10 - Equipment and Instruments for Refrigerant Handling and Service Flashcards
How do spring operated relief valves, rupture disks, and fusible plugs operate?
Spring-Operated relief valves open under excessive pressure, and then close again when enough refrigerant has been released from the cylinder to lower the pressure.
Rupture disks are designed to open under excessive pressure, but do not close again. They will release the entire charge into the atmosphere.
A fusible plug is made of a metal with a low melting point, which melts and releases a cylinder’s entire refrigerant charge if the cylinder begins to overheat.
When should a refrigerant cylinder have a pressure release protective device, and what should they be?
Cylinders that have a diameter of 4 1/2” or greater and a length of 12” or more must have a pressure release protective device. This device can be a rupture disc, a fusible plug, or a spring-operated relief valve. These are designed to allow refrigerant to escape from a cylinder when the pressure or temperature is too high.
Who prescribes the regulations for refrigerant cylinders?
The Department of Transportation (DOT)
How often should cylinders be inspected and re-certified?
Cylinders with a corrosive refrigerant must be inspected and recertified every five years. Cylinders with non-corrosive refrigerants, every ten years.
What are the three main types of refrigerant cylinders?
Storage cylinders, disposable cylinders, and recovery cylinders.
What is a storage cylinder?
Large storage cylinders are used to charge refillable service cylinders at the shop. Often, the storage cylinders are positioned upside down with the valve at the bottom to make filling a service cylinder easier and faster.
What is a disposable cylinder?
Disposable service cylinders are one of the most commonly used types of refrigerant container. They are designed for one use only. They are used to charge refrigerants into a system. They should be stored at temperatures below 125 to prevent refrigerant pressure buildup. They can be used to charge with vapor (valve side up) or liquid (valve side down).
How should disposable cylinders be disposed of?
All refrigerant must be recovered into an approved recovery cylinder. The cylinder must be evacuated down to atmospheric pressure. The cylinder may then be disposed of or recycled. Many refrigerant supply stores offer recycling of used disposable cylinders.
What are Recovery cylinders?
Recovery cylinders are refrigerant cylinders specifically dedicated to storing refrigerant recovered refrigeration systems. Each cylinder is dedicated to only one type of refrigerant. These cylinders are easily recognized by their gray paint on the lower portion and yellow paint on the upper portion.
How often should a recovery cylinder be tested.
Over 300 psig, every five years. Under 300 psig, every ten years.
What are pressure gauges?
Pressure gauges are instruments that measure and display the pressure of a fluid in a container.
What is a bourdon tube?
A bourdon tube is a thin walled tube of elastic metal bent into a circular shape that straightens as pressure inside it increases. One end of a bourdon tube is sealed closed, while the other end is connected to a fitting that connects into a valve on a refrigeration system. With the sealed end connected to a linkage and a specially engineered gear with an indicator needle, a bourdon tube’s reaction to pressure indicates pressure on a given scale.
What is a retarder?
A retarder allows a gauge to measure pressure readings at higher pressures . After the pressure has crossed a certain pressure threshold, a retarder engages an extra spring that correlates with the gauge’s higher graduation markings.
What are the three main types of pressure gauges used in HVACR service work?
1 - Vacuum gauges (30” hg vacuum through 0” hg vacuum)
2 - Compound gauges (30” hg vacuum through 240 psi)
3 - High-pressure gauges (0 psi through 800 psi)
What is a vacuum gauge?
A vacuum gauges measures lower than atmospheric pressure.
What is a micron?
A micron is the equivalent of 0.001 mm hg.
What is the difference in vacuum measurement between microns and in hg?
A deeper vacuum measured in microns will correspond to a decreasing value of microns. A perfect value measured in microns is 0, with the value increasing as pressure is added. Vacuum measurements in hg in will increase once pressure decreases past atmospheric pressure (29.92 in hg) from 0 in hg vacuum, until a perfect vacuum is reached at 29.92 in hg vacuum. (in hg and in hg vacuum are inverse one pressure deceases past atmospheric pressure)
How is a vacuum used to remove water from the inside of a refrigeration circuit?
