Skip to main content

Did you buy the wrong type of compressed air dryer?

Do you have a desiccant compressed air dryer in your plant?
Yes?
Do you know the annual running cost of that dryer?
It's plugged into a power socked, so it probably uses a bit of electricity… and you need to replace the desiccant every so many years. Right?
True!
But for many types of desiccant air dryers, there's a hidden cost… and it is substantial!
In fact, the yearly cost will probably SHOCK you!
The culprit?
Purge air!
Purge air is air that is used to regenerate the desiccant. (the desiccant needs to be regenerated every few hours, to remove the water that it previously absorbed).
There are 2 main types of desiccant dryers:
Heated blower regenerated
This type uses an external blower and heater to regenerate the desiccant.

It requires only electricity (around 1 kW for every m3/min of compressed air).

Purge regenerated
This type doesn't use electricity to regenerate the desiccant...
Great, right! 
No! 
It uses precious compressed air!!!
This compressed air flow is between 10 and 20% of nameplate rating of the dryer.
So if we take a 90 kW air compressor (17 m3/min or 600 cfm) that runs for 8.000 hrs per year (almost fulltime, which is quite common). And we pay 10 cents per kWh… what do these two dryers cost us?
Running cost for heated blower generated dryer:
A dryer for 17 m3/min uses around 10 kW of electricity on average. At 8.000 hrs per years and 10 cents per kWh, 
… that's $ 8.000 per year in electricity
WOW!

That's the price you pay for dried air!

But let's take a look at the other type of dryer…
Running cost for purge air regenerated dryer:
Purge air regenerated dryers come in two flavors: heated purge and unheated purge.

Heated purge uses around 10% of compressed air (+ electricity for heating), while unheated purge uses around 20% of compressed air.

So… what does this cost us?
Our 90 kW air compressor, that runs for 8.000 hours at 10 cents per kWh costs us $72.000 to run per year!
(surprised?)
So what does our air dyer cost us? It uses up to 20% of our precious compressed air for the regeneration process!
What? Are you crazy?
20% of compressed air, that's $14.400 per year! 
Wow again! Almost double!
And that's the MINIMUM you'll pay through your desiccant compressed air dryer.
The purge air rating is *nameplate* rating – so if you have a bigger dryer than really needed (which by itself is a good thing actually), you will also use more purge air!
So if you have a 800 cfm dyer behind your 600 cfm air compressor… you will lose 160 cfm of compressed air. That is 1/4th of your precious compressed air!
And if you chose the cheapest option, without dewpoint control or anything like that … it will happily continue drying and purging, even if your compressor is stopped!

Comments

Popular posts from this blog

Decoding the Duty Cycle Rating of Piston Compressors

Selecting the correct air compressor for your application can be a complicated process. Before making a purchase, operators need to specify the quality and amount of air their application requires. Each compressor technology (rotary, piston, centrifugal, etc.) has an optimal flow output, so users should choose compressor technology based on the compressed airflow requirement of their application. Some compressors, like rotary screw and centrifugal, are designed to run continuously at full speed while maintaining peak airflow (defined in cubic feet per minute, or CFM). The motors and cooling systems of these compressors are engineered to run 100 percent of the time without overheating. However, this isn’t true for all compressors. Piston compressors do not have the cooling capabilities to run continuously for extended periods of time. Therefore, each piston compressor must have a specified flow output and pressure, as well as the perc…

A VSD Compressor Doesn’t Save You Money

VSD (Variable Speed / Frequency Drive) Compressors

The energy savings were huge… of course. The pay-back time would be a few months, or days, or less.. for sure!

Stop here!

Yes, a VSD compressor can save huge amounts of energy (and thus money), but only if a propoer homework is one, make some calculations and use your common sense.

[For those in the dark: a VSD or variable-speed compressor uses a frequency drive to match the compressor speed (and thus capacity) to the amount of compressed air needed. This as opposed to 'load-unload' machines that runs at a fixed speed but 'loads' and 'unloads' between a minimum and maximum pressure).

And IF a VSD compressor is a good idea in your situation, buy the right size of VSD compressor.

Here's when a VSD compressor will save you money: when it runs at less than 80% speed for most of the time and when it runs continuously (daily).

In these cases, the cost-savings can be huge. Tens of thousands of dollars per year in energy …
4 Ways to Extend Your Air Compressor’s Life
Intelligent management of maintenance and operations of the plant’s compressed air system helps increase plant uptime, reduce unplanned shutdowns and help keep the plant profits and employee morale at peak levels. Service Agreement for Out-Sourced Compressor Maintenance With a full range of coverage options available, service provider inspects your air compressor for wear, damage and potential failure. Below are three different types of Air Compressor Service Agreements and their key benefits: OEM Service Schedules – Offer compressed air maintenance according to scheduled service intervals. Includes 46-point compressor inspection, filters and fluid.Annual Maintenance Agreement— Sakoon offers annual service agreements to relive plant managers from hassles of air compressor maintenance so that they may focus on production.Trouble Shoot Plan— System Failure – Call the Professionals! Should your system ever fail, customers can contact Sakoon spec…