Procedure to Emergency Close
the 2.5-meter Telescope
Prepared by French Leger
Reviewed by Mark Klaene
Maintained by Gretchen Van Doren
Last modified on
The proper method for stowing the telescope in the event of a loss of
telescope control if site power remains available. The procedure
employs the use of the Wind Screen motors to "drag" the disabled
telescope into a position to allow the enclosure to be
closed.
Cautionary
Notes
Equipment
Involved in this Procedure
Procedure
CAUTIONARY
NOTES:
THIS OPERATION MUST BE DONE
WITH TWO PEOPLE; STATION ONE ON THE OBSERVING DECK AND THE OTHER ON
THE LOWER LEVEL. PEOPLE ON DIFFERENT LEVELS MUST BE IN COMMUNICATION
WITH EACH OTHER.
Warning - there is 208 VAC
in the Wind Screen box - keep hands away from the
circuits.
Operating the telescope with
the hardware as described will disable ALL telescope
interlocks - this includes E-Stop buttons. Exercise extreme care to
avoid personal injury or equipment damage.
Only those persons having a
purpose and are trained may execute this procedure; see web-based
training
list.
THIS PROCEDURE SHOULD NOT BE
DONE IF WEATHER CONDITIONS EXCEED THE FOLLOWING:
ENGINEERING/OBSERVING:
Sustained wind
speed > 25 MPH; wind gusts > 30 MPH
Dew point depression < = 4oF or 2oC
Dust count > 3000
ANY threat of precipitation.
Check the whiteboards in the
Ops building and both levels of the 2.5-m enclosure for the current
status of the telescope and any other notes which may pertain to this
procedure. Be sure to indicate your planned change of
status.
SAFETY WEAR: (recommended)
rubber-soled shoes
EQUIPMENT
INVOLVED IN THIS PROCEDURE
Altitude angle markings;
Location: painted to the drive chain side of WS support
structure; Purpose: these markings inform the pendent operator
that the telescope has reached the 6° alt angle and is therefore
safe to close the enclosure.
Azimuth angle markings;
Location: northeast section of the lower level;
Appearance: black wire tie glued to the stationary structure;
there is a marking on the rotating floor that is labeled "121" and
this needs to be lined up with the black wire tie to indicate the 121
position; the purpose of the markings inform the pendent operator
that the telescope has reached the 121 azimuth angle and therefore
safe to close the telescope.
Brake release valves;
Location: in-line for the air supply and adjacent to each of the
axis brakes for alt and az. The alt brake is directly below the
west-mounted laptop computer, the az brake is in the lower level and
mounted to the NE corner of the telescope concrete pier at 7 ft
elevation; Appearance: 3-way brass valve with black lever
handle; Purpose: to release the brake air cylinder so as to
not drag the telescope against its brake when moving with the WS
drives.
Emergancy closing (EC)
controller; Location: inside the WS control box;
Appearance: - small grey metal box, 3 cables terminated with
Brundy connectors, 2 extending from one end and 1 from opposite end,
two toggle switches mounted to front face.
Emergency closing (EC) power
supply; Location: mounted to the bottom of the WS Control
Box; Appearance: 2 inch x 8 inch x 4 inch alumnium box with
toggle switch, green LED and fuse holder on front face;
Purpose: supplies 24 VDC to power the interlock and control
relays inside the WS control box.
Wind screen (WS) control
box; Location: northeast corner, lower level, enclosure
mounted to the east wall at eye level; Appearance: white, 4 ft
x 3 ft x 1.5 ft metal box.
Wind screen (WS) manual
pendent; Location: stored directly below the WS control
box; Appearance: 4 inch x 3 inch x 3 inch gray metal box, 40
ft of cable attached to one end of box, 10 turn "pot" and amber palm
push switch mounted to front face; Purpose: used to manually
move one axis at a time of the WS; palm switch simulates an E-stop
condition; "pot" controls the speed of the axis drive motor, i.e.,
the more one turns the knob the faster the motor goes, "000" reading
on the "pot" is stop "neutral."
PROCEDURE:
accomplish in numerical order
Preparation
- Open the WS control box. Warning - there is
208 VAC in this box keep hands aware from circuitry.
- Find emergency closing controller
- Open the power switch to the WS control box
by throwing the red handled lever mounted to the side of the
junction box located directly below the WS control box
- Disconnect the 2 Brundy cables located in
the bottom of the WS control box labeled "24 VDC and
Inhibs"
- Connect the appropriate cable from the EC
controller to the EC power supply and the other 2 cables to the 24
VDC and Inhibs connectors (connectors are different so connections
can not be confused)
- Make sure the EC controller toggle switches
labled AZ and ALT are "Off"
- Throw the WS control box power switch
"close" (up)
- Activate the on switch for the EC power
supply, if not already on
- Disconnect the az axis control brundy, left
side of box 1/3 way up from bottom
- Connect the WS manual pendent to this
connector, making sure that the "pot" reads "000" and the palm
switch is depressed
- Turn on the az switch on the EC controller;
this should fire up the 3-left Somitoma amps located top of box
and labled az amps
- Disengage the az brake by turning the az
brake valve to the "off" position
The telescope can now move in azimuth.
Continue the procedure in sequence.
- With one person on the observation deck,
the WB clear of the hand rail, and the alt above 20°, pull up
on the palm switch on the WS manual pendent to engage the
system
- Slowly turn the "pot" knob until the az
begins to move, about 1/2 to 1 1/2 turns, if moving in right
direction continue, if not reverse direction of "pot" and az will
reverse direction
- Continue to move az at comforable speed
until 121° markers line up, slow down when approaching
markers and set the "pot" to "000" before depressing the palm
switch
- Engage the az brake by moving the az brake
valve to the "on" position
- Turn off the az switch on the EC
controller
The telescope is now ready to lower alt
axis. Continue the procedure in sequence
- Make sure the palm switch on the WS manual
pendent is depressed and the "pot" reads 000
- Change the WS manual pendent connector in
WS control box to ALT Axis Brundy, make sure the "pot" is at "000"
and the palm switch is depressed
- Switch on the alt switch on the EC
controller, the alt amp should fire up
- Proceed to the observation deck with the WS
manual pendent and station yourself at the drive chain side of the
WS, the south side when the az is at 121°
- Disengage the alt brake by turning the alt
brake valve to the "off" prosition
- Standing by the south side of the
telescope, check that 'pot' reads "000" then pull the palm
switch
- Turn 'pot' slowly to determine correct alt
movement
- Bring alt to 6° and slowly approach
and set 'pot' to "000" and, depressing the palm switch, on alt
brake
- Disconnect and reconnect all Brundy
connectors to bring system back to normal at the WS control
box
- Close hatches and enclosure
The telescope may be brought up to 30° alt stow position by
using the EC system, if necessary, after enclosure is closed and
telescope is secure. Employ
utmost caution in so doing because of interlock bypass condition
inside the enclosure.
END OF PROCEDURE