Describe your application in one clear paragraph
A short, reusable shape for describing what a valve has to do - so the same paragraph works for every supplier you talk to.
Write it once, keep it, reuse it. An application paragraph is the part of an enquiry that does not change between suppliers, and having it ready turns a half-hour of drafting into a paste.
The shape
We [what you do with the gas] using [cylinder type and size] at [working pressure and unit]. The gas is [gas, named exactly]. The valve sits between [what is on the cylinder side] and [what is on the outlet side]. [Flow or bore requirement, if any.] [Safety device requirement and whose rule it comes from, if any.] [Temperature or environment, if unusual.] Volumes are around [quantity] [per period], delivered to [country].
An example
A general example, not a real case: "We fill 10-litre aluminium cylinders with medical-grade N₂O at 5MPa for regional distribution. The valve sits between a taper cylinder thread and a pin-index style outlet used by our customers' equipment. We have no particular bore requirement. A safety device is required by our own filling procedure. Volumes are around 2,000 pieces a year, delivered within the EU."
Nothing in that paragraph is a model, a brand or a specification. It is entirely about the use, which is why it stays valid no matter who reads it.
Four habits that make it work
Name the gas exactly - Not the group it sits in on a catalogue.
Give the unit with the number - Every time.
Say which side is which - Even loosely - "the cylinder side is the taper thread" is enough to start.
Mark what you do not know - An explicit gap is a question a supplier can answer. A silent gap becomes an assumption.