There are two air compressor systems in the K-Hut for operation of the telescope. The larger of the two compressors (Quincy compressor) supplies the telescope structure lifting air. The other compressor (Curtis compressor) provides air to the tracker, to operate the drive and slew motor brakes, and purge air to the tracker rail and drive screw bellows. This smaller compressor also supplies “clean” air to delicate instruments on the Tracker. As a result, we need to keep this air as clean as possible by removing both moisture and oil from the system. Currently, we are evaluating the purchase of an “oil-free” system to replace the Curtis air compressor.

The Quincy compressor discharges through an ambient air cooler to the large air receiver. The ambient air cooler has an automatic drain valve that removes condensation that forms in the ambient air cooler. The air then flows through an oil and water filter that has an automatic drain valve located at its lower end and enters the large receiver. From the receiver, air is directed to two filters. The first filter is an oil removal filter. The second filter is a water and particulate removal filter. Neither of the two filters have automatic drain valves.

	Structure Lift Air Compressor in K-Hut

Following the filters, air is directed into a dual-tower, desiccant air dryer. The dryer removes sufficient remaining moisture from the air to protect the structure lift air components.

On the discharge of the dryer, there is a connection to provide backup air to the tracker purge and brake air system. This connection consists of an isolation valve and particulate filter. From the particulate filter, the air travels to a manifold consisting of an isolation valve, regulator, check-valve and outlet isolation valve shown below. If the system is in the proper lineup and operating, the regulator will automatically provide air to the tracker purge and brake air system, if pressure in the tracker purge and brake air system falls below 95-psig.

	Tracker Purge and Brake Air Backup Air Manifold in K-Hut

The Curtis air compressor, shown below, provides air to the tracker for operating the drive and slew motor brakes, for purging the tracker rails and drive screw bellows, the spectrograph rooms, and the machine shop. Air from the receiver passes through a water removal filter. This filter, shown below, does not have an automatic drain valve. It must be drained twice each shift including dayshift, or when a water level is visible in the sight glass.

The Curtis air receiver discharges through a regulator set to 110-psig. The compressor cycles between 160-psig and 108-psig in its receiver. The receiver has an automatic drain valve (Snap Trap) and it should automatically drain. However, the drain line from this trap often freezes in cold weather. If it does, just disconnect the line from the Trap, allowing the water to drain to the floor.

	Curtis Compressor in K-Hut

Air is delivered to the refrigeration dryer from the receiver via an oil/water/particulate filter (shown below). This filter has an automatic drain valve.

	Refrigeration Air Dryer in K-Hut

Air from the dryer is delivered to the spectrograph manifold located in the upper electrical room. The manifold is fitted with a pressure gauge. Air is directed to the tracker via a manifold located inside the telescope pier/wire wrap. There is an isolation plug valve, pressure gauge and pressure switch located on the tracker purge and brake air manifold. The pressure switch is set to trip at 78-psig and reset at 84-psig. When the pressure switch trips, a shutdown signal is sent to the tracker. The tracker cannot be operated when the pressure switch is tripped. An indicating light on the emergency shutdown panel indicates that the pressure switch has tripped. The indicating light is labeled “LOSS OF AIR AND/OR GLYCOL.”

	Upper Electrical Room

From the tracker air manifold below the telescope main bearing, air is delivered to lower X via a 3/8-inch hose to a tee. One branch of the tee goes to two regulators at lower X that control purge air pressure at 5-psig. From the regulators, air goes to a valve bank connected in parallel that directs air to each purge point. For each rail (upper X (1), lower X (1), and Y (2)), there are two points of entry for purge air. For each roller nut screw, there are two points of entry for purge air. The points of entry for purge air on the roller nut screws and the rails are at the extreme ends of each component. There are 14 points where purge air is applied to the tracker.

The second branch of the tee is the tracker brake air supply. The air is regulated, filtered, and then directed to a mini-solenoid block manifold. The solenoids operate three way valves to either direct air pressure to the brake releasing it or isolating air and venting the brake to set the brake.

	Structure Lower X Configuration

General Precautions:

1. The air systems discussed above are medium energy systems. If operated improperly, serious personnel injury or equipment damage may occur.

2. Open air-valves slowly, allowing the air pressure to equalize across the valve. A failure to open air valves slowly may cause excessive heating in the down-stream line due to the heat of compression. Dieseling, of the oil in the air, may occur. Pressurization rates should not exceed 200-psig per second.

	Inside Telescope Pier/Wire Wrap

3. Filters and air receivers that do not have automatic drain valves installed must be blown down regularly. To blow down a filter or receiver, open the bottom drains until air is discharged. Typically, prior to startup and at shutdown. Prior to startup, it is not expected that any oil or water will be present. However, to ensure that the system was shutdown properly, all filters and receivers without automatic drain valves should be drained prior to startup. Failure to blow down filters and receivers that do not have automatic drain valves installed will result in system and component damage.

4. Verify the proper oil level in a compressor prior to startup.

1.1 Structure Lift Air Startup

1.1.1 Read the receiver pressure gauge. If there is pressure in the receiver, perform steps 1.1.1.1 and 1.1.1.2. Otherwise, proceed to step 1.1.2.

