Process tool
Coating drying capacity and maximum spray rate calculator
How much water your inlet air can actually carry away, and the spray rate that supports.
- Runs in the browserNothing is submitted anywhere
- Working shownCheck every line by hand
- Plant figuresThe bands our grades run in
- Free, no sign-inNo account, no email
Written by the Rglax Pharma technical team, who formulate and manufacture every grade named on this calculator at our WHO-GMP works in Tahliwal, Una (drug manufacturing licence NNZ/23/238). Reviewed 3 September 2026. Licences and certificates.
Result
Drying capacity
479 g/min of water
- Ambient moisture
- 11.85 g/kgWater already in the air
- Exhaust moisture
- 28.34 g/kgWhat the air can hold on the way out
- Dry air mass flow
- 1,743 kg/h
- Maximum spray rate
- 563 g/minDispersion, at the solids above
How this was worked out
- inlet humidity ratio = 0.622 × pv ÷ (101.325 − pv) at 25 °C, 60% RH = 11.85 g/kg
- exhaust humidity ratio at 40 °C, 60% RH = 28.34 g/kg
- dry air mass = 1,500 m³/h × 1.162 kg/m³ = 1,743 kg/h
- capacity = 1,743 kg/h × 16.48 g/kg ÷ 60 = 479 g/min
- max spray = capacity ÷ (1 − 15 ÷ 100) = 563 g/min
Formula
saturation pressure, Antoine: log10 P = 8.07131 − 1730.63 ÷ (233.426 + T) humidity ratio W = 0.622 × Pv ÷ (P − Pv) drying capacity = dry air mass flow × (W exhaust − W ambient)
Why this number matters
This is the calculation that explains why a coating process that ran perfectly in February fails in July. The air can only carry away the difference between what it already holds and what it can hold at the exhaust condition. On a humid day that difference collapses, the bed stops drying at the spray rate you have always used, and you get picking and sticking on a formulation nothing has changed about.
Where it goes wrong
Treat the answer as a ceiling, not a setpoint. Run at 70 to 80 percent of it. And check it against the worst ambient humidity your site sees rather than today, because the process has to hold through the monsoon.
Worked example
With air volume of 1500 m³/h, ambient temperature of 25 °C, ambient humidity of 60 % RH, exhaust temperature of 40 °C, exhaust humidity of 60 % RH and dispersion solids of 15 % w/w, the calculation gives:
- Ambient moistureWater already in the air
- 11.85 g/kg
- Exhaust moistureWhat the air can hold on the way out
- 28.34 g/kg
- Dry air mass flow
- 1,743 kg/h
- Drying capacity
- 479 g/min of water
- Maximum spray rateDispersion, at the solids above
- 563 g/min
The arithmetic is 3 lines, shown beside the result above so it can be checked by hand: saturation pressure, Antoine: log10 P = 8.07131 − 1730.63 ÷ (233.426 + T); humidity ratio W = 0.622 × Pv ÷ (P − Pv); drying capacity = dry air mass flow × (W exhaust − W ambient).
Typical ranges
- Air volume(m³/h)Inlet air handling capacity
- Ambient humidity(% RH)The monsoon figure is the one that bites
- Exhaust humidity(% RH)Above about 70% the bed stops drying
These are the bands our grades were developed in at Tahliwal. A run outside them is not wrong, but it is a run the published parameters no longer describe.
Other calculators
- Coating weight gainHow much dry coating material a batch needs at a target percentage weight gain, including process loss.
- Coating dispersionWater or solvent needed to disperse a ready-mix powder at a given solids concentration.
- Spray rateSpray rate per gun and total run time from your dispersion quantity and available process window.
- Pan speedTangential bed velocity from pan diameter and RPM, with the range most film coating runs sit in.
- Dispersion vesselVessel volume, diameter and impeller size for the dispersion quantity you are making.
- Surface area and build-upSurface area per tablet and coating build-up in mg per square centimetre, which is how enteric coats are specified.
Every grade page carries the process parameters it was developed on, so you can start from a known point rather than a calculated one. Browse the grades.
Read next
- Moisture barrier coatingMoisture sensitive cores are the case where drying capacity, not output, sets the run.
- CVS-101, moisture barrierFormulated for Amoxycillin and Clavulanate, where the core will not tolerate a wet bed.
- Tablet coating weight gain calculatorHow much dry coating material a batch needs at a target percentage weight gain, including process loss.
- Coating dispersion and solids calculatorWater or solvent needed to disperse a ready-mix powder at a given solids concentration.
- Coating spray rate calculatorSpray rate per gun and total run time from your dispersion quantity and available process window.
- Coating defects, and what causes themWhat the bed looks like when this number is wrong, and which parameter to move.
Need a second opinion
Talk to our technical team.
Send the core, the coater and the target and we will tell you what we would run, and which grade we would run it with.
From the calculation to the pan.