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There are multiple hazardous areas in the DKIST and support facilities, this document address only areas of hazard during fully automated control. In particular, areas in current design that needed DKIST input on hazards requiring mitigation due to the presence of personnel. Most areas are simply too hazardous to allow personnel entry during fully automated control. Some areas such as the telescope enclosure floor level and coudé Coudé rotator will have the need for personnel entry during under some circumstances. Starting from the upper enclosure moving down, we will discuss each area and the design conclusions for each. See the summary table section 13at 13 at the end of this discussion. Section 14 contains a diagram that shows the major hazardous zone in a schematic format to aid in understanding access to the various hazardous areas.
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In summary, for fully automated operational access by personnel into hazardous zones, the motion must be speed inhibited to <250 mm/sec, have minimum clearance from the operating space of 0.45 m, and present no other severe hazard due to the equipment, or configuration of the space and moving items.
ENCLOSURE - UPPER LEVELS
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Enclosure – Upper Levels
The enclosure upper levels for the purpose of this section include the upper platforms, TEOA platform and the lifting platform. include:
Valve Station Platform
TEOA Platform
Ventilation Gates Maintenance Platform
Upper Vent Gates Platform
Upper Platform
Bridge Crane Platform
This does not include the enclosure floor on the telescope level (see below, section 3 Telescope Level Floor).
Entry to the upper levels is by stairs from the telescope level.
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There are numerous serious hazards here to both personnel and equipment (including the primary mirror) so there is no personnel entry allowed during fully automated control. The stairs will be protected by gates that can be locked for fully automated controlare protected by trapped keys bolt interlocks at the telescope level.
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Access to the upper levels of the enclosure is controlled via two gates on the stairs leading upward from the telescope floor level. Both gates will are be electronically locked (controlled by the GIS) mechanically locked and access granted is possible only when enclosure azimuth motion is inhibited.
A trapped key that inhibits enclosure azimuth motion when removed will be located in the control roomat Cabinet 001 on the utility level. This key is then inserted into a key exchange unit that frees several secondary keys ( secondary keys are also used for other zones that have hazards created by telescope azimuth motion). This secondary key is required to be inserted in either of the control panels located by trapped key bolt interlock located on the gates at the bottom of the stairs. Insertion of this key unlocks the gate, releases two personnel safety keys, which must be carried by personnel entering the hazardous zone. The secondary key is trapped until the two personnel safety keys are returned and the door gate is re-locked. Then the secondary key can be returned to the key exchange unit (and provided all secondary keys are present) to allow the primary key to be released and re-inserted into the main control panel to permit enclosure azimuth motion.
TELESCOPE FLOOR LEVEL
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| Anchor | ||||
|---|---|---|---|---|
|
The telescope level floor level hazardous zones include hazardous zone includes:
the fixed floor
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portions of the telescope azimuth floor
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the enclosure azimuth floor.
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Entry to this level is through the LU/LA elevator or the stairway (doors 701A and 701B) on to the fixed floor from the “doghouse”. Two doors also provide access to the enclosure exterior that allow use of ladders to reach the catwalk.
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Hazards and controls
Entry on to the fixed floor during fully automated control presents no serious hazards as the telescope movement envelope does not reach it and equipment on the rotating floors (telescope and enclosure) shall be kept at least ~500 mm from the edge of the fixed floor[SS1] . Note that the stairway/elevator “doghouse” is close to the enclosure floor. Also, from the top of the “doghouse” the telescope movement envelope can be reached.
