Measuring Sealing - Ovens

[cook0]

Hello,

I am wondering if anyone of you have any tip (or could direct me to appropriate person/institution/website) for as accurate, as fast and as quality as possible method for measuring sealing in VAPOUR ovens? Most important factor is time because the control is 100% in production procedure. But all factors (main is obviously flux) such as heating, condensation, etc must be considered and all elements of ovens.

Any tip on how to measure sealing in said case would be appreciated.

 

[cook0]

hello?

 

[MikeHalloran]

Are you talking about a vapor phase oven as used in reflow soldering?


Mike Halloran
Pembroke Pines, FL, USA

 

[cook0]

Yes vapor ovens such as this one:

http://media.bosch-home.com/Files/B..._def.eps?AntiCropWidth=550&AntiCropHeight=420

Need some good method, very accurate that includes all components (flow - air / sealing) inside the ovens. The method for measuring/analysing/testing sealing must be as fast as possible. A lot of ovens are made hourly and control is 100%.

 

[MikeHalloran]

Well, what are you doing now, that isn't working?

Mike Halloran
Pembroke Pines, FL, USA

 

[Compositepro]

The correct term for that in English is a steam oven, apparently consumer type. The question is still unclear.

 

[cook0]

MikeHalloran, Compositepro: Nothing at all is being done from aspect of sealing testing. Inspection/testing is being done just for flow but need some good suggestion how to measure/inspect sealing. That inspection will be done directly on production line, not in laboratory. Im just asking for some good suggestions how to measure it (the sealing) so really all directions of all components will be included. Fan is going to be even more complicated than the front window. There are also other components such as bus with water, lights, etc who have a lot to do with sealing. Im asking for method, no need to list components, I will (at least try to) do that on my own.

 

[MikeHalloran]

A lot of ovens are made hourly ...

If you're running a factory and you don't have an exact number for this, you're doing a damn poor job of it. We need a number to evaluate the cycle time you can tolerate in order to propose reasonable and achievable solutions.

... control is 100%.

I have no idea what you're trying to say here.
It appears that you are presently controlling nothing.


Since you've provided essentially zero useful information, I'll speculate:

Since it's a steam oven, I'll guess that your 'final test' involves starting a cycle, and looking for steam leaks.

... and that ALL of the units are visibly leaking,

so you're trying to quantify the leak rate to allow you to say that you're inspecting per some procedure that you don't have yet,
with equipment that you don't have yet,
to some acceptance criterion that you don't know yet,
so that you can say you are measuring your quality
by inspecting all units and accepting most of them,
instead of what you are currently doing,
i.e., going through the motions of inspection,
and shipping everything you make.
... in which case you really don't need a QC operation, do you?


Mike Halloran
Pembroke Pines, FL, USA

 

[cook0]

Don't understand what are you asking? Im talking about measuring of SEALING but we might misunderstand each other what is means as sealing term. Units per hour or per day vary a lot based on many factors. Currently I don't have the number for vapour ovens but for all types of ovens, most likely around 1200 per day but often this number can increase a lot. Surely I would be interested to use available tools for measuring sealing (im aware i haven't listed to you the tools yet) but im open minded in new tools as well. I apologize but im not sure what are you suggesting in your post? I cannot recognize any measuring advice from it.

 

[Compositepro]

Use compressed air to pressurize the oven to the operating pressure and measure the flow rate of the compressed air. The flow rate of air is the leak rate.

 

[MikeHalloran]

Thank you Compositepro.
So, cook0, is there a way to pressurize the oven for testing?
Can the oven itself measure its internal pressure, or otherwise participate in the test?


Mike Halloran
Pembroke Pines, FL, USA

 

[MintJulep]

Engineers work with quantifiable information. An so far you haven't given us any at all.

1200 per day, or a lot more. How long is a day for you? One eight-hour shift? Two shifts? Three?

How many lines are making these things?

How much pressure are the ovens designed to contain? How much leakage is allowed?

Since you are forcing us to guess, I will guess that the flow rate of the allowed leakage will be difficult to measure accurately.

I would suggest pressurizing, then measuring the time of leak-down.

