pump. (7) À Close the hose tap, M1.4 and M1.2.

À Switch off the pump. (7) 1 1 j) The first two ports of manifold M2 will still contain refrigerant vapour, this vapour is preventing the use of the Torr gauge, (8) and these ports can now be emptied.

À Turn the three way switch to RECOVER À Open R2.

À Switch on the recovery pump. (2) À Open M2.1, M1.4, M1.3 and R1.

The refrigerant vapour will be safely stored in the hose between R2 and M2.3.

À With a vacuum registered in the suction side close M2.1, M1.4, M1.3 and R1.

À Switch off the pump (1) and close R2.

k) Keeping safety at the fore-front of our minds and to carry out the next part of the procedure without the risk of accidentally contaminating the stored refrigerant charge.

À Check V1 is closed.

* Check V1 is fully back seated.

À Disconnect M1.1, and remove the refrigeration trainer. (1) This will also free up the recovery circuit for the next student. Leave Ml, M2, the recovery pump (2) and the still (3) connected with all of the valves in the recovery circuit closed. The delivery side of the recovery pump (2) will still contain refrigerant under pressure.

À Move on to 1.5.3. )'1

1.5.2 Refrigerant Recovery from the Refrigeration Plant (1) (With a Pressurised Still (3)) The handout (Annex A) used to familiarise the student with the rig contains two exercises that give me student instructions on how to determine me quality of the refrigerant within their system. Question I explains the importance of checking gauges before running the unit and task No 6 explains how to deal with a noncondensable gas. The following tasks are designed to give the technician the ability to safely remove the tested refrigerant from a sealed serviceable system, so that it can be worked on. The refrigerant charge can be weighed, replenished, if necessary and re-used without any release of refrigerant to the atmosphere.

a) Check the condition of the recovery stills (3) contents using the comparator and total test kit.

If compatible with R134a. Zero the scales and measure the 'empty' weight ofthe still. (3) b) Determine if there is enough space available to take the whole refrigerant charge from the trainer (1) (Either 1 or 2 kg of R134a) complete the connections from the trainer (1) to the recovery still (3) in accordance with fig 1. I g

* NOTE; THE RECOVERY PUMP (2) CAN TAKI;, REFRIGERANT IN EITHER FORM LIQUID OR VAPOUR, THE WAY IT IS RECOVERED DEPENDS ON THE WE OF TRAINER BEING USED. THE OLDER RIGS ARE FITTED WITH A TAP VALVE ON THE OUTLET OF THE LIQUID RECIEVER9 THE NEWER RIGS DO NOT,AND HAVE TO HE CONNECTED VIA THE tWO-WAY SERVICE VALVE, FITTED TO THE LIQUID RECIEVER. BOTH OF THESE VALVES WILL BE REFFERED TO AS V1 THROUGHOUT. ALSO NOTE THAT ON THESE NEWER RIGS THE REFRIGERANT WILL BE RE-TRODlJCED THROUGH A QUICK

RELEASE COUPLING AND THE SCHRADER VALVE CONNECTION FITTED

UPSTREAM OF THE FILTER DRIER AS THE OPEN AND CLOSING

lNSTRUCTlONS DIFFER SLIGHTLY STUDENTS WITH THE NEWER RIGS MUST

FOLLOW THE EXTRA SET OF INSTRUCTIONS WHEN THEY SEE THE ASTERISK

(*) FOR EXAMPLE.

* Check V1 u fully back seated. q

WARNING 11: DO NOT DISCONNECT ANY IIOSES OR OPEN ANY OF THE VALVES AT TIIIS TIME, THEY WILL ALL BE CLOSED.

c) To ensure the integrity of the recovery circuit and to ensure the lines are free from any non-condensable gasses.

WARNING N.2: THE RECOVERY CIRCUIT FROM R1, R2, M2.3, M2.4, S1 AND TIIE STILL (3) WILL CONTAIN REFRIGERANT UNDER PRESSURE. THESE VALVES MUST REMAIN CLOSED FOR THE PRESENT TIME.

