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SEMI F78-0304 © SEMI 2003, 2004 9 Tube Size Wall Thickness Minimum ID Purge Rate ID Purge Pressure Restrictor Size 38 to 64 mmwc ½ in. 12 mm 0.049 in. 1 mm 15 scfh 7 l/m 1.9 to 2.8 torr 1.0 to 1.5 iwc 25 to 38 mmwc ¼ in.…

SEMI F78-0304 © SEMI 2003, 2004 8

12.8.5 Field Installation

12.8.5.1 If a system cut-out or cut-in is required, purge

shall be applied to both ends or the down stream end

must be discarded or cleaned, per Section 12.5. The

following cutout procedure shall be followed:

12.8.5.1.1 Set purge pressures to 5 psi max (35 kPa)

for safety.

12.8.5.1.2 Make initial cut. WARNING

: When the

tube is cut purge gas will escape the cut area at high

velocity. This gas may contain particles from the cut or

the tubing. Protect yourself, others, and nearby

equipment from injury or damage (Figure 8).

12.8.5.1.3 Make any additional cuts.

12.8.5.1.4 Face the ends.

12.8.5.1.5 Set single purge direction for welding.

12.8.5.1.6 All cuts shall be done in the horizontal when

possible.

13 Interpretation of Results: Weld Inspection

13.1 All welds shall be 100% inspected on the outside

surface and whenever possible on the ID surface to

insure conformance to the weld bead specifications

listed in SEMI F81.

13.2 Dimensional and Configuration Inspection —

Dimensional and configuration inspection shall be

performed as follows:

13.2.1 One hundred percent subassemblies shall be

inspected. If a subassembly is opened for inspection,

the inspection must be performed in a clean room of

same class as the assembly area.

13.2.2 Confirm fabrication drawing is attached to the

assembly; if not, reject.

13.2.3 Use check sheet to verify conformance of

assembly to drawing. Check dimensions, squareness,

offsets, straight edges, and levels to verify all

dimensions.

13.2.4 Inspect each weld externally in reference to the

coupon.

13.2.5 When subassemblies have passed inspection,

they shall be tagged as such, rebagged, and released for

final testing.

13.3 Any items found defective during inspection and

repairable may be repaired, if the repair will not

degrade the system conformance to installation

specifications.

13.4 Where a weld is found defective, the preceding

two welds shall be tested as indicated in Section 11. If

either of these welds is rejectable per SEMI F81, then

all welds made since the last welding procedure was

established shall be removed and replaced.

14 Report

14.1 Coupons shall be logged with the date and time

and operator identification. Coupons and coupon logs

shall be retained for one year. Sample test welds shall

be kept on file and may be reviewed at any time during

the construction.

14.2 A daily log shall be maintained on all system

welds and coupons (see Weld and Coupon Log, Table

2), and as-built drawings recording all data shall be

maintained in the welding area.

14.3 All welds shall be identified with a code number

and cross-referenced with the drawings for future

evaluation.

15 Related Documents

AWS C5.10 — Recommended Practices for Shielding

Gases for Welding and Plasma Arc Cutting

ANSI/AWS C5.5 — Recommended Practices for

GTAW

Table 1 Suggested ID Purge Setting for Argon and Argon Gas Mixes

Tube

Size

Wall

Thickness

Minimum

ID Purge Rate

ID Purge

Pressure

Restrictor

Size

1/16 in.

n/a

0.015 in.

n/a

3 scfh

1.5 l/m

13 to 16.8 torr

7 to 9 iwc

175 to 230 mmwc

n/a

1/8 in

3 mm.

0.028 in.

0.8 mm

5 scfh

2.3 l/m

9.3 to 16.8 torr

5 to 9 iwc

130 to 230 mmwc

1/16 in.

¼ in.

6 mm

0.035 in.

1 mm

7 scfh

2.5 l/m

5.2 to 6.3 torr

2.8 to 3.4 iwc

71 to 86 mmwc

1/8 in.

3/8 in.

10 mm

0.035 in.

1 mm

7 scfh

2.5 l/m

2.8 to 4.7 torr

1.5 to 2.5 iwc

1/8 in.

SEMI F78-0304 © SEMI 2003, 2004 9

Tube

Size

Wall

Thickness

Minimum

ID Purge Rate

ID Purge

Pressure

Restrictor

Size

38 to 64 mmwc

½ in.

