In need o eddication -- valves and water hammer

Jamie Hall

I think I need some education here from others far more knowledgeable...

Background: I'm quite familiar with valves and the way they can and do cause water hammer -- sometimes quite spectacular -- in large systems. Think control valves for city water supply aqueducts (36 inch cone and butterfly valves, surge chambers) and hydroelectric power plants (ditto, plus bypasses and the like) and the rules... like, if a valve is allowed to close rapidly (defined there as 30 seconds to several minutes) it must have a close surge chamber or a slow closing bypass... and a valve element always closes against the flow...and such like. And a valve with static pressure on must always open, likewise. (ball, plug, and gate valves are interesting -- they must be powered both ways, and gate valves are not wanted when there is flow, unless there is a bypass -- the vibration when they are almost closed can be quite destructive at anything much less than quarter open)(for that matter, all big valves are powered both ways -- sometimes motored, sometimes hydraulic rams, sometimes manual)

But. That, obviously, doesn't apply to the sizes we deal with here on the Wall! And I find there are holes (gaping holes!) in my knowledge which need filling.

So. Do I presume that zone valves always close against the flow, or if they are ball or plug types, slow powered close? If they are spring close, is there damping? If not, why not? Could they be wired, if they are fast closing spring close, so that the circulating pump is turned of while they are closing, and turned back on if needed?

Just thinking that water hammer arrestors are addressing the symptom, but not the problem -- and that always annoys me.

Anyone? @Ironman ? @hot_rod ? @EBEBRATT-Ed ? @GW ?

Ironman

@Jamie Hall
I believe that you have far more knowledge and insight than I would.

As far as ZVs go, I always go by the book + what I've learned from folks like Dan and others on here. Doing it that way, I've never had a ZV issue so far - I've got two going in today with a boiler replacement.

Jamie Hall

Ah no, not really, @Ironman . You have boots on the ground on this sort of thing, I don't. That's important.

GW

Well I never really had the need to study this topic out I’m afraid to say. Some grizzled plumber there probably knows zone valves like the back of his hand. I had a zone valve slam on a remodel job about 20 years ago. If my memory serves me it may have been backwards (maybe the flow was reversed, don’t recall). We talking hydronic heating Jamie? 

pecmsg

I’m still questioning a spring loaded valve causing water hammer! I personally don’t ever recall seeing it happen with out underlying reasons. 

pecmsg

@Jamie Hall
Those zone valves are Ball Valves

Jamie Hall

pecmsg said:

@Jamie Hall
Those zone valves are Ball Valves

But -- if a ball valve closes quickly enough, it can slam. So how is the closing rate controlled? Is it?

And yes @GW -- hydronic. About which my practical knowledge is somewhat lacking. And @Youngplumber -- it is the fast stopping of water which is the problem -- the valve snapping shut stops it really fast!

As I said in my first up there, I have some actual practical experience with really big valves, where the water hammer shock wave can quite literally blow the pipe apart (ruins your whole day) -- but I want to know more about these pesky little ones...

EBEBRATT-Ed

I think flow velocity has a part to play in all of this. Keeping the velocity down (not under sizing the pipe), also using multiple zone valves in parallel and using valves with the slowest operating actuators

Solid_Fuel_Man

All valves I'm aware of used specifically for hydronic zoning are of the slow closing type. 

Slowest being heat motor valves with wax elements and a restrictive globe valve design.

Then there are the typical synchronous AC motor valves like the famed Honeywell V series, the Caleffi Z-One, Erie etc. They all have nice little synchronous motors which dont mind being in a stalled position, and serious gear reduction. The gear reduction is what acts as the speed limiting during the spring closing the valve when the power is removed (power open, spring close). Caleffi even has a nifty clutch to allow the motor to freewheel after the valve is seated closed. 

The flow traveling toward the closing element and the low velocities in hydronic systems seems to be the key factors in zone valve attenuation. High velocity and over pumping violate that. 

I have no experience with ball valves used as zone valves (Taco Century). Only used them as a 3 way configuration for mixing. 

Delta P pumping in commercial jobs with lots of zone valves works wonders. I've put on many VFDs and pressure transducers in schools and hospitals on 3 phase pumps. Solves the velocity issues and saves electricity at the same time. 

EdTheHeaterMan

Here is the inside of the Honeywell Zone valve body that has the problem.


The top section is removed had has a black ball that a pair of springs in the actuator head forces against the inlet orifice of the valve. If the valve is installed properly and the system pump has more head then the valve can handle the black ball inside the valve chamber can slam against the orifice and stop the water flow rather quickly. This flow stopping too quickly can cause poorly supported piping to move and cause a noise that some might call "water hammer".