1.1.1.1 The Snap Trap shown above drains the receiver automatically. Make sure the sight glass is not more than ½ full.

1.1.1.2 The two filters on the outlet of the receiver and the filter on the outlet of the dryer as seen in the below photograph have automatic drain valves that should be manually drained on system startup and shutdown. Make sure the sight glasses are not more than ½ full.

Filters with Snap Traps Installed

1.1.2 Check the oil level in the compressor. This is done by inspecting the bull’s-eye on the oil tank. A full bull’s-eye indicates proper oil level. If a level is visible in the bull’s-eye or below the bull’s-eye, do not start the compressor. Contact John Vause for assistance.

1.1.3 Test the compressor indicating lights by pushing the white button on the control panel. All indicating lights should illuminate. If any lights fail to illuminate, document the failure in CMMS with a Work Order.

1.1.4 Rotate the red stop button clockwise until it pops up. Do not pull on the stop button. Pulling on the stop button will cause premature failure of the button.

1.1.5 Start the compressor by pushing the green start button until the compressor begins to rotate. You should verify that compressor discharge pressure and discharge air temperature increase. The filter light may be on at startup in cold weather, but should go out in approximately 1 minute.

1.1.6 While the compressor is running, check for oil flow in the sight glass pictured below. There should be a small amount of flow in the sight glass. If the sight glass shows full flow, contact John Vause.

1.1.7 Slowly open the dryer outlet valve. When the dryer isolation valve is open and air pressure is rising in both towers, start the dryer by pressing the black button on the control panel. Within 8 seconds, one of the towers should blow down.

1.1.8 Verify that purge pressure is at 45-psig. If it is not, adjust the purge pressure to 45-psig using the purge air valve.

1.1.9 Slowly open the isolation valve to the tracker brake and purge air backup system. Verify there is no indication of moisture in the tracker purge air backup particulate filter sight-glass. If there is any indication of moisture, contact engineering immediately. This step should be performed if you want to operate the tracker even if the tracker purge and brake air compressor is shutdown. There will not be any air to operate the tracker brakes and the tracker will be locked out. See the infrequent/abnormal operations in Section 4.0 below.

1.2 Structure Lift Air Shutdown

1.2.1 Shut the structure lift Air Dryer Outlet Valve.

1.2.2 Shut the isolation valve to the tracker brake and purge air backup system.

1.2.3 Drain the receiver and filters.

1.2.4 The air system should be depressurized by commanding the structure to stand until air pressure is relieved. (Less than or equal to 15 seconds only.)

1.2.5 Turn the structure lift air dryer off by pressing the red stop button on its control panel.

DO NOT STOP THE COMPRESSOR UNTIL ITS DISCHARGE PRESSURE AS READ ON ITS CONTROL PANEL INDICATES 0-PSIG. YOU MAY DAMAGE THE COMPRESSOR BY SHUTTING IT DOWN UNDER FULL LOAD.

1.2.6 The compressor will go through a shut down and cool down sequence. As the receiver pressure approaches maximum, the compressor will unload and cool down. When compressor discharge pressure reads 0-psig and discharge air temperature is lowering, stop the compressor by pressing the red stop button on its control panel.

1.3 Tracker Purge and Brake Air Startup

This system should always be in operation. However, the following is provided for initial startup following a maintenance outage.

1.3.1 Check the oil level in the compressor crankcase. Oil level should be above ½ in the bull’s-eye but not above the bull’s-eye. If oil level is abnormal, contact engineering.

1.3.2 Check that the compressor receiver is draining properly by monitoring the water and oil level in the automatic Snap Trap.

1.3.3 Turn the refrigeration dryer on using the on/off switch located on the side of the dryer. Check to make sure the fault light goes out.

1.3.4 Slowly open or verify open the following valves: Receiver outlet valve, Tracker purge and brake air isolation valve, Tracker purge and brake air reducer manifold inlet and outlet valves, Backup tracker purge and brake air manifold outlet plug valve located inside the structure pier.

Refrigeration Dryer

Backup Purge & Brake Air Reducer

1.3.5 Start the compressor by using the electrical box adjacent to the compressor as shown above. The compressor should increase system pressure to 110-psig out of the regulator, and the receiver pressure should be maintained between 108-psig and 160-psig.

1.3.6 Closely monitor, periodically throughout the day and night, that the receiver is being properly drained.

1.4 Tracker Purge and Brake Air System Shutdown

Caution: Shutting down the tracker purge and brake air system will cause the tracker and the air systems in the spectrograph rooms to be inoperable. The structure lift air system can be used to backup the tracker purge and brake air system as described in section 4.0 below.

1.4.1 Shut the purge and brake air system isolation valve.

1.4.2 Turn off the dryer.

1.4.3 The air compressor provides shop air also. Therefore, the compressor does not need to be shutdown unless desired.

2.0 Infrequent/Abnormal Operation

2.1 Supplying the tracker purge and brake air system using the structure lift air system.

2.1.1 Initial Conditions:

2.1.1.1 The tracker purge and brake air system is shutdown per Section 3.4 above and is inoperable.

2.1.1.2 It is desired to operate the tracker/telescope and spectrographs.

2.1.1.3 The structure lift air system is in operation as described in Section 3.1.

2.1.2 Shut or check shut the tracker purge and brake air isolation valve.

2.1.3 Slowly open/check open the backup tracker purge and brake air regulator inlet and outlet valves.

2.1.4 Adjust the regulator outlet pressure to about 95-psig to 100-psig as required.