UPDATE 2:
I just remembers something. I'm using HDPE pipe. Does the ductile nature of HDPE mean that it is effectively avoiding surge due to localised elastic expansion?
That would probably explain why I'm not seeing high surge pressures and tending to be worried about their resulting...
UPDATE:
You're right. It seems the elevations have been changed. There is a very small pipe RISE (2m). Not withstanding, should vapor formation be avoided even if resulting surge is within design limits.
Cheers.
First of all, you have to understand what you require a measurement for.
Gauge pressure is used to measure the pressure difference between two mediums. This is very important for hydraulic equations, where you are concerned with pressure differences. barg, is used to reflect the pressure...
I believe from memory, that sheet gasket is not recommend about about 2 MPa.
Sheet gasket is relatively cheep and useful in relatively 'easy' applications (ie low temp, low pressure, 'safe' fluids, etc).
Hi,
I have a somewhat interesting problem involving pumping water downhill. I have a system which has a static drop of about 6m from inlet to outlet, with a slight crest rise (2m) in the middle, hence the need to a pump system.
I've modeled a power trip simulation for water hammer. The pipe...
Hi,
I'm after an isolation valve for a waste water treatment plant. Our inlet pipe is above the level of the treatment plant, so on power failure of the plant, I would like to isolate the inlet flow so:
1. The pipe does not drain and draw air through vacuum valves.
2. The inlet tank does not...
no idea if I can edit posts....
http://www.hosemaster.com/products/expansionjoints/comparisonchart.php is a very useful table.
I see the tied bellow takes lateral movement. I doubt they can really take much lateral movement though (length/diameter dependent).
As a general mental note, I think...
rmw,
I believe I understand exactly what you are saying. I agree that tie rods will resist thrust movements.
My question is; in what system can you require the use of a thrust restrained expansion bellow, that also has a requirement for axial compression?
Tied bellows are useful for taking...
Hi,
For people familiar with AS 1579.
I'm looking at using this standard for a pump application with ~250 m of head, ~1000mm ID pipe. I haven't used this standard before (much more familiar with AS4041) so would like some clarification on what I seem to be reading.
Is my understanding correct...
-rmw
Tie bars are only there for ease of assembly. To overcome the pressure thrust and spring rate of the bellow, both sides of the pipe has to be anchored. Therefore the bellow could have been installed without tie rods - ie it is free to compress, but the anchorage of the pipe will stop...
Four bolts on a tie rod as you explain make the expansion bellow a rigid member!
Two bolts will theoretically allow compression and not expansion. However the thrust force is usually sufficiently high that you still need to restrain (anchor) the pipe both sides of the expansion joint. Therefore...
Thanks for the feedback.
I played around with some modelling programs and they confirmed the 'simple' Joukowsky result.
I think that my original reasoning of check valves was correct. That they can't reduce water hammer, but they can increase the problem due to rapid closure at reverse...
Laziness?
There is no reason why air valves need to be placed anywhere but local high points. Even then I can't really see the need for them, apart from to aid filling as I find it unbelievable that so much air could enter the pipe.
The other reason may be the water industry trying to minimise...
hmmmm. I think I may have discovered my mistake.
The pump is 'driving' the water up the hill. Due to pump inertia, the pump continues to drive the flow and until the check valve closes. If it is a perfect check valve there will be no pressure surge. Is this correct?
So with a pump, when it...
I think there may be two issues:
1. In water industry air valves are used liberally because they can be. No one cares (too much) if water leaks and it's a nice safe lazy option to put many in. For HC, the fluid is worth allot more and generally it is not acceptable for any of it (including...
I've been doing some reading on water hammer and trying to 'really' understand it.
I've been asked to look at a relatively simple problem of a pump station pump water up a relatively constant slope. Initially this was to be done by others, but I was keen (stupid) to learn.
Details:
Flow: 50 MLD...
Cheers AHT. Looks like some interesting reading.
racookpe, I didn't think of that. However I'm out of the schedule pipe wall thickness. Will have a look around though.
Try and do a quick calculation.
If you have a CV curve of the valves, work out what the maximum pressure drop is. This will give you an idea of whether it's the cause.
My limited experience is that for such small run of pipe, cavitation would only be occurring at a fitting. Straight pipe would...