A vacuum of 250 microns will decrease the pressure enough to cause liquid water to evaporate and be drawn out of the system. To measure such a low pressure, a vacuum gauge must be used, as a compound gauge will not be able to accurately measure a deep vacuum.
How can a technician determine if water is present inside a system?
If a vacuum is drawn out of the system and the vacuum levels off at 5000 microns, ice or water is in the system.
How can a thermistor vacuum gauge be cleaned?
- Fill the tube with cleaning solvent using a eyedropper.
- Rock the tube gently, and empty it when finished
- Repeat steps 1-2 two or three times.
- Clean with an alcohol rinse.
- Clean the instrument dial cover with soap, water, and facial tissues.
What is a compound gauge
A compound gauge measures pressure above atmospheric and also vacuum. It is also known as a low-side gauge. It is compound because it measures both above and below atmospheric pressure.
What is a high pressure gauge?
A high pressure gauge is a pressure gauge that can read high pressure values on a single continuous scale.
How can a gauge be calibrated?
Disconnect the gauge so that it is open to the air. Set the indicator needle to 0.
What is the difference between psi, psia, and psig?
PSI is the most basic form of measurement. It stands for pressure per square inch. Most pressure transducers are measured in psi.
PSIA is absolute pressure, and scales up from a perfect vacuum.
PSIG is relative to atmospheric pressure, and will increase from there. Any decrease will be measured in psig vacuum or psiv.
What is a service valve?
A service valve is a valve with a wrench operated movable valve stem that blocks or opens passage trough the valve. The service valve also blocks or opens a service port, which provides a connection to the refrigeration system for taking pressure readings and adding or removing refrigerant or lubricant. Service valves enable technicians to seal off parts of the system while installing gauges or recharging or evacuating the system.
What are the four different valve positions?
Back seated, front seated, mid position, and cracked open.
What is the function of a back seated service valve?
If the valve stem is turned counterclockwise (outward) as far as possible, the valve is back seated. This closes off its service port from the rest of the system, so no pressure readings or procedures can be performed. This is used for normal system operation.
What is the function of a front seated service valve?
If the valve stem is turned clockwise (inward) as far as possible, the valve is front seated. When a service valve is front seated, it blocks the flow of refrigerant through the valve by closing off it’s regular passageway. Front seating a service valve provides a passage between part of the refrigeration system and the service port.
What is the function of a mid position service valve?
When the valve stem is turned so that the valve is not against either seat but midway between the front and back, the service valve is in mid-position. This is usually done by beginning with the valve in the back-seated position and turning the valve stem two complete clockwise rotations. This position accomplishes two objectives: it allows refrigerant to continue flowing, and it provides a connection between the rest of the system and the service port.
What is the function of a cracked open service valve?
A service valve is cracked open when the valve stem has been turned just enough to lift the valve off the back seated position. This allows refrigerant to continue flowing while providing a connection between the rest of the system and the service port.
What is a suction line service valve?
This is a low side service valve connected to a refrigeration system’s suction line. In many cases, a suction line service valve is located much closer to the compressor’s inlet than to the evaporator. These are often found on the condensing unit of a split system. During normal system operation, cool low-pressure vapor refrigerant flows through this valve.
What is a suction service valve? (SSV)
This is a low side service valve that connects to the suction line and directly onto the compressor at its inlet. Valve caps protect the service port and valve stem when the valve is not in use. It is considered a compressor service valve because it is one of the two service valves connected directly onto the compressor.
What is a discharge service valve? (DSV)
This is a high side service valve that is mounted at a compressor’s discharge port, providing a shutoff between the compressor and the condenser. It also provides a service port for a high pressure gauge or a gauge manifold. During normal operation, hot, high pressure refrigerant vapor flows through this valve. This valve is considered a compressor service valve.
What is a liquid line service valve?
This is a high side service valve located in a refrigeration system’s condenser and liquid line. In many cases, a liquid line service valve is located much closer to the condenser’s outlet than to the metering device. These service valves are often found on the condensing unit of a split system. During normal system operation, warm high
What is a liquid receiver service valve? (LRSV)
A liquid receiver service valve, or queen valve, is a high side service valve connected to the outlet of a liquid receiver and the inlet of a liquid line. These valves enable the technician to charge liquid refrigerant into the system.
