When to change oil in vacuum pump? Why to change vacuum pump oil? How to change oil in a vacuum pump?

Oil change in the pump is carried out when the pump is at ambient temperature. In case of top up of oil first oil is drained from the drain of the vacuum pump. Vacuum pumps used in wet application (salt drying/ paper drying), often tend to condense water vapour in the exhaust cycle which emulsifies in the oil and turns milky. One may keep the pump idle over-night and next morning, drain the oil. Often water that is settled overnight is drained initially followed by oil. If the later is acceptable in form of contamination, then top up of oil can be opted. Pump should not be rotated either by hand/motor, since water settled overnight may mix with oil.
In case of total oil change, first the oil from pump is drained completely. Later pump is filled with flushing oil. The pump is rotated by hand or its motor is inched (turned ON-OFF). This aids to circulate flush oil in the pump and gather dirt accumulation from the pump. Flushing is done twice or thrice as the contamination demands. Flushing oils are generally less viscous and compatible to vacuum pump oils. One may opt to mix benzene or carbon tetra-cholride with vacuum pump oil for better results. However, it is strongly recommended that the pump be rotated by hand in such scenarios. Followed by flushing the vacuum pump is filled with a new charge of oil.

What is Oil consumption of a vacuum pump, how much oil is consumed by a vacuum pump?

There is no equation that suggests an estimate of consumption. Individual pump manufacturers may however, lend information on oil consumption rate in cc (cubic centimeter) per mbar-cu.m of the pump which is helpful in estimating the oil consumption rate. General figures are 1.8 to 2.3 cc per 1000 mbar-cu.m of air for gas ballast pumps. Gas ballast contributes to 10% consumption in total oil consumption.

The post What is frequency of oil change in a vacuum pump? appeared first on NACH ENGINEERING.

A. Primary : Electrical Insulation

The main purpose of oil in transformers is to provide an effective electrical insulation between (a) the winding and tank  and (b) between the different winding

B. Secondary: Cooling of transformer

The secondary purpose of oil is to mobilize heat from core and winding to cooling surfaces of the transformer tank.

To fulfill the above purpose, following basic qualities of transformer oil are required:

1. The oil shall be free from dirt, moisture, metal ions fibres etc.

2. It should be stable against oxidation at operating distinct temperatures

3. It should not be corrosive in nature

4. It should not be soluble with respect to transformer material of construction

The post Why oil is required in transformer? appeared first on NACH ENGINEERING.

Here in this article we will address vacuum drying process/method , principle of vacuum dryer of power transformers and how it is done.

Let us start with basic concepts of insulation and its importance.

Insulation materials are those materials that act as a barrier for electricity conduction. Insulation materials or simply electrical insulation is of prime importance in area of utility of Electric appliances, be it a home appliance operating on 110VAC/230VAC or an industrial equipment operating on 380VAC/415VAC or electrical high voltage devices like the transformers, transmission lines, circuit breakers and like.

As the power levels scale up, the internal insulation levels of devices, (say like insulation between two phases, phase to ground insulation etc.) become more crucial and decisive factor for the life of the device. Devices like transformers and motor-generators require a good insulation for robust electrical performance.

Water is abundantly present in the atmosphere in form of water vapour.  Insulation material like paper, insulating oils, wood etc. have natural tendency to absorb water. Water is a good conductor of electricity and if absorbed by the insulation of the device weakens the insulation.

When a device with a weak insulation is put in operation, the electric pressure (voltage) may break the insulation barrier for the current resulting in heavy inrush of electric current  which the device may not be able to withstand and eventually break down. In case the device happens to be a part of the system, this may result in failure of the system.

We thus need to ensure a proper insulation of the electrical devices to assure non-failure of the devices.

How can we ascertain a good insulation? What are parameters that decide that the insulation is really in good condition?

Insulating materials say like a plastic handle of electric iron, rubber shoes of wire-man, insulating oils in a transformer or say chemicals used in motor windings, all of them require three properties to be defined as  good insulators.

