309 Questions
What is the primary purpose of Particle Size Reduction (PSR)?
To reduce large solid unit masses to smaller unit masses by mechanical means
How can Particle Size Distribution (PSD) impact drug product performance?
It can affect dissolution, bioavailability, content uniformity, stability, and powder flow characteristics
How can PSDs of both drug substance and excipients affect drug product manufacturability?
By affecting flowability, blend uniformity, and compactibility
Particle Size Distribution (PSDs) can affect impact safety, efficacy and quality of the drug product
True
PSDs of pharmaceutical powders can influence granulation, milling, coating, drying, mixing/premixing, encapsulation processes and compression
True
Particle Sizes of pharmaceutical powders should be evaluated at different pharmaceutical development phases for each specific drug application.
True
The target PSDs of pharmaceutical powders can be selected after determining the particle size effects in the final development phase.
True
Establishing appropriate particle size specifications helps in controlling drug product quality and ensuring manufacturing consistency.
True
What can be done once the particle size effects have been determined in the final development phase?
Select target PSDs of pharmaceutical powders and establish appropriate particle size specifications
What is the purpose of establishing appropriate particle size specifications?
To control drug product quality and ensure manufacturing consistency
What is the primary purpose of size reduction in pharmaceutical manufacturing?
To reduce solid particles to the required size for incorporation into finished products
How does the range of mechanical properties of solid particles influence size reduction mechanisms?
It determines the specific mechanisms needed for size reduction
Why does the range of mechanical properties of solid particles influence the design of commercial equipment?
To ensure efficient size reduction based on material properties
What does the method of size reduction affect?
Mean particle size and distribution of powdered material sizes
Why does the correct choice of efficient commercial size reduction machinery depend on knowledge of particle size properties and mechanisms?
To ensure effective reduction of particle sizes and distribution
Which factor determines the required size of a drug for a dry powder inhalation formulation?
Subsequent usage of the material
What influences the design of commercial size separation methodologies and apparatus?
Final required particle size and size of the commercial batch
Which method is NOT Correct as a commercial size separation methodology ?
Milling
What is the primary purpose of pharmaceutical particle technology?
To improve poor aqueous solubility of drug compounds
What does pharmaceutical particle technology aim to produce?
Solid, powdered form of drugs readily soluble in water
What are the primary targets of pharmaceutical particle technology?
Modify the solubility properties of drugs
What is a limitation of vivo bioavailability of pharmaceutical particle technology?
Low disssolution rate in the gastrointestinal fluids
What is the primary advantage of newer novel particle techniques over conventional methods?
Overcoming limitations of conventional methods
What is the main purpose of size reduction in pharmaceutical manufacturing?
Increase the surface area and enhance solubility
What is the primary purpose of size reduction in pharmaceutical manufacturing?
To reduce the drug particle size and increase the surface area to enhance solubility and dissolution
What is a limitation of conventional particle technologies ?
Limited efficiency for some drugs
What is the main advantage of newer novel particle techniques over conventional methods?
Overcoming limitations of conventional methods and being more efficient for poorly soluble drugs
When is a particle size specification needed ?
When the particle size is critical to drug product performance or manufacturability
Conventional methods of size reduction can sometimes lead to thermal and chemical degradation of drugs
True
Newer novel particle techniques are less efficient than conventional methods for formulating poorly soluble drugs
False
Particle size specification is required if the particle size of the drug substance is critical to drug product performance
True
If the drug product is not a low dose drug and the drug substance is highly soluble, the particle size specification may NOT be established with little or no scientific justification
True
Granulation and coating are related to particle size enlargement, while milling and grinding are related to particle size reduction
True
Mixing and blending are related to combination of particles of different components where size differences among these components have a large impact on blend homogeneity
True
Screening and sieving are related to separation of particles with different sizes
True
What are granulation and coating related to in pharmaceutical particle technology?
Particle size enlargement
What are screening and sieving related to in pharmaceutical particle technology?
Particle separation
What are mixing and blending related to in pharmaceutical particle technology?
Combination of particles of different components
Particle size specification is only required for the drug substance and not for excipients or in-process materials.