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While no hazard is present immediately upon exiting either of the doors (701A and 701B)[SS2] , these door doors represent the last barrier barriers between personnel and various hazards. There is also a second means of egress from the enclosure and that is from doors that connect to the external ladders, (these doors only open from the inside). These doors will be monitored. Access to the telescope floor level is controlled via doors 701A and 701B. Doors 701A and 701B will be electronically locked (controlled by the GIS) and access granted only when enclosure azimuth rotation is limited to a safe speed. The exterior enclosure doors will be mechanically locked and monitored by the GIS. The GIS will inhibit enclosure azimuth rotation if either of the exterior doors is opened. A trapped key that limits enclosure azimuth motion to a safe speed when removed will be located in the control room. This key is then inserted into a key exchange unit that frees several secondary keys (secondary keys are also used for other zones that have hazards created by enclosure azimuth motion. This secondary key is required to be inserted in either of two control panels located by Door 701A and 701B. Insertion of this key unlocks the corresponding door 701A or 701B, releases two personnel safety keys, which must be carried by personnel entering the hazardous zone. The secondary key is trapped until the two personnel safety keys are returned and the door is re-locked. Then the secondary key can be returned to the key exchange unit (and provided all secondary keys are present) to allow the primary key to be released and can be re-inserted into the main control panel to permit full-speed Enclosure Azimuth Drive motion.Table 3‑1
Telescope azimuth floor motion speed analysis
Telescope |
Azimuth Floor 12.5 m diameter |
°/s | RPM | mm/s | m/s |
Diameter | Circ. |
m/ |
° | ||||||
2 | 0.33 | 219 | 0.22 | 12.5 | 39.4 | 0.11 |
1.5 | 0.25 | 164 | 0.16 |
12.5
39.4
1 | 0.17 | 109 |
0.11
12.5
0.11 | |||
0.5 | 0.08 | 55 | 0.05 |
12.5
39.4
0.11
[*]. No entry is allowed during fully automated control. This area is equipped with physical barriers to prevent entry. Entry is controlled by two gates (Gate “202” and Gate “257”).
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For entry a trapped key that inhibits telescope motion when removed will be located in the control room. This key is then inserted into a key exchange unit that frees several secondary keys (secondary keys are also used for other zones that have hazards created by telescope motion, such as the telescope Nasmyth platforms, see Telescope Azimuth Floor to Telescope Nasmyth Platforms below). This secondary key is required to be inserted in to the gates that control access to the telescope motion envelope. Insertion of this key unlocks the gate and releases two personnel safety keys, which must be carried by personnel entering the hazardous zone. The secondary key is trapped until the two personnel safety keys are returned and the door is re-locked. Then the secondary key can be returned to the key exchange unit (and provided all secondary keys are present) to allow the primary key to be released and re-inserted into the main control panel to permit telescope motion.
[†] on the Nasmyth platform from the movement of the altitude axis. These stairways shall be guarded and locked for fully automated control. A trapped key that inhibits telescope motion when removed will be located in the control room. This key is then inserted into a key exchange unit that frees several secondary keys (secondary keys are also used for other zones that have hazards created by telescope motion; see Telescope Azimuth Floor to Telescope Center Span above). This secondary key is required to be inserted in to the gates that control access to the telescope motion envelope. Insertion of this key unlocks the gate and releases two personnel safety keys, which must be carried by personnel entering the hazardous zone. The secondary key is trapped until the two personnel safety keys are returned and the door is re-locked. Then the secondary key can be returned to the key exchange unit (and provided all secondary keys are present) to allow the primary key to be released and re-inserted into the main control panel to permit telescope motion.
it is imperative that no equipment on the enclosure shall be within 450 mm of the edge of the fixed floor.[SS3] Table 3‑2 Enclosure Floor 19.3 m inner diameter Enclosure Floor
Enclosure Floor 19.3 m inner diameter | ||||||
Deg./s | RPM | mm/s | m/s | Dia. - m | Circ. - m | m/deg. |
2 | 0.33 | 337 | 0.34 | 19.3 | 60.6 | 0.17 |
1.75 | 0.29 | 295 | 0.29 | |||
19.3
60.6
1.5 | 0.25 | 253 | 0.25 |
19.3
60.6
1 | 0.17 | 168 |
0.17
19.3
0.17 | |||
0.5 | 0.08 | 84 | 0.08 |
19.3
60.6
Various means to reduce or eliminate this hazard were analyzed to include both procedural controls (disallow entry during slews) and engineering controls (slow speed control). Although slow speed control has the potential for cost and operations impact, engineering solutions are a more effective way to control hazards than procedures.
