Additional considerations when selecting a gasket material may include:
- Fire safe capability - There is no standard for "fire safe" gasket materials. However, Durlon® 8500 passed a modified API 607 fire test that was done by an independent lab.
- API Spec 6BF, Fire Test for End Connections, and API Bulletins, 6F1 and 6F2, do discuss fire testing but for metal gaskets and API rings, not soft gasket material.
- Gasket design factors - The m and y values established by ASME and the newer design factors being developed by the PVRC for fugitive emissions, are additional considerations. The m and y values do not take fugitive emissions into account whereas the newer tightness parameters (Tp) do.
These gasket factors recognize that all joints leak to some extent. Therefore, an acceptable level of leakage is defined. A leak rate of 1/2480 lb/hr per inch of OD has been defined as a "standard" acceptable leak rate and is known as T2.
Tp classes and their associated leak rates are as follows:
- T1 - Economy - 1/25 lb/hr per inch of OD
- T2 - Standard - 1/2480 lb/hr per inch of OD
- T3 - Tight - 1/248,000 lb/hr per inch of OD
Torque values for Durlon® products are calculated using a tightness parameter of T3.