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1800 882 229

Specialist suppliers to
the Blast Cleaning &
Coating Industry

Blast-One Weekly Tips
Tip #70
Is moist air costing you time and money?

17 Ways to Blast a Tank

On many tank jobs we find customers need to leave a newly blasted surface unpainted overnight or over a weekend. If there is any moisture in the air a flash rust will spoil the ready blasted surface making it unpaintable.

Blasted Surface A newly blasted surface
ready for painting...
Development of rust ...will quickly develop flash rust
with moisture present in the air

By using a dehumidifier on your tank project you are able to blast all day and hold the blast that night or longer to save you having to:
1) Clean up the spent abrasive
2) Rush the paint job and then clean the equipment
3) Put a holding primer on the surface.

dehumidifier-diagram

It's possible to hold the blasted condition of the steel for days, when the containment and dehumidification are correctly monitored and controlled.

This is convenient as it means, once you start blasting, you can stop and start as you like without worrying about losing the blast to flash rusting and forfeiting the hours of work and materials already spent.

It makes it so much easier. You don’t have to stop every day to clean up the abrasive, set your airless pump up, spray on the coating and clean the equipment before you go. It also saves you having to be careful when blasting up against the pre-primed surface of the previous section when you start to blast again.

dehumidifier

You are in control and you can plan and execute your process timing to ensure quality.

Blast as long as you want and continue the next day without having to go back and re-blasting what you have completed on previous shifts for fear of the surface being contaminated with rust.

This is what you can achieve by using a dehumidifier to control humidity.

There are a couple of simple rules of thumb: To maintain correct conditions in the tank you will need to have four air changes of dehumidified air per hour in the tank. Let's look at an example: If you’ve got a tank that is 60,000 cubic feet, you will need to use a 4,000 cfm dehumidifier.

Reduce the water content in the air with a Dehumidifier

Dehumidification is not about just heating the air or reducing the relative humidity (also known as the ‘RH’). If you simply heat, the lower RH will enable the air to hold more water before saturation, ie. no water is actually removed. Dehumidification effectively reduces the actual water content in the air by removing it.

Surface Preparation

During Abrasive Blasting and immediately after, the RH is a critical factor, as the substrate surface becomes vulnerable to corrosion such as flash rusting. The electrolyte in atmospheric corrosion is usually the water in the air. Introducing Dehumidified Air into an enclosed work area will reduce the RH significantly. If the humidity is reduced to below 50% RH, you can effectively ‘hold the blast’ on uncoated, blasted steel for days – sometimes weeks! This will have a huge impact on a production cycle – imagine being able to blast non-stop for a week before having to stop, clean up and paint!

Drying

Dehumidifiers can be used in the construction industry to save time and money. The curing of concrete floors and walls prior to painting etc can be drastically reduced. Bad wet weather conditions need not affect your painting schedule for indoor or undercover work as dehumidified air also reduces drying time of paint. Another good advantage is the optional precooler which also lowers surface temperatures assisting the curing process of the applied coating. The precooler is a fatigue management tool for those working in the area maintaining workable conditions.

Preservation

A dehumidifier can be effectively used near equipment such as boilers during maintenance. Vulnerable to corrosion, such pieces of equipment can be protected by dry air during any scheduled maintenance process.

Power it with Propane

If you choose to operate the dehumidifier’s heaters on Propane instead of electricity, your costs can be reduced by thousands of dollars per month! The motors and controls are still electrically operated, but the bulk of the energy required to operate the Dehumidifier is consumed by the heaters. Ask your Blast-One dealer for more information.

dehumidifier-diagram

Click here to view the Psychrometric Chart.

Call Blast-One now on 1800 882 229 for further help on calculating your dehumidifier needs.

Dehumidifier Rental

Dehumidifiers are Available for Rent

Sizes Available: 200 cfm to 20,000 cfm of variable style and temperature control.

Benefits of Rentals

  1. Short term back up equipment
  2. No maintenance required
  3. Use and return this unit
  4. Claim as a tax free expense
  5. Don't have to store the unit
  6. No worries about repairs cost or depreciation
  7. Availability of a large range of equipment
  8. Access to equipment you can't afford
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