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The operational impact of enclosure slow speed control was analyzed and documented in TN-0003, Alt-Azimuth Blind Spot and the DKIST. Maximum speed is used at noon to reposition the enclosure aperture for the afternoons observing. In summary of TN-0003, the operational impact of speed limiting the enclosure while personnel are on the telescope level is negligible. See TN-0003 in C:\DKIST File Vault\SysDocs\1.0 Tel\1.1 TMA\Docs & Images\Tech Notes & Reports\TN-0003-Zenith Blind Spot. The enclosure design has passed FDR and the contractor has included slow speed control under a category of Special Operations. Design and budget impacts to introducing a speed limiting device to the enclosure motors cannot be analyzed fully at this point.
SERVICE RING ACCESS PLATFORM
General
The service ring access platforms are entered from two stairways in the enclosure cable wrap level. No personnel shall be allowed entry during fully automated control.
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Telescope Mount Zone
The Telescope Mount Hazardous Zone includes:
Nasmyth Platforms
Telescope Central Span
Telescope End Stop Pit
Access to the Telescope Mount Hazardous Zone is controlled by several means. Access to the Nasmyth Platforms is controlled by mechanical trapped key bolt interlocks located on each access stairway. Access to the Telescope Central Span is controlled by mechanical trapped key bolt interlocks located at gates at the front and rear of the telescope.
Potential Hazards
Telescope Altitude motion
M1 Cover motion
Controls
Access to the
Service Ring Access
The Service Ring Hazardous Zone consists of:
Enclosure Cable Wrap Level
Service Ring Level
Service Ring Access Platforms
Enclosure Service Ring
Telescope Service Ring
No personnel shall be allowed entry during fully automated control.
The enclosure cable wrap level is accessed through doors 501A, 502A and two hatches (FH-01 and FH-02) to the outer utility level below.
The service ring access platforms are entered from two stairways in the enclosure cable wrap level.
Hazards
Controls
Entry to the Service Ring Hazardous Zone is controlled at door 501A and 502A by Guard Locking Switches which lock the door via power to unlock solenoids controlled by Rotary Trapped Key Interlock Switches. To enter the area both Telescope Azimuth and Enclosure Azimuth rotation is inhibited.
Entry can also be gained by two floor hatches (FH-01 and FH-02). The ladder way to reach each hatch is controlled via a Trapped Key Bolt Interlock.
| Warning |
|---|
Access via the floor hatches do not inhibit Telescope Azimuth motion. |
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Hazards and controls
TMA power and electronics racks hang down into this area creating serious fall, crush and pinch hazards. Entry to this level is controlled by enclosure cable wrap level doors 501A and 502A [SS4] 502A (see section 7 Enclosure Cable Wrap Level).
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Catwalk Zone
General
The catwalk is affixed to the S&O building and personnel are exposed to the motion of the rotating enclosure. It provides access to the lower enclosure and weather stations. There are ladder ways down to the ground level with landings and exit doors at lower levels which can serve as means of emergency egress (Figure 10).
An exterior ladder way on the S&O building also provides access to the catwalk level from below (Figure 10).
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impact hazard to personnel on the catwalk[SS5] . Access to the catwalk is controlled by door 402D from the vestibule on the utility level to the catwalk. Access is also possible from the landing near door 402B or by descending from ladders on the exterior of the enclosure, (see section 2) During fully automated control no personnel shall be allowed onto the catwalk and door 402D interlocked and emergency exit doors shall be alarmed and monitored. Access to the catwalk is controlled via door 402D. Door 402D will be electronically locked (controlled by the GIS) and access granted only when telescope azimuth motion is inhibited. The GIS will inhibit enclosure azimuth rotation if Door 402D is opened. The catwalk can also be accessed from the exterior ladder way through doors 210B, 308D, and 402B. Doors 210B, 308D, and 402D will be mechanically locked and monitored by the GIS. The GIS will inhibit enclosure azimuth rotation if any of these three doors are opened. A trapped key that inhibits enclosure azimuth motion when removed will be located in the control room. This key is then inserted into a key exchange unit that frees several secondary keys (secondary keys are also used for other zones that have hazards created by enclosure azimuth motion. This secondary key is required to be inserted in a control panel located by Door 402D. Insertion of this key unlocks Door 402D, releases two personnel safety keys, which must be carried by personnel entering the hazardous zone. The secondary key is trapped until the two personnel safety keys are returned and the door is re-locked. Then the secondary key can be returned to the key exchange unit (and provided all secondary keys are present) to allow the primary key to be released and re-inserted into the main control panel to permit enclosure azimuth motion. Figure 9 Enclosure catwalk Secure ladder way Door 308D Door 210B Door 402B Figure 10 Exterior ladder ways to the catwalk level
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ENCLOSURE SERVICE RING
General
The enclosure service ring is only accessed from the Service Ring Access Platforms (see section 4 Service Ring Access Platform) which are accessed from the enclosure cable wrap level and no entry is allowed during fully automated control.
