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Coating Industry

Blast-One Weekly Tips
Tip #73
How does the correct hose size make or break your tank project?

17 Ways to Blast a Tank

Keep your productivity up!

Always maximise compressed air volume and pressure. A blast cleaning operation’s productivity level directly depends on the volume and pressure of the air passing through the nozzle. Where production is slow, there’s usually not enough air volume (cfm) and pressure (psi). A larger compressor will provide more air to support a larger nozzle, and a larger nozzle gets the job done faster. But the big question is: "What do you have in between?"

Often when you are blasting on a tank project you will need to use long runs of air hose (bull hose) and blast hose, sometimes as much as 200-300 feet (60-90 metres) or more. It all depends on the accessibility of the site and how close you can get your blasting equipment to the tank.

Obviously every time you increase the distance between the air compressor and the blast pot you are increasing the distance the air has to move through the hose and this increases the pressure loss. Likewise if you increase the distance between the blast pot and the nozzle on the abrasive side you are not only moving air a lot further but also the abrasive. It becomes quite a struggle for the air to propel the abrasive along without it dropping out of the air stream and clogging.

1. Shorter hoses are better

Maintain maximum pressure

Keep your air hose and blast hose lengths as short as possible. This requires that you position your compressor as close to the blast pot as possible to shorten the distance the air has to travel and, as mentioned, it is even more important to keep your blast pot as near to your blasters as you can, to keep the pressure drops along the blast hose to a minimum.

2. Bigger ID hoses are better

Reduce friction and pressure loss

Use a large ID hose size. When it comes to hoses, bigger is always better. Running large ID hoses in your blast system reduces the friction and the pressure loss caused in smaller, more restrictive sizes. Air pressure drops have a large impact on blasting production.

If you have the correct size and length blast hose, you will keep your pressure up and keep your abrasive flowing all the way to the nozzle. This means:

  1. you get better performance
  2. you get the correctly specified profile
  3. the operator can move his nozzle quicker and finish faster
  4. the operator will use less abrasive
  5. less dust will be created.

 

Get the most productivity from your bull air hose

Use a bull hose to supply air to your pot.

Do you use a big nozzle to blast with but only supply the air to your blast pot in a small jack hammer hose? Or maybe you have two jack hammer hoses? This just won’t work. But, we do have good news! Overnight, you can double your blasting rate by simply updating your air supply hose. Big nozzles need big hoses. When you are blasting with a nozzle any larger than a 7/16” (no. 7), you need to supply your air to the pot in a 2 inch (50mm) ID bull hose. Any smaller air delivery hose than this will simply be choking the air supply and decreasing your blasting potential. And then you lose valuable air pressure and you lose money.

IMPORTANT NOTE
Check your hose fittings. It’s no good having a nice big bull hose to supply air to your blast pot if you’ve still got hose fittings or pipe fittings that have a smaller bore than the ID of your hose. A 2” bull hose should be connected to a 2” outlet on the compressor and use 2” bore fittings right through to match. Now the restriction is minimal. And remember - One 2” hose is better than 4 x 1” hoses!

RULE OF THUMB for AIR SUPPLY HOSE:
Minimum size – 4 times the blast nozzle orifice.
Maximum size – no upper limit for air hose.

undersized-air-supply-hose normal-air-supply-hose

 

The blast hose is an integral part of any abrasive blasting system

Correct blast hose sizing is critical for productive and efficient blasting. Improperly sized hoses will have a major effect on your blasting production, abrasive consumption, the surface finish, surface profile and the wear on your blasting equipment. It is very important to size hoses correctly for efficient blasting.

RULE OF THUMB for BLAST HOSE:
Minimum size – 3 times the blast nozzle orifice.
Maximum size – 5 times.

hose-selection-guide

 

Keep hose lengths as short as possible. If extra lengths are required, it is better to run a longer air hose than blast hose, because the pressure loss is significantly lower in air hose.

Fit a large bore flexible whip hose

You need to be a muscle man to continually hang onto some of those large blast hoses all day. By ensuring the blast hose is four times the diameter of the nozzle sure helps keep the pressure up, but it becomes very hard to continually hold. We recommend you fit a 20ft (6m) SupaLife whip hose between your blast hose and nozzle. This special hose is made of high quality rubber to maintain life, but with thinner walls to make it lightweight and flexible. The SupaLife whip hose has a large bore so you don’t lose pressure to the nozzle. Your operator will find it easier to blast, much less tiring on the back and easier to get into tough spots.

Don’t use a smaller size blast hose as a whip hose. - You’ll just choke the system up.

RULE OF THUMB for WHIP HOSE:
The ID of your whip hose should be the same as your blast hose.

air-supply-hose comparative-percentage-reduction-chart

 

 

 

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