Solar Lubrication System – FT8 & Solar – Turbine Technical Information

ART271 – Mars Thermostatic Control Valve

Don — Mon, 02 Mar 2026 11:43:51 +0000

The Thermostatic Control Valve regulates how much lube oil is cooled and how much bypasses the cooler to keep the oil within its optimum operating temperature range. Using a wax-filled thermal capsule, the valve continuously modulates as temperature changes—protecting bearings from the damage caused by oil that is too cold or too hot. This overview explains real operating behavior on the Solar Mars, including why the valve often ends up in full-cooler mode in the field.

ART241 – Solar Mars Lube Oil Logic

Donald Murphy — Wed, 19 Jun 2024 19:38:00 +0000

ARTICLE REF – ART241

This video is going to look at the lube oil logic for the Mars turbine.

ART049 – Solar – Mars oil pressure regulator issue – PCV901

Donald Murphy — Wed, 19 Jun 2024 01:29:11 +0000

ARTICLE REF – ART049

The Mars pressure regulation as used on the generator sets with bias control has a tendency to drift low. This article describes one fix to this problem.

Figure 1 shows part of the Mars generator lube oil system. The design of the pressure regulation is very bad and it is common for the oil pressure to drop without adjustment while in operation

The normal practice is to adjust the oil pressure to 10 PSI while the unit is not running, using the spring adjustment on the regulator valve (in red).

Then when the unit is running the oil pressure is adjusted by means of the hand valve.

Note the solenoid is energized at 30% NGP which dumps some of the pressure opening the valve thereby dropping the oil pressure.

This is a drawing of the system before modification.

A pressure regulator Solar PN 1066290 was fitted instead of a hand valve and we never had another problem with the oil pressure.

This is the regulator PN 1066290 we fitted instead of the hand valve.

ART042 – Solar – Centaur / Taurus Pressure & temp control block.

Donald Murphy — Wed, 19 Jun 2024 01:19:11 +0000

ARTICLE REF – ART042

In the graphic below you can see two T60 generator units, one with pressure control issues and one with temperature control issues. This has been an issue with this pressure and temperature control block for many years. Solar released a Service Bulletin 6.0/124 and it is at revision E at least, so that gives some idea of the number of changes there have been. This temperature block was used on Centaur and Taurus generator sets and at one time was mounted at the side of the oil tank, now it is located on top of the tank. The old part number was 190185-xxx and there is at least one newer one part number 1061918-xxx.

If anyone has had issues with this part and would like to share your experience please comment below.

ART041 – Solar – Centaur Lube Filter

Donald Murphy — Wed, 19 Jun 2024 00:52:50 +0000

ARTICLE REF – ART041

This is information I picked up from a blog in Linkedin which I participate called “Solar Gas Turbines – Worldwide Users”.

Some good feedback from someone who read the article at the end ………..

The issue was that the lube oil filters on several Centaur 40 were collapsing in service.

Some background data:
– Filter element is changed every 4000hrs running hours.
– Diff. pressure at the filter less than 0.5 bar.
– Operating Lub. oil pressure header equal 4 bar.
– Filter element is Solar P/N:1026614-11.

Some of the questions and suggestions from participants:

When was the last time you changed the oil?
Was a lube oil analysis carried out?
Is there any abnormal lube oil temperature?
Could there be microbilogical contamination?
If its centaur 40/50 there should be an adapter inserted into the filter to prevent this pressure squeeze.
Consider reducing the time between filter changes.
Is the bypass valve between filters open?
Make sure LO is to spec.
See O&M spec for ISO VG 32 oil and ensure ambient and operating temps for oil are correct.
Pay particular attention to startup limitations to ensure correct oil viscosity prior to starting.
Verify TCV901 and PCV901 are both correctly set and fully operational. Most of the oil should be diverted away from cooler HX901-1 on startup until oil heats up to spec.
Verify pre/post lube oil pump checks are complete and no low pressure FSLO or high alarms experienced.
Record aux pump P902 LO header pressure below starter drop out speed.
Record main pump P901 LO header press above starter drop out speed.
Consider putting a temporary dp transmitter across the main LO filter DP switch S397-1 and ranging say 4-20mA = 0-15 psid. Trend actual dp on startup and during operation. Check all against Device Settings schedules.
LO temp on startup. If your oil is too cold on start up the increased viscosity can lead to temporary off spec flow / dp across filter not necessarily picked up as excessive dp when oil temp reaches specification as oil warms up and dp drops to more normal values.
Is LO tank heater working?
Mechanical pulsations from pumps?
Excessive vibration?
Incorrectly set lube oil pressure header PCV?
Sluggish PCV dynamic pressure control response on startup?
Oxidation / Varnish formation off spec LO?
Incorrect installation of filter.
DP transmitter / gauge and all impulse lines verified as free of debris? No low point traps for moisture formation?

