Cycle Times for Dry Blast Cleaning

The amount of abrasive blasting required for a specific application depends on the workpiece material, the surface finish requirements, and the performance characteristics of the blast equipment. No dependable formula exists for establishing minimum blasting cycles; the amount of blasting time required to produce a given result in a given machine is established by trial. Table 2 lists abrasives, equipment, and cycles that have been used for dry blasting a number of materials or products for specific purposes.

Table 2 Abrasives, equipment, and cycles used for dry blasting

Material or product

Reason for blasting

Abrasive

Equipment

Type

Horsepower

Nozzle diameter

Blasting cycle

Type

Size No.

mm

in.

Ferrous metals

Cast iron

Prepare for zinc impregnation

Iron grit

G80

Air, table(a)

6

1 4

1 h

Remove molding sand

Steel shot

S230

Wheel, barrel

15

10 min

Cold rolled steel

Remove graphite for painting

Iron grit

G80

Wheel, barrel

15

10 min

Air, table(a)

6

1 4

40 min

Gray iron exhaust manifolds, bearing caps

Clean for machining

Malleable iron shot

S460

Wheel,( b) tumble®

80

1500 pieces/h

Gray iron motor blocks and heads

Remove sand and scale after heat treatment

Steel shot

S460

Wheel, blast cabinet(c)

500

6 s

Hardened steel screws

Remove heat treat scale

Iron grit

G80

Wheel, barrel

10

5 min

Material or product

Reason for blasting

Abrasive

Equipment

Type

Horsepower

Nozzle diameter

Blasting cycle

Type

Size No.

mm

in.

Hot rolled steel

Prepare for painting

Iron grit

G80

Air, table(a)

6

1 4

1 h

Malleable iron castings

Prepare for galvanizing

Steel grit

G50

Wheel, barrel

40

15 min

Pole-line hardware

Prepare for galvanizing

Steel grit

G50

Wheel, barrel

40

15-20 min

Round steel bar

Etch for adhesive coating

Iron grit

G80

Air, blast room

6

1 4

2 min

Soil pipe fittings

Remove molding sand

Steel shot

S330

Wheel, barrel

30

181 kg (400 lb) in 5 min

Steel drums

Prepare for painting

Iron grit

G80

Air, blast room

6

1 4

4 min

Steel rod

Clean for wiredrawing

Steel grit

G40

Wheel, continuous(d)

80

0.2-1.5 m/s (40300 ft/min)

Steel screws

Prepare for plating

Iron grit

G80

Air, barrel(a)

8

5 16

2 min

Structural steel

Prepare for painting

Steel grit

G40

Wheel, continuous(d)

80

0.02 m/s (30 ft/min)

Weldments (steel)

Remove scale, welding flux, and splatter for painting

Steel grit

G25

Wheel, barrel

30

136-272 kg (300-600 lb) in 7 min

Engine parts for rebuilding

Remove paint, scale, and carbon deposits

Glass beads

60-100 mesh

Air

6

1 4

5-20 min

Nonferrous metals

Material or product

Reason for blasting

Abrasive

Equipment

Type

Horsepower

Nozzle diameter

Blasting cycle

Type

Size No.

mm

in.

Aluminum

Produce frosted surface

Sand

50

Air, barrel

ó

1 4

20 min

Prepare for painting

Iron grit

GSO

Wheel, barrel

15

5 min

Bronze

Produce frosted surface

Sand

50

Air, barrel

ó

1 4

20 min

Aluminum and bronze

Prepare and condition surface

Glass beads

20-400

Air

ó

1 4

5-20 min

Nonmetallic materials

Clear plastic parts

Produce frosted surface

Sand

50

Air, barrel

ó

1 4

15 min

Hard rubber

Improve appearance

Sand

50

Air, barrel

ó

1 4

20 min

Molded plastic parts

Remove flash

Walnut shells

Wheel, barrel

10

S min

Phenolic fiber

Produce frosted surface

Sand

50

Air, barrel

ó

1 4

SO min

Prepare for painting

Sand

50

Air, barrel

ó

1 4

20 min

(a) Four air nozzles.

(a) Four air nozzles.

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