Max pipe velocity for Caustic Soda & Hypochlorite Acid 2

[drakkkko]

Dear all,

I have to size pumps for both dilute Caustic Soda (5% at 122 °F) and Hypochlorite Acid (32% at 50 °F) fluids.
I know there is recommended velocity for each fluids ( e.g. for NaOH velicity is 6 f/sec )
, but there is a max velocity for each fluid to design pipe diameter ?
What could happens if maximum speed is exceeded in each fluids?

Thanks in advance.

 

[MJCronin]

draggo...

Design fluid velocity for process chemical systems depends on type of fluid, temperature and piping material.

But you don't know what material that you will be using ....

Keep velocity less than 5 fps for most piping materials.

If you exceed max velocity, corrosion rates accelerate

On corrosion prone systems like these, plan on replacing everything every 5 years....Control valve innards more often than that...

MJCronin
Sr. Process Engineer

 

[drakkkko]

Thank you MJCronin !!.

Pipe material we are considering:
Hypochlorite Acid (32% at 50 °F) : CPVC, Sch 80.
Dilute Caustic Soda (5% at 122 °F): Carbon Steel Astm A106 Gr.b, Diam< 3", Sch XS, & Diam>=3" Sch STD.

With respect to caustic soda, it contains virtually no chlorine ... there should be no problem of corrosion related to speed, there are probably other problems that I don't know.

 

[MJCronin]

Use Schedule 80 CS for the caustic soda ..... it only costs a little bit more and will give you slightly more life.

Are you using threaded joints on the CS piping ?

Threaded joints on Schedule 40 CS piping degrades the wall thickness significantly, ..... Sched 80 recommended ...

MJCronin
Sr. Process Engineer

 

[Iomcube]

From my 6 years chloralkali experience if you are using high concentration NaOH at temperatures <80C you can use PP pipes

For 5% you can use CS pipes

For hypo solutions no metallic pipe (except Ti) use only CPVC / PVC