It turned out that not all the units had a collapsed filter. The one that did not had a strainer fitted inside it which prevents the filter from collapsing. This strainer is not shown on the Illustrated Parts List manual.

The solution was in one of the suggestions above.

Feedback from a reader

I find something called “Adapter, Cartridge” PN 997824C1 in the parts book. Unfortunately, it is not illustrated – just listed. Due to time constraint didn’t order the missing adapter from Solar. We just took a same sample adapter from the sister unit and had the missing ones fabricated. I still have the photos of the adapters..

Element adapter has two O-rings seal. One on the adapter OD that seals to the filter element bottom ID. Another on the adapter ID that seals onto the male opening at the filter housing bottom. Seals are critical to prevent debris to bypass the elements. When the filter element is removed from the housing, the adapter OD O-ring being bigger in diameter has more friction and stiction effect to the filter element and will be lifted together with the element. When the adapter is attached into the filter element, it will be flushed at the bottom. One can mistakenly think that it is a complete assembly. Hence it can get accidentally disposed during maintenance.

ART023 – Solar – DC backup pump control

Donald Murphy — Tue, 18 Jun 2024 20:02:28 +0000

ARTICLE REF – ART023

This is a DC pump control panel which was introduced around 1990. Up until that time the thinking was that an emergency pump should have as little protection or to put it another way it should sacrifice itself if necessory to save the turbine. But with new safety standards and electrical specifications there was a lot of pressure on turbine manufacturers to change.

This new design included a thermal overload (indicated in yellow), the idea being that if the current was too high the thermal overload would heat-up and open the circuit to prevent a possible electrical fire. The backup pump is tested as part of the startup routine and some units have the DC pump being tested periodically when in service.

If the pump did not make pressure an alarm would be enunciated. The test does not last very long and it is mainly looking at the pressure. The backup DC lubricating system is designed to run for a period of time (depends on the type of turbine) on the batteries should the mail pumps fail, so hopefully they are in a good state of charge. Something often forgotten during the rush to get a unit back on-line is the state of the batteries. They take time to re-charge, and should there be a power failure or main pump failure during the startup, you will need the batteries to be at full charge. On one site that I am aware of, a Mars compressor set shut down due to a loss to power on the station. The unit shut down was due to loss of cooling air flow in the enclosure. Once the NGP speed dropped, oil pressure also dropped, so the AC pumps were commanded “ON”. As there wasn’t any AC power the DC pump came on automatically. A few minutes into the post-lubrication of the turbine the DC pump stopped. An alarm was annunciated on the display (along with hundreds of other alarms for the unit shutting down), but nobody noticed the pump stopping.

The bearings melted due to heat soak of the turbine. Analysis of the shutdown showed that everything worked as it should. But some minutes into the shutdown the thermal overloads operated, and cut power to the pumps. The thermal overload was discovered to be loose. This looseness acted as a resistance in the circuit, adding additional heat to the thermal overload causing it to trip prematurely.

I would recommend that the DC pump be run for its “emergency time period” during maintenance checks. Just checking amps consumed and oil pressure is not enough. Check the capacity of batteries by removing the charge circuit and force the DC lube pump on for the post-lube backup pump lubrication time. Ensure the pump maintains good pressure during this test.

And for sure “check the tightness of the screws on the thermal overload”!

ART022 – Solar – T130 – Oil flushing

Donald Murphy — Tue, 18 Jun 2024 20:00:50 +0000

ARTICLE REF – ART022

While the heading is flushing the Solar Titan 130, it could be any turbine. The photos are actually of a Titan commissioning.

