🔩 Leak testing by the bubble emission method — detection and location of leaks by the immersion technique or by applying a liquid to an object under a pressure difference; PN-EN 1593

Materials and NDT PN-EN 1593:

Overview

WHAT THE STANDARD COVERS. EN 1593:1999 (clause 1): procedures for detecting and locating leaks by bubble emission techniques; the sensitivity depends on the technique and the materials used. Two techniques are described: a) immersion — with specified equipment it can be used for quantitative measurements (informative Annex A); b) liquid application. The standard can be applied to equipment that can be evacuated (vacuum) or filled with gas under pressure. The "Scope" field of the PKN card of PN-EN 1593:2004, in full (our translation): "Procedures are specified for detecting and locating leaks by the described bubble emission techniques: immersion and liquid application" (without a full stop on the card). The standard was prepared by committee CEN/TC 138 "Non-destructive testing". References: EN 473 (qualification of non-destructive testing personnel), EN 1330-8 (leak testing terminology — the definitions come from it), EN 1779:1999 (criteria for the choice of the leak testing method). Table of contents: 4 personnel qualification, 5 principle, 6 general requirements, 7 interfering factors, 8 immersion technique, 9 other techniques using liquids, 10 test report, Annex A (informative) — example of quantitative leak assessment.

PRINCIPLE AND GENERAL REQUIREMENTS (EN 1593:1999, clauses 4–6 — text read from the scan of the sample). It is assumed that testing is carried out by qualified personnel; it is recommended that qualification be confirmed by certification according to EN 473 or equivalent. Principle: a pressure difference is created across the wall of the object and the formation of bubbles in a liquid on the lower-pressure side is observed; the smallest detectable leak depends on the pressure difference, the gas and the liquid. The location of the leak shall be visible directly or indirectly, in order to check whether it is a real leak in the tested area. The test gas is usually air; inert gases may be used — the hazard of an oxygen-deficient atmosphere shall then be taken into account. It shall be checked that the object is designed for the test pressure difference, and the test conditions shall neither permanently deform the object nor endanger the operators. With the immersion technique the pressure in the closed object is maintained before inspection for the time needed for the bubble emission to stabilize — with small leaks this may take several minutes. Temperature of the tested surface usually not lower than 278 K (5 °C) and not higher than 323 K (50 °C) throughout the test; local heating or cooling may be used if the temperature stays within this range; other temperatures — when the procedure has been shown to be suitable. Direct visual inspection: the surface is viewed from a distance not greater than 0.6 m, at an angle not less than 30° (the text of the standard says "1/6 rad (30 degrees)", although 30° is π/6 rad); mirrors and magnifiers may be used; lighting, if necessary with a torch, recommended 350–500 lx. Indirect visual inspection (mirrors, endoscopes, telescopes) — with a resolution at least equal to direct inspection.

AMENDMENT A1:2003. It deletes informative Annex ZA on the relationship with Directive 97/23/EC (pressure equipment) and amends the table of contents and foreword accordingly; it does not change the test procedures.

STATUS (state of the PKN card on 10.10.2026). The card of PN-EN 1593:2004 (Polish version) carries no withdrawal label: title "Badania nieniszczące -- Badania szczelności -- Próba pęcherzykowa" (Non-destructive testing — Leak testing — Bubble test; our translation), publication 04-10-2004, 13 pages, Sector of Basic Issues and Management Systems, KT 7 Non-Destructive Testing, "Replaces: PN-EN 1593:2002 - English version", "Introduces: EN 1593:1999 [IDT], EN 1593:1999/A1:2003 [IDT]", ICS 19.100. In the iTeh catalogue (read on 10.10.2026) EN 1593:1999 has the status "Published", the last stage of the CEN periodic review — "9060 – Closure of 2 Year Review Enquiry" dated 04.06.2025.

