Chemical Cleaning of Carbon Steel Piping
- Static cleaning: The static method is useful where only short runs of pipe are concerned and consist merely of filling the pipe, or immersing short sections in a tank, and leaving it to stand for approximately 10 hours.
- Circulation cleaning: The circulation method is employed where long awkward pipe runs are encountered and requires a reservoir, a small circulation pump capable of handling mildly corrosive liquids and some lengths of flexible hosing of suitable diameter. The various piping items are bolted up to form a closed loop and the solution is pumped through the loop and recirculated on the reservoir. This method is much more efficient than the static method due to the constant movement of the solution through the pipes. It also allows several systems, i.e. the lube and seal oil piping from three identical compressors, to be cleaned at the same time.
Chemical Cleaning of Stainless Steel Piping
- Degreasing: If degreasing is thought to be necessary, proceed as described in 220.127.116.11 followed by rinsing with either demineralized or good quality potable water.
- Cold pickling at ambient temperature: In a 200 liter plastic drum, charge 100 l of demineralized (or high quality) water.
- Add the following chemicals and mix thoroughly.
- Nitric acid (HNO3), from a solution of 65% wt concentration, 310 g/l.
- Hydroflouric acid (HFL), from a solution of 40% wt concentration, 37 g/l.
- Charge the solution to the piping as described in 7.10.1. For static cleaning leave to stand for three hours, for circulation, cleaning two hours should be adequate.
- Dump the cleaning solution paying careful attention to 18.104.22.168, effluent disposal.
- Carry out a final rinse, again with demineralized water. Thoroughly drain the piping and air blow dry using instrument air.
- Reassemble piping and carry out oil flushing, etc. as required.