False
Particle size of pharmaceutical materials can range from nanometer to centimeter.
True
Mixing and blending in pharmaceutical particle technology are not affected by the size differences among the components.
False
Size reduction increases the solubility and dissolution rate of pharmaceutical materials, enhancing bioavailability.
True
Griseofulvin, an antifungal drug, shows around five times better absorption in its micronized form.
True
The absorptive power of charcoal and kaolin increases after size reduction due to the increase in surface area.
True
What is the impact of size reduction on pharmaceutical formulation?
It increases surface area, enhancing solubility and dissolution rate
Which substance shows around five times better absorption in its micronized form after size reduction?
Griseofulvin, an antifungal drug
What happens to the absorptive power of charcoal and kaolin after size reduction?
It increases due to the increase in surface area
What is the primary purpose of controlling particle size distribution in pharmaceutical suspensions?
To reduce the rate of sedimentation
How does controlling particle size distribution impact the flowability of materials in a tablet machine?
It improves flowability due to decreasing PSD
What is the purpose of controlling particle size distribution in dry granulation or dry mix in pharmaceutical manufacturing?
To minimize segregation while handling and tableting
Particle size for pharmaceutical capsules, insufflations, suppositories, and ointments must be below 10mm.
True
Lack of grittiness of solid particles is a concern for dermal ointments, creams, and ophthalmic preparations.
True
Fine powders have a particle size of 50 to 100 µm.
True
Particle Size Reduction can lead to a decrease in bulk density causing flowability issues.
True
Particle Size Reduction can lead to an increase in dissolution rate.
False
Particle Size Reduction can lead to a decrease in static charge problems.
False
Which of the following correct is a potential disadvantage of Particle Size Reduction (PSR) in pharmaceutical manufacturing?
Possible degradation of the drug due to heat build up during milling
How does a decrease in bulk density due to Particle Size Reduction (PSR) impact material flowability?
It may cause problems in the flowability of material
What problem may arise from a decrease in particle size due to Particle Size Reduction (PSR) in pharmaceutical manufacturing?
Static charge problems causing small drug particles to agglomerate
Which type of materials are most difficult to comminute?
Hard materials
What type of mill is suitable for size reduction of fibrous materials?
Cutter mill
What should be done before milling plastic materials like synthetic gums and resins?
Chill (make cold) the materials
Hard materials like pumice and iodine are easy to comminute due to their soft nature.
False
Fibrous materials like glycyrrhiza and rauwolfia can be size reduced by pressure.
False (correct answer Reduce by cutter mill)
Plastic materials like synthetic gums, waxes, and resins should be chilled before milling.
True
Hygroscopic materials must be comminuted inside a closed equipment like a ball mill because they absorb moisture rapidly.
True
Thermolabile materials like vitamins and antibiotics are milled inside chilled equipment.
True
Fine dust, such as dextrin, starch and sulphur, is a potential explosive mixture under certain conditions.
True
Why must hygroscopic materials be comminuted inside a closed equipment like a ball mill?
Because they absorb moisture rapidly
What type of equipment is suitable for milling thermolabile materials like vitamins and antibiotics?
Chilled equipment
Why should fine dust inflammable materials be handled with caution in milling processes?
They can form explosive mixtures under certain conditions
What is the suitable moisture content for materials to be ground dry?
Less than 5%
How does moisture content influence the milling process?
It produces a sticky mass
What properties does moisture content influence that can affect size reduction?
Hardness, toughness, or stickiness
Moisture content more 5% enhances the milling process and improves the particle size reduction
False
Less than 5% moisture is suitable for dry grinding of substances
True
More than 50% moisture is suitable for wet grinding of substances
True
What is the difference between hardness and toughness of a material?
Hardness is the surface property of a material, while toughness is the ability of a material to resist fracture
Why might a soft but tough material present more problems in size reduction than a hard but brittle substance?
Soft but tough materials may be difficult to break despite their softness
How does moisture content relate to the toughness of pharmaceutical materials?
Moisture content can impact the toughness of pharmaceutical materials, particularly in fibrous drugs
Harder materials are generally easier to reduce in size than softer materials.
