This is Ajay Kumar Kalva, back here after several months and this time i've decided to make few posts in diverse area's which could benefit chemical engineers working in Pharma industry.
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Today, i'll demonstrate about estimating plant OEE, which is most commonly used interview question.
Before going into the topic in detail, lets discuss few basic things.
What is OEE ?
OEE is a Lean manufacturing metric referring to Overall Equipment Effectiveness, which measures the efficiency of plant, equipment or process.
What is difference between Efficiency and Effectiveness?
Effectiveness is the degree upto which something is successful in giving a desired result, whereas the efficiency is ability to accomplish the desired results with least amount of wasted time, money and efforts.
What is availability ?
Availability refers to the net duration for which the equipment is available for manufacturing of product.
How to calculate availability in % ?
% availability is the ratio of time run to the Planned operating time (POT).
Time run (t) = POT - BT or CT or AT,
% Availability = t x 100 / POT
POT - Planned operating time
BT - Breakdown time
CT - Changeover time
AT - Adjustment time
What is Planned operating time ?
Planned operating time is the difference between total operating time (TOT) and Scheduled maintenance time or pre scheduled break (which could be for the operators).
POT = TOT - Pre-Scheduled break or Scheduled maintenance time
What is Performance ?
Performance refers to the speed at which the plant runs as a percentage of its designed speed. We can use the capacity to better represent performance.
How to calculate % performance?
% Performance shall be calculated as the ratio of Quantity produced (Q) to Time run (t) x Capacity (C)/given time.
% Performance = Q x 100 / (C x t)
What is Quality ?
Quality refers to amount of goods parts manufactured (G) to total parts manufactured (Q).
How to estimate % Quality ?
% Quality = G x 100 / Q
Good parts (G) = Total parts manufactured - Waste i.e., reprocess or rework.
Finally, how to estimate Overall Equipment Effectiveness (OEE) ?
OEE is the product of % Availability, % Performance and % Quality.
Hope the things are cleared till now,
Lets dive deep with an example.
Case Study:
A chemical plant with production capacity of 2800 MT/hour was expected to run for 150 hours/week continuously. At the end of the week it produced 250,000 tones together with a waste of 3500 tones. It had 150 minutes breakdowns and 450 minutes changeover and adjustment. We need to estimate the Plant overall effectiveness.
Soln.:
Lets write the data which is given,
Capacity (C) = 2800 MT/hour,
Manufacturing time per week = 150 hours/week = 150 x 60 = 9000 minutes/week,
Quantity produced (Q) = 250000 tones,
Waste = 3500 tones,
Breakdown time (BT) = 150 minutes,
Changeover time (CT) = 450 minutes,
A) Estimation of % Availability,
% Availability = Time run x 100 / POT.
Time run (t) = POT - BT - CT
Planned operating time (POT) = TOT - Pre-Scheduled break or Scheduled maintenance time
Since the process is continuous, Pre-Scheduled break or Scheduled maintenance time = 0,
Therefore, POT = 9000 - 0 = 9000 minutes,
Time run (t) = 9000 - 150 - 450 = 8400 minutes,
% Availability = 8400 x 100 / 9000 = 93.33 %,
B) Estimation of % Performance,
% Performance = Quantity produced x 100 / (Capacity x time run)
= 250000 x 100 / (2800 x (9000-150-450)) = 63.77 %,
C) Estimation of % Quality,
% Quality = G x 100 / Q = (250000 - 3500) x 100 / 250000 = 98.6 %,
Finally, Plant OEE = % Availability x % Performance x % Quality
= 93.33 % x 63.77 % x 98.6 % = 58.68%.
That's it .....!!
Hope the post is clear for everyone, For any queries feel free to reach me at pharmacalc823@gmail.com
Comments are most appreciated ....!!
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Hi! I am Ajay Kumar Kalva, Currently serving as the CEO of this site, a tech geek by passion, and a chemical process engineer by profession, i'm interested in writing articles regarding technology, hacking and pharma technology.
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