 

[cook0]

That number 1200 is for two shifts per day, each 8 hours. Per one shift is approximately in average between 650 and 660 BUT this number is for all ovens and not only vapour ovens. For ovens (all types) there is one production line only. Don't know approximate frequency how often occurs vapour ovens on the line. We have more lines but for different products that are irrelevant to this topic (stoves known as cookers, cooking hotplates, kitchen vents, etc). Yes the "normal" pressure can always be kept while testing (=pressurizing). I don't think ovens can by itself measure the internal pressure, this is done with equipment in laboratory.

Compositepro are you referring with your term "flow rate of air" to the sealing? Flow and sealing isn't the same but yes leakage can be defined as reverse sealing.

 

[MikeHalloran]

Okay, 660 units per shift suggests that you have to test an oven in ~43 seconds or less so as to not slow the line down.

As Compositepro suggested, that involves making some kind of test connection to the oven cavity, pressurizing to some reasonable pressure with clean air, shutting off the air supply, recording the pressure decay over time T, then venting any remaining pressure, disconnecting the test connection and sealing it.









Mike Halloran
Pembroke Pines, FL, USA

 

[cook0]

I am testing something like this at the start of this project already. I use flow machine, plug the cable at the back of oven and put GUESSED value of pressure inside the oven which is currently filled with polystyrene. Im not sure about what % of interior (referring to entire interrior area of oven) is filled with it because I haven't filled polystyrene personally inside but with look of an eyes only, it is around 90 to 95%. Not sure about air, if any and where, between polystyrene and oven's walls. So for the start what is being done is putting polyvinyl's bag (piece of bag) near seal, cover it with some aluminium material to prevent further air leakage and simple push on machine the pressure inside. Then how much bag's bends forward is for the start one of indicators I am interested for. However this method is impossible to be used for obvious reason - time consuming too much. Other reasons are here too why such method cannot be used such as:

- not sure how to evaluate the bag's forward bending and how to measure it. Bending is different in the center of bag than on different locations.

- don't know about fixed pressure - what to use, thats why I didn't answer you about max allowed limits - still researching. I only know working pressure meanwhile vapour oven will be in operating mode (client side) or testing method (my side) or production/measuring method (workers near production line side).

- i think the method i described for the START (just to do some progress) of project isn't even accurate at all

- not only described location (doors/bag) but different oven's elements also have air flow/leakage - sealing!

- too much pressure could cause door to open by itself at the top side of door (fastened are at the down side - leakage too). Equivalent is said polyvinyl bag.

- etc, probably many more reasons. Gotta dig further to research.

Is this what you were referring to? Venting of remaining pressure can be sucked from oven, thats ok but you probably meant recording sealing (how? via what? which locations? a lot to be said here) and not pressure. Pressure is shown on machine screen. Noting it down, thats it, no problem about the actual pressure. Could you clarify in more detail?

 

[MikeHalloran]

We here were talking about attaching a compressed air supply, dry, filtered, regulated, to the oven cavity by means of a quick connect or perhaps a connection to a vent line. ... but _we_ know nothing about the architecture and specifics of your oven.

Pressurizing the oven by means of a bag is a clever and perfectly acceptable way to do a leak test, provided you can make and demake a leaktight connection quickly enough.

The protocol could be as simple as:
- attach the bag, say to the top of the oven.
- inflate the bag.
- rest a book on the bag (to apply a controlled pressure).
- wait for X seconds.
- the oven fails the test if the book collapses the bag in X seconds.
- detach the bag.


Mike Halloran
Pembroke Pines, FL, USA

 

[Compositepro]

A U-tube manometer made from some clear plastic tubing, filled with colored water, will measure pressure very accurately, and can detect a very small pressure loss due to a leak.

 

[cook0]

What do you mean? For the start im using such air pressure machine:

http://www.appliedmeasurement.com.a...detector+for+production+testing-ATEQ+F520/150

Bag might be, at least for start, appropriate way but its too time consuming. The workers won't be attaching bags on every single ovens. It would take too long. Also hard to measure how much (how far) does it react (bends).

Compositepro are you saying linkage between ovens and manometer should be tube in plastic material?

Seems like it will take a while to even recognize what are you suggesting....