Hydraulic oil filtration system
 
"What micron filter should be used to filter a 220 gear oil? We are looking into getting a filter cart to filter the oil while the machine is running."

First, determine the optimum target cleanliness level for that specific gearbox, and the do not forget to ensure adequate breathers are fitted, as any attempts at clean-up will be lost quickly. A few tips on filter carts:

First, ensure that for each type of lubricant in use, there is a dedicated filter cart to avoid cross contamination of fluids. 

Second, because this is fluid power generating device, ensure it complies with all the safety requirements and has a pressure venting safety valve in the event of dead-heading the pump. 

Third, ensure the cart includes a by-pass loop to the filters, and incorporates a sampling connector for the use of online instruments or bottle sampling. The design (pump and filter selection) of filter carts is dependent on two factors; the lubricant's viscosity grade, and the temperature at which the cart will be used. A higher viscosity, such as an ISO VG 220 oil, will require a lower flow rate in the pump to avoid high differential pressures across the filter. But this will be affected by the ambient and operating temperatures.

While the use of quick connectors allow the cart to be used while the gearbox is operating (this is the optimum filtering condition), the lubricant's viscosity will also be affected by the ambient temperatures, so if this is located outdoors, assume the worst case winter temperature when looking at the viscosity issue. Of course, slowing the flow rate to avoid high differential pressures will increase the time to filter the box, and depending on the Beta ratio, the rule of thumb is to allow the volume of the gearbox to circulate seven times through the filter for effective clean-up. For example, a gearbox with 50L sump capacity and a filter cart with a 10L/min flow rate will take five minutes for one pass and approximately 35 minutes to clean up. Keep in mind the flow rate versus the time available for filtering.

As to the filter rating, experience has shown a 10 micron filter capable of achieving better than ISO 17/15/12. However, if your optimum target cleanliness level is lower than this, consider a 6 micron filter. There are various ways to strike an optimum balance between flow rate and filter rating, and this includes the possibility of putting several filters in parallel to increase the flow area. As a simple guide, the differential pressure can be halved by doubling the length of the element or putting two elements in parallel. 3 micron filters will work with ISO VG 220 oils, but check the temperature conditions, and whether your target cleanliness levels require such fine filters. The cost of these elements should be considered.


By Noria

Find more  oil filtrationoil purificationoil treatment, oil purifieroil recyclingoil filters

 
 
  •  When selecting filtration for high-viscosity gear oils, you should first determine the optimum target cleanliness level for that specific gearbox and ensure adequate breathers are fitted, as any attempts at cleaning the oil will be lost quickly.

  • Ensure that for each type of lubricant in use, there is a dedicated filter cart to avoid cross contamination of fluids.

  • Because filter carts are fluid power-generating devices, ensure they comply with all the safety requirements and have pressure venting safety valves in the event of dead-heading the pump.

  • Ensure the carts include a by-pass loop to the filters, and incorporate a sampling connector for the use of online instruments or bottle sampling.

  • The design (pump and filter selection) of filter carts is dependent on two factors; the lubricant's viscosity grade, and the temperature at which the cart will be used. A higher viscosity, such as an ISO VG 220 oil, will require a lower flow rate in the pump to avoid high differential pressures across the filter. But this will be affected by the ambient and operating temperatures.

  • While the use of quick connectors allow the cart to be used while the gearbox is operating (this is the optimum filtering condition), the lubricant's viscosity will also be affected by the ambient temperatures. So if the gearbox is located outdoors, assume the worst case winter temperature when dealing with the viscosity issue.

  • Of course, slowing the flow rate to avoid high differential pressures will increase the time to filter the gearbox, and depending on the Beta ratio of the filter, the rule of thumb is to allow the volume of the gearbox to circulate seven times through the filter for effective cleanup. For example, a gearbox with 50L sump capacity and a filter cart with a 10L/min flow rate will take five minutes for one pass and approximately 35 minutes to clean up. Keep in mind the flow rate versus the time available for filtering.

