Hydraulic Power Unit Repair

Sometimes the problem is obvious. Other times the HPU is running hotter than normal, losing pressure or flow, working fine cold and falling off when hot, or contaminating the hydraulic oil.

We can work through the HPU and the equipment it powers to determine what needs attention.

Heat is one of the most common HPU issues we see.

Some units, including the NOV / Varco HPU 35, tend to operate on the warm side. The important question is whether the temperature is normal for that unit and operating condition, or whether something has changed.

High hydraulic oil temperature can come from:

• Worn pumps or motors
• Internal leakage
• Relief or bypass flow
• Dirty or restricted oil coolers
• Cooling fan problems
• Restricted filters
• Suction problems
• Incorrect or degraded hydraulic fluid
• Contamination
• Excessive system load

The answer is not always a bigger cooler or a new pump.

Mondak can look at pressure, flow, temperature, pump performance, cooling, filtration, fluid condition, and how the system behaves under load.

The goal is not to make the HPU run cold.

The goal is to determine whether it is running the way it should, and if it isn't, why.

Many oilfield HPUs use diesel engines, including units powered by Detroit Diesel Series 60 engines and other diesel power packages.

Mondak can troubleshoot:

• Diesel engine performance
• Engine controls
• Fuel systems
• Cooling systems
• Pump drives
• Hydraulic pumps
• Engine RPM under load
• Electrical systems
• Shutdown and protection circuits

If the engine cannot maintain the power or RPM the hydraulic pumps need, the equipment being powered can look like it has a hydraulic problem.

That is why we may look at the engine and hydraulic system together.

Mondak can repair and troubleshoot:

• Hydraulic pumps
• Hydraulic motors
• Directional valves
• Proportional valves
• Relief valves
• Flow and pressure controls
• Manifolds
• Accumulators
• Reservoirs
• Filters
• Hydraulic hoses and hard lines

A system that will not build pressure does not automatically need a pump.

Internal leakage, a bypassing valve, restriction, engine problem, overheating, or another condition can create similar symptoms.

Sometimes the HPU is blamed for a problem that is actually in the top drive, power swivel, iron roughneck, or catwalk.

Other times that equipment is showing symptoms caused by the HPU.

Mondak works on both sides.

That gives us the ability to look at what the HPU is supplying and what the equipment is actually demanding from it.

Most oilfield HPUs are too large or too integrated into the equipment to simply load up and bring to a repair shop.

That is why field service is a major part of what Mondak does.

We can come to the equipment and troubleshoot the HPU where it is operating. That allows us to see the unit under real operating conditions and, when possible, evaluate the equipment it is powering at the same time.

Field repair can include:

• Pressure and flow testing
• Hydraulic temperature troubleshooting
• Pump and motor diagnostics
• Cooler and cooling-system checks
• Filter and contamination issues
• Valve and manifold repair
• Hydraulic hose and hard-line repair
• Diesel engine diagnostics
• Electrical and control troubleshooting
• Component replacement
• System flushing and cleanup
• On-site modifications and repairs when practical

Some individual components may still need to come back to the Mondak shop for rebuilding, machining, or more extensive repair.

But in most cases, the HPU itself stays in the field and Mondak goes to it.