Refrigeration Compressor Manual

P and S Automation Limited

Provision RefrigerationCompressor

Control System

Manual

P & S Contract 2144P

P & S Automation Limited.

Project: Provision Refrigeration Compressors Contract 2144PControl System Manual November 2009

47-49, Cutlers Road,Saltcoates Ind. Est,South Woodham Ferrers,Chelmsford EssexTel: 01245 322777Fax: 01245 322776Email:[email protected]: www.PandSautomation.com

Refer-Compressor-Manual-iss1.doc1q

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Table of Contents:

1. Introduction .............................................................................................................................31.1 Operation Notes ..........................................................................................................................................3

2. Overview and Description ......................................................................................................32.1 Operating Philosophy..................................................................................................................................32.2 Alarms.........................................................................................................................................................32.3 Sea Water Pumps ........................................................................................................................................32.4 H.T. Compressors .......................................................................................................................................4

2.4.1 Hand Operation ...........................................................................................................................................42.4.2 Auto Operation............................................................................................................................................42.4.3 Condenser Control Valve Operation. ..........................................................................................................5

2.5 L.T. Compressors........................................................................................................................................62.6 Subcooling Operation. ................................................................................................................................7

3. PLC Program Notes ................................................................................................................7

4. HMI Operation ........................................................................................................................94.1 Home Page ..................................................................................................................................................94.2 Compressor Screens ..................................................................................................................................104.3 Settings Pages ...........................................................................................................................................14

5. Appendix 1. – Alarm List......................................................................................................28

6. Appendix 2. - Settings ...........................................................................................................30





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1. IntroductionThis system is to control two off Sabroe CMO26 & two of TCMO28 compressors. The originalSiemens control PLC has been replaced with a new Mitsubishi control PLC and HMI in November2009.

1.1 Operation NotesAfter a compressor has tripped out on a fault condition, switch the control selector switch back toStop, then press the Mute button to accept the fault. Press the Alarm button on the HMI to showthe alarm list to see what alarm has tripped the compressor. If the fault is one that has to be resetexternally (e.g. KP15 Temperature) then once it has been reset press the mute again, the alarm willnow clear (shown on the alarm list as no symbol to the left of the alarm).To make changes in the HMI there is a requirement to first Login. To Login press the Login button(1st function key) then enter 8786 and press the enter key, the Login will stay active for 30 minutesthen automatically log out.

2. Overview and Description

2.1 Operating PhilosophyThe system controls 4 refrigeration compressors. No.1 & 2 are on the H.T. circuit and No.3 & 4 areon the L.T. circuit. Each compressor has an associated sea water pump.

2.2 AlarmsThere are 40 alarms installed into the system, the complete alarm list is detailed in appendix 1.When an alarm occurs, the ‘Common Alarm’ output relay is energised, the running lamp for thepump or compressor associated with the alarm will flash. The alarm will show on the HMI in thealarm banner on the home page and in the alarm list. To accept the alarm press the mute button onthe panel or the ‘Ack’ button on the HMI.

2.3 Sea Water PumpsEach of the 4 sea water pumps is controlled as detailed below:

When the front panel selector switch is set to ‘Off’ the SW pump will not run.

When the front panel selector switch is set to ‘Hand’ the pump will start and continue to runprovided the Common Emergency Stop and Pump Overload are not active.





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When the front panel selector switch is set to ‘Auto’ the pump will start 30 second before thecompressor starts and then continue to run until 15 seconds (set by adjustable SW Pump StopDelay timer) after the compressor has stopped.

If the Emergency Stop is activated the pump will stop.

If the Thermal Overload is activated the pump will stop, the running light will flash and theCommon Alarm relay will de-energise.

2.4 H.T. Compressors

2.4.1 Hand OperationProviding the compressor is ‘OK to Run’ (no shutdown alarms present – see appendix 1.), the seawater pump is running and the emergency stop is not active, if the control selector switch is set too‘33%’ the compressor will start and continue to run. The running lamp will illuminate and the‘Running’ relay will energise, this will energise the Running Lamp on the Cold Room controlpanel. The HT Liquid Solenoid will energise. After a 60 second delay (Adjustable ‘Oil ReturnDelay’) the Oil return Solenoid will energise.

If the selector switch is set to 50% the 50% solenoid will energise after a 1 second delay.If the selector switch is set to 67% the 50 % & 67% solenoid will energise after a 1 second delay.If the selector switch is set to 100% the 50%, 67% & 100% solenoid will energise after a 1 seconddelay.

When the switch is set to off, the compressor will stop and the solenoid valves will de-energise.

If any of the shutdowns occur the compressor will stop, the running lamp will flash and thecommon alarm relay will de-energise. The individual Compressor Fault relay will de-energise (thisis relayed too the Cold Room Control panel).

