DE102005008308A1 - Leakage detection method e.g. for leakage protection linings of tanks and containers, involves cleaning welding seams and sheet metal surfaces with water or fine-grained sand which are then dried by radiant heat - Google Patents

Abstract

The method involves cleaning welding seams and sheet metal surfaces with water or fine-grained sand which are then dried by radiant heat. Examination of a lining is made by an exterior check of the seams and surfaces for large leakages. A monitored area is examined for internal tightness by a gas and a sensor. An examination is made for internal tightness, where determined leakages are sealed immediately by welding and again sensed. If no leakage is proved, all seams and surfaces are examined by a vacuum chamber and any leakages if necessary are welded and a new examination.

Description

The The invention relates to a method for leak detection on leak-tight monitoring spaces forming leak protection linings from connected by welds Steel sheets for with leak detection system equipped Container, Tanks o. The like., In which groundwater hazardous liquids are stored, at first the test pressure in the surveillance room determined and documented, then the leak monitoring system except Operation, disassembles the piping connections associated with the leak monitoring system be, with the interstices with a test gas be charged.

To protect against the escape of flammable, especially groundwater damaging liquids from tanks, containers or silos due to leaks, it is known that the hazardous liquid in double-walled containers or tanks ( DE 40 15 821 A1 . DE 41 27 090 A1 ) to store. The monitoring of the cavity formed between the inner and outer shells is performed by means of a Unterducküberwachung that detects a change in the negative pressure in the cavity due to leakage and displays.

These known solutions enable it is not, however, to pinpoint the leakage.

From the DE 40 00 699 C1 is a method for localizing a leak on a gas and / or liquid-filled body is known, which is arranged in a sheath, wherein a cavity is formed between the casing and body, by arranging at least one transmitter in the cavity between the body and casing for delivering a certain electromagnetic radiation and at least one receiver for receiving and for quantitatively detecting absorption bands within the electromagnetic radiation emitted by the transmitter.

Another known solution ( DE 198 53 049 A1 ) is used to detect a leak in a test object, such as vacuum apparatus, gas and tank containers, a carrier gas such as helium and a test gas such as air. The carrier gas is supplied to the test object, removed therefrom and passed to the outside of the test object adjacent test gas, wherein the test gas is applied at a higher pressure than the carrier gas. For detecting test gas constituents, laser diodes, absorption cells and photodetectors are used.

Also With this known prior art, the exact location of a Leakage on larger tanks or containers can not be determined.

These disadvantages the prior art tries DE 43 22 859 A1 . DE 102 34 190 A1 . DE 43 24 865 A1 ) in that fluid-selective sensor cables are arranged within the interstitial space formed between the outer and inner floors, or a plurality of locally distributed leakage sensors are used.

Tank bottoms or interstices exist from a variety connected by welds Single sheets with flanges, overlaps etc. Despite a large number of misplaced leakage sensors can be the exact location of the leak does not notice, since the sensors by no means laid along the welds are.

In addition, can This known state of the art cost only for tank new buildings be used.

at In this prior art, the object of the invention is to provide one for United Tanke and containers equally suitable locating method for To provide leaks, despite its robustness over the necessarily has high accuracy, reliable and at the same time cost-effective as well as Tank new buildings as well as older ones Tank structures is applicable.

These The object is achieved by the Characteristics solved in the characterizing part of the main claim. Advantageous embodiments The invention are described in the subclaims.

Of the inventive idea consists of stepping the location of the leaks, i. by a iterative sequence of interrelated but easily reproducible sequences Performing processing and testing operations, the To determine coordinates of the leak and the leak detected immediately after its localization safely and inexpensively eliminate.

requirement for that is, that the surfaces the leak-proof linings of the interstices outwardly can be controlled visually, so that the to be tested Welds and sheet metal surfaces of Product residues, deposits, encrustations, paint residues, rust or other contaminants must be exempted. This is done appropriately in step P1 by irradiation with water or sand under High pressure.

All test areas are then heated by propane burners or heaters Radiation in step P2 externally dried intensively.

The Interior of the tank or tank must while of the entire testing process be navigable and walkable, which is why the oxygen and carbon monoxide as well as the explosive vapor / air concentration in the tank / tank constantly measured and monitored so that the testing works without respiratory protection possible are.