False
Toughness is more important than hardness in size reduction of pharmaceutical materials.
True
Moisture content has no impact on the size reduction process of pharmaceutical materials.
False
Stickiness causes considerable difficulty in size reduction process.
True
The final powder may be contaminated with more than 0.1 percent of metal worn from the grinding mill when grinding abrasive substances.
True
The reverse of stickiness, which can be described as slipperiness, always makes size reduction process more efficient.
False (correct answer lower efficient)
What property causes difficulty in size reduction as material may adhere to the grinding surfaces or meshes of the screen?
Stickiness
Which substance may be added to assist in size reduction of gummy or resinous materials?
Kaolin
What may limit the type of machinery that can be used for hard materials during size reduction?
Abrasiveness
What is a potential concern when milling waxy substances or drugs containing oils or fats?
Generation of heat causing softening
How can the softening temperature issue be addressed during the size reduction process?
Cooling the mill with water jacket or air stream
Which type of substances may be affected by the softening temperature issue during size reduction?
Waxy substances and drugs containing oils or fats
Cooling the mill can be used to overcome the softening temperature issue during size reduction
True
Cellulose is classified as a soft material in terms of hardness
False (correct answer Moderately hard to brittle )
Amobarbital is classified as an abrasive material in terms of hardness
True
Cellulose is classified as a soft material in terms of hardness
False
Sucrose is classified as a hard material in terms of hardness
True
Kaolin is classified as a moderately hard to brittle material
False (correct answer Hard )
Which pharmaceutical material is classified as 'soft but plastic' in terms of hardness?
Boric acid
Which pharmaceutical material is classified as 'abrasive very hard' in terms of hardness?
Calactate
Which pharmaceutical material is classified as 'moderately hard to brittle' in terms of hardness?
B+D
What type of mill is suitable for obtaining very fine particles like micronized griseofulvin?
Fluid energy mill
Why should size reduction be conducted in a sterile environment for preparations intended for injection or ophthalmic uses?
To prevent contamination of milled materials
What type of equipment may be used for milling potent drugs and low dose products to avoid contamination?
Fluid energy mill
Particle size reduction is not important in pharmaceutical manufacturing.
False
Particle size reduction is necessary for parenteral and ophthalmic preparations.
True
Contamination of milled materials is not a concern for potent drugs and low dose products.
False
Which of the following is a principal means of size reduction ?
Shearing
What is the term used for rubbing and grinding as a means of size reduction?
Attrition
What is the term used for size reduction by applying pressure?
Compression
Size reduction can be accomplished by cutting, shearing, compression, impaction, and attrition.
True
Grinding and trituration are not means of size reduction.
False
Is compression a commonly used mechanism of size reduction in pharmaceutical manufacturing?
False
Which mechanism of size reduction involves crushing the material by application of pressure?
Compression
Which mechanism of size reduction involves crushing the material by means of a sharp blade or blades?
Cutting
Why might a soft but tough material present more problems in size reduction than a hard but brittle substance?
It adheres to the grinding surfaces or meshes of the screen
What type of forces break the particles in the process of attrition?
Shear forces
In which scenario does impact occur during size reduction?
When the material is stationary and is hit by an object moving at high speed
What happens to the material in impact during size reduction?
It shatters to smaller pieces
Which methods are used much more widely for size reduction in Pharmaceutical practice?
Impact and attrition
What type of machines are often termed as Mills for size reduction in Pharmaceutical practice?
Mills
Which methods are of limited use in Pharmaceutical practice for size reduction?
Cutting and compression
Which of the following correct depend rate peocess of size reduction on?
The size of the starting material, the feed
Which factor influences the orientation of the material in the crushing machine during size reduction?
Type of size reduction machine
What is a critical aspect that affects size reduction according to ?
The time of milling to which these materials are subjected
Which factor influences the selection of size reduction equipment for materials?
Moisture content and particle size distribution
What determines whether a machine hard enough to withstand abrasion effect is used for size reduction?
Range of abrasion of the material
Why is knowledge of particle size properties and mechanisms important in selecting efficient commercial size reduction machinery?
