LD

S

Technical details

8.380

Leak monitoring system

s

Locating the leak inner and outer pipe

Procedur

e

Leak monitorin

g

Flammable or water-hazardous

fluids are transported through

the inner medium pipe of a double-walled pipe system. The

outer containment pipe prevents uncontrolled spillage of th

e

dangerous transport medium if leaks occur. Approved leak

detectors can be connected to the surveillance space between

the inner and outer pipes for permanent leak monitoring with

vacuum or positive pressure principle. The leak detectors reg

-

ulate the monitoring pressure in the surveillance space of the

double-walled safety pipe and register any pressure changes

when either the inner or outer pipe is damaged. When damage

occurs, the leak detector gives an acoustic or optical alarm

signal which can be transmitted over long distances via poten-

tial-free relay contacts.

Locating the lea

k

If the alarm is given, first of all a check should be carried out

on all easily accessible and visible parts of the piping such as

the leak detector, connection pipes and test valves at the end

connections. The next step is to examine the weld or solder

seams or the threaded/couples end connections of the visibl

e

connection fittings (inner/outer pipe).

If the leak has still not been found, the piping itself needs to

be checked. It is recommended to detach all connections to

further piping above ground, to install blank

flanges at both

ends and to mount a manometer for the inner pipe at one end

.

After that, the surveillance space should be pressurized and

checked whether the pressure leaks out into the inner pipe or

into the environment

.

The leak detector and the connection pipe

s

Untightness in the leak detector or in the connection pipes ca

n

be easily detected by means of a pressure test and sprayin

g

on bubble-forming fluid

.

Leaks in the outer pip

e

If the outer pipe is damaged it is recommended to check

whether earth-moving work has been carried out along th

e

piping route. The majority of outer pipe damage is caused b

y

mechanical impact from outside (e.g. by mechanical excava-

tors). For this reason it makes sense to check for damage t

o

the outer pipes

first in such areas.

If the leak cannot be found in this way, the surveillance spac

e

between inner and outer pipe can be can be

filled with a read-

ily volatile gas, e.g. helium, to locate the leak. The gas escapes

through the leak and rises to the surface, where it can be

detected by using a gas detector. If the pipe route runs under

-

neath a concrete or asphalt surface, holes can be drilled abov

e

the route at intervals of 1 m to 2 m

.

Leaks in the inner pipe

One of the options for locating a leak in the inner pipe is th

e

ultrasonic method. Nitrogen, which is filled in the surveil

-

lance space, enters the inner pipe through the leak, causing

a

flow noise. An ultrasound sensor which then is pulled slowly

through the inner pipe registers this noise and reports it to

a

display unit. The leak can be located by reading off the metre

indication on the pulling wire of the sensor, it can then b

e

determined how far along the pipe from the end the leak i

s

located

.

31.03.2026 Subject to technical changes. Page 39