03- Process Analysis

8/9/2019 03- Process Analysis

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OPM 1 Term 2, B2014-16, Oct-Dec 2014 Session 03 Process Analysis

Process Analysis

OPERATIONS MANAGEMENT -1

Term 2, B2014-16, Oct-Dec 2014


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West

converts iron ores into iron briquettes to supply steel


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~ 160 m

IronOreFines

CFBPreheater

InclinedBucket Elevator

1st StageCFB Reactor

2nd StageFB Reactor

HBI Produc

ProcessGas

HeatExchanger Process GasCompressor

Fired Gas Heaters

ElectricalSubstation&ControlRoom

Engineering drawing

To Create a Process Flow Chart (Diagram)


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Elements of a Process

Inventory / Buffers

Do NOT have a capacity; however,

there might be a limited number of

flow units that can be put in this

inventory space at any moment of time

Multiple flow unit types possible

Arrows

Indicate the flow of the flow unit

Multiple flow unit types possible

Activities

Carried out by resources

Add value and are required

for completion of the flow unit

May or may not carry inventory Have a capacity (maximum number

of flow units that can flow through

the activity within a unit of time)


5/30OPM 1 Term 2, B2014-16, Oct-Dec 2014 Session 03 Process Analysis

Pre-Heater

Pile of Iron ore fines

Process flow diagram, first step



LockHoppers

1st Reactor 2ndPre-Heater


Process flow diagram, to be continued



FlaHe

DischargeBriquetting

Lock

Hoppers1st Reactor 2nd RPre-Heater


Finished Goods

Completed process flow Process flow di



Completed PFD for the Circored process

Pile of Iron

ore fines

Pre-Heater

Bri

tinFlash

heater

Dis-

charge

Fini

goo

Lock

Hoppers1st

Reactor

2nd

Reactor



FlasHeaDischargeBriquetting

LockHoppers

1st Reactor 2ndRePre-Heater


Finished Goods

7.5% Outflow 15% Outflow 1

FlasHeaBriquetting

LockHoppers

1st 2ndPre-Heater


Finished Goods

Process flow diagram accounting for mass


10/30OPM 1 Term 2, B2014-16, Oct-Dec 2014

Session 03 Process Analysis

Process Concepts

Important

Process capacity

Flow rate

Cycle Time

Manufacturing Lead Time (MLT) /Throughput T Bottleneck

Process utilization and capacity utilization

Workload and implied utilization

Additional

Lot Size/Batch Size

Setup time Run time

Waiting time

Idle time

Buffer


11/30OPM 1 Term 2, B2014-16, Oct-Dec 2014


Bottleneck and process capacity Capacity: Number (amount) of units that can be processed pe

Each briquetting machine has a capacity of 55 tons per hour

Overall capacity of a sequence of processes is determined by

process, i.e. the resource with the smallest capacity.

Process capacity=Min{Capacity of Res 1, ., Capacity of Res

Incorporating available input rate and demand rate,

Throughput=Min{Input rate, Process capacity, Demand rate

Demand

InputBottleneckCapacity

Excesscapacity

Flow Rate

Demand

InputBottleneckCapacity

Excesscapacity

Flow Rate

Demand constrained

Flow Rate Flow Rate

Supply constrained


12/30OPM 1 Term 2, B2014-16, Oct-Dec 2014


Capacity Related Terminology

Setup time : thetime that a part

spends waiting for aresource to be set

up to work on thissame part

Process time/runtime is the timethat the part is

being processed

Queue titime th

waits for while the

is bussometh


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Time Components of Production Cycle (C

Wait time is the time that apart waits not for a resourcebut for another part so that

they can be assembledtogether

Idle time is the unuthat represents thtime less the sum

setup time, processqueue time, and w

i d i f


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Time to Produce a Certain Amount of Su

Assuming the process is already producing output.

How long does it take for the Trininad plant to prod10,000 tons?