First property of the insulator is its resistance offered to the electrical current. The higher the resistance better is the insulation. Second property, the dielectric strength or breakdown strength of insulation, defines strength of the insulation to withstand electric pressure the stress that is developed in the insulation. The third property, the dielectric constant, or the dielectric power factor or also called tan delta, states the amount of electrical energy consumed by the insulator itself in order to act as a barrier to the electrical potential.

By judging these three properties, one can evaluate the quality of insulation.

How can we build good insulation properties?

The parameters defined above which give evidence of good insulation are sharply affected by the water content in the insulation material. Thus if are able to develop insulation that has least water content we are able to achieve better insulation properties. Removal of water from the insulating material is called the process of drying. Drying of insulation to some extent can be done by heating the insulating material and vapourizing the water from the insulation. However, heating of insulation material is limited activity as it may damage the physical and chemical properties of the insulation material. In case of transformers, one cannot simply elevate temperature in order to evaporate more and more water from the insulation. This damages the physical properties of the transformer and also may be hazardous.

We have seen a generalized scenario of insulation and drying. In the discussion to follow we shall now concentrate on drying of transformers.

How can we achieve drying without elevated heating of the insulation material for transformers?

Drying of insulation materials can be achieved at low temperature and low pressure levels. The pressure levels and temperature levels for drying vary for distinct material. At low pressure or under vacuum the rate of water vapour evaporation is accelerated if sufficient heat is provided to the insulation material.  Thus we can achieve a good drying of insulating material if the material is suitably heated and subjected to vacuum.

What are the components/equipments used in vacuum drying process of power transformers?

Vacuum drying process requires a closed vacuum tight chamber, a heating system that can heat the insulation in stipulated time, a vacuum system and a controlling mechanism. We shall discuss these one by one below

• Vacuum Tight Chamber:

  This is generally a rectangular chamber of size suitable to place a transformer or a multiple set of transformers. The construction of the chamber is made rigid to withstand heat and vacuum.  The chamber is provided with trolley to maneuver the transformer in/out of the chamber.

• Heating system:

  Inside the oven, on the walls, tubes are provided wherein a hot fluid flows to transfer heat to the object placed in the oven.  This fluid is externally heated  by electrical heaters or by a gas/fuel  fired boiler. A fan is provided in the oven to uniformly distribute the temperature and accelerate the heating of the transformer insulation.

• Vacuum System:

  The vacuum system consists of vacuum pumps, condensers and booster pumps. The vacuum pump and booster pumps evacuate the chamber and extract the moisture/gas (air) from the chamber. Water cooled Condensers placed in series of the vacuum pumps aid in condensing the water vapour extracted from the transformer’s insulation.

• Controlling Mechanism:

  With the advent of PLC and SCADA the whole process of drying can be monitored and controlled to desired levels. Vacuum levels can be monitored and controlled. The temperature level  in the vacuum drying oven can be controlled. The time taken for drying, amount of drying done and end of power transformer drying process can be determined and monitored.

What is vacuum drying of transformers and how vacuum drying of transformers is done?

In the process of vacuum drying the insulation material of transformer, the transformer is placed in vacuum drying oven. A vacuum drying oven consists of heating facility and a vacuum system to develop low pressure in the oven/chamber. The transformer is first heated to a desired level. The insulation material should be uniformly heated and its temperature should be elevated to acceptable levels. After heating the material, it is subjected to vacuum. Vacuum in the oven is developed by a vacuum system consisting of vacuum pumps. Due to low gas pressure in the vicinity of the material, i.e. in the oven, the moisture absorbed by the insulation is released and extracted by the vacuum system.  The vacuum system consists of the water condensation system where this water vapour can be condensed and also measured.

What decides the efficiency of the drying process?

The factors that result a good drying process are

(a) insulation material temperature and its uniform distribution,

(b) property of the material to release water also called the diffusion coefficient,

(c) difference of pressure exerted by the water vapour on the insulation and surrounding area (i.e. inside of the oven) and

(d) the time required for drying out the insulation.

