Siphon vs. Pressure Pot?
Siphon vs. pressure pot is possibly one of the most misunderstood facts in the blasting industry today. Company product lines often define the definition of this question. Media Blast manufactures all types of abrasive delivery cabinets, wet, dry, siphon, gravity feed and direct pressure. Portable pots and cabinets should be considered separately and the information that follows is critical for proper selection of stationary blasting cabinets only. In addition, abrasive type must be considered.
Compressed air is responsible for the actual part-cleaning rate not abrasive delivery type. Compressed air is needed to deliver the abrasive to the part and the volume of compressed air will establish how much abrasive, in pounds per minute, and the frictional heat generated, in degrees Fahrenheit. More compressed air volume in cubic feet per minute gets you more pounds per minute of abrasive against the part. This increases the frictional heat of the abrasive and produces the almost geometric faster cleaning rate when the air volume is doubled.
FACT: Keeping the compressed air usage and the abrasive velocity measured in miles per hour against the part the same will result in abrasive delivery, pounds per minute, within 10% on the two types of blasting machine delivery systems.
Most abrasive grains can be destroyed with normal air compressor line pressure. Even though a direct pressure machine can actually create a faster abrasive velocity, the siphon type can also produce abrasive velocities that destroy abrasive recycleability rates. Except for steel shot and steel grit, great for direct pressure machines, the siphon type is usually capable of abrasive velocities exceeding the impact velocity of the grain.
Direct pressure machines require pot re-filling that cuts into valuable production time. Not all part processing lends itself to perfect pot reloading schedules. Large part surface areas require long blasting cycles. Long extended blasting cycles require pressure pot reload, reducing production with production down-time.
Time and time again the welding machine comparison has always had the ability to explain and clarify this problem.
Compare the wire feed continuous weld machine to the siphon continuous blast machine then compare the stick or rod welding machine to the direct pressure machine. Each has its pluses but with the rod welder you need to stop about every 6 inches of weld and install a new welding rod. With the direct pressure machine requiring pot refill the comparison is complete. With the wire feed machine you start your welding and don't need to stop until the wire spool is empty. The siphon machine is very similar in that you start blasting and don't need to stop until the abrasive is worn out from maximum recycling. Many options are available to help keep the pressure pot full but remember if direct pressure machines were generally faster, every cost engineer would favor the purchase of automated direct pressure machine types and it's just not so! You always have exceptions to every rule and Media Blast offers the dual pressure pot assembly to permit continuous pot blast but continuous blasting and continuous abrasive feed without media delivery interruption are two separate items that require further explanation.
Call for details and Media Blast will be happy to explain the difference and supply the equipment that is best for YOUR part processing, YOUR production schedule and YOUR compressed air usage when considering siphon and pressure pot machine types.
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