Not On Stuffing Box Oil Filtration

At a slow speed, 2 stroke engines the primary concern is to have proper sealing between the combustion area and the crankcase. The crankcase is separated from the cylinder and scavenge space by the diaphragm plate on a two-stroke crosshead engine so a provision must be made for the piston rod to pass through the plate without oil from the crankcase being carried upwards, or used cylinder oil-contaminated from products of combustion being carried downwards. It is also highly undesirable to allow the pressurized air in the scavenges space to leak into the crankcase.
The Piston rod passes through a stuffing box and is bolted into the diaphragm plate. The stuffing box casing which can be split vertically, as shown in the photo, contains a series of scraper rings and sealing rings which are each made up of three or four segments. On the outside of each set of segments is a garter spring which provides the tension to hold the ring segments against the piston rod. There is a clearance between each segment to allow for wear. The rings are either bronze or can comprise of replaceable cast iron lamella fitted into a steel backing ring.
As the Piston rod passes up through the stuffing box, the oil from the crankcase is scraped off by the lower sets of rings and is returned via drillings to the crankcase. Any oil that passes this primary set is scraped off by another set of rings and is led away through a drain to a telltale open-ended pipe into a dish outside the engine from where it drains to a recycling tank.

As the piston passes down through the stuffing box, the top set of scraper rings will scrape off the contaminated oil into the bottom of the scavenge space, where it is drained away via the scavenge drains. However, if these rings are faulty, then the oil may drain into the recycling tank.
By observing the open-ended telltale referred to above, a guide to the condition of the rings can be ascertained. If a large quantity of oil is draining out, then the lower set of rings is faulty. If air is blowing out, then the upper rings are worn.
Oil in the recycling tank can be purified back to the crankcase. Filtek portable oil filtration unit is capable of fine filtration of this contaminated oil which can be used for recycling. Filtek offers a complete centrifuging system with tank, level switches, heater, 1-micron polish filter, and a transfer pump for transferring the filtered oil to the crankcase.

Oil Filtration Unit
However, care needs to be taken on the overall oil viscosity if the cylinder oil if mixed with the crankcase oil. It may be contaminated by used cylinder oil which if mixed with crankcase oil causes an increase in viscosity of the crankcase oil. Calcium deposits in the bearings lead to damage and the oil may carbonize and deposit on the underside of the piston crown when used as a piston coolant. Often this contaminated oil is just landed ashore or burnt.
Regular maintenance of the stuffing box will keep it in good condition. checking garter spring tension, ring butt, and axial clearances, and replacing worn rings are all part of the overhaul procedure.
Excessive wear will take place if the crosshead guides are out of alignment or if the guide clearances are excessive. Worn stuffing boxes and excessive leakage can exacerbate the incidence of scavenge fires and increase the risk of a crankcase explosion.

Stuffing Box Schematics

 

centrifugal-oil-cleaners-ft600-2

Centrifugal Oil Filter Working Principle

CENTRIFUGAL OIL FILTRATION – PRINCIPLE OF OPERATION

Filtek Centrifugal Oil Cleaner consists of 3 major sub-assemblies as follows:

1. Base assembly made in die-cast Aluminum
2. Rotor Assembly made in die-cast Aluminum
3. Cover Assembly made in Press MS

The lube oil from a pressure point on an engine is fed through the side inlet of the Centrifuge. The cut-off valve (COV) is rated between 1.3 to 2.5 BAR as per each situation. When the oil pressure exceeds the set value, the spring-loaded plunger in the COV assly is pushed back allowing entry of the oil . to enter the rotor assembly through the internal drill hole of the central spindle. The rotor assembly gets pressurized and the only exit point for the oil is the two tangentially opposed nozzles at the base. The rotor assembly has two bush bearings, one at the top and one at the bottom and it spins freely around the spindle.

