Cats aren't the only thing that can't stand water, your gearbox can't stand it as well. Unfornately for gearboxes, water is used in every industry and is one of the leading causes of machine failure. It is a silent killer, it can take a long time to cause noticeable damage, but when the signs do appear, it is usually too late.
Water contamination can cause:
- Shorter component life due to rust and corrosion (gears and bearings). - Hydrogen embrittlement happens when water invades microscopic cracks in the metal surfaces. Under extreme pressure, water decomposes into its components and releases hydrogen. This explosion forces the crack to become wider and deeper, leading to spalling. - Film strength loss - the pitch line of a gear tooth is protected because oil viscosity increases as pressure increases due to the oil's pressure/viscosity coefficient. Water does not possess this property. Its viscosity remains constant (or drops slightly) as pressure increases. As a result, water contamination increases the likelihood of contact fatigue (spalling failure).
It's affect on gear oil:
- Water accelerates oxidation of the oil. - Water depletes additives like oxidation inhibitors and demulsifiers. - Water causes ZDDP anti-wear additives to destabilize over 180°F. - Competes with polar additives for metal surfaces.
Types of Water
There are three states of water contamination: dissolved water, free water or emulsified water. When talking about gearbox reservoirs, all three states of water can cause serious damage. Free water and emulsified water specifically are the most harmful states in any lubricated system.
Dissolved Water
Dissolved water is like humidity in the air. The water or moisture is present but dispersed throughout the oil, molecule by molecule, making it almost impossible to detect with the human eye. With a high concentration of dissolved water, you might see condensation start to build. Dissolved water is what causes any part not coated in oil to start rusting, promoting further oxidation and contamination down the road. As the concentration or saturation of dissolved water builds, it will turn into free water or emulsify with the oil.
It is important to remember that you can have both free and emulsified water in the same sump.
Free Water
We all know water and oil do not mix well together. Water is usually heavier than oil and will sometimes settle out in the bottom of the sump. This is what we refer to as free water. If caught early enough, free water is the easiest form to remove from a sump or reservoir. Installing a bottom sediment and water bowl or column sight glass on the drain port is a good way to keep a constant eye on water contamination. Free water buildup can cause serious problems, with oil levels eventually filling up and either overflowing or causing the gears to now operate with water and oil causing emulsification. If water is allowed to mix around in the oil, it can cause foam and become suspended within the oil, emulsifying and causing serious viscosity changes which then results in boundary conditions and eventual machine failure.
Emulsified Water
Water/oil emulsification occurs when free water and hot oil are agitated together. The oil and water become mixed, leading to increased viscosity, loss of film strength, additive washout and lubricant failure. Viscosity is the most important physical characteristic of an oil. When free water is allowed to become emulsified, the viscosity will go up and machines will start working harder, become hotter and machine parts will fail. Emulsified water is almost impossible to fight with filtration. It is important to catch the problem during the free state to prevent emulsification. Failure due to water contamination may be catastrophic, but it may not be immediate. Many failures blamed on lubrication are truly caused by excess water contamination.
Water Contamination Causes
The most common cause of water ingression or contamination is through open ports/hatches, shaft seals, flange fittings and cooling systems. However, all oils will have a traceable amount of water in them. It is important to test new oil coming in, so you have a baseline or starting point - something to use as a reference if a problem does arise. Studies have shown that new oils are not clean and sometimes not dry. By testing new oils or oils that have been stored for an extended amount of time, you can obtain an accurate baseline not only for water content but also for a particle count to determine overall cleanliness.
Manage Stored/New Oils
Prevent water from entering new oil by storing drums indoors. If they must be stored outside, keep them in a shed or under a tarp, or store them on their sides. Drum and tote mounts like Checkfluid's DT Adapter will enable you to sample, monitor, and filter the oil while it is stored. The DT Adapter will also let you cleanly transfer your oil from a storage container to the machine.
Some of the ways to keep an eye on water contamination are:
Oil Analysis
Oil analysis is a key way to monitor the amount of water in the oil. Remember, oil analysis is depended on a representative oil sample. The goal is to get a sample from as close to the active zone as possible, to achieve this, select a sampling tube that has a permanent sampling tube. The permanent sampling tube ensures that the oil sample is pulled away from the bottom or side sediment. For sampling gearboxes Checkfluid recommends the LT or LTJ Series. Both series use Checkfluid's high flow L style sampling valve, and come standard with a 1/4" OD, 12" sampling tube. The LTJ has a comes with a standard swivel which allows you to easily position a bent tube.
Condition Monitoring
Checkfluid's AD Drain Mount allows you to add sight glasses & BSW bowls for a quick visual indication of oil condition. BSWs also allow you to drain out any free water located in the bowl. Moisture sensors can also be installed to measure the moisture in the headspace of the reservoir as well as moisture in the oil.
Checkfluid's AD Drain Mount
Controlling Water
Controlling water contamination can be accomplished in a variety of different ways. A simple solution is mouting a desiccant breather on the headspace. Desiccant breathers allow the air entering equipment to flow through the desiccant media, stripping out any moisture and trapping it in the desiccant media before entering equipment. Checkfluid's AB Breather Mount will let you add a desiccant breather, filter guage, and quick coupling for filling & filtering.
Checkfluid's AB Breather Mount
Removing Water
There are several methods to efficiently remove water from the lube systems. The following table from Machinery Lubrication provides a general rating of the ability of each technology to remove free, emulsified, and dissolved water.
Water generally has a high density (or specific gravity) than most lubricants. Free water settles at the bottom of the reservoir and can be easily removed by regular oil draining. The effecitiveness of oil and water separation can be improved by a larger reservoir sidze and higher fluid temperature. Checkfluid has a new Bottom Fluid Retriever (BFR) that can be used to remove water from the deep bottom of tanks. You can also replace the water with the required oil amount to maintain adequate lubrication.
Checkfluid's Bottom Fluid Retriever
Filter Carts
Portable filter carts can also be used to remove free and emulsified water. These carts can be fitted with water absorbing filter elements. However, they gace a lower capability of water removal in comparison with other systems.
Stop Water First
The cheapest and most effective method of controlling water is simply stopping water from entering the machines or making contact with the machines in the first place.
Invest & inspect to save money:
- Invest in splash guards around equipment, make sure ports and hatches are sealed tight, and train people on how to carefully spray down an clean equipment
- Inspect shaft seals for damange and replace damage seals if necessary
- If equipment is outside, building rain covers or redirecting the drain water away from equipment can also help mitgate water contamination problems
It will be much cheaper and easier to protect equipment from water ingression than to remove water after it's inside the system.