2.4.2 Auto OperationThe S.W. pump should be in ‘Auto’. There should not be any alarms present.

Turn the Compressor Selection switch (1 or 2) to the compressor to be run. Turn the ControlSelector Switch to ‘Auto’ a 10 minute timer will start (Start Delay Timer), after 9 ½ minutes (30seconds less then the Start Delay Timer) the sea water pump will start to run. After a further 30seconds the compressor will start to run.





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The running lamp will illuminate and the ‘Running’ relay will energise, this will energise theRunning Lamp on the Cold Room control panel. The HT Liquid Solenoid will energise. After a 60second delay (Adjustable ‘Oil Return Delay’) the Oil return Solenoid will energise.If the Suction pressure is greater then the Set Point plus the Hysterisis the Step Up timer will start(60 Seconds), once timed out the 50% loading valve will energise.

While the Suction Pressure is within the window Set Point minus Hysterisis (40 PSI) to Set Pointplus Hysterisis (50 PSI) the loading valve status will remain steady.

If while at 50 % loading the Suction pressure is greater then the Set Point plus the Hysterisis theStep Up timer will start (60 Seconds), if this times out the 67% loading valve will energise as wellas the 50% valve.

If while at 67 % loading the Suction pressure is greater then the Set Point plus the Hysterisis theStep Up timer will start (60 Seconds), if this times out the 100% loading valve will energise as wellas the 67 & 50% valves.

The process will reverse if the Suction pressure is less then the Set Point Minus the Hysterisis butthe Step Down time is much shorter at 5 seconds.

If when at 33% loading (no loading valves energised), the Suction pressure is less then the SetPoint Minus the Hysterisis for the Step Down time (5 seconds) the compressor will stop and thesea water pump will stop after a further 15 seconds.

While the compressor is stopped and in Auto if the Suction Pressure rises above the Set Point plusHysterisis the start timer will start (Start Delay Timer), after 9 ½ minutes (30 seconds less then theStart Delay Timer) the sea water pump will start to run. After a further 30 seconds the compressorwill start to run and load up/down as detailed above.

When the switch is set to off, the compressor will stop and the solenoid valves will de-energise.

If any of the shutdowns occur the compressor will stop, the running lamp will flash and thecommon alarm relay will de-energise. The individual Compressor Fault relay will de-energise (thisis relayed too the Cold Room Control panel).

2.4.3 Condenser Control Valve Operation.The Motorised Valve will be ‘Closed’ (down) while the compressor is stopped, the close signalremains on and therefore it is important that the limit switches within the valve actuator are setcorrectly.





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When the compressor starts the valve is given an ‘Open’ (Up) signal for 30 seconds (adjustable),once the 30 seconds has timed out the valve will then move to try to maintain the Dischargepressure at the ‘Set Point’ (247 PSI).It does this by Closing (Down) to increase pressure and Opening (Up) to decrease pressure.

The controller action is described below.

The controller checks the values on a cyclic basis, the period of this cycle is set by the ‘I-Paramtime (3 seconds). Each time it checks the values:

It works out if the error is High or Low.It then works out the size of the error.It works out if the error is greater then the ‘Large Error Inhibit’ value.It works out if the error is greater or less then the error during the last cycle.

Based on the answers to these checks it then operates the valve as below:

If the error is high, it needs to reduce pressure so will mainly be Opening (Up) the valve, ifthe error is low, it needs to increase pressure so will mainly be Closing (Down) the valve.The P-Parameter is divided by the size of the error and multiplied by 10, this value is thenused in the ‘Pause’ timer. Hence a small error gives a long pause time and a large error givesa short pause time.The output will then pulse on for 1 second (Impulse timer) and off for the length of time dueto the size of the error (P-Parameter / error (PSI) x 10 = time in 0.1 sec e.g. a P-Param of 40and an error of 10PSI = 40/10 x 10 = 40 = 4 seconds).If the error is greater then the Large Error Inhibit value (20 PSI) then the above will alwaysbe true, if the error is less then 20 then the D parameter can come into play.

If the error in one sample is less then the error in the previous sample (i.e. the process isstarting to get closer to the set point) then the valve will pulse in the other direction to reducethe amount of overshoot that occurs. The D parameter (set at 100) will operate a pause timerfor a pulse in the other direction as described for the normal operation above.

2.5 L.T. CompressorsThe L.T. compressors work in the same way as the H.T with the following differences:

The Suction set point is lower (15 PSI)When temperature input KP77 is set the additional ‘Cooling’ valve will be energised.





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2.6 Subcooling Operation.When the selector switch is set to Sub Cooling or Compound, the subcooling valves will energise atime delay (0 seconds) after the following statement is true:‘If compressor 1 or 2 is running, and compressor 3 or 4 is running’ When the statement is false thevalves will de-energise.

