Static Charge Removal

its a bother issue, especially in winter.

we put a humidifier in our workshop, and workers wear anti static clothes and conduct ring on their wrist.( I dont know what it call in english)

workbench is led to ground excellently etc.

parts are in good shield place. especilly mos devices etc.

pay attation to solding.

I do not know much about plastics, but static issues sound similar to what we had to deal with a solvent room in a printing plant. As CNPower suggests, ground everything.

In addition to the humidifiers and de-ionizer bars, every piece of equipment, furniture, tools, chairs, and people should be electrically attached to a low ohm ground. Lots of ground rods and ground straps, bars, and wires to safely dissipate the static charges. The copper cost might seem high, but this is the only way I know of to safely dissipate the static.

The other course is any steps to prevent static, but if you have to move the material, it is bound to occur.

I agree with cnpower. Humidity control and localized static control of workstations and personnel are highly critical.

The company I work for makes a quite large ion generator which uses an electric blower to distribute the ions over a very wide space. For reference, the unit's size is a little smaller than a cubic meter/yard. Most often these are suspended from a facility's ceiling and used to control airborne dust, particulates, etc. However it might also work for your application. If you might be interested, let me know and I'll send you some literature.

And just because I don't wish to seem like I'm a salesman trying to sell only our own product, I'm sure a web search will reveal other similar devices. Possiby even some that are better than our own! I highly recommend you shop around and find one which best suits your needs.

You can get my ex-wife to stand anywhere near the items. Energy and wallets will fly over to her and effectively cancel everything to absolute zero.

I never thought of blowing ions on her in court. Next time . . . . .

From your description of the product and such, there is no way to have a plant wide solution with a single device.

Every time your plastic part or plastic film is moved relative to another plastic part there will be static developed and until that static is "treated" it will stay on your parts as surface charge.

Even peeling plastic "sticky tape" from a roll creates huge surface static.

The only solution (and this might not be feasible) is to have a material change to something that is surface dissipative, like the film used for electronics devices.

Static control relies on a system. Even in our electronics facility with dissipative flooring, humidity control, earthed benches and so on, I demonstrate to new employees how it is possible to create charge (while not wearing my personal grounding heel strap and wrist bands) just by moving my shirt inside my jacket. (To show them that even with all those controls in place, if the system is not complete then the parts can be compromised.)

Do you have any computer monitors or screens in your site? Check the static on them every time they are turned on.

Static and surface charge are real challenges.

This is interesting static generally comes from rubbing or moving a non-conductor over another surface. with plastics you are making a condenser and so can build up a charge. If the second surface conducts & earthed then the charge is dissipated, Having a piece of chain trailing from the back of a car is an example of one way tried by some people. High humidity also can be effective, in South Africa the problem is worse in the Transvaal than at the coast where the humidity is high. In my industry (synthetic resins) all reactors, blenders, pipelines and tanks have to be earthed.

If you are extruding, try a bar made like a brush but using thin conductive wire to make contact with the surface and ground it. These will need to be put in strategic places generally where the plastic leaves another surface

Interesting but if the polymer is going to be printed, then it will usually be subjected to a "sparking" a high voltage static discharge to make the surface printable.

I am already using ionizer/ static bar and humidifier on different places. but i require something different as stated in #2.

You gave the impression you were blowing deionised air - you need direct earthing. Workers at end need earthing rods to earth charge - same as is done in plants making Formica type products - earthing brush is a metal bar wired to earth with a metal brush (aluminium or copper bristles) or with something like a copper pan scrub on the end

Technically you do not want a straight ground to earth because this would cause a discharge not prevent it. In this particular case its not a big issue because there is not a chance of damaging sensitive electronic components, but it doesn't help in understanding how to remove the static charge in general.

The wrist and heel straps one would wear that are connected to anti-static mats have a 10Mohm resistance between the person and ground. This is to slow the rate of discharge (RC time constant) in order to minimize damage.

There is not a 1 piece of equipment solve all solution to this issue. To have prevented this issue it would have needed to be addressed at time of construction and in the ordering of the process equipment. Approx. 70% of the static issue is addressed when pouring the concrete slab.

After the fact, it becomes a minimizing the damage function. There are coatings you can apply onto the concrete along with floor tilings for absorbing (slowing) the discharge, but they won't be as effective. On the equipment side, you can purchase and machine plastics like delrin that are impregnated with carbon that replace the existing components and can create the same slow rate of discharge needed to properly dissipate the charges as the polymer sheets rubs over the surfaces.

Overall, there is no cheap and easy solution after the fact. In the end, you as a company have to decide what you are willing to tolerate considering the product you are producing and the annoyances this issue creates.

Rubbish

If you don't earth it and get rid of it you will have problems!

