本技术报告阐述了与外部压力对安装在深水中用于容纳或控制井筒流体的水下设备的影响有关的问题。深水处的外部压力可以显著降低作用在水下设备壁上的压差，从而提高其内部承压能力。外部压力通常是环境海水压力，但在某些情况下，外部压力可能是由于钻井泥浆、完井液或立管或其他导管内包含的其他液体的静水压头造成的，这些导管将海底设备连接到地面设施。API技术报告17TR12为海底设备设计师/制造商提供了指导，以在设计和验证海底设备时正确考虑外部压力（或在某些情况下，压差）。 此外，本技术报告还为设备采购商/最终用户提供了指导，以适当选择其海底系统的额定设备，同时考虑外部压力和内部压力的影响，包括封闭机构的压差，以及在所有潜在操作场景和功能标准下施加的其他机械或结构荷载。本技术报告的使用者必须了解司法当局的法规，这些法规可能会对设备设计中的外部压力或压差考虑提出额外或不同的要求。

This technical report addresses issues related to the effects of external pressure acting on subsea equipment installed in deepwater for containing or controlling wellbore fluids. External pressure at deepwater can significantly reduce the differential pressure acting on the wall of subsea equipment, and therefore, this can improve its internal pressure containment capability. External pressure is typically ambient seawater pressure, but in some cases, external pressure may be due to the hydrostatic head of drilling mud, completion fluids, or other fluids contained within risers or other conduits that connect the subsea equipment to surface facilities.API Technical Report 17TR12 provides guidance for subsea equipment designers/manufacturers to properly account for external pressure (or in some cases, differential pressure) when designing and validating subsea equipment. Additionally, this technical report provides guidance to equipment purchaser/end-user to appropriately select rated equipment for their subsea systems with consideration to the effects of external pressure in addition to internal pressure, including differential pressure across a closure mechanism, and other applied mechanical or structural loads under all potential operating scenarios and functionality criteria.It is necessary that users of this technical report be aware of regulations from jurisdictional authority that may impose additional or different requirements to the consideration of external pressure or differential pressure in equipment designs.