A few client calls have been received recently related to the possible combined use of high pressure nitrogen tube bundles and liquefied cryogenic nitrogen as sources for higher volume testing requirements. The most specific application related to the use of high pressure nitrogen gas for high pressure purging and testing of pipelines. Nitrogen offers significant advantages for this application over water or air by providing an inert atmosphere with a very low dew point. Ie- It is dry, clean and reduces oxidation. As with any compressible medium, nitrogen has significant risks associated with it in the event of a pipe or component failure. It is therefore very important that high pressure gases only be used for testing by professionals with carefully reviewed and administered operational safety procedures.
The discussions related to testing or purging with pipeline pressure requirements at 1200-1800 psi. Total volume requirements ranged from 50,000 to 150,000 cubic feet of nitrogen. A conventional simple approach for these applications is to roll up with a high pressure (~3000psi) tube trailer and directly transfer nitrogen from the trailer to the pipeline. There is inefficiency here as only a certain percentage of the gas in the tubes will be available for the pipeline at the pressure needed. Cascading of the tubes increases the consumable gas from the tubes, but still leaves a significant residual.
Getting pressure up is directly related to the volume of molecules you can get into a space. One thought on pressurizing pipes is to use portable liquid nitrogen vessel (ex- 850 gallon GOrilla) to provide the initial low pressure mass of molecules into the pipe. Once the pipe is up from atmospheric pressure to the level that can be reached from the liquid source then tubes can be used to get to the required test pressure. The advantage of this approach is that each vessel source is used for what it actually does best. That is- Volume from the Liquid Vessel and Pressure from the Tubes.
Alternatively, for a project requiring multiple tube/liquid sources for a series of tests some added efficiency could possibly be achieved by adding a high pressure pumping system to the liquid source. The tubes could be used to provide fast flow and pressure to the pipeline. The portable liquid nitrogen vessel could be used to replenish the tubes between tests. It could also be used to discharge an initial volume of molecules into the pipeline. This approach could be advantageous in cases where it is more convenient and cost effective to deliver liquid to a site for refilling the portable cryogenic vessel than it is to swap out or refill tubes. There is also a good possibility that an 850 gallon GOrilla-type vessel with trailer, vaporizer pumping system and power source is less expensive that a tube trailer with comparable volume. Use of less expensive portable cryogenic vessels in place of high pressure tubes (where feasible) could allow more valuable assets to be used where they are required.
There is also the side benefit that the portable cryogenic vessel could be used for many other applications when not tied to high pressure testing and purging. The ability to keep capital invested in cryogenic vessels working for pipeline freezing, liquid delivery, welding purge, harvest, or high volume cutting applications warrants consideration. This is particularly true in the event that the highly versatile liquid and gas use vessel requires less capital investment, less ongoing testing/ recertification cost and provides more positive financial return than a set of tubes holding a comparable volume of nitrogen.
The discussions related to testing or purging with pipeline pressure requirements at 1200-1800 psi. Total volume requirements ranged from 50,000 to 150,000 cubic feet of nitrogen. A conventional simple approach for these applications is to roll up with a high pressure (~3000psi) tube trailer and directly transfer nitrogen from the trailer to the pipeline. There is inefficiency here as only a certain percentage of the gas in the tubes will be available for the pipeline at the pressure needed. Cascading of the tubes increases the consumable gas from the tubes, but still leaves a significant residual.
Getting pressure up is directly related to the volume of molecules you can get into a space. One thought on pressurizing pipes is to use portable liquid nitrogen vessel (ex- 850 gallon GOrilla) to provide the initial low pressure mass of molecules into the pipe. Once the pipe is up from atmospheric pressure to the level that can be reached from the liquid source then tubes can be used to get to the required test pressure. The advantage of this approach is that each vessel source is used for what it actually does best. That is- Volume from the Liquid Vessel and Pressure from the Tubes.
Alternatively, for a project requiring multiple tube/liquid sources for a series of tests some added efficiency could possibly be achieved by adding a high pressure pumping system to the liquid source. The tubes could be used to provide fast flow and pressure to the pipeline. The portable liquid nitrogen vessel could be used to replenish the tubes between tests. It could also be used to discharge an initial volume of molecules into the pipeline. This approach could be advantageous in cases where it is more convenient and cost effective to deliver liquid to a site for refilling the portable cryogenic vessel than it is to swap out or refill tubes. There is also a good possibility that an 850 gallon GOrilla-type vessel with trailer, vaporizer pumping system and power source is less expensive that a tube trailer with comparable volume. Use of less expensive portable cryogenic vessels in place of high pressure tubes (where feasible) could allow more valuable assets to be used where they are required.
There is also the side benefit that the portable cryogenic vessel could be used for many other applications when not tied to high pressure testing and purging. The ability to keep capital invested in cryogenic vessels working for pipeline freezing, liquid delivery, welding purge, harvest, or high volume cutting applications warrants consideration. This is particularly true in the event that the highly versatile liquid and gas use vessel requires less capital investment, less ongoing testing/ recertification cost and provides more positive financial return than a set of tubes holding a comparable volume of nitrogen.
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