Compressed air solutions for water transmission

In this blog we’ll briefly explain how air compressors play a role in water transmission and why Atlas Copco oil-free air-cooled compressors are ideally suited for this use case.

Water transmission and the water hammer effect

Transporting water is a hallmark of civilization. We forget how much water flows around us and beneath us along pipelines. If we were to calculate all the water that flows through our own homes, it would add up to quite a significant amount of water mass. And when all this water is moving through the pipes it has a high momentum.

If we were to suddenly block the path of the water along the pipes, by shutting a valve for example, all that momentum would have nowhere to go. And since water isn’t compressible the full force of the moving mass of water slams into the blocked end. A good analogy would be a freight train crashing into a wall.

That sudden change in momentum creates a sudden spike in pressure that travels as a shockwave through the pipe. This shockwave has been given the name ‘Water Hammer’ because it often causes a loud banging or rattling sound along the pipes. For large diameter pipelines carrying massive amounts of water over hundreds of kilometers this pressure spike and shockwave can cause major damage.

Free Ebook: High pressure compressed air applications and solutions

Air compressor solutions for pressure spikes during water transmission

high-pressure-compressor-for-water-transmission

Water transmissions systems (surge water vessels) need to be protected against water hammer. One way this is done is by installing a surge water vessel along the piping system. Surge water vessels are designed to store water while providing a compressed air cushion that absorbs or dampens the pressure spike. Compressed air pressure in the tank will vary as the volume of water rises and falls, based on system demand. An air compressor is attached to the tank to maintain pressure. The air compressor interacts with a liquid-level switch with a time delay relay, and a pressure switch. These features may be together inside a cover mounted on top of the tank or installed separately. The liquid-level switch senses the water level through an electrode suspended inside the tank. The pressure switch senses the air pressure in the tank. Both sensors are set to maintain the desired water level inside the pressure tank by controlling when the air compressor runs. As air dissolves into the water, the water level inside the tank rises and air pressure falls. The compressor begins to pump air into the tank when the water level rises above the electrode and the air pressure falls below the pressure switch setting. A time delay circuit in the liquid-level switch prevents rapid cycling of the air compressor due to waves in the tank.

Oil-free air-cooled compressors are ideal for surge water vessels

Since compressed air is in direct contact with the water, compressed air quality in terms of oil & dust content is very dangerous for the surge water application, and any contamination or oil carry over can impact the water quality,

Oil-free air is a must for such sensitive application where the air is in contact with the final product which is potable water, however some installations use oil injected compressors along with filtration, which can maintain the compressed air quality to a certain extend, but in hot environments like Middle East the oil carry overs in the compressed air during summer are 5 times more the normal carry overs that any filtration system can stand with, accordingly oil free compressors certified with Class 0 according to ISO 8573-1 is the best solution to have risk free oil free compressed air supply to the surge water vessels .

Surge Vessels Applications calls normally for higher pressures between 12 – 20 bar, oil free compressors to produce this pressure are typically either oil free screw compressors accompanied with oil free piston boosters, or oil free piston compressors.

Since surge vessel air compressors runs on intermittent basis based on the water level , the compressor requires to be designed to handle long standstill periods with all the required protection against condensation and rust, in addition for some application compressors need to be mobile and installed in different locations remotely, accordingly air compressors shall be air cooled for the ease of installation and relocation and ease of maintenance .

The Atlas Copco ZP compressor is both oil-free and air-cooled while also being allow designed for immediate ‘plug and play’ installation.

The ZP uses air cooled technology and IE3 TEFC motors suitable for a 50°C ambient environment. This technology makes accessories such as cooling water towers, cooling water pumps redundant, resulting in lower costs and less space. Atlas Copco has also integrated sensors to optimize the availability of the machine, leading to increase reliability and lower maintenance costs.

The ZP high pressure air compressor is ISO 50001 certified for energy efficiency management. And it comes with our patented variable speed drive technology called VSD+.

Over 80% of a compressor’s life cycle cost is taken up by the energy it consumes. Moreover, the generation of compressed air can account for more than 40% of a plant’s total electricity bill. To cut your energy costs, Atlas Copco pioneered Variable Speed Drive (VSD) technology in the compressed air industry.

Atlas Copco's VSD technology closely follows the air demand by automatically adjusting the motor speed. This results in energy savings of up to 35%. The Life Cycle Cost of a compressor can be cut by an average of 22%. In addition, lowered system pressure with VSD minimizes energy use across your production dramatically. Learn more about VSD+ here.

We strongly advise you to select a compressor like the ZP that runs oil-free, air-cooled and delivers high pressure, while also earning significant cost savings for you in the process.

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