2002(08)LCX0175

IN THE CEGAT, SOUTH ZONAL BENCH, CHENNAI

S/Shri S.L. Peeran, Member (J) and Jeet Ram Kait, Member (T)

COMMISSIONER OF CUSTOMS, CHENNAI

Versus

ASIAN BEARING LTD.

Final Order No. 892/2002, dated 9-8-2002 in Appeal No. C/420/98

Cases Quoted

Bharat Forge & Press Industries (P) Ltd. v. Collector — 1990 (45) ELT525 (S.C.) — Relied on [Paras 4, 6, 8]

Collector v. Escorts Ltd. — 1990(11)LCX0038 Eq 1991 (054) ELT 0144 (Tribunal) — Relied on........................ [Paras 6, 9]

Collector v. Escorts Ltd. — 1997(10)LCX0031 Eq 1997 (096) ELT 0504 (S.C.) — Relied on..................................... [Para 7]

Advocated By :   Shri G.S. Menon, SDR, for the Appellant.

Shri S.S. Radhakrishnan, Advocate, for the Respondent.

[Order per : S.L. Peeran, Member (J) (Oral)]. - Revenue is aggrieved with the Order-in-Appeal No. C. Cus. 283/98 despatched on 1-4-98 by which the ld. Commissioner (Appeals) has upheld the importer’s plea to classify “Ultrasonic Washing Machine” under sub­-heading No.8479.81 of the Customs Tariff Act with description “for treating metal, including electric wire coil-winders”. Revenue seeks for classification of the item under residuary heading “other” under sub-heading 8479.89 of the Customs Tariff Act. The machine uses the technology of the ultrasonic sound for the purpose of washing ball bearings. It consists of demagnetzing unit, ultrasonic chamber and jet cleaning system, the essential elements of this being the Generator or Power supply Transducer, Processing tank. As per the technical details, which were placed before the Commissioner, it was seen that the items Ultrasonic cleaning is the latest technology adopted for the bearing cleaning all over the world, as the removal of foreign particles by forced cleaning/brush clearing cannot reach inside the component and still some amount of dirt particles will be retained. It was also noticed that the item, besides this function, was also carrying out an important function of demagnetizing the component. The write up produced on the item states as follows :-

“WRITE UP ON ULTRASONIC WASHING MACHINEMODEL - KARLROLL SK 03428

Anti-friction Rolling Bearing consists mainly of four basic components viz. Inner ring, Outer ring, rolling elements and cages. In this the rolling elements are produced in batches and cages are manufactured out of sheet steel through Gang die with transfer machanism. Inner and outer rings of rolling bearings are manufactured by individual processing after forging like Turning, Grinding, Superfinishing etc.

It is essential for a rolling bearing to operate with less noise which can be achieved through high precision grinding, superfinishing and good cleaning. The grinding operation involves removal of material of about 0.5 mm (500 microns) with the help of grinding wheels which are made of small grits of abrasives bonded together with the help of suitable bonding material and formed as a wheel. The components viz. Inner rings and outer rings are held in the work holding device with the help of magnetic induction and in the process of grinding the component being ground would attain some amount of magnetism retention and some amount of metallic particles/abrasives will stick to the component as now they are having magnetism.

Similarly after the grinding, the superfinishing process involves a material removal of about 5 to 10 microns. This is done with the aid of superfinishing/honing stones/sticks which are made of fine abrasives formed as stones with bonding material.

The iron particles will stick with the components and then due to the abrasion involved in the surfaces becomes dust and paste is also formed. This cannot be normally removed, until a forced cleaning like brush cleaning or ultrasonic cleaning is done.

If these foreign particles are not removed from the rings, the dirt particles will distrupt the lubricating produce noise. Solid foreign particles lead to running noise, wear and premature failure. Hard particles in rolling bearings cause abrasive wear, particularly in contact areas with a high rate of sliding friction. Wear even occurs with extremely small particles. Cycling of larger particles (in the order of 0.1 mm) causes indentations in the raceways. The greater the hardness of the cycled particles (e.g. filedust, grinding chips, mould sand, corundum) and the smaller the bearings, the shorter the life.

