Posted tagged ‘mass’

Vertical screw conveyors

September 8, 2011


01-Vertical screw conveyors- Vertical screw pump- Vertical screw conveyor design- Vertical screw conveyor calculations

A vertical screw conveyor conveys material upward in a vertical path. It requires less space than some other types of elevating conveyors. Vertical screw conveyor can handle most of the bulk materials provided there is no large lump. The maximum height is usually limited to 30m.

A vertical screw conveyor consists of a screw rotating in a vertical casing. The top bearing for the screw shaft must be designed to stand against radial and thrust loads. A suitable inlet port at the lower end and a discharge port at the upper end of the casing are provided. Feeding a vertical screw conveyor deserves careful consideration. Most materials are fed to the vertical conveyor by a straight or offset horizontal feeder conveyor. The ideal operation of a vertical screw conveyor is to have a controlled and uniform volume of material feeding.

Uneven feeding and start stop operation may adversely affect the performance of the vertical screw conveyor in terms of speed, capacity and horse power.

Average capacities and speeds of vertical conveyor

Nominal diameter of screw in mm Capacities in m3/hr Speed of screw
150 10 Up to 400 RPM
250 35 300 RPM
300 75 250 RPM
400 170 200 RPM

Vertical screw conveyors or some special design of vertical screw conveyor finds wide application in ship unloading.

01-Vertical screw lift- Vertical screw elevator- Vertical screw feeder- vertical screw conveyor-vertical screw pump

Practical experience with these conveyors has shown that the resistance factor for vertical conveyors is higher than those of the horizontal conveyors. Resistance factor λ may be taken as 5.5 to 7.5 for grains. 6.5 to 8.3 for salt.

01-screw conveyor design calculation- screw conveyor power calculation- screw conveyor efficiency- screw conveyor theory- screw conveyor formulae- screw conveyor flow rates

The driving power of the loaded screw conveyor is given by:

P = PH + PN + Pst

Where,

PH = Power necessary for the progress of the material

PN = Driving power of the screw conveyor at no load

Pst = Power requirement for the inclination of the conveyor

Power necessary for the progress of the material PH:

For a length L of the screw conveyor (feeder), the power PH in kilo watts is the product of the mass flow rate of the material by the length L and an artificial friction coefficient λ, also called the progress resistance coefficient.

PH = Im.L. λ.g / 3600 (kilowatt)

= Im.L. λ / 367 (kilowatt)

Where,

Im = Mass flow rate in t/hr

λ = Progress resistance coefficient

Each material has its own coefficient λ. It is generally of the order of 2 to 4. For materials like rock salt etc, the mean value of λ is 2.5. For gypsum, lumpy or dry fine clay, foundry sand, cement, ash, lime, large grain ordinary sand, the mean value of λ is 4.0.

In this connection it should be noted that the sliding of the material particles against each other gives rise to internal friction. Other resistance due to grading or shape of the output discharge pattern contributes to the resistance factor. That is why the parameter λ is always higher than that due to pure friction.

Drive power of the screw conveyor at no load, PN:

This power requirement is very low and is proportional to the nominal diameter and length of the screw.

PN = D.L / 20 (Kilowatt)

Where,

D = Nominal diameter of screw in meter

L = Length of screw conveyor in meter

Power due to inclination: Pst

This power requirement will be the product of the mass flow rate by the height H and the acceleration due to gravity g.

Pst = Im.H.g / 3600

= Im.H / 367

H should be taken positive for ascending screws and will be negative for descending screws.

Total power requirement:

The total power requirement is the sum total of the above items

P = (Im (λ.L + H) / 367) + (D.L /20) (Kilowatt)

HYDRATION SYSTEM

August 23, 2011

04-The Future Of Bicycling Hydration, Bicycle Mounted Hydration System, Hydration System Mounts On The Bicycle Rear

Is it possible to drink too much water during ride without stop the vehicle?

Adequate hydration is as important as calorie replacement to an athlete’s performance, yet dehydration continues to be a condition many experience. This is especially true in cycling where evaporative losses are significant and can go unnoticed. Sweat production and losses through breathing can exceed 2 quarts per hour. To maximize your performance pre-hydration is important, and it is essential that fluid replacement begin early and continue throughout a ride.

