API TR 17TR11-2015 pdf download.Pressure Effects on Subsea Hardware During Flowline Pressure Testing in Deep Water.
1 Scope This document provides guidance to the industry on allowable pressure loading of subsea hardware components that can occur during hydrotesting of subsea flowlines and risers and during pre-commissioning leak testing of these systems. There are potential problems with confusion arising from high hydrostatic pressure in deep water, partially due to the variety of applicable test specifications and partly from the inconsistent use of a variety of acronyms for pressure terminology. With guidance, owner/operators can avoid unexpected loading conditions and the resulting potential for equipment damage, failure, or leakage (either immediate or delayed leaks) or reduced service life. This document and the examples provided give the user guidance for evaluating subsea hydrotesting scenarios where test pressures are often well above maximum allowable operating pressure (MAOP). 2 Normative References The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. API Technical Report 17TR8, High-pressure High-temperature Design Guidelines API Technical Report 17TR12, Consideration of External Pressure in the Design and Pressure Rating of Subsea Equipment 3 Terms, Definitions, Acronyms, and Abbreviations 3.1 Terms and Definitions For the purposes of this document, the following definitions apply. 3.1.1 absolute pressure Absolute pressure inside the components being tested, measured in “psia.” 3.1.2 barrier Element forming part of a pressure-containing envelope that is designed to prevent unintentional flow of produced/ injected fluids, particularly to the external environment.
3.1.4 external pressure External pressure acting on the subsea equipment due to the ambient seawater pressure at the submerged depth of the equipment being tested (Po). 3.1.5 gauge pressure Pressure gauge reading (assuming gauge is referenced to ambient pressure at the subsea depth); for example the differential between the absolute pressure inside the component being tested subsea and the external ambient pressure at the submerged depth, measured in “psig.” 3.1.6 maximum allowable operating pressure MAOP The single absolute pressure rating assigned, by U.S. regulator, to a flowline system including topsides to seabed limits. NOTE 1 MAOP may be the maximum pressure determined by design of a critical section or component pressure rating. NOTE 2 MAOP may also be the lowest design pressure of the maximum design pressures of all pipeline sections and components. 3.1.7 rated working pressure RWP Maximum internal pressure a piece of equipment is designed to contain and/or control. NOTE 1 For the purposes of this technical report, rated working pressure is defined as the absolute internal pressure minus 14.7 psia (see API 6A and API 17D). NOTE 2 Typically applies to valves, flanges, hubs, OECs, fittings, etc. 3.1.8 rated working pressure, absolute RWPa Manufacturer’s rated working pressure rating for the component, expressed in absolute pressure of fluid inside the component (psia). NOTE For the purpose of this technical report, the term RWPa means the manufacturer’s rated working pressure, measured in “psia.” 3.1.9 rated working pressure, differential RWPd For valve bore sealing elements, the maximum allowable differential pressure across the closed valve (applies to both testing and operations). NOTE When conducting typical factory acceptance testing ( FAT) and fabrication facility pressure tests on land, RWPd is essentially equal to RWPa for practical purposes.
4 Limitations on Subsea Testing Pressures 4.1 General In this section, a number of examples are described and illustrated for possible scenarios that can occur while pressure testing a flowline and riser. These scenarios, plus any additional testing requirements that might be required or desired, should be discussed at the design review phase between client and manufacturer so that the proper equipment selection and testing procedures can be confirmed. These examples show how subsea hardware components can be subjected to pressures well above the manufacturer’s rated working pressure (RWP), even when the RWP of these components appears to exceed the pressure required for the subsea flowline system test, normally 1.25 × MAOP. It is important to note that the API RWP for the components is “absolute pressure” (psia) of the fluid contained within the equipment, and not the differential pressure between internal pressure and external ambient seawater pressure (psid). In this document, the term RWPa is to mean the manufacturer’s rated working pressure, measured in “psia.” This document is applicable to API 17D, Second Edition. Additional considerations should be made for equipment designed to the following. 1) API 17TR8, relating to FAT hydrostatic test pressures: a) 1.5 × RWP for API RWP ≤ 20,000 psi; b) 1.25 × RWP for API RWP > 20,000 psi.