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Hot tapping of C02 Pipelines leaks during Carbon transport in pipelines

Context

Pipelines are used to transport volumes of fluids from the field or production facilities to distribution centers and ultimate consumers. A leak could occur due to corrosion, aging, or human activities on these. Such could to adverse environmental and human impact.

Definition

Hot tapping is a procedure used to make a new pipeline connection while the pipeline remains in service, flowing natural gas under pressure. The hot tap procedure involves attaching a branch connection and valve on the outside of an operating pipeline, and then cutting out the pipeline wall within the branch, removing the wall section through the valve, and closing the valve for future connection. Hot tapping allows an operator to make a new connection without having to shut down the pipeline or vent gas to the atmosphere. This practice allows for uninterrupted service to customers, as well as reduced emissions of methane. Hot tapping is an alternative to “pipeline blowdowns” which entails shutting down a portion of the system and purging the line of gas before beginning any work.1

Applicability

Hot taps can be vertical, horizontal, or at any radial angle around the pipe if there is sufficient room to install the valve, fitting, and tapping machine. Current technology allows for taps on all types of pipelines; at all pressures, diameters, and compositions; and even older pipes merge with new ones. Lightweight tapping machines are also available that allow a small hot tap to be performed by a single operator, without additional blocking or bracing. Hot taps can be vertical, horizontal, or at any angle around the pipe if there is sufficient room to install the valve, fitting, and tapping machine. Current technology allows for taps on all types of pipelines, at all pressures, diameters, and compositions, even older pipes merging with new ones. New, lightweight tapping machines are also available that allow a hot tap to be performed by a single operator, without additional blocking or bracing. In swampy terrain, cofferdams are temporary structures that can used to create dry work areas in wet environments using various technology including sheet piling that can be used for multiple purposes including dewatering, diversion, and damming.1

Preparing for Hot Tap And Stoppling

In preparation for a hot tap project, operators will need to determine the maximum operating pressure (during welding of a fitting and the hot tap), type of pipe material (i.e., steel, cast iron, plastic), and condition of the parent pipeline (internal/external corrosion, wall thickness) to ensure a safe project. A hot tap connection can be made on a pipeline only where the parent pipe material is in good condition. Other conditions to evaluate include the flow of fluid in the pipeline to carry away the heat of welding, the location of nearby valves for emergency isolation in the event of an accident, the desired tap diameter, working space around the connection, location of other pipeline welds, and imperfections or obstructions. Operators should also determine if the line is “looped,” as many gas transmission companies avoid operational disruptions by shifting the load to a parallel line. Developing and following a written plan is advisable to ensure full and proper evaluation of a future connection. 1

CO2 pipelines differ from oil and gas pipelines primarily due to the state in which CO2 is transported (as a supercritical fluid), which requires higher pressures and thicker pipeline walls compared to natural gas pipelines. A minimum consideration for CO2 pipeline design should include determining the physical properties of the flowing fluid, optimal pipeline sizes, specification of operating pressures of the pipeline, adequate knowledge of the topography of the pipeline route, geotechnical considerations, and the local environment 4

The primary equipment for a typical hot tap application includes a drilling machine, a branch fitting, and a valve. Exhibit 1 shares on the overall structure of the Hot-tapping equipment

a) Fitting: the connection to the existing pipe is made within a fitting, which can be a simple welded nipple for a small (e.g., one inch) connection to a larger pipeline, or a full-encirclement split-sleeve tee for extra support when the branch is the same size as the parent pipeline. The tee wraps completely around the pipeline, and when welded, provides mechanical reinforcement of the branch and carrier pipe.

b) Drilling machine: the drilling machine generally consists of a mechanically driven telescoping boring bar that controls a cutting tool. The cutting tool is used to bore a pilot hole into the pipeline wall to centre a hole saw that cuts out the “coupon,” or curved section of pipeline wall. The pilot drill includes a “catch” to withdraw the cut-out pipe wall (coupon) and withdraw it past the valve.

c) Valve: the valve on a hot tap connection (a sandwich valve) must allow the coupon (the section of pipeline wall cut out by the drilling machine) to be removed after the cutting operation. Suitable valve types include ball or gate valves, but not plug or butterfly1

Below is a schematic arrangement of the tapping machine on the pipeline. 3

Source: U.S. Environmental Protection Agency. 5

Operation of the tapping machine

Exhibit 2 provides a general schematic of a hot tapping procedure and below are basic steps to perform a hot tap are:

1. Connect the fitting on the existing pipeline by welding (steel), bolting (cast iron), or bonding (plastic) and install the valve.

