Guidance for tank level control of 98% sulphuric acid

[chris1967]

We are considering altering calibration of existing level control of a 98% sulphuric acid storage tank and require guidance as to legislative requirements. Would it be acceptable to calibrate to the full tank capacity or do you restrict to a percentage of maximum capacity.

 

[BRT549]

All concentrations of sulfuric acid are not considered PSM chemicals (Process Safety Management). Therefore, there is no web of regulations and standards - if you want to respan your level sensor there should be no problem from that aspect.

If your tank has an overflow, a suggestion would be to call the bottom of the overflow pipe the 100% point.

 

[JOM]

chris,

isn't there something wrong in principle in having a situation where a process parameter can go beyond the capability of the instrument to measure it - ie, goes offscale? Cheers,
John.

 

[hacksaw]

Place your 100% at least 6" (150 mm) below the bottom of the overflow.

You want to have a little time between any alarms and actual overflow. Cheap insurance.

Believe the Chemical Manufacturers Assoc. may have requirements listed for sulfuric.

 

[PeterPiper]

The NSAA (National Sulphuric Acid Association) provide some basic guidence on storage of conc H2S04. From a level point of view you can calibrate the instrumant as you like but froman operational point of view they do have suggested maximum operating levels below the overflow and vent lines.

If you want a copy contact;
Ms.P Latham
19 Newgate Street
Chester
CH1 1DG
+44 (0)1244 322200

The section on level indication is summerised below.

1. Contents gauge should be read directly in Tes and visible at the intake point.
2. An independent high level trip should be provided that stops the flow before the overflow.
3. If the gauge reads in litres or % full, maximum fill level should be clearly indicated.
4. Use of sightglass' is to be discouraged and only acceptable if protected from mechanical damage and can be isolated in the even of damage.
5. If the contents gauge is not visible to the offloading driver the customer must provide offloading procedures detailing safe systems of work covering instructions, training and supervision actions to prevent tank overflow.
6. If there is no indication of level on the tank and contents is measured by ‘dipping’ then written confirmation that there is space available in the tank must be supplied to the driver before off loading will commence. This may also be required when placing an order.

PeteRJ