Acid Cleaning (General Guidelines)

Hydro-Logic, Inc. makes no warranty as to the effectiveness of the inhibited acid or services and has no way of knowing the entire metallurgy of the system. Customer assumes the entire risk and agrees to hold Hydro-Logic, Inc. completely harmless from any damage and injury arising from the acid cleaning.

Stage 1 - Pre-Acid Cleaning Preparation

Choose the method of circulation. Install the acid circulating pump and hoses accordingly.

Fill the equipment up with water to flood the entire surface to be cleaned.

If you have a way to heat up the water to about 140°F, do so. This will enhance the acid reaction with lime. The additional heat will also aid in the circulation.

Stage 2 - Acid Cleaning

Calculate the water capacity of the system.

Pump 5% - 10% of this capacity in acid. If the system holds 1000 gallons of water, add 50 - 100 gallons of acid. pH of the initial solution should be around 1.0.

Remember the old chemistry rule: Add acid into water (not water into acid). The latter will cause a violent reaction and can result in injury.

Start the acid circulation pump to circulate the acid solution through the equipment.

Check pH immediately. pH must start at about 1.0. If pH is higher, pump additional acid into the equipment until pH drops to about 1.0.

Check pH every hour. As pH increases to about 2.0, add additional acid to drop the pH back to 1.0.

Once pH stabilizes at about 1.5 for 2 hours, it indicates that no additional scale is being removed. As such, it usually indicates that the removal of the scale is completed.

Depending on the quantity of scale to be removed, acid cleaning time can take up to 24 hours. Typically, circulation of 8 - 12 hours is sufficient.

When the equipment is cleaned sufficiently, stop the acid circulation pump.

Dispose, Neutralize, or Treat the acid solution, as discussed in the Acid Cleaning Hazards - Proper Planning and Preparation Guidelines.

To neutralize, you may do this while the acid is in the equipment so you don’t have to use another tank. You will form sludge in the equipment but they can be flushed out by pressure washing. Add caustic slowly to raise the pH to the desired level.

Drain the treated acid solution out of the equipment.

Stage 3 - Post Acid Cleaning Guidelines

Flush the equipment thoroughly with fresh water. Continue flushing until all the loose particles are flushed out. Pressure washing will help.

Inspect the internal to see if the scale removal is sufficient. Inspect for any damage too, so repairs can be made before placing the equipment back in service.

Remove all caps. You may need to physically clean these capped nipples, as these areas have a tendency to collect particles during the acid cleaning process, due to poor circulation.

Install all the piping that were removed during Stage 1.

Start-up or pressure test the equipment for leaks.

Immediately refill the equipment with treated water to prevent flash corrosion and possible residual acid in crevices. Final pH must not be acidic.