Approximately 75% of the energy your body produces is converted to heat rather than being delivered to your muscles to power your pedal stroke. Keeping your body cool and re-hydrated during exertion will result in greater efficiency, higher power output, extended endurance, and a quicker, more thorough recovery. Say good-bye to the Wet Spot!


Individual fluid and electrolyte needs are widely variable during physical exercise due to differences in metabolic rate, body mass and size, environmental conditions (e.g. temperature, humidity, wind, solar load, clothing worn), heat acclimatization status, physical fitness, activity duration, and genetic variability. Sweat rates can vary from 0.5L/hr to more than 3 L/hr. Similarly, sodium concentration may vary from less than 460 mg/L to more than 1840 mg/L

03-The Future Of Bicycling Hydration, Bicycle Mounted Hydration System, Hydration System Mounts On The Bicycle Rear

Technology:

Why use a perfectly good water bottle on your bike when you could use a complex, expensive and awkward to use “hydration system” instead? That’s the promise of the VelEau Bicycle Mounted Hydration System.

01-The Future Of Bicycling Hydration, Bicycle Mounted Hydration System, Hydration System Mounts On The Bicycle Rear

The VelEau comes in several parts. First, there’s a saddlebag which holds 42 ounces (1.4 liters) of water. Then there’s a tube through which you drink, much like those found on CamelBak water bags. This runs from under the seat, along the top-tube to the handlebars, where it is secured to a retracting cord on the stem. This cord pulls the mouthpiece back into place when you’re done drinking, where it is secured by magnets.

02-The Future Of Bicycling Hydration, Bicycle Mounted Hydration System, Hydration System Mounts On The Bicycle Rear

If that seems like it’s complex, unnecessarily heavy and annoying to use, that’s because it probably is. However, there is at least a compartment to carry a multi tool in the same bag, which adds some utility.

HYDRATION SYSTEM

August 23, 2011

04-The Future Of Bicycling Hydration, Bicycle Mounted Hydration System, Hydration System Mounts On The Bicycle Rear

Is it possible to drink too much water during ride without stop the vehicle?

Adequate hydration is as important as calorie replacement to an athlete’s performance, yet dehydration continues to be a condition many experience. This is especially true in cycling where evaporative losses are significant and can go unnoticed. Sweat production and losses through breathing can exceed 2 quarts per hour. To maximize your performance pre-hydration is important, and it is essential that fluid replacement begin early and continue throughout a ride.

Approximately 75% of the energy your body produces is converted to heat rather than being delivered to your muscles to power your pedal stroke. Keeping your body cool and re-hydrated during exertion will result in greater efficiency, higher power output, extended endurance, and a quicker, more thorough recovery. Say good-bye to the Wet Spot!


Individual fluid and electrolyte needs are widely variable during physical exercise due to differences in metabolic rate, body mass and size, environmental conditions (e.g. temperature, humidity, wind, solar load, clothing worn), heat acclimatization status, physical fitness, activity duration, and genetic variability. Sweat rates can vary from 0.5L/hr to more than 3 L/hr. Similarly, sodium concentration may vary from less than 460 mg/L to more than 1840 mg/L

03-The Future Of Bicycling Hydration, Bicycle Mounted Hydration System, Hydration System Mounts On The Bicycle Rear

Technology:

Why use a perfectly good water bottle on your bike when you could use a complex, expensive and awkward to use “hydration system” instead? That’s the promise of the VelEau Bicycle Mounted Hydration System.

01-The Future Of Bicycling Hydration, Bicycle Mounted Hydration System, Hydration System Mounts On The Bicycle Rear

The VelEau comes in several parts. First, there’s a saddlebag which holds 42 ounces (1.4 liters) of water. Then there’s a tube through which you drink, much like those found on CamelBak water bags. This runs from under the seat, along the top-tube to the handlebars, where it is secured to a retracting cord on the stem. This cord pulls the mouthpiece back into place when you’re done drinking, where it is secured by magnets.

