WELCOME

Maintenance Engineer

If you are the maintenance engineer for a general industrial requirement, then a lot of what is contained here will apply to your equipment also, keep scrolling and reading.

Hopefully the project engineer who specified the drying equipment for your system, specified the simplest, most reliable and efficient Heatless Desiccant Air dryer/s which are producing consistently dry instrument & process air, at least to a -40oC pressure dewpoint (pdp). Particularly if you are based within a hot climate.

If you answered that you are - then congratulations.

But how can you be sure ?

Are you consistently producing "dry" air at -40oc pdp ?

Are your dewpoint meters callibrated and measuring the outlet of each dryer unit  ?

Are the dryers being operated within their design parameters ?

Are the dryers being maintained as per the manufacturers recommendations ?

If not, then keep reading and scrolling down.

MAINTENANCE - preferably Preventative (PM)

I find it amazing that this is still an open topic. Surely we accept and appreciate that we service and maintain our cars for one basic reason - so it doesn't breakdown when we most need it !. 

Most sensible drivers maintain their vehicles in line with the manufacturers recommendations, because they appreciate that the manufacturer knows the peak reliability and performance periods for the parts fitted to their cars. 


Is this not what we are all looking for, reliability and performance. The car will go as fast as the specification, will do so many miles per gallon and be reliable for a given period of time at a measured cost, if maintained.

Why change your engine oil ?

Because it is cheaper to change the oil every year rather than replace the engine, every 3 years.

So why is that we do not accept the same basic principles when applied to equipment that could have a more catastrophic impact.


When you consider the life of most plants and the equipment within the plants doesn't it make more sense to maintain the equipment at the optimum performance and reliability levels.


In the long term and with most plants we are talking long term, it works out cheaper and more cost effective. Increased production, reliability, less downtime, scheduled maintenance.

"FIRE FIGHTING" - in relation to maintenance, is for a variety of reasons, one of the most widely used practices  and basically means fixing something when it breaks.

"Why fix something if it is not broken" - right ? - WRONG.

Preventative Maintenance (PM) isn't about fixing things that are not broken, it is about taking care of equipment so that it does not break unexpectedly. Giving you back control over your equipment, not the other way around.

Which of these gears is the more important ?

Within your plant or refinery (the machine) every gear (equipment) is important. If it wasn't, then it wouldn't be there. So every gear (equipment) needs to turn (operate) efficiently and reliably, to ensure that the plant (the machine) produces a quality product as efficiently, reliably and as safely as possible. Not only does each gear (equipment) affect the efficiency of the plant/refinery (the machine) but it also affects the other gears (equipment) directly or indirectly connected to it. So in the case of "fire fighting", fires will spread if not dealt with quickly and cause damage to the surrounding area (other equipment). This applies to all the equipment within your plant/refinery. So all the gears are important.    Logic

BENEFITS OF PREVENTATIVE MAINTENANCE (PM)

IT IS CHEAPER

Preventative Maintenance is generally 25-50% cheaper than "run to fail" or "fire fighting" maintenance programs. As compared over a 5 year operating period.


  • PM provides a planned maintenance cost, with minor fluctuations which can be budgetted for - NO BIG SURPRISES.

It is cheaper to replace the filter elements every 6-12 months (depending on manufacturer) rather than changing the desiccant early.


The filter elements protect your desiccant and your plant. What's the cost of the items which need repairing/replacing because they have been impacted by desiccant dust ?

LESS HEADACHES

The more reliable your equipment is, the less headaches you will have in trying to deal with unexpected and unplanned problems.


Most dryers, when the recommended maintenance is followed, will give 99.9% reliability over a 12 month period. But only if the correct maintenance is followed.


Imagine what it would be like, if all the equipment within your plant had a guaranteed reliability period and a planned PM program.

IS PROFIT & QUALITY NOT AN ISSUE ?

Reliability and efficiency are directly linked to profit and quality. 


If your equipment isn't reliable, then you will struggle to produce the end product.


But if the equipment is not working efficiently, then the quality of the product will be affected, losing your company position in the market.


Inefficiency increases cost, making your product more expensive to produce.

Learn more

MAJOR COMPONENTS SHOULDN'T NEED REPLACING

The main components on your dryer should be designed to be serviceable for the life period the dryer.


Providing that the minimum maitenance is completed on a regular basis.


One of the main components on a dryer are the valves, which should never need to be replaced as complete assemblies, purely serviced annually.

