At the pipe-stress check, the suction nozzle is 600 mm and the discharge nozzle is 500 mm, while the available API 610 table stops at 16 in. Do not assign either nozzle a generic allowable load or extrapolate the 16-in values; obtain the allowable nozzle loads for the exact pump from its manufacturer and compare your calculated loads with those limits.
Check whether the pump table covers these nozzles
Read the largest nozzle size covered by the API 610 data you have. In this case it is 16 in; both stated metric nozzle sizes are larger. That is a coverage limit, not a load value for a larger nozzle. A value for a 16-in nozzle does not automatically apply to either nozzle here.
- Record the suction and discharge nozzle sizes as shown on the pump drawing: 600 mm and 500 mm.
- Mark the limit of the table you have: 16 in.
- Stop the table-based check at that boundary. Do not scale, interpolate, or extrapolate loads without an applicable manufacturer method.
A nozzle's allowable external load depends on the pump construction and support arrangement. The information provided specifically identifies mounting style as a factor: a centreline-mounted pump, an end-suction foot-mounted pump, and a foot-mounted horizontal split-case pump can have different load capacity. The nozzle size alone cannot select an allowable.
Identify the exact pump and mounting arrangement
Read the pump data sheet and general arrangement drawing before changing the stress model. Confirm the pump type, mounting style, casing material, nozzle locations, and the flange-to-pump-centreline or mounting-feet dimension. These details determine whether a published chart applies and are also needed for an approximate calculation if the manufacturer cannot supply limits.
- If the pump is centreline mounted, use limits for that mounting configuration.
- If it is an end-suction foot-mounted pump, do not use limits for a different pump construction.
- If it is a foot-mounted horizontal split-case pump, request limits for that specific arrangement rather than assuming another type is equivalent.
If the drawing does not make the mounting arrangement clear, resolve that with the manufacturer before accepting a nozzle-load calculation. A chart for the wrong configuration can make a numerically low load appear acceptable when it is not.
Request allowable loads for each nozzle
Ask the pump vendor for the allowable external force and moment data for the exact pump, including both the 600 mm suction nozzle and the 500 mm discharge nozzle. Request the applicable chart or calculation basis, its units, the coordinate convention, and any load-combination restrictions. Confirm whether the values apply to the supplied pump and its actual mounting arrangement.
Do not accept “normal allowable loads” as a substitute for identified limits. There is no useful generic value established here for either nozzle size. If the vendor has not yet provided the data, keep the pipe-stress case open rather than treating the largest API table entry as a provisional acceptance value.
The vendor data is the preferred input because the allowable is specific to the pump. If the vendor cannot provide a chart, ask for an engineering assessment using pump-specific information. The source data identifies casing material and the dimension from the flange to the pump centreline or mounting feet as inputs needed for an approximate force-and-moment calculation. Do not attempt that calculation with missing geometry or material properties.
Read pipe-stress results at the nozzle interface
Once you have the applicable allowable data, read the piping analysis output at the pump flange/nozzle interface. Record the reported forces and moments using the same axes, sign convention, and units as the vendor chart. Keep suction and discharge results separate; do not compare a suction result against a discharge limit just because the nozzles belong to the same pump.
Use the pipe-stress model to determine the loads delivered to the pump, not only whether the pipe passes its own stress criteria. Pipe code stress acceptance and pump nozzle-load acceptance are separate checks. A piping stress below its allowable does not, by itself, prove the nozzle load is acceptable.
Compare the applicable calculated load components and combinations with the vendor's stated limits. If the chart gives a combined-load rule, apply that rule exactly. If it gives directional limits, preserve the chart's directions when mapping model output. Resolve mismatched units, axes, or definitions before making a pass/fail decision.
Minimize nozzle loads when limits are pending
While waiting for vendor limits, use minimum nozzle loading as the design target, especially at the suction nozzle. This is a conservative interim design objective, not permission to declare the installation acceptable without a limit. Do not turn a temporary pipe model into a final pump-load acceptance check.
One modeling technique is to represent the pump flanges as virtual anchors in the stress program, then increase pipe flexibility until the calculated loads at those points are very small. Treat the virtual anchors as analytical constraints only; they are not real supports to install at the pump. Review the resulting layout and support assumptions so that the model represents the intended piping, rather than hiding load through an unrealistic restraint.
After reducing loads, rerun the model and retain the nozzle-interface outputs for comparison when the vendor chart arrives. If the vendor limits later show an exceedance, revise the piping layout or flexibility and repeat the check. Do not accept a “very small” modeled load as proof of compliance when the allowable is still unknown.
Separate nozzle-load symptoms from misleading checks
| Observed result or claim | What it means | Next check |
|---|---|---|
| API 610 data ends at 16 in, but the nozzles are 600 mm and 500 mm | The available table does not cover the stated sizes; it supplies no verified allowable for those nozzles. | Get pump-specific allowable loads from the vendor. |
| Pipe stress is below the piping allowable | The pipe stress check does not establish that external loads at the pump nozzle meet pump limits. | Read interface forces and moments, then compare with the applicable pump data. |
| A proposed screen uses “5,000 to 6,000 psig” or “10%” | Do not use this as a pump nozzle acceptance criterion. The quoted pressure unit is not a pump-specific nozzle-load limit, and a percentage without a defined allowable and method cannot establish acceptance. | Use the correct pipe-stress units for the piping check and obtain the pump vendor's force/moment limits for the nozzle check. |
| Loads are low after adding virtual anchors | The model may help reduce calculated interface loads, but an analytical restraint is not a physical pump support or a vendor allowable. | Check model realism and compare the final loads against vendor limits. |
Close the calculation with a documented comparison
When the vendor data arrives, verify that it matches the pump identity, nozzle, and mounting arrangement. Confirm units and axes before comparing the analysis results. If the vendor provides separate limits or a combination method, follow those instructions rather than substituting a single scalar load.
- Update the stress model with the finalized pipe routing, supports, and flexibility.
- Extract the suction and discharge nozzle forces and moments from the same defined interface used by the vendor data.
- Compare every applicable component and required load combination against the corresponding allowable.
- If any result exceeds a limit, revise piping flexibility or support arrangement and rerun the analysis.
- Record the vendor data reference, model assumptions, units, comparison results, and final disposition with the calculation.
Close the check only after the final analysis satisfies the pump-specific limits and the piping-stress requirements. If the pump identity, mounting details, or vendor allowable data remain unresolved, leave the nozzle-load acceptance open.
FAQ
How do I determine allowable loads for a 600 mm pump suction nozzle?
Request the allowable force and moment data for the exact pump and suction nozzle from its manufacturer. The 16-in table limit described here does not establish an allowable for a 600 mm nozzle.
How do I check pipe stress at a pump nozzle?
Read the forces and moments at the nozzle interface from the piping analysis, align axes and units with the pump data, and compare them with the applicable vendor limits. Passing the pipe-stress check alone does not pass the pump nozzle-load check.
Can I use a virtual anchor to reduce pump nozzle loads?
You can model the flanges as virtual anchors and increase pipe flexibility to drive calculated loads very low, but those anchors are analytical constraints, not installed supports or allowable-load criteria. Verify the model represents the intended piping and compare final results with the vendor limits.
Stop the acceptance review if the vendor data does not cover the exact pump, nozzle, and mounting arrangement, or if the model and chart use incompatible axes or units. Escalate to the pump manufacturer's applications or engineering support for written allowable loads or a pump-specific assessment before releasing the pipe-stress check.