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SEMI S2-0703a E © SEMI 1991, 2004 76 RELATED INFORMATION 13 SURFACE TEMPERATUR E DOCUMENTATION NOTICE : This rel ated information i s not an of ficial part of SEMI S2 and was de rived from practical application by task f…

SEMI S2-0703a

RELATED INFORMATION 12

LIGHT TOWER COLOR AND AUDIBLE ALERT CODES

NOTICE: This related information is not an official part of SEMI S2 and was derived from practical application by

task force members. This related information was approved for publication by vote of the responsible committee on

October 21, 1999.

R12-1 Colors for Light Towers

R12-1.1 Where used for safety, a light tower should have the following characteristics:

Table R12-1 Light Tower Color Code

Color Explanation Examples

Red Hazardous, dangerous or abnormal

condition requiring immediate

attention

Pressure/temperature out of safe limits;

Voltage drop; Breakdown

Overtravel of a stop position

Indication that a protective device has stopped the machine, e.g.,

overload

Yellow Abnormal, caution/marginal condition;

Change or impending change of

critical condition requiring monitoring

and/or intervention (e.g., by re-

establishing the intended function)

Pressure/temperature exceeding normal limits

Tripping of protective device Automatic cycle or motors running; some

value (pressure, temperature) is approaching its permissible limit.

Ground fault indication. Overload that is permitted for a limited time.

Green Normal condition; machine ready Pressure/temperature within normal limits

Indication of safe condition or authorization to proceed. Machine ready

for operation with all conditions normal or cycle complete and machine

ready to be restarted.

R12-2 Audible Alert (Buzzer) Code

R12-2.1 Where used for safety, audible alert (buzzer) for the light tower should have the following characteristics:

Table R12-2 Light Tower Buzzer Code

Color Audible Alert (Buzzer)

Red Continuous

Yellow Intermittent

Green Intermittent/no sound (selectable)

SEMI S2-0703a

RELATED INFORMATION 13

SURFACE TEMPERATURE DOCUMENTATION

NOTICE: This related information is not an official part of SEMI S2 and was derived from practical application by

task force members. This related information was approved for publication by vote of the responsible committee on

October 21, 1999.

The following is some of the research leading to the

values in Table 1 in Section 18 of this guideline.

R13-1 The proposed Hazardous Temperature Limits

were derived from UL1950

and IEC950

by adding

ambient temperature (25°C) to the maximum

temperature rise allowed for external parts of

information technology equipment. Because several

SEMI members have questioned whether these limits

might subject operators and maintenance personnel to

contact with potentially hazardous temperatures, a

review has been done of several other sources of

suggested temperature limits.

R13-2 The proposed hazardous surface temperatures

for handling and touching of metal handles, knobs, etc.,

for brief periods in normal use is 60°C. Assuming a

brief handling time to be 5 seconds or less, this limit is

supported in MIL-STD-1472

, MIL-HDBK-759A

and EN563

(which are the same or more conservative

by 2°C), and is equal to the pain and tissue damage

threshold listed in the Human Factors Design

Handbook

. Thus, this temperature limit seems

appropriate for momentary (five seconds or less)

contact with uncoated metal handles, knobs, etc., and

other material with high thermal conductivity.

R13-3 The proposed hazardous surface temperatures

for handling and touching of glass/porcelain handles,

knobs, etc., for brief periods in normal use is 70°C.

This temperature limit is supported by MIL-STD-1472

and EN563. MIL-HDBK-759 is not applicable because

it must be assumed that it applies only to material with

high thermal conductivity.

R13-4 The proposed hazardous surface temperatures for

handling and touching of plastic/rubber handles, knobs,

etc., for brief periods in normal use is 85°C. This

12 UL 1950, Safety of Information Technology Equipment, 1989

(Underwriters Laboratory Standard).

13 IEC 950, Safety of Information Technology Equipment, 1986

(International Electrotechnical Commission Standard).

14 MIL-STD-1472D, Human Engineering Design Criteria for

Military Systems, Equipment & Facilities (Military Standard).

15 MIL-HDBK-759A, Handbook for Human Engineering Design

Guidelines, 1981 (Military Handbook).

16 EN 563, Safety of Machinery – Temperatures of Touchable

Surfaces, 1994 (European Normative Standard).

17 Human Factors Design Handbook, Second Edition, Woodson,

Tillman & Tillman, 1992 (Reference).

temperature limit is similarly supported by MIL-STD-

1472 and EN563. MIL-HDBK-759 is not applicable.

R13-5 The proposed hazardous surface temperatures

for continuous handling and touching of metal handles,

knobs, etc., during normal usage is 55°C. It is

suggested, based on observations of semiconductor

equipment in use, that a continuous handling time of

one minute be used. With this duration, the limit of the

MIL-STD and the MIL-HDBK ranges from 49 to 52°C.