A restaurant has 40 tables. Average flow time = 60 m

long is the wait time if you are sixth on the waiting l


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Throughput Time = Work-in-Process /Throughput rate

Operations management (OM) covers a large arena of practice.

Littles Law is discussed in several current OM texts, including Hopp a(2000), Cachon and Terwiesch (2004).

Queuing theory and OM generally use different notations for Littles Law

and so we introduce that issue first. In a desire to get close to people wh

using LL to support decision making,

Littles Law

Average Inventory = Average Flow Rate X Average Flow Tim

( Cachon and Terweiesch

( Hopp amd Spearman, 2000

Li l L


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Littles Law

7:00 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00

Cumulative In-flow and Out-flow

11

10

98

7

6

5

4

3

2

1

0

Flow Time

Inventory

Inventory=Cumulative Inflow Cumulative Outflow

Cumulative

Inflow

Cumulative

Outflow

Patients


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The process capacity of Circored plant in Trini

Capacities

Preheater 120 tons/hour

Lock Hoppers 110 tons/hour

1st (cfb) Reactor 112 tons/hour. Processes 28 tons every 15 minutes

2nd (fb) Reactor 100 tons/hour. Processes 400 tons every 4 hours

Flash heater 135 tons/hour

Discharge 118 tons/hour

Briquetting 165 tons/hour

Pre-

Heater DischaFlash

heater

Lock

Hoppers 1st (cfb) Reactor

2nd (fb)

Reactor

Process Capac

= min{120,110,112,100,

= 100 tons/ho


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The cycle time of circored plant in Trinidad

Cycle time: Amount of time taken to process 1 unit in a repetitive

Since different units can be processed in parallel, cycle time is not the flow tim

Cycle time (designed) = 1 / Process Capacity

How long does it take to process 1 ton of iron ore?

Since 1 hour is required for 100 tons, 1/100 hour suffices for 1 ton.

That is, the cycle time is 0.01 hour = 0.6 min = 36 seconds

Every 36 seconds 1 ton of iron briquette is completed.

Pre-

Heater DischaFlash

heater

Lock

Hoppers 1st (cfb) Reactor

2nd (fb)

Reactor

P tili ti d C it tili ti


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Process utilization and Capacity utilizatio

The objective of most businesses is to increase profi

increase utilization.

A service process should not pursue 100% utilization

Utili ation of limited demand


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Utilization of limited demand Assume the demand is only 657,000 tons

Design capacity = (100 tons/hr X 24 hours/day X 365 days/ yr)

tons

The bottleneck is the resource with the highest utilization.

Utilization Profile


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Preheater LockHoppers

CFB StationaryReactor

Flashheater

Pressurelet-downsystem

Briquma

Imbalance relativeTo bottleneck

Mismatch between demand andsupply at the process level


CFB StationaryReactor

Flashheater

Pressurelet-downsystem

Briquma

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Imbalance relativeTo bottleneck

Mismatch between demand andsupply at the process level

Bottleneck

Utilization

Utilization Profile



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Utilization only carries information about excess ca

Implied utilization captures the mismatch when the

exceeds the capacity.

The utilization with demand of 1 095 000


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The utilization with demand of 1,095,000

Bottleneck

Implied (requested) Utilization of a resource = Demand / Capacity


CFB FB FlashHeater

Briquett0%

50%

75%

100%

Utilization

Discharge

125%

STEPS FOR BASIC PROCESS ANALYSIS WITH ON


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STEPS FOR BASIC PROCESS ANALYSIS WITH ON

OF FLOW UNIT

Find the capacity of everyresource, if there are

multiple resourcesperforming the same

activity add their capacitiestogether.

The resource with thelowest capacity is called the

bottleneck. Its capacitydetermines the capacity ofthe entire process (Process

Capacity).

