Graco ti25442a Metering Valve Settings, Grit Size, Blast Pressure, Abrasive Dose, Blast Angle

Operation

Metering Valve Settings

There is no fixed formula for what works best in each application. The information below works best for the majority of the time. From this initial setting, adjustments can be made up or down to get the fastest removal rates without damage to the surface.

Normal settings are: 110 psi (7.5 Bar, 0.75 MPa) initial pot setting, less than 1/2 turn open metering valve, blasting pressure at 80 psi (5.5 Bar, 0.55 MPa). For applications requiring higher performance, use high-performance abrasive (the heaviest mass @ 80 grit) such as Garnet, and the highest pressures the compressor can support. The initial pot pressure should always be 30 psi (2.0 Bar, 0.2 MPa) above the intended blast pressure.

Gradually make adjustments to meet the specific requirements for each application. Higher blast pressures will require turning the abrasive metering valve slightly more open (and vice versa). Make the adjustments (see DataTrak Controls, page 7 ) to achieve 7-10 cycles per minute to be the most efficient (cut at the fastest rate while using the least amount of abrasive). Blasting pressures can range between 30 - 120 psi max (2.0 Bar, 0.2 MPa – 8.2 Bar, 0.82 MPa).

Unlike conventional sandblasting, higher pressures do not necessarily mean better cleaning. Nozzle distance and the angle to the surface has an effect on performance, as does the blast pressure. Choice of abrasive also has a great effect. High-performance abrasive produces the best performance and can save enough time to make up the difference in cost.

NOTE: Blasting with 150+ feet of blast hose requires the use of an electric blast control.

	Grit Size	Blast Pressure	Abrasive Dose	Blast Angle	Notes
General	40/70	60-80 psi (4.1 Bar,	1/4 to 1/2 turns	35° - 65°	When the blast
		0.41 MPa- 5.5 Bar,			pressure is
		0.55 MPa)			increased, the
					abrasive dose turns
					will also need to be
					increased.
Wood	80 (using a low	40-50 psi (2.7 Bar,	1/8 to 1/4 turns	15° - 30°	Do not wash, as it
	mass abrasive	0.27 MPa- 3.4 Bar,			may raise the wood
	like glass)	0.34 MPa)			grain. Brush off
					excess abrasive after
					the wood dries.
Steel	80-100 (using	100-120 psi (6.8 Bar,	1/4 – 1/2 turns	65° - 85˚	When the blast
	a high-mass	0.68 MPa- 8.2 Bar,			pressure is
	abrasive like	0.82 MPa)			increased, the
	Garnet)				abrasive dose turns
					will also need to be
					increased.
Fiberglass	40-70 low mass	45-65 psi (3.1 Bar,	1/8 to 1/4 turns	35° - 45˚	When the blast
		0.31 MPa- 4.4 Bar,			pressure is
		0.44 MPa)			increased, the
					abrasive dose turns
					will also need to be
					increased.

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