The EN563 burn threshold limit for contact with metal

for one minute is 51°C. The burning heat pain level

listed in the Human Factors Design Handbook is 49°C

(no time frame given; assume high thermal conductivity

material). Thus, the proposed temperature limit appears

to be somewhat high for reasonably foreseeable

extended handling contact with uncoated metal handles,

knobs, etc., and other material with high thermal

conductivity. The Section 18 Table 1 limit is 51°C,

which might be somewhat painful to more sensitive

personnel, but should not result in tissue damage.

R13-6 The proposed hazardous surface temperatures

for extended handling and touching of glass/porcelain

handles, knobs, etc., during normal usage (again

assuming 1 minute) is 65°C. The limit of MIL-STD-

1472D is 59°C for “prolonged contact” with glass. The

EN563 burn threshold limit at 1 minute is 56°C. Thus,

the proposed temperature limit appears to be slightly

high for reasonably foreseeable extended handling

contact with glass/porcelain surfaces of moderate

thermal conductivity. The Section 18 Table 1 limit is

56°C, which is the more conservative of the

recommendations. This limit could be raised based

upon the results of the risk assessment for actual and

foreseeable normal usage.

R13-7 Similarly, the proposed hazardous surface

temperatures for extended handling and touching of

plastic/rubber handles, knobs, etc., during normal usage

(again assuming 1 minute) is 75°C. The limit of MIL-

STD-1472D is 69°C for “prolonged contact” with

plastic. The EN563 burn threshold limit at 1 minute is

60°C. Thus, the proposed temperature limit again

appears to be slightly high for reasonably foreseeable

extended handling contact with plastic/rubber surfaces

of low thermal conductivity. The Section 18 Table 1

limit is 60°C, which is the more conservative of the

recommendations. This limit could be raised based

SEMI S2-0703a

upon the results of the risk assessment for actual and

foreseeable normal usage.

R13-8 The proposed hazardous surface temperatures

for external surfaces and internal parts which may be

touched are 70°C for metal, 80°C for glass/porcelain,

and 95°C for plastic/rubber. It is assumed that this limit

applies to inadvertent touching by the

operator/maintenance person, resulting in the person

instantly breaking contact with the hot surface. There

are no analogs in either the MIL-STD or the MIL-

HDBK for these temperature limits. The EN563 burn

threshold range for one-second contact with uncoated

metal is 65 to 70°C, while the range for one-second

contact with glass is 80 to 86°C. The proposed

temperature limit appears to be slightly high for

reasonably foreseeable inadvertent contact with

external metal surfaces. The Section 18 Table 1 limit

for contact with external metal surfaces is 65°C, which

is the conservative end of the EN563 range.

R13-9 No information was available to support or

refute the temperature limits for contact with external

plastic/rubber surfaces. With regard to internal parts,

the proposed temperature limits may be adequate given

the foreseeable cooling which would likely occur prior

to handling of internal parts. The actual thermal lag of

components likely to be handled could be verified by

thermocouple readings on specific equipment during a

risk assessment.

Table R13-1 Allowable Surface Temperatures (°C)

for Handles, Knobs, Grips, etc., Held for Short

Periods Only (5 seconds or less)

Metal Glass,

Porcelain,

Vitreous

Material

Plastic,

Rubber

EN563 58 70 n/a

MIL-STD-1472 60 68 85

MIL-HDBK-759 60 n/a n/a

Section 18 Table

1 Value

60 70 85

Table R13-2 Allowable Surface Temperatures (°C)

for Handles, Knobs, Grips, etc., Held in Normal Use

Metal Glass,

Porcelain,

Vitreous

Material

Plastic,

Rubber

EN563 51 56 60

MIL-STD-1472 49 59 69

MIL-HDBK-759 52 n/a n/a

Section 18 Table

1 Value

51 56 60

Table R13-3 Allowable Surface Temperatures (°C)

for External Surface of Equipment Which May Be

Momentarily Touched

Metal Glass,

Porcelain,

Vitreous

Material

Plastic,

Rubber

EN563 65-70 80-86 n/a

MIL-STD-1472 n/a n/a n/a

MIL-HDBK-759 n/a n/a n/a

Section 18 Table

1 Value

65 80 95

Table R13-4 Allowable Surface Temperatures (°C)

for Parts, Inside the Equipment, Which May Be

Momentarily Touched

Metal Glass,

Porcelain,

Vitreous

Material

Plastic,

Rubber

EN563 n/a 68 85

MIL-STD-1472 n/a n/a n/a

MIL-HDBK-759 n/a n/a n/a

Section 18 Table

1 Value

65 80 95