Premium Part 2 - Intermediate Shell and Tube Heat Exchangers

We have come a long way.

We have understood the basics of Shell and Tube Heat Exchanger and we have started on the calculation part.

1. Calculating the thickness of the Shell.

2. Calculating the thickness of the Channel Head.

Now we are going to calculate the thickness of the Tube based on Design Pressure.

API 660 Table 1 has given us a guide on the minimum thickness of the Tube based on the material of the Tube.

According to the material table, tube side is SA387-11 Cl2, its a type of low-alloy steel. Therefore our minimum thickness according to API 660 is 2.11mm.

The tube that is used is sized as ¾” OD (19.05mm) with wall thickness as 2.108mm

Now lets calculate the minimum thickness based on design pressure.

The formula - as per ASME VIII, div 1, UG-27

Where

Pdt - Internal Design Pressure - 43 barg - 4.3 MPa

rt - inside radius of tube - OD-19.05mm, thickness-2.11mm, rt - 7.415mm

C - corrosion allowance - 0mm

S - allowable stress - check ASME II Section D - SA387-11 Cl2 @ 350 deg C Design Temp - 148MPa

E - Joint efficiency, refer UW-12 equals 1

Plug it in the formula -

Tmin = 0.219 mm

Therefore, required thickness based on Design Pressure of 43 barg is 0.219mm.

To summarize, the thickness required as per design pressure is much lower than the selected tube thickness (2.108mm)

That is it for today, the example given is sufficient for you to understand how to calculate tube thickness. If personal mentoring (on the calculations) and mentorship is something that you are looking for, upgrade here.