Bulk oil

Using bulk oil comes with its challenges. Normally the bulk containers are reusable and you have no control over what was in them before you got your oil. If you are commissioning you will be filling a large quantity of oil and you need to pass the oil through a fine mesh filter. As you can see in the photo there was a lot of dirt in oil. Even oil in drums will not normally meet the Solar specification until it has passed through the lube oil filters many times. The main oil filters used by Solar now are often 3 or 5 micron – that is very fine indeed and will improve the cleanliness of even new oil.

Foreign objects

When commissioning you have to have the mindset that anything is possible. This piece of cardboard was found in the oil tank. If not found it would disintegrate and start to block lines, filters, instruments – a real nuisance. On another site a small label stating that the “hydraulic tank was inspected” was left in the tank. It floated on top of the oil for years. When the turbine was being changed at overhaul some of the oil was lost due to lines being disconnected. The level in the tank dropped and during the next start the label was sucked into the suction of the pump. That took a couple of days to find.

Flushing coke from the system

While this is not done at commissioning, it would be necessary if the number 2 seal starts passing hot compressed air into the oil cavity at the bearing. The Titan 130 has a high compression ration which also means it gets very hot. This will form coke when it comes in contact with oil in the bearing areas. With normal amounts of air leaking at the seal you should see oil varnishing of the bearing location. But when the leak gets worse the oil being burnt turns into “coke” which is a hard substance. The Titan can change the color of a tank of oil in one day due to the formation of coke. Trying to flush coke from the oil system is not easy and is very time consuming.

Oil additives

The filters used by Solar in the lubrication system are very fine. The use of 5-micron filters is common. This can remove oil additives from the oil and form a jell like film on the filter. During the commissioning of a T70 the lube tank was filled and the lube pump was circulating the new oil. Within 20 minutes the DP increased so the reserve filter was selected. 20 minutes later the reserve also was blocked. A lab on site was able to identify a jell coating on the filter. The oil was drained and filled again (that is a lot of oil on a compressor set) – same thing happened – within 20 minutes the filter was blocked. The operator was adamant that the same oil was being used in a different plant without issue. This nearby plant did not have an issue because they were in service for a couple of years with an old batch of oil and was using the new oil only to top-up. That is why the did not have an issue. It turned out the oil supplier had introduced a new additive to improve some quality and did not advise the operator. A 5-micron filter is very fine!

Flushing kits

Solar make very good quality special tools, but when it came to flushing kits they were not good. That was some time ago and maybe it has improved. The quality of what was supplied was OK, but there was always a need to make up additional hoses and fittings to get it to work. The flushing kits used in the manufacturing facility are very good and it is a pity the design of the flushing kits were not based on them. Attached is an example of what was needed to complete an oil flushing on a Titan some years ago.

ART226 – Solar Mars Lube Oil System

Donald Murphy — Tue, 09 Jan 2024 17:35:05 +0000

ARTICLE REF – ART226

Intro / Overview

The lubrication system is responsible for the cooling and lubrication of the Accessory Gearbox, Gas Generator bearings, Power Turbine bearings and the driven equipment bearings.

As all the principal bearings are tilt pad type bearings, there will be a large volume of oil required. With ball and roller bearings there isn’t as much oil required and therefore a small oil tank.

Typically on a Mars unit there will be a lube pump driven by the AGB, an AC motor diven pump for pre and post lube, and a DC motor driven pump for emergencies. There are units without mechanically driven pumps, that use two AC driven pumps, normally referred to as Auxiliary Pumps.

Oil will be regulated to the required pressure and kept at the required temperature by the oil cooler. Then passing through a filter before being delivered to the different areas of the equipment to lubricate and cool. Oil then falls by gravity directly to the oil tank.

The oil tank will contain approximately 5,000 liters of oil when full.

Normally viscosity VG-32 oil is use, but in locations where the ambient temperature are very high some operators opt for VG-46 oil.

This selection is not arbitrary and Solar Engineering need to evaluate this change if desired. This will be discussed a little further on.

Oil level
The oil level is displayed locally on a level gauge and also by a level transmitter which sends a 4 to 20 milliamp signal to the PLC.

Four milliamps is equal to 8.8 inch level of oil and 20 milliamp is equal to a level of 32.6 inches.

There is a low alarm at 19.32 inches and shutdown at 17.3 inches.

There is also a high alarm at 23.74 inches.

