Sealing systems operational behaviour

Mechanical and environmental performance
of Wolf GmbH inflatable sealing systems


Advantages of our air-filled sealing systems

  • Long service lifetime due to the extremely
    low leak rate (diffusion) of the sealing cushion
  • Patented CO2-neutral inflation technology; the cushion
    is inflated with air to protect the environment
  • Reusable cushion types (i.e. all sealing systems with valves and
    tyre valve connections (SSB2)) reduce maintenance costs, thanks
    to savings on material costs when retrofitting cables
  • Valve sealing systems allow filling-pressure monitoring
    and pressure can be topped up if necessary
  • Suitable for temperature range:
    -15°C to +30°C (+45°C (4 h))  PI 19.1 | 19.2 | 19.3 | 19.4 | 20.3 | 20.6

Calculation of service lifetime

  1. Computational determination of service lifetime

    The values for service lifetime are based on the total leak rate (diffusion) values measured by the GEMTEC testing institute and the results of ageing tests carried out in the Fibre Optics CT GmbH testing lab.

Extract from the GEMTEC test report

(full report available on request)

1.1 “Determination of the total leak rate of sealing elements”


Test setup:

The test sample was laid in a plastic duct supplied by the customer
and filled with the test gas (100 % SF6) at a pressure of 2.8 bar (abs.).

Swelling Sealing Bags SSB/SSB2
Samples A and B. After pressure-filling, the filling tube was crimped with the original crimping tool in accordance with the instructions provided.


Sealing cushion with valve
After pressure-filling, sample D was stored alternately with and without the valve end cap. (Note: The installation instruction state explicitly that the end cap should be used !)

Test procedure:

The sample was laid in the testing chamber, which was then evacuated to a pressure of 17 hPa. The background concentration of the test gas (SF6) was determined, followed by a waiting period of 30 seconds before the second measurement was carried out. The change in concentration is a clear indication of the total leak rate of the sample. The testing chamber has a volume of 13 litres. An LTS 311 V, S/N: 05107 was used. The simulation apparatus was calibrated with a pulse leak module.


Measurement of the total leak rate:

Types SSB/SSB2:

  1. Total leak rate directly after inflation of the sample (< 10 min)
  2. Total leak rate after 25 h

         Measured result: (average of 4 single measurements)


 Measurement No. 1
 L [mbarl/s]

 Measurement No. 2
 L [mbarl/s]


 < 2,3 x 10-8

 < 2,3 x 10-8


 < 2,3 x 10-8

 < 2,3 x 10-8

The total leak rate for samples A and B was below the detection limit:
L = 2,5 x 10-8 mbarl/s (corresponding to 0.73 mbarl/ year)

Calculation of the service lifetime

Test procedure:

Sealing systems with valve (V):

  1. Total leak rate directly after inflation of the sample (< 10 min).
    There was no end cap (AK) on the valve.
  2. Total leak rate directly after inflation of the sample (< 30 min).
    The valve was closed with the supplied end cap beforehand.
  3. Total leak rate after a waiting period of 24 h.
    The valve was closed with an end cap during this time.
  4. Total leak rate after a waiting period of 25 h,
    after the end cap had been removed.
  5. Total leak rate after a waiting period of 12 days.
    The valve was closed with an end cap during this time.
  6. Total leak rate after a waiting period of 12 days,
    after the valve had been removed.

Measurement results: (Average of 4 single measurements)



 No. 1
 L [mbarl/s]

 No. 2
 L [mbarl/s]

 No. 3
 L [mbarl/s]

 No. 4
 L [mbarl/s]

 No. 5
 L [mbarl/s]

 No. 6
 L [mbarl/s

 Measured after

 < 10 min.

 < 30 min

 24 h

 25 h

 12 d

 12 d

 Sample stored

 without AK

 with AK

 with AK

 without AK

 with AK

 without AK


 3,8 x 10-6

 2,3 x 10-8

 2,3 x 10-8

 5,2 x 10-6

 < 2,3 x 10-8

 4,9 x 10-6

With the end cap (as required by the installation instructions), 
the leak rate was as follows 
Sample D:    L = < 2,3 x 10-8 mbarl/s    (corresponding to:    0.73 mbarl/year)

without end cap:    (Note: These values clearly indicate the importance of the end cap)
Sample D:    L = 4,9 x 10-6 mbarl/s    (corresponding to:  155 mbarl/year)

without AK (end cap)


with AK (end cap)


Calculation of the service lifetime

1.2   Computational determination of service lifetime of air-filled sealing elements


Relevant factors:

