Chapter 5 – Nozzle Neck, Flange, Weld and External Load Assessment
This chapter presents a preliminary engineering assessment of the proposed 10 in nozzle neck,
ASTM A105N Class 150 RF flange, nozzle weld configuration and the external dead load
imposed by the 532 kg suspended submersible pump. This is a screening-level assessment and
is not a substitute for a detailed WRC 537, finite element analysis (FEA), or Engineer-of-Record
design review.
5.1 Design Inputs
Parameter
Nozzle
Nozzle Material
Flange
Outside Projection
Inside Projection
Pump Mass
Shell Thickness
Design Pressure
Design Temperature
Value
10 in NPS Sch.30
API 5L Grade B
ASTM A105N ASME B16.5 Class 150 RF
250 mm
50 mm
532 kg
15 mm
7 barg
+80 °C
5.2 Nozzle Neck Assessment
The nominal Schedule 30 wall thickness is taken as approximately 7.8 mm. A preliminary
pressure-based required thickness of approximately 4.0 mm (including corrosion allowance) was
established in the previous assessment. Therefore:
1.
2.
3.
4.
Actual thickness = 7.8 mm
Required thickness = 4.0 mm
Excess thickness = 3.8 mm
Utilization = 4.0 / 7.8 = 0.51 (51%)
Conclusion: The nozzle neck is preliminarily adequate for pressure loading.
5.3 Flange Assessment
The selected ASTM A105N Class 150 RF flange is suitable for the stated pressure and
temperature envelope provided the pressure-temperature rating is confirmed against ASME
B16.5 and the selected gasket, bolting and facing are compatible with the service.
5.4 Pump Dead Load
The suspended pump load is converted from mass to force:
W=m×g
5. m = 532 kg
6. g = 9.80665 m/s²
7. W = 532 × 9.80665 = 5,217 N ≈ 5.22 kN
5.5 Preliminary Bending Moment
Until the manufacturer's centre-of-gravity drawing is available, a conservative centre of gravity
located 600 mm from the shell/nozzle junction is assumed.
8. Dead load = 5.22 kN
9. Lever arm = 0.60 m
10. Moment = 5.22 × 0.60 = 3.13 kN·m
This bending moment acts simultaneously with the internal pressure loading and should be
included in the local nozzle-shell stress assessment.
5.6 Installation and Dynamic Allowance
During installation, lifting, maintenance and pump start-up, the nozzle may experience transient
loads greater than the static dead load.
Use a dynamic installation factor where appropriate.
Prevent side loading during pump lowering.
Confirm pump guide arrangement does not introduce additional moments.
Review vibration characteristics if the pump operates continuously.
5.7 Nozzle Weld Configuration
Recommended weld arrangement:
Full penetration nozzle-to-shell groove weld.
Continuous reinforcement pad fillet weld (if repad installed).
Qualified WPS/PQR to ASME Section IX.
100% VT and MT/PT of completed welds.
Additional UT/RT as required by the inspection plan.
5.8 Need for Local Stress Analysis
The UG-37 reinforcement calculation demonstrates pressure adequacy only. It does not qualify
the nozzle-shell junction for external forces and moments.
A detailed nozzle-load evaluation should therefore be completed using one of the following:
WRC Bulletin 537 (preferred where applicable).
Finite Element Analysis (FEA).
Recognized pressure-vessel nozzle-load methodology accepted by the Engineer of Record.
5.9 Engineering Recommendations
11. Retain the recommended 10 mm reinforcement pad to improve local stiffness.
12. Verify the pump centre of gravity with the vendor before final design.
13. Minimise nozzle projection where practical to reduce bending moment.
14. Support piping independently so that piping reactions are not transferred to the nozzle.
15. Complete the local stress assessment before issuing construction drawings.
5.10 Chapter Conclusion
The preliminary assessment indicates that the selected 10 in Schedule 30 nozzle neck and Class
150 flange are suitable for the pressure design basis. However, the governing design issue is the
approximately 5.22 kN dead load and the associated bending moment generated by the 532 kg
suspended pump. Final acceptance of the alteration should therefore include a detailed local
nozzle-load analysis in addition to the pressure-boundary checks completed in the previous
chapters.
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