3. PLC Program NotesAll used devices (memory tags, timers, data words) have a comment to advise what they do.HMI will act as a transparent conduit to the PLC. The enables the HMI to carry on working whilealso looking at / changing the program.The program is structured as detailed below:

Rung 0 to 184 - Set default values to adjustable valuesWhen the PLC is set to Run (normal mode), during the 1st scan the default settngvalues are loaded into the various data words.

Rung 184 to 297 – Read in Analogue ValuesThis program area reads in the analogue values. The raw values are 0 for 4mA and4000 for 20mA.

Rung 303 to 580 – Scale Analogue ValuesThe analogue values are scaled by carrying out a division and then a subtraction toscale the inputs to the real engineering units. Note pressure is in PSI, current inAmps.

Rung 585 to 721 – Map in Digital InputsThe digital inputs (X**) are mapped into memory tags (M**) these memory tagsare used within the program, thus if a switch works the opposite way to expectedthen the input can be inverted once in this area.

Rung 723 to 1050 – Check for Alarm Values from Analogue ValuesThe analogue inputs are compared to alarm limit values, the output tags from thesechecks are used in the Alarm handling section.

Rung 1077 to 3080 – Alarm HandlerAll the alarm handling software is in this area, there are 40 alarms within thesystem.

3074 to 5200 – Compressor No.1All the software for controlling compressor No.1 is within this area



9456 to 11566 – Compressor No.3





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All the software for controlling compressor No.3 is within this area11570 to 11588 – Liquid Valve Controls11606 to 11 636 – Sub Cooling Operation11656 to 11834 – Map Outputs Out

The memory tags for each digital output are mapped out to the output in this area.





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4. HMI OperationThe HMI is used to view internal operation values, alarms and also to change settings.

4.1 Home PageThis is the Home Page it can be accessed at any time by pressing the ‘Home’ button

It shows which compressors are set to run in Auto and prompts the 4 function keys to press toaccess the values for each compressor, i,e, to select compressor 2 press the button labelled ‘PREV’.The Banner area at the top displays the last active alarm.-

OGIN PREV NEXT SETTING LOGOU





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4.2 Compressor ScreensThe screens below are the same for each compressor, for this manual we have only showed thescreens for Compressor 1.

This is the first compressor screen. All the function keys will work as labelled. If an alarm occursthe word ALARM will flash in the top right hand corner, to go to the Alarm page press the‘ALARM’ button.-

To go to the next page for compressor No.1 press the ‘NEXT’ button.






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The 2nd compressor screen is shown below.The valves will change to solid black when they are energised.

--






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The 3rd compressor screen is shown below:The control requirement is shown on the left hand side. Man means in Manual Control, when inmanual control the amount of load required will be shown by the appropriate valve being filled inblack.When in Auto the word Man will be replaced by the word Auto.

The right hand side shows the status of the output valves. These will be filled with black when theyare active.

--






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The last compressor page is shown below, this details the status of the sea water pump. The NEXTbutton will not work on this page.

-

-






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4.3 Settings Pages

The Setting screen can be accessed by pressing the SETTING button from any of the compressorpages.

-Before settings can be changed you must first LOGIN.

Press the LOGIN button.






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Input the Password (which is 8786), Then press the ENTER button.

--If the password is entered correctly it will show the screen below.






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--Press the NEXT button to scroll through the setting screens.






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-The 1st screen details the current alarm setpoint (limit) and the step down (time delay) for eachcompressor.






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To change any values on the settings screen use the ARROW keys to move the CURSER to thevalue to be changed.

Use the numeric keys to enter the new value, then press the ENTER key to enter the value.






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The next setting screen shows the suction Setpoint and Hysterisis, the hysterisis is added to eitherside of the setpoint.






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The next setting page shows the suction alarm (setpoint) and delay (step down) values.






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The next setting screen shows the HT and LT Step Up/Down and Start / Stop delays.






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The next setting screen shows the Sub Cooling valve operation delay.






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The next setting screen shows the Discharge pressure Alarm/Warning/Setpoint levels,alarm/warning and Oil Return Valve operation delays.






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The next setting screen shows the control valve settings,:The P-Parameter is the gain setting, the higher this value the slower the operation will be.The I-Parameter sets the update sample time in seconds (don’t set above 10)The IMPLUSE time is the length of each pulse (nominally 1 second)The Pause and Valve times are not used and should be left as they are.The Open > Start setting is the time that the control valve is told to open when thecompressor starts. After this time the valve will start to control to the Setpoint.






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The next setting screen has additional control valve settings.The D parameter is similar to the P-Param on the previous screen, but this sets the amountof correction that is given when the process value starts to improve towards the setpoint,this is to reduce overshoot. The higher the value the more action is given.The LRG ERR INH – this sets a window either side of the set point when the process valueis outside this window the D-Param is inhibited.






