FIT OF A COMPONENT SPECIFICATION

          The components of the toleranced dimension shall be indicated in the following order: 

a) The basic size, and

b) The tolerance symbol.

          If, in addition to the symbols it is necessary to express the values of the deviations or the limits of size, the additional information shall be shown in brackets.

Permissible deviation:

.The upper deviation or the upper limit of size shall be written in the upper position and the lower deviation or the lower limit of size in the lower position, irrespective of whether a hole or shaft is toleranced.

.The tolerance symbol for the hole shall be placed before that for the shaft or above it, the symbols being preceded by the basic size indicated once only. 

BEARINGS

          "A bearing is a machine element that constrains relative motion between moving elements to solely offer the desired motion". Bearings are designed to provide free linear movement of the moving elements or free rotation around a fixed axis or it may prevent motion by controlling the vectors of normal forces that acting on the moving element. They are mainly used as friction-reducing devices between moving parts.

          When a metal contacts with another metal produces a large amount of friction. Due to this friction the metals wear and tear, produce grinding that slowly degrades the metals that are in contact. Bearing reduces friction by allowing one moving part to glide past another moving part. Bearings consists of a smooth metal ball or roller that rolls against a smooth inner or outer metal surface (race). The balls or rollers take up the load, allowing the device to spin.   

PRINCIPLE OF FRICTION

          If you've been asked to move one ton, smoothly polished block which is placed on ground (another surface) from one place to another location. During initial attempt to move the block, the two surfaces in contact (the base of the block and the ground) resist movement. This is called Static friction. If we applied some more force, which is enough so that the surface begin to slide against one another. Once in motion, the resisting force is from kinetic or slippery friction, instead of static friction.

          If beneath of that very same block we placed equally spaced rollers, the force which is required to move the block is considerably reduced. Do you know why? The rollers, in contact with the surfaces of ground and block, still encounter friction, but the rotating action of the rollers carries the block and have eliminated the resisting force of Kinetic friction; the friction encountered is now classified as Rolling friction. Rolling element bearings are designed based on this principle. They eliminate sliding friction and utilize the efficiency of rolling friction to carry load.

Comparison of 304 or 316 and 304L or 316L type welding electrodes

As American AISI basic grades, the only practical difference between 304 or 316 and 304L or 316L is carbon content. ... The 1.4301 (304) and 1.4307 (304L) have carbon ranges of 0.07% maximum and 0.030% maximum, respectively. The chromium and nickel ranges are similar, nickel for both grades having an 8% minimum. Low carbon rods, which provides extra corrosion resistance.

--> ER 308 stands for MIG wire

MAKE	SIZE  DxL (MM)	Amps.	/CARTON
SS - Supron	2.50X350	60-90	260
MS -Manglam	3.15X350	100-140	150
	3.15X450	100-140	150

CHILLER CAPACITY CALCULATION PROCEDURE

          Just like refrigerator a chiller uses a refrigeration cycle to cool water or dehumidifies air. This chilled water then used to cool a larger space, such as a factory floor or for process uses. Cooling equipment in this matter increases its efficiency by providing a steady thermal environment. Before we begin to derive a chiller's capacity we must know three variables, they are:

1. The incoming water temperature

2. The chilled water (out going water) temperature required

3. The flow rate

          This formula produces the chiller's capacity in British Thermal Units (BTU’s). That scale directly corresponds with the more common unit of "tons" that cooling systems often use.

For our example, we will calculate what size chiller is required to cool 60 GPM (gallons per minute) from 64 °F to 52 °F? Use the following five steps and general sizing formula:

1. Calculate Temperature Differential (ΔT°F)

          Subtract the temperature of water as its leaves the chiller from the temperature of the water as it enters it.

ΔT°F = Incoming Water Temperature (°F) - Required Chilled Water Temperature.

· Example: ΔT°F = 64°F - 52°F = 12°F

2. Calculate BTU/hr. (British Thermal Unit/hr)

          The cooling capacity of air conditioners is measured in BTUs, or British thermal units. The more Btu of capacity, the larger the room the air conditioner can cool. Scientifically, ‘one Btu is the amount of energy required to change the temperature of 1 pound of water by 1 degree Fahrenheit’. In terms of air-conditioner capacity, the rule of thumb is that it takes around 25 Btu to cool 1 square foot of room floor area.

To calculate BTU Multiply the temperature difference by the flow rate (that what we need), which is measured in gallons per minute. If, for instance,

BTU/hr. = Gallons per hr x 8.33 x ΔT°F

· Example: 60 gpm x 60 x 8.33 x 12°F = 3,59,856 BTU/hr. 

(Or)

· 40 gpm x 500 x 12°F = 3,59,856 BTU/hr.  (since 60 x 8.333 = 500)

3. Calculate tons of cooling capacity

Tons = BTU/hr. ÷ 12,000

· Example: Ton capacity = 239,904 BTU/hr. ÷ 12,000 = 29.998 tons

1 ton = 12000 BTU

4. Oversize the chiller by 20%

 Ideal Size in Tons = Tons x 1.2

· Example: 29.998 x 1.2 = 35.9976

5. You have the ideal size for your needs

· Example: a 35.9976 (or 35-Ton) chiller is required