QUARRY DEWATERING – DIESEL OR ELECTRIC PUMPS?

Above: a diesel dewatering pump in action

How you can make an informed decision?

Often engineers in quarries and mines, or in other industrial settings, are faced with the decision between using a diesel powered pump unit, or an electric one. Of recent times, pressures to increase efficiency and cost savings, and environmental and safety considerations, have led to the two options being looked at more and more seriously. There are a number of points that must be considered when making this decision and it is important to first carefully examine your application and pumping needs. Some of the considerations would include…

The location of your site may limit you to diesel

If electrical supply is insufficient for a large pump or too unreliable in remote areas, then diesel power is the logical conclusion. Also, the usage and location of the pump within your site may favour diesel power as electrical pumps are often less mobile. If say you have a number of locations around the site that need dewatering, it could be impractical to lay electrical cabling all over the site. Having said this, electric submersible pumps should be considered – they are very flexible and if you go for model such as the Audex range, they are perfectly designed for the wear and tear of the mining and quarrying environment.

Electricity supply

For electrical systems the power source can affect their suitability. If a permanent power point is present the only efficiency check need be on the pump, however if your site features a centralised or mobile generator to provide electrical power then the efficiency of the conversion of diesel to electricity almost entirely rules out the possibility.

"...if you ran your pump 24 hours a day for a year by the end you could have saved enough money by using an electric system to buy a Land Rover Discovery XS"

The environmental and safety considerations are vital

The emissions when using a diesel powering method must also be considered as often ventilation is of primary importance to site safety; particularly if the pump is needed underground or in an area which is difficult to ventilate. Also diesel handling on site can lead to spillages and contamination of ground water that can be difficult to solve. This being said electric isn’t the perfect solution either as long high load cabling over a site is also a safety hazard. Again location of power source and power usage is of key interest.

Above: this quarry in Scotland saved £8,000 a year by switching from a diesel pump to an Audex submersible pump suspended on a pontoon.

Maintenance of your pump solution is also something that needs to be carefully examined

Before making a decision you must think carefully about maintenance as on-going upkeep of equipment can be a serious drain on your profits. Using a diesel unit is more efficient than using a generator and a pump but, generally speaking, an electric unit will require considerably less maintenance. The more maintenance required, the more downtime, which can be a big cost factor in a busy site. That being said, electrical maintenance does require specific training so it is important to consider your work forces capabilities along with those of your pump supplier.

Running costs is perhaps the greatest factor to be considered

This is the question which lots of pump engineers are currently focusing on and with good reason. Using electric, the price per litre pumped is far lower than for diesel powered pumps as can be seen in figure 1. Depending on the amount of time in use a huge saving can therefore be made by using electrical systems. To illustrate this if you ran your pump 24 hours a day for a year by the end you could have saved enough money by using an electric system to buy a Land Rover Discovery XS and have enough left over to pay for the luxury hotel in Scotland you will be driving to; and that’s with the added front headlights, heated steering wheel, walnut interior as well as the cooler in the arm rest!!! In other words, a huge saving of £57,465.60 a year [See figure 2].

Finally it is important to note that the potential output (flow rate and performance) and the cost of purchase of either solution is roughly the same. It seems then that the choice between electrical or diesel powered pumps should be mainly based on their location and intended use. If a permanent power point is available electrical power should be used; as long as cabling infrastructure is reasonable because it is more efficient and cheaper to run in the long term. However if the pump needs to be mobile and flexible in use, or if your site is off grid then diesel powered pumps are possibly preferable.

The Bottom line

• Electrical pumps carry huge savings if heavily used in the same location and on-grid power is available.
• Diesel power is usually best for mobile pumping solutions and where electrical power has to be generated on site.

In all cases it is best to consult a dewatering expert who should be able to give you a cost breakdown specific to your site and location.