Indonesia Offshore Submersible Pump Service Case: Diagnosing Low Pressure in Two 55kW Pumps

When two submersible pumps at an offshore installation in Indonesia developed low discharge pressure and abnormal operating conditions, our first task was to separate a possible pump fault from an installation problem.

The project used two 250QJH95-122/5-55kW submersible pumps installed in the same well. The recorded well diameter was 599.4 mm. Because the two units had to operate in a confined space, the installation arrangement, intake clearance and mechanical connections were just as important as the condition of the pumps themselves.

This case shows why on-site pump troubleshooting should follow measured evidence instead of immediately assuming that the motor or hydraulic components have failed.

The service involved two pumps with the following recorded information:

• Pump model: 250QJH95-122/5-55kW

• Serial numbers: 25110602 and 25110601

• Quantity: Two units

• Well diameter: 599.4 mm

• Installation: Offshore facility in Indonesia

• Main symptoms: Falling pressure, abnormal noise and unstable operating current

The QJH units are multistage submersible pumps intended to operate fully submerged. During service work, the pumps had to be lifted from the well and handled vertically with chains and lifting slings. The limited working area increased the importance of planning each removal and reinstallation carefully.

The first pump initially reached a discharge pressure of approximately 8 bar during its first 24 hours of operation. On the second day, the pressure dropped to about 6 bar. By the third day, the maximum pressure had fallen to approximately 4.3 bar, while motor current reached about 101.3 A.

The site team also reported clear abnormal noise during operation. Because pressure continued to decline, the first pump was stopped.

The second pump behaved differently. From the beginning of operation, its maximum discharge pressure remained at only about 4.3 bar.

These symptoms could have come from several sources, including incorrect rotation, a blocked inlet, hydraulic leakage, loose pipe connections or internal pump damage. We therefore avoided selecting a cause before checking the complete system.

On September 9, both pumps were started for diagnostic testing. The three-phase power sequence had already been checked, and the motor rotation direction was confirmed to be correct.

The first pump drew approximately 94 A and produced about 4 bar of pipeline pressure. The test also showed a pressure drop accompanied by loud noise.

The second pump drew only about 36 A and did not discharge water after startup.

The team inspected the piping visible above the water surface and found no obvious leakage. There were also no visible signs of underwater turbulence that would clearly indicate a major submerged pipe leak.

Confirming the rotation direction was important. Low flow and pressure are often blamed on the pump, but a three-phase pump running in the wrong direction can produce similar symptoms. In this case, rotation was not the cause, so the pumps had to be removed for direct inspection.

On September 11, both pumps were lifted from the well. Inspection found that the main pump components were functioning normally.

The primary problem was an anti-collision rubber component that had been added during on-site installation. Its position restricted the pump water inlet. The same problem affected both pumps.

This finding explained why the second pump could run without discharging water and why the first pump experienced declining pressure and abnormal noise. The pumps could not receive a stable, unrestricted water supply through their inlets.

The rubber component was intended to protect the pumps from contact inside the well, but its installed position created a new hydraulic obstruction. This is an important installation lesson: any protective part placed near a submersible pump must remain clear of the suction inlet under both stationary and operating conditions.

After the intake issue was corrected, the pumps were recommissioned on September 14. The service record states that the pumps showed no internal fault and were able to reach approximately 12 bar at 85 A.

The end user then requested an operating setting of about 5 bar, 137 m³/h and 105 A. On September 15, the current stabilized at approximately 102 A. After discussion with the end user, the flow was reduced to 115 m³/h to protect pump service life.

These results confirmed that the earlier low-pressure condition was not caused by a failed hydraulic assembly. Once the water inlet was clear, the pumps recovered substantial pressure.

After the pumps ran for a full day and night, the site recorded another change on September 16. Pressure dropped to approximately 4 bar, flow fell to 87 m³/h and current changed to about 92 A.

At this stage, the service team suspected that the two pumps were positioned too close together. Contact or vibration between the units could loosen connection bolts and allow leakage from the rising-pipe assembly. The restricted well diameter made this risk more significant.

This was treated as a suspected mechanical installation issue rather than a confirmed internal pump failure. The operating values and the physical arrangement both pointed toward the need for another inspection.

On September 17, the team decided to pull both pumps again. Double nuts were added to the relevant bolts to reduce the risk of the connections loosening during operation.

The revised installation plan was to reinstall the pumps at different depths instead of placing them directly alongside one another at the same level. One pump would operate at approximately 16 m and the other at approximately 18 m.

Our preferred recommendation was to install only one pump in the well because the available diameter gave the two units limited clearance. The site, however, required a two-pump arrangement. The agreed approach was therefore to stagger the installation depths and strengthen the bolted connections.

The service record notes that the second pump was planned for installation when the vessel could move closer to the offshore platform. We do not describe this later step as completed because the supplied record contains the plan, but not a final commissioning result for both pumps in the revised arrangement.

This project reinforced several practical points that we apply when supporting submersible pump installations.

Cable guards, rubber buffers, centralizers and other protective parts must not cover the pump intake. Their positions should be checked after the complete assembly is lowered, not only while it is lying on the ground.

The pump diameter alone is not enough. The design must include cables, cable guards, lifting components, rising pipes, couplings, bolts and anti-collision parts. Two pumps in one well require enough space to avoid contact during starting, stopping and continuous operation.

Pressure, flow, current and noise changed together in this case. Recording these values at every test helped distinguish an inlet blockage from an electrical phase-sequence problem or an internal motor failure.

Even when the pump itself is operating normally, vibration can affect the rising-pipe connections. Fasteners, locking methods and pipe supports should be selected for the actual installation environment.

A short successful test does not always prove that the complete installation is stable. The pumps initially recovered pressure after the inlet obstruction was removed, but the later overnight run exposed another possible installation issue.

For this Indonesian offshore service case, we worked from the electrical checks to the hydraulic and mechanical installation. We confirmed rotation, reviewed current and pressure, checked for visible leakage, removed the pumps, inspected their components and identified the blocked inlets. When the later operating data suggested another problem, the installation plan was revised rather than treating the earlier test as the end of the investigation.

For customers using submersible pumps in wells, tanks, offshore facilities or other confined spaces, we recommend sending us the complete installation drawing before commissioning. Pump model, well diameter, setting depth, pipe arrangement, cable position and protective accessories should be reviewed together.

If your submersible pump develops low pressure, unstable current, abnormal noise or no discharge, send us the pump nameplate, operating readings, installation dimensions, photographs and video. Our engineers can help organize a troubleshooting path based on the actual evidence.

Contact SLAPK for submersible pump technical support