API MPMS 4.9.1:2005(2015) pdf download

API MPMS 4.9.1:2005(2015) pdf download.Manual of Petroleum Measurement Standards Chapter 4-Proving Systems Section 9—Methods of Calibration for Displacement and Volumetric Tank Provers
Part 1—lntroduction to the Determination of the volume of Displacement and Tank Provers.
5.5 ATMOSPHERIC TANK PROVERS
An atmospheric tank prover is a volumetric ves.sel with an upper neck, upper sight glass. upper scale, and an upper and lower cone usually separated by a cylindrical section, Different types are identified by the way in which their bottom zero is defined. Atmospheric tank proven are described below:
Bottom-weir type: Thi’ prover has a bottom neck beneath the lower cone. The bottom neck iiia or may not base a sight glass and scale, but in any case it has a fixed bottom “zero” defined by the weir.
• Dry-bottom type: This proser usually does NOT base a bottom neck under the lower cone. The closed bottom drain valve defines the bottom “zero” just as on a field standard test measure.
• Wet-bottom type: This prover has a bottom neck beneath the lower cone. The bottom neck always has a sight glass and scale. The bottom “zero” is defined by the “zero” on the scale. In practice, readings above and below the “zero” in the lower neck are common.
6.0 Equipment
Changes in fluid properties. operating conditions and equipment components may affect the uncertainty of the volume relative to the volume obtained at calibration conditions.
6,1 PROVER DETECTOR SWITCHES
A detector switch is a high precision device mounted on a prover, which is itsed to detect the passage of a displacer. The calibrated
volume of a prover is the amount of tluid that is displaced between two detector switch positions. Additional detector switches
may be used if more than one calibrated volume is required on the same prover, or they can also be used to signal the entrance of
a displacer into the sphere resting chamber. Several types of detector switches are descnbed below.
6.1.1 Mechanically Actuated Detector Switches
The mechanical type of detector switch is used primarily with an ela.stomeric sphere displacer, but there are applications where they axe used with piston displacers. and are operated when the displacer contacts a rod tw ball protruding into the prover pipe. At the point of operation a switch is closed or opened by means of a mechanically or magnetically driven contact.
Mechanically actuated detectors may or may not be pressure balanced. Pressure balanced detectors have ports or passages that allow pressure to be equally distributed on the switch rod, thereby ofisetting the effect of pressure on the activation of the detector.
6.1.2 Proximity-Type Magnetically Actuated Detector Switches
This type of detector switch is used only with piston displacers and is mounted estenially with no parts protruding into the prover pipe. An excitor ring on the non-magnetic piston displacer actuates the detector switch mechanism as it passes beneath the proximity type detector switch.
6.1.3 OptIcally Actuated Detector Switches
Conventional design of the optical detector has a light source, together with a photoelectric detector cell, mounted opposite each other on a small metal base plate. In nomad operations the light source shines directly into the photoelectric cell until the light beam is interrupted by a lever or plate mounted to a moving rod on the displacer. Breaking of the light beam causes the detector switch to operate.
6.2 LAUNCHING CHAMBERS AND TRANSFER CHAMBERS
In both unidirectional and N-directional provers, an area must he provided in which the displacer can rest when not in use. In bidirectional meter proven, this space is defined as a launching chamber. Hi-directional provers using sphere displacers require launch chambers at both ends of the prover pipe. Piston type hi-directional proven do not require esponded launch chambers at either end of the prover pipe because the flowing stream does not go around the piston. but is diverted upstream of the launch chambers by meaas of check valves. On unidirectional meter provers, a transfer chamber is used in combination with one or more salves, to store the sphere away from the flowing stream, and to provide a means to re-launch the displacer when required.