À Check V1 is dosed.

* Check Vl is fully back seated.

À M1.4 will be in a vacuum, disconnect it from M2.1, checking M2.1 is fully closed.

À Connect M1.4 to the nitrogen cylinder (5) and safely purge the hose.

À Open M1.1 and M1.3.

The "spare" hose connected to M1.4 is fitted with a shut-off tap from now on it will be referred to as the fly hose. Ilds hose can be moved between the various services used during the task. For example during the following tasks the fly hose at M1.4 will be moved between a Nitrogen cylinder, (5) refrigerant cylinder (6) and M2. 1 as necessary. To start with connect the hose to a nitrogen cylinder (5) via a pressure regulator. (Fig 1) WARNING No3; ALWAYS WEAR PROTECTIVE GOGGLES WHEN DEALING WITH NITROGEN UNDER rRESSURE.

d) Carry out an initial pressure test of Ml paying particular attention to the connection at Vl. With the Nitrogen, take the pressure to between 15-30 lb/in2 if there are no obvious leaks increase the pressure up to 75 lb/in2. Allow the pressure to hold for ten minutes, and then slowly release the Nitrogen through Ml. I to a positive pressure of 5 Ib/in2. so

e) lithe vacuum pump (7) can accommodate this positive pressure if introduced gently to it, so following the instructions given in the C1TB Study Notes p48; (Annex B) evacuate the recovery system using the combined triple/deep vac method. For this task the fly hose will need to be moved between the nitrogen cylinder (5) and M2. 1.

À During the final evacuation, the fly hose should be connected to M2.1.

À Close M1.4, its shut off tap and M2.1.

À Disconnect the hose from M2.1.

À Re-connect the fly hose to the vapour connection of an R134a cylinder. (Fig 2 Item 6) À With the vacuum pump (7) still running open M1.4 and the hose tap to pull any residual air from the line.

À Switch off the pump. (7) À IIolding a good vacuum throughout, check M2.1 is closed. Close M1.2 and M2.2.

f) Slowly opening the vapour valve on the R134a cylinder, (6) introduce a vapour charge to the equivalent of 350F-saturated pressure for R134a throughout the open recovery lines, and the vapour will act as a cushion for the liquid when it is introduced.

À Close all valve connections.

À Close the refrigerant cylinder's (6) vapour valve. Hi

g) The trainer's refiigerant charge can be recovered from it as either a liquid or a vapour À Turn the three way switch to RECOVER À Open R2.

À Switch on the recovery pump. (2) À Empty the refrigerant vapour from M1.4 by opening Rl, M1.3, M1.4 and the hose tap.

À Close the shut off tap and M1.4.

À Disconnect the hose from the refrigerant cylinder (6) and re-connect to M2.1.

WARNING No4; DO NOT OPEN M2.1 OR THE SHUT OFF TAI, À Then in sequence open V1, M1.1, M1.3 and R1. The refrigerant will begin to move to the recovery pump. (2) * Turn Vl to the mid position.

À Open M2.3, M2.4 and S1. The liquid refrigerant can now be observed in the sight glasses of the manifold gauges and the still (3) will start to fill up.

À The refrigerant will be removed from the trainer (1) and the weight of the still (3) should increase by the amount stated on the trainer's data plate. If the scales (4) do not increase by this amount ask for assistance from your instructor before taking any further action.

À The pump (2) will automatically adjust between liquid and vapour as the trainer (1) empties.

À The recovery pump (2) will start to pull a vacuum in the suction side, when it does, close all valves in the same order as they were opened Closing 112 after switching off the recovery pump. (2) h) When the recovery pump (2) is stopped trapped refrigerant will start to boil offinside the trainer's (1) almost empty system increasing the pressure on the gauges. When the needle settles, re-start the recovery pump (2) and using the same sequence pull the system into a further vacuum, this may take more than one attempt. When the needles hold steady, and with the valves still open (pump running) carry out the following: À Close Vl, M1.1, M1.3, and R1.