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Enclosure Cable Wrap Level
General
The enclosure cable wrap level is accessed through doors 501A, 502A and two hatches (FH-01 and FH-02) to the outer utility level below.accessed from the enclosure cable wrap level and no entry is allowed during fully automated control.
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Enclosure Cable Wrap Level
General
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Due to the numerous pinch and crush hazards of the enclosure cable wrap and enclosure equipment no operational entry is allowed. Doors and hatches shall be interlocked to prevent entry during fully automated control.[SS6]
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Access to the enclosure cable wrap is controlled via doors 501A and 502A as well as floor hatches FH-01 and FH-02. Door 501A and Door 502A will be electronically locked (controlled by the GIS) and access granted only when enclosure azimuth motion is inhibited. The GIS will inhibit enclosure azimuth rotation if either Door 501A or 502A is opened. Floor hatches FH-01 and FH-02 will be mechanically locked and monitored by the GIS. The GIS will inhibit enclosure azimuth rotation if either floor hatch FH-01 or FH-02 is opened. For maintenance purposes, there are additional removable steel plates in the floor near FH-01 to allow for larger pieces of equipment to be installed. These must be in place to allow operation. A trapped key that inhibits enclosure azimuth motion when removed will be located in the control room. This key is then inserted into a key exchange unit that frees several secondary keys (secondary keys are also used for other zones that have hazards created by enclosure azimuth motion). This secondary key is required to be inserted in a control panel located by Door 501A. Insertion of this key unlocks Door 501A, releases two personnel safety keys, which must be carried by personnel entering the hazardous zone. The secondary key is trapped until the two personnel safety keys are returned and the door is re-locked. Then the secondary key can be returned to the key exchange unit (and provided all secondary keys are present) to allow the primary key to be released and re-inserted into the main control panel to permit enclosure azimuth motion.
UTILITY FLOOR LEVEL
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.
Utility Level Inner Pier Zone (Telescope Cable Wrap)
The Utility Level inner pier hazardous zone contains the telescope cable wrap which presents a significant pinch/crush hazard.
Access to the Utility Level Inner Pier is control via door 403A and gate ‘21’.
| Warning |
|---|
Gate ‘21’ is only monitored and not physically locked. |
This level includes an inner and outer pier area. The inner pier will be separated by a safety barrier to prevent inadvertent entry, since the walls were removed from the design. The inner area contains the mount cable wrap and is accessed by gate “403A” and another gate, “21” on the opposite side. The outer pier has several doors and has access to the emergency exterior ladder ways.
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Hazards and controls
Serious crush and pinch hazards exist around the Catwalk. No personnel access is allowed into the utility level inner pier during fully automated control and gate at former location of door 403A shall be interlocked. Access is allowed to the utility level outer pier.
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A trapped key that inhibits telescope azimuth motion when removed will be located in the control room. This key is then inserted into a key exchange unit that frees several secondary keys (secondary keys are also used for other zones that have hazards created by telescope azimuth motion. This secondary key is required to be inserted in a control panel located by Door 403A. Insertion of this key unlocks Door 403A, releases two personnel safety keys, which must be carried by personnel entering the hazardous zone. The secondary key is trapped until the two personnel safety keys are returned and the door is re-locked. Then the secondary key can be returned to the key exchange unit (and provided all secondary keys are present) to allow the primary key to be released and re-inserted into the main control panel to permit telescope azimuth motion.
