Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Study on Subsea Hot-tap Protection Frame DesignFengyun Wang1, Sheng Yang2, Chenlei Cao2, Hao Yang1
Offshore Oil Engineering Co. Ltd., Tanggu, Tianjin, China1
Offshore Oil Engineering Co. Ltd., Nanshan, Shenzhen, China2

ABSTRACTin any case, a protection frame is very useful for the security of hot-tapregion.

A protection frame is urgently needed by subsea hot-tap tee and its
control valve in shallow water subsea engineering to against the fishinggear and dropped object. And the hot-tap protection frame can also be
used as an installation assistant for the hot-tapping tool orientation andoperation. Control valve observation and operation is easier for diver or
ROV outside the protection frame. This paper presents the design
consideration of subsea hot-tap protection frame and indicates someproblem during fabrication, transportation and installation. A typicaldesign example is also be demonstrated in this paper.

Convenient for hot-tapping operation and the new pipeline accessing, aT-shape trench should be dug in advance. But the trench will makemore difficult for protection frame design and installation. And it also
brings a lot of consequences for the determination of hot-tapping
location and the support for the control valves on new pipeline. So thesubsea hot-tap protection frame needs to have the auxiliary functions
such as assistance for hot-tap tool lowering and positioning, control
valve support, etc.

KEY WORDS: hot-tap; protection frame; shallow water; distributed
mudmats; T-shaped trench; fishing-gear; dropped-objects.

This paper presents the general methodology of subsea hot-tap
protection frame and the special functional components design is also
be demonstrated.

FOUNCTION OF SUBSEA HOT-TAP PROTECTIONFRAMENOMENCLATURE
DFP = Dropped-Objects and Fishing-Gear Protection
OD = Outer Diameter

Hot-tapping Procedure

INTRODUCTION

Hot-tapping technology can only be used in shallow water pipeline atpresent because it is difficult for ROV to precede the hot-tapping
procedure.

Hot-tapping technology is widely used in technical transformation at acertain position of pipeline during production process. In case ofleakage, blockage and corrosion of the pipeline, hot-tapping on pipeline
is necessary to add auxiliary lines to maintain production and replace
the faulty pipe section.

Hot-tap procedure is listed as following:In recent years, with the continuous increase of drilling and production
capacity, the scale of subsea pipeline network is increasing day by day.
Through comparison, it found that hot-tapping is the most economical
choice for connecting the new pipeline to the old one. To facilitate precommissioning of new pipeline, control valves on it are necessary.
According to ISO 13628-15, for subsea equipment in depths less than750m, the influence of fishing gear and dropped object should beconsidered. And for equipment in depths below 750m, normally
accepted as guideline-less, bottom trawling is less common. For
locations where it can be documented that no bottom trawling occurs,
and is not likely to occur within the design life of the installations, theequipment need only be protected against dropped objects. Therefore,1863Excavation around the existing pipeline and the location which
new pipeline will be installed, a T-shaped trench is necessary for
hot-tapping operation
Removing the concrete coating of existing pipeline
Landing the hot-tapping protection frame (with no cover)Landing the hot-tap tee, valve and operation tools (see Fig.1)
After hot-tapping, retrieving hot-tapping tools and then landing
hot-tapping plugging valve (see Fig.2)
Backfilling with sand bags in T trenchLanding the cover of protection frame