To make the correct choice based on material properties
What is a key factor to consider when selecting size reduction equipment?
Moisture content of the material
Which factor determines whether fine or large particles are needed as the final product?
Particle size distribution and shape
What influences the selection of equipment to withstand abrasion effects?
Structure, strength, friability, stickiness
Moisture content of the material does not influence the selection of size reduction equipment
False
Particle size distribution does not influence the selection of size reduction equipment
False
Coarse particles have no applications in pharmacy as blake jaw crusher, Dodge crusher, Gyratory crusher, and Rotary coal breaker.
True
Intermediate particles include Hammer mills, Cutting mills, Edge and end runner mills.
True
Ball mill, Fluid energy mill, and Oscillating granulator are used for producing fine particles.
True
Which type of equipment is suitable for reducing intermediate particles?
Hammer mills
Which particle size reduction equipment is suitable for fine particles?
Ball mill
Which type of particles have no applications in pharmacy?
Coarse particles
What type of size reduction mechanism is used in a hammer mill?
Impact
How are particles retained within a hammer mill during milling?
By a screen
What type of slots are often used in the screen of a hammer mill to allow particles to pass through?
Square, rectangular or herringbone slots
What happens to particle inertia as size reduction continues in a hammer mill?
It reduces markedly
Hammer mill uses a series of hammers hinged on a central shaft for size reduction by impact.
True
The angular velocity of the hammers in a hammer mill produces a strain rate of up to 80 s−1.
True
Particles passing through a given mesh in a hammer mill can be much finer than the mesh apertures.
True
Hammer mills tend to produce powders with broad size distributions.
False
Is a hammer mill capable of being used as a primary, secondary, or tertiary crusher?
True
Can small hammer mills be operated on household current?
True
Does the screenless hammer mill use air flow to separate small particles from larger ones?
True
What type of motors can be used to drive large hammer mills used in automobile shredders?
Electric motors ranging from 2000 to over 5000 horsepower
What type of power source can small hammer mills used as crushers be operated on?
Household current
How does the screenless hammer mill separate small particles from larger ones?
Uses air flow to separate small particles from larger ones
Is it possible to obtain different particle sizes by changing the screen, nature of the hammers, and driving force in size reduction equipment?
True
TRUE OR FALSE : hammer mill is essentially a steel drum containing a vertical or horizontal rotating shaft or drum on which hammers are mounted?
True
What is the primary purpose of using a hammer mill in the pharmaceutical industry?
To reduce API particle size and maintain consistent distribution for solid dosage forms
What type of pharmaceutical materials are not suitable for size reduction using a hammer mill?
Sticky materials that can choke the screen
What particle size range can be achieved using a hammer mill in pharmaceutical applications?
20 to 40 microns
What type of materials can be milled by hammer mills?
Dry, wet, brittle, and fibrous materials
In which industry is impact size reduction primarily done by hammer mills?
Pharmaceutical industry
What is the primary purpose of using a hammer mill in the pharmaceutical industry?
Size reduction and granulation
Hammer mills can only be used for milling dry materials.
False
Particle size reduction is not important in the pharmaceutical industry.
False
Moisture content does not affect the size reduction process of pharmaceutical materials.
False
What is the primary purpose of using a hammer mill in the pharmaceutical industry?
To achieve impact size reduction for conventional size reduction of pharmaceutical materials
What type of materials can be milled by the hammer mills?
Brittle and fibrous materials
What is the impact of hammer mill on agglomerates?
Reduces agglomerates resulting in lower particle size distribution
Which of the following correct advantage of using a hammer mill for particle size reduction?
It is rapid in action and can grind various materials
How is the particle size of material controlled in a hammer mill?
By changing the speed of the rotor, hammer type, shape, and size of the screen
What is a feature of the operation of a hammer mill for particle size reduction?
The operation is continuous and easy to install and operate
What is a potential issue with the high speed of operation in a hammer mill?
Generation of heat affecting thermo labile materials or drugs containing gum, fat, or resin
How can the potential damage by foreign objects such as stones or metal in the feed be minimized in a hammer mill?
