The majority of mechanical equipment found in oil and gas facilities belongs to the static equipment group, which comprises pressure vessels (drums, columns, reactors, filters) and heat exchangers (shell and tubes, plate and frame, air coolers). The presented guidelines contain cost-effective recommendations for their design, materials, and fabrication. They aim to enable the project engineer, who is not an equipment specialist, to check that economical choices are made. The specification and selection of the equipment is the responsibility of the static equipment engineer, based on requirements specified by other disciplines, including process, materials and plant layout. These other disciplines are not always aware of the impact of their demands on the cost/lead time of the equipment. Conversely, the static equipment discipline is not always aware of where the requirements of these disciplines come from and if the onerous ones could be challenged. Such interface data are the focus of this article, which aims to give a cross-discipline awareness. Let's start with the review of the process equipment data sheet. The process engineer defines the design pressure by applying common and reasonable margins above the maximum operating pressure, as shown below. The design temperature is usually set 15-20 C above the maximum continuous operating temperature.