Oil heater
A three phase heater is used to heat the oil while on standby if necessary. While on standby (below lite off T5 temperature) the oil heater will be commanded on if the oil temperature drops to 75 degrees F, and cuts out when the temperature is 80 degrees F. It uses the Oil Tank RTD to control the temperature.

The heater will be inhibited if the lube oil pressure is less than 8 psi, the tank level is low or fire is detected.

This heater has a thermostat which will kill the power to the heater should the oil temperature reach 125F. This is an additional safety built into the control of this heater. If the PLC does not trip the heater, the thermostat operating independently of the PLC will.

Oil tank pressure:
The oil tank can become pressurized if one or more of the oil bearing seals are damaged or worn. Each seal on the Gas Generator and Power Turbine is pressurized with PCD or Eleventh Stage Air to prevent oil leaking into the airflow.

Bearing one at the front of the gas generator and bearing four of the PT is pressurized with 11th stage air. A small quantity of this air will flow through the labyrenth seals and return to the oil tank, as will the other seals.

On a compressor set sealing gas returns with the oil, which not only has pressure, it alos is a fire or explosion hazzard.

To prevent the tank from pressurizing and removing any explosive gases, the tank is vented to a safe place outside the enclosure.

The tank has a vent pipe connected to the top of the oil tank. Mounted alongside the vent pipe is a pressure differential transmitter that monitors the tank space pressure.
Alarm is set at 8.5 inches of water.
Shutdown is set at 10 inches of water.

Solar Oil Viscosity:
The most common oil viscosity used on Solar turbines is VG-32 with VG-46 being used in very hot climates. The viscosity of the oil is important, because it will determine the oil film thickness between bearing and shaft. The oil film thickness is important for heat transfer from the metal to the oil as well as lubricating qualities to reduce wear on the bearing and preventing elevated oil temperatures which will lead to oil oxidation which degrades the oil. The viscosity is measured in centistokes (cSt) which is a measure of a fluid’s flow.
If you think that a change of viscosity might help your operation, you would need to contact Solar Engineering, as there is much to consider. The basic thinking behind moving to VG-46 oil would be because it obtains its optimum oil film thickness at a higher temperature. The thicker the oil, the higher the VG number.
A Solar oil system is designed to run at a specific temperature to take advantage of the optimum oil film thickness. This is achieved by sizing the oil cooler, fan speed, temperature control valve to get the oil temperature where it needs to be.

Some items Solar Engineering will consider:
1) The thermal control element for the lube oil cooler needs to be changed.
2) The control set points, alarms etc. in the software will change.
3) Going from C32 to C46 is okay as far as the oil cooler is concerned. The other way, the oil cooler may be too small.

Lube system instrumentation:

Let’s take a look at the instruments of the lube system that interface with the PLC. First let’s look at temperature monitoring using Resistance Temperature Detectors “Called RTDs”

The temperature of the oil is very important because it needs to be kept at the design temperature for maximum cooling and lubricating, and to prevent oil degradation due to oxidation. The temperature of the oil at the different locations gives us an indication of pending or current problems.

The three bearing drain RTD monitor the oil leaving the different bearing areas. These bearings have labyrenth seals and the seals are pressurized with PCD or eleventh stage air. This air is very hot and when the seals are damaged or worn a high flow of this air will heat the oil. That is why you monitor these drains.

These are, “bearing one” which drains via the accessory drive gearbox. Oil from bearing two and three drain together and oil from the power turbine bearings four and five drain together.

There is an alarm on each RTD set at 250 Degrees Fahrenheit.

Also each sensor failure is annunciated if the temperature is less than 160 or greater than 400 Fahrenheit. The signal is considered out of range at these values.

There is also a differential alarm and differential shutdown on each RTD.

The Header RTD is used as a reference, and what the control is looking for is differential from this value. The temperature of the “Header RTD” is subtracted from the value of each drain RTD.
For bearing one and bearing four dash five (PT drain), there is an alarm if the differential temperature is greater than 45 degrees Fahrenheit, and there is a shutdown if the differential is greater than 50 degrees Fahrenheit.
For bearing drain two dash three there is an alarm if the differential temperature is greater than 110 degrees Fahrenheit, and there is a shutdown if the differential is greater than 125 degrees Fahrenheit.