02-The Future Of Bicycling Hydration, Bicycle Mounted Hydration System, Hydration System Mounts On The Bicycle Rear

If that seems like it’s complex, unnecessarily heavy and annoying to use, that’s because it probably is. However, there is at least a compartment to carry a multi tool in the same bag, which adds some utility.

BLOW MOULDING PROCESS

August 23, 2011

Today, when walking in your supermarket, it is increasingly difficult to find items packed in glass and jars.  Packaging for soft drinks, healthcare and beauty products, household chemicals and medicines, among other products, have switched from glass or metal to plastics.  Today the Blow Molding industry has expanded from simple plastic containers to plastic drums, gas tanks, automobile parts and toys in all shapes and sizes.

01-blow-molding-extrusion blow molding-injection blow molding-parison extrusion


Blow Molding (BM) process makes it possible to manufacture molded products economically, in unlimited quantities, with virtually no finishing required.  The basic process of blow molding involves a softened thermoplastic hollow form which is inflated against the cooled surface of a closed mold.  The expanded plastic form solidifies  into a hollow product.

Blow molded components are now seen all over the markets and industries for traditional materials, particularly in liquid packaging applications.  The last few decades saw the introduction of  Poly Ethylene (PE) squeeze bottles for washing liquids, Poly Vinyl Chloride (PVC) for cooking oil and fruits squash bottles, and Poly Ethylene Terephthalate (PET) for carbonated beverage bottles.  Nowadays, it is also used for the production of toys, automobile parts, accessories and many engineering components.

There are basically four types of blow moulding used in the production of plastic bottles, jugs and jars. These four types are:

  1. Extrusion blow molding,
  2. Injection blow molding,
  3. Stretch blow molding and
  4. Reheat and blow molding.

Extrusion blow molding is perhaps the simplest type of blow molding, whereby a hot tube of plastic material is dropped from an extruder and captured in a water cooled mold. Once the molds are closed, air is injected through the top or the neck of the container; just as if one were blowing up a balloon. When the hot plastic material is blown up and touches the walls of the mold the material “freezes” and the container now maintains its rigid shape. There are various types of shuttle, reciprocating and wheel style machines for the production of extrusion blown bottles. Shuttle or reciprocating type machines can be used for small, medium and high volume production with wheel machines being the most efficient for huge volume production of certain resins.


01-petblow-plastic products manufacturing-PET Preform-PET bottles-stretch blow molding

A typical apparatus consists of following major components i.e. blow pin, plunger, accumulator and lastly a mold.

Actually the process utilizes air pressure to inflate softened thermoplastic tube which is sealed at one end (also called as parision). This parision is constantly inflated and extruded. Then later on it is cut according to required dimensions. The temperature in Accumulator is maintained around 400 degree Celsius or so.

Stretch_blow_mold-dies-PET Pre form mold-household appliance mold

The mold consists of two split parts which have a semi-circular cross-section. Usually the air pressure which is applied in low pressure molding is about 50 to 250 psi. Various forms of blow molding used in industry today on a wide scale are Injection Blow Molding.

Injection Blow Molding though not used in industry, has very limited and specific applications like making small medicine plastic bottles etc. Extrusion blow molding is the simplest form of blow molding. A tube of plastic material which is generally maintained hot, is dropped from an extruder only to be captured in a water cooled mold. Once the molds are closed, air is injected through the top or the neck of the container and the tube is inflated just like a balloon. When the hot plastic material is blown up and touches the walls of the mold the material is cooled and the container now maintains a solid, rigid shape.

Now Stretch blow molding, this process requires the raw material to be formed in a pre-form using injection molding and later on stretch blow molding process can be applied.

The product range varies from various cylindrical components like bottles, cans, floats heater ducts in automobile parts and various small pipe fittings and hollow cylindrical parts can be produced in mass production.

The advantages are many like the tooling costs are very less as compared to injection molding, the part performance is excellent under pressure. Then the products have excellent environmental stress crack resistance. The products also perform excellently in high speed impact strength than even the metal components the process can be automated and used in mass production.

The disadvantages mainly raise environmental concerns. It depends on petroleum industry as any plastic industry depends. Also the cylindrical shapes are delicate so if the dimensions are not accurate then they result in scrap.