American Petroleum Institute

Technical Report on Performance of  and ANSI End Connections in a Fire Test According to  Specification 6FA - Third Edition
 N TR 6F1

Annotation

1 Scope and Applicability

The sizes of interest are shown in Table 1. The ANSI (8) sizes are adopted by API Spec 6D. The API sizes refer to those in API Spec 6A.

Table 2 shows the materials and gasket types which have been studied. As can be seen, there are a large number of sizes and combinations of materials and gaskets.

One very important point is that this Technical Report, and the research projects which preceded it, are based on the fire test procedure in API Spec 6FA. Whether or not API Spec 6FA adequately defines a "true" fire is totally outside the scope of this bulletin. The test simulates a closed condition with no flow through the connection. If there were flow through the connector, the heat transfer response would likely be different. Also, the external loads from dead weight, piping system thermal expansion, wind, etc., could significantly affect a joint's performance in a fire. These effects could be included in the design procedures reported herein, but they are not in the scope of this report.

1.1 EFFECTS OF FIRE ENVIRONMENT

Exposure to a fire environment around a flanged or clamped joint will tend to reduce the joint preload required for many seals to function. In a flanged joint, the flange exterior and bolts will heat up quicker than the seal and interior flange portion. This thermal gradient across the joint will cause preload to be lost. If enough preload is lost, the seal may unseat and leak; lose the contact pressure necessary to maintain a seal; fail if the seal is not strong enough to carry pressure load without the restraint from the adjacent contact surfaces, or fail if the temperature capacity of the seal material is exceeded.