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Start | Basics Blasting Technology



7.6 Selection of a blasting pot in considering the wear and tear behaviour


1) Assumption Nozzle: 8 mm Ø
    Abrasive: slag, specific weight 1.5
    Blasting pressure: 8 b

2) to determine based on nozzle table: abrasive capacity = 465 kg/h
    (see chapter 9)

3) desired blasting time: e.g. 5 min.
    optimal pot size = 465 * 5/60 = 39 kg of abrasive

4) optimal pot size at a blasting time of 5 min. = 39/1.5 = 26 l volume
    optimal pot size at a blasting time of 10 min. = 52 l volume
    optimal pot size at a blasting time of 20 min. = 104 l volume
    optimal pot size at a blasting time of 40 min. = 208 l volume


Wear and tear behaviour:
Wear and tear at vessel and emergency shut-down will be kept at low level by an optimal selection of the pot size according to the demands of the blasting unit.

The application of an air/sand-control is another opportunity to minimize wear and tear. Before the blasting operator switches off the pot switching over to air operation takes place and the blasting hoses are run empty. The subsequent switching off without abrasive reduces considerably wear and tear at the dosing valve and emergency shut-down.


7.7 Increased wear and tear at the blasting pot caused by wrong adjustment

Commissioning of a blasting pot is shown as an example here.

Commissioning of a blasting pot

Click to enlarge!



A blasting pot with pressure conditions as shown in this picture does not function because there is lower pressure at the dosing valve (p3) than at dosing valve (p4). By this, the abrasive can flow through the dosing valve out of the blasting pot; only compressed air flows out of the jet nozzle.
The pressure p4 will be reduced only by slight closing of the lateral ball valve. If p4 will reach the value of p3 (or less) the abrasive will start flowing through the dosing valve and the blasting pot is operational.

Too hard closing of the ball valve leads to the fact that too much abrasive flows through the dosing valve at a very high speed (pressure p4 is much lower than pressure p3). This leads to extraordinary high wear and tear at the dosing valve. If the flow volume will be additionally reduced at the dosing valve, i.e. the flow volume cross-section reduces, the dosing valve acts like a nozzle. By this life time of the dosing valve as well of the components getting in contact with the abrasive will reduce many times over.