MYOG HH Tester

Here's a few pictures of a DIY Hydrostatic Head tester. I've had it up to 2500mm H20 without leaking. Easier to use if you have a second person helping. I don't think you can compare the results one to one with published HH ratings because of diameter, rate of rise, etc. But it could be useful for relative testing of your own materials.

Components:
3/4" plywood
4" ABS Cap (ID is 4-1/2")
1/2" MNPT x 1/2" barb fitting. Drill 3/4" hole in ABS cap. Heat metal fitting to cut threads.
Teflon tape
Hose clamp
1/2" ID x 10' tubing
1/4" CCF
5" Carraige bolts, fender washers and wing nuts
Tape measure
Timer



Vessel set on base



Bottom gasket in place



Fabric and top gasket in place



Assembled



Air almost gone



Water in tube level with fabric



First beads of water



Another sample after 3 beads of water



Another sample pushed beyond first three beads



Different batch of silnylon



Couldn't seal this design tight enough to keep it from leaking at very low head.



Possible improvements:

It would be easier to test the corner of a large piece of fabric or tarp if three carraige bolts were used instead of four. I think it would still hold a seal.

Tape a ruler or measuring tape to a wall for measuring head and rate of rise more accurately.

Tap the vessel with a 1/4" MNPT x 1/8" barb fitting and attach a gauge from a blood pressure cuff (max 300mm Hg = 4078mm H2O)

-Lance

Edited by Lancem on 03/26/2011 23:21:58 MDT.

Outstanding!

By attaching a vented bottle filled with water to the other end of the hose you can very easily control the rate of rise.



Every bit as valid as the chrome jobs.

Note the meter stick on the side of the frame.

Edited by greg23 on 03/26/2011 08:07:25 MDT.

Hi Lance

My compliments indeed. What I especially like about your tester is the ease of photography it presents.

I do notice that you are seeing the same phenomenon with ripstop fabric: it tends to leak along the relatively superfluous ripstop threads.

Cheers

Lance,

Great job!

What fabrics did you test and what HH did they provide?

Edited by richard295 on 03/26/2011 06:22:06 MDT.

Richard,

I refined the rate of rise by using a metronome for timing 1/2" increments at 48 per minute and ran a few more samples. I couldn't reach high enough to push the WPB beyond 60". I ran out of tubing before the PU coated ripstop failed.
Error could easily be 25 to 50mm.

Edited by Lancem on 03/26/2011 23:14:07 MDT.

Very simple and elegant - nice!

Interesting that 1sts and 2nds are about the same

2004 silnylon was better

Hi Lance

Post 2004 stuff - pathetic! I am appalled!

Cheers

So what changed in 2004?

Chlorofluorocarbons (CFCs) were formerly used as blowing agents in foam and in the production of silnylon, but were banned from use by the Montreal Protocol. This was an international plan to limit the production and ultimately the release of CFCs. Chlorofluorocarbons contain chemicals that contribute to the destruction of the ozone layer, the barrier that protects the earth from the sun's harmful ultraviolet radiation. Release of this class of chemicals into the atmosphere was scheduled to cease by January 1, 2003. It took about a year for inventory to be depleted. Not only did the silnylon HH level change post this time frame but also the closed cell foam insulation levels also dropped because the new blowing agents are more thermally conductive.

Just awesome!

Richard, as always, very informative. Thanks!

(P.S. I'm not sure if you remember, but I had inquired about the Sawyer packraft paddle as a walking staff in another thread some time back. I took your recommendation, and ordered the paddle, along with a brand new Alpacka!)

Travis,

I have had WONDERFUL adventures with mine. I will be in the bush with it for a month again this summer. I trust yours will also bring you much joy.

Lance - I apologize for the thread drift. Back to your thread topic, I don't have access to any of the 2004 era silnylon but if I did, I would guard it with my life (smile). If I didn't have any of that to guard, I would send an email to Stuart Robb and have him send you some of the top quality stuff he has access to via DE. His second quality stuff is better than any silnylon I have purchased in the US.

Edited by richard295 on 03/28/2011 00:26:33 MDT.