  • In regards to filter rating, experience has shown that a 10 micron filter is capable of achieving better than ISO 17/15/12 oil cleanliness level. However, if your optimum target cleanliness level is lower than this, consider a 6 micron filter. There are various ways to strike an optimum balance between flow rate and filter rating, and this includes the possibility of putting several filters in parallel to increase the flow area.

  • As a simple guide, the differential pressure can be halved by doubling the length of the element or putting two elements in parallel. 3 micron filters will work with ISO VG 220 oils, but check the temperature conditions, and whether your target cleanliness levels requires such fine filters. The cost of these elements should be considered.

  • Electrical power considerations include the use of single or three phase, and the availability of power sockets near to the equipment, as well as ensuring that the unit is intrinsically safe for use in potentially explosive areas.

  • Finally, consider using water-absorbing elements if the gearbox suffers from free and emulsified water, in addition to the use of desiccant breathers.

 
 
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If you recycle just two gallons of used oil it can generate enough electricity to run the average household for almost 24 hours.

Cars are an indispensable fact of life for most of us. So, too, are abundant and clean supplies of drinking water. What we do with the used oil from our cars plays an important role in balancing our desire for convenient transportation with our desire for a clean and healthy environment today and for future generations.

We are all familiar with recycling newspapers, aluminum cans, glass and plastic bottles, but you may not be aware of the efforts of the petroleum industry and other groups to promote used motor oil recycling: providing convenient collection sites for the purpose of keeping used motor oil out of our waterways and ground water supplies and getting used oil into the recycling system.

Motor oil has value even after it has been drained from an engine. The oil you take to a collection center to be recycled saves energy. It can be reprocessed and used in furnaces for heat or in power plants to generate electricity for homes, schools, and businesses. It can also be sent to a refinery that specializes in processing used oil and re-refined into lubricating base oils that can be used to formulate engine oils meeting API specifications.

What can you do? If you change your own oil, be certain that you take it to a collection center for recycling. If you take your car to an automotive service outlet, you can be fairly certain that they recycle the oil that they change. But if you're not sure, ask.

Used motor oil that is collected by "do-it-yourselfers" is critical to the used oil recycling system. Next time you change your own oil, remember, you can make a difference by recycling the oil from your car, truck, motorcycle, boat, recreational vehicle or lawnmower. By dropping off your used motor oil today you help prevent pollution and conserve energy for a safer and healthier tomorrow.


 
 
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Listing requirements for less-flammable liquids

In discussing the requirements of various codes on the installation of transformers using less-flammable liquids, you'll encounter a requirement to comply with the listing of the liquid. Due to this requirement, it's important that you understand the various listing agency requirements for these units. In our discussion here, the use of the term "listing" or "listed" follows the basic definition from the National Electrical Code (NEC). This definition reads as follows:

Listed: Equipment or materials included in a list published by an organization acceptable to the authority having jurisdiction and concerned with product evaluation, that maintains periodic inspection of production of listed equipment or materials, and whose listing states either that the equipment or materials meets appropriate designated standards or has been tested and found suitable for use in a specified manner.

Less-flammable liquids are currently listed with Underwriters Laboratories (UL) and FM.

Factory Mutual. FM recommends certain practical and effective mechanical and electrical protection schemes for particular types of transformers. Fire protection is a base level of protection that FM requires for transformer installations that expose buildings or other property to potential damage. However, FM also gives consideration to omitting fire protection if the transformer installed is a less-flammable type with proper electrical and mechanical protection and if it is not installed as a network transformer.

Protection systems should be determined by an engineering study that considers the criticality of the supplied loads and the level of fire exposure that may be presented by a transformer failure. Various schemes of electrical protection can be employed from normal overcurrent protection to the inclusion of differential relays, ground relays, etc. FM's guidelines give varying degrees of overcurrent protection required based upon the transformer kVA and the supply configuration.

Per FM, all indoor transformers should be installed at least 3 ft from building walls, and containment systems should be provided for the transformer liquid in case of tank rupture. The containment area should be capable of containing the liquid from the largest transformer located within the space.