The action of oil exiting through the nozzles gives it a reverse direction spin. The rotor RPM is directly proportional to the inlet pressure. The oil is returned back under gravity through the central hole at the base of the centrifuge. At 6 BAR pressure, the high RPM generated results in centrifugal force 2000 times that of gravity. Thus any particle heavier than oil is compacted onto the inner rotor wall. At pre-determined intervals, this can be easily cleaned with the help of a wooden spatula or a specially coated, nonstick paper insert.

The centrifuge has no consumable parts and is capable of removing sub-micron particles from the oil. The minimum operating oil pressure should be at least 4 BAR but not exceeding 7 BAR to get optimal results.

FILTEK GR-300 FILTRATION SKID

Wind Turbine Gearbox Oil Cleanliness

Proper and long term functioning of the Gearbox is very critical and depends mainly on the quality of oil cleanliness. Gearbox failures are primarily a result of oil contamination due to ingress of dust, metallic wear on account of friction, water contamination resulting in the change of oil parameters, oil degradation, and excess vibrations leading to probable surface cracks, misalignment of pump+motor shaft. Wind turbines being placed in remote locations, regular monitoring of oil condition assumes importance. Choosing the right amount to invest in contamination control to optimize your return on investment should be the goal. The ideal ISO Cleanliness Code for oil in gearbox is 16/15/12 and water content < 500 ppm. This ensures a very long life of the gearbox which is typically 15 years to 20 years. The ISO Code 16/15/12 means the following:

Particles/ml as per Size Range number 16 Range number 15 Range number 12
4 micron > 320 and < 640 – –
6 micron – > 160 and <320 –
14 micron – – > 20 and < 40

 

Usually the online oil filtration system has a 50 + 10-micron cartridge in the lube circuit. The Gearbox oil is checked every 6 months with a complete change every 24 months.

In a wind-turbine gearbox, the most common gear-oil viscosity is ISO 320 which is calculated at 40°C and reported as centistokes (CST). If the viscosity decreases beyond permissible limit, the oil is shearing and there is potential for reduced oil-film thickness, resulting in increased wear. If the viscosity increases, it may be due to oxidation by-products which can be associated with oil degradation and shortened filter and oil life.

It is a well-known fact that it costs at least 10 times more to remove a gram of dirt than it would exclude it in the first place Even in a very tiny amount, contaminants can increase operating costs associated with maintenance expenses or gearbox replacement. The main contaminants affecting oil and gearbox life are water, wear particles, and dirt. Along with additive depletion, water can cause filter plugging, sludge formation, reduced oil-film thickness, and be difficult and expensive to remove.

As a general rule, it is accepted that water is detrimental in wind-turbine gear oil. A 0.05% presence of water in oil equates to a 58% reduction in bearing life. However, filtration from 10 microns to 3 microns will increase bearing life by 50%. This allowable presence of water in the oil limit ( ppm ) varies with acceptable levels from 0 to <500 ppm.

Each oil type has a different starting point for total acid number (TAN) which is directly associated with additive content. A general rule is to condemn the oil when the TAN increases more than two points higher than the initial TAN. In this case it is best to consult your oil supplier for the new oil-TAN value and used the oil-condemning limit. If the TAN increases and exceeds the condemning limit it may be an indication the oil is turning corrosive and may contribute to depleted additives and increased wear.

Filtek has recently introduced a 1-micron microglass filter which can be used in offline mode to maintain the required ISO cleanliness of gearbox oil. Additionally, a high powered rare earth magnetic chamber captures all the metal particles in oil as shown in the below picture.

HF-60 Skid

Hydraulic Oil Cleanliness

The importance of Hydraulic Oil Cleanliness cannot be emphasized enough and is vital for the continuous running of all machinery/equipment utilizing hydraulic oil. Preventive maintenance is planned maintenance designed to prevent equipment breakdown resulting in huge costs of downtime and repair. Taking active steps to keep equipment in good condition is usually a more efficient and cost-effective solution than repairing or replacing equipment after it breaks or fails.

Hydraulic Systems work under extremely high oil pressure usually in excess of 200 BAR with very small oil film thickness/clearances between friction parts. The cleanliness of oil plays a very vital role in extending the life of friction components, maintaining the oil pressure and life of the equipment.