The ultrasonic washing machine Karl Roll Model SK 03428 consists of a demagnetising unit, ultrasonic chamber and jet cleaning system. All are connected together with in-built conveyors. In the demagnetising unit, the rings are stacked and they are lifted upwards. When it is lifted upwards, a demagnetiser kept behind the component holder, demagnetises the component. The ring is then passed to the ultrasonic chamber where the washing media, mineral turnpentine is stored. The transducers create the ultrasound waves which makes the particles to get loosened. After this, the ring is taken up to jet cleaning system, where mineral turpentine oil is poured with a huge amount of pressure through nozzles/jets. Then the rings are free from magnetism and foreign particles.

Ultrasonic cleaning is the latest technology adopted for the bearing components cleaning all over the world, as the removal of foreign particles by forced clearing/brush cleaning cannot reach inside the component and still some amount of dirt particles will be retained.”

2. Further examination of the entire manufacturing activity through Flow Process Chart of the item in question which has been placed before us to show that inner and outer rings are made free of foreign particles, then the process of demagnetizing takes places. Thereafter the process of ultrasonic cleaning is done besides the jet washing and thoroughly cleaned inner and outer rings. This is carried out for the following three purposes :-

(1)     As preparation for a process such as plating, painting or bonding.

(2)     When a high degree of cleanliness is essential to make the article attractive.

(3)     When contaminants must be removed to prevent subsequent malfunction or undue wear.

3. The function of each of the item which is there in the ultrasonic cleaning system viz. (a) generator or power supply (b) transducer (c) processing tank has been brought out in the write up which is noted herein below :-

“Generator

The generator converts the mains electrical energy of 50 c/s to an Ultrasonic energy of 22KHz/40KHz.

Transducer

It consists of a piezoelectric crystal which, converts electrical energy into mechanical energy.

Processing Tank

This contains the cleaning liquid and the articles to be cleaned are immersed in it. The transducers are either fitted to sides or bottom of the tank as called for by the application. If the above set-up for transducers is not desired, then transducers mounted in liquid-proof housings suitable for immersion in the cleaning liquid could be provided. These are called immersible transducers.

3.0 Basic Principles of Ultrasonic Cleaning

The generator converts the mains frequency into an Ultrasonic frequency which is converted into a mechanical energy by the transducer. The transducer transfers this mechanical energy to the bottom of the tank which in turn transfers the energy to the cleaning liquid inside the tank.

Ultrasonic energy produces a number of effects in liquids but the following three of these are of particular significance in Ultrasonic Cleaning.

(1) Streaming (2) Degassing (3) Cavitation

Streaming : When the bottom of the tank vibrates it produces a unidirectional force in the fluid with which it is in contact. This results in a flow or streaming notion of liquid away from the transducer surface. Streaming is useful because it assists, in dispersing loosened contaminants and also brings a continuous supply of fresh cleaning liquid to the surface of the article being cleaned.

Degassing : Most liquids contain dissolved or entrapped gas. To achieve efficient Ultrasonic Cleaning.

Cavitation : A wave usually travels with rarefactions and compressions. When the Ultrasonic wave travels through the liquid it causes rarefactions and compressions in the liquid 22000/40000 times a second. This causes formation of bubbles during the rarefaction phase and collapsing of the bubbles during the compression phase of the ultrasonic wave. This process of formation and collapsing of the bubbles is known as cavitation.

From theoretical calculations it has been estimated that a pressure of more than 350 NM/m² and a temperature greater than 5500°C is created when a bubble collapses. This energy though small is released from a single bubble. Millions of bubbles collapse every second, the collective energy of all these bubbles is powerful enough to blast off the contaminant from the surface no matter how tightly bonded. It is for this reason Ultrasonics can clean small holes, crevices and inaccessible areas. Cavitation also accelerates chemical reactions which helps in dissolving the contaminants.

The intensity of cavitation depends on a number of physical properties of the liquid but the three main requirements for good cavitation are :

(a) High surface tension (b) Low vapoure pressure and (c) Low viscosity.

3.1 Design :

Ralsonics Ultrasonic Cleaning System is completely solid state mains operated instrument inclusive of fans for forced air cooling of the electronic components. A separate/inbuilt transducerised stainless tank complete with connecting coaxial cable between the tank and generator. The generator is controlled by a simple ON/OFF switch. The pilot lamp indicates whether the unit is ON or OFF Mains fuse for overload protection is provided.

The transducer is basically a lead-nirconate-titanate rings and sandwiched between two metallic blocks. When ………

Equivalent 2002 (146) ELT 0162 (Tri. - Chennai)