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SEMI S2-0703a E © SEMI 1991, 2004 41 Potential Hazard Recommended Control Method Design Considerations Control of ignition sources. NFPA 70 (NEC) Class I, Div. 2 wiring methods, intrinsically safe components, or nitrogen…

SEMI S2-0703a

APPENDIX 3

DESIGN GUIDELINES FOR EQUIPMENT USING LIQUID CHEMICALS

— Design and Test Method Supplement Intended for Internal and

Third Party Evaluation Use

NOTICE: The material in this appendix is an official part of SEMI S2 and was approved by full letter ballot

procedures on December 15, 1999 by the North American Regional Standards Committee.

A3-1 Introduction

A3-1.1 This appendix provides specific technical

information relating to Section 23. In general, it

provides information on potential hazards,

recommended control methods, and design

considerations.

A3-1.2 This appendix is not intended to limit hazard

evaluation methods or control strategies (e.g., design

principles) employed by manufacturers. Alternative

methods are acceptable if they provide an equivalent

level of hazard control.

A3-1.3 This appendix is intended to be used as a

starting point for reference during equipment design.

An example would be during a formal hazard analysis

in a brainstorming session.

Table A3-1 Liquid Chemicals

Potential Hazard Recommended Control Method Design Considerations

Containment, control, and alarm

notification for spills, leaks or vapors.

Appropriately sized secondary containment (minimum 110%

volume of entire contents)

Equipment exhaust

Leak sensors to initiate auto shutdown.

Controlled access to chemical

containment areas.

Door/access cover interlocks that automatically depressurize the

area of the system being accessed.

Exposure to

operators

Control of access to point-of-

operation hazards.

Physical guarding/presence-sensing devices

Control of chemical delivery

pressure; control of residual

chemicals.

Depressurization upon system failure, interlock activation, or

normal shutdown

Transparent doors/covers allow visual inspection.

Exposure to

maintenance

personnel

Serviceability Built-in system purge and flush capabilities

System components accessible and easy to service.

Chemical resistance/compatibility

Appropriate materials used for equipment construction and

components.

General

equipment and

component

failure

Pressure rating

Pressurized systems designed to withstand 150% of maximum

foreseeable pressure, or provide a suitable relief valve.

Durable bulk chemical containers

Use of approved (e.g., DOT, UN Dangerous Goods) containers

in bulk distribution systems.

Control of pressurized vessels and

piping.

Provide visual pressure indicators with or without alarms.

Pressurized vessels and piping are designed and built to

recognized standards.

Spill control Automatic system pressure check prior to allowing dispense.

Use of normally closed valves on distribution lines.

Chemical

delivery system

leak

Drum change-out controls Over-fill sensors on chemical baths

Monitoring for excess flow.

Keyed and color-coded quick-connects

SEMI S2-0703a

Potential Hazard Recommended Control Method Design Considerations

Control of ignition sources.

NFPA 70 (NEC) Class I, Div. 2 wiring methods, intrinsically

safe components, or nitrogen-purged enclosures

Physical separation of ignition sources and/or potentially

flammable atmospheres.

Use of low voltage to reduce the risk for ignition.

Control of static electricity (i.e., one

type of ignition source).

Maintain ground continuity

Fire

Heat/fire/chemical detection

Limiting concentrations of fuels and

oxidizers.

(No consensus for a specific recommendation at the time of

publication of this guideline.)

SEMI S2-0703a

APPENDIX 4

IONIZING RADIATION TEST VALIDATION — Design and Test Method

Supplement Intended for Internal and Third Party Evaluation Use

NOTICE: The material in this appendix is an official part of SEMI S2 and was approved by full letter ballot

procedures on December 15, 1999 by the North American Regional Standards Committee.

A4-1 Introduction

A4-1.1 This appendix provides specific technical information relating to Section 24. In general, it provides

information on hazard evaluation methods, examples of control strategies, and test validation criteria.

A4-1.2 This appendix is not intended to limit hazard evaluation methods or control strategies (e.g. design

principles) employed by the manufacturers. Alternative methods are acceptable if they provide an equivalent level of

hazard control.

A4-1.3 Test validation criteria are generally referenced from the applicable internationally recognized standard. It is

the users responsibility to ensure that the most current revision of the standard (or its national equivalent) is used.

Table A4-1 Ionizing Radiation

Ionizing

Radiation Type

Emission Limit

microsievert/hr

(millirem/hr)

Test Method

X or Gamma Operator

2 Sv/hr

(0.2 mrem/hr)

Direct doserate measurement with an Ion Chamber (or equivalent) calibrated

to ± 10% of true doserate at the surface of the equipment (or at the closest

approach) in all areas where the operator may have access with the ionizing

radiation source active.

X or Gamma Maintenance and Service

10 Sv/hr

(1 mrem/hr)

Direct doserate measurement with an Ion Chamber (or equivalent) calibrated

to ± 10% of true doserate during simulated maintenance and service

procedures. Measurements should be made at the surface emitting the

ionizing radiation or the closest approach to the emitting surface with the

ionizing radiation source active.

NOTE: For these measurements, panels and/or shields should be removed

only if removal is required for maintenance or service activities.

A4-2 Basic Radiation Control Methods

Time — If the radiation field exists and it must be entered, then minimize the time spent in the field to minimize the

exposure to the individual. This gives a linear dose reduction.

Distance — If the radiation field is present, stay as far away form the source as possible to perform the required

tasks. Dose is reduced by the square of the distance from the source.

Shielding — If the radiation field is intense and the source is small, shielding the source is generally the most

practical.

Quantity — If there exists an opportunity to minimize the amount of radiation or radioactive material that is required

for the task, then the exposure can be minimized also.