Spring energised Valve seals
In sealing systems for valves where soft packing materials are used, the initial compression on the packing decreases as a function of time and load.
The causes for this are in most cases:
Setting phenomena during operation
Reduction in sealing material volume as a result of wear
Ageing of the sealing material
Influences from equipment operation, like pressure and temperature changes
Elasticity through spring-loaded elements
Since the sealing materials do not have enough self-elasticity for compensation of volume losses, additional elastic elements in the form of spring discs are inserted for minimization of the loss of volume and compression so that inadmissible leakage rates are prevented.
The loss in sealing material volume caused by setting, material discharge through wear and ageing will be compensated by follow-up pressing of counter-sealing faces through spring packs so that the actually existing sealing pressure is always higher than the sealing pressure required as minimum. The spring colums are selected for the admissible drop of force across a specified spring path.
Limit values for leakage
Sealing systems with spring energising packs serve to ensure long-term tightness of sealing joints. The leakage limit values have been verified under test conditions. The following leak rates are admissible according to the German codes and standard TA-Luft.
In our opinion a TA-Luft certified packing for a valve is not sufficient as volume loss through wear will still occur and therefore leakage after while. Only when sufficient compression on the packing througout its life is available , the system can be called a TA-Luft system. The continious compression will be guaranteed by the addtional spring compression by our spring energised spring colums and can be substantiated by a calculation.