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Valve and Compressor Testing

A/C Compressor Evaluation Test Machine (CETM)

A/C Compressor Evaluation Test Machine (CETM)

The A/C Compressor Evaluation Test Machine (CETM) is designed to evaluate compressors without the operator needing to be familiar with the design and functionality of compressors. The most recent upda...

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  • A/C Compressor Evaluation Test Machine (CETM)
  • A/C Compressor Evaluation Test Machine (CETM)
  • A/C Compressor Evaluation Test Machine (CETM)
  • A/C Compressor Evaluation Test Machine (CETM)
The A/C Compressor Evaluation Test Machine (CETM) is designed to evaluate compressors without the operator needing to be familiar with the design and functionality of compressors. The most recent update of the CETM has been manufactured for compressor manufacturers and remanufacturers with more automation and capability.

The CETM requires a computer loaded with the TDS Compressor Evaluation Software (TCES).
A list of compressor models is included in the software for convenience, but it is possible to test any compressor with a given pulley diameter and displacement per revolution.

 
here are the video about operation
https://www.youtube.com/watch?v=Nt7I4GBT5Uw&feature=youtu.be
https://www.youtube.com/watch?v=Nt7I4GBT5Uw&feature=youtu.be



Initial Preparation and Setup

There is some initial setup that must be done before performing a test.
1. Connect the machine's power cord to a 3 phase electrical source. The actual phase
voltage available will be confirmed with the customer before fabrication of the
machine.
3.
Connect a 12 / 24 volt DC power source to the supplied connections on the back of
the machine. We recommend using a 12 / 24 volt battery charger. A 12 / 24 volt
battery may be used but the charge level of the battery will need to checked
occasionally and testing may need to be delayed while the battery is recharged.
2.
Connect a clean / dry air supply of at least 90 PSI to the Air Supply fitting
located on the back of the macine. Nitrogen may be used as an alternative to
compressed air. Various components of the machine will be damaged if a clean /
dry air supply or Nitrogen is not used, and the warranty on the machine will be
invalidated.
4. Connect the computer to the machine at the Computer Data Connection using
the supplied programming / communication cable and USB to Serial adapter.
The USB port used must be COM1. If needed, configure the USB port to
communicate on COM1.

Quick Start

The CETM is easy to use. Mount the compressor on the universal clamping fixture.
Align the compressor pulley with the drive motor pulley by sliding the clamping
fixture along the rails and insure the belt is aligned. The compressor should be
drained of excess oil from the compressor (only a trace amount of oil should remain
inside the compressor). Excess oil will lead to a false pumping ability of the
compressor. The compressors function is to pump refrigerant gas and excess oil
will create a hydraulic effect giving false data. Insure that the hoses are properly
connected.
 
Start the program and ensure the machine is communicating with the computer. This
is confirmed on the lower left corner of the "Test Setup" screen by the status color of
the connection indicator changing from red to green.
The software consists of four (4) screens:
Test Setup Screen -This screen is used to choose the type of compressor to be
tested and to make changes to the drive specifications (if necessary).
Compressor Edit Screen - This sub-screen is used to imput the required
information regarding the particular compressor that is to be tested.
Test In Process Screen - This screen has data fields that show the actual
Suction, Discharge, and Crankcase pressures as they are being generated by
the compressor. There are also four (4) graphs (Suction / Discharge /
Crankcase / Power) that are continuously updated in "real time"
Test Perforance Report Screen - Shows the Final Test Report and allows printing of it.



The easiest way to run a test is to use the drop down list of compressor types listed in
the “Model Type” field to select a compressor model that best represents the
compressor being tested. Select the model type from the list. Enter the clutch pulley
size in the Clutch Pulley Size field and click on the “Start Test” button. If a compressor
model is not listed or the properties for it need to be edited, selecting the "Edit
Defaults" button will activate an edit window and the compressor can be added by
selecting the "Add" button beside the compressor list which will open a window
showing fields where the specifics of the compressor can be entered. This is also
where any changes to the compressor properties can be made.



After selecting the compressor type confirm the displacement value of the compressor. If it
is incorrect you may change it in the "Displacement / Revolution" field.
Confirm the direction of the drive motor.The drive motor on the CETM can run forward
or backward. Most compressors will run forward. Default direction is "forward"
Enter the compressor clutch pulley diameter. This measurement is in millimeters.
The "Pass Criteria" is factory set at 200 PSI for both the Differential Pressure between
the internal Suction / Discharge pressures and the Minimum Discharge Pressure required
for the compressor to pass the test. These are factory set for each machine and should
not be changed, but can be adjusted if desired. If a tighter tolerance is desired increase
the value for the Differential Pressure, and if a looser tolerance is desired decrease the
value. The test time is also set at the factory and cannot be adjusted.



Data
The CETM has two methods for reviewing the results of the test.

The first method is the review of the indicators for “Flow Result” and “Control Valve”
located on the“Performance Report screen. These give an estimate for the operator
who is not familiar with how a compressor should perform. The “Flow Result” shows
an evaluation of the flow performance of the compressor. This is determined by
pressure thresholds. As mentioned previously the mass flow rate is proportional to the
pressure drop across an orifice. If the higher discharge pressures are not obtained the flow
will not be optimized. The settings showing a drop in compressor performance are
representative of 10% drops in the pressure generated by the compressor. “Good” will be
10% lower than “Excellent”, “Acceptable” will be 20% lower than “Excellent”, and so on. It
does not necessarily translate to the temperature of the air entering the passenger
compartment of the vehicle. It is instead representative of the compressors
performance. A pressure drop of 10% may only reflect a small amount of temperature
change of the air that the passengers may not notice.