Where is the queen valve, and what is it useful for?
The queen valve is installed between the condenser and the liquid receiver inlet. King and queen valves are useful when pumping down systems for component isolation.
What is valve packing?
Valve packing is a string sealant that creates a pressure seal between the inside and outside of a valve, preventing fluid from leaking out. It’s made up of rings of resilient or semi-resilient material that are placed around the valve’s stem or shaft and push against it and the valve body to create the seal.
What is a valve gland?
A valve gland is a mechanical seal that compresses packing material around a valve stem or shaft to create a barrier that prevents fluids or gases from escaping. This compression creates a leak-free seal that allows machinery to operate smoothly and efficiently.
What is a valve stem?
A valve stem is a self-contained valve that opens to admit gas to a chamber, and is then automatically closed and kept sealed by the pressure in the chamber, or a spring, or both, to prevent the gas from escaping.
What are the four key points to keeping a service valve in good working order?
- Keep the valve body free of moisture to prevent rusting on the stem
- Match the correct service valve wrench size to the valve stem to prevent stripping of the valve stem head.
- Maintain the packing so that the service valve will not leak: occasionally tighten the packing head
- Oil and seal the threads of the service port each time gauges are used and caps are replaced.
How can risk be minimized when opening a stuck service valve?
Always use a fixed wrench rather than a ratchet wrench. This is done so the valve can be quickly closed again if a leak or breakage occurs.
How can a technician avoid valve stem freezing?
After back seating a valve, turn it just enough to relieve some of the pressure on the seat, but not enough to open the valve. This provides just enough clearance between the valve and it’s seat to prevent it form getting jammed into its seat if the valve body contracts.
How can a stuck service port plug be loosened?
Heat the outside of the service valve body with a flame from a torch. Be careful not to overheat it, it should not glow. After the threads are loosened, use a wrench to gently turn and loosen the plug.
What is an access port?
An access port is a small valve opening that usually contains a schrader valve core and is used for checking pressure and servicing a system.
What is a bypass valve?
Discharge Bypass Valve is used to bypass a portion of the hot discharge gas directly into the low side to limit the minimum evaporating pressure during periods of low load either to prevent coil icing or to avoid operating the compressor at a lower suction pressure than it was designed to operate.
What is a hot gas defrost valve?
In hot gas defrost, refrigerant vapor from either the compressor discharge or the high pressure receiver is used to warm the evaporator coil and melt the frost that has collected there. The vapor condenses to a liquid during this process, and is then routed back to a protected suction line or to an accumulator. It’s often used in commercial appliances like ice machines and freezers.
What is a schrader valve?
A schrader valve consists of an externally threaded, hollow tube with a spring loaded, coaxially centered pin that blocks access through the tube. The tube can be opened by depressing the pin against the spring pressure.
What are schrader valve cores?
Having external threads allows schrader valves to be used as valve cores inside access ports. This allows a valve core to be removed from an access port for certain procedures, such as pulling a vacuum.
What are piercing valves?
The most common method used to gain access to small hermetic systems or those without access ports is to use piercing valves. A piercing valve is a valve that is secured to a length of tubing and accesses the refrigeration system by piercing through the tubing
What are the pros and cons between a bolted on and brazed on connection?
Bolted on piercing valves do not require refrigerant removal prior to installation, but their seal may leak over time in systems with large vibrations. They should be used as temporary access to the system.
Brazed on piercing valves seldom leak, but they do require refrigerant removal prior to brazing.
What are the three criteria that must be followed when selecting a bolt on piercing valve?
- The rubber or nylon seal should be clean
- The tubing should be straight and clean
- The correct diameter valve must be selected for the correct diameter tubing
What is the nine step procedure to installing a bolted on piercing valve?
- Assess the location where the valve will be installed: Make sure there is enough space around the tubing to operate and install the valve, make sure hoses can be easily attached.
