Psi limits on Alloy 20 piping when pumping 98% Sulfuric acid 2

[ctymec1]

I have seen many specs.on the use of Alloy 20 in the pumping of 98% Sulfuric acid but they are all related to temperature.I am looking for some info on psi and what type of valves and fittings can be used.The Sulfuric acid piping,valves and pumps are to be used in the production of drinking water on a RO water treatment plant.

 

[metengr]

Look at ASME B B31.3 Piping Code.

 

[MJCronin]

ctymec...

This is the first time you have specified piping or tubing...right ?

ASME B31.3 is the key......

-MJC

 

[ctymec1]

Thanks for your response MJCronin.Have an Alloy 20 Piping system on site but is no longer in use,we have had many problems with this system in regards to leaks,not on the Alloy 20 piping but on any valve ect.we attach to it.We are about to install a new Sulfuric acid system and the specs.call for the use Alloy 20,so any info I can get will be much appreciated!

ctymec1

 

[ApC2Kp]

ctymec1,

The corrosion problems are multiplied at places the sulfuric acid system is connected to the RO water system.

Where ever the water could back up into the control valve or shutoff valve there will be acid + water, and the most severe corrosion might occur at 60% concentration. The use of Teflon lined piping and valves should be strongly considered at those areas where acid and water mixing might occur. Even if there is a check valve, some back flow will likely take place if a control valve reduces pressure and back flow through the check valve is then possible.

Some of the most frequently replaced valves are the small sample valves. The film of acid left in the sample valve then combines with atmospheric humidity to result in more aggressive moderate 'weak' 40%-70% acid corroding the small sample valves.

 

[QuickFlange]

Hi,

As the concentration goes below the sulphuric acid becomes very corrosive. For high conc.(98.8%) we have used carbon steel storage tanks. CS lined with PTFE is a good option for weak acid. But manufacturing may take some time and also the cost. what about HDPE (I think can be used but no longer life) and also cast iron piping. But what will be the effect of psi?