What is a weak peak?

The storage tank is designed with a weak roof structure so that in the event of an explosion of the flammable or explosive fluids contained within it, the roof of the tank collapses before the tank walls do. This allows the explosion pressure and the flammable fluids to escape upward, enabling most of the unburned fluids to remain inside the tank. Instead of the tank walls collapsing and the flammable fluids bursting out in all directions, which would instantly increase the severity of the disaster. Its purpose is to control disasters and reduce losses. This is mainly reflected at the junction of the tank roof and the tank wall, where weak connections are used; this generally does not affect the normal operation of the storage tank.

The last edit to this post was made by fzujunru on 2019-3-19 at 08:41. The connection between the tank top and the tank walls (the angle steel used for framing) must first meet the strength requirements under the design internal pressure. A weak roof is, from a safety perspective, the best option, but it’s difficult to achieve; the requirements for a weak roof are too stringent. According to GB50341, weak-roof connections are usually not feasible, and in such cases an emergency relief valve must be installed on the tank top

The tank top and tank wall are connected using a weak connection structure, which serves as a safety release mechanism in case of an accident. The tank top and tank wall are connected using a weak connection structure, which serves as a safety release mechanism in case of an accident. The main assumptions adopted in deriving the weak-top condition according to API 650 are as follows: the lifting force generated by internal pressure lifts the tank bottom to a critical state where it is no longer supported; when the compressive ring material reaches its yield strength of 220 MPa, plastic instability occurs at the weak connections, thereby allowing effective pressure release and protecting the tank. There will be a slight error when the actual yield strength of the compression ring material is not 220 MPa. The conditions for weak connection structures are formulated in accordance with the provisions of API 650. The GB50341-2014 tank code only specifies the requirements that a weak roof must meet, but it does not require the use of a weak roof structure. Whether the storage tank shall adopt a weak roof connection structure shall be determined by the owner, or as specified by other safety regulations. In GB50074, no explicit requirements are specified ； Clause 6.2.20 of GB50160 stipulates that the connection between the roof panel of a fixed-roof tank at normal pressure and the corner steel strips should adopt a weak-roof structure. Clause 6.2.20 in GB50160 corresponds to Clause 6.1.5 in SH3046. The emergency relief function for weak roofs only operates in the event of a fire outside the tank; it does not cover situations such as explosions inside the tank, chemical reactions, or overfilling that leads to roof failure.

To be honest, after designing storage tanks for so many years, I’ve never used a weak roof once