Lance,

In the not too distant future the Protocol B thread will start to show the aging value curves for some materials. You may be the only one on the forum that has a pre-2004 silnylon swatch. No answer is needed now, but at least think about doing a protocol B aging test on one of your "worth their weight in gold" pre 2004 silnylon swatches and posting the results in your thread.

This really opens up some questions. I'm wondering if anyone happened to include samples sourced by Ray Jardine? I bought a tarp kit off of Ebay a year ago which had never been sewn and the Tarp book which came with it has long been out of print. The Thank you note from Ray isn't dated , but I may be able to figure out a date from the UPS rates.

Edited by Meander on 03/28/2011 18:29:40 MDT.

John,

I believe Ray's current silnylon is marketed as being proprietary. If so, it would make an interesting data point in addition to the historical stuff you have access to.

Richard. I'll measure the material vs. the specs for the tarp and selvage and will do it if I can. A quote from a poet I know, Sandra McPherson suggests itself at times like these. " Proof! Proof! . It sounds like something going up in smoke. " Encore!

Improved DIY Hydrostatic Head tester for fabric.

Additional Materials:
3"diam x 5" ABS pipe
2 - 3" test plugs
2 - 1/8" barb x 1/4" NPT fittings
1 - 1/2" barb x 1/2" NPT fitting
1- hose clamp
1/8" ID tubing
Gauge and inflation bulb from blood pressure cuff







The middle fitting is even with the water level of the test vessel. The gauge was checked against another gauge and both were checked against a column of water. The following table shows the calibration results.



There is a learning curve and a bit of art in deciding when a test is 'over'. Water bubbles appear around the perimeter of the circle long before bubbles appear in the 'field'. Sometimes a tiny bubble will appear but not grow in size. Do you count it? With head increasing 10mm per second, looking away, waiting for a 'real' bubble, or other indecision can make a difference in the test results. In any case, for comparative tests of your own materials this works well.

HH numbers for the following pictures are for that specific test, not an average of multiple tests.

First bubbles, silnylon seconds at approximately 400 mm H20



First bubbles, same silnylon seconds flipped over at approximately 300 mm H20


First bubbles, silnylon seconds, approximately at 270 mm H20


First bubbles, silnylon seconds roll end bought 2004, 'back' side at approximately 570 mm H20


First bubbles, same silnylon seconds roll end bought 2004, 'front' side at approximately 1010 mm H20



same test, silnylon seconds roll end bought 2004, 'front' side at approximately 1240 mm H20


same test, silnylon seconds roll end bought 2004, 'front' side at approximately 1760 mm H20



Left, silnylon seconds roll end bought 2004, 'front' side at approximately 1950 mm H20
Right, silnylon seconds at approximately 450 mm H20

Edited by Lancem on 06/02/2011 15:21:58 MDT.

Lance,

You did an absolutely FABULOUS JOB on your pioneering DIY hydrostatic head project! To the best of my knowledge your design is unique… CONGRATULATIONS!

There is now no reason that any forum reader can't now economically build their own accurate tester. There is only one major difference between your design and most commercial designs; the commercial designs generally have overhead lockable test heads. They generally allow a fabric bolt or shelter fly to be tested in a wide range of non-overlapping locations without requiring any cuts.

The relevant extract from ISO 811 says: “After receipt, handle the fabric as little as possible, avoid folding it sharply and do not treat it in any way (e.g. by ironing it) other than by conditioning. Take at least five test specimens from different places in the fabric so that they represent the material as fully as possible. The fabric may be tested without cutting specimens. Areas with deep creases or fold marks shall not be tested.”

The ISO 811 standard is designed for testing tent flies and other similar items where enough fabric is available for at least five random sample testing points. Many of the scraps that were submitted via Protocol B are only large enough for one sample of the standard sized test head. The largest sample received allowed a maximum of only four non-overlapped test head readings.