Before with the test procedure must be started, the existing leak detection system of the tank except Operation. Conveniently, become the pipe connections of the leak monitoring system disassembled and instead of the pipe connections test connections for Monometer, Digitalmeßgeräte, shut-off valves etc. mounted so that the interstitial space with a test gas durbebeaufschlagt or a flow can be carried out with gas.

Of the first test step P3 of the method according to the invention This is the cleaned and dried test surfaces of an external visual inspection to undergo and conspicuous Welds and / and sheet metal surfaces to locate. The localized sites are identified by bubble detection under vacuum bell at low pressure for the presence of large leaks checked. Any detected leaks are immediately with closure plates by welding closed. This ensures that the subsequent examination of the interstitial space is up Do not leak through out big ones Leaks escaping test gas disturbed or falsified becomes. To the first test step belongs Furthermore, a pre-inspection for internal tightness by means of negative pressure, which makes it possible information about the magnitude of a to receive existing leaks. After a service life of three hours can by the test pressure change on the size of the leak concluded become.

Of the first test step P3 is thus a leak test with negative pressure for the detection of Leaks in welds and sheet metal surfaces without big ones equipment expenditure executable is and delivers reproducible results.

At the first test step P3 closes the exam the interstitial space internal tightness in at least two further steps P4 and P5. At step P4, it may become possible from the inner monitoring rooms existing gas atmosphere, Product and water with a test gas such as. Hydrogen or helium under defined pressure applied and the outer welds and sheet metal surfaces by means of sniffer probes checked. The condition is that before the start of the test possibly existing gas atmosphere, product residues and remove water in the monitoring rooms become. This is done by suction through the existing test connections. Identified Leaks are immediately closed with a closure plate, welded and again checked.

can In step P4, no leak is detected, is in another Step P5 the corresponding monitoring space leveled to its low point and by tapping a connection to Produced outside atmosphere, so that maybe existing residual amounts of gas atmosphere, product and water easily on the Drilling can be sucked.

The step P5 additionally contains a drying of the interstices. The drying is carried out in a simple manner in which a drying gas is passed through the interstitial space via the test connections. Any residual amounts of liquid in inaccessible areas of the interstitial space are blown out and dried out the interior of the interstitial space. This is so important because even the smallest residual fluid clogs leaks with a leak rate smaller than q _L = 10 ^-2 Pa m ³ s ^-1 , which means they can no longer be detected.

To Drying is the test the welds and sheet metal surfaces with sniffing probes.

results also, the step P5 no evidence of leaks at the welds and sheet metal surfaces the leakage protection lining, a third test step is followed by means of bubble detection at negative pressure, which is accessible from the outside Welds and sheet metal surfaces includes. Once a leak is detected, the closure is done by weld together with a closure plate.

The inventive method secures through its iterative process from simple to step by step more complex scope of testing a cost-effective and at the same time manageable Leak detection even at large complex tank structures.

It is for both older tank farms as well as for Tank newbuild well suited and the rather rough tank operation well customized.

The Invention will be described below to an embodiment of the hand Drawings closer explained become.

It demonstrate:

1a and 1b a side view of a monitoring space of overlapped or butt welded tear sheets,

2 a side view of a tank with horizontal bottom and connections for a test line, suction line and a measuring line to the interstitial space,

3 a top view 2 and

4a to 4d a schematic flow chart of the method according to the invention,

The method according to the invention is intended to be used for a leak detection on a leak protection lining of a tank with a horizontal bottom. In 1a and 1b is schematically the tank 1 with surveillance space 2 shown, which latter consists of overlapping welded tear sheets 3 of the upper tank bottom 4 and lower tank bottom 5 is formed. It goes without saying that the surveillance space 2 may also consist of overlapped welded smooth plates or butt-welded smooth plates, without departing from the invention.

