World Cement - July 2020

planning and initial construction stages, rather than

retrofitting the system later. The added engineering

cost of PtD is often less than an additional 10% of

engineering but has enormous benefits in improved

safety and increased productivity.

The cost of PtD initiatives after initial construction

can be three to five times as much as when

the improvement is incorporated in the design

stage. Retroactive improvements can cost far

more, and are sometimes impossible due to

designed-in restrictions or space limitations. This

cost of retroactive improvements is reduced by

implementing modular designs with plenty of

space to work and expand. The biggest cause

of expensive retroactive improvements is cutting

corners initially by seeking lowest-bid contracts.

Low-bid process and life cycle cost

Although the policy is generally not explicitly stated

by companies, the low-bid process is usually

an implied rule that is baked into a company’s

culture. It encourages bidders to follow a belt

conveyor design methodology that is based on

getting the maximum load on the conveyor belt

and the minimum compliance with regulations

using the lowest price materials, components and

manufacturing processes available.

Maximising the volume of cargo and minimising

the price of the system usually means choosing

the narrowest feasible belt operating at the highest

speed possible. This leaves little margin for error

and in many cases results in chute plugging,

excessive spillage and reduced equipment life.

According to conveyor expert and P.E.,

Todd Swinderman, “When companies buy on

price, the benefits are often short-lived, and costs

increase over time, eventually resulting in losses.

In contrast, when purchases are made based on

lowest long-term cost (life-cycle cost), benefits

usually continue to accrue and costs are lower,

resulting in a net saving over time.”

The art: Design hierarchy

To safely maximise production, designers and

engineers are urged to approach the project with

a specific set of priorities. Rather than meeting

minimum compliance standards, the conveyor

system should exceed all code, safety and

regulatory requirements using global best practices.

By designing the system to minimise risk and the

escape and accumulation of fugitive material, the

workplace is made safer and the equipment is

easier to maintain.

Life cycle costing should play into all component

decisions. Be aware of specifications on project

components that state ‘specific manufacturer

name/or equal.’ Vaguely written ‘or equal’

specifications are there for competitive reasons

and allow contractors to purchase on price

without adequate consideration for construction

or performance. Rather, buying on ‘life cycle cost’

or ‘engineer-approved or equal’ and anticipating

the future use of problem-solving components in

the basic configuration of the conveyor provides

improved safety and access, without increasing

the structural steel requirements or significantly

increasing the overall price. It also raises the

possibility for easier system upgrades in the future.

The ability to accommodate future increases in

capacity can be included in the original design,

expanding options and reducing future modification

costs.

Best practices

Using the hierarchy of controls along with the

design hierarchy, engineers will be able to construct

an ‘evolved basic conveyor’ that meets the needs of

modern production and safety demands. There are

several key points that should be considered when

designing a safe and efficient conveyor system.

Components of an Evolved

Basic Conveyor

facilitate operations, maintenance and safety.

Raw bulk material drops onto a moving

conveyor belt, creating dust and spillage.

World Cement

July 2020