For transformers that are FM approved, the following elements are required in order to install the transformer without additional fire protection:

* Tank design strength to prevent tank rupture under low energy fault conditions;

* A pressure relief device to relieve pressure if a low current fault occurs until it can be cleared by the electrical protection;

* Electrical protection in the form of a ground fault relay, sudden pressure relay, or other device of equivalent reliability to clear sustained low current faults;

* A liquid with a firepoint greater than 300 [degrees] C; and

* Electrical protection to clear high current faults. This protection is based on the liquid volume of the transformer and is intended to electrically isolate the transformer [TABULAR DATA FOR TABLE 2 OMITTED] rapidly enough to prevent pressure increase to greater than half the tank burst pressure.

If the transformer is used on a network system, FM also requires that the transformer be installed in a room with a 3-hr construction or a room with 1-hr protection and automatic sprinkler protection.

For transformers installed outdoors, you must give some additional considerations to their location based on the insulating liquid used. In general, FM requires that they meet the above items outlined for indoor transformers and, in addition, the building should be protected by separation, fire barriers, or a water spray system.

The separation distances are shown in Table 1 (on page 80). These values show the varying degrees of separation needed between a transformer and an adjacent building. The distances increase depending on the fire hazard introduced by the volume of liquid in the transformer and the liquid type.

If the separation shown in Table 1 cannot be maintained, a fire barrier should be provided to protect the building from exposure to the fire. Fabricated barriers should be constructed of concrete block or reinforced concrete construction with a 2-hr fire rating. This barrier should extend beyond the transformer by the horizontal or vertical distances shown in Table 1.

If a building wall is used as the fire barrier, the exposed wall should be fire-resistive or noncombustible construction for transformers with less than 500-gal fluid capacity. For transformers with more than 500-gal capacity, the building wall should be of 2-hr fire resistance. In all cases, the wall should extend the horizontal and vertical distances specified in Table 1 from the transformer.

A water spray system may be provided for additional protection provided it has a discharge density of .20 gal/min over the exposed surface.

UL listing requirements

Significant revisions in the Factory Mutual Transformer Loss Prevention document in October, 1994 resulted in FM adopting a protection scheme similar to the original UL requirements. FM dropped requirements based on heat release rate and incorporated protection against tank rupture. Now, both UL and FM use mechanical and electrical protection combined with the good fire-resistance properties of less-flammable fluids to prevent transformer tank rupture, explosion, and fire. There have been no reported eventful failures involving less-flammable units with these requirements. Similar protective devices (with the addition of low current fault protection) are also used by FM for its new FMRC-Approved Transformer standard.

Presently, UL has classified only two liquids in the less-flammable category: a high molecular weight hydrocarbon (HMWH) and a silicone. Common to both classifications are the following additional use restrictions:

* They are applicable to 3-phase transformers only;

* The transformer tank must be able to withstand an internal pressure of 12 psig;

* The transformer must be equipped with a pressure relief valve with a capacity based on the transformer kVA rating;

* The transformer primary side over-current protection must be selected to meet specific energy let-through ([I.sup.2]t) specified in the use restrictions; and

In mid-1995, a revision in both UL less-flammable fluid classifications banned the use of immersed expulsion fuses that vented during operation, unless the classified fluids are tested effectively and the installation includes primarily current limiting fusing. A representative classification marking is shown in Table 2 for a specific silicone brand. In December of 1995, UL tested and reversed the internal expulsion fuse ban for an HMWH fluid classification. The resulting UL marking is shown in Table 3.

The requirement noted above takes into account the fact that many transformer designs have the primary fusing in the transformer case, under the same insulating fluid as the transformer itself. The UL-classified HMWH fluid allows the additional option of current limiting fusing (which may be used alone or in combination with under-oil expulsion fuses inside the transformer tank), or the option of external expulsion fusing without current limiting fusing, provided the let-through current/time is within the maximum allowable limit


End
(by Loyd, Richard E)

 
 
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Transformer modifications

Sec. 450-28 of the NEC has some specific provisions that govern modifications to transformer installations. Although the NEC is not a retroactive document, it is specific in establishing requirements where a modification can change the entire context of a particular installation. Transformers are an excellent example of this case.

