Water Main Surge Relief Valve 2

[ivanlocke]

I am looking for information/manufacturers of surge relief valves to relieve water hammer from a 60" water main. Probably an 8" or 12" valve. I've tried searching the internet, but haven't been able to find anything specific to large water mains.
Thanks for any help.

 

[bimr]

Try contacting Cla-val. They specialize in that area and make all types of controls and valves for that industry.

 

[BobPE]

you are going to need to design more than one for that large of a main in surge anticipation mode.

BobPE

 

[epbpe]

There are numerous manufacturers of control valves; including: Cla-Val Compnay, Newport Beach, CA., Golden Anderson Co., Mars, PA., Ross Valve, Troy, NY, and Bermad Company, Anaheim, CA. All of these companies manufacturer surge and pressure relief valves. It is imperative that you understand which type of valve you need. A pressure relief valve is designed to relieve high pressure only while a surge relief valve is intended to relieve both low and high pressure surges and waves. You should never use a surge valve on a water system without elevated water storage because the valve will often not close following a low pressure wave. And, don't forget to use proper air relief valves since most pressure surges are the result of some type of sir entrapment. In any case, all of the manufacturers listed can provide you with guidance on which valve to use.

 

[stanier]

If one wants a more sophisticated rapid acting unit the petroleum industry normally uses Mokveld or daniel type valves.

A formal waterhammer study shouldbe used to size the devices.

The maximum velocity recommended through these valves is 12 m/s. The larger the unit the lower the maximum recommended velocity. Sharing knowledge is a way to immortality

 

[ivanlocke]

Thank you for all the replies.

I was just told to start looking into surge relief valves, but I have now received more detailed information that we want a relief valve for the case of overall high pressure of the system (in case one of the valves from a high pressure to low pressure zone fails to respond) - so a pressure relief valve instead of surge relief valve.

I have been told that these valves are high maintenence. From what I've seen on manufactures websites are just annual visual and pressure checks. Have any of you had any experience one way or another?

Thanks

 

[epbpe]

The surge anticipator valves (surge relief) are indeed high maintenance valves due to the multiple pilots and complex piping. A surge anticipator valve normally will include: 1- high pressure pilot, 1- low pressure pilot, 1- flow limiter (to restrict amount of main valve opening), 1- control pilot valve, 1- strainer/needle valve assy., opening and closing speed controls, and numerous other cocks, copper tubing, and fittings. The initial adjustment and maintenance of the adjustment is critical for proper response and operation of the valve. A pressure relief valve, on the other hand, will generally only have a high pressure pilot, speed controls, and control pilot for pilot control over the main valve. Adjustment is much simpler to initially perform and maintain than a surge valve. As I mentioned in my previous post, a surge valve in the wrong application is often worse than using no valve at all. Make sure that your system has adequate supply and pressure to reclose the valve after the initial low pressure wave, otherwise the valve might remain open and never close because the pressure cannot recover enough to reset the pilot system. Hope this helps, epbpe.

 

[BobPE]

edbpe:

The valves are quite complicated as you indicate, however, they are not used too frequently if the system works right!!! The valves must be looked at and cycled to make sure they are operational, but they usually dont need much replacement maintenance and are very reliable.

I am a little confused though from you posts, these valves work by the anticipation of a surge which is the high pressure wave arrival at the pump station. A transient starts with the low pressure wave upon pump shutoff at which time the vlves are closed as not to let air into the system which could magnify the problems. Prior to arrival of the high pressre positive wave, the valves open to waste water and reference the high pressure wave to atmosphere. These valves do nothing for this low pressure wave. If you want to control the negative or low pressure wave, a surge tank design will have to be placed into service.

Usually, the anticipation function of the valve is done using a regular low tech timer that opens the valve a pre determined period of time after pump shut down...

BobPE

 

[epbpe]

BobPE; The surge anticipator valve I refer to is the pilot controlled over hydraulically main style as made by Cla-Val, OCV, Ross, etc. Their pilot control system is designed to allow the main valve to begin to open during the initial low pressure wave that accompanies power failure of a pump or similiar failure mode. The name "anticipator" is derived from the fact that the valve is anticipating the returning high pressure wave by first sensing the initial low pressure wave and is already open when the higher pressure surge appears at the valve, thus exhausting this high pressure surge. As long as