When pipes are connected and used to convey high-pressure fluid, over time, they experience wear and tear. Sometimes, the fluid that is being conveyed may react with the pipelines, causing corrosion or mechanical damage. The continuous use of such pipes will cause serious environmental hazards, hence, the need for hot tapping pipeline services.
What is Hot Tapping?
It is a technique that helps to connect a different pipe to an already established piping system when it is in operation. It creates an opening on the pipe by cutting or drilling. Although the technique is mostly used in pipes, you can also use it to attach nozzles to storage tanks and pressure vessels.
Additionally, it allows you to attach connections without disrupting or depressurizing process operations. You can also use hot tapping services to connect pipes when you cannot conveniently use the pipes to convey hot substances. It enables you to isolate sections of pipes that require maintenance by either stoppling or plugging the line.
Furthermore, this technique is inherently dangerous and should only be used when you cannot practically remove an operating piping system. Precision is needed in testing, design, and inspection when specifying taps for pipes. This is important because you must be sure that the operation is carried out in a reliable and safe manner.
Therefore, you should only consider this technique after evaluating and rejecting other options. You must design each tap properly, thoroughly inspect the location, and review the procedures for installation.
How is Hot Tapping Done?
Below is a step-by-step guide on hot tapping.
- Set up the machine for tapping onto the pipes.
- Ensure the pilot/cutter assembly is touching the head pipe, and then commence the process.
- After the pilot has gone through the head pipe completely, stop the machine then allow the u-wires to fall off.
- Withdraw the cutter and coupon.
- Stop the flow of fluid between two consecutive locations of the tap, and then make another passage to maintain the normal flow in the piping system.
- Use a vent to drain out the fluid between both locations of the tap if the fluid is gaseous or use a drain if the fluid is liquid.
- Cut and weld to complete the alterations between both locations. The installation may involve another piece of pipe or a valve.
- Fill the tap sites with fluid and ensure to maintain the previous pressure.
- Remove the machine for tapping and allow the flow of fluid to begin from the head pipe and the newly added pipes.
Environmental and Economic Benefits of Hot Tapping
There are distinct environmental and economic benefits to carrying out this welding operation without removing pipes that are in service and venting greenhouse gases like methane. The key benefits of using this procedure rather than shutting down the entire connections are:
- Continuous operation of the piping system, thereby, avoiding service interruptions and shutdown.
- No harmful gas releases into the atmosphere.
- There is no need to cut, realign, and re-weld any section of the pipeline.
- Reduction in the costs of planning and coordinating activities such as direct manpower, lost production, paperwork, schedules, and meetings.
- Increase in the safety of workers.
- No obligation to inform clients about gas outages.
When you follow best practices, the time needed to carry out the procedure and the risk of failure reduces drastically.
When You Should Not Use Hot Taps
Problems may arise when using hot taps particularly when there is a risk of burning through the pipes instead of cutting through them. Also, the product flowing in the pipes may experience unstable decomposition, and there is a risk of cracking hydrogen.
A burn-through may occur when you weld a pressurized pipe. In this case, the un-melted site under the welding pool isn’t capable of containing the pipe’s internal pressure. To prevent this, you need to take special measures to ensure that the temperature inside the pipe’s wall does not exceed a critical level. This critical level depends on the type of product flowing in the pipe.
Furthermore, the probability of cracking hydrogen increases during hot tapping compared to other situations that involve welding. This is because the product flowing in the pipes increases the risk of developing hard microstructures, thereby, increasing the potential of cracking hydrogen.
You can reduce the risk of cracking by using electrodes with low hydrogen and carefully selecting your heat input. Sometimes, it may be possible to control the initial heat, but the approach becomes inefficient because of the cooling ability of the conveyed products. The deposition sequences of temper bead may be utilized in hardness control.
Generally, the conditions that do not require hot tapping are:
- Stainless steel pipes conveying catacarb solution.
- Montel pipes conveying sulfur compounds.
- Airlines that do not provide the assurance of a lack of hydrocarbon.
- Piping containing chlorine or pure oxygen.
- Piping conveying caustic soda.
- Piping containing peroxides, chlorides, acids, or other substances that may become hazardous or decompose due to the heat from welding. Examples are acetylene and sulfuric acid.
- Piping conveying a flammable or combustible mixture.
How to Assess the Economics of Hot Taps
The steps to assess the economics of hot taps are:
- Determine the physical condition of the already existing pipeline.
- Calculate the cost of shutting down the connection.
- Calculate the cost of performing hot tapping procedures.
- Evaluate the benefits of saving gas if you perform hot tapping.
- Weigh your options and determine if hot tapping is better.
Companies can devise safety measures for welding taps using qualified flow loops and computerized techniques for modeling heat flow. This approach involves matching and/or controlling the cooling ability of the pipeline using available measurement techniques. You can visit this website to learn more strategies to manage and mitigate the hazards of hot tapping.
Generally, pipelines undergo various transformations every year. Performing hot tapping procedures to make installations and connections is beneficial. It reduces the emission of methane gas from the pipelines and increases efficiency while saving costs.