- Make sure the part of the tubing you intend to install the valve on is straight, round, and free of any dents or irregularities
- Clean the area with a fine emery cloth or fine sandpaper. Be careful to not scratch the tubing while cleaning. Wipe it clean when done with a clean cloth to remove any dust.
- Back out the valve’s piercing needle as far as it will go
- Dab a little nylog on the tubing.
- While holding the sealing washer steady to be sure it stays in place, mount the valve on the tubing. Secure the valve body too the tubing by tightening the screws evenly and snugly.
- Once the valve body is firmly clamped to the tubing, attach the service hose and rotate the piercing valve stem clockwise into the tubing. It will become easier to tighten when the needle pierces the tubing
- Back off the piercing needle slightly in order to access the system
- Test for leaks to make sure the seal is airtight between the piercing valve and tubing.
What is the eleven step procedure to installing a brazed on piercing valve?
- With the size of the piercing valve in mind, check to see if there is enough space around the tubing to install and operate the piercing valve. Also make sure there will be enough room to attach service hoses.
- Ensure the area of tubing you intend to install the valve on is straight, round, and without any dents or irregularities.
- Clean both the saddle and tubing mating surface with clean sandpaper or clean steel wool. Wipe both the saddle and the tubing with a clean cloth to remove any dust.
- Remove the piercing valve stem and the gasket from the saddle.
- Brazing requires flux or flux-coated filler rod. If using a flux-coated filler rod, mount the saddle on the tubing. If not using a flux-coated filer rod, apply clean, fresh brazing flux on the saddle according to the valve manufacturer’s directions. Then mount the saddle on the tubing. To prevent the saddle from moving during the brazing process, a small c clamp can be used to secure it in place.
- Check to see if there is enough room for using the valve in its present location. If there is not, find a more suitable location with better clearance.
- Using a torch, heat both the tubing and saddle until the filler rod material flows around the saddle. Do not overheat the tubing or it may be weakened to the point of failure and burst. (note: ensure nitrogen is flowing during the brazing process to prevent porosity in the weld)
- When you have finished brazing the joint, inspect it carefully. Use a mirror to check hard to see edges
- After the brazed joint has cooled, install the piercing needle and gasket. Many piercing valve caps have O-rings. These seal the system. O-rings must be in place before installing the cap to ensure a proper seal. Caps with a metal-to-metal seal must be tightened one-eighth of a turn with a wrench after being finger tightened. Can be sealed additionally with Nylog.
- Attach the service hose and then back off the piercing valve stem slightly to access the system.
- Test for leaks to make sure the seal between the piercing valve and tubing is airtight.
What is a gauge manifold?
What is it used for?
A gauge manifold consists of a compound (low-side) gauge, a high-pressure (high side) gauge, and at least three ports that may be isolated form each other, and at least two hand valves.
A gauge manifold allows a service technician to check the operating pressures of both the low side and high side simultaneously, to add or recover refrigerant, to add oil, to bypass the compressor, and to perform many other service operations.
What is the 6 step process to purging a gauge manifold and hoses?
- Before beginning, make sure all gauge manifold valves and system service valves are closed.
- Connect the center service line to a refrigerant cylinder containing the same refrigerant used in the system.
- Remove the service caps from the systems access ports, and loosely connect the gauge manifold’s lines for purging.
- Open the low and high side valves on the gauge manifold.
- Briefly crack open the cylinder valve on the refrigerant tank to flush the gauge manifold and service lines with refrigerant. Any moisture or air will be forced out of the loose connections at the service ports.
- Close the cylinder valve and tighten the service line fittings at the access ports.
What are the six different methods of leak detection?
- Bubble Solutions
- Fluorescent Dyes
- Refrigerant Dyes
- Halide Torches
- Electronic Detectors
- Ultrasonic Detectors
What are some tips to remember when conducting a leak search?
- Check connections: Tubing connections and brazed areas, especially high stress/vibrations such as near a compressor
- Look for Oily or Dusty areas
What is the EPA Leak Repair Standard for Commercial/Industrial refrigeration and comfort cooling?
