I think this is exactly the issue I came across today
The manual suggest that if you want to compare a numerical input field to a constant (like 'AGE' to a number) you can add 'age > 18' under 'set conditions', but this gives me an error in the Relevance Equation: "This expression uses invalid comparaison. Are you sure you didn't mean numerical compare?". But there is not option in 'conditions' where you can tell Limesurvey that indeed I meant to compare two numbers.

@HSwebteam You got a warning, not an error - the survey will run even if you have warnings.

Feel free to upload your survey here, if it's not private. Then we can have a look. NB: There is intval() you can use for age.

sum(QCODE.NAOK) don't do the trick (false good idea).

It's an easy to add except float are different in PHP and JS id i don't make error ;).

Else
I just check : using condition editor : put 18 : compare is done as numeric : no issue are shown …

Seems really easy to add ;)
https://locutus.io/php/var/floatval/

:)
3.X or 4.X ?
In 4.X : maybe in a core plugin :p

Should be in 3 already, since we have the warning system.

intval() is no plugin. floatval() should be same.

https://github.com/LimeSurvey/LimeSurvey/pull/1344

Fix committed to master branch: http://bugs.limesurvey.org/plugin.php?page=Source/view&id=29273