* Fully backseat Vl.

À Slowly turn the dial on the recovery pump (2) to SELF-CLEARING, the pump (2) will empty itself of liquid and there will only be vapour left in the delivery lines.

À Close M2.3, M2.4 and S1.

À Switch off the recovery pump (2) and close R2.

i) When the fly hose was connected to M2. 1 air will have become trapped between the tap and the connection. To remove the air, À The suction side of the recovery circuit will be in a vacuum.

À Start the vacuum pump. (7) À Open M1.2, M1.4 and the hose tap.

À Listen for the change in tone from the vacuum pump. (7) À Close the hose tap, M1.4 and M1.2.

À Switch off the pump. (7) j) The first two ports of manifold M2 willstill contain refrigerant vapour, this vapour is preventing the use of the Torr gauge, (8) and these ports can now be emptied.

À Turn the three way switch to RECOVER À Open R2.

À Switch on the recovery pump. (2) À Open M2.1, M1.4, M1.3 and Rl.

The refrigerant vapour will be safely stored in the hose between R2 and M2.3.

À With a vacuum registered in the suction side close M2.1, M1.4, M1.3 and R1.

À Switch off the pump (2) and close R2.

k) Keeping safety at the fore-front of our minds and to carry out the next part of the procedure without the risk of accidentally contaminating the stored refrigerant charge.

À Check V1 is closed.

* Check V1 is fully back seated.

À Disconnect M1.1, and remove the refrigeration trainer. (1) This will also free up the recovery circuit for the next student. Leave Ml, M2, the recovery pump (2) and the still (3) connected with all of the valves in the recovery circuit closed. The delivery side of the recovery pump (2) will still contain refrigerant under pressure.

À Move on to 1.53.

1.53 Pressure Testine WARNING; ALWAYS WEAR PROTECTIVE GOGGLES WHEN DEALING WITH NITROGEN UNDER PRESSURE.

a) Having disconnected the trainer, (1) reconnect it to the Nitrogen cylinder's (5) regulator using a single high pressure hose c/w tap. (Fig 3) À Purge the Nitrogen high-pressure hose, and with the trainers system empty.

À Open V1 * Turn V1 to the mid position, b) Introduce a positive pressure of 2 lb/m2 of Nitrogen into the trainer. (1) (This will prevent the ingress of moisture and air when the system is broken into.) Break into the system by checking the oil level, changing the filter drier or carrying out any necessary repairs.

c) On completion of the maintenance task a pressure test must now be carried out on the refrigerant trainer. (1) À Pressurise the system to between 130 lb/in2. Check for any obvious leaks.

For training purposes carry out a strength test of the trainer (1) equating to 1<A/P<13 (Allowable Pressure up to 1.3AIP) À Observing both gauges on the trainer, (1) slowly build up the pressure to 100 lb/in2.

Fully front seat the low pressure service valve.

À With the low pressure side isolated increase the Nitrogen pressure on the high side up to 120 lblin2.

À Close off the Nitrogen cylinder. (5) À Both gauges will eventually equalize through the head, when they do and you are satisfied there are no leaks; reduce the system pressure to 7S lb/in2 equalizing both the high and low sides together.

d) With the whole system held at a pressure of 75 lb/in2 the pressure test can be carried out.

À Fully front seat the low-pressure service valve.

À Increase the high side pressure to 135 lb/in2 À Close V1.

* Check V1 is fully back seated.

Note: Each time the system is pressurised use leak detector (Snoop) around the joints À Leave the system sealed under these pressures for a minimum of 1 hour preferably 12 hours to prove it is sound.

Hopefully at the end of day one each student should have reached this stage 2i 1.5.4 Day Two: The combined TrinIe/Deep Vac a) After the elapsed time check the system has maintained its pressure on the gauges.

À Slowly release the pressure in the high side by opening V1 and releasing the pressure through the hose down to 75 lb/in2.

À Turn the trainer's (1) compressor, low-pressure service valve to the mid position.