Using magnets to remove iron and visually checking the feed for any other contamination
What must be controlled carefully to prevent choking and decreased efficiency in a hammer mill?
The rate of feed
What type of equipment is suitable for reducing intermediate particles?
Cutter mill
What property causes difficulty in size reduction as material may adhere to the grinding surfaces or meshes of the screen?
Stickiness
What is the term used for size reduction by applying pressure?
Compression
What determines particle size in a Cutter Mill?
Rotor size
What is the pharmaceutical use of a Cutter Mill?
Milling tough materials
Which factor determines particle size in a hammer mill?
Gap between the two sets of knives
Which of the following correct advantage of using a Cutter Mill for size reduction?
Effective for tough, fibrous, or resilient materials
Why is a Cutter Mill not suitable for most pharmaceutical applications?
Formation of wide particle sizes
Which of the following correct disadvantage of using a Cutter Mill for size reduction?
Not easy to clean after use
Is Cutter Mill the best option for size reduction when impaction, attrition, or compaction type milling is not effective, especially for tough, fibrous, or resilient materials?
True
Is Cutter Mill suitable for most pharmaceutical applications due to the formation of wide particles size?
False
TRUE OR FALSE : Cutter Mill equipment is not expensive
True
Which method is known for preparing nanosuspensions of drugs with poor water solubility?
High pressure homogenization
What advantage does High pressure homogenization (HPH) offer over conventional size reducing methods?
Effective size reduction to the nanosize range
What is a reported improvement resulting from the use of High pressure homogenization (HPH)?
Improved dissolution rate and bioavailability
High pressure homogenization (HPH) is a top down technology used for preparing nanosuspensions of drugs with poor water solubility.
True
HPH is particularly advantageous for comminution of drug particles because it overcomes the drawbacks of conventional size reducing methods.
True
Fluid energy milling is also known as air jet milling
True
In fluid energy milling, particle size reduction is brought about by a combination of impact and attrition
True
A classifier may be integrated into the milling system to remove particles above a predefined cut-off size
True
Fluid energy milling can effectively reduce the size of drug particles to less than 20 μm
False
What is the primary mechanism of particle size reduction in fluid energy milling?
Impact and attrition
What role does a classifier play in fluid energy milling?
Removing particles below a certain size
What is the purpose of high velocity compressed air streams in fluid energy milling?
Accelerating particles and causing collisions
How does attrition contribute to particle size reduction in fluid energy milling?
Shear forces from rapid movement break particles
Fluid energy milling is suitable for meltable materials and heatsensitive drugs.
True
Raw materials are introduced into the violent and turbulent air stream in fluid energy milling.
True
Particle size reduction in fluid energy milling is brought about by a combination of impact and attrition.
True
High Pressure Homogenization (HPH) is not suitable for formulating parenteral formulations due to risk of contamination from milling media.
False
HPH has been successfully demonstrated to formulate nano suspensions of poorly soluble drugs like prednisolone and carbamazepine for parenteral administration.
True
HPH can protect from microbial contamination by eliminating potential contaminants in the high pressure environment.
True
What is a reported improvement resulting from the use of High pressure homogenization (HPH)?
Improved dissolution rate and bioavailability of poorly water soluble drugs
Which method is known for preparing nanosuspensions of drugs with poor water solubility?
High pressure homogenization (HPH)
Why is High pressure homogenization (HPH) considered suitable for formulating parenteral formulations?
Eliminates potential contaminants by protecting from microbial contamination
What is the reported improvement resulting from the use of High pressure homogenization (HPH)?
Enhanced dissolution and improved saturation solubility
What has been suggested about High pressure homogenization (HPH) as a technique?
Simple, adequate, easily scaled up, and having general applicability
What did the formulation of nifedipine as nanoparticles demonstrate?
Enhanced dissolution and improved saturation solubility
Is milling immediate due to high-velocity collisions between particles suspended in the air stream?
True
Are grinding nozzles used to increase particle velocity and impact energy in the milling process?
True
Does the classifier remove smaller particles in the fluid energy milling process?
True
What is the purpose of the grinding nozzles in fluid energy milling?
