API MPMS 4.9.2:2005(2015) pdf download

API MPMS 4.9.2:2005(2015) pdf download.Manual of Petroleum Measurement Standards Chapter 4-Proving Systems Section 9—Methods of Calibration for Displacement and Volumetric Tank Provers.
6.2 DISPLACEMENT TYPE UNIDIRECTiONAL PROVERS WITh FREE DISPLACERS
A unidinxtional prover with a free displacer operates with some type of sphere handling interchange. If this interchange is left in place during the waterdraw calibration, then it is normally used to launch the sphere for each calibration pass/run. At the end of its pass/run the sphere is allowed to continue into the interchange to await its next launching.
Before beginning a calibration on any unidirectional displacement prover with a free displacer. the air must be vented at all high points. This includes those points, which are static during the calibration, All venting shall be done hetbre. during, and after moving the sphere through the prover several times, by leaving the vents partially open and continuously bleeding otT air and water.
lFnidirectional provers with sphere interchanges require special attention in that all the air must be vented with the interchange in both the open and salcd positions. This shall be done beliwe, during, and al’ter moving the sphere through the prover several times, by leaving the vents partially opeii and continuously bleeding off air and water.
With the interchange in place and functioning, the calibration can be perfonned using the nonnal operation to launch and receive the sphere displacer. To improve air elimination and temperature stability the sphere should be allowed to complete us forward travel at the end of a calibration pass. and be sent through the interchange for a re-launch from the launching chamber.
A four-way valve is usually located between the prover and the waterdraw unit for sphere positioning purposes at the first detector switch. All measured calibration pass/runs shall he made in the same direction as in normal prover operation. A trial run is sometimes made to work out any operational details and verify the approximate prover volume (especially on new provers).
Sometimes, the interchange is removed for the period of the calibration and replaced with a blind flange equipped with a connection to serve as the prover water inlet. In that case the sphere has to he placed into the prover pipe prior to the titling of the blind flange. At the end of each pass/run, a four-way valve, located on or near the waterdraw unit, is used to return the sphere hack to its starting position. On other occasions the sphere interchange may be removed or blinded-off from the remainder of the prover, and the sphere traversed inside the pipe between the prover detector switches. When the calibration is performed in this way the sphere is kept in the ,ipe section of the prover at all times and special care must he exercised to ensure the complete evacuation of air. After the displacer has been launched and completed its calibration run, a four-way valve is required to return the sphere displacer back to its starting position upstream of the first detector. Therefore, when using a fnur-wa’ valve to return the sphere to the starting detector, the return pass is not measured, It is essential that all calibration runs he conducted in the same direction that the displacer normally travels.
Regardless of whether an interchange is being used or not, a four-way valve is required to position the sphere at the starting detector. See Figure I.
On the lirst pass the following starting sequence is followed to position the sphere into its starting position under the first detector switch. The detector switches are named “A” and “B”.
I. 11w sphere is directed FORWARD to Detector A at normal flow rate, until it passes completely through this detector. Closing the circulation block valve then stops the flow.
2. The direction of the flow is changed to REVERSE using the four-way valve.
3. The circulation block valve is re-opened and the sphere is now traveling in the REVERSE direction back through Detector A for a short distance until the audible or visual signal (if used) ceases. Closing the circulation block valve again stops the flow.
4. The direction of the flow is changed to FORWARD using the four-way valve.
5. The water flow is now directed through the solenoid valve, in the FORWARD direction. All the water is now passing only through the solenoid valve at a very slow flow rate.
6. At this time the pressure of the system shall be read on the downstream side of the displacer, by means of a pressure gauge that is usually installed on the waterdraw calibration unit manifold.
7. When Detector A is actuated, the solenoid valve operates and the water flow is directed into the first test measure.