At NACH we have expertise in developing the vacuum drying ovens of required sizes for drying of power transformers. Our installations of large drying system are a state of art. We understand the requirement of the drying process and its influence on quality of the transformer. We believe that with our drying process techniques, the client shall be benefited in quality and costing of the transformer.

The post what is vacuum drying process/method of industrial drying oven of transformer appeared first on NACH ENGINEERING.

(like casting) or objects with inherent voids (like motor coils) to prevent accumulation of undesired

elements like dust, dirt, chemicals or water. Impregnation of objects improves its physical properties

and also tends to improve overall parameters of the equipment/component wherein use. For Ex. a

varnish impregnated coil improves the overall insulation resistance of the motor and hence the life of

the motor is improved.

Different chemicals are used in the process of the impregnation. These chemicals can be classified

as epoxy, varnish and resins. Impregnation process itself can be classified in different types like

flood impregnation, dip impregnation, vacuum impregnation, vacuum pressure impregnation, trickle

impregnation, hot roll dipped impregnation. At NACH we have expertise in manufacturing all these types

of the impregnation systems.

Flood impregnation and dip impregnation are simple impregnation processes often used in the low

voltage small frame electrical motors. In flood impregnation the resin/varnish is flooded in the chamber

where the preheated coils (electric motor stator or wound rotor) are placed. The coils are kept for

soaking in varnish for a certain period and then taken off to the baking oven. The varnish is stored in

a cold chamber or vessel called the storage tank. Typically temperatures for maintaining the varnish/

resins is 15 deg C to 10 deg C. In dip impregnation, coils are dipped in a tank that contains varnish and

kept for a certain time.

Vacuum pressure impregnation is a special process designed to impregnate the motor coils or some

castings that are used in critical applications. Vacuum pressure Impregnation often called the VPI

process impregnates the coils or metal castings under vacuum. Impregnation under vacuum prevents

advent of external moisture that may be accumulated in the voids of the coil or may be absorbed in

insulation. Vacuum impregnated coils are free of moisture that result good electrical properties.

In case of metal impregnation, vacuum impregnation results good adhesion of the chemical with the

surface. Metal impregnation process that involves impregnation of castings is often accompanied by

additional processes like cleaning of castings jobs, chemical treatment for better adhesion etc. Often

epoxy is used for porosity sealing of the castings.

In a vacuum pressure impregnation plant, there are two tanks, one is the impregnation chamber and the

other is the storage tank used to store the varnish/resin. In resin impregnation system, often storage

tanks require cold storage of level up to 10 Deg C to 15 Deg C. Alternately a epoxy impregnation system

demands hot storage, since the curing of epoxy occurs at room temperature. Distinct manufacturers

for epoxy like Alantas (formerly Dr Beck), Huntsman (formerly CIBA), Von Roll, Vantico Ltd. suggest

methods for vacuum pressure impregnation with indication of different processes like vacuum, soaking,

maintaining pressure, amount of pressure etc for better results.

In a typical vacuum pressure impregnation system for motors, preheated coils are kept in the

impregnation tank and vacuum is drawn. After a certain period resin is introduced in the impregnation

tank in controlled manner and filled till the top of the coil stack. Dry air or nitrogen pressure is applied in

the chamber for better penetration of the resin in the voids and this is maintained for a stipulated time.

Later the resin is withdrawn to the storage tank. Almost in all the impregnation processes the resin or

varnish transfer from tank to tank is achieved by pressure difference in the two tanks or by gravity flow

of the varnish.

In trickle impregnation or a hot rolled impregnation process, the resin is introduced on the motor coil

in a very controlled fashion. The coils are heated by use of its own resistance. This type of methods are

used where resin costs are higher or usage of resins/chemicals have limitations.

At NACH we have the expertise to develop the vacuum impregnation systems for different resins. NACH

can manufacture VPI systems as per guidelines and specifications defined by resin manufacturers.