To increase the particle velocity and impact energy
What is the function of the classifier in fluid energy milling?
To remove the smaller particles from the powder
Why are hygroscopic materials recommended to be comminuted inside closed equipment like a ball mill?
To prevent moisture absorption during milling
Which of the following correct of micronizing pharmaceutical ingredients?
Enhancing solubility and improving bioavailability
How is micronization achieved in pharmaceutical manufacturing?
High pressure air/gas causing particle to particle collision
What impact does particle size reduction have on the manufacturing of finished dosage forms?
It could be improved with a reproducible and controlled particle size
What does a high feed rate result in during particle size reduction?
Larger particle size
Which factor does not influence the particle size during milling?
Moisture content of the material
What is one of the factors that influences particle size during milling?
Feed rate
Particle size depends on the configuration of the mill, feed size, position of the nozzles, design of the classifier, and feed rate.
True
A high feed rate can result in larger particle size in the size reduction process.
True
A slow feed rate can result in smaller particle size in the size reduction process.
True
Is fluid energy milling suitable for milling soft, tacky, fibrous materials?
False
Does fluid energy milling use inert gases to minimize or eliminate oxidation of susceptible compounds?
True
Does fluid energy milling produce very small and uniformly distributed particles?
True
Which of the following correct advantage does fluid energy milling offer in terms of heat-labile substances?
It can be milled with little danger of thermal degradation due to the cooling effect of the air and rapid heat exchange
What is a potential benefit of using inert gases instead of air in fluid energy milling?
Minimize or eliminate the oxidation of susceptible compounds
What type of materials are recommended for ultra-fine grinding using fluid energy milling?
Moderately hard materials
Which of the following correct disadvantage of fluid energy milling?
Not suitable for milling soft, tacky, and fibrous material
Why is fluid energy milling considered expensive?
It needs additional accessories like a fluid energy source and dust collection equipment
The equipment for fluid energy milling is expensive because it requires additional accessories like fluid energy source and dust collection equipment.
True
Ball milling is primarily used for pharmaceutical and cosmetic products.
True
Ball milling can be used for particle size reduction, mixing, blending, and dispersing of materials.
True
Particle size reduction is not an important application of ball mills.
False
What are the applications of ball mills ?
Particle size reduction, mixing, blending, dispersing
In which industries are ball mills widely used?
Pharmaceutics and cosmetics
Which of the following correct technological process applied in ball mills?
Grinding to reduce particle size
What is the primary purpose of a ball milling device of particle size reduction?
To transfer kinetic energy of the grinding media into the grinding product
What is the function of the cylindrical vessel in a ball milling device?
To allow rotation of the vessel around the center axis
What initiates the milling process in a ball milling device?
Rotation of the vessel with charged material and grinding media
A ball milling device is not capable of controlling the particle size of the material being milled
False
What is the primary purpose of a ball milling device?
To transfer kinetic energy to the grinding product
What takes place during the milling process in a ball milling device?
Transfer of kinetic energy from grinding media
What is the function of the grinding media in a ball milling device?
To provide kinetic energy for milling process
What is the primary mechanism by which a ball mill produces size reduction?
Impact and attrition
What percentage of the total volume do the balls typically occupy in a ball mill?
30-50%
What is the purpose of having balls with different diameters in a ball mill?
To break down coarse feed materials and form fine product
Why is the amount of material in a ball mill of considerable importance?
Too much feed produces a cushioning effect and too little causes loss of efficiency
What is the factor of greatest importance in the operation of a ball mill?
Speed of rotation
At what angular velocity do balls in the ball mill move with the drum until gravity exceeds frictional force?
Low angular velocities
At what point does a cascading action occur in the ball mill?
Two thirds of the critical angular velocity
What is the optimum rate of rotation dependent on in a ball mill?
Mill diameter
What factor is of greatest importance in the operation of the ball mill for efficient size reduction?
Speed of rotation
At what angular velocity do the balls in the ball mill experience a cascading action for efficient size reduction?
Two thirds of the critical angular velocity
What occurs when the balls in the ball mill are thrown out to the mill wall at high angular velocities?