When modifications are made to a transformer that changes its type (i.e. oil-insulated to less flammable), it must comply with the appropriate requirements for the installation of the new type. The transformer must be marked to show the type of insulating liquid used in the modification. This marking is a critical element for an inspector to determine if the transformer is in compliance with its appropriate installation requirements.

This requirement for a marking and compliance with the installation requirements for the new "type" can work to a user's advantage as well. If buildings are expanded or altered such that they no longer have appropriate distance separation from, for instance, an oil-insulated transformer, then the transformer may be modified with a less-flammable liquid, and the new space separation may now be acceptable.

Transformer installation requirements in the 1996 NEC

Some changes in the requirements for the installation of less-flammable liquid-filled transformers appear in the 1996 NEC. These changes are significant enough to warrant their consideration here.

The Code-Making Panel covering transformers received proposals for Sec. 450-23 to clarify the installation requirements in both indoor and outdoor locations for less-flammable liquid-filled transformers. Per Fig. 7, you can see that one of the permitted installation methods for less-flammable liquid-filled transformers is to comply with the requirements in Sec. 450-26. These requirements are written specifically around oil-filled transformers, and the panel made it clear that the less-flammable liquids are permitted to be installed in situations identical to that for oil-filled. The basic requirement in Sec. 450-26 is to install the transformer in a vault constructed in accordance with Part C of Art. 450, unless one of the following exceptions can be met.

* If the total transformer capacity is 112 1/2 kVA or less, the vault may be constructed of 4-in. reinforced concrete.

* If the nominal voltage is 600V or less, the vault may be omitted if arrangements are made to prevent a transformer oil fire from igniting other materials, and the total transformer capacity does not exceed 10kVA in a section of a building classified as combustible or 75kVA in a section classified as fire-resistant construction.

* Electric furnace transformers can be installed without a vault where the total rating does not exceed 75kVA, and arrangements are made to prevent a transformer oil fire from igniting other materials.

* Transformers are permitted to be installed in a detached building that does not comply with the vault requirements if neither the building nor its contents present a fire hazard to any other building or property, and if the building is used only in supplying electric service, and the interior is accessible only to qualified persons.

* The vault may be omitted for transformers used in portable and mobile mining equipment with additional conditions specified.

Outdoor locations

Since less-flammable liquids are indeed less of a fire safety hazard than their mineral-oil counterparts, the 1996 NEC clarifies installation requirements for outdoor installations as well.

For installations attached to, adjacent to, or on roofs of Type I or Type II buildings, the installation shall simply comply with all of the restrictions in the listing of the liquid. A fine print note in Sec. 450-23(b)(1) notes that when the transformer is installed adjacent to combustible materials, fire escapes, or door and window openings, additional safeguards may be necessary. The safeguards noted in Sec. 450-27 may be acceptable. Note that in the 1993 NEC, this was part of the actual requirement, and the current status as FPN makes continued enforceability questionable.

For other than Type I or Type II buildings, the installation shall be installed in accordance with the same requirements as oil-filled transformers in Sec. 450-27.

NESC requirements for less-flammable liquids

The NESC is published by the Institute of Electrical and Electronics Engineers (IEEE) as ANSI/IEEE C2-1993. The document generally is used by utility companies and provides practical safeguarding of persons during the installation, operation, or maintenance of electric supply and communications lines and their associated equipment. The NESC specifically references the NEC for building utilization wiring requirements.

As the following sections will show, the NESC has very few specific requirements for transformers. This should be considered along with the fact that most utilities have their own operating and installation procedures above and beyond any code or standards requirements.

