API Std 650 mixed material tanks testing requirements

The cone slope of the completed API Std 650 mixed material tanks foundation is 15/1000 for the general foundation and less than 35/1000 for the soft foundation. After the foundation settlement of the storage tank is basically stable, the surface slope must be greater than eight thousandths. The edge of the tank bottom should be more than 0.3 meters higher than the surrounding ground. Above the ground, the tank bottom leakage detection tube should be drawn from the foundation sand cushion and cross the foundation ring wall or the slope protection surface. The circumferential distance should be less than 20 meters, and each API Std 650 mixed material tanks should have at least 4 detection tubes.

Preheating should be performed by heating and maintaining this heat in appreciable lengths of the joint to be welded, preferably using a strip burner with a mild flame rather than a harsh flame such as that from a cutting torch. Electrical strip heaters are available and have been found to be satisfactory. The preheat of 300°F should be checked with a temperature-sensitive crayon, or similarly accurate means, so that the steel 4 in. (or four times the API Std 650 mixed material tanks plate thickness, whichever is greater) on each side of the joint will be maintained at the minimum preheat temperature. Ring burners or heaters are recommended for nozzle and manway welds. At no time during the welding should the base metal fall below a temperature of 300°F.

According to API 650 tanks, anchoring devices should be designed to transfer overturning moments to the API Std 650 mixed material tanks tank foundation. At the same time, according to API 650 tank Appendix F, when the tank is to be anchored, the size of the anchoring parts is determined by the maximum lifting force caused by the internal pressure and wind load or the combination of internal pressure and seismic load.