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Coudé Lab Zone
General
The Coudé floor level has an inner and outer area. The inner rotator area presents the most needs for access to a hazardous zone during fully automated control. Instrument scientists and engineers desire regular access to the Coudé rotator during some operations. The lab can be entered by doors 307A, 308C and the “rec room” ladder way (TBD)[SS7] .
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Depending on the type of operations, the probability for entry differs. During diffraction limited seeing, in general, no personnel would be present in the coudé rotator. During seeing limited operations, personnel are likely present and during coronal observations personnel frequent the area.
There is a fixed floor and a rotating floor 16.5m in diameter. During tracking, the speed of the rotator is well below the RIA slow speed control (seeTable 9‑1
Coudé rotator motion speed analysis
Coudé Rotator Floor 16.5 m dia. | ||||||
Deg./s | RPM | mm/s | m/s | Dia. - m | Circ. - m | m/deg. |
6 | 1 | 865 | 0.87 | 16.5 | 51.9 | 0.14 |
4 | 0.67 | 577 | 0.58 | |||
16.5
51.9
2 | 0.33 | 288 | 0.29 |
16.5
51.9
1.75 | 0.29 | 252 | 0.25 |
16.5
51.9
1 | 0.17 | 144 |
0.14
16.5
0.14 | |||
0.5 | 0.08 | 72 | 0.07 |
16.5
51.9
Hazards and controls
The outer pier presents no additional hazards during fully automated control and can be entered. The Coudé lab rotator floor edge area has the potential for serious crush and pinch hazards and therefor the rotator should be speed inhibited to 1.75°/sec (250 mm/sec) when personnel are in the Coudé lab. For example the WFC optical bench is very close to the outer edge of the rotating floor. For a worker be in the Coudé lab, and for it to be able to rotate, it would have to be in slow speed control (<250mm/sec) and safety procedures (TBD) to be followed prior to rotation. Railings have been discussed but these could present crush or pinch hazard themselves, depending on where there are placed.
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A trapped key that limits Coudé motion to a safe speed when removed will be located in the control room. This key is required to be inserted in a control panel located by Door 307A. Insertion of this key unlocks Door 307A, releases two personnel safety keys, which must be carried by personnel entering the hazardous zone. The primary key is trapped until the two personnel safety keys are returned and the door is re-locked. Then the primary key is released and can be re-inserted into the main control panel to permit full-speed Coudé Rotator motion.
Mezzanine Floor Level
General
This level includes an inner and outer pier area. The inner area contains the underneath of the Coudé rotator and the instrument cabinets and is accessed by doors 209A and 210A. This area also contains the “Rec Room” in the center of the rotator structure. The “Rec Room” provides ladder access to the center of the inner pier. There is removable ladders which can provide access to the Coudé level[SS8] .
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Hazards and controls
During fully automated control the floor is stationary and the rotator structure and instrument cabinets rotate creating pinch and crush hazards. Someone standing or on a ladder on the fixed floor working on the electronic cabinets that could move and impact a worker and cause a fall and/or catch on something and pinch/crush hazard, etc. During fully automated control or any motion controlled from outside the room the inner pier mezzanine level shall not be accessible to personnel and the entry door(s) shall be interlock to prevent entry.
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The “Rec Room” is accessible via one of two ladders in the Mezzanine Inner Pier Area. These ladders are permanently installed. The “Rec Room” is also accessible via a removable ladder from the Coudé Rotator Platform above. The hatches in the floor of the Coudé Rotator Platform will be mechanically locked and monitored by the GIS. The GIS will inhibit Coudé Platform rotation if either hatch is opened.[SS1]
The addition of video and audio communication will help protect workers, but this control alone does not adequately mitigate the hazard of accessing the cabinets that can move “unexpectedly” from a fixed floor. Purely procedural mitigations (make sure you check the cameras) should not to be used as the only control of such a serious hazard.