The “Control Valve” evaluation is a little more complex and is broken down as follows:
Full Function – This is when the compressor drops to a relatively low suction
pressure as the compressor drops to minimum displacement.
Part Function – The evaluation will give this reading when the discharge pressure falls
lower but not to minimum. It means the compressor will lower the displacement amount
but not completely.
Poor Function – This can only happen if the crankcase pressure detects that the
internal mechanical control valve is working but could not detect an acceptable drop in
the compressor performance. It means that there may not be enough flow through the
control valve or the compressor is bypassing gas faster than the flow through the valve.
None Detected – This occurs when no crankcase pressure is detected or the crankcase
never rises above the suction pressure. This may happen if the internal control valve is
not functioning at all or the compressor is a fixed displacement model.
Does Not Have – This is the reading when a fixed displacement compressor model is
selected.
The second method is for operators that are more experienced with compressors or
who are looking to get more information than the indicators provide. Using the
graphical fields located lower on the “Performance Report” screen, the pressure curves
and power draw of the compressor can be evaluated. The data is also saved to the
computer hard disk, and can be imported into a spreadsheet such as Excell.

Theory of Operation

A car A/C compressor is essentially a pump designed to move a gas through a closed
system. There are many types of compressors and they come in many sizes. For the CETM
to test many types of compressors the system has to be programmable so that the test
dynamics for all models produce similar results within a specified range. This is
accomplished by entering the displacement per revolution and the pulley diameter in the
fields on the Test Setup screen. Using the data from these fields a calculation is performed
within the computer software and the drive motor speed is changed to compensate for the
size of the compressor.

As noted earlier, the test imitates the loads that would be put on a compressor in an
actual vehicle air conditioning system. When the test is started current is sent to an
air pressure transducer that adjusts the suction pressure. This is well above the
pressure which would result in a freezing evaporator and is also high enough to
simulate a medium to high heat load on an evaporator. If the compressor is a variable
displacement compressor the control valve should have been set at the factory to
result in a crankcase pressure equal to the suction pressure.
The suction pressure is then adjusted by the computer down to a pressure that
represents a low heat load or a freezing evaporator temperature. If the compressor is a
variable displacement compressor the discharge pressure should drop all the way down
to unload the compressor. The suction pressure is then increased back to the high load
condition. The discharge pressure should go up again. If it is a fixed displacement
compressor the discharge pressure will drop proportionally to the suction pressure.

The discharge pressure is increased by putting a restriction in the discharge line. For this
test the restriction is an adjustable orifice inside a metering valve. The pressure drop
across an orifice is directly proportional to the mass flow rate. Therefore, when the
compressor drops to minimum displacement the mass flow rate drops. When the machine
is shipped the Flow Control Valve is set to fix the orifice size. This setting is for average cc/
rev compressors (for instance 200 PSI). For lower cc/rev compressors it may be necessary
to adjust the Flow Control Valve to allow the compressor to pump up to its peak capability.
It is recommended that no changes be made to this valve.

Note: If you adjust this valve only adjust in 1/4 turn increments at a time.

The “Peak” setting is the maximum pressure differential a good base line compressor
will achieve. If this is set too low poorly performing compressor will pass, and if it is set too
high good compressors will fail. This setting is extremely important and great care should
be taken before it is adjusted.
A car A/C compressor is essentially a pump designed to move a gas through a closed
system. There are many types of compressors and they come in many sizes. For the CETM
to test many types of compressors the system has to be programmable so that the test
dynamics for all models produce similar results within a specified range. This is
accomplished by entering the displacement per revolution and the pulley diameter in the
fields on the Test Setup screen. Using the data from these fields a calculation is performed
within the computer software and the drive motor speed is changed to compensate for the
size of the compressor.
Theory of Operation
The CETM has a frequency inverter to adjust the speed of the drive motor which is
controlled by the computer software. This inverter also sends information to the
computer on the amount of power being used to turn the compressor during the test.



Test Machine Specifications
Machine Type..... Automatic Computer Controlled CC/Rev compressor evaluation test machine
with TDS Compressor Evaluation Software (TCES). Computer and monitor not
included.
Compressor Drive..... Clutch belt drive to accommodate multi-groove and V-belt pulleys
Motor..... Five (5) horsepower premium efficiency inverter rated
Speed..... Variable speed motor controller
Voltage..... Dependent on available 3 phase electrical power at the installation location
Low Side Monitor..... 2.5 inch 0 to 160 PSI liquid filled gauge & 0 to 100 PSI pressure transducer
High Side Monitor..... 2.5 inch 0 to 300 PSI liquid filled gauge & 0 to 500 PSI pressure transducer
Sump Monitor..... 2.5 inch 0 to 160 PSI liquid filled gauge & 0 to 100 PSI pressure transducer
Compressor Mounting..... Universal clamping fixture mounted on alignment slide

Belts Provided..... One (1) multi-groove serpentine belt and one (1) V-belt
Drive Belt Tensioning..... Air cylinder tensioned idler pulley
Test capabilities..... Fixed displacement and variable displacement (mechanical & electronically
controlled) with printed test report
Dimensions..... 24 inches wide x 32 inches high x 30 inches deep
Weight..... Approximately 250 lbs.
Finish..... Powder Coated Forest Green

Safety Features
1. High Pressure Cutout Switch..... Test terminates if discharge pressure reaches preset safety PSI
2. High Motor Amperage..... Test terminates if motor draws excessive amps due to compressor
high turning resistance.
3. Safety Guard with Interlock..... Motor cannot operate without safety guard closed and will stop if the
guard is opened
4. Emergency Stop Button..... Immediately shuts down all operations when pushed

Shanghai Trisun Mechanical Parts Co., Ltd is the Exclusively Authorized Dealer for
the TDS AC Compressor Evaluation Test Machine

 
 

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