As 2 and 3 dargestellen is with the interstitial space 2 a measuring line 6 with measuring line flange 7 or screw connection connected. The measuring line 6 is through the tank jacket 8th guided. One also through the tank jacket 8th guided suction line 9 with flange 10 or screwing is also with the interstitial space 2 in connection with which it is possible the interception room 2 to evacuate. Furthermore, at least two test sockets 11 and 12 , the further accesses to the surveillance room 2 allows. These existing connections, which actually belong to the leak monitoring system, are used to the necessary for the execution of the method according to the invention devices, apparatus and devices such as manometers or digital measuring devices 13 , ex-proof vacuum pumps 14 , Drying equipment 15 , Test gas cylinders 16 , Pressure reducer 17 , Shut-off and opening valves 18 as well as collecting container 19 to join.

The 3 shows in the plan view of the tank bottom, the distribution of Prüfstutzen 11 and 12 , the outer circumference of the tank shell 8th are arranged, which have approximately an angular distance α of 120 °. This ensures that the entire surveillance space 2 uniformly applied by the test gas, no pressure peaks in the interstitial space 2 be caused and for the devices, fittings and lines sufficient space is available.

The course of the method according to the invention is in the 4a to 4d clarified.

Before carrying out the leak detection on the leak protection lining of the tank 1 can be started, is initially in fully intact leak protection system, the test pressure in the interstitial space 2 by means of manometer, such as digital pressure gauge, measured and documented accordingly. The leak protection system is then put out of operation, the interstitial space 2 depressurized and dismantled the pipe connections of the leak protection system. To the flange 7 the measuring line 6 , the flange 10 the suction line 9 and the test socket 11 and 12 The appropriate equipment and equipment are installed as described above.

For further testing on and in the tank, appropriate driving, grinding and welding approvals for the interior of the tank are required 1 available. Power connections for the lighting inside the tank and the power supply of the welding equipment must also be present.

During the entire test procedure must the oxygen and carbon monoxide concentration and the explosive vapor / air concentration constantly in the tank and the test area measured and monitored so that working without respiratory protection is readily possible.

The Leak detection by the method according to the invention begins with step P1, which requires careful cleaning the outer test surfaces of Leak protection lining includes. All welds and related sheet metal surfaces will be treated with a jet of water under high pressure or sandblasted to deposits, paint residues, rust, product residues, slag or soiling other kind are removed.

The cleaned surfaces will be afterwards in step P2 carefully dried. This happens, for example, by a propane burner or radiant heater developed thermal radiation. Especially corner areas need be completely dry.

In the first test step P3 described below, a visual inspection of the cleaned weld seams and sheet metal surfaces for defects, obvious defects or other irregularities is carried out by inspection and the identified defects are marked. The marked defects, ie the corresponding welds and sheet metal surfaces are then subjected to a leak test by means of bubble detection under negative pressure on their externally accessible side. The areas to be tested are coated with a foam-forming commercial test solution. A vacuum bell (test frame with an externally visible Viewing window) is pressed onto the area to be tested. The vacuum bell is evacuated by means of a vacuum pump to a negative pressure of pu = 0.5 bar. If a foam crown forms within the vacuum bell, the test area covered by the vacuum bell has a leak. The leak is localized and marked after the vacuum bell has been unloaded and removed from the test area. The site is cleaned, dried and sealed by means of closure plate by welding to the sheet of the leak protection lining. After sealing, the leak is subjected to a repeat test by means of the bubble detection method. This procedure is continued until all visually detected defects are removed and sealed, as shown 4b is to be taken.

are eliminated any visual imperfections or could not leak in the test step P3 are started, is started with the test step P4, the examination of the interstitial space on inner tightness includes.

The test step P4 is divided into two interdependent substeps A1 and A2 (in 4b the clarity not dagestellt), which are described in more detail below.

In sub-step A1, they become the interception space 2 leading test socket 11 and 12 closed by shutting off the corresponding shut-off valves. The suction line 9 remains open and is connected to an ex-proof vacuum pump 14 connected, with their help in the interstitial space 2 a negative pressure is generated, which makes it possible to suck off any product, water including the gas atmosphere and into the collecting container 19 to empty. After suction, the vacuum is reduced to about 0.5 bar over a service life of at least 3 Held hours for pre-inspection and then the negative pressure in the interstitial space 2 set to about 300 mbar absolute. This measure is used to estimate the leak size.

The surveillance room 2 is then with a test gas, for example helium, hydrogen or hydrogen-nitrogen mixture, from the test gas cylinder 16 via a pressure reducer 17 is applied to a defined test pressure, which is selected so that no damage occurs at the leak protection lining.

