EMERGENCY ENCLOSURE CLOSING
1.0
The SDSS 2.5m telescope has a rolling enclosure that is used to protect the instruments and telescope from the environment. This enclosure rolls eastward to uncover the telescope for observing. There is no emergency procedures for uncovering the telescope since a failure of the normal systems is reason for not observing. However, once uncovered if a failure develops there are alternate means to roll the enclosure over the telescope to provide the necessary protection.
1.1
There are a number of likely failure modes that will keep the enclosure from closing. In general, emergency systems/procedures have been put in place for electrical power failure and/or for enclosure controller/ motor drive failure. In the case of power failure, the telescope will have to be manually stowed prior to closing the enclosure. This will be covered in a separate procedure. This guideline is intended to be used only by persons trained and familiar with the normal operations of these systems.
2.0
The following procedure should be used in the event that the SDSS 2.5m telescope enclosure fails to close due to utility electrical power failure.
2.1
The SDSS telescope enclosure is powered automatically by the main emergency generator near the operations building. Once the emergency generator starts and the automatic transfer switch transfers to "Emergency" (approximately 3 1/2 minutes) the enclosure will operate using the normal controls and procedures.
2.2
In the event the emergency generator fails to start or generate power, use procedure 3.0 for motor drive/controller failure except, you will need to plug the 2 winches into the portable Kubota generator which is stored in the garage. Place the generator on the moving platform and use an extension cord for the other winch. Do not allow extension cord to snag on the telescope or other obstructions as the enclosure closes.
Note: In the event the generator starts and generates power but the transfer switch fails, take the handle inside the transfer switch cabinet and manually transfer the load. Due to the high voltage present in the cabinet do NOT attempt this unless properly trained .
2.3
With all electrical power out you can use the manual chain control to close the doors. See section 4.0
3.0
In the event either the enclosure controller or individual motor drive assemblies fail the enclosure can be closed using two permanently mounted electric winches. These winches work completely independent of the motor drives and the controller and as such will work even with a number of failures. However, since the motors require electrical power from the controller to release the motor brakes , when operating in this mode the brakes must be manually released and held in this position.
1. AT EACH WINCH, PULL BACK THE HUB DRIVE TO RELEASE THE CABLE DRUM. THIS PUTS THE WINCH IN A FREE-WHEELING MODE AND ALLOWS THE CABLE TO BE PULLED OUT EASILY.
2. PULL BOTH CABLES AND ATTACHED PULLEYS THROUGH THE SMALL DOORS IN THE WEST SIDE OF THE ENCLOSURE.
3. ATTACH PULLEYS TO THE RINGS AT EACH END POST.
4. HOOK THE 2 CABLE ENDS TOGETHER APPROXIMATELY 1/2 WAY BETWEEN THE 2 PULLEYS.
5. AT EACH OF THE 4 DRIVE MOTOR ASSEMBLIES INSTALL THE LONG THUMBSCREWS INTO THE BRAKE RELEASE MECHANISM AND TIGHTEN. AS THE SCREWS ARE TIGHTENED THE BRAKE RELEASE WILL MOVE OUTWARD AND WHEN HAND TIGHT THE BRAKES WILL BE RELEASED.
6. PUSH THE DRIVE HUB THAT YOU RELEASED IN STEP 1 BACK ON BOTH WINCH CABLE DRUMS .
7. WITH AT LEAST ONE PERSON AT EACH WINCH AND USING THE REMOTE HAND CONTROL START PULLING IN SLACK IN THE CABLE. (NOTE : SINCE THE WINCHES ARE MOUNTED DIFFERENTLY THIS WILL BE FWD ON ONE AND REV ON THE OTHER.) WHEN ALL OF THE SLACK IS PULLED IN VERIFY THAT THE TWO HOOKS AT THE END OF THE CABLE ARE ROUGHLY CENTERED.
8. VERIFY THE AREA AROUND THE TELESCOPE IS CLEAR OF THE ENCLOSURE.
9. RESUME TAKING IN CABLE AT EACH WINCH WHILE OBSERVING THE CABLE HOOKS AND HOW THE CABLE WINDS ON THE DRUM. IF AVAILABLE, A PERSON AT EACH WINCH TO HELP GUIDE THE CABLE ON TO THE DRUM IS HELPFUL. ENCLOSURE SHOULD BE MOVING AT THIS POINT.
NOTE: DO NOT ALLOW ANYONE TO STAND NEAR THE CABLES UNDER LOAD. ALWAYS STAND INSIDE THE ENCLOSURE WHEN OBSERVING OR OPERATING THE WINCHES. CAREFULLY OBSERVE AND LISTEN FOR ANY SIGNS OF OVERLOADING. OR BINDING .
10. COMPLETELY PULL ENCLOSURE IN TO THE STOPS AND INSERT SAFETY PINS.
11. DISASSEMBLE WINCH SET UP.
12. CLOSE BY-FOLD DOORS.
13. RE-ENABLE BRAKES.
4.0
The final emergency procedure is to be used when the overhead doors will not lower under their motor control . This may be due to any number of reasons such as ; gear box problems, motor problems, relay/interlock or controller failure. If time permits (ie ;the weather is good) then some basic trouble shooting should be accomplished and repaired if possible. In general this will be limited to electrical failures and accomplished by the daytime engineering personnel.
4.1
In the event that the doors must be closed via the manual mechanism simply pull on the wire cable that disengages the motor and engages the manual chain drive. Then simply lower the door by operating the chain drive. This will lower the door in most failure modes and is the only operation that can be done with minimal manpower and time. If the door sticks upon lowering hanging a few hundred pounds of wweight on the door may help in lowering. If a failure of the door spring or a severe binding occurs then the door will have to be repaired before lowering and the openingwill have to be tarped.
4.2
Besure to pull on the other cable to reengage the motor and disengage the manual control before trying to operate the doors via the electric motor.