The post What Is Vacuum Pressure Impregnation Process ? appeared first on NACH ENGINEERING.

Do you know want to know what is Transformer Oil Purification ?  how to do transformer oil filtration? Or what is oil purification process?.

In this article you will understand transformer oil purification process , steps and methods involved in oil purification process.

Transformer oil filtration machine

Transformer oil purification is a process to remove sludge, dissolved moisture and dissolved gases from the oil.

Before we move to process details, Lets see why transformers need purified oil  ?

Need for transformer oil filtration

As discussed in details Advantages of transformer oil filtration  in post why transformer oil filtration is required? here we will see in brief advantages for transformer oil purification :

• Improved insulation properties of the oil and hence the other media like paper/cellulose insulation
• Better the insulation of transformer, longer the life of the transformer and lesser the breakdown of the transformer
• Longer the life of the transformer asset, good returns on investment of the asset
• Lesser breakdowns and failure of the transformer results in uninterrupted power supply

For good performance of transformers we require filtration machines designed and manufactured with standards. At NACH we manufacture Oil purification machines with Standard (BIS, NEMA, IEEE, IEE, ASTM, ASME, IEC) for good performance of transformer.

Now lets move to, Transformer Oil Purification Procedure

Transformer Oil Purification Procedure

Transformer is one of the main asset in the electrical power industry which needs to be maintained for guaranteed uninterrupted power transmission in order to get assured revenue benefits.

Transformer life mainly depends on the quality of oil volume it contains.

Regular transformer oil filtration assures long and consistent results from the transformer.

Transformer oil purification is a process to remove sludge, dissolved moisture and dissolved gases from the oil. Transformer oil conditioning may also include to some extent improving the acidity of the oil.

A good oil purification system is able to deliver filtered oil with parameters as per the standard specification.

However, this revival of the oil by oil filtration plant to standard oil parameters is based on the quality of unprocessed oil and its initial process. In case the unprocessed oil does not match the standard oil parameters, then the effort of transformer oil filtration is all in vain. Alternate method of regeneration of transformer oil should be adopted in this case.

Here we shall look at the method of the transformer oil filtration by vacuum type dehydration and centrifuge type removal of solids and water separation.

Transformer oil conditioning is a stream line oil filtration process of sludge purification, moisture removal and gas removal.

First step in the transformer oil purification

The first step in this serial process is to raise the oil temperature to a desired level, generally upto 65 Deg C. This aids to give the oil latent heat which later aids to dissociate the moisture and gases from oil in the degassing chamber. Additionally the viscosity of the oil drops which aids in better filtration to some extent. Recommended heater design should consider an area of heating of about 1 to 2 W/sq.cm. In the transformer oil purification plant, the heating system is protected against over pressure built up and excess temperature rise.

Second step of transformer oil purification

The second step of transformer oil purification plant is removal of sludge and dirt from the transformer oil.

Two methods have been used for removal of the sludge:

• Removal of sludge by filter candles. and/or
• Removal of sludge by centrifuging action.

Removal of sludge by filter candles.

Transformer oil filtration using filter candles in the transformer oil purifier machine can further be classified as:

• Filtration using the classical edge filter
• Filtration of transformer oil using the depth type filter.

Both methods of cartridge type filtration are prevalent and owe certain advantages and disadvantages.

The edge type filter system can be cleaned and be reused for at least three to four times, however, cleaning and fitting of the edge filters involves considerable time and human effort. This system is robust to handle large quantity of sludge. Edge filters can be cleaned by reverse pressurized dry air/nitrogen flow in order to remove the contamination. After de-sludging the paper stack is removed and dried in oven/ bright sunlight and reused. This operation demands experience and skill set.

New trends and technology in the market have driven transformer oil filter machines to use filter cartridges instead edge type paper stacked filters. These cartridges are similar to those of the water filter cartridges and can be selected from a variety of purification range say from 500 micron to 0.5 micron size.

