Tamilnadu Engineers Forum5th International Conference – November 2014

The Perils of Overdesign

Background

Over design is not apparent

Under design has an implied failure

Design Targets are set Internally by business Externally by authorities

These are minimums engineers must achieve

Targets can be any range of variables Safety Environmental Health Production rates Quality of product Cost & Schedule

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Failure to meet a target

Visible to many – e.g BP Deep Water Horizon – Poor design and inadequate installation management – did not meet requirement

Can have serious impacts – short and long term – workers on platform, fisheries, tourism, local businesses – life, cost, business reputation, business failure

CEO - “I want my life back”

Impact on UK Pension values

Still in legal dispute

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Overdesign

Myths about over design

Nobody notices or visible to few

Its always safer

It does not matter to anyone

We meet our target so no one will care

It will be noticed and there will be a price – in terms of resources including materials manpower and money.

Sustainability is about protecting all resources and using them to our best adavntage

In the long run it does matter

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Oversizing

Causes of oversizing can be many

We don’t know the feed stock when before we build – wells to be drilled in upstream, oil to be purchased for downstream refinery– so we estimate and add margins to cover uncertainty

We don’t know how much we need to produce – what is the market going to be in 1 year, 5 years, 10 years and beyond – so we estimate and add margins to cover uncertainty

We set environmental limits – maximum and minimum temperatures for instance

We then add a “design” margin – typically 10% without actually defining its purpose

Supply chain adds its margins based on the terms and conditions

Impact will be seen when we put the facility to use

Commissioning takes longer as plant is not running at the optimum point

Plant running unstable or inefficiently

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Typical Issues – Centrifugal compressor

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Limited turndown Head is impacted by fluid composition Power requirements impacted by fluid

composition The oversizing results in Loss of efficiency Running closer to unsafe surge

conditions Larger ancillary equipment Increase wear and maintenance on

recycle controls used to control machine

Greater Capex and Opex

Similar applies to Pumps

Typical Issues – Tanks

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Improved Performance! Larger tanks – diameter

increases as height is limited Takes more land More materials in construction

(pipe and cable) due to greater distance

More cost for utilities due to greater demand

Greater risk in the event of fire Increased capex – tank cost is

proportional to volume

Typical Issues

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Pipeline Larger diameter and wall thickness More construction costs – welding,

PWHT, logistics due to weight Deeper trenches – cost and safety

issue In operation stratification / separation

of process fluids Increased settlement of solids Increased corrosion – including

failure

More frequent cleaning / inspection requirements

Greater Capex and Opex

Utility Larger facilities usually require more

utilities Power – transfer of materials, lighting Air Water Control systems Buildings Land

All result in greater Capex and Opex

Typical Issues – Processes

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Distillation Liquid channelling / loss of seal Insufficient vapour Loss of separation efficieny Products don’t meet specification

Cyclonic Separation cyclones / hydrocyclones Insufficient velocity to effect separation Carryover of products into the wrong streams Failure of downstream processes

Getting it right

Requires Planning and Control

Gate systems are used to plan and control Appraise – Concept – inputs / output targets including tolerance must be defined Define Execute Operate

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We must have the right targets and basis before moving to next stage

Conflict of Requirements

Projects have HSE, Quality, Cost and Schedule goals

We cannot always balance all requirements perfectly

Safety standards are fixed

Cost / Schedule changes limited

Quality takes the strain

Oversizing protects quality

Oversizing increases cost

Oversizing can increase time

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Quality

CostSchedule

HSSE

Risk

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The threat associated with uncertainty is often managed by over-sizing to remove the uncertainty.

Risk is defined as being:‘An uncertain event, feature, activity, or situation that can have a positive or a negative effect on your objectives’Risk are opportunities (positive effect) or threats (negative effect)

Risk is the product of the uncertainty of an event occurrence combined with the impact if it happens.

The threat of under-design results in over-design creates an opportunity that we overlook.

Acceptable Risk

Statutory authorities impose their own minimums with legal backup –often driven by society’s opinion

Business has its own targets – determined by stakeholders Standards of risk change over time – e.g. safety There are rarely the same for each project Example - Flood defences

New Orleans – 1 in 100 years failure Netherlands – 1 in 10,000 years

So designing for 1 in 1000 years would be seen as under design in Netherlands but over design in New Orleans.

Same applies to weather conditions – how often are we prepared to accept disruption due to snow, rain or wind

Perception and willingness to bare cost is critical and is this society, business or consumers.

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Risk Management

Typical Mitigation Approaches

Avoid – eliminate completely

Limit – accept not always

Insure – pay to cover loss

Provision for

Cost for

Time for

Manage

PROBABILITY

IMPACTLow High

High DETRIMENT

Avoid orlimit

Treat as cost and thereafter opportunity

Insure, provisionand limit

Provisionandmanage

Using appropriate Risk Management techniques is a tool to measure the effectiveness of design management

Over design generally “Avoids” – other approaches may be more appropriate based on actual risk.

Summary

We do not need to avoid all risks - some may be tolerable to the stakeholders

Tolerable risks should be acknowledged and managed

Every society and business has its own acceptance criteria –learn these before starting work

Challenge waste – think sustainably

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THANK YOU