Gauge the delivered and receiving shore tanks after the completion of the line displacement. Normally TOV volumes are used to quantify volumes transferred; however, TCV can be used if it has been historically demonstrated to be appropriate for the pipeline size, distance between vessel and shore, and/or temperature difference between vessel, pipelines, and tanks, or by commercial agreement. The standard does not address how TOV is to be converted to a standard volume, in the event that the parties agree to adjust the out-turn, our suggestion is to apply the volume correction factor using the sending tank’s API gravity and temperature to the TOV difference, rather that comparing the GSV difference between the sending and receiving tanks, because large differences in the density or temperature of the pipeline contents from those of the receiving tank can effect the accuracy of the GSV to GSV comparison. One of the drawbacks of this method is that it can only be performed on the opening of a transfer; necessitating a different method to be used to determine pipeline fullness at the close of the transfer. If this method is used, you should establish, prior to cargo transfer, which one of the alternate methods will be used to determine line fullness after the cargo transfer.
5.3.1 Internal Circulation Gauge the delivering and receiving shore tanks before line circulation. Circulate product through the designated pipeline system, which should pass through the designated dock manifold, after the system has been isolated to displace the agreed volume, which shall be a minimum of 100% of the combined capacity of all designated transfer lines (110-120% is preferable if terminal conditions allow). Gauge the delivered and receiving shore tanks after the completion of the line circulation. Normally, TOV volumes are used to compare sending and receiving tanks. The procedure is to be repeated until the difference is less that the agreed tolerance. An advantage of this method is that it can be performed at both the beginning and the end of the transfer. 5.3.2 Line Displacement This is probably the most common form of line verification. Gauge the delivering and receiving tanks before line displacement. Transfer the agreed volume for displacement between vessel and shore, which shall be a minimum of 100% of the combined capacity of all designated transfer lines (110-120% is preferable if terminal conditions allow).
5.3.3 High-Point Bleed-valve This is the least used and least practical method for pipeline fullness verification. While considered a valid method, there are very few pipeline systems that have bleed valves at every high-point. This method can be problematical on systems with extensive sections of horizontal pipe. Also, releasing vapors into the atmosphere can be problematic. 5.3.4 Pigging Method Pigging is a very effective method of displacing the contents of a pipeline and is most common in terminals that handle chemicals, although they can be found in ones that handle petroleum products. It can only be performed with pipelines that are equipped with a pig launcher and receiver. The "pig" is a plastic flexible cylinder with vanes or wipers on its exterior. The "pig" fits snugly against the interior of the pipeline and displaces the liquid in front of it as it is propelled through the pipeline. 5.3.5 Line Press or Line Pack This method, as written, assumes that the void in the line is due to gas vapor from the line contents. The theory is that the pressure from the line pack will condense the vapors back to a liquid and therefore the line pack process will in effect fill the line.
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