Although enforcement of the NESC is by the utility companies themselves, engineers and inspectors outside of the utility industry should be aware of NESC requirements for transformers. Since the local authority having jurisdiction is primarily [TABULAR DATA FOR TABLE 1 OMITTED] concerned with fire and personnel safety within and around public or private buildings, the location of a transformer, even one owned and maintained by the utility, can become a concern if a building or combustible materials are in close proximity.

The NESC has specific transformer requirements for installations in "electric supply stations." It defines these areas as "any building, room, or separate space within which electric supply equipment is located and the interior of which is accessible, as a rule, only to qualified persons. This includes generating stations and substations, including their associated generator, storage battery, transformer, and switchgear rooms or enclosures, but does not include facilities such as pad-mounted equipment and installations in manholes and vaults."

Outdoor installations. The NESC has language that is much less specific than that provided in the NEC. Sec. 152(A) simply requires that specified methods be used to minimize fire hazards associated with liquid-filled transformers. These specified methods include the following:

* Use of less-flammable liquids;

* Space separation;

* Fire-resistant barriers;

* Automatic extinguishing systems;

* Absorption beds; or

* Enclosures

Although the specific requirements to apply these methods are not provided in the NESC, you should consider using some of the methods described in this document, particularly if the transformer is located close to a nonutility building.

Indoor installations. The NESC categorizes transformers located indoors as liquids of flammable, nonflammable, and less-flammable types. Transformers containing flammable liquids (such as mineral oil) and rated above 75kVA must be installed in ventilated rooms or vaults separated from the rest of the building by fire walls. The specific rating of the fire walls are not given in the NESC. As such, you should consider the degree of the fire hazard when determining the rating of these walls. Doorways leading to the room or vault should be constructed with a fire-resistant rating as well. It's also required that the room or vault have a means to contain the liquid of the transformer(s), should a rupture occur.

The NESC specifies that a pressure relief vent of a transformer with a nonbio-degradable liquid, when installed, be provided with a means for absorbing toxic gases. This requirement relates to that discussed in NEC Sec. 450-24 for these transformers.

Less-flammable liquid. NESC requires that less-flammable liquid-filled transformers be installed in a way to minimize fire hazards. You must consider the type of electrical protection, amount of liquid contained, and tank venting when selecting a location for the transformer.

(by Loyd, Richard E)
to be continue...


 
 
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"Our oil analysis results often show levels of water present in the oil. We are considering the purchase of portable equipment suitable for the removal of water from lube and hydraulic oil systems. I have also been told by some people that some separators can only remove water down to the water saturation level of the oil. Is there a preferred method for removing water from oil in a lube or hydraulic circulating system? How much water can be removed by these methods?"

Water in any lubrication system is bad news. In hydraulic systems, it can result in vaporous pump cavitation, corrosion and valve stiction, while in circulating lube oil systems it can cause oil film strength loss, rusting and other serious mechanical problems.

The effects of water on the oil are often overlooked. Excessive water contamination can result in premature oil oxidation and promote the buildup of sludge and varnish. In ester-based fluids, it can result in the hydrolytic destruction of the base fluid resulting in the formation of corrosive acids. In some circumstances, water can also strip additives from the oil through water washing or hydrolysis resulting in premature oil degradation.

For these reasons, the best strategy when it comes to water is to monitor and control the root cause of the water ingression. This can be achieved by ensuring that all seal and breathers are in good shape (consider using desiccant style breathers), lube tank hatches are closed and sealed properly and that top-up oil is stored and handled properly.

Water can exist in three phases in an oil, free, emulsified and dissolved. Free and emulsified water cause the most damage so a good rule of thumb is to keep moisture levels below the saturation point so that all the water is in the dissolved state. For typical mineral-based industrial oils, this is typically 200-300 ppm.

The most effective way of achieving this is to use a vacuum dehydration unit. These systems are capable of removing free and emulsified water as well as up to 70-80% of the dissolved water. For a typical hydraulic fluid, this can mean water levels as low as 30-50 ppm (0.003-0.005%). Alternatively, many companies are reporting success with vapor extraction devices mounting on tank tops. Some of these devices work similar to air conditioners in removing humid air from tank headspaces.