If there are no leaks there should be no movement of the gauges, any movement will require further investigation.

À If satisfied reduce the system pressure to 5 lblin2.

À Close V1.

* Fully back seat V1.

b) Re-connect the trainer (1) to the recovery circuit via V1. (Fig 4) To remove any moisture or non condensable gasses from the circuit prior to recovering its refrigerant charge a combined triple/deep evacuation will need to be carried out successfully on it. The vacuum pump (7) can accommodate the positive pressure of 5 lb/in2, if introduced gently to it, so following the instructions given in the C1TB Study Notes p48, (Annex B) evacuate the recovery system using the combined triple/deep vac method. For this task the fly hose will need to be moved between the nitrogen cylinder and M2. I. À During the final evacuation, the fly hose should be connected to M2.1.

À Close M1.4, its shut off tap and M2.1.

À Disconnect the hose from M2.1.

À Re-connect the By hose to the vapour connection of an R134a cylinder. (Fig 5 Item 6) * Fully backseat V1 and close Ml.1 * Disconnect the hose from V1 and attach the valve of a quick release coupling. (QRC) * NOTE: The Quick Release Couplings come in two parts, Valve and Socket. The spring loaded valve should prevent any release from the system when connected to a Sehrader connection. Be aware that these valves can fail during a vacuum; they must be disconnected as soon as possible after they have done their bit.

* Connect the socket of the QRC to the Schrader valve upstream of the liquid line shut off valve.

À With the vacuum pump (7) still running open M1.4 and the hose tap to pull any residual air from the line.

* With the vacuum pump (7) still running open M1.4 and the hose tap to pull any residual air from this line. Also open Ml.l pulling a vacuum up to the QRC.

* Connect Ml.l to the socket of the QRC when a vacuum is felt.

À Switch off the pump. (7) À Holding a good vacuum throughout, check M2.1 is closed. Close M1.2 and M2.2.

c) Slowly opening the vapour valve on the R134a cylinder, (6) introduce a vapour charge to the equivalent of 35 F-saturated pressure for R134a throughout the open recovery lines and the trainer's circuit, (1) the vapour will act as a cushion for the liquid when it is introduced À Close all valve connections.

À Close the refrigerant cylinder's (6) vapour valve.

AL

1.5.5 Refrigerant Recovery a) Confirm the net weight of refrigerant in the still by reading the scales; from the trainer's (1) data plates determine how much is needed for the transfer À Fully front seat the refrigerant trainer's (1) receiver service valve.

* Close the liquid line shut off valve.

À The hose connected to M1.4 will still contain refrigerant vapour, as it needs to be connected to M2.1. Start the trainer's (1) condenser fan, compressor and evaporator fans.

À Open V1, M1.1, M1.4 and its hose tap.

* Open Ml.l, M1.4 and its hose tap.

À When a vacuum shows on the gauge close the valves from the cylinder (6) to the trainer (1) and switch off the trainer. (1) À Disconnect M1.4 from the refrigerant cylinder (6) and re-connect to M2. 1 WARNING; DO NOT OPEN M2.1 OR THE SHUT OFF TAP it" b) When the fly hose was connected to M2. 1 air will have become trapped between the tap and the connection. To remove the air, À The suction side of the recovery circuit will be in a vacuum.

À Start the vacuum pump. (7) À Open M1.2, M1.4 and the hose tap.

À Listen for the change in tone from the vacuum pump. (7) À Close the hose tap, M1.4 and M1.2.

À Switch off the pump. (7) c) Now the refrigerant can be introduced back into the trainer. (1) À Open S1, M2.4, M2.1, the hose tap, M1.4, M1.1 and V1.

À Allow the liquid to settle observing the drop in weight, start up the trainer's (1) condenser fan, compressor and evaporator fans, activating the low-pressure by-pass at the same time.

À The trainer's (1) compressor will pull the charge through its own circuit, storing it into its receiver.

À When the difference in weight has registered on the scales.