If the valve is installed in the wrong direction, the water flow will increase the closing force and bush the black valve ball against the orifice (that is supposed to be the inlet) against the outlet of the valve. This will increase the "water hammer" effect. The first thing to do is to inspect the valve to see if it is installed in the proper direction of flow (note the arrow on the valve body)
If that is in the wrong direction, you have found the problem and you need to correct it.

If the valve is in the proper direction, then the flow is higher than the valve can handle properly and an easy fix is to remove one of the springs that provide the closing force for the valve. If that solves the problem then you are finished.
If the noise from "Water Hammer" stops... but the valve fails to stay closed, then the spring is needed to keep the valve closed. My guess is the circulator is too powerful for the system and a redesign is in order. For most systems that have 5 zones or less and utilize a B&G 100 or equal circulator... or... a 4 zone or less system with a Taco 007F or equal circulator, you will find the Honeywell valve is just fine.

Respectfully Submitted
Mr.Ed

Jamie Hall

Thanks, @EdTheHeaterMan . Looking at that Honeywell valve, I can see some very interesting hydrodynamics going on in there... as several of you all have noted, flow velocity is going to play a big part here. If the velocity is high enough, under certain conditions I think it's going to actually pull that ball shut, oddly enough (you wouldn't think so...) we see the same kind of problem on big cone valves (think needle valve on steroids!) which have to actively restrained in the last part of their closing stroke.

Much to think about here. Keep it coming!

Gsmith

I know from reading your posts Jamie, that you know the theory. You might try working out some examples of pressure rise in typical hydronic systems. Say a Taco 007 at mid range flow on the curve of about 10 gum, pumping in a mid size pipe of say 1”. The pressure rises are typically pretty reasonable, say less than 100 psi, unless the pipe lengths are a lot over 100 feet and the valve closing time is shorter than 1/2 second. Seems like in typical cases the pressure rise should be within the capabilities of typical system components, except in rare cases (very short valve closure times, very long pipe lengths, very high velocities). So probably the most common problems are noise and banging from the delta P. But, I have very little hands on knowledge of hydronic systems and the common effects of water hammer, other than the annoying but not damaging types.

Ironman

This has been our favorite for years. It’s a simple ball valve that can accept flow in either direction.

hot_rod

It’s all about a quick close against a high flow velocity. Hydraulic shock is the technical term. I did some research a while back as it is also a cause of intermittent backflow spitting

one other cause of some brands of zv hammer is the spring inertia winds into the motor. After the valve closes off it bounces two or three times before it rests. That bounce can cause the hammer. I have a video of a super slow motion camera capturing that bounce. Certainly it can be engineered out, slow closing valves for example.
one brand:) has a lost motion gear that disconnects that  spring inertia from the motor, removing that Flywheel” bounce potential

mattmia2

I installed one honeywell valve and several of the taco valve. i like everything about that taco valve much better than the honeywell. The power head just pops off if you push in a little wire clip vs the honewell where you have to remove screws to remove the powerhead. The wiring uses phoenix connectors which are much easier to wire than the screw terminals or the flying leads of the honeywell, they can be unplugged if you need to remove the powerhead altogether or you want to swap powerheads for troubleshooting and they are very easy to make a neat connection to. It is also a ball valve so it has a huge CV.

mattmia2

BTW, I prefer to use the npt version and adapters that way you don't end up cooking about a $75 valve if something goes awry or you end up having to rework it for some reason.

GW

hmmm I've soldered hundreds and have yet to learn of any getting cooked. Grab the 50-50. We call it the shifty 50.

ChrisJ

I've watched some interesting videos on hammering in both steam and water lines.

In steam lines it's the steam condensing and creating a vacuum suddenly, I'm sure many here are very familiar with the behavior. In water lines I think it's a mixture of things. The first being the weight of the water stopping too fast. I also believe it can create a vapor pocket on the downstream side of the valve causing something similar to steam hammer, or cavitation in a pump.

Jamie Hall

I suppose, @Gary Smith , that you are right. I probably should get out the old texts and do the math... it's been a while. Wonder where I put those...?

But I'm learning a lot -- no surprise there -- and thanks! Keep it coming!

pecmsg

Jamie Hall said:

pecmsg said:

@Jamie Hall
Those zone valves are Ball Valves

But -- if a ball valve closes quickly enough, it can slam. So how is the closing rate controlled? Is it?

Power open Spring Close.

its 2-3 seconds closing

hot_rod

Ball valves tend to cut or shear the flow off, the valves in our industry seem to be power close, and not an immediate, or split second closure.

Fast acting solenoids or spring return where you close the door quickly,tend to be more the issue, in the hydronic systems we generally talk about here.

Steam hammer and hammer in large water distribution piping is predicted and analyzed with water hammer or surge software, typically more of a civil engineers realm.

I think some of the hammer noise experienced in residential hydronics is the lack of adequate and proper tube or pipe restraint.