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The door from the Coudé “rec room” to the mezzanine will be interlocked during normal operation to prevent personnel exiting to the mezzanine with the Coudé rotator in motion.
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Ground Floor Inner Pier
General
This level includes an inner and outer pier area and the inner coudé pier. The inner coudé pier area contains the coudé rotator cable wrap and is accessed by door 110 A. The center of the inner coudé pier cable wrap area is accessible from the ladder from the coudé pier inner mezzanine level above, which in turn is accessed from two hatches and ladders in the “rec room” floor.
Access is typically not required during while the Coudé Rotator is in motion. Daily pre-operations check will include a visual inspection of this area.
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Hazards and controls
The Coudé Platform Cable Wrap occupies a large portion of the Inner Pier. This represents numerous pinch/crush hazards as well as unexpected startup hazard. To prevent unauthorized access to the Coudé Platform Cable Wrap, Door 110A will be electronically locked and access granted only when Coudé Platform rotation is inhibited.
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During fully automated control, the inner coudé pier shall not be accessible to personnel and the entry door shall be interlocked to prevent entry.
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Trapped Key Plan
Based upon the idea that no single key can be in two places at once, trapped key interlocks (also known as key interlock systems or “Castell” key interlocks) can be configured to provide that a predetermined sequence of events takes place or that hazards have been reduced before personnel can become exposed to them.
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The key naming scheme presented below is just for reference, actual key labels and types will be coordinated during installation.
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Coudé Hazardous Zone
Figure 23 shows the general arrangement of trapped keys for access to hazardous areas of the Coudé Rotator. While the Coudé Rotator is stopped, personnel may remove primary key ‘AA’ from the control panel, this removes the permissive signal to the Coudé Rotator LIC. Primary key ‘AA’ can open either Door 110A (see Figure 21) or Door 209A (see Figure 18) which allow access to the inner pier area. Unlocking a door releases personnel keys ‘BA’ and ‘CA’ which must be taken into the hazardous area.
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Coudé Lab Access
Figure 24shows the arrange of keys for entering the Coudé Lab. Removing primary key ‘DA’ requires the Coudé Lab rotator to be travelling at or below the safe limited speed (SLS) of 2°/sec. Once the primary key has been removed Coudé Lab rotation is limited to less than 2°/sec. Primary key ‘DA’ may then be used to open door 307A (see Figure 16) to access the Coudé Lab, which releases two trapped keys ‘EA’ that must be taken into the lab, a third key is available to insert into a key exchange unit that release six additional keys ‘XA.’
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Telescope Hazardous Zones
The telescope has two primary keys, ‘FA’ and ‘GA’. These control permissive signals to the Azimuth and Elevation axes respectively. Some hazardous areas only require that one axis be inhibited as shown in Figure 25. Telescope azimuth motion must be inhibited to access the utility level via door 403A (see Figure 14) or the cable wrap level inner pier via door 501A or 502A (see Figure 12). To access either telescope platform elevation motion must be inhibited (see Figure 4).
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Note: to get to the telescope mount, access must be through the area controlled by the enclosure floor access, see section 12.4 below.
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Telescope Level Floor Automated Control Access
Figure 27 shows the arrangement for access the enclosure floor area. Similar to the Coudé Lab hazardous zone, this arrangement limits the speed of enclosure rotation to below a safe threshold (1.5°/sec). Primary key ‘UA’ will open either door from the ‘doghouse’ onto the observing chamber floor. Personnel Keys ‘WA’ and/or ‘VA’ must be taken into the hazardous zone.
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Enclosure Hazardous Zones Access
Figure 28 shows the arrangement for inhibiting enclosure rotation. The hazardous zone includes interior service platforms and the exterior catwalk. Primary key ‘PA’ inhibits enclosure rotation when removed. This key opens access points to hazardous areas created by enclosure rotation. Personnel keys ‘RA’, ‘SA’, and ‘TA’ must be taken when entering the hazardous zone. Access to the catwalk is controlled via door 402D (see Figure 8).