  1. Total leak rate (rate of diffusions)
  2. Filling pressure p
  3. Filling volume V (in relation to the cushion size and cable configuration)
  4. Min. filling pressure required for an effective seal of 5 m water column
    (= 1 bar (value for practical test))


 Wolf GmbH

 (current state
 of technology)

 product CO2


 QADK/V (valve)

 with valve end cap


 * <2.3 x10-8

 * <2.3 x10-8

 ≤4,4 x10-6

 ≤ 6,5 x10-6






*Measurements Gemtec 10/2016

Table 2:

Computational determination of service lifetime of
inflatable cable seals for duct ID 105 mm
Requirements: "Tightness 5 m water column"

Sealing cushion   type L100:
Uninflated           length l: 33,0 cm
                            height h: 13,5 cm






 Sealing cushion filling quantity
 at filling pressue p

 Calculation of lifetime T

 Wolf Kabeltechnik


 SSB2 100






 Inflatable length


 Resulting height


 Resulting width


 On installa-

 Min. require-


 Leak rate L (mbarl/year)







 T = ∆p/ L


















 > 20















































Calculation of service lifetime

3.    Calculation of service lifetime: the environmental "ageing" test
 based on DIN EN 60794-1-22 and DIN EN 60794-1-21


This test is carried out on cable-sealing cushions that are intended to seal annular spaces against penetration by water or gas by means of internal pressure.
In order to calculate the service lifetime of the seal, its resistance to compressed air under operational conditions is determined.

2.1    Temperature cycling IEC 60794-1-22/F1
         Fibre Optics CT test protocoll No. 094/2016

Test setup
Configuration of the cable duct used in the test


Testing chamber:

Requirements Lowest temperature  TA -15°C
                       Highest temperature  TB +30°C
                       Min. dwell time         4 h
                       No. of cycles             20


096 /2016

Tightness of the sealing system

Tightness of the sealing system combination under stress caused by heat and overpressure

In the following test method No. 1, the tightness of the QADE/V and QADE/V L sealing cushions with valves was verified under temperature stress. Fluctuation in the surrounding temperature has an effect on the filling pressure inside the sealing cushion. If it is cold, the inner filling pressure sinks. The object of the test is to verify whether tightness remains unimpaired despite tempera-ture changes within the specified temperature range.

In addition, with test No. 1 it was possible to verify the application-specific need for overpressure in the cable conduit to be able to escape through the swelling material without affecting water-tightness. In the case of cable conduits equipped with sealing systems against pressing water at both ends, the sealing systems have been known to shift position or even be forced out.

Test 1:
Sealing cushion filling pressure 2,8 bar.
Sample is positioned horizontally,
water column ~ 1-2 cm


Test 2:
Sealing cushion filling pressure 2,8 bar.
Sample is positioned vertically,
water column ~ 3-4 cm


The filling pressure of the sealing cushion changes during temperature cycling from an initial value of 2.8 bar as follows:

  • At highest temperature +45°C → filling pressure max 3.0 bar
  • At lowest temperature   -15°C → filling pressure 2.2 bar

…/ Results of field testing "Tightness of the sealing system combination“

In calculating the length of service lifetime, test method No. 2 investigates what max. possible loss of pressure there may be without the tightness of the QADE/VR and QADE/V L seal against pressing water being affected. To this end, the filling pressure of the sealing cushion in the test is reduced step by step to a residual pressure of 1.0 bar.


Test results:

Test method No. 1:        Requirements V (1) fulfilled

On exposure to heat, 0.35 bar overpressure air can escape from the swelling sealing system.
This pevents sealing cushions from being pushed out of the duct.


Test method No. 2:        Requirements V (2) fulfilled

  • 5 m water column for ˃ 2 days: passed
  • Long-term performance of the seal: passed

Leak rate of cushion filling pressure: 2.8 to 1.0 bar ≥ 4 m water column

Fibre Optics CT GmbH testing method

for sealing-cushion pressure filling:

* The sealing system 20.6 QADE/VL 100 was soaked in water for a short period (approx. 20 min)
   by turning the sample through 180°. There was subsequently no pressure on the sealing system!
   The requirement "Tightness against gas diffusion and 5 m water column" was thus fulfilled.
   The specified requirement for gas diffusion stipulated by the German Gas and Water Association
   DVGW-VP601: is < 0.1 bar.

Wolf GmbH

Zazenhäuser Straße 52
D - 70437 Stuttgart

Tel.:  +49 (0)711 87 39 41
Fax.: +49 (0)711 87 12 30

Email: Service(at)