Jerking in Lines

'Water hammer'. Force is rate-of-change-of-momentum.

• Slow down the speed of opening or closing of the utility valve.
• Anchor the pipes properly before they fall off their supports and brain someone.

Put an air chamber (like a small accumulator) in the line.

iawtc

a heavy jerking and vibration is observed in the line

Thats water hammering. You cannot avoid this for it is common where the same heating lines are used as cooling lines. You hear sharp crackling noise.

As stated, water hammering.

If feasible, you may install high point vents. These are valved stubs located at the highest points of system as well as where any vertical change of direction takes places in the system. A simple petcock valve should suffice for most applications and in many cases may be hot-tapped in (depends on pipe material and service). The venting of these high points will allow trapped air to escape instead of hammering against pressure diffs.

Also remember that air compresses much more than water and can create other problems as a result - especially if there are pressure sensitive monitoring points.

Much luck to you.

cr3

This is not my subject so feel free to ignore me, but: water hammer is normally associated with turning OFF valves rather than turning them ON. You can alleviate it by turning off the valve slowly or incorporating air reservoirs just before the valves. What you have may be more to do with expansion and contraction of the pipe work due to changes in temperature: in which case you can alleviate it by incorporating expansion "loops" in the pipework.

It may help to place a "T" fitting and 3' of water pipe (same diameter as the lines) dropping down at the "T" - with a cap (or pressure valve) on the end. It should be about 2' from the valve. This works like a capacitor and helps absorb the "bounce". This was common practice in days gone by, especially in apartment buildings. This also has worked to quiet steam pipes to radiators as well.

The above answers are correct...water hammering. Usually it's more associated with valves closing but I have seen both opening and closing cause it, depending on the pressure and flow volume. It can cause a lot of stress on your pipes.

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I have these arrestors installed throughout my process, they are cheap, and they work well. Install them as close to the problem source as possible. My primary water line runs through my parts room right over my head and the hammering was driving me nuts. Now, if I hear any hammering I go into my PLC network...watch for a few minutes...listen and see what equipment just shut water off when I hear it and have the weak arrestor replaced. Aah...peace and quiet.

The web-site Switchman directs us to shows products that evolved from the old-style water capacitor. They are more compact, and should work quite well. (In my opinion they are over-engineered, and designed to fail after a pre-determined period of service, therefore will require replacement.) The drop-down pipe however is effective, and will never need replaced - it is easier to purchase and much less expensive. I work in Mexico, and I don't like to spend money unnecessarily.

You've got my curiosity up too: how do these drop down pipes work? If they were "pointing up pipes", and, full of air I could understand how they could absorb the shock. But drop down pipes must be full of liquid, which is effectively incompressible.

Well shoot, SPIJman...you've gotten my curiousity up so now I'm going to have to try that. I have a 500' section of 2in line running into my spiral freezer for defrost flood that has a hammer on it and the line needs to be replaced next month. I'll try your method there.

I also do not want to needlessly spend money on something where there is an equivalent solution.

Simplicity is genious, but taking a simple thing and complicating it, then tailoring it to specific applications when the "one size fits all" rule would often suffice, is much more profitable...

I guess I am not clear on whether or not they are separate process lines. Sounds like water hammer though, have you increased your hot/cold water consumption recently? Utilities are usually just considered to "be there" when a new project comes along...

Rember, there is a lot of air (oxygen) in water.

As the liquid flows over the top of the drop, it slightly lowers the pressure in the drop pipe. As the valve closes, the drop absorbs the pressure that would normally slam against the valve seal. The water will compress a bit, and the pipe will expand ever so slightly. A piece of foam similar to that used to wrap pipe can also be inserted into the drop for added cusion (sealed air bubbles), but is rarely needed unless pressures are extreme.

The vibration occurs when the water hits a dead end, and has no where to go - except back in the opposite direction. This causes further compression and reverberation.

You can experiment with a capped 3' pipe full of water and a (plastic) rod that fits just tight enough to slide inside, but will prevent most of the water from leaking past. Bump the rod with a known force, and you will get a general idea of how much force can be absorbed.

It may help to understand if you can compare the water current to electric current.

Basically you are heating/cooling a Reactor jacketed/limpid coil . Heating with steam & draining the lowest point with a steam trap. This may be one whole reactor or the Reactor is sub-divided in 3 heating sections(botton/middle/top) depending on the volume you wish to process. Here you will be having 3 steam inlets & 3 trap outlets. When cooling is required you use the trap side as inlet of cooling water and the steam inlet side as return.

In steam you cannot avoid water hammering because of sudden switch over from steam to heat to water to cool.

To avoid waterhammering you should switch over to thermic oil heating for heating. The oil will then go to a cooler and the same oil will be used for cooling. Because the heating oil is going to the cooler from the reactor and returning back there is not a sudden drop in temperature but gradual drop hence, no thermal shocks take place and the cooling cycle is attained.