MUSTHAVE

SHOULD

HAVE

COULDHAVE

Module # 040

PAC Algorithms Which one to use?

• Objective:• Know when to use which algorithm.• Know how each Algorithm behaves.

Configuration & Setup Sequence

• Plan hardware options (scale, flowmeter cards, etc)• Construct (install cards)• Calibrate instruments• ------------------------------------------------------------------------------• Plan PAC configuration (# Material Paths, Channels)• Configure PAC database• Commision Materials and Channels• Optimize PAC parameters• ------------------------------------------------------------------------------

Control

Hardware

PAC Algorithms Which one to use?• There are three types of Gain in Weight (GIW)

Algorithms– Spill (short or erratic behavior)– K1 (most common)– K2 (fast feeds, downwards into scale)

• These are your Loss in Weight (LIW) options– Spill– K1 (and less often, K2)– Dump to Empty (DTE)

Behaviour

• Spill – The results of the previous feed are used to adjust the cutoff point of the next feed. Flow rate of the material is not monitored.

• K1 – The cutoff point is adjusted as the Flow Rate varies during the feed. This is a dynamic behaviour.

• K2 – The cutoff point is adjusted as the Flow Rate varies during the feed. This is a dynamic behaviour.

• Dump to Empty – the Qi will attempt to completely empty the scale. A target value is ignored.

• Unfortunately the Final spill value is not always directly proportional to the Flow rate!

• Some components are Proportional and some are not• The resultant Sum of all components is non Linear• The complex mathematical algorithms are described as the “PAC

Algorithms”– Have been patented by P&G

It is these PAC Algorithms which result in the Qi’s accuracy and repeatability at higher flow rates

Flow Rate

Fina

l Spi

ll v

alue Linear effect

K1K2

Final Spill. Summation of all graphs

Non Linear effect

PAC Algorithms Which one to use?• Spill

– Very erratic flows or short feeds ( < 6seconds )

• K1– Materials which have initial downward velocity of zero

• Ie horizontal entry

– Materials which have slow flow rates• Even if vertical entry

– Flow meters, Screw Feeders, Vibratory feeders and Discharge weighing

– When Spill is proportional to Flow The initial downwards

velocity is zero

PAC Algorithms, Which one to use?

K2– Materials which have fast flow rates directed downwards into the

scale– Ie there is a large deceleration force– Hint: spills are small in relation to the flow rate as the

deceleration component is negative and subtracts from the inflight material

– Non linear spill wrt Flow Rate– As Flow Rate increases the amount of material in flight does so

only slightly

Material in suspension

The Algorithms - Summary

• Spill– Very erratic flows or short feeds ( < 6seconds )

• K1– Materials which have initial downward velocity of zero

• Ie horizontal entry

– Materials which have slow flow rates• Even if vertical entry

– Flowmeters

– Loss In Weight Feeds

• K2– Materials which have fast flow rates directed downwards into the

scale

– Ie there is a large deceleration force

– Hint: spills are small in relation to the flow rate as the deceleration component is negative and subtracts from the inflight material

– Non linear spill, sometimes inversely proportional to flow rate

Tips

• Sometimes its not obvious which to use.• Collect data using K1, collect data using K2 and compare results.• Collect data and draw a X, Y graph of FlowQ and Final Spill

– If linear then K1

– If non linear then K2

Review Questions

• Which Algorithm would you use when:– Adding via a flowmeter downwards into a Scale at very high flow

rate?– When you are dumping to empty?– High flow rates downwards into a Scale.