Consider the testing of a chemical processing plant which is placed on line and operates indefinitely. Periodically, it is necessary to test the product made in the plant. That is a difficult task to accomplish in many circumstances, especially those where the process operates at very high pressures and temperatures. Typically, high pressures and temperatures make it difficult to obtain a sample. Moreover, expensive metals and expensive fabrication techniques are required to enable the processing plant to be properly confined within the structure which holds the process. This remains a problem even when only a small sample is required for periodic testing. Not only must the sample be removed from the process plant, the sample must be delivered into a sample container for easy transportation to a lab for testing. Consider as an example a petrochemical processing plant where a process is carried out at elevated temperatures of over 1,000.degree. F. and very high pressures limited primarily by the pressure rating of the equipment of the sample collection system. The fluid flowing in the process pipes and pressure vessels of the processing plant may flow at a rate of hundreds of gallons per minute, and yet only a small portion is required for testing, for example, one liter. There is even the possibility that the sample will change from a gas to liquid on reducing the temperature and pressure to remove the sample. Transfer of the sample from the interior of a process plant through the walls of the pipes or other pressure vessels which contain the process requires tapping the process to obtain the sample, and this must be done without permitting the sample to escape to atmosphere. Except in rare cases, such a sample is at least partially, and often extremely volatile. In any event, a sample must be removed from the processing plant, transferred through a set of flow lines, metered into some sort of sample container, and then delivered for subsequent testing, for instance, at a testing laboratory sample analysis or other testing can be carried out. One mode of testing is to fill a small sample container, carry it to the testing lab, and conduct the test there. This enables a single testing lab to test samples from several different locations on a process plant. For instance, a single process plant may comprise several different columns with intermediate stages of processing, thereby generating samples at 10 or 20 different locations; samples are obtained at different times of the day from the several sample locations, the tests are then run, and product quality and purity is then certified as a result of the laboratory testing.
The present apparatus and method enable periodic testing to be carried out in this fashion. This disclosure sets forth a means and mechanism for such testing notwithstanding the fact that testing is required of the product when the product is manufactured at extremely high pressures and temperatures. Immediately, there is a problem in removal of the sample. For instance, as a result of high process temperatures, the removed product typically will be a gas, and will tend to be reduced in size should it undergo a phase conversion from gas to liquid. On the other hand, because of extremely high pressures, a sample will tend to expand when the pressure confinement is reduced. It is therefore somewhat difficult to scale the amount of sample to be removed so that the proper size and consistent size of sample can be provided in a sample container. The present apparatus enables this to be accomplished. Moreover, it is accomplished in the context where one or several sample containers can be serially filled with each separated from the other at the sample taking stage. The timed separation of samples is accomplished by providing fixed flow lines extending to the sample receiving container which are periodically purged with nitrogen to assure that there is no remnant of sample gas in the lines for later sample collection. The purging of lines assures that two samples taken hours apart are not mixed serially by storage in the connective lines. Moreover, this is all accomplished without permitting fugitive emissions to atmosphere. In part, that is prevented and protected against by utilization of a closed housing which is maintained under a blanket of nitrogen. This assures that there will be minimal accumulation of explosive gases in the housing, or gases which otherwise create some type of hazard. Finally, the system operates so that it can be cyclically controlled by a handle for the purpose of periodic operation of a two position, six port valve.
In summary, the present disclosure is a system for transfer of a sample by means of permanently made connections to a process across a flow restriction in the process. Connection is through an inlet line and outlet line. These connections extend to two ports on a six port valve. There is a sample storage loop in the six port valve. The sample storage loop includes a sized volumetric buffer tank. It is sized so that the sample that is delivered at the prevailing pressure and temperature is held in this buffer tank. To the extent that there is either expansion or contraction by transfer out of the process plant to a reduced pressure and a temperature approaching ambient, there is sufficient size in the buffer tank to permit a properly sized sample to be collected. A purge gas source connected to a needle valve with a flow meter connects to a fifth port, and the sixth valve port is connected by means of a sample line extending to a syringe needle for filling a closed sample container. A sequence of operations is also set forth where the sample is delivered for intermediate holding and later for delivery into the sample receiving container. In addition to that, the equipment operates in a sequence to direct a continuous flow of nitrogen for purging of the connective lines.