HOW MANY LABORATORIES AND IN WHAT FORM (copy of the accreditation scope database of 10.10.2026 and current PCA documents read on 10.10.2026). The number 1593 appears in 9 records at 9 laboratories; the number is present in all 9 current PCA documents, no entry is suspended. 8 of them have leak testing by the bubble method: AB 608, AB 1327, AB 1646, AB 1700, AB 1754, AB 1844, AB 1888 and AB 1900. The ninth, AB 054, has "PN-EN 1593" in the entry "Waste — loss on ignition (LOI), gravimetric method, range 1.0–99.0 %" — this standard does not concern that quantity, so we do not count this laboratory. Forms: "PN-EN 1593:2004" (6 laboratories; AB 1844 adds "EN 1593:1999 + EN 1593:1999/A1:2003"), "PN-EN 1593" without a year (AB 608) and "PN-EN ISO 1593:2004" (AB 1700 — there is no standard with ISO in its designation under this number). The "Laboratories" tab searches for "PN-EN 1593:" (with a colon) and shows 6 laboratories: AB 1327, AB 1646, AB 1754, AB 1844, AB 1888 and AB 1900; without the colon it would show several dozen laboratories with other standards — most of them with PN-EN 15935 (64 laboratories), PN-EN 15934 (41) and PN-EN 15936 (11) (measurement on the database copy on 10.10.2026, all countries). AB 608 and AB 1700 are outside the tab because of the way the number is written.

WHAT THE LABORATORIES TEST (copy and PCA documents). Subject: welded joints in metallic materials (AB 1327, AB 1700, AB 1844, AB 1888), metallic products and materials (AB 608, AB 1754, AB 1900), technical equipment and steel structures (AB 1646). Quantity: leaks (detection, location of a leak — AB 1646) by the bubble method; no laboratory states the technique (immersion or liquid application) or a quantitative range.

WHERE A SEEMINGLY CORRECT RESULT IS EASY TO GET. First — too short a stabilization with the immersion technique: small leaks need several minutes before bubbles appear; inspection immediately after immersion gives "leak-tight". Second — a temperature outside 5–50 °C (cold object, hot weld) changes the behaviour of the liquid; a different temperature only with a procedure shown to be suitable. Third — inspection from more than 0.6 m or in poor light (recommended 350–500 lx) will miss single bubbles. Fourth — the sensitivity depends on the pressure difference, the gas and the liquid: "no leak" without stating these conditions says nothing; the leak testing method is chosen according to the criteria of EN 1779. Fifth — a number with ISO in it or without a year does not identify the document unambiguously.

WHAT WE DO NOT GIVE. The sample of the standard (scan) ends at 6.6. We do not give the content of clauses 7–10 (interfering factors, the procedure of the immersion technique and of the liquid application technique, types of liquids and foaming solutions, test report) or the example of quantitative assessment from Annex A.

Method principle

A pressure difference is created across the wall of the object (gas overpressure in the object or vacuum) and the formation of bubbles in a liquid on the lower-pressure side is observed — in a bath in which the object is immersed (immersion technique) or in a liquid applied to the surface (liquid application technique). The smallest detectable leak depends on the pressure difference, the gas and the liquid (EN 1593:1999, clauses 1 and 5).

Applications

• Equipment that can be evacuated or filled with gas under pressure (EN 1593:1999, clause 1)
• Welded joints, metallic products and structures — detection and location of leaks
• In the accreditation scopes: 8 laboratories testing leak-tightness; none states the technique or a quantitative range

Key parameters

Standard

Standard number

PN-EN 1593:2004 (wersja polska; wprowadza EN 1593:1999 [IDT] i EN 1593:1999/A1:2003 [IDT])

Title (PL)

Badania nieniszczące — Badania szczelności — Próba pęcherzykowa

Title (EN)

Non-destructive testing — Leak testing — Bubble emission techniques

Step-by-step procedure

1. Preparation

   Check that the object will withstand the test pressure difference without permanent deformation and without endangering the operators; choose the gas (usually air); surface temperature 5–50 °C.

2. Creating the pressure difference

   Fill the object with gas under pressure or create a vacuum; with the immersion technique maintain the pressure until the bubble emission stabilizes (several minutes for small leaks).

3. Liquid

   Immerse the object (immersion technique) or apply the liquid to the tested surface (liquid application technique); we DO NOT GIVE details.

4. Visual inspection

   Directly from ≤ 0.6 m, at an angle ≥ 30°, at 350–500 lx, or indirectly with instruments of at least the same resolution; check whether the indication is a real leak in the tested area.

5. Test report

   According to clause 10 (we DO NOT GIVE its content); state the technique, gas, pressure difference and liquid. PN-EN 1593:2004 current (state of the PKN card on 10.10.2026).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Object under gas pressure — risk of bursting; test pressure not greater than provided for by the design (6.2)
• Inert gases — risk of an oxygen-deficient atmosphere in the room (6.1)
• NOTE ON SUBSTANCE: a result without the technique, pressure difference, gas and liquid is not comparable

Frequently asked questions