C´est la chute maximale de la pression statique

This is the term that chemical and mechanical engineers use.

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Note added at 1 hr (2012-09-04 00:29:06 GMT)
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Sometimes "chute" means pressure drop. The last phrase is confusing, "for the maximum static chute and the test pressure". Therefore I do not have a firm opinion on whether a "static pressure drop" is meant here. More details of the test setup would be needed.

Imho

The document explicitely references EN-1261-1, my copy is tattooed to my name, but a freely accessible copy is here:
http://www.nortech-v.com/tech/bs en 12266.pdf
Table 14-3 on page 12 mentions only "test pressure", assuming 0 pressure on the other side of the valve.

A4.2 specifies: "The test pressure (see A.1.6) shall be a minimum of 1,1 times the allowable differential pressure at room
temperature",

thus by this standard we should use "differential pressure"

and to explain further, "chute" is a pressure drop measured as a difference in dynamic condition (ie with a flow for the concept of "pression dynamique" in French), and "différence" is the susbstraction of the pressure values measured at inlet and outlet of the valve, in static condition (no flow, and the leak test of valve closure is precisely at quasi-zero flow)

The advantage of this wording is that it matches precisely the standard quoted as a reference, which may be a good excuse to have a target a bit more consistent than source in translation

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Note added at 16 heures (2012-09-04 15:55:42 GMT)
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Please correct EN 12266-1 in my first line, official document available here for example, I purchased it for a valve manufacturer of my clients:
http://www.techstreet.com/cgi-bin/detail?doc_no=bs_en|12266_1_2003;product_id=1111048