12 mm

0.049 in.

1 mm

15 scfh

7 l/m

1.9 to 2.8 torr

1.0 to 1.5 iwc

25 to 38 mmwc

¼ in.

6mm

¾ in.

20 mm

0.065 in.

1.5 mm

20 scfh

10 l/m

1 to 2 torr

0.5 to 1.1 iwc

13 to 28 mmwc

¼ in.

6 mm

1 in.

25 mm

0.065 in.

1.5 mm

40 scfh

20 l/m

1 to 1.9 torr

0.5 to 1.0 iwc

13 to 25 mmwc

¼ in.

6 mm

1 ½ in.

38 mm

0.065 in.

1.5 mm

80 scfh

40 l/m

1 to 1.3 torr

0.5 to 0.7 iwc

13 to 18 mmwc

¼ in.

6 mm

2 in.

50 mm

0.065 in.

1.5 mm

150 scfh

70 l/m

0.7 to 1.3 torr

0.4 to 0.7 iwc

13 to 18 mmwc

3/8 in.

10 mm

3 in.

75 mm

0.065 in.

1.5 mm

320 scfh

150 l/m

0.4 to 0.9 torr

0.2 to 0.5 iwc

5 to 13 mmwc

½ in.

12 mm

4 in.

100 mm

0.083 in.

2 mm

600 scfh

275 l/m

0.4 to 0.7 torr

0.2 to 0.4 iwc

5 to 13 mmwc

¾ in.

20 mm

6 in.

150 mm

0.083 in.

2 mm

1000 scfh

475 l/m

0.2 to 0.9 torr

0.2 to 0.5 iwc

5 to 13 mmwc

¾ in.

20 mm

NOTE 1: scfh—standard cubic feet per hour. L/m—liters per minute. iwc—inches of water column. mmwc—millimeters of water column.

NOTE 2: This table is for use on butt welds only.

NOTE 3: Internal pressure shall be adjusted for ID convexity of 0 to +10% of the wall thickness at the 6 o’clock position (bottom of the weld).

NOTE 4: ID purge rates shall be adjusted to the desired ID color line.

NOTE 5: Restrictor sizes are approximate. Purge rate and pressure are critical parameters.

Table 2 Weld Log or Weld Coupon Log

Customer: Date Begun:

Location: Page __ of __

Project: Welder:

Number Size Description ID Purge

Flow/pressure

Visual Color Uniformity Heat/Lot Coupon Date Comments QA

egin Production

Welding

Verify correct welding power

supply and weld head, collets,

electrodes, etc.

Yes

Is equipment

working properly?

Yes

Set up procedure to deal

with hazard. Reference

SEMI Standards.

Yes

Fix it, call technician,

or return to factory.

Are there any hazardous

materials or operations?

Do all materials conform to

specifications? Tubing, fittings,

cleaned and faced? Electrode

urit

e set-u

Get proper materials

and material specs.

Submit test welds for

testing. Document results

and record all variables

on proper forms.

Has Weld Procedure Been Qualified?

Are Welders Certified?

Make Qualification Test

welds for WPS, PQR,

R Per Section 7.

Yes

Make Sample Test Welds using

cleaned and faced coupons of

same alloy, material heat and

dimensions to be welded.

Examine Sample Welds on OD for weld

bead appearance, joint contamination,

Joint soundness, surface oxidation,

discoloration, pitting, cracking, defects

of fit-up and workmanship.

Section coupons and inspect ID surface

visually for penetration, bead concavity,

ead variation, and oxidation.

Is weld acceptable?

Determine

and fix cause

of problem

First sample weld is onsite

work sample. Document all

variables. Identify and save

all coupons.

Enter

required

information

in coupon

log.

Verify correct

OD, ID purge

flowrates and

ID pressure.

At start or end

of shift or after

a change in

procedure. See

Section 11.

Weld Inspection

100% Visual of OD

surface of all welds.

ID inspection of all

accessible welds;

cut-out statistically

significant sample

for inspection.

Repair or cut out previous

welds

er Sectio

13.4.

Is weld acceptable?

Maintain Weld

Log for all welds

Yes

Figure 2

Welding Procedure Flow Chart