DIFFERENT TYPES OF FITS

Fits:

          The relationship between two parts, which are to be assembled, with respect to difference of their sizes, before assembly is called 'Fit'.

          It is the general term used to signify the range of tightness or looseness that may result from the application of a specific combination of allowances and tolerances in  mating parts.

There are four types of fits between parts, they are

          1. Clearance Fit

          2. Interferance Fit

          3. Transition Fit

          4. Line Fit

1. Clearance Fit:

          When an internal member fits in an external member (as a shaft in hole), in clearance fit there is always an air space or clearance between the shaft and hole. Such type of fit give loose joint. A clearance fit always have a positive allowance.

Clearance fit also sub-classified as

a) Slide fit

b) Running fit

c) Slace running fits

d) Loose running fits

2. Interference Fit:

          When the internal member is larger than the external member then there is always an actual interferance between those materials. This negetive difference between diameters of shaft and hole  is called interference. An interferance fit always have a negetive allowance.

          From the below example, the smallest size of the shaft is 2.2313" and the largest hole is 2.2305" so that least interference among the materials is 0.0008". Under maximum material condition the interference is 0.0018".  

Interferance fit can be sub-classified as

a) Shrink fit (or) Heavy force fit

b) Medium force fit

c) Tight fit (or) Press fit.

3. Transition Fit:

          It may result in either Clearence fit or Interference fit condition depending on the actual value of the individual tolerances of mating parts. This type of fit is used for applications where accurate location is important but either a small amount of clearence or interference is acceptable. 

Transition fit can be sub-classified as 

a) Push fit

b) Force fit

c) Wringing fit

4. Line Fit:

          The limits of size are so specified that a clearance or surface contact may result when mating parts are assembled.

ex: Shrink fit   

** credits: some definitions taken from ANSI text book.

                    Slideshare.net

DEFINITIONS OF LIMITS, FITS & TOLERANCES

Limits: 

          A useful definition is provided by McGraw Hill: "Two extreme permissible sizes of a part between which the actual size is contained, are called Limits".

Fits:

          The relationship between two parts, which are to be assembled, with respect to difference of their sizes, before assembly is called ''Fit'.

          It is the general term used to signify the range of tightness or looseness which will result from the application of a specific combination of allowances and tolerances in  mating parts [ANSI Y14. 5M-1982].

Tolerance:

          The total permissible variation of a size is called ''Tolerance''. It is the difference between maximum and minimum limit of size.

** credits: some definitions taken from ANSI text book.

CENTRIFUGAL MONOBLOCK PUMPS AND APPLICATIONS

What is a Monoblock Pump?

          Monoblock Pump is defined as, the prime mover of the pump i.e.,, the motor and the pump is assembled together within the same housing. In this type of pumps there is no need of any coupling between the motor shaft and pump shaft since the shafts are coupled directly. The main principle of monoblock of pump is to transmit power without any losses. 

          In Monoblock Pumps, Centrifugal monoblock pump is one of the common types. In a lot of places centrifugal pumps offers more benefits. Here are the benefits offered by these pumps:

1) Due to its compact size, it consumes less space.

2) There is no air lock problem in these types of pumps, because these have uni casing.

3) There is no centrifugal switch.

4) The pump has a balanced structure so there is no vibration and noise. Rigged construction that ensures longevity.

5) There is less maintenance & operation cost.

6) Bearings of the pump are water lubricated.

7) These pumps are self-supportive. This means that there is no requirement of installing any base plate or guards.

8) These pumps have the best hydraulic and suction lifting efficiency.

9) They are self priming. They are also put into use to pump water from well (Both shallow and deep wells) with built in Non return valves.

Applications:

          These pumps can be used at a variety of places to meet different water requirements. Below we mentioned some applications of these type of pumps:

a) Industrial and Public water supply.

b) Booster application

c) Sprinkler/Drip and Lift Irrigation

d) Dewatering of mines.

DIFFERENCE BETWEEN TOOTHED PULLEY AND FLAT BELT PULLEY

1) Flat Belt pulley's  are used inline shafting to transmit power in factories. They were also utilized in infinite farming, mining and work applications, like saw mills, water pumps and electrical generators. Whereas toothed pulleys are usually accustomed transmit direct motion for indexing. They are usually utilized in part of chains of gears. Camshafts of vehicles, miniature timing systems, and stepper motors often utilized these belts. Toothed pulley are called timer pulley also.

2) Flat belt pulley's doesn't have teeth (have no teeth), whereas toothed pulleys have teeth that match into an identical toothed counter.

3) Flat belts tend to slip on the pulley when heavy loads are applied, where as toothed belts haven't any slippage when properly tensioned. 

4) The toothed pulley is employed when correct transmission of the torque is required. A 100% accurate transmission of the torque is not possible by Flat belt pulley's or V-Belt pulley's, as a result of this there is always some (very little) slipping between the pulley and belt.

5) Toothed pulley's are more efficient because timing belts desires least tension of all belts where as flat belts desire more tension compared to toothed pulley.

6) Purchase cost of flat belt is less than toothed pulley.

These are the variations those i know, hope it will be useful to you.

:::FLANGES:::

          After welding, flange is the second most commonly utilized joining technique. Flanges are utilized when the joints are needed dismantling. It provides easy access for maintenance like cleaning, inspection and modifications. Flange connects the pipe with numerous equipment, pumps and valves to form piping. Breakup flanges are added in the pipeline system if regular maintenance is needed or necessary during plant operation.

          A flanged joint consists of three distinct and independent although interrelated segments; the flanges, the gaskets, and also the bolting; that are assembled by yet another influence, the fitter. Sometimes flanges are welded to the pipe lines too. Exceptional controls are needed in the selection and application of all these components to accomplish a joint. A gasket is placed between the two mating flanges which provide acceptable leak tightness.
          However, it is not recommended to used flanged connection in underground piping when it is yo be buried. There are a variety of flanges are available. Flanges are classified as following below:
          1. On the basis of type of connection
          2. Based on flange facing type
          3. Material type
          4. On the basis of Temperature and pressure Ratings