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SUMMARY TABLE OF HAZARDOUS ZONES ACCESS
Hazard Areas |
Access Doors1 | Interlock / Lock / Monitoring Type
| ||
| Personnel Access Permitted when… | Notes (Telescope/ | |
Coudé level personnel access adversely affects observations) |
Fully |
Automatic Control | Speed Limited Move/Tracking < 250 mm/s |
Enclosure Upper Levels | Exterior |
701A -
701B -
Exit 1 - im
Exit 2 - im
Enc. stair - tk
Egress Doors | IL | No |
| |
Upper Platforms | Enclosure stairs | TK | Stairs to be gated and interlocked locked (TBD), Vent gates platforms | |
TEOA Platform | TEOA interlocked | |||
Lifting Platform
Telescope |
Fixed Floor
701A -
701B -
Az tower gate barriers - it
Nasmyth stairs - it
Enc. stair - tk
Yes[SS1]
N/A
Mount | Nasmyth Platforms | Nasmyth Stairs | IT | No | N/A | Stairs to be gated and interlocked locked (TBD) |
Center Span | Gates | IT | Yes[SS2] | N/A |
Tele. Movement Envelope
No
N/A
Physical barriers (removable) will prevent entry between towers “crush zone” and to be interlocked trap key |
Tele. Nasmyth Platforms
No
N/A
Stairs to be gated and interlocked locked (TBD)
Enclosure Azimuth Floor
End Stop Chamber | Hatches | IM | ||||
Telescope Floor Level | Fixed Floor | 701A (stairway 2) - 701B (LULA) - | none IT | Yes[SS1] | N/A | Door 701B causes a pinch/crush hazard as it opens into the movement envelope of the telescope. |
Enclosure Azimuth Floor | No | Yes | Stairs to upper platforms to be gated and interlocked locked |
Service Ring Access Platform
501A – m
502A – m
Gate 1 – it
Gate 2 – it
No
Access from enclosure cable wrap level stairs[SS3]
Lifting Platform | No | No | ||||
Catwalk | Exterior | 402D |
Emergency doors
TK | TBD | Access from utility level outside stairs. Outside ladder to grnd/mezz/ coudé/util /catwalk levels | ||
210B 308D 402B | IM | ||||
Service Ring | Service Ring | ||||
501A – m
502A – m
Gate 1 – it
Gate 2 – it
Service Ring Platforms | 501A 502A | IL | No | Access from enclosure cable wrap level stairs[SS3] | |
Enclosure Cable Wrap | Hatch 1 Hatch 2 | TK TK | No | Access from enclosure cable wrap level Only major maintenance access | |
Azimuth Equipment Level |
|
501A – m
502A - m
Hatch 1, 2 – imGate 3 |
IT | No | |
Gate 3 is access to az. equipment level (air knife) | |
Utility Floor Level | Inner Pier |
403A |
Gate 21 – it
IL | No | MAINT mode only – LOTO; Mount cable wrap | ||||
Gate 21 | IT | |||||
Outer Pier
| 402A – N/A 402B – m 402C – N/A 402D – tk |
| Yes | Ladder (1 ea.) to coudé level. Outside ladder to ground/ mezzanine/ coudé/ utility /catwalk levels | ||
Coudé Floor Level | Coudé Lab, Rotator and Fixed Floor | 307A - it 308C - im |
| No | Yes | Other hazard controls also required: high visible marking, audible move warnings, bump sensors, barriers etc. |
Outer Pier
| 308D - m 308E – N/A 305F – N/A |
| Yes | Ladders (1ea) to outer utility level and (2 ea) outer mezz. level. Outside ladder to ground/ mezzanine/ | ||
Coudé/ utility /catwalk levels
| ||||||
Mezzanine Floor Level | Inner Pier
| 209A - it 210A - im Rec room - im |
| No | Coudé Rotator to be inhibited or locked out for access. | |
Coudé Pier Inner Mezzanine | 2 hatches in Rec room floor - im |
| No | Allows access to ground floor inner pier – center of cable wrap | ||
Outer Pier
| 210B – m 211A – N/A |
| Yes | Ladders (2 ea) to outer | ||
Coudé level. Outside ladder to ground/ mezzanine/ |
Coudé/ utility /catwalk levels | ||||||
Ground Floor Level | Coudé Pier Inner | 110A – it |
| No | Coudé Rotator to be inhibited or locked out for access; rotator cable wrap | |
Center of Coudé Pier | ladder |
| No | Accessed by ladders from Coudé pier inner mezzanine level | ||
Outer Pier | 109A,B,C |
| Yes | No interlock/monitoring needed | ||
Outside ladder | N/A - im |
| Yes | Needs security “gate/door” on ground level. Ladder to mezzanine, | ||
Coudé, utility and catwalk levels |
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Note 1, Access Doors:
IT=Interlocked Trapped Key This type of access door can only be unlocked by inserting the correct trapped key. A manual override will be available for egress only. The lock and the door are monitored to ensure that it cannot open during hazardous operation without stopping hazardous motion.
