Scope
This procedure describes the actions to be taken to check the prover
sphere. It will normally be done every six monthly and prior to the recertification of the prover loop. It will normally be carried out by the maintenance department and, at the time of re-certification, witnessed by the certifying authority and interested parties.
PROVER SPHERE INSPECTION
Procedure Prover sphere of the appropriate size and material type shall always be
available.
The Oil & Gas Operators shall check that a spare prover sphere of the
correct size, material, and condition is available, as well as all necessary
sphere tools and a sphere pump. A readily available supply of glycol shall
also be provided.
A spare prover sphere of the appropriate size and material type shall
always be available. This sphere shall be stored such that it does not
deform under its own weight. Practical solutions to this problem typically
involve the storage of the sphere on a bed of polystyrene beads, or the
hanging of the sphere in a sack or mesh sling, (but not a rope cargo net,
as the sphere may extrude and deform).
PREPARATIONS:
Confirm that the removal of the sphere will not interfere with the normal
operation of the metering system.
Give a brief description of the test in the Metering Log Book.
Confirm that the sphere location is known before the prover loop is drained
and isolated. Record the results of this test of the calibration report
PROCEDURE
The prover sphere will be checked using the following procedure: –
a. Open the prover closure and verify that the sphere is accessible.
b. Remove sphere from prover launch chamber / interchange valve.
c. Wipe clean and inspect entire surface of sphere for signs of
damage e.g. shape, cuts, wear, blistering, score marks etc.
Replace if damaged.
d. Confirm the correct inflation size for the prover sphere from the
calibration certificate. Measure the sphere around the equator and
pole planes using a diameter tape. Record the smaller of the two
dimensions on the test sheet.
e. If the sphere size is within tolerance the check is complete and the
sphere should be returned to the prover.
f. If the sphere size is out of the tolerance, the sphere should then be
inflated / deflated with a water/glycol mix using suitable
filling/inflation equipment until the required diameter is obtained.
g. Return the sphere to the prover.
h. Enter details of the sphere size and any problems encountered in
the Metering Log Book.