PFIS Safety Document

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
References
Analysis

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
	Improper attachment or lifting	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
	PFIS mounting works loose	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
		Improper installation	Management signs off on installation
		Handling equipment improperly used	Follow procedure
		Handling equipment improperly used	Train personnel
A.4 Electrical Shock	Exposed wires and connectors	Underrated wires	Use rated components
		Chafed insulation	Route wires correctly
		Chafed insulation	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
	Power left on during maintenance	Failure to 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
	Electrical fault	Overcurrent	Fuses (220VAC) and circuit breakers (+24VDC)
	Electrical overheating	Failure of cooling system	Monitor temperatures
	Glycol pipe bursts or leaks	Bad connections	Inspect connections
	Glycol pipe bursts or leaks	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
		Sensor failure	Replace sensor
B.3 Articulation Arm Runaway	Hardware interlock failure	CPLD failure	Swap in spare interlocks board
		Sensor failure	Design sensor to fail asserted
		Sensor failure	Replace sensor
	Articulation brake failure	Life-cycle failure	Use preventive maintenance
		Jamming	Use preventive maintenance
		Jamming	Cover and protect mechanism
B.4 Major Electronics Failure	Power surge	Lightning	Shut down during storms
		Lightning	Use UPS power
		Noisy power	Use UPS power
		Overloaded circuits	Use proper loads
	Moisture in electronics	Condensation	Shut down for condensing conditions
	Moisture in electronics	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
	Degradation of NaCl optics	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
	System leaks	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
C.3 Shutter Failure	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
C.4 Motor Failure	Component failure	Low quality components	Use good components
C.5 Fiber Communications Failure	Damage to cable wrapup	Poorly routed fibers	Route fibers correctly
C.5 Fiber Communications Failure	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
	Bad design	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
D.2 Computer Failure	Disk crash	Random failure	Use spare disk, pre-loaded with system