System Review

The average working life of a refinery or chemical processing plant is between 50 and 120 years, the major components within your system should at least survive the minimum period of 50 years. If not, then you could ultimately be heading towards a future catastrophic outage and subsequent extended plant shutdown for repairs.

The single most important common element within your system is the process and instrument air network, on which almost every process relies upon.

If you have stainless steel pipework throughout, then you have little reason to worry, unless you are in the food or pharmaceutical industries, which generally do have stainless steel pipework, but must be wary of bacteriological growth and contamination.

They generally have dryers producing a -70oC pressure dewpoint (pdp).

So what are we talking about ?                     Put simply - DEWPOINT

DEWPOINT

Simple Definition - the air temperature, at a given pressure, at which water vapour begins to condense into a liquid.

Almost everyone of us, will have at sometime, experienced the effects of dewpoint, be it sitting on the grass early in the morning or simply getting a drink can from a vending machine and placing it on our desk.

The greatest misconception, with regard to dewpoint, is that it is purely the temperature at which moisture begins to condense into a liquid.


It is also the measure of how "dry" the air is, how much moisture remains after being dried to a given dewpoint. As illustrated in the chart below.

Dewpoint oC Grams of water per m3 Dewpoint oC Grams of water per m3
-70 0.0025 0 4.87
-60 0.0119 5 6.8
-50 0.039 10 9.4
-40 0.12 15 12.9
-30 0.33 20 17.4
-20 0.89 25 23.2
-10 2.16 30 30.5

There are three elements needed for corrosion to occur, a ferrous material, oxygen and moisture. At a -35oC pressure dewpoint, there is insufficient remaining moisture for corrosion or bacteriological growth to take place. A -40oC pdp instrument air specification allows for a 5oC safety buffer, preventing corrosion.

Corrosion - the single biggest hidden threat to your plant, costing industry over $2.5 trillion per year.

For "Blue Chip" industries this is a major issue - Why ?

Remember, liquid water is not the most damaging of the contaminants within your compressed air system. Particulates are.

Corrosion generates increasingly more and larger particulate contamination, causing more damage.

Want to learn more - CLICK HERE

Don't forget your plant is expected to operate for a minimum of 50-120 years. Plenty of time for corrosion to have a major impact. Maybe not an issue you will see in your lifetime, but certainly within the lifetime of your children and grandchildren.

Preventative Maintenance

The only safe, reliable and efficient maintenance program.

Most good dryer manufacturers recommend a 12 month maintenance period.

The following are the components which should be serviced and replaced annually.

01

FILTER ELEMENTS

Generally three types, inlet, outlet and control (pilot). Replace annually (some manufacturers every 6 months). Filter elements cannot be cleaned and differential should not be relied upon.

02

MAIN VALVES

The main valves on a dryer should be removed and serviced. Service kits are generally available for all valves. Check for scoring and damage, particularly with ball & butterfly valves.

A good maintenance engineer should be able to fully service a small dryer within a normal working day.

For a medium to large dryer, 2-3 good maintenance engineers should be able to service a dryer within a normal working day.

DESICCANT 

The correct desiccant should last 3-5 years, within the original design conditions of the dryer.

If not, then you have an issue with your dryer, system or desiccant.


Grade - is a word which is incorrectly used when selecting the correct supplier of desiccant. 

Most desiccants are manufacturered to the same ratio of materials (grade).


For dryers, the more important selection criteria is size. This will affect air flow, contact time, and abrasion all important factors when applied to desiccant and the efficiency of your dryer.

LEAKS

It is generally accepted, that within most major plants, 25-30% of the compressed air produced is being lost to leaks. A percentage of this loss can also be attirbuted to bad system management or operating practices. Refer to anecdote No. 5.

There are many effects which can be attributed to this high leakage rate, aside from increased utility cost.

1. Increased loading on the comprerssor, if it unecessarily works harder it runs hotter.

2. The servicing of compressors is usually based on hours run on load, service interval is shortened.

3.  Dewpoint would be affected. Within 40ft of a 1/4" leak, 20o's of dewpoint is lost.


So not only are you wasting energy and the associated expense, the quality of your system is compromised. If your dryers are only producing a -20oC pdp, one 1/4" leak and you could have a 0oC dewpoint. Further leaks and you would probably have a positive dewpoint and the associated "liquid" contamination. Either way corrosion and the speed of particulate generation exponetialy increases the wetter the air gets.

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