View unanswered posts | View active topics It is currently Thu Mar 28, 2024 8:41 am



Reply to topic  [ 20 posts ]  Go to page Previous  1, 2
 Station EB0FCB7A located outside Alamogordo is finally up 
Author Message
User avatar

Joined: Mon Mar 17, 2014 10:34 am
Posts: 14
KingCobra wrote:
Glad to help. Thanks for sharing those pictures, your unit looks very professional but I do agree with hey/Harlan, improvements can be made. Please remember that the EPA units and those used at the WIPP all use HEPA filters. The main reason I believe is so the filter/sample can be sent off to be tested using a scintillation counter if radiation above normal is detected. Of course using a HEPA filter will give you better detection rates too as the fallout would build-up on the filter and be more easily detected.

I assume that your fan draws the air in from hole near the bottom of the geiger counter? If not, it should because the geiger tube for detection is located in the bottom of that model geiger counter. Then a HEPA filter should be installed over the hole nearest to the bottom of the geiger counter. This filter will obviously need to be replaced from time to time. You would also want the bottom of the geiger counter as close to the filter as you can without limiting the airflow. You want the most airflow you can reasonably get out of a fan with those dimensions.

Your geiger counter comes with a preset alarm of 100 CPM I believe from the manufacture. I would make sure your does because if you were to see high readings on the NETC network from your unit, you need to be able to verify it is not a software problem. By having your alarm set on the geiger counter you should be able to hear it alarming from the ground with no need to climb up and unscrew your enclosure to look at the screen. Furthermore, just because your geiger counter display might read a 100+ CPM value does not confirm radiation is present. The GM tubes in the units do fail (in all geiger counters) and can create false readings. Having a 2nd geiger counter is always a good idea to have available to confirm the detection.


Hi King, and Harlan too.
Firstly, I am always open to suggestions so always feel free to comment.
I'll try to address some of your questions, and also what I have in mind for Mod 2 on this.
I know the EPA stations use HEPA filters, I believe the rational is if they start seeing high counts they can send the filter into the lab for spectral analysis to see exactly what type of nucleotide they are dealing with, Cs, Pu, etc. but I am hardly an expert on the subject.

I know the GM tube is located on the bottom of the unit as I popped the cover on it for a look see. Nice electronics on the GMC, but the Chinese GM tube they use leaves a lot to be desired. Alright for the money, but it can't begin to compare to my Ludlum survey meter with it's pancake tube.

I do have two professional grade Geiger counters on hand to verify the readings of the GMC if things get wonky.

Here's a more detailed explanation of how this is set up, just to clarify things, and you can refer to the not so good picture at the bottom of this post.

The intake port is on the left side of the box (2 inch pvc elbow) butted against it is the bottom of the GMC-320. The fan on the right side is blowing outward, so when the cover and gasket are on, the left port is the intake and the right port is the exhaust. The fan is 60 MM in diameter and is rated at 25 CFM (which is pretty phenomenal for its size). As the box is physically not that big, I believe that when it is closed up, the airflow should be more than adequate. I could have used a bigger enclosure and fan, but everything you see in this setup I already had on hand, and did not have to buy anything, (I hate the "B" word). I do have some course filtering material crammed in the intake port, which you can't see in the picture, mainly to keep sand out.
So, here's what I am thinking to improve this:

The GMC is mounted using adhesive backed Velcro tape, so I have an inch or two wiggle room. I am going to try and find a air filter such as used on a lawn mower engine, or such, the correct size, and mount it on the inside covering the intake port, then butt the bottom of the GMC right up against it. Guess I should have thought of the earlier.

Let me know what you think of this idea, and if it would be a viable improvement....
Image


Sun Apr 27, 2014 9:42 am
Profile
Moderator
User avatar

Joined: Mon Jan 28, 2013 7:40 pm
Posts: 2885
Location: Illinois
I would highly suggest a HEPA filter only. You could cut up and use the Holmes brand filter like I use easily found at WalMart.

I own 3 pancake geiger counters and while they are great units, they would not be good to use like we are doing outside 24/7 and with fans. The GMC-xxx GM tubes win hands down for durability & cost when compared to the pancake GM type.

The suction alone from the fan could damage a pancake GM tube. If the suction don't, likely the moisture would. If neither of those damaged it, there is always just risk of failure and with a 90-day warranty on the pancake tubes, that is a costly replacement.

_________________
MY OUTSIDE RADIATION MONITORING STATION:
South Beloit, Illinois - GMC200 Outside on HEPA air purifier, ground level, facing West.
http://netc.com/chart/view.php?n=1%3AEB5A139C


Mon Apr 28, 2014 12:08 pm
Profile
User avatar

Joined: Mon Mar 17, 2014 10:34 am
Posts: 14
KingCobra wrote:
I would highly suggest a HEPA filter only. You could cut up and use the Holmes brand filter like I use easily found at WalMart.


