How to Operate A Pressure Blast Pot?
If you are new to sandblasting, here is some key information you should know when it comes to operating a Pressurized Blast Pot.
Follow these guidelines to get the best out of your blast pot and maintain it for optimal working performance for decades.
CONNECTION TO THE AIR COMPRESSOR
The sandblasting machine usually has a 1″, 1 ¼”, or 1 ½” air inlet coupling equipped with a ball valve and a pressure regulator and gauge to adjust the pressure at the point of connection with the blaster.
It is important to use a compressor that has an outlet and an air line that is at least the size of your sandblaster’s air inlet or bigger, to avoid causing any restriction to the air coming in. For instance, if your sandblaster has a 1 ¼” air inlet, the air compressor outlet and air line that supplies your equipment must be at least 1 ¼”.
Also, the compressor must be able to supply enough air volume (cfm) at a given pressure (psig) to maintain your sandblast machine pressurized and able to supply enough air for your application. The air consumption at a given blasting pressure is dictated by the opening size of the blasting nozzle.
Consult our Air consumption tables to find out the required cfm for your application.
Remember that, as your blast nozzle wears out, its internal diameter will increase and so will the air demand. For that reason, you should consider the air consumption of a blast nozzle that is one size bigger than the one you are using to avoid lacking air volume eventually.
Ideally, you should use a dedicated compressor for your sandblasting equipment. If you compressor is shared among different air-powered equipment, make sure the use of other equipment will not affect the air supplied to the sandblast pot.
Finally, only straight coupling should be used on both ends of the air hose to ensure the connection is airtight. Avoid using Chicago coupling or other quick connect couplings which may lead to air leaks. For every drop of 1 psig at the nozzle, there is a corresponding loss of 1.5% in productivity.
These considerations are critical in order to supply enough pressure and volume to maintain a constant pressure inside the blast pot. Otherwise, you may experience pressure fluctuation, which will result in an irregular stream of blast media and negatively impact your productivity.
AIR QUALITY SUPPLIED TO THE SANDBLASTER
Air quality is the key. Make sure to use water separators and desiccant filters between the air compressor and the sandblasting machine to remove any oil remains, moisture, and contaminants produced by the compressor, in order to supply only clean and dry air to the blaster.
Moisture can contaminate your abrasive media, which will eventually clog your abrasive metering valve and lead to the formation of rust on your blast pot’s inner walls and piping.
As an additional protection measure, our PPB Series Portable Blasters are equipped with a water separator which uses centrifuge force to extract high concentrations of moisture before it can enter the sandblasting machine.
PRESSURIZING/DEPRESSURIZING THE BLAST POT
Between the air inlet and the pressure pot, an inlet air valve controls the supply of air to the pressure vessel.
The pressure vessel also has an exhaust system equipped with an exhaust air valve enabling it to maintain or release the pressure inside the blast pot.
A plunger mounted on a spring is located inside the pressure pot, which controls the filling of abrasive media inside the blast pot.
When compressed air is supplied inside the pressure vessel, the plunger lifts up to cover the abrasive media filling hole located on top of the blaster. This way, the vessel can build up its pressure until it reaches the desired psig.
When the airflow ceases, the plunger falls back to its initial position, allowing abrasive media to fill up the pot.
To pressurize the vessel, open the air inlet ball valve, open the air valve between the air inlet and the blast pot, and close the exhaust air valve. Make sure the plunger sits tightly on the o-ring and the entire pressure vessel is airtight.
To depressurize the vessel, shut off the air supply to the blast pot and open the exhaust air valve.
Depending on the Choice of Depressurization System, air valves can be operated manually or automatically when the blaster activates the remote-control handle.
The “push line” consists of the air line which collects abrasive media from the abrasive metering valve and propels it at a high velocity through the blast hose and eventually onto the workpiece.
It begins at the air valve which controls the air supply coming through and goes all the way out to the blast nozzle.
ABRASIVE METERING VALVE
The abrasive metering valve controls the flow of abrasive media entering the push line. It is very important to have a precise amount of abrasive material inside the push line – having too much or too little will produce an uneven and unstable media flow which will affect the performance of the sandblasting process.
Abrasive media usually falls by gravity into the push line. The abrasive metering valve consists of an opening that can be set to control the amount of abrasive material entering into the push line.
The pressure of the push line must equal that inside the pressure vessel in order to ensure a normal flow of air and abrasive media towards the blast nozzle. Otherwise, the abrasive metering valve will not be able to correctly control the amount of abrasive media, and an unbalanced pressure may harm your unit.
To increase productivity by reducing manual tasks, most ISTblast Air Valves and Abrasive Metering Valves can be operated from a distance with the remote-control handle – also known as the Deadman Control because upon the release of that handle, most hazardous sandblasting operations are immediately ceased for security reasons.
The Deadman remote control handle is located on the blast hose near the blast nozzle connection. It is available with a choice of electric (12V or 120V) or pneumatic signal.
Blast nozzles are available in several configurations and sizes (interior diameter), all of which produce a different output.
The bigger the interior diameter of the nozzle, the more effective the process will be, but more compressed air pressure and volume are required.
Refer to your instruction manual or contact one of our technical representatives to learn more about how to operate your sandblasting machine safely and efficiently.