They remain due to centrifugal force and no size reduction occurs
What is the optimum rate of rotation for a ball mill dependent on?
Mill diameter
The optimum rate of rotation is usually of the order of 0.5 revolutions per second.
True
What are the three types of grinding media commonly used in ball mills?
Steel and other metal balls, metal cylindrical bodies, ceramic balls
What is the most frequently used type of grinding media in ball mills?
Steel and other metal balls
What is the range of ball sizes commonly used as grinding media in ball mills?
10 to 150 mm in diameter
Which of the following correct types of grinding media commonly used in ball mills?
All of the above
What happens at and above the critical speed in a ball mill?
No significant size reduction occurs
What is the primary combination of actions involved in ball milling?
Impact and attrition
The critical speed of a ball mill is the speed at which the balls just begin to centrifuge with the mill.
True
At and above the critical speed, significant size reduction occurs.
False
Ball mills are operated from 60 to 85% of the critical speed.
True
For a given feed, smaller balls give a slower but finer grinding.
True
What is the empiric rule for the optimum speed of a ball mill?
n = 57 - 40 log D
What percentage of the critical speed are ball mills typically operated from?
60 to 85%
How do smaller balls affect the grinding process in a ball mill?
Slower but finer grinding
Which of the following correct of critical speed depend on ?
Chamber size, grinding media size, material shape, density, and size distribution
What influences the size of the product in a ball mill?
Rate of feed, weight of balls, diameter of the balls, mill slope, discharge freedom, and speed
Critical Speed in a ball mill depends on the chamber size, grinding media size, and material characteristics.
True
The rate of feed, weight of balls, and discharge freedom are factors influencing the size of the product in a ball mill.
True
Ball mill can only be used for dry grinding processes.
False
Rod or bars can also be used as grinding media in a ball mill.
True
Installation, operation and labour costs are high for a ball mill.
False
Is the ball mill a very noisy machine?
True
Is the ball mill a slow process?
True
Can soft, tacky, fibrous material be milled by ball mill?
False
What is the principle of operation of the oscillating granulator?
Shearing with some attrition
What is the product size obtained from the oscillating granulator?
0.3 mm
What type of materials can the oscillating granulator be used for?
Wet and dry granulations
What type of equipment can be used for direct collection of wet granulations?
Trays
What is the primary function of the specially fitted collector funnel mentioned in the text?
Minimize dust
What part of the equipment allows for interchangeability and production of particles with desired size?
Screens
How are particles fractured in attrition methods?
By rubbing and grinding
What type of materials are roller mills primarily used for?
Solids in suspensions, pastes or ointments
What is the typical range of particle size achievable with roller mills?
1 - 200 µm
What is the primary function of a colloid mill?
To reduce the size of suspended droplets
In a colloid mill, what happens when the heavier liquid is added to the chamber?
It performs the shearing process
In some models of colloid mills, what remains constant while the milling process takes place?
Stator
What type of device is a colloid mill?
Hydraulic shear producing device
Colloid mills work by passing the material through the narrow gap between the rotor and stator to reduce particle size:
True
In some models of colloid mills, the stator remains constant while the rotor rotates:
True
The primary function of the specially fitted collector funnel in the colloid mill is to collect the milled material:
True
The process of colloid milling is done through the addition of the heavier liquid into the chamber of the mill that performs the shearing process:
True
Colloid mills are used for dispersion of solid particles within a liquid.
True
Colloid mills can be used to increase the stability of suspensions and emulsions.
True
High levels of hydraulic shear are applied to the process liquid in a colloid mill.
True
What is the primary purpose of a colloid mill?
To produce colloidal suspensions, emulsions, and solid dispersions
What controls the particle size produced by a colloid mill?
Rotor speed
Why must a colloid mill be jacketed and cooled during operation?
To absorb the large amount of heat produced during operation
Colloid mills can produce colloidal suspensions, emulsions, and solid dispersions by means of high shear forces
True
The rotor and stator in a colloid mill can be adjusted to create a very small clearance for producing fine particles
True
A large amount of heat can be produced during the operation of a colloid mill, necessitating the need for jacketing and cooling
True
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