Siphon blast cabinets and pressure blast cabinets are the two main types of sand blasting cabinets that exist on the market. The two have some distinct differences in how they operate.
A siphon blast cabinet (aka a suction blast cabinet) is mostly used for light production jobs, and general cleaning of parts and objects. A siphon blaster works by using a suction gun to pull blast media through a hose, and deliver that media to a blast nozzle, where it is then propelled at great speed into the cabinet. Siphon blast equipment is easier to set up, but it takes more blasting pressure to achieve maximum abrasive impact. Because of this, suction blast cabinets will leave a less pronounced anchor pattern than a direct pressure cabinet using the same blast media.
A pressure blast cabinet uses a pressurized vessel (like a pressure pot) filled with blast media, which is then forced through a blast nozzle. Pressure blasting is significantly faster and more aggressive than suction blasting.
What are some Pros of Siphon Blast Cabinets?
Lower initial cost. To set up a suction blast cabinet you need less equipment than with a direct pressure system. If budget is a concern, a siphon blast cabinet may be a better choice than a direct pressure cabinet.
Suction blasting uses less compressed air. A pressure blast cabinet uses more air than a siphon blast cabinet with the same size blast nozzle. You can see the comparisons of air blast consumption between siphon blast and direct pressure here.
Ongoing operating costs are lower. Because direct pressure blasting throws with more force, the erosion of your blast nozzle, glass panels, and other replacement parts is faster than with a siphon blaster. Direct pressure blast cabinets are more aggressive, and will therefore eat up the blasting surfaces more quickly than a siphon blast cabinet.
Cons of Siphon Blast Cabinets
Slower cleaning speed than direct pressure. Suction blast cabinets operate with lower air pressure than direct pressure. They simply cannot strip and clean as fast as a pressure blast cabinet. For heavy-use industrial blasting applications, a direct pressure cabinet may be a better choice.
Cannot push heavy steel shot or grit. Direct pressure units use a pressure pot to propel abrasive blast media. Because direct pressure cabinets can use more force, they can use steel shot or grit for blasting jobs.
Slower cleaning and stripping than pressure blasting. In a suction blast cabinet, the blast media pushes at a lighter pressure and speed. Direct pressure cabinets are about 3 to 4 times faster at blasting residue and coatings from objects than traditional siphon blast cabinets.
More difficult to strip heavy residue or coatings from a surface. Siphon blast cabinets are less aggressive than pressure blast cabinets. Heavy deposits may be more difficult to remove from a surface in a suction blast cabinet.
What are some Pros of Direct Pressure Blast Cabinets?
Increased productivity. Generally, you will be able to clean surfaces about 3 to 4 times faster using direct pressure as opposed to siphon blasting.
More aggressive force than siphon / suction blasting. Pressure blast cabinets deliver abrasive media at about twice the speed of siphon blasting cabinets. Heavy, caked-on residue is much easier to strip with a direct pressure blaster.
You can blast with heavier media. Metallic blast media, like shot or steel grit is not easily done in a traditional suction blast cabinet. Direct pressure cabinets mix the air and blast media in a pressurized pot, and expel the abrasive into the cabinet. With a siphon blast cabinet, this is not easily done, as the media must fight gravity, and be drawn up through the blast hose. For shot blasting, a direct pressure cabinet is the equipment you should use.
Some Cons of Direct Pressure Blast Cabinets
Initial setup expense is greater. Direct pressure cabinets require a few extra components than suction blast cabinets. Because the setup requirements are a bit more complicated, it takes a larger investment to get started with a direct pressure cabinet.
Parts and components wear out faster due to wear and tear. Because a direct pressure cabinet propels the blast media with greater force, universally, the blast machine components tend to wear out at a faster rate than with a suction blast cabinet.
Needs more air to operate. When abrasive blasting with more force, the consumption of pressurized air increases. It takes more air to operate a pressure cabinet than a siphon blast cabinet.
Air Consumption: Siphon Blast vs Direct Pressure
|Siphon Blast Cabinet CFM Consumption|
|Nozzle Size||Air Nozzle Orifice||30 PSI||40 PSI||50 PSI||60 PSI||70 PSI||80 PSI||90 PSI||100 PSI||120 PSI|
|1/4″ (#4), 5/16” (#5)||1/8”||9.8||12.03||14.26||16.39||18.62||20.76||22.99||25||30|
|5/16” (#5), 3/8” (#6)||5/32”||15.31||18.8||22.28||25.61||29.09||32.43||35.92||40||49|
|Direct Pressure Blasting CFM Consumption|
|Nozzle Size||Nozzle Size (Decimal)||20 PSI||30 PSI||40 PSI||50 PSI||60 PSI||70 PSI||80 PSI||90 PSI||100 PSI|