There are 2 separate compressed air systems on site that function independently. These systems can backup each other in case of an emergency. Depending on the situation the backup system can support operations for either a short time or for days.


System No. 1:  This system provides compressed air to:


                                    3.5m primary mirror support

                                    2.5m  --all

                                    1m   -- all

                                    .6m   -- all

                                    Ops bldg outlets


System No. 2:  This system provides compressed air to:




                                    3.5m Eyelids/Mirror Cell

                                    3.5m Enclosure lock

                                    3.5m Instrument purges

                                    .5m Back-up PMSS pumps


System No.1


Compressed air is provided by two Kaeser screw compressors in the boiler room.  Each compressor can handle the load by itself and runs for 12 hrs each day, then switches over to the other compressor.  Air from the compressors goes into an air tank in the boiler room. The air is filtered and dried in the boiler room before being distributed. There are additional air tanks at the 3.5m ground level, 2.5m, 1m, and .6m telescopes. Pressure runs at either 109 or 115 psi depending on which compressor is operating.  Each compressor and dryer system provides automatic redundancy.  If the load becomes too much for one compressor to handle (pressure drops due to leak for instance) then the second compressor will come on load automatically.


There are 3 operating modes for these compressors:


On load –generating compressed air;

Off Load – motor running but not building pressure;

Standby- motor off unless pressure drops.


The largest consumer of this air is the 2.5m PMSS system.


The air tanks are sized to provide 15 minutes of compressed air to support the mirrors in the event of a compressor fault.


There are two alarms:  A low pressure alarm in the Ops Building extension on the north facing wall which alerts if the pressure drops below 85 psi; and an alarm in the shipping/receiving area of the Ops Bldg Service Area which alerts if there is too much moisture in the air. (This is critical for the instrument purge systems in the 2.5m but not for anything else)  Both alarms need to be addressed quickly.


In the event of loss of pressure, both the 2.5m and 3.5m should be moved to zenith and held in that position.  Once the pressure drops below 70 psi, do not slew either telescope in altitude.


The Kaeser compressors operate via a computer SIGMA controller.  Compressors labeled #1 and #2 are identical; compressor #3 is slightly different.  If the compressor senses a maintenance issue or is due for maintenance based on runtime, an orange LED will blink by the wrench symbol.  No immediate action is required.


If the compressor faults, a red LED will blink. To clear this, you press the button with the two half moon symbols. Then press the green I button to restart the compressor.  If necessary, try recycling the power using the circuit breaker behind each unit, then press the green I button.  If this fails, call for assistance. (see Fig 1)


If the motor current trips, common with power outages, you can reset this by opening the electrical compartment on the right hand side of the compressor.  There is high voltage in this compartment unless power has been turned off.  Turn the power off (turn off circuit breaker behind unit), then open compartment using the cross shaped key (see Fig 4).  This key is kept near each compressor.  Depress the blue reset button on the contactor.  After depressing the blue button (see Fig 5), close the compartment, turn circuit breaker on then, after the unit initializes, press the green I button.


System No. 2


Compressed air is provided by one Kaeser screw compressor in the garage.  There is also a Speedaire piston compressor that can be used as an emergency backup.  The Speedaire is not an automatic backup and requires a knife switch be thrown to bring it on line.  (see Fig 3)


A twin tower dryer and filters clean and dry the air before it leaves the garage.  The Speedaire tank is the only air storage tank for System No. 2.


There are currently no alarms on System No. 2.


Systems No. 1 and No. 2 can be interconnected to provide an additional level of backup.  Note that System No. 1 can back up System No. 2 completely.  However, System No. 2 can only backup System No. 1 when operating on the Kaeser compressor.


********* Do not operate System No. 1 on the Speedaire compressor.  Doing so will burn up the Speedaire compressor within an hour ************


To operate System No. 1 from System No. 2:


                        Close valve labeled Compressor 2 outlet NO in boiler room

                        Close valve labeled #1 outlet NO in boiler room

Open the valve labeled BU Supply NC in the boiler room (see Fig 2)


To operate System No. 2 from System No. 1:


Open the valve labeled BU Supply NC in the boiler room (see Fig 2)


Anytime you operate both systems from one source you need to conserve as much air usage as possible.  Avoid operating multiple air devices simultaneously.





                                                     Figure 1

                               Kaeser screw compressor controller




                                                            Figure 2

                                                Back up supply valve





                                                            Figure 3


                                    System No. 2 backup knife switch  (with old craftsman legend)




                                                            Figure 4

                               Electrical compartment above air filters (R/H side)

                                              Shown with key in latch





                                                            Figure 5


                                    Motor current trip (blue reset button)

                                    Inside compartment above air filter