À Close S1 and pull a vacuum up to M2.4, close M2.4.

À Pull a vacuum up to M2.1, open R2 and remove any vapour trapped inside the recovery pump, (2) then close M2.1.

À Close the hose tap, pull a vacuum up to M1.4 and close M1.4. 3o

À Open M1.3 and pull any vapour from the recovery pumps (2) suction line, and then close M1.3.

À Close M1.1 and close V1 as the vacuum is shown.

* Follow the instructions above but instead of closing V1 disconnect the QRC and open the shut off valve.

d) Disconnect the trainer (1) from the recovery circuit.

À Open the liquid receiver service valve.

* The receiver service valve should already be fully back seated.

À Allow the system to reach its operating parameters, replace all blanking caps, and carry out a full functional test checking the gauge readings for any inconsistencies.

e) Completion of the task.

À Check all refrigerant log tables have been completed correctly.

À Tidy all tools away.

À Sign for having completed the task on the relevant job card.

Brief explanation of the diagrams Fig 1. Connections to be made between the trainer (1) and the still (3) these connections allow for triple/deep evacuation of recovery circuit and leak testing.

Fig 2. Connections for the introduction of a vapour into the recovery circuit and for the recovery of the trainers ( I) refrigerant charge into the still.

Fig 3. Connection to be made to free up recovery circuit and to pressure test the repaired/empty trainer ( I) Fig 4. Connections to be made to carry out combined triple/deep evacuation of the serviceable, empty trainer ( I) Fig 5. Connections for the introduction of a vapour into the recovery circuit and trainer and for recovery of the refrigerant back into the trainer (1) from the still (3) after the charge has been replenished. 32.

pack l or] . Refrigeration and Air Conditioning Trainine Equipment Familiarisation The procedures in this handout have been written to assist students to set up practical tasks that will enhance their knowledge of refrigeration principles, enforcing the knowledge gained from theoretical lessons taught in class. Culminating in the removal and recovery of the systems charge to and from the training plant. To this end each task contains a number of questions that will test the students understanding of the processes involved.

Students will be able to introduce deliberate faults identical to those met when servicing equipment of this type in the field. It is important that the units be returned to full working order on completion of each task, if not then misleading results will be obtained from that point on causing additional problems. Instructors will be available to supervise help and check the results from each task before the next can be started.

All of the Feedback units are charged with lKg of R134a refrigerant, the Polar Pumps trainer is charged with 2kg of R134a. To protect the units the high-pressure cutouts have been set at lb/in2 for the Feedback systems and 250 lb/in2 for the Polar Pump system. The low- pressure cut outs have been set at between 20-30 lb/in2 for the Feedback systems and 25 lb/in2 for the Polar Pump system Q1. What temperatures in F do these figures equate to for R134a? Ans.

The units have been fitted with pressure limiting expansion valves that prevent the evaporator's pressure rising too high. The air-cooled condensers have been sized such that the discharge pressure will correspond to 335 F above ambient.

Q2. What would be the condensing pressure considering today's ambient conditions? Ans.

AT

Refrigeration and Air Conditioning Training Equipment Familiarisation Task No 5 Bad maintenance practices It is always important to make sure all of the systems components are free from obstructions.

Q10. Explain what would happen if the condenser fins were to become blocked after a sand storm in the desert? Ans.

Prove your answer by blocking the condenser with the board, noting your results below.

Task No6. The Introduction of a Non- Condensable Gas Non-condensable gasses can effect the operation of refrigeration circuits.

Q11. Give an example of a Non-Condensable Gas, explaining what noncondensable means? Ans.

Q12. Explain what effects a Non-Condensable Gas would have on a refrigeration systems operating parameters and why? Ans. 3Ll

Refrigeration and Air Conditioning Training Equipment Familiarisation Q13. What symptoms would you expect to see from a refrigeration plant with a non condensable gas? Ans.

Q14. How would you identify the presence of a non-condensable gas within a system? Ans.

Q15. What actions would you take to rectify the problem? Ans.

