Monday, February 17, 2014

Inventory control

Inventory is a physical stock of items that a business or production enterprise keeps in hand for smooth functioning. Inventory control is a concept in which material with apposite quantity and quality is made available whenever required with due regard to economy in storage and ordering costs and working capital. Inventory control helps to ensure goods requirement in reserve format at the lowest possible ultimate cost. Improper inventory control leads to heavy loss. The most important functions of inventory control are to run the stores effectively, to ensure timely availability of material and avoid build-up of stock levels, technical responsibility for the state of material, stock control system, maintenance of materials, supply etc. and avoiding improper handling. The tools to control inventory are maximum stores, minimum stores, standard order, re-ordering point and procurement time. A good inventory control allows an organization to make purchases in economic lots, maintain continuity of operations, avoid small time consuming orders and assured prompt delivery of finished goods.

Classification of rivers

The two main types of rivers are rivers in hills and rivers in flood plains. Rivers in hills start from the mountains and flow through the hilly regions before reaching plains. Rivers in hills are of two types. They are incised river stage (rocky stage) and boulder river stage. Degradation process is responsible for flow channel in Rocky stage types. In Boulder river stage, river flows through wide shallow beds and interlaced channels and develops a straighter course. Rivers in flood plains or alluvial plains are of four types. They are aggrading, degrading, stable and deltaic. A silting river which forms a slope is known as aggrading river. In a degrading river, the river bed gets sourced constantly. In a stable type river, it is very difficult to find any significant changes in alignment, slope and regime. A deltaic river gets divided into branches before joining the sea. Based on flood hydrographs, there are two categories of rivers. They are flashy rivers and virgin rivers. Sudden flood rise and flood fall results in a flashy river. If the river water dries completely before it joins another river or sea is known as Virgin River.

Wednesday, December 25, 2013

Metallic and non-metallic coatings

Metallic and non-metallic coatings are used for corrosion protection in metals. The major types of metallic coatings are hot dipping, spraying, electroplating and diffusion coating. In hot dipping, the metal part which is to be protected against corrosion is dipped in a molten bath of the coat metal. In spraying method, the coat is melted into small drops of liquid and propelled by a blast of air on to the metal surface. Aluminium coatings are obtained by hot dipping or spraying. In electroplating method, the metal part which is to be coated is made cathode and immersed in an electrolytic bath with the electrolyte containing the ions of the coating material. Nickel coating and tin coating are usually done by employing electroplating technique. In diffusion coating, the diffusion of the coat metal into the part through the surface is achieved at an elevated temperature. Metal coating can be classified according to their electrochemical behavior into two-noble coatings and sacrificial coatings. The coat is noble with respect to the underlying metal in noble coatings. The underlying metal is protected by the sacrificial action of the coating in sacrificial coatings. Zinc coatings on iron are sacrificial. There are two categories in nonmetallic coatings- organic and inorganic. Organic coatings refer mainly to paints applied to metals. Paints are normally mixture of particles of a pigment in a continuous organic medium. Examples of pigments are red lead and zinc chromate. Examples of inorganic nonmetallic coatings are enamel and porcelain.

Bearing alloys

A stationary bearing should possess least friction between the bearing and the rotating part for better result. The wear of the contacting metals is made as low as possible and made strong enough to withstand pressures that arise from small misalignments. For preventing seizures, stationary bearing melting point should be low. To make friction and wear low, a thin film of lubricating oil is introduced between bearing and the rotating part. Soft and low melting alloys are preferred to deal with pressure and melting related issues. Normally a soft matrix bearing alloy in which hard particles are incorporated is a preferred choice. Babbits or white metals are used for this purpose. Normally babbits are either lead-based or tin-based alloys. Addition of small amount of arsenic increases the pressure withstanding power of alloys. Bronze bearings are normal choice when we have to deal with high bearing loads. Some other commonly used bearings are aluminium based and silver based.