Hydrotest Pressure of Newly procured tubes

[franklin55]

We are planning to re-tube one of our condensers. The tubes OD is 25 mm and thickness is 2.2 mm with material ASTM A179. Please advice what hydrotest pressure should we specify for the preshipment HYDROTEST.

 

[rmw]

Ask your tubing vendor what their standard hydro test pressure is. Then decide if that is suitable for you.

rmw

 

[franklin55]

Thank you very much for replying.
The design pressure in this case is 8.4 Kg/cm2. So the test pressure for tubes should be 8.4 x 1.3 = 10.9 Kg/cm2. But when I dug out the ASTM standard A540 (Specification for general requirements for carbon steel tube), it mentioned the hydrostatic test pressure by following:
22. Hydrostatic Test
22.1 Except as provided in 22.2 and 22.3, each tube
shall be tested by the manufacturer to a minimum hydro-
static test pressure determined by the following equation;
Inch-Pound Units: P = 32000 l/D (3)
Si Units: P = 220.6 t/D
where:
P = hydrostatic test pressure, psi or MPa,
t = specified wall thickness, in. or mm, and
D = specified outside diameter, in. or mm.

According to this standard this comes out to be:
P = 220.6 x 2.2 / 25.4 = 19.1 MPa (190 Kg/cm2 !!!!!!!)

Please note that this standard is also applicable to A179 tubes
I am surprised that on th e basis of design pressure of the equipment, the test pressure should be 10.9 Kg.cm2 but the code has specified it as 190 Kg/cm2!!!!!! how is so much difference???

 

[rmw]

You are confusing the test pressure requirements of a specific piece of equipment with the testing after the manufacturing process of tubing which can be used for a variety of purposes. The manufacturer who makes this tubing doesn't know (or care) whether that tubing is going into your low pressure condenser application or someone else's HP boiler or heat exchanger application. They just test to the requirement of the applicable code to which the tubing is manufactured. When a mill runs your size tubing, they run a whole lot more than what will be required for your retubing job (based on details given in another thread.) So the same tubing could easily wind up being used in a variety of actual operating pressures.

Or NOT!!! Sometimes they will cut corners or make assumptions which is why I recommended asking them to what pressure do they hydrotest. That will answer two questions; (1) whether or not they do in fact hydrotest, and (2) if they do, to what pressure.

rmw