Meter Proving Apparatus

1. Field of the Invention

The invention relates to meter proving apparatus for use in test flow meters incorporated in a pipe line for indicating fluid flow rates.

2. Description of the Prior Art

U.K. patent specification No. 865,882 discloses an apparatus for calibrating a meter in a pipe line including a calibration pipe which is fluidly connected into a main pipe line and switches adjacent to each end of and projecting into the calibration pipe and operable by a plug located in the pipe which passes along the pipe with fluid flow. Three-way valves are provided for establishing fluid flow from the pipe line along the calibration pipe in either direction. In order to ensure that the flow in the calibration pipe is fully established before the plug reaches the first of the two switches, it is necessary to provide a considerable length of calibration pipe and whilst this may be satisfactory for a land based system where space is not at premium, it is not acceptable for use on off-shore oil extraction platforms where the space available for such equipment is strictly limited. The object of the present invention is therefore to provide a meter proving apparatus in which fluid flow can be established through the calibration pipe prior to a test operation whilst minimising the length of the calibration pipe.

The invention provides a meter proving apparatus comprising a calibration conduit for receiving a fluid, a plug located in the conduit to be carried along the conduit by fluid flow along the conduit, two stations at the ends of the conduit for accommodating the plug prior to a test operation, two plug detector devices spaced apart along the conduit between the end stations to signal the passing of the plug for use in computing the fluid flow rate along the conduit and valve controlled connecting means for connecting one end station to a pipe line including a meter to be proved to receive fluid from the pipe line and connecting the other end stations to the pipe line to return the fluid to the pipe line and vice versa, said valve controlled connecting means including a by-pass for at least a part of each end station in which the plug may be located so that the plug may be by-passed before a test operation is started whilst fluid flow to the conduit is established.

FIG. 1 is diagrammatic view of one form of meter prover apparatus;

FIG. 2 is a more detailed plan view of the apparatus of FIG. 1;

FIG. 3 is a side elevation of the apparatus of FIG. 1; and

FIG. 4 is a diagrammatic view of a further meter proving apparatus.

Referring first to FIGS. 1 to 3 of the drawings, there is shown a meter proving apparatus for use in calibrating an in-flow, volume flow rate meter in a pipe line, for example, for oil or liquified petroleum gas. Conventionally, a number of flow meters are connected in parallel conduits extending between inlet and outlet headers connected in the pipe line. For example, four such conduits each containing a flow meter may be provided for indicating the flow in the pipe line. Isolating valves are provided in the conduit on either side of each flow meter. Each of the conduits may have a branch conduit extending to a prover header through a valve control and the prover header is connected to the prover apparatus as described below through a valve mechanism and the prover apparatus is in turn connected to the aforesaid outlet header for returning the flow to the pipe line.

Referring now to FIG. 1 of the drawings, the conduit extending from the prover header is indicated at 10 and is connected to a flow reversal valve indicated at 11 having one outlet conduit 12 for returning the fluid flow to the aforesaid outlet header and two outlet conduits 13, 14 which are connected to a U-shaped calibration conduit 15. The U-shaped calibration conduit 15 has enlarged diameter end chambers 16, 17 respectively and conduits 13, 14 are connected to the ends of the chambers 16, 17 respectively via diverter valves as described below. A sphere 18 is shown located in one of the end chambers 16. When fluid flow is established through the conduit 15, the sphere 18 is carried by the fluid around the calibration conduit, the sphere being an interference fit in the main part of the calibration conduit 15 between the end chambers 16, 17 to prevent any significant loss of fluid past the sphere as it is carried around the calibration conduit.

Two sphere detection devices 19, 20 are provided at spaced locations around the conduit 15 adjacent the end chambers which are actuated when the sphere passes and provided electrical signals used in a measuring apparatus for determining the actual flow measurement of liquid through the calibration conduit 15 for comparison with the indicated flow measurement on the meter being tested in a known manner.

The conduits 13, 14 connected to the end chambers 16, 17 have diverter valves 21, 22 therein for diverting flow into by-pass conduits 23, 24 which are connected to the end chambers 16, 17 adjacent the main part of the calibration conduit 15. Thus if the sphere 18 is located generally at the centre of the end chamber 16 as indicated in the Figure, the diverter valve 21 can be arranged to divert flow through the by-pass 23 and into the end chamber 16, adjacent the main part of the calibration conduit 15 to by-pass the sphere so that the sphere is not carried into the main part of the calibration conduit. This enables the flow of fluid to be established around the calibration conduit before the sphere is introduced into the main part of the calibration conduit to carry out a meter proving operation. When the flow has been fully established, the diverter valve 21 can simply be switched over to direct the fluid directly into the end of the end chamber 16 and the flow then carries the sphere 18 into the main part of the calibration conduit to perform a calibration operation. The diverter valve 22 at the downstream end of the calibration conduit is set to receive fluid through the by-pass 24 so that the fluid flowing around the calibration conduit 15 is diverted from the end chamber 17 to the by-pass 24. This leaves a column of fluid trapped in the end chamber 17 by the valve 22 which cushions the entry of the sphere 18 to the end chamber at the end of the proving operation, preventing the sphere from colliding with any significant impact against the ends of the end chamber 17. The fluid passing through the by-pass 24 and the valve 22 is directed by the valve 11 into the return conduit 12 to the main outlet header.

At the completion of a meter proving run in one direction, the valve 11 and valves 21 and 22 can simply be switched over to reverse the direction of flow through the calibration conduit 15 to perform a meter proving operation in the opposite direction.

The valves 21 and 22 can be conveniently connected to a single motor driven mechanism for adjusting the valves.

Referring now to the embodiment shown in FIG. 4 of the drawings, like parts have been alloted the same reference numerals. The main differences are that the valve 11 is replaced by a three-way valve 28 which has outlets to the conduits 13, 14 and the by-passes in the conduits 23 and 24 are omitted. Instead each end chamber 16, 17 has a separate conduit connection 25, 26 respectively, connected to the end chambers 16 and 17 adjacent the main part of the calibration conduit 15. The conduit 25, 26 extend to a three-way valve 27 the outlet of which is connected to the conduit 12 leading to the main outlet header of the apparatus. If fluid flow is established in the direction shown by setting the valve 28 to deliver fluid into the conduit 13, the valve 27 can be set to connected conduit 25 of the chamber to exit the fluid into the conduit 12 to return to the outlet header. The fluid flow will carry the sphere 18 to the forward position of the end chamber as shown in dotted lines just beyond the conduit 25 but not into the main part of the calibration conduit so that the end part of the end chamber is in effect by-passed and the fluid flow allowed to be established before the sphere 18 is directed into the main part of the calibration conduit. When the fluid flow has been appropriately established, the valve 27 is switched over to connect the conduit 26 of the other end chamber 17 to the outlet conduit 12 and the fluid flow is then established around the calibration conduit 15, the fluid exiting from the chamber 17 through conduit 26, valve 27 and outlet conduit 12 to return to the outlet header. A column of fluid is held in the end chamber 17 by the valve 28 and this cushions the entry of the sphere into the end chamber to prevent the sphere colliding with the end of the chamber as before. Again, as before, the valves 28 and 27 can be appropriately switched over to direct fluid in the opposite direction around the calibration circuit for subsequent meter proving operations.