2. Install the hot tap machine through the permanent valve.

3. Perform the hot tap by cutting the coupon from the pipeline through the open valve. A special device retains the “coupon” for removal after the hot tap operation. Withdraw the coupon through the valve and close the valve.

4. Remove the tapping machine and add the branch pipeline. Purge oxygen, open the valve, and the new connection is put into service.

Source:https://edarikahiki.wordpress.com/wp-content/uploads/2013/02/screen-shot-2013-02-04-at-7-10-17-pm.png Other sources for videos: See the attached URL for a video on tapping. TD Williamson example

Economic and Environmental Benefits

Economic and Environmental Benefits Key economic and environmental benefits of employing hot-tapping procedures instead of shutdown connections include:

a. Continuous system operation—shutdown and service interruptions are avoided.

b. No gas is released to the atmosphere.

c. Avoided cutting, realignment, and re-welding of pipeline sections.

d. Reduction of costs associated with planning and coordination—meetings, schedules, paperwork, lost production, and direct manpower.

e. Increased worker safety.

f. Elimination of obligations to notify customers of gas outages.

g. Reduce service interruptions - Allows for continuous system operation by avoiding shutdowns.

h. Maintain pipeline structural integrity - Avoids cutting, realignment, and re-welding of pipeline “T” sections.

Local Community Impact

The Denbury CO2 pipeline leaks in Mississippi and Louisiana caused significant suffering and disruption to local communities such as health and livelihood disruption.

Health Effects • In the 2020 Satartia, Mississippi incident, 45 people were taken to the hospital due to CO2 exposure • Symptoms of CO2 exposure included headaches, drowsiness, rapid breathing, confusion, increased cardiac output, elevated blood pressure, and arrhythmias • At extreme concentrations, CO2 exposure can lead to death by asphyxiation

Livelihood Disruption • Approximately 300 residents were evacuated during the Satartia incident • Residents experienced vehicle engine issues due to the CO2 cloud • Some individuals passed out or required emergency assistance to evacuate 6

Explanatory Notes. This Wikipedia write-up only covers Hot Tap for horizontal fluid flow related to oil, gas, and C02. It does not cover vertical wells or other storage equipment.

<ref>1U.S. Environmental Protection Agency. "Pipeline Hot Taps." Last modified July 9, 2024. https://www.epa.gov/natural-gas-star-program/pipeline-hot-taps. 2 https://www.ecfr.gov/current/title-49/section-192.151 3 Edarikahiki. "Pipeline Hot Tap." Edarikahiki's Blog (blog), February 4, 2013. https://edarikahiki.wordpress.com/2013/02/04/pipeline-hot-tap/. 4 Witkowski, Andrzej, Maciej Majkut, and Stanisław Rulik. "CO2 Pipeline Design: A Review." Energies 11, no. 9 (2018): 2184. https://doi.org/10.3390/en11092184. TDW Williams. (n.d.). Safe, Efficient Pipeline Hot Tapping: Perform Repairs and Maintenance Without Disrupting Service. Retrieved from https://www.tdwilliamson.com/resources/papers/safe-efficient-pipeline-hot-tapping 5 U.S. Environmental Protection Agency. "Using Hot Taps For In Service Pipeline Connections." Natural Gas STAR Program, June 2016. https://19january2017snapshot.epa.gov/sites/production/files/2016-06/documents/ll_hottaps.pdf. 6 Pipeline Safety Trust. "Denbury Pipeline Company Responsible for 2020 Carbon Dioxide Pipeline Rupture in Satartia, MS, Leaks CO2 Again, This Time in Sulphur, LA." April 5, 2024. https://pstrust.org/denbury-pipeline-company-responsible-for-2020-carbon-dioxide-pipeline-rupture-in-satartia-ms-leaks-co2-again-this-time-in-sulphur-la/.