Calculation of pump casing thickness

⚙️ Calculation of Pump Casing Thickness

Pump casing thickness is a critical design parameter that ensures the pump can safely withstand internal pressures during operation. The casing acts as the pressure boundary, protecting both the pump internals and the external environment. Accurate calculation of casing thickness is essential for safety, reliability, and compliance with engineering standards.  

📏 Formula for Pump Casing Thickness

The casing thickness can be calculated using the following equation:  

T = p x r / (S – 0.6p)  + 3  

Where:  

- T = Thickness of pump casing (mm)  

- p = Maximum working pressure (bar)  

- r = Internal radius of the casing (mm)  

- S = Permissible stress of the material (N/mm²)  

🔍 Determination of Permissible Stress (S)

Permissible stress is derived from the material’s ultimate tensile strength (UTS):  

S = 1/4 * UTS * 0.8  

- UTS = Ultimate tensile strength of the casing material.  

- The factor of ¼ and 0.8 ensures a safety margin, accounting for material imperfections, fatigue, and operational uncertainties.  

⚡ Explanation of Formula Terms

1. Pressure Term (p × r):  

   - Represents the hoop stress generated by internal pressure acting on the casing radius.  

2. Denominator (S – 0.6p):  

   - Accounts for material strength reduced by the effect of pressure.  

   - Ensures casing thickness is sufficient to resist bursting under load.  

3. Constant (+3):  

   - A design allowance added to cover machining tolerances, corrosion allowance, and safety margins.  

📉 Practical Example

Suppose:  

- Maximum working pressure (p) = 10 bar  

- Internal radius (r) = 150 mm  

- Ultimate tensile strength (UTS) = 400 N/mm²  

Step 1: Calculate permissible stress (S):  

S = 1/4 * 400 * 0.8 = 80 N/mm²

Step 2: Calculate casing thickness (T):  

T = {10 * 150}/{80 - (0.6 * 10)} + 3 = 23.3mm

So, the required pump casing thickness is approximately 23.3 mm.  

✅ Conclusion

The calculation of pump casing thickness ensures that the pump can safely handle maximum operating pressures without failure. By considering internal pressure, casing radius, material strength, and safety allowances, engineers can design casings that are both safe and efficient. Proper casing thickness not only prevents catastrophic failures but also extends pump life and reduces maintenance costs.