Differenices between ISO 15848 and TA-Luft
September 6th, 2017 by Amanda Schumann
TA-Luft only deals with stem sealing area. Also, no third party witness is needed.
The TA-Luft test qualifies only a “high-quality sealing system”. TA-Luft is considered to be complied with if metal bellows with a safety energised packing or similar sealing systems are used; as per VDI 2440.
TA-Luft does not specify the number of mechanical cycles nor the number of thermal cycles.
Many valve manufacturers like to publish the TA-Luft logo but it often only means the seals themselves they use were TA-Luft certified! Simply using “TA-Luft packings” does not ensure long-term leak tightness. Many other factors play a role in sealing system, such as the stem surface finish and the tolerances dimensions between the gland and the stem.
ISO 15848 is much more stringent.
ISO 15848 “Measurement, test and qualification procedures for fugitive emissions” the complete valve, and all seals, requires type testing.
The requirements of the type tests are very detailed: –
1: A distinction is made here between three tightness classes, namely A, B and C (Class A having the lowest environmental leakage).
2: Leakage is tested at room temperature without mechanical effects (helium leak detection test). Pressure, temperature, endurance & tightness parameters must be met.