LUBE OIL TANK RTD:

The oil tank RTD is used as one of the start permissives. Often the tank heater is locked out for maintenance and when it comes time to start back up, all the locks are removed only to realize that they have to wait for the oil to heat up before a start permissive is available.
The temperature for the start permissive depends on whether the oil is viscosity grade 32 or 46. Grade 32 is set to 68 degrees Fahrenheit and Grade 46 is set to 85 degrees Fahrenheit.

The tank oil temperature has an alarm set to 160 degrees Fahrenheit and shutdown at 165 degrees Fahrenheit for Grade 32 oil. Grade 46 is sent to 175 and 180.

The oil tank RTD also controls the tank heater “on off”.
With Grade 32 oil the heater comes on at 70 degrees Fahrenheit and off at 75 degreed Fahrenheit. Grade 46 is 90 and 95 degreed Fahrenheit.

LUBE OIL HEADER RTD:
The oil temp needs to reach 125 degrees Fahrenheit for C32 oil, 30 minutes after starter dropout speed.

Failure of lube header RTD means a Cool Shutdown.

The Lub oil cooler is controlled “on/off” by the lube oil header RTD.
With Grade 32 oil the cooler is turned on at 110 degrees Fahrenheit and off at 100 degrees Fahrenheit.

The header alarm is set to 175 degrees Fahrenheit and the shutdown is 180 degrees Fahrenheit.

Cooling Fan RTDs

Temperatures are only for display and are not found in the logic. They are used by the operator to evaluate the efficiency of the oil cooler.

NEXT LETS LOOK AT THE PRESSURE INSTRUMETS:

Pressure Switches:
There are different configurations of the Mars lubrication system, so therefore there will be different control logic and instrumentation. In this example there are three pressure switches.

The pressure switch on the main lube oil header is subject to bearing oil pressure. The switch activates at 8 psi decreasing, but it is not an input to the PLC. It’s wiring is connected to the turbine backup system. The backup system is a relay logic system which is used in case of PLC failure, to safely control the shutdown of the turbine and the post lubrication cycle of the lubrication system. If the PLC fails, the turbine will shut down. The Main Pump driven by the Accessory Drive Gearbox will loose pressure. The Pre-Post pump would normally be commanded on by the PLC, but if it has failed, it wont be commanded on. The pressure switch will change state and completes the backup pump loop command to start. At this stage the lubrication system is being controlled by relays and mechanical timers.

The pressure switch just after the DC pump is used to verify that the backup pump is capable of making 12 psi pressure. It is isolated by a check valve downstream of the pump, therefore the pump can be checked while the turbine is in service. A daily check of the backup pump is carried out at midday if the turbine is running. The backup pump is checked as part of the pre start checks. For this check the transmitter mounted on the lube oil header is used for pressure verification.

The pressure switch just after the Pre-Post lube pump can be checked while in service similar to the DC backup pump.

Pressure Transmitter Main Lube Oil Header:

The solid red line is the lube oil shutdown schedule pressure, in psi versus NGP speed. You can see that there is an 8 psi minimum pressure for startup permissive.

There is a maximum delay of 5 seconds before shutting down.

The alarm limit in red dotted line is 2 psi higher.

This is checked during the pre start checks to verify the pre post pump can supply minimum 8 psi.

Note that the mechanically driven pump will not be capable of creating enough pressure until the speed increases and until that timn the electrical pre post pump is in service.

Some turbines have two electrical pumps and no mechanically driven pump, so the logic will change some.

Thermostatic Control Valve.
The Thermostatic Control Valve controls the ampount of oil that flows through the oil cooler. It is important to remember that unless the cooling fan is rotating there isn’t any cooling. As the oil heats up, the oil starts to be diverted to through the cooler.

The control of the valve is done automatically using an wax filled capsule. It expands when heated opening the cooler port and closing the bypass port progressively until it is in full cooler position. All the oil has to flow through the cooler at this temperature.
For example a Solar Mars Thermostatic Control Valve, part number 120337-25 has an internal capsule which is replacable. This has a capsule that starts to open at 110 deg F and is fully open at 130 deg F.

The sketch on the left shows the TCV in bypass. None of the oil is flowing through the cooler. The oil flow is represented by the red lines. The oil flows out the bypass connection of the vlave.

