D US T A N D I TS I MP A C T O NELE CTR ONICS

A B S T R A C T

Indicator and preventive maintenance utility for dust deposited on electronic/electrical devices andIndustrial devices e.g. Computers.

Dust can be conductive or attract moisture causing leakage problems; can insulate the devicescausing it to overheat, can cause poor contact in various circuits or can cause arcing and carbontracking in higher voltage applications and still many more consequences of dust accumulation overelectronics card are there.

Dusting remains very vital part of preventive maintenance for any kind of digital systemsdeployed over varied range and various types of industries. But the question is when toshutdown the system and start blowing the dust with blower

This paper focuses on one such simple method to indicate the degree of dust deposition andthe requirement for blowing away the dust

I N T R O D U C T I O N

Atmospheric Dust is one of the oldest known enemies of electronics and electrical devices. Overperiod of time, gradually, dust gets accumulated on the circuits despite the coveredcovering/packing.

On contrary, when dealing with electronics and electrical devices there is need to keep the devicescool, for which there will be perforations or grill kind of thing engraved on the devicecovering/canopy. These perforations and grills on the covering body give an easy access to the dustparticle to settle on the circuits leading to unexpected consequences.

So, in actual there is no way or very less ways to say no to dust deposition. Good housekeeping isvery essential in ensuring the proper functioning of electronic/electrical device. e.g. PC. Thus toensure good product life of such electronic devices the user needs to carry on “PreventiveMaintenance” on regular basis. One very essential and initial activity forming the basics ofPreventive maintenance is ‘blowing the dust with vacuum cleaner or small sized air blower’.

We do blowing in our personal computers. In industries the blowing activity is carried on lot ofelectrical panels, control system, and all the computers hosting plant specific control, measurementand analysis software’s, during their unit outage or scheduled unit shut down for maintenance.

At home the blowing may not be of much significance but in industries like thermal utilities, cementindustries or oil and gas utilities etc... There will be lot of coal dust, limestone dust and oil and gasfumes etc… so the need for dust blowing activities are indispensable.

One interesting fact is that the ‘rate of dust deposition is not in accordance with your preventivemaintenance schedule or your unit outage plan’.

Now, question which seems obvious at this part of discussion how to decide the start of shutdownthe specific small part or component for dusting/blowing in order to ensure the availability of thebigger system.

Another question is how to get an assessment of the degree of dust deposition/accumulation orscaling.

E X I S T I N G T E C H N I Q U E S

• Covering the electronics card, e.g.… plastic cover on ram.

• Intuition/experience of the maintenance people, blowing or vacuum cleaning during annualoutages/overhaul idea about actual need of it.

• sense of unusual high temperature of the cabinet or systems etc…

T H E M E T H O D T O A C C E S S T H E D E G R E E O FD U S T O N E L E C T R O N I C C A R D S

The method involves the assessment of dust deposition on any circuit/card of any particular sizebased on comparison with another reference i.e. prototype of same dimension as of the originalcircuit/card which acts as reference.

Now this prototype is deployed in the same environment i.e. covering/case/canopy where theoriginal circuit/card lies.

Assuming the fact that there will be very little variation on quantity of dust deposition on both(original electronic card/PCB and the reference prototype) of the devices being exposed to sameenvironment, thus if you can measure the level of dust deposition on the reference prototype, youcan have an idea of how much dust is there on the original device under test.

How to measure the dust accumulation on reference prototype is explained in the following fivesteps in the illustration shown below:

Now let’s try to create dust accumulation indicator for this PCB in the CPU shown in the figurebelow:

Step 1 Identify the dimensions of the Card/PCB/Module under test so that we can makereference prototype with same dimensions for measurement.

Step 2 Turn the two opposite Edges to touch each other such that it forms cylindrical structure.Cylindrical structure has the advantage of consuming less space.

Step 3 Reference Electrical signal measurement, take an imperforated tube of same dimension asthe perforated tube for determining the maximum values of the electrical signal received at theother end of the tube.

Step 4 Creating perforations on the cylindrical tube Size of perforation will be in proportion tothe Dust particulate size that will further depend upon environment of the Industry type in whichcard/PCB is exposed. If the environment is thermal utility then most of the dust will be coal dust andperforations dimensions can match the size of coal dust. If the environment is cement plant thenperforations dimension can match that of cement limestone dust an so on.

Step 5 Final step “measurement”, just turn ON the Light source, and observe the strength of themeasured electrical signal in the meter. The electrical signal will Increase/grow with due course ofthe time as the dust accumulates and blocks the pores.

Since the reference electrical signal is already known from STEP 3 any further rise or fall in thevalue of measured electrical signal will be an assessment of dust level.

Now place this whole assembly into the same environment where the actual electroniccard/module or circuit is placed.

Note: In order to ensure that the amount dust deposited on the cylindrical tube

1. Remains uniform over the cylindrical surface and

2. Very close to the amount of dust deposited on actual module/card

This whole cylindrical device can be move around the central axis (along the lenght) with the helpof small motor.

Finally with due course of time, when gradually dust will be built up on the modules/cardsyour dust monitoring kit will assess it and give you an estimation of degree of dustdeposition.

R E S U L T S / B E N E F I T S

The results or benefits emerging are many such as enhanced overall product life very lessunexpected failures fewer accidents due to overheating of the appliances improvedperformance of the overall device, less trips and alarms, proper contacts is ensured for longerperiod time in relay, switches and connectors etc…

The output of this dust measurement transducer as discussed above can also be used as triggerpoint for any further action or alarm.

A S S U M P T I O N S

1. Dust distribution is uniform in closed enclosure/container/housing in whichPCB/card/module is mounted. Thus if two objects of same surface area are exposed todust/vermin the dust accumulating on both the objects are same and since the wholecylindrical assembly is rotating, dust distribution can be considered to be depositeduniformly.

2. The method described gives the dust indication with comparison from reference ratherany absolute scale.

3. The maximum the number of pores/holes/perforations on the cylindrical surface, the moreaccurate is the dust level indication. The total surface area occupied bypores/holes/perforations cannot be exactly same as the surface area of thePCB/Card/Module.

4. How much exact amount of dust can cause problem is still unknown, the method onlydescribes reliable way to indicate the degree, ‘HI-Lo’ levels, of dust approximately.

C O N C L U S I O N

The method surely describes measurement technique to assess the degree of dust deposition onparticular module or card.

Though the method only describes about HI and Low levels of dust but believe that this paperopens gateway of further possibilities of an absolute measurement and more quantitativemeasurement of dust deposition. Also there is need to accurately predict the consequences ofdust

A U T H O R S N O T E

Some of the images used in the paper are taken from Google image search.

You can share your views, feedbacks or suggestion on my mail id: ‘atulkumar.mshra@hotmail.com’or ‘aaatul007@gmail.com’ or contact me on +91-8826006907.

Thanks.

Atul Kumar Mishra