IL=Interlocked Locked This type of access door is locked using a normal keyed locked to inhibit entry. The door may be unlocked for egress from the inside. The door is monitored to ensure that it is not opened during hazardous motion. If the door is opened hazardous motion is stopped until it is manually reset.[r13] IM=Interlocked Monitored This type of access door may inhibit entry or egress. The door is monitored to ensure that it is not opened during hazardous motion. If the door is opened hazardous motion is stopped until it is manually reset.
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TK – Trapped Key This is a door with a trapped key with exchange for opening, and it may or not be electronically monitored.
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State Diagram Of Hazardous Zones Access
Access to the various hazardous zones represents a complex interaction of moving about the facility from “safe” through various barriers to “hazardous zones.” The diagrams that follow represent the various zones and the barriers through which must be breached to access the zone.
There are zones that while technically are “safe” can only be accessed from “hazardous” zones, therefore it is considered part of the hazardous zone (the “rec room” is one example).
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[*]In the area between the mount altitude bearing towers there are a number of pieces of equipment that as the mount moves in altitude sweep close to both the Telescope floor and also close to the M5/M6 Tower. These are Optical Support Structure (OSS) electronics rack and platform, OSS main counterweights and parts of the OSS main structure.
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These access provisions are provided for normal maintenance and were not designed for working on the systems while under TCS control (fully automated control) which could invoke a slew at any time. For these activities it would be necessary to implement ‘other protective’ means which could be a combination of local enabled slow speed operation with temporary access via scaffolding. The same issue exists for encoder alignment where access is needed to an area that has intrinsic crush hazards but must be able to move the axis while adjusting. This is not “normal” inspection / maintenance and so falls under the “specific job hazard and alternative protection means.”
[†] The hazards on the Nasmyth platform include the different relative motion of the OSS trunnion and the bearings system, the manual drive gear, brake discs / brake mechanism, encoder and encoder read head brackets. The most straightforward way to protect personnel from these mechanisms is to limit access to the nasmyth platform during fully automated control.
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If during IT&C or operations some of the thermal or other systems need adjustment or inspection during tracking, then a specific job hazard analysis would be required and then ‘alternative protection’ means would be implemented.
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[SS1]Various parts of the telescope have encroached into with 500 mm of the edge to include pipes, valve handles, stairway base, gate swing radius, elevation cable wrap (crosses over at lowest elevation) et al
[SS2]Door 701A to the stairway open to ~500 mm of the fixed floor edge and door 701B LULA lift to ~230mm of the edge. Parts of the telescope have encroached to and past the fixed floor edge.
[SS3]Need to check. Some rails and duct supports attached to rails likely to exceed.
[SS4]Proposed to be changed to stairway gate interlocks and installing new permanent rails and platform surface to access the mount racks. See section 7
[SS5]Impact is somewhat limited to the 2 ladders and area access could be reviewed.
[SS6]The enclosure cable wrap has an installed mesh barrier. It is proposed to add interlocked gates to the mount service platforms and telescope azimuth equipment level gate and allow access to part of the enclosure cable wrap level during operations and movement. This would also involve replacing the temporary rails and working platforms at the mount service platform level with permanent rails and platform. The floor hatch access to the enclosure drive chamber would remain the same.
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