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This is the last setting page. The settings shown is the ‘Run On’ time for the sea water pump afterthe compressor is stopped.






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This is the Alarm List screen, it is accessed by pressing the ‘Alarm’ button.

Press the TIME button to give time and date of the alarm.The ‘Plus’ button will change the size of the font.Press the ACK button on the HMI or the MUTE button on the main panel to accept the alarms.A $ sign to the left of the alarm means that it has not been accepted.A – sign to the left of the alarm means that it has been accepted but it is still active (not beencleared).






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5. Appendix 1. – Alarm ListThe list of alarms is detailed below:

Alarm Description Compressor Shutdown1 Compressor1 High Current N2 Compressor1 High Disc.Pressure W N3 Compressor1 High Disc.Pressure A Y4 Compressor2 High Current N5 Compressor2 High Disc.Pressure W N6 Compressor2 High Disc.Pressure A Y7 Compressor3 High Current N8 Compressor3 High Disc.Pressure W N9 Compressor3 High Disc.Pressure A Y10 Compressor4 High Current N11 Compressor4 High Disc.Pressure W N12 Compressor4 High Disc.Pressure A Y13 HT Low Suction Pressure N14 LT Low Suction Pressure N15 Compressor1 H-L Oil Y16 Compressor1 Oil Pressure Y17 Compressor1 Oil Temp. Y18 Compressor2 H-L Oil Y19 Compressor2 Oil Pressure Y20 Compressor2 Oil Temp. Y21 Compressor3 H-L Oil Y22 Compressor3 Oil Pressure Y23 Compressor3 Oil Temp. Y24 Compressor4 H-L Oil Y25 Compressor4 Oil Pressure Y26 Compressor4 Oil Temp. Y27 Compressor1 Overload Y28 Compressor1 Fail to Start N29 Compressor2 Overload Y30 Compressor2 Fail to Start N31 Compressor3 Overload Y32 Compressor3 Fail to Start N33 Compressor4 Overload Y34 Compressor4 Fail to Start N





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35 S.W. Pump 1 Overload Y36 S.W. Pump 2 Overload Y37 S.W. Pump 3 Overload Y38 S.W. Pump 4 Overload Y39 Spare N40 Spare N41 Pressure in Safety Line N





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6. Appendix 2. - SettingsThe adjustable settings and their default values are listed below: These values can be changed bythe HMI, however if the PLC is stopped (either by the Reset / Stop / Run switch or by poweringdown). When it restarts these default values are re-loaded.

Plus (High Temp Minus (Low Temp)Compressor Comp.1 Comp.2 Comp.3 Comp.4Motor Setpoint 60A 60A 60A 60ACurrent Delay 2 Sec 2 Sec 2 Sec 2 Sec

Suction Control Plus (High Temp Minus (Low Temp)Suction Set Point 45 PSI 15 PSIPressure Hysterisis 5 PSI 5 PSIWarning Set Point 30 PSI 6 PSILow Press. Delay 5 Sec 0 Sec

Step Up 60 Sec 60 SecCompressor Step Down 5 Sec 5 Sec

Start Delay 600 Sec 600 SecStop Delay 1 Sec 0 Sec

Sub Cooling Delay 0 Sec N/A

Plus (High Temp Minus (Low Temp)Condenser Comp.1 Comp.2 Comp.3 Comp.4

Alarm 295 PSI 295 PSI 295 PSI 295 PSIDischarge Warning 280 PSI 280 PSI 280 PSI 280 PSIPressure Delay 5 Sec 5 Sec 5 Sec 5 Sec

Set Point 247 PSI 247 PSI 247 PSI 247 PSIHysterisis 1 PSI 1 PSI 1 PSI 1 PSIGain (P) 40 40 40 40Gain (D) 100 100 100 100

Control Sample Time (I) 3 Sec 3 Sec 3 Sec 3 SecValve Large Error Inh (D) 20 PSI 20 PSI 20 PSI 20 PSI

Pulse Time 1 Sec 1 Sec 1 Sec 1 SecPause Time 1 Sec 1 Sec 1 Sec 1 SecValve Close Time 60 Sec 60 Sec 60 Sec 60 Sec





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V/V Open > Start 30 Sec 30 Sec 30 Sec 30 SecComp. Oil Return Delay 60 Sec 60 Sec 60 Sec 60 Sec

Plus (High Temp Minus (Low Temp)Pumps Comp.1 Comp.2 Comp.3 Comp.4

Pre Start Time 30 Sec 30 Sec 30 Sec 30 SecStop Delay 15 Sec 15 Sec 15 Sec 15 Sec

Refrigeration Compressor Manual

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