Anyone know about vacuum rating?

Well, I lay a one foot piece of pipe on my bench and it fits just fine. But a 20 foot piece -- heck, it lops over both ends and keeps cloths- lining me every time I walk by.

(Lloyd, how am I supposed to respond to that unk's response than to say something off the wall _without_ a smiley face? Honestly.)

There was an engineer involved in there someplace, I know it.

Larry Jaques fired this volley in news: snipped-for-privacy@4ax.com:

It comes in solid, too.

20HP 3-phase regen blower; it'll pull 11" at many, many CFM

You mean, there's a formula for area? Maybe that's where they screwed up!

1/2" MDF, -0.040" 'deglazed' on both sides, and edge-sealed, all-around. It's sort of the standard for this kind of machine, doing full-sheet work.

This stuff must not come over in anything close to the order posted. I posted all that stuff yestiddy.

I'm pretty competent at vacuum work, too. I just want to know if anyone has ever seen a vacuum spec for 2729.

Lloyd

Tim Wescott fired this volley in news: snipped-for-privacy@giganews.com:

That is what I was referring to about things not coming over in the order posted. Your response arrived before his inane comment.

LLoyd

Tim Wescott fired this volley in news: snipped-for-privacy@giganews.com:

yep... and to the 'engineer' who suggested I pull 30" and wait to see what happens.

Ehhh.... I'm reluctant to do that here in Florida. I think I'll stop at about 29.96".

LLoyd

By the book and never in the field before, no doubt. Engineers, the 2nd Louies of manufacturing!

But what for? Where's the leakage? If you're using holey spoilboard, have you considered dropping some vinyl over the leaks to bring up the vacuum?

That thing sounds like an expensive bitch just to run!

I've been noticing that. I see stuff today which I didn't yesterday, but it was posted yesterday. It's fine for people who log on once every two days, I guess. I'm pleasantly surprised at how well Usenet does work, though. What a great idea!

Why would there be a vacuum spec for waste pipe (with a mess of holes in it) which will never see vacuum?

Regular sch 40 will handle a good vacuum, and I've seen numerous people using it for vac storage. But sewer pipe is thinner, I believe. I doubt 11" will harm it, though. SWAG

You're being too hard on engineers, because you don't notice when we succeed in some stunningly creative way. It's just that when we fail, it's often in some stunningly creative way.

Well, it cost me a double-sawbuck to figure out what I needed to know, but it leaves me questioning some of the manufacturer's claims.

I took a length of good, clean, and round 2927 pipe (no Larry, no holes... this is solid pipe), capped both ends, BRACED the ends inside so they could not initiate a collapse, and stuck in a reefer fitting for my Robinaire pump... then started gradually pulling it down.

Now, three of the manufacturers of the stuff claimed "ability to withstand column separation up to five stories high". Working backwards, a suddenly-separated column of water-borne 'stuff' would initially pull a vacuum of about 22", before it began to boil and make up the vacuum.

So I felt pretty good about getting through this OK. nahhh.... at about

18", the whole pipe gently folded up into a flat ribbon of PVC, with only the braced ends staying round. (kinda neat to watch, even though that was the expected failure mode)

So, I'm going to have to find room for two runs of 3" Sch-40 under the table for each of the four table zones.

I'm glad I didn't pipe it first, then find out!

Lloyd

A buried pipe is supported against bulging out at right angles to where the collapse begins. Yours wasn't.

"Jim Wilkins" fired this volley in news:mbt9mu$pih$1 @dont-email.me:

Exactly how does that address "five story high vertical column separation"?

This stuff is not used only buried. It's approved (in some few places) for vertical vents on DWV systems.

Lloyd

And so often is a stupendously stunning creative way!!! Success is generally so benign in comparison

The simple engineering solution to that is to tell Corporate that you need a round-trip ticket to Death Valley.

Young engineers tend to an arrogant self-confidence not supported by their practical experience. As lab manager I had to tactfully show them that they still had very much to learn, while respecting what they did know.

For example one of them kept requesting another case of Polaroid film for the scope camera. When I finally asked why he told me he was attempting to determine how fast a fuse would blow to protect his circuit. His schooling hadn't covered real-world device characteristics, or apparently how to least-squares fit a curve to noisy data points.

So I gave him a brochure that explained the subtleties of fuse ratings.

-jsw

How can you pull a five story (50') vacuum?

The rating may be for the overpressure from a five story high water hammer.

Google isn't too helpful.

-jsw

"Jim Wilkins" fired this volley in news:mbtdq5$e3f $ snipped-for-privacy@dont-email.me:

You're forming ideas without reading any of the words. "Column separation"... I've quoted it several times, and you don't seem to 'get it'.

First, you DON'T pull a "five story vacuum", but you CAN have five stories of water fall straight down under the force of gravity while the top of the pipe is stoppered-up somehow.

Then, with just a teensy bit of scientific history under your belt, you'd be able to determine that the water will drop about 16 feet, essentially unimpeded, and leaving a vacuum in its wake, until the vacuum holds it up at 33.9ft... after which the vacuum is relieved fairly rapidly by the surface of that column's boiling into water vapor to fill the void.

This is junior-high general science class stuff, not the stuff of "engineering". (well, at least only the most basic underpinnings of engineering)

Lloyd

Vertical column separation dynamics are about the water hammer that follows. It pertains mostly to tall pipes and to a failure of an upstream valve or pump.

If the column is water, the pressure inside can't drop below the vapor pressure of water -- around 20 torr (20 mmHg) at room temperature.

Ed Huntress fired this volley in news: snipped-for-privacy@4ax.com:

Ah, but it can drop lower than that -- instantaneously. It's rapidly followed by "makeup" by the vapor pressure of the water; but there's time involved in that's happening.

Lloyd

Ed Huntress fired this volley in news: snipped-for-privacy@4ax.com:

I should have said that I understand it's an asymptotic relationship at low rates of fall, but with 'overshoot' when the fall is rapid, like when the water is _already_ falling at acceleration and then the pipe gets stopped- up.

LLoyd