Multiphase flow pump B experienced failures in March and June 2010 due to destruction of the rotor and choking of sand at the outlet. An analysis found that sand was accumulating in the U-shaped suction pipes below the pumps when they were idle. This sand would then enter the priming pumps and damage the rubber stators. It is recommended to install a large sand trap to prevent accumulation of unfiltered sand, rehabilitate pumps A and C, regularly inspect stators for wear, and follow manufacturer maintenance instructions to extend pump lifetimes.

1. Multi-Phase Flow Pumps Failure Report
Background
As per Adar maintenance supervisor report, Multiphase flow pump-B experienced twice failures on
(30/3/2010) and (6/6/2010). This failure appears as destruction in the rotor of the priming pump at the
suction entrance and sands were chocked at outlet.
System Description
• OGM-5 receives oil from 15 production wells (3 ESP & 12 PCP). All these wells have no strainers in
their flow lines except well AD-18.
• OGM-5 contains one strainer used only for Multiphase flow-meter. Also, it contains three
Multiphase flow pumps A/B/C.
• All Multiphase flow pumps have built-in basket filters directly upstream pump intake.
• 6 inch suction pipe for all MPFP and 1 inch suction pipe for attached lubricating pumps.
• As per PM schedule plan, the built-in pumps' filters are flushed every two weeks.
Failure Events
• As per FSF daily report, Pump-C stopped almost one year ago due to failure of a dry run
temperature sensor.
• As per FSF daily report, Pump-A stopped on (8-Feb-2010) due to damage of the dry run
temperature sensor which was already borrowed from OGM-1 MPF pump.
• As per FSF daily report, Pump-B was running alone since (8-Feb-2010).
• When the priming pump disassembled, the rubber stator moved out with the rotor (stuck over the
rotor). Also, the MPFP rubber stator found damaged and worn out.
• Sound noise was detected out of MPF pumps bearings.
Failure Analysis
• The three suction pipes for the pumps are constructed in U shape below the altitude of the 6 inch
header and the pump suction. Thus, it became an area for sand accumulation specially when the
pump in standby.
• The suction pipe for priming pump is taken from the 6 inch pipe at six O'clock position at the lowest
part of the U-shape. When the pump is off the 6 inch line remains heat insulated and crude oil
viscosity reduced, this helps the course (heavier) sand to precipitate to pipe bottom and been
sucked in the next priming.
• Since the priming pumps are not heat insulated, more sand will jellied in the suction entrance and
in the pump during standby periods.
• Sands (as foreign bodies) wear out the rubber stator worm paths and reduce positive displacement
efficiency. Thus, allowing more sand to accumulate inside and this lead to internal blockages.
• Blockage possibility increases as long as course sands enter the priming pump leading to dry start-
up of the MPFP.
• Moreover, the elastomer will stuck on rotor and the torque tends to separate the elastomer from
the stator casing.
• As per pump manufacturer precautions; a few rotations in dry condition will damage the stator.

2. • Recent PMs performed for the basket filter of pump-B demonstrate presence of big quantity of
course sand (As per FSF maintenance foreman) and most of these sands will go directly to the
unfiltered priming pump.
Recommendations
• According to the mentioned analysis, it is quite obvious that the major cause of the problem is the
sand content. Therefore, construction of big sand trap located at the highest area of the suction
header is highly recommended to prevent accumulation of unfiltered well sands.
• General specification for the proposed Sand trap:
- Type: Horizontal sand trap.
- Body: Carbon Steel.
- Flange: 6'' ANSI CL600.
- Screen type: Determined according to engineering study.
- Mesh size: Determined according to engineering study.
• Rehabilitation of the Pump-A&C (complete overhaul) and spare parts provision (Ex; dry run temp.
Sensor, etc).
• As per manufacturer instruction the stator is to be regularly checked for wear. Inspection and
Maintenance intervals shall be as follow :
- Operating Time of > 16 h/day, at least twice a year.
- Operating Time of < 16 h/day, at least once a year.
•••• As per manufacturer instruction; shaft bearings replacement shall be after 14500 hours (according
to prEn 13463-5: replacement after 90% of the designated service life). For most of OGMs pumps;
bearing life time has already run out.
•••• Strict compliance to the manufacturer's O&M instructions will extend life time of all MPF pumps.
Prepared By:
Musab Humaida
Facility Engineer