Southern African Large Telescope

Prime Focus Imaging Spectrograph

Safety Analysis

SALT-3170AE0005

Jeffrey W Percival

Modification Record
Version Date Comments
1.0 18-Mar-2003 CDR Version
2.0 18-Mar-2003 Move to tabular layout

Table of Contents:

Introduction

This note presents the safety analysis for the Prime Focus Imaging Spectrograph (PFIS) subsystem of the Southern African Large Telescope.

In numbering the events, we choose X from this table:

Code Category Description
A Catastrophic Failure may result in severe injury, death or major damage to the telescope
B Critical Failure may result in minor injury and also interruption of telescope operation for more than one week
C Marginal Failure may result in interruption of telescope operation and cannot be repaired the same night
D Negligible Failure may result in interruption of telescope but can be repaired the same night

References

Document References
Document # Name
1000AA0030 SALT Safety Analysis
3300AE0011 SALTICAM Safety Analysis

The referenced documents present the project's safety definitions and the Safety Analysis Procedure. We will not reproduce them here.

Analysis

Catastrophic events

Event First Level Causes Second Level Causes Preventive Measures
A.1

PFIS Dropped in Handling

Crane failure Crane not certified before use Certify crane before use with weights
Improper attachment or lifting Inexperienced crane operator Use experienced crane operators; practice with weights
Attachment and lifting procedure not followed Management signs off on procedure and work order
A.2

PFIS falling into telescope

PFIS attached incorrectly Installation procedure not followed Management signs off on installation procedure and work order
PFIS mounting works loose Fasteners not torqued properly Use proper torques
Vibration Use lock nuts and locking compounds
Articulation bearing failure Bearing not rated for load Select bearing rated for load + margin
A.3

Tools & components dropped into telescope during maintenance

Loose tools Untrained personnel Train personnel
No safety net Use safety net
No attach lines Keep tools attached
Unsecured components Improper installation Follow procedure
Management signs off on installation
Handling equipment improperly used Follow procedure
Train personnel
A.4

Electrical Shock

Exposed wires and connectors Underrated wires Use rated components
Chafed insulation Route wires correctly
Routine inspection of cable loops
High voltage on open connector Interlock HV connector to cut AC to the etalon controllers
Power left on during maintenance Failure to follow procedure Follow procedure
Train personnel

Critical Events

Event First Level Causes Second Level Causes Preventive Measures
B.1

PFIS Catching Fire

Electrical fault Short circuit Periodic inspection of insulation & connectors
Overcurrent Fuses (220VAC) and circuit breakers (+24VDC)
Electrical overheating Failure of cooling system Monitor temperatures
Glycol pipe bursts or leaks Bad connections Inspect connections
Bad tubing Use good tubing
B.2

Etalon and Grating Collision

Hardware interlock failure CPLD failure Swap in spare interlocks board
Sensor failure Design sensor to fail asserted
Replace sensor
B.3

Articulation Arm Runaway

Hardware interlock failure CPLD failure Swap in spare interlocks board
Sensor failure Design sensor to fail asserted
Replace sensor
Articulation brake failure Life-cycle failure Use preventive maintenance
Jamming Use preventive maintenance
Cover and protect mechanism
B.4

Major Electronics Failure

Power surge Lightning Shut down during storms
Use UPS power
Noisy power Use UPS power
Overloaded circuits Use proper loads
Moisture in electronics Condensation Shut down for condensing conditions
Rain Close dome
B.5 Damage to Optics Coatings Damage Unintentional contact Use covers for exposed surfaces during maintenance
Degradation of NaCl optics Poor design Review design
Seal failure Periodic inspection

Marginal Events

Event First Level Causes Second Level Causes Preventive Measures
C.2

Minor Electronics Failure

Tube failure Low quality components Use good components
System leaks Bad connectors Use good connectors
Poor connections Double-check connections
C.2

Minor Electronics Failure

Component failure Random failure Diagnose, replace with spare boards
C.3

Shutter Failure

Life-cycle failure Failure of preventive maintenance Use preventive maintenance
Jammed mechanism Foreign Materials Inspect and clean
C.4

Motor Failure

Improper use (e.g. running against brake or detente) Hardware interlock failure Use spare interlock board
Component failure Low quality components Use good components
C.5

Fiber Communications Failure

Damage to cable wrapup Poorly routed fibers Route fibers correctly
MXI Interface card failure Random failure Swap in spare cards
C.6

Control Lost to Hackers

Unprotected access from outside world Control LAN connected to Internet Disconnect control LAN from Internet

Negligible Events

Event First Level Causes Second Level Causes Preventive Measures
D.1

Slitmask, Grating, Filter Magazine Jam

Bad design Lack of review Careful review
Lack of testing Test under realistic conditions
Insertion error Inexperienced personnel Train personnel
D.2

Computer Failure

OS crash Using MS Windows Live with it
Disk crash Random failure Use spare disk, pre-loaded with system