Air-Jet Relay Nozzle Wear & Airflow Drop Calculator

The formula

This is the expression the tool evaluates. Every term is named underneath, with the unit it must be supplied in.

How the result is derived

Step by step, from the values you type to the figure on screen.

1. The 7 inputs are read from the form on every keystroke: New Orifice Diameter, Wear Rate, Picks Since New, Replacement Threshold, Velocity Loss per % Area, Air Consumption when New and Compressed Air Cost.
2. Each value is checked against the accepted range in the input table below. A value outside its range stops the calculation rather than producing a misleading figure — the results blank out and a message appears.
3. The validated values are substituted into the expression above, which resolves Current Orifice Diameter together with every supporting figure in one pass — no value is carried over from a previous entry.
4. The supporting outputs — Orifice Area Increase, Air Flow Increase, Jet Velocity Lost, Picks to Replacement and Extra Air Cost — come from the same pass, so they always describe the same case as the headline figure.
5. Results are rounded for display only. The full-precision value is used throughout the chain, so reading a rounded intermediate figure back into the tool by hand can shift the last digit.

What each input means

Where to read each value on the floor, the unit it must be in, and the range the tool accepts.

What the tool returns

The headline figure and every supporting value it is built from.

Worked example

The tool loads with this case already solved — the Current Orifice Diameter shown above is its answer. Change one value and the difference from this baseline is the sensitivity of the result to that variable.

How to use it

1. Work through the input groups in order — Nozzle and Consequence. The defaults are a realistic case, so you can change one value at a time and watch what moves.
2. There is no calculate button. Every figure recalculates as you type or drag, which is what makes this usable for a what-if sweep rather than a single answer.
3. Read Current Orifice Diameter in the dark results panel — that is the headline figure, expressed in mm.
4. Check the supporting rows underneath (Orifice Area Increase, Air Flow Increase, Jet Velocity Lost, Picks to Replacement and Extra Air Cost) before acting on the headline — they are where an implausible input usually shows itself first.
5. Reset to defaults returns every field to the reference case, which is the quickest way to check whether a surprising result came from the tool or from an input you had changed earlier.

Where this is used

• Process planning — establishing Current Orifice Diameter before a trial is booked, so machine time and material in Predictive Maintenance & Spare Parts Physics are committed against a calculated figure rather than an estimate.
• Costing and quotation — Current Orifice Diameter is an input to the cost sheet, and quoting from a worked number rather than a remembered one is what keeps a margin intact.
• Troubleshooting — when the floor result drifts from plan, entering the measured values (starting with New Orifice Diameter) shows how much of the gap in Current Orifice Diameter each variable explains.
• Teaching and study — the accepted ranges bracket normal Predictive Maintenance & Spare Parts Physics practice, so moving one variable at a time shows the shape of the relationship rather than a single answer.

Assumptions and limits

• A negative picks-remaining means the nozzle is already past its threshold, which is the common finding — relay nozzles are cheap and rarely tracked, so they are usually changed on a stoppage rather than on wear. Uniform linear erosion is assumed and real wear is directional, biased toward the side the weft strikes, so the jet loses coherence and aim before the diameter figure suggests. Flow is taken as proportional to area at constant pressure, which holds for choked flow through a sharp orifice and less well once the edge has eroded round. Measure a sample of nozzles with pin gauges before acting on any of it.
• Every input is bounded to the range normal practice occupies (New Orifice Diameter 0.5 to 5 mm, Wear Rate 0.01 to 20 µm per million picks and Picks Since New 0 to 5000 million, and so on for the rest). Those bounds are guard rails against typing errors, not a claim that the formula fails one unit outside them.
• The calculation is deterministic: the same inputs always give the same result. It carries no allowance for machine condition, operator skill, ambient conditions or lot-to-lot material variation unless an input above explicitly represents one.
• Nothing is sent anywhere. The maths runs in your browser, so the numbers you type never leave the page.

Questions people ask