Section 8 - Milling Machines Flashcards
What does the feeding device of a rollermill consist of
A pair of feed rolls and a balanced feedgate system
What are the main types of fluting
Radiused groove, 1.5mm saw tooth, 3mm saw tooth, screw head
What is automatic feed roll adjustment
A feedgate that automatically opens and closes using a pneumatic servo control that opens and closes depending on the level of stock in the roll sightglass
What are the special features of a grind roll
Roll protection, roll gap adjustments, roll cleaning, discharge hopper, exhaust, control system
Can a roller mill run without feed?
NO! this would damage the roll surfaces, and cause heat build up which could present a fire risk.
What controls whether the grinding rolls are engaged
The pneumatic servo control - it disengages the rolls when there is no feed
Why is there automatic roll gap adjustment
Removes operator inconsistencies and improves mill balance, consistency of mill performance and finished flour quality
What cleans the rolls
Roll brushes and cleaners (scrapers)
What is roll ringing?
When there is too much build up on the rolls - it can affect mill performance and product quality and an increase in temp
What does a discharge hopper do
Collects the ground stock and directs
When are rollermills connected to a central exhaust
In mills with bucket elevators
What is perfect tram
Roll axes are in parallel
What expands more, the ends or centre of a roll
Ends
How do you combat roll expansion
A taper or camber
What were the different types of plansifter
Reels, Centrifugals, Free-swinging
Why are centrifugals better than plansifters
Simpler in design and more accessible
More effective way of dressing reduction stocks, particularly with soft wheats
A double collecting worm allowed complete freedom in division of stocks
Advantages of Plansifters over centrifugals
Occupy less space
Use less power
Lower capital cost
Dressing surface is more effectively used
Gentle rotary motion makes the stock much cleaner
Covers are more easily changed
More stock separation can be achieved
Efficiency of throughs dressing is increased with pneumatic conveying
What is the set up of a free swinging plansifter and a drawer type plansifter
Suspended from girders by 4 sets of canes
driven by a central vertical shaft
driven from either a motor mounted on steelwork above, or a motor built in the sifter frame
What affects the ‘throw’ of a sifter
The balance weight adjustment
What are the advantages of a buhler planostar type MPAD
Sieves and sieve frames may be individually removed
The flow partitions and channels may be quickly changed
Maintenance can be carried out by one person
Wear on sieve covers is reduced
Why was the square sieve plansifter developed
To achieve higher capacities within one machine
What advantages do square sieve plansifters have over free-swinging plansifters
Increased sieving efficiency so fewer sections required for each passage
A section can be taken down and cleaned in 1/4 of the time it takes to dismantle older machines
Flow is easily altered
Less time is lost on burst covers
Sieve cleaners are more efficient and less prone to sticking
Less spouting required
Easier to maintain
Greater flexibility due to more separation
take up less space
Benefits of a square sieve plansifter
More sieve dressing area
Higher capacity
Greater flexibility to change internal stock flow
How many nests, sections and sieves can be in a plansifter
2, 3, 4 or 5 nests
4, 6, 8 or 10 sections
up to 30 sieves