If a system contains more than 50 lbs of refrigerant and has yearly leak rates at or above trigger levels, a repair is required within 30 days. (35% for commercial and industrial equipment, 15% for comfort cooling and other appliances) These requirements do not apply to systems containing 50 lbs or lower.
How does the bubble solution leak detection method work?
What are its pros and cons?
What is an important quality tip to remember when using bubble solution?
It is a soap-water or solution that is brushed/sprayed over an area of tubing. If there is a leak, bubbles with form. It is useful for pinpointing the exact location of a leak
A bubble solution is low-cost and easy. It will also not react to the refrigerant used in Urethan insulation. However, a large high pressure leak can blow through the solution and no bubbles will appear.
(Note: wipe bubble solution off of ACR tubing when finished to avoid oxidization. When using soap bubbles or refrigerant dye, operate the system prior to leak detection to build pressure.)
How does the Refrigerant/Fluorescent Dye detection method work?
What are its pros and cons?
What is an important tip to remember?
It involves charging a dye into a refrigeration system and observing areas suspected of leaks during operation. Most leaks will show after a short time, however it may take longer (24 hours) to indicate leaks, especially if it is very small. Fluorescent dyes show up under ultraviolet light.
The biggest advantage of fluorescent dye is that there are no false alarms, if you see the dye, there is a leak. Unfortunately, wind and bright sunlight can make detecting small leaks hard. Excessive use of dyes can also reduce a refrigerant’s cooling capacity, lower lubricant viscosity, and even damage internal components in high concentrations.
(Note: always use dye that is compatible with the refrigerant in the system. Also, block out bright lights when using color changing methods)
How does the Halide Torch detection method work?
\What are its pros and cons?
Halide torches burn a flammable gas over a copper strip, while supplying the flame with oxygen through a siphon hose. When most gases burn with a copper strip placed inside the flame, it will turn green in the presence of the tiniest amount of halogenated refrigerant. (All CFC, HFC, and HCFC refrigerants contain halogen) If the flame turns green, a refrigerant leak is near the inlet of the rubber hose.
Halide torches are no longer commonly used. They can be difficult to use in the presence of wind or bright sunlight, and will throw a false reading when used near urethane insulation, as it contains some refrigerant chemicals as an expander. It can however be used to success when combined with a bubble solution to pinpoint the exact location.
How does the Electronic Leak detection method work?
\What are its pros and cons?
They use electronic sensors to determine if a refrigerant is present. They are often able to detect very small leaks. The detector is first dialed in to atmospheric pressure, then a probe is passed over surfaces suspected of leaking. A small pump draws air into the unit through the probe, and if a small amount of refrigerant is detected, the detector will emit a flash and audio cue.
ELDs can be thrown off by drafts. Shut off any fans that cause air movement. The tip can become contaminated by water or other substances, and this will interfere with its operation. A plastic guard tip should be used in these situations. They should also not be used near areas containing explosive or flammable vapors. ELDs will also throw a false reading when used in the presence of urethane insulation.
Always position the sniffer below the suspected leak, since refrigerant is heavier than air. Move the tip slowly at a rate of about one inch per second.
How does the ultrasonic leak detection method work?
\What are its pros and cons?
These detect the sound that a vapor makes as it is escaping from a pressurized system.
It is compatible with all refrigerants. However, background noise produced by equipment not related to the system can sometimes produce false alarms. Turn off any noise producing equipment when operating an ultrasonic detector
What is a vacuum pump?
It is a vapor pump used to create vacuums for evacuating a refrigerant system of moisture and other contaminants before refrigerant is recharged into the system.
How many microns due manufacturers usually recommend a system be vacuumed down to before charging?
500 microns.
What is ultimate vacuum?
Ultimate vacuum is the highest vacuum that a vacuum pump can pull. It is the most important specification of a vacuum pump and is usually measured in microns.
What is free air displacement? What is it measured in, and what is an alternative name for it?
What are the recommended pump capacities for residential, medium, and large systems?
It is the speed at which gas may be pumped through a vacuum pump. It is measured in CFM. It may also be known as volume capacity.
1.5 cfm - 3 to 5 ton residential systems
3-5 cfm - 5 to 100 ton medium systems
10-15 cfm - large systems over 100 tons
What are the two main types of vacuum pumps?