One-half teaspoon of dust contains enough particles to contaminate 55 gallons of hydraulic fluid state most OEMs. Even fresh fluids will not meet these cleanliness targets. Testing shows that component life can be extended up to 30% when fluid cleanliness is improved by a single ISO Code. A recommended practice is to subject new oil to a filtration process prior to being deployed in hydraulic tanks/machinery. When tiny abrasive particles such as sand and dust get into the oil system they flow with the oil into critical machine components and are wedged in the fine clearances. Excessive amounts of particles cause stress on the additive package in the oil. The detergents and dispersants may get depleted if the particle contamination is not taken under control.

Leaders in the hydraulic equipment industry have determined that the majority of system failures can be traced back to abrasive particles that cannot be seen with the human eye. Component life and operating costs can be improved by achieving fluid cleanliness in hydraulic systems.

Typical Parts Clearances are (a) Piston Pump 0.5-5 μm (b) Vane Pump 0.5-13 μm (c) Gear Pump 5-40 μm


Filtek HF Hydraulic Filtration Skids are very effective in maintaining oil cleanliness to industry acceptable standards. The magnetic conditioner aids in effectively removing all ferrous particles from the oil prior to entry into the oil pump. The microglass depth filter with an oil flow of 1-3 LPM removes all solids and insoluble. The evaporation chamber heated to 80 deg C is helpful in venting out all moisture from the oil into the atmosphere. This compact skid with pump+motor, control panel with fittings weighs only 40 Kg and can be easily transported between various hydraulic tanks.

For more information visit our website www.filtekfiltration.in

FT060 skid

Filtek Centrifugal Bypass Lube Oil Filtration System

All diesel engines have a primary lube oil filter which is installed between the engine oil pump and the engine components. This is always a barrier cartridge type filter rated at 40 to 80 microns to stop the larger size particles going to the engine components. (see fig 1). Filtek Centrifugal Oil Cleaner fitted in the bypass lube oil circuit of the engine has been found to be extremely effective in removing carbon soot, wear metal particles, inorganic and organic particles down to 1 micron without affecting the oil pressure or flow of oil to the engine (see fig 2)

Recently in the past 10 years engine manufacturers have started to realise that the wear and tear of friction components of the engine such as bearings, piston rings and liners, turbo bearings valve guides etc happens due to the smaller particles less than 5 microns.(see fig 3)

The only way to capture these tiny particles between 1 and 5 microns is with a very high centrifugal force, nearly 2000G. The dirty oil enters the centrifuge under engine operating pressure, enters the rotor chamber, is expelled via the 2 nozzles at the centrifuge base to eventually return through the crankcase into the lube oil sump. The action of oil exiting through the nozzles gives the rotor a reverse spin directly proportional to the inlet pressure. Speeds to 6000 RPM can be achieved creating tremendous centrifugal force on the particle to separate contaminants from the oil, on the inside rotor wall. (see fig 4)

The Filtek Centrifugal Oil Cleaner is installed on the crankcase cover of the engine. Only 10% of the oil flow capacity of the pump, is taken from the oil cooler inlet or the lube oil filter assembly and sent to the oil sump via the centrifuge. (see fig 5)

Advantages of fitting a Filtek centrifuge are 

  • Removal of contaminant to 1 micron will increase Engine oil life by min 50%.
  • Fully cleanable unit so no consumable costs to enduser.
  • Environment friendly as contaminant is bio degradable.
  • Increase in engine life by at least 25%.
  • One time cost effective investment for life of the engine.
  • ROI considering the above is less than 3 months.

Statements by marine engine manufacturers

CAT STATEMENT

Bypass oil centrifugs extend oil filter change periods. They mount on the side of the engine and can be changed with the engine running

YANMAR STATEMENT

The engine-mount centrifugal bypass filter is effective in controlling lube oil contamination of the engine being operated. In particular, in the batch treatment system, since circulation purification of lube oil is not conducted during engine operation, equipment of the centrifugal bypass filter is indispensable.