API RP 14B:2005 pdf download.Design, Installation, Repair and Operation of Subsurface Safety Valve Systems
5.2 System requirements
5.2.1 General
The user/purchaser, when developing the system configuration, shall consider all the pertinent elements and their compatibility. These elements shall include the following: control system, control line, wellhead/tubing hanger passages and connectors, control line protectors, control fluid (for SCSSV); SSSV; flow couplings; locking and sealing devices (for wireline safety valves); safety-valve landing nipples; related tools and exposed fluids.
5.2.2 Installation
5.2.2.1 General
The user/purchaser shall assure that installation and installation testing of the SSSV system is performed and approved by qualified personnel using documented procedures and acceptance criteria in accordance with the manufacturer’s operating manual and operator’s system integration manual. System configuration and installation testing results shall become a part of the well records (see 5.4).
5.2.2.2 Control system
The surface-control system shall include the elements necessary to sense abnormal conditions that may contribute to uncontrolled well flow and shall transmit the necessary signal to the SCSSV for closure. All elements of the integrated system shall be analysed for potential hazards that may render the system vulnerable to failure or may preclude safe use. For example, automatic resets shall not be incorporated in the control system since this feature may cause the SCSSV to reopen when it should remain closed. Systems shall be designed and operated to address the potential hazards to safe use. It is desirable to integrate the SCSSV surface-control system into the surface safety system to avoid duplication. Features shall be designed in the integrated system whereby routine production upsets do not result in closure of the SCSSV(s). If hydraulic or pneumatic control systems are utilized, the test pressure of those systems shall be equal to or greater than the highest operating pressure of that system when installed. System components shall be verified capable of meeting all anticipated environmental conditions, including temperature. For multiple-well installations, the control-system manifolding shall include provisions for individual well and SSSV isolation. ESD controls should be installed in strategic locations in accordance with applicable regulations and sound engineering judgement. To avoid closure of the SCSSV under full well-flow conditions, a delay shall be incorporated between closure of the tree valves controlled by the ESD and the downhole SCSSV. The opening sequence should be reversed on returning production facilities to normal operations. This delay mechanism shall be carefully analysed and documented to verify that it does not create additional hazards that render the system vulnerable to failure. For additional information, see ISO 13628-6.