What are the applications of both?
Single stage and multi stage
Single stage uses a single pump mechanism to draw a vacuum. These can only be used when the triple evacuation method is used.
Two stage vacuum pumps consist of two pump mechanisms working in series. Working together, they are able to draw a vacuum more efficiently than a single pump mechanism. These are used when the deep vacuum method is used.
What is the purpose of oil in a vacuum pump?
How does pump oil interact with system contaminants?
It is used as a lubricant for the pump and as a fluid seal between air, gases, and contaminants entering the pump from the refrigeration system.
During evacuations, gases and water vapor pulled from the system often become trapped in the oil, which raises the oil level in the pump. Oil should be replaced frequently since oil rapidly becomes dirty when water and solvent vapor are drawn and dissolved into it.
What can dirty oil do to a vacuum pump? How can you tell if the oil is dirty?
Water will turn the oil white and foamy. If contaminated oil is left in the pump, sludge will form, reducing the service life of the pump. If pump oil is clear, it means it is clean. Dirty oil also reduces a pump’s ultimate vacuum.
What is the 7 step process to testing a vacuum pump?
- Using a tee fitting, connect an electronic vacuum gauge between the vacuum pump and the center port of a gauge manifold.
- Close the low and high side gauge manifold valves.
- Start the vacuum pump.
- Allow the pump to run long enough to pull a vacuum of approximately 500 microns.
- Turn off the pump and wait two to three minutes, allowing the pressure to rise as moisture boils off inside the hose.
- Pull another vacuum down to 500 microns.
- Watch the vacuum gauge reading. If it rises, check for leaks at the hose fittings. If a pump will not pull down to high vacuum, change the oil.
What does the term recovering mean?
This refers to removing refrigerant from a system and storing it in an external container, regardless of the condition of the removed refrigerant. Recovered refrigerant is usually returned to to system from which it was taken following repairs.
What does the term recycling mean?
Where is it typically performed?
It refers to cleaning a refrigerant for reuse by separating out the oil and passing the refrigerant through filter driers. It can be returned to the system it was recycled from, or put into another system operated by the same owner.
It is usually done at a jobsite or a local service shop.
What must be done to a refrigerant before it can be resold?
It must be reclaimed.
What does the term reclaiming refer to?
What are the requirements for reclamation? What regulation does this fall under?
It refers to processing a recovered refrigerant so that it is chemically pure.
The reprocessed refrigerant must be analyzed at an approved testing facility before it can be classified as being reclaimed. It must meet the AHRI Standard 700 for purity.
What procedures must be followed in the event of a refrigeration system repair?
Before any repairs can take place, all refrigerant in the system must be recovered. After repairs are finished, the system must be then be evacuated to remove all moisture and contaminants before recharging.
What act prohibits the venting of refrigerants?
Section 608 of the clean air act.
What is the primary purpose of a recovery machine?
To remove refrigerant from a system.
What is the cutoff age for recover machines required by the EPA to be certified?
November 15, 1993.
What are seven maintenance tasks to perform on a recovery machine?
- Change the filter drier per the mfg schedule.
- Perform leak checks, the fittings for connections may loosen with use. (every 3 months)
- Verify overfill or high-pressure shutoff.
- Check gauge calibration. Use a reference gauge and compare its readings against the recovery machine’s gauge.
- Check the recovery machine’s compressor oil. In general, compressor oil should not need to be changed or added. However, in the event of a compressor slug, the oil may be washed out. This does not apply to oil-less compressors.
- Complete a visual inspection. Check hoses, fittings, tank expiration, lights and electronic indicators, and clean the case/control panel.
- Use appropriate cables. Use short, heavy duty extension cables rated to handle the equipment’s amp draw.
How frequently should a recovery tank be certified?
Every five or ten years.
What is a digital charging scale?
What is Tare weight?
I is an electronic refrigerant scale that monitors the weight of a refrigerant cylinder as refrigerant is being charged into or recovered from a system.
Tare weight is the weight of the recovery cylinder when it is empty.