Only the first paragraph is wrong, the rest of his suggestions do have merit.

The purpose of grounding everything is not to dissipate static, it is to try to get everything to an equal electrical potential so static does not exist or to minimize the buildup of high static charges. If everything is at an equal potential and electrically well connected, any static that tries to build up is immediately conducted away before it can become highly charged.

The purpose of grounding is to prevent any static charge at all.

PERIOD!!!

j.

This makes complete sense - also years of experience and problems have taught me iof the dangers- those who voted as "off topic" are positively dangerous and need to study some basic physics.

have you checked with resin supplier about the anti-stat used in the add-pak for your material? If you are not constrained by specification, you may want to look at a new additive to improve anti-stat properties.

Add a copper ground- grid with all equipment tied to it. I work in a plastics plant and this has greatly reduced the accumulated static

Hi,

who knows about positive and/or negative charge being built up by friction, by creating new surfaces or by whatever action?

The ion generators working with high negative voltage (no more than -4.5KV to prevent ozone generation, no less because inefficient) will charge the air molecules to a positive charge?

But if the surface to be neutralised is positive?

Natural electric field is positive? at 400V/m. This is generated by thunderstorms. Ice and rain drops are rubbing and hit each other may be enhanced by friction with high-speed air. Negative charge is accumulated in low altitude clouds (3 to 4 Km) then discharged by lightnings. Positive charge is accumulated in high altitude clouds
(12 Km) and only rarely earthed by very high energy lightnings. So Positive charge is remaining, charging the stratosphere to earth (200 F capacitor). Any expert to confirm this or the contrary?

Any droplet that is sprayed from a charged nozzle will be charged opposite to the nozzle. This can build up high charge on walls with subsequent lightnings. This did explode minimum 3 empty oil tankers that were cleaned with high power water spray. The discharge did ignite the oil-air-mist. I am convinced that the TWA800 plane blew up by the same mechanism: air in partially filled fuel tanks subject to droplets from connecting pipes did generate charge to ignite the whole mix and blew the tanks and the plane.

Back to the original problem:

shall we dissipate surface charge by surface resistivity? This is independent of polarity. Or shall we remove surface charge by ion-blowers, then we should know which polarity is existing! How to know? Any continuous no-contacting measurement existing?

RHABE

Diris,

You are being told here by numerous responders what it is clear you do not want to hear, i.e., that there is no one way to prevent static buildup and to control it.

For safety reasons, therefore, your company will have to spend whatever it must to control this very serious problem that some here have pointed out can and will lead to major explosions.

As a printer I was on occasion faced with static problems. The ionizer bars were always a critical element on the printing presses especially on the delivery pile when we were printing on plastic sheet.

I would suggest as to your cutting process the application of those bars to that machine.

I would suggest also, that when you move quantities of materials, you have long, well grounded wires, that you can clip to the conveying vehicle as you move it through and out of the critical plant areas.

Nonetheless, the consensus here (I note we rarely see clear consensus), is that there is no one method of controlling the plant wide problem and the consensus is right. I gather that part of your process involves flammable liquids and you are right to be concerned about the process.

I would extend control methods to incorporate all those suggestions here that are not already in use. Better safe than sorry; if you survive. Cost be damned.

j.

Gentlemen,

I would not so quickly dispute the comments made in post #12. What I understand he is saying is that if all points are "directly" connected to earth, then any static will conduct to ground. My experience is that will often happen as a spark from the charged object to the grounded equipment.

The post is suggesting that the connections to ground be "dissipative". That is, that they provide a path to ground that enables static to be conducted to ground, but for the energy to be spread over sufficient time that there is no spark (Or in reality an extremely low energy spark) at the point when conduction starts.

The OP commented about explosive gasses involved somewhere in the process and there is NO WAY that I would want static sparks in that situation.

For people involved in static prevention in electronics manufacture, there is a well defined system for static protection using dissipation rather than short circuit conduction. Both systems rely on grounding the potential so the energy can be removed. Sounds like semantics, because it is. They are similar but different and the outcome can be dangerous if not properly understood.

Static is a charge developing above ground. If everything is grounded and further there is high moisture and ionization, there is nothing to conduct, or bleed, or slowly convey to ground. Everything is already at ground potential.

j.

Thanks for all participants. Now I have clear idea about staic charge and its removal methods and I concluded that there no any single way that could eliminate the static charge from the whole process/area.

I have used following methods on different areas i;e

*I have used Humidifier in storage area.

*Used Ionizer/ bar at moulding machine outlet.

*I have earthed/grounded all machuines properly.

Although I have not used static mats on working benches. Our workers are not using wrist straps. I think, problem can be minimized by using static floor mats, wrist straps and aprons.

Diris

In addition, all those on shop floor must use Conductive shoes . www.kineticpolymers.com