Electrical Design For Food Processing Facilities 1

[birddogger]

I'm a consulting electrical engineer designing my first food processing facility, with limited resources/old projects to refer to in my design.

I am familiar with the types of light fixtures required for these designs, and have already talked with several vendors regarding what should be spec'ed, but I have a few more general design questions if anyone can help me:

For the processing areas where hosedown will be occuring, I assume WP receptacles and light switches will be required here, or is there something even more specialized for this application? Or are general purpose receptacles generally avoided in these areas?

I didn't see anything in the Hubbell or Leviton catalogs specific to food & beverage applications, though both offer devices made for wet industrial locations.

On one of the old projects I have for reference, the previous EE ran cable tray everywhere in the processing areas. This does not make sense to me. If you are required to specify light fixtures with smooth surfaces to alleviate dust accumulation/dispersion, how can you justify running cable tray through there, with its large surface area and open construction? Plus, cables do "twitch" on inrush, so I would think that the potential for falling dust would be high.

I will not be placing any lighting/power panels in any processing areas, but as far as items like disconnects, control panel enclosures, etc. - I assume these need to be suitable for wet locations as well. Is NEMA 4X the standard for all devices/enclosures/equip. in these areas?

In general, anything else I should know about elec. design for food processing areas?

Thanks in advance.

 

[jraef]

I can't answer to everything, but I will share some of my experiences.

WP receptacles and switches are not suitable for hose-down areas. There are specific water proof receptacles and cord caps available from Woodhead

http://www.woodhead.com/products/electrical/wiringdevices/

and others, but generally you should avoid having regular outlets for portable equipment whenever possible in hose-down areas. Usually we specified pin and sleave type connection systems because it prevents someone from inadvertantly leaving a drop light or power drill plugged in without having the proper mating seal system.

Light bulbs and tubes must be shatter proof. This website ofers links to regulations regarding that issue, a good resource.

http://www.shattershield.com/index.html

NEMA 4 is less expensive than NEMA 4X when it comes to disconnects etc., the difference is in the concept of "corrosion resistance". N4 is hose-down resistant, but N4X adds corrosion resistance, and then you need to be concerned for the corrosive element. For instance, some cleaning solutions and salt will attack aluminum, but aluminum is often sold as N4X. Most disconnects etc. will use stainless steel for N4X which can drive the cost up substantially if not necessary. Thermoplastics and Fiberglass are also N4X, but some food environments are not compatible with some plastics as well. If it is only water being used, N4 is usually OK.

I for one have never seen open cable tray used in a food handling area. Usually any cables are routed behind the walls and ceiling, with sanitary seals at the penetrations. There is NEMA 4 (and 4X) sealed wireway available from the likes of Hoffman and others if you must route cables through a clean area, but you are right about the dust issue.

"Venditori de oleum-vipera non vigere excordis populi"

 

[Mike2468]

Also, mercury contactors are not supposed to be used. Use mechanical contactors or solid state contactors.

 

[BJC]

Birddogger
I allways got a lot of info from the owner.
I am not sure which agency ( if any sets) the rules for electrical installation. I have worked on process plants that had stainless steel conduit that was welded together. That was to the motors. Controls were plastic tubing that was routed in quick disconnect stainless pipe. They repalced the tubing after cleaning.
The whole place was built to take steam cleaning not just was down. They did not want any pleace where particals could hide- like in conduit threads. The control panels were nema 4X, stainless and cost a small fortune.
We did it their way, they were paying the bill. That was a cheese plant.
I've done cannerys that were the owner not all that fussy. The equipment was steamed but the general area was just hosed down with hot water.
I would start researching with the Dept of Agriculture.

 

[advidana]

Check with your local health department and the state health department for regulations for this installation. Light fixtures should be rated for food handling and vapor tight if within hose down area. nema4 or nema 4 is ok. Don't ever ever ever use "GO BY" drawings or specs unless you know they are correct or you can question the guy that did them because there is a lot of bad drawing floating around. Also check with you local building department for thier views on this type of installation. yea I am tuff.

 

[busbar]

 
Suggested for cord connections are IEC-309 series-2 hosedown-duty devices with dual-saddle cord-jacket restraints (NOT threaded-ring gland-compression type.)

Some plant owners dislike NEMA 5-15/5-20 configurations in any form, for they do not discourage ‘personal-grade/non-industrial appliances’ among the troops in wet locations.

Competently installed thermoset-jacketed metal-armored multiconductor cables for motor circuits have their proponents and flexibility, especially for off-production-floor MCC/VFD layouts were circuit lengths are not too long.

OTOH, for suburb corrosion performance, one killer-grade raceway line is

http://www.stainlessconduit.com

[note 304 and 316 alloys {and commensurate pricing on FIVE-foot lengths} … limousine delivered by tuxedo-clad drivers complete with a complimentary Wolfgang’s autographed caviar sampler and one-year Seaweed Splendor Pilates Club membership]

 

[birddogger]

Thank you to all for the info. To respond to parts of what has been offered so far:

I do know that this particular client wants to get by "on the cheap", so stainless steel, etc. will probably be frowned upon. This is likely going to be a 2000-2500A service at 480/3, and when I told them it would be more practical to bring primary power into the facility and set up a secondary unit substation, they immediately said no, they did not want to take ownership of the transformer and have to maintain it. So I'll be bringing an 8-hole ductbank under the building about 50 ft. and then going up to the second floor with it. So there will be a nice 33"W x 18"D column of concrete on the wall in the 1st floor break room.

I will check with the local health & buildings departments to see what guidelines I will need to follow here.

The Woodhead devices look exactly like the stuff I saw from Leviton, so in the case that I do need to put standard receps in these areas, I'll go with that. But the pin-sleeve devices sound like a much smarter way to go.

Perhaps the cable tray I'm seeing on this previous job is enclosed. Not enough info on the drawings (and no spec to look at) to tell. Still seems like the potential for contamination would be high though.

FYI, this is an "egg-breaking" facility in Texas, where the eggs are broken by large skid-mounted machines, and the yokes & whites are mixed in large enclosed tanks and packaged for distribution (I assume to other food manufacturers). I do not know if there are any open-vat areas here, since I'm still waiting for the client to provide me with a detailed floor plan showing equip. locations, and for that matter a final list of the loads and which ones will require a single-point connection vs. their own starter back at the MCC. Job supposedly goes out at the end of the month, and it's been frustrating to say the least!

 

[umrpwr]

Just to add a little to what has already been mentioned by others it is probably best to avoid locating switches and receptacles in wash down areas as much as possible.

On the projects I have been involved in for food processing plants typically any exposed conduits at a minimum are either going to be IMC or GRC HW conduit and in some cases PVC coated HW conduit. Also all of the projects I have done in food processing facilities specifically prohibited the use of both Unistrut (Kindorff) and continuously threaded rod for supports. Instead we would use stainless steel minis for conduit support which would then be drilled and tapped onto a piece of SS angle and then hung using SS rods which we would thread only on the ends. It is very labor intensive, but the main idea is to minimize the surfaces on which dust and other contaiminents can collect. Also probably on Myers hub fittings.

Also just as a side note you may check FDA guidelines. If the company doesn't have their own construction standards I would check with them since they will have to meet guidelines for food production which are going to be more stingent that local codes.