The flow on Flow(Availab

Pro

We find the Utilization oSimilarly we find the utilization of eachresource as Flow rate

Different units flowing in the same syste


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File

Contact faculty/

other persons

Contact prior

employers

Benchmark

grades

Confirmation

letter

Internship

Staff

Consulting

File

Contact faculty/

other persons

Contact prior

employers

Benchmark

grades

Confirmation

letter

Different units flowing in the same syste Outsourcing business processes is common

Billing, Recruiting, Maintenance, Customer call centers, etc

The company which handles the outsourced process is likely to deal w

kinds of units

Case in point: A company that provides resume validation service:

Demand is 180 applications per day ( 30 for consulting, 110 for staff and remaining f

STEPS FOR BASIC PROCESS ANALYSIS WITH M


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STEPS FOR BASIC PROCESS ANALYSIS WITH M

TYPES OF FLOW UNITS1. For each resource, compute the number of minutes that the resource can produce; this is 6

Number of resources within the resource pool.

2. Create a process flow diagram, indicating how the flow units go through the process; use m

indicate the flow of the different flow units.

3. Create a table indicating how much workload each flow unit is consuming at each resource

The rows of the table correspond to the resources in the process.

The columns of the table correspond to the different types of flow units.

Each cell of the table should contain one of the following:

1. If flow unit does not visit the corresponding resource, ;

2. Otherwise, demand per hour of the corresponding flow unit activity time.4. Add up the workload of each resource across all flow units.

5. Compute the implied utilization of each resource as

Implied utilization = Result of Step 3

Result of Step 1

The resource with the highest implied utilization is the bottleneck.

An application as a unit


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Activity

Time (min)

Per applct

Number

of workers

Available

Capacity

Applct/hr

Consulting

Workload

Per hour

Staff

Workload

Per hour

Intern

Workload

Per hour

T

File 3 1 20 3 11 4

Contact Persons 20 2 6 3 0 0

Contact

Employers

15 3 12 3 11 0

Benchmark

Grades

8 2 15 0 0 4

Confirmation

Letter

2 1 30 3 11 4

Demand per hour for validation: 3 for consulting; 11 for staff; 4 for inter

Using One minute of work as the flow unit to find the


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g

Activity

Time (min)

Per applct

Number

of workers

Available

Capacity

Consulting

Workload

Minutes Per

hour

Staff

Workload

Minutes Per

hour

Intern

Workload

Minutes Per

hour

File 3 1 60 3 X 3 11 X 3 4 X 3

Contact Persons 20 2 120 3 X 20 0 0

Contact

Employers

15 3 180 3 X 15 11 X15 0

Benchmark

Grades

8 2 120 0 0 4 X 8

Confirmation

Letter

2 1 60 3 X 2 11 4 X 2

Demand per hour for validation: 3 for consulting; 11 for staff; 4 for inter

A li ti it


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What is the minimum number of people to hire simplied utilization of contact employers is below 100%

What happens to implied utilizations when staff ap

decrease to 8 per hour? Compute the new utilization

Summary of process analysis


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Compute the

Capacity for

each of the

Resources

Use demand to

compute the

implied utilization

levels

Identify the

Bottleneck

Prepare a

Process Flow

Diagram

Use different

Colors to mark

Flow units

Note that capacity

levels may differ

depending on

product type

Compute the work-

load across all

product types

Step with highest

implied utilizationExtensions required

for working with

multiple flow units

Extensions required

for working with

multiple flow units

Compute the

Capacity for

each of the

Resources

Use demand to

compute the

implied utilization

levels

Identify the

Bottleneck

Prepare a

Process Flow

Diagram

Compute the

Capacity for

each of the

Resources

Use demand to

compute the

implied utilization

levels

Identify the

Bottleneck

Prepare a

Process Flow

Diagram

Use different

Colors to mark

Flow units

Note that capacity

levels may differ

depending on

product type

Compute the work-

load across all

product types

Step with highest

implied utilization

Summary of process analysis

World class enterprises excel at the speedy and flexible integthe business processes.

Finding the bottleneck allows us to compute a variety of perf

measures.

You Can't Manage What You Don't Measure

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03- Process Analysis