Ok, sounds good to me. What department in WalMart do they have these filters?


Mon Apr 28, 2014 1:53 pm
Profile
Site Admin
User avatar

Joined: Mon Jan 28, 2013 6:51 pm
Posts: 741
Location: Arkansas
In Arkansas, the filters are next to the water filtering systems.


Mon Apr 28, 2014 3:53 pm
Profile
User avatar

Joined: Mon Mar 17, 2014 10:34 am
Posts: 14
hey wrote:
In Arkansas, the filters are next to the water filtering systems.


Thanks Harlan.


Mon Apr 28, 2014 6:59 pm
Profile
Moderator
User avatar

Joined: Mon Jan 28, 2013 7:40 pm
Posts: 2885
Location: Illinois
EB0FCB7A wrote:
$2
KingCobra wrote:
I would highly suggest a HEPA filter only. You could cut up and use the Holmes brand filter like I use easily found at WalMart.


Ok, sounds good to me. What department in WalMart do they have these filters?


Sorry for my late reply, thanks hey/Harlan

@EB0FCB7A - You might be fine using a furnace filter that is or close to HEPA standards. This would likely be the most cost effective choice and yo could cut out what you need.

_________________
MY OUTSIDE RADIATION MONITORING STATION:
South Beloit, Illinois - GMC200 Outside on HEPA air purifier, ground level, facing West.
http://netc.com/chart/view.php?n=1%3AEB5A139C


Tue Apr 29, 2014 1:10 pm
Profile
User avatar

Joined: Mon Mar 17, 2014 10:34 am
Posts: 14
KingCobra wrote:
You might be fine using a furnace filter that is or close to HEPA standards. This would likely be the most cost effective choice and yo could cut out what you need.


Hi King
There's an idea. One other thing that occurred to me would be to try a HEPA rated vacuum cleaner bag. That seems to be the best value or the money, especially since I am probably going to have to change it every two weeks here in the desert. Of course I don't know how much it would cut down on the airflow. Know anyone who has tried a HEPA vacuum bag?


Wed Apr 30, 2014 5:29 pm
Profile
Moderator
User avatar

Joined: Mon Jan 28, 2013 7:40 pm
Posts: 2885
Location: Illinois
EB0FCB7A wrote:

Hi King
There's an idea. One other thing that occurred to me would be to try a HEPA rated vacuum cleaner bag. That seems to be the best value or the money, especially since I am probably going to have to change it every two weeks here in the desert. Of course I don't know how much it would cut down on the airflow. Know anyone who has tried a HEPA vacuum bag?


8-) I never thought of vacuum bags, thanks for the tip! I will confess, I do not change my filter as regular as I should.

_________________
MY OUTSIDE RADIATION MONITORING STATION:
South Beloit, Illinois - GMC200 Outside on HEPA air purifier, ground level, facing West.
http://netc.com/chart/view.php?n=1%3AEB5A139C


Thu May 01, 2014 11:51 am
Profile
User avatar

Joined: Mon Mar 17, 2014 10:34 am
Posts: 14
KingCobra wrote:
$2
EB0FCB7A wrote:

8-) I never thought of vacuum bags, thanks for the tip! I will confess, I do not change my filter as regular as I should.


Ok, here is Mod 2.
This is a HEPA rated vacuum bag on intake butted against the bottom of the GMC.
The HEPA bag is a heck of a lot thicker than normal bags and I could barely blow through it using lung power, but surprisingly it did not cut down the air flow as much as I thought it would once the enclosure was sealed back up.
I guess I will try this for a couple of weeks and see how clogged up it gets. Once again I had to clear the data history, so I am starting from scratch...
Image
Image


Sun May 04, 2014 12:57 pm
Profile
Moderator
User avatar

Joined: Mon Jan 28, 2013 7:40 pm
Posts: 2885
Location: Illinois
Looks really good. Since your unit is sealed so well from water and sunlight, you might consider removing the GMC geiger counter cover. This will allow the geiger tube better detection off the filter.

_________________
MY OUTSIDE RADIATION MONITORING STATION:
South Beloit, Illinois - GMC200 Outside on HEPA air purifier, ground level, facing West.
http://netc.com/chart/view.php?n=1%3AEB5A139C


Mon May 05, 2014 4:26 am
Profile
Display posts from previous:  Sort by  
Reply to topic   [ 20 posts ]  Go to page Previous  1, 2

Who is online

Users browsing this forum: No registered users and 39 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group
Designed by STSoftware.