Compressor Lubrication: Best Practices
You may know how important compressor lubrication is to compressor components, but are you aware of the best lubrication practices? To ensure a well functioning compressor, read more below.
Compressor lubrication practices are employed to ensure that the internal components of these machines are fully functional for a long time. These components are not limited to bearings, gears, and seals.
What’s more, the lubricant you use has to meet certain criteria for it to be the best to serve the compressor. And we’ve outlined what these criteria are.
The same applies to the compressor’s lubricating oil system operation to give a better understanding of what happens to your machine once it’s filled with oil.
What is a Compressor?
A compressor is a mechanical device that improves the pressure in a fluid such as air, and a list of other gases, by reducing its volume.
There are dynamic compressors that operate by exerting velocity energy on a stream of gas. The velocity energy is then transformed into pressure energy.
Compressors feature various internal components and these machines need lubricants or coolants to oil their components. There are, however, exemptions given that some type of compressors do not need to be lubricated.
Dynamic compressors, for instance, have to be lubricated, whereas static jet compressors and oil-free compressors that feature rotors suspended in magnetic bearings do not have to be lubricated.
On the other hand, if you’re using a dynamic compressor, let’s show you what’s required to lubricate it.
Components of a Compressor
Dynamic compressors feature several components that need a lubricant to operate them seamlessly. Some of these components include bearings, gears, and seals.
There are a good number of dynamic compressors that rely on oil film-lubricated seals.
Nonetheless, there are gas-lubricated seals or labyrinth seals that do not necessarily need a liquid film on their surfaces.
Premium-grade turbine oils whose ISO viscosity grades are around 32 or 46 are ideal for use on a good number of compressors.
Needless to say, manufacturers may specify the best oil to use in the compressor given that these machines vary. The manufacturer’s recommendation may have also been used at a test stand and controlled user facilities.
Nonetheless, a turbine oil that is employed instead of oil grades with heavier viscosity is the premium-grade ISO VG 32. The usual viscosity index is 97 and it often has a pour point around -37ºC (-35ºF).
Also, the oxidation stability (per ASTM D943) should not be above 5,000 hours. The flashpoint (per ASTM D92, COC) should BE AROUND 206ºC or 403ºF.
And if you settle for these lubricants, they should be able to offer the following:
- Good foam control.
- Long-life without requiring a changeout.
- Preventing sludge, deposit formation, and acidity.
- Protect against corrosion and dust, even during a shutdown.
- Good demulsibility to eliminate the water that enters into the lubrication system.
On the other hand, these compressors may operate for a long time after the first fill with oil. They may operate as long as three decades.
This long term lifecycle is due to the premium-grade product selection, good contamination control, large sumps, amongst other measures taken.
What’s more, the turbine’s extended lifecycle, as well as the turbo-compressor, are aided by the simple additive structure of the product.
This structure reduces the various complications that are linked to complex additive systems including those found in EP gear lubricants.
There’s an oil face seal that relies on a spring-loaded stationary carbon ring that is in sliding contact with a rotating ring. The ring must be made from a material with high quality and remarkable finish.
Also, a seal of this nature is ideal when the compressor is in a standstill and there has been a shutdown of the oil pumps.
What’s more, two stationary breakdown bushings that have small diametral clearances opposite a shaft sleeve are the major components of oil bushing seals.
Here, the flow of seal liquid that cools the seal is controlled by the floating ring clearance. The floating ring clearance controls the flow of the seal liquid cooling the seal.
There are floating carbon seals and they also need seal face lubrication.
Compressor Lubricating Oil System Operation
The lube oil system helps to transfer oil to the compressor and the driver bearings. The oil is also sent to the gears and couplings.
In line with that, the lube oil is taken from the reservoir by the pumps and it is sent under pressure to the bearings using coolers and filters.
And once the oil exists from the bearings, it can drain into the reservoir again.
On the other hand, the reservoir is created in a way that will allow circulation of the whole fluid volume between eight to twelve times per hour.
Also, the oil reservoirs have thermal sensors that aid in monitoring the level of temperature during startups and regular operations.
Coupled with that, the reservoir features oil temperature controls, and these controls to aid in preheating in cold start-up conditions.
It also aids in cooling to keep overheating that may occur during peak operating cycles at bay.
Compressor Lubricant During Unit Operation
The main oil pump circulates a compressor’s lubricant during operation. There’s also an auxiliary pump that serves as a backup, and these pumps feature different drives or power sources.
Also, as the two pumps are driven electrically, different supply feeders are used to connect them.
In compressors that have step-up gearboxes, the main oil pump could also be driven electrically right from the gearbox.
The auxiliary pump can also operate during the start-up and run-down stages of the compressor train.
These are the best compressor lubrication practices that will ensure you use the best grade oil for your compressor.
Much more, different compressors have an oil grade that is ideal for them which makes it needful to adhere to these practices. It’ll ensure that you choose an oil that does not have to be changed so frequently, and one with the highest quality.
The lubricant will also be able to keep rusting at bay in the internal components of your units.
Now it’s up to you to adopt these practices to maintain the high-level performance of your compressor for a long time.
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