The advantage using these cartridges over the edge filter is

• No moisture storage, since the filter media used can be non-hygroscopic
• Easy to replace with less human effort and easy availability.

Removal of sludge by centrifuging action.

An alternate method used for dirt separation from oil is centrifuge. Routine transformer oil filtration or transformer oil conditioning is often confused with transformer oil centrifuging. Transformer oil centrifuging is all together a different technology and has a little impact on improving the oil parameters. Centrifuges used for separation of dirt from the transformer oil can be slow speed type centrifuges that do not require additional electric motor to spin the centrifuge cone at high speed.

However, the dirt separation from oil with such centrifuging has limitations since these centrifuges cannot remove the dirt less than 10 micron level. Thus a power driven centrifuge becomes evitable which scales up the cost of the oil conditioning machine.

Only advantage of the centrifuges is that the recurring cost of changing filter elements is saved. Power driven centrifuges can remove water from the oil that is in free form but not the dissolved moisture. Manufacturers of power driven centrifuge also often do not guarantee removal of moisture to a level less than 5 ppm.

Third  step in the oil filter machine

The third step in the oil filter machine is dehydration of transformer oil and degasification of the transformer oil.

Dehydration  and Degasification of transformer oil

These processes of dehumidification of transformer oil and removal of gasses is executed in the degassing chamber. The dissolved water oil separation or dissolved gas oil separation is possible at reduced pressure, i.e. vacuum, due to difference of boiling point of water, gas and transformer oil. In the process of separation of gases from the oil it becomes important to retain the aromatic hydrocarbons so that the original properties of the oil are retained. When the water level in the oil is above saturation level of the transformer oil, oil is observed in free water. Removal of free water can be done by power driven centrifuge or by coalescing principle, where the later is more effective and economical in practice.

Why NACH make oil filter plants

With the different processes involved in the transformer dehydration and degasification plant it is evident that the processes should be neatly designed to tame different oil volumes to be filtered. With increasing power demands and scaled up voltages transformer oil filtration is becoming more and more demanding and sophisticated. With the advent of new technology now the water activity or the water content in the transformer oil is measurable online and methods of laboratory testing like the titration method are becoming limited. At NACH we are update with the recent trends and technology pertaining to the oil filtration and also with requirements imposed for UHV and EHV grade transformer oils.

At NACH we understand the requirements of the oil filtration and are committed for resulting a good transformer performance.  Feel free to contact us,  we shall be happy to help you  and provide you a quick response.

Providing  Quality Product Rage and Services for transformer

Interested in transformer oil filtration machine? , call + 91 9881624496 or send email : nachengg@gmail.com

The post Transformer Oil Purification / filtration Process/Procedure ? appeared first on NACH ENGINEERING.

tend to weaken the inter winding bonds of the filter element. The condition is worsen if core of the filter

element is of plastic/polypropelene (PP), as these filter elements also lead to deformation fter 75 deg C

temperature. However, PP yarn or nylon yarn do not absorb moisture and are better recommended for

wet applications. Hence a blend of SS core with PP yarn/Nylon yarn ensues good results in filtration.

The post Use of SS core Filters, with PP/NYLON windings appeared first on NACH ENGINEERING.

maintained at varying operating temperatures of vacuum pump. These parameters are crucial for

deciding vacuum pump performance. Genuine vacuum pump oil recommended by pump OEM, are able

to deliver better performance of vacuum pump under running condition. Oils manufactured by pump

OEM, say LEYBNOL, manufactured by Oerlikon Leybold, have good blending of chemicals to preserve

the oil properties under different working conditions. Such chemically blended oils demonstrate good

performance in chemical environments.

The post Genuine Vacuum Pump oil appeared first on NACH ENGINEERING.

maintain oil quality in order to expect continuous vacuum pump performance. Continuous monitoring of

oil quality and quantity can save over cost of replacing the vacuum pump. It is highly recommended to

use genuine oil in the vacuum pump as recommended by the OEM.

The post Use proper oil for safeguarding the vacuum pump appeared first on NACH ENGINEERING.