As the capsule in orange starts to expand oil will flow through both the bypass and the cooler connections. In our case with a 120337-25 valve, the oil starts to flow through the cooler at 110 degrees Fahrenheit and the flow through the bypass connection will be fully closed at 130 deg Fahrenheit.

The capsule used will depend on the viscosity of the oil used.

DC Contactor:

The purpose of the DC Pump starter is to safely control the DC backup pump. It was introduced around 1990 as some companies felt there was a risk of fire due to the pump not being monitored and protected.
Some people feel that this system is over protecting the pump and sarcrificing the turbine.
It is true that there are some weak links and more things that can go wrong to cause the backup pump to fail.

The components in the starter are:
The Disconnect Switch – this can be rotated / controlled from outside the box.
Line Fuses – protect from short circuits and high loads.
Relay M – this is the main motor contorl for the pump.
Relay CR – this is the on/off control relay from the PLC and backup system.
OL – these are thermal overloads – current heats the sensor and opens it if too hot. This is an indication of over load on the montor. Loose connections will have the same result!!!!!
1A is an acceleration contactor to give the motor a soft start.

Pump logic

Pre Start Logic: cold engine start or test crank.
Oil level and temp is checked.
Backup pump is turned on and pressure is checked and has to be greater than 8 psi for 5 seconds.
The pressure needs to decay within 30 seconds to indicate pump is turning off – otherwise an pump alarm will annunciate.
AC pump turned on and checked for min pressure of 8 psi for 5 seconds.
This pump stays on until the engine driven pump takes over or stays in service if there are only electric driven pumps.
The oil pressure while in servcie was allready discussed. The alarm values vary with speed.

Post lube 4 hours.

Post lube required once the NGP speed is greater than 65%.

In the event of a fire the lube system operates during the coastdown. Then it is turned off for a maximum of 20 minutes before resuming post lube.

If the pressure drops on the post lube below 8 psi the backup pumps comes on.

The backup pump comes on for one hour continuous and then cycles on off for the next three hours. 2.5 / 9.5 minutes on off.

If there is case pressure in the compressor the lube pump is commanded on. The reason being that the compressor may spin if the vent valve opened to depressurize the compressor.

Both the thrust bearings are also monitored. The maximum temperature allowed is 250 degrees Fahrenheit. There is also a differential shutdown. A maximum of 100 degrees Fahrenheit difference between the bearing supply temperature and the thrust bearing.

END

ART223 – Solar – Mars Lube System – Video Part 1

Donald Murphy — Fri, 15 Dec 2023 21:09:55 +0000

ARTICLE REF – ART223

ART111 – Solar – Titan 130 Oil leak

Donald Murphy — Sat, 25 Sep 2021 12:41:37 +0000

ARTICLE REF – ART111

Question from Solar Turbines Linkedin group ………

Has anyone had an oil leak in the bearing 2/3 on the titan 130? The red line shows where the oil leak is occurring and the blue line seal air taken from axial compressor last stage. There is no vibration problem in the gas turbine.

Two-shaft Titan 130 slow roll within the current 3-5% NGP range with the bleed valve open can result in oil leakage from the number two and three bearings. The amount of leakage varies. The root cause of the leakage was found to be insufficient buffer air flow across the labyrinth seals. Engine tests and resulting pressure measurements have aided in determining the optimum slow roll speed to avoid oil leakage. In addition, it was determined that the bleed valve as well as the guide
vanes must remain closed during slow roll.

The recommendation from Solar for units with this problem mentioned above is “at the next opportunity, the following should be accomplished for affected units to avoid bearing leakage”
1. Set the slow roll speed range to 12-15% NGP.
2. Correct the bleed valve schedule for units with a 6 inch bleed valve.
3. Ensure bleed valves remain closed if acknowledge/reset is selected when stopping.
4. Configure the system to allow the unit to be started when slow roll is in progress.

Typical sources of oil leaks:
High Pre/Post lube oil pressure.
Number 1 seal air leaking or not connected.
Damaged o/ring on the number 2/3 oil transfer tube tip – o-ring can be replaced on site.

To determine the source of the leak:
Wash the turbine of any residual oil.
Disconnect the supply to Number 2-3 bearing and run the pre post pump to see if there is a leak at the Number 1 bearing seal.
Reconnect the supply to Number 2-3 bearing, disconnect the supply to Number 1 bearing and run the pre post pump.

End or article.