I had to chuckle regarding your comments regards interpreting test results. I try to follow the ISO 811 standard to the best of my ability and like you, most tests I conduct solely on my own. This evening, my significant other offered to help me test the first batch of aging samples because she knew I was feeling overwhelmed with the amount of work involved. She is a molecular biologist research scientist who routinely conducts extremely detailed experiments in order to design and then write up standard clinical test procedures. She had recently read the ISO 811 standard and told me she knew the procedure before she sat down at the test bench to help me. I was focusing on the pressure gauge ramp reading only and she focused on the sample. She requested a very bright light be focused on the test head at an acute angle and kept her nose only about 4 inches from the sample. The first time she said three drops, I glanced at the sample from about two feet away and the drops looked to me as if they were barely perceptible glistening under the bright light. I said, “Those aren’t drops!” She was not too happy with me telling her she not know how to read and follow a standard. She said, “If they are perceptible in the sense the observer can detect an increase in size they should be counted.” I cowered away and just focused on the pressure ramp and gauge readings. She insisted that is the way the standard should be interpreted, but I can’t really see them until they get a little larger than what she is able to see and they grow faster than what she is able to see. She is a lot younger (I am retired) and so that might explain the differences in visual acuity (smile). Remember this paragraph when you read the first Protocol B Aging results because she was reading the samples, not me.

The relevant extract from ISO 811 says:
“Wipe all water from the clamping surfaces. Clamp the conditioned specimen in the test head so that the face of the fabric will be in contact with the water. The clamping shall be carried out in such a way that water will not be forced through the specimen prior to the start of the test. Subject the specimen immediately to increasing water pressure. Watch continuously for evidence of penetration by water. Record the pressure, as conventional centimeters of water, at which water first appears at the third place in the specimen… Do not take into account very fine droplets which do not grow after being formed. Do not count subsequent drops which penetrate through the same place in the fabric. Note whether the penetration of water at the third place occurs at the edge of the clamp and reject as unsatisfactory any test in which such penetration occurs at a pressure less than the lowest pressure recorded for the other specimens from the same sample.”

In summary some people can see smaller drops growing better than other people as well as smaller size changes and so there may be slight variances at the point where they can perceive 3 distinct growing drops. The variance between the two of us averages in the ~100 mm range; consequently, this seems like a reasonable tolerance between different testers to be deemed equivalent.

Edited by richard295 on 04/04/2011 21:24:57 MDT.

Thanks for your generous comments and extracts from ISO 811. It clears up some questions regarding drop size, drops that don't grow, and drops around the perimeter seal. I'm relieved knowing of the ~100mm range between yourself and your significant other.

I mailed fabric to you today. Some of what's pictured above plus a third.

-Lance

As part of this project I show how I have been doing my fabric testing for the last few years (5+).

I was dissatisfied with the Standard as it stops when 3 drops are visible. I want to know how the fabric behaves at higher pressures, so my tester goes up to 80 kPa or about 8,000 mm water. I record how the fabric is behaving at 5 kPa steps (~500 mm steps). That required that I develop some sort of consistent format for recording: this will be explained after the picture.



Photo 1: red fabric with a single static drop visible. According to the Standard you don't count the drop if is is not growing.

Photo 2: different red fabric with leaky (cheap and nasty) acrylic coating, leaking everywhere.

Photo 3: blue fabric with static drop, leaking drop, and several micro-jets spraying away.

Graph: many fabrics. Horizontal axis is pressure in 10 kPa steps. Vertical axis is my rating system, explained below.

Level 1: dry
2: 1-2 static drops. Should they be counted? They are not growing.
3: 3-4 drops, mostly static.
4: 5-10 drops, some might be growing extremely slowly
5: very slow growth in drop size
6: slow growth in drop size
7: slow leaking
8: medium leaking
9: microjets
10: definite flow

Ignore water in ring around edge of sample. That can have a number of causes, including leakage.

As you can see, some fabrics start to fail at a certain pressure and get steadily worse and worse as the pressure goes up. Other fabrics reach a pressure (often low) and go all to pieces quickly. But some other fabrics show a few drops at a threshold pressure and then don't get any worse despite a considerable increase in pressure. Finally, some fabrics just don't leak. (They tend to be heavier ones.)

The interesting case is where a fabric (often with a silicone coating) allows a few drops to become visible at a moderately low pressure, but those drops do not grow in size despite a significant pressure increase. I have seen quite a few of those. What is happening there? How do you grade such fabrics?

Cheers

Edited by rcaffin on 04/05/2011 05:01:10 MDT.