Task No7 Effects of a low charae With the compressor running and using the Liquid Receivers service valve and a refrigeration spanner, close the valve fully and turn the valve back 'id: a turn. Keep an eye on the gauges, note the pressures once they have settled and explain the results by using the temperature probe on the outlet pipe of the evaporator calculate the temperature of the air coming off it. Re-open the valve fully. Note your results below. t

(.611 mung 6.6 Practical Considerations The following are some general guidelines to follow when evacuating and dehydrating refrigeration and air-conditioning systems: À use a good quality, two-stage gas ballast vacuum pump À use a pump with a capacity to match the system À regularly change the pump oil À use large diameter, short connecting lines À connect the pump to both sides of the system À use an accurate measuring device Methods of Evacuation and Dehydration There are two generally recognised methods for the evacuation and dehydration of refrigeration systems. These are: 1. triple evacuation method ('triple-vac') 2. deep vacuum method ('deep-vac') The 'triple-vac, method is so named because this is the minimum number of times the sequence should be carried out to effectively remove H20 vapour and other undesirable gases from the system/plant.

The deep-vac' method is carried out when the system is known to be dry, i. e. when triple-vac' has been carried out satisfactorily.

Triple Evacuation Using the chart on page 49, choose the mean plant temperature'. For this exercise, we will use 10 Celsius. (At this temperature, water vaporises at about 10 torn) The method below, using the pressures stated, is a combination of triple-vac followed by deep-vac methods.

1. Evacuate to 10 Torr from both service valves.

At this pressure, any HERO will vaporise.

2. Break vacuum with O.F.N. into discharge service valve to 1.1 bar abs.

This wig sweep any vapour and unwanted gases before it.

3. Evacuate to 5 Torr from suction service valve.

This will motivate those vapours towards the suction valve and atmosphere.

4. Break vacuum with O.F.N. into discharge service valve to 1.1 bar abs.

This will sweep any remaining vapour and unwanted gases before it.

5. Evacuate to the lowest pressure that the pump will achieve.

Repeat 4 and 5 if necessary to achieve maximum vacuum.

The plant should now be sufficiently dehydrated and suitable for recharging. 3C

Claims (7)

1. A refrigerant recovery system that will recover refrigerant to and from a serviceable refrigeration trainer without any release of refrigerant to atmosphere.

2. A refrigerant recovery system is claimed in claim 1 that is compatible with in use training rigs, to qualify students in the skins of refrigerant handling. In accordance with and exceeding the instructions detailed by Cib and Guilds and The Construction and Industry Training Board.

3. A refrigerant recovery system is claimed in claims 1 and 2 that can be constructed using off the shelf component parts.

4. A refrigerant recovery system is claimed in claim 1 that requires the minimum of connections and reconnection to carry out all of the recovery and testing tasks related to the repair of a sealed vapour compression circuit.

5. A refrigerant recovery system is claimed in claims 1,2,3 and 4 that guarantees 100% recovery of the refrigerant charge with zero release of refrigerant to atmosphere, within the training environment.

6. A refrigerant recovery system is claimed in claims 1,2,3,4 and 5 that can be used by the trained refrigerant technician with a guaranteed 100% recovery of the refrigerant charge with zero release of refrigerant to atmosphere.

7. A refrigerant recovery system is claimed in claims 1,2,3,4,5 and 6 that could mean the beginning of the rebuilding of the earths damaged atmosphere and the end to extremes of climate.

Key to Fieures 1-5 (1) A serviceable R134a refrigerant trainer.

(2) A serviceable R134a refrigerant recovery pump. Complete with self clear function.

(3) A 4kg refrigerant still capable of holding R134a (4) A serviceable set of 1OOkg scales.

(S) A cylinder of oxygen free nitrogen, complete wit refrigerant regulator.

(6) A suitable R134a refrigerant cylinder.

(7) A serviceable 6.2 cubic foot per minute vacuum pump.

(8) A vacuum gauge calibrated in Torrs.