For example, with a horizontal leak-proof lining, the test pressure is included 6 mbar. All shut-off valves on the measuring line 8th , the suction line 9 and the test socket 11 respectively. 12 be closed, leaving the surveillance room 2 is below the defined test pressure. The test pressure is transmitted via the to the measuring line 6 connected pressure gauge constantly checked.

The Leak detection in substep A2 begins with a sniffer probe, the test gas traces emerging from any leaks appeals, about the ones to be tested Welds and sheet metal areas is pulled. A hydrogen sniffer probe is already detecting Traces of hydrogen, sets detected traces of hydrogen in optical and audible warning signals around, with the volume of the warning signals approaching increase the leak or remove it when removing it from the leak.

The Localization of the leak is advantageously carried out so that the area to be tested in the opposite direction. Is the leak localized, it will be marked accordingly.

The Leak is closed immediately after its identification by a closure plate and welded to the leak protection liner or closed only by a weld.

This is followed by an inspection of the sealed leak. For this purpose, the test gas is in the interstitial space 2 refilled in accordance with the selected test pressure and, if appropriate, carried out in the test area an air exchange, so that the test gas concentration in the environment of the test area decreases so much that a re-sniffing the welds and sheet metal surfaces is possible without errors. This test and work continues until all leaked leaks are sealed (see 4b ).

If no leak is detected in substep A2 or all leaked leaks are sealed, then test step P5 begins. The surveillance room 2 is achieved by opening the shut-off valves on the suction line 9 and the Püfstutzen 11 respectively. 12 depressurized and the test gas escapes into the atmosphere.

By means of a leveling the relevant surveillance space 2 to its lowest point TP (see 1 ) leveled out. To the low point TP of the interstitial space 2 is an external access by tapping with a diameter of up to 10 mm 5 to 10 Made bodies.

About this Access then takes place Aspiration of any remaining liquid.

This is followed by drying and dehumidifying the interstitial space 2 at. At the test tube 11 is when the test socket is closed 12 a drying device 15 connected, for example, generates a heated air flow, which over the interstitial space 2 for example, the suction line 9 is fed so that by the Surveillance space a forced flow takes place, the moisture particles in the interior of the interstitial space entrains and dehydrates the interstitial space. Nitrogen has proved to be the drying gas in addition to the air.

The Humidity in the interstitial space is by measurement at the effluent from the interstitial space drying gas measured. The forced flow is maintained until the remaining low residual moisture the following test no longer significantly impeded or falsified.

The Burrs are covered with closure plates and tight with welded to the sheets or angles of the leak protection lining.

The drying device 15 is from the test socket 11 dismantled and closed by shutting off the shut-off valve. The other test piece 12 stays closed and the suction line 9 open. As previously described, is via the open suction line 9 a test gas, for example a hydrogen-nitrogen mixture, with a defined test pressure, for example 6 mbar, from the test gas cylinder 16 over the pressure reducer 17 , the surveillance room 2 fed again.

It includes the snooping the welds and sheet metal surfaces with hydrogen sniffer probes at. As soon as these lead over the Test surface responds, there is a leak found after localization and labeling immediately through a closure plate covered and welded to the leak protection lining.

The test gas in the interstitial space 2 is refilled, brought to the appropriate test pressure, for example, 6 mbar, and held. Any test gas concentration increases occurring in the immediate vicinity of the leak detected and sealed are removed by air circulation.

Of the Test step P5 continues with another sniffing of the welds and sheet metal surfaces of the sealed leak.

The The procedure continues until all detected leaks are commensurate sealed and inspected are.

Become in the test step P5 does not detect any leaks, the further leak detection starts with the Test step P6 continues. In the test step P6 will be the entire outside accessible Test surface of a Leak testing after the bubble detection at a test pressure of pu = 0.5 bar subjected. The exam corresponds to that in the test step P3 method described, only with the difference that the test is not only selectively, but nationwide is applied.

1

tank

2

monitoring room

3

Tränenblech

4

upper tank bottom

5

lower tank bottom

6

Measurement line

7

Flange or screw connection of 6

8th

tank shell

9

suction

10

Flange or screw connection of 9

11 12

test connector

13

Measuring device

14

Vakummpumpe

15

drying device

16

test gas cylinder

17

pressure reducer

18

Shut-off valves

19

receptacle

TP

low

α

Angular distance of the test sockets 11 . 12

Claims (11)

Leak detection method for leak-proof linings made of steel sheets connected by welding seams for containers equipped with leak monitoring system, tanks o. The like., In which groundwater hazardous liquids are stored, first determines the test pressure in the interstitial space and documented, then the leak monitoring system is taken out of service and the piping connections belonging to the leak monitoring system are dismantled, the test chambers being supplied with a test gas, characterized in that the leak detection is carried out in a sequence of interlinked machining and test operations in the following working and test steps: (P1) cleaning of the welds to be tested and sheet metal surfaces of the leak protection lining from product residues, deposits, encrustations, paint residues, rust, slag or other soiling by irradiation with water or fine-grained sand at overpressure; and (P2) drying the weld seams to be tested and sheet metal surfaces of the leak protection lining by heat radiation by means of propane burner, heater or the like; and (P3) checking the leak-proof lining by externally checking visually prominent welds and sheet surfaces for large leaks by means of bubble detection at a vacuum of pu = 0.5 bar and repairing any defects and faults found immediately; and (P4) checking the interstitial space for internal Tightness (leaks) by exposure to the test gas at a defined overpressure and a subsequent external sniffing of the welds and sheet surfaces after escaping test gas by sniffing probes responsive to the test gas at evacuated gas atmosphere, product and water monitoring space, where detected leaks sealed by welding immediately after localization and then sniffed again; and (P5) checking for internal leakage by externally prepared access of the additionally dried interstitial space if no leak is detectable after step (P4), and any leaks detected are immediately sealed by welding after being localized and then re-sniffed; and (P6) if no leak is detectable after step (P3, P4 and P5), Check for external tightness of all welds and sheet surfaces by bubble detection by means of a vacuum bell at a vacuum of at least pu = 0.5 bar and immediately closing any leak detected Welding and subsequent retesting. Method according to claim 1, characterized in that that the inspection process after step (P5) comprises the following individual steps: a) Determine the low point of the interstitial space leveling; b) Establishing access to the low points the surveillance room by drilling and / or cutting and aspirating possibly existing Gas atmosphere, Product and water; c) drying the interstitial space by means of a dehumidifier, Heating or nitrogen loading; d) measuring the humidity in the surveillance room; e) close the holes through locking plates by welding; f) Charging the interstitial space with test gas according to step P4 .; f) re-sniffing the one to be tested Welds and sheet metal surfaces by means of sniffer probes to determine the tightness. Method according to Claims 1 and 2, characterized that while of the entire inspection process the oxygen and carbon monoxide concentration as well as the explosive vapor / air concentration If necessary, also other chemical compounds in the tank / tank measured and monitored becomes. Method according to claim 1, characterized in that that in the interstitial space existing gas atmosphere, bearing liquid and water over Separator with ex protected Vacuum pumps over the test, Measuring and suction line connections of the Leak Detection System be sucked off and emptied into a collecting container for intermediate storage. Method according to claim 1, characterized in that that in the interstitial space a negative pressure of about 0.2 to 0.8 bar for pre-control over a Service life of at least 3 h by means of ex-protected vacuum pump is generated. Method according to claim 1, characterized in that that the interstitial space is evacuated to absolutely 300 mbar. Method according to claim 1, characterized in that that the interstitial space with test gas up to to one of the nature and construction of the leak-proof lining dependent Gas pressure applied is, with the pressure of the test gas constantly through Measurement is controlled and maintained. Method according to claim 7, characterized in that that as a test gas Helium, hydrogen, nitrogen or a mixture of hydrogen and nitrogen is used. Method according to claim 7, characterized in that that the test pressure of the test gas at tank bottoms and tank coats is set to 2 to 6 mbar. Method according to claim 1, characterized in that that as sniffing probes Helium or hydrogen probes are used, which over the tested Weld or sheet metal surface to be pulled. Method according to claim 1, characterized in that that the detected leaks immediately after their localization by welding sealed and the sealed leaks again by snooping a Leak testing be subjected.