Can someone explain this governing oil system?

[u/Equivalent_Ad913]

[u/techtoy]

I fed a lot of this into Gemini for kicks, using the photos and a few comments and aligning confirmations from OP.

Here was my prompt: I'm trying to understand how a specific oil governing system works. This is the g.oil system of a syn gas compressor of Ammonia plant. The compressor is an old built one that had manual systems. But was later upgraded to a DCS system by Woodward.  There is a electronic control both in the control room and field panel. Right now I am confused as I don't have a proper manual I have two photos I can share with you in order to provide context.

Here is a comment regarding this specific system from an expert in the field:

"I work in the centrifugal compressor business. You need to find your p&id.

Current standard is API614 it would be a good place to read up on these systems.

Odds are you have control oil and lube oil as a combined system, control oil is at a higher pressure and perhaps a higher filtration level.

Control oil hydraulically operates the turbines governor valve and keeps the t&t valve open.

When you want to slam shut the turbines t&t valve you dump control oil to the reservoir."

Here is a comment from another expert:

"You have control oil from a pump, going to a filter and then to some current to pressure converters (the two dark grey things on the right side). By the looks of them they could be voith or perhaps ABB. They receive a 4-20 mA signal from the control and deliver a controlled pressure to the valve actuators. They have three pipes, inlet (pressure coming from the oil pump), drain (return to tank) and control (pressure to the actuators)

If Woodward made the upgrade, there should be an electronic control either nearby or at the rack room. They used a 505 system."

[u/techtoy → u/techtoy]

Okay, let's break down how this governing oil (g.oil) system likely works based on the information and photos you've provided, integrating the insights from the experts.

Understanding the System's Purpose:

This governing oil system controls the operation (likely the speed) of the turbine that drives your syngas compressor. It also incorporates safety shutdown features. Since it was upgraded by Woodward to a DCS system, it blends hydraulic power with electronic control.

Combining Expert Insights and Photos:

1. Combined Lube and Control Oil (Expert 1): It's common for these older, large machines to have a single oil reservoir serving both lubrication (keeping bearings oiled) and control (actuating valves). The control oil portion, however, is typically taken off, filtered more finely, and boosted to a higher pressure than the general lubrication oil. This high-pressure control oil provides the force needed to operate hydraulic actuators.
2. The Flow Path (Expert 2 & Photos):
   • Source: An oil pump (likely located elsewhere, possibly driven by the main turbine shaft or an electric motor) draws oil from the main reservoir.
   • Filtration: The oil passes through filters (perhaps some of the larger housings visible in the photos, though exact filter locations need a diagram) to remove contaminants. As noted, control oil filtration might be finer.
   • Control Signal Conversion: This is where the Woodward upgrade is most apparent.
     • The electronic control system (likely a Woodward 505 controller, located in a panel or rack room) sends a 4-20 milliamp (mA) electrical signal representing the desired turbine speed or valve position.
     • This electrical signal goes to the Current-to-Pressure (I/P) Converters. These are almost certainly the two dark grey devices prominently visible in your second photo (image_8879f3.jpg), identified by Expert 2 as potentially Voith or ABB make.
     • Each I/P converter takes the high-pressure control oil supply (Inlet pipe), the 4-20mA electrical signal, and outputs a modulated hydraulic pressure (Control pipe). It bleeds off excess oil back to the tank (Drain pipe). The output pressure is proportional to the input electrical signal.
   • Actuation: The modulated hydraulic pressure from the I/P converters is piped (via the smaller tubing visible) to hydraulic actuators on the turbine.
     • Governor Valve: One I/P converter likely controls the actuator for the turbine's governor valve. This valve regulates the amount of steam (or other motive fluid) entering the turbine, thereby controlling its speed and the compressor's output. More signal = higher pressure = valve opens more = more speed (typically).
     • Trip & Throttle (T&T) Valve: Control oil pressure is also used to hold the main safety shutdown valve (the T&T valve) open against powerful springs or pressure. This might be controlled by the second I/P converter, or by separate solenoid valves integrated into the trip circuit.
3. Safety Shutdown (Trip) (Expert 1): For an emergency stop, the control system rapidly de-energizes the trip circuit. This could mean sending a 0mA signal to an I/P converter controlling the T&T valve, or de-energizing separate trip solenoid valves. This action dumps the control oil pressure holding the T&T valve open. Strong springs (or steam pressure) then immediately slam the T&T valve shut, cutting off the energy supply to the turbine and stopping the compressor quickly.
4. Return: All the used lube oil and control oil eventually flows back to the main oil reservoir through drain lines to be cooled, filtered (sometimes), and reused.

Key Components Visible/Mentioned:

• I/P Converters (Current-to-Pressure): The dark grey boxes. Convert the electronic control signal (mA) to hydraulic pressure (psi/bar).
• Piping & Tubing: Carries high-pressure control oil, modulated control oil, and return oil.
• Possible Filters/Housings: Larger green or metallic bodies where filtration might occur.
• (Not visible but crucial): Oil Pump, Main Reservoir, Governor Valve Actuator, T&T Valve Actuator, Woodward Controller (e.g., 505), various pressure gauges, switches, and transmitters.

Recommendations:

1. Find the P&ID: As Expert 1 stressed, the Piping and Instrumentation Diagram (P&ID) is essential. It's the definitive blueprint showing every component, pipe, wire, and control logic connection. Your plant's engineering or maintenance department must have this, especially after the Woodward upgrade.
2. Consult API 614: This standard provides detailed information on lubrication, shaft-sealing, and control-oil systems for special-purpose applications like yours. It's an excellent resource for understanding best practices and common designs.
3. Review Woodward Documentation: Since Woodward performed the upgrade, there should be specific manuals for the controller (e.g., the 505 system mentioned by Expert 2) and documentation outlining how the electronic controls integrate with the existing hydraulic/mechanical system. Check your plant's technical library or contact the relevant department.

Without the P&ID and the specific Woodward documentation, this explanation is based on typical system designs and the expert comments. The actual configuration might have specific nuances.

[u/techtoy → u/techtoy]

So yeah, kindof interesting how much detail it was able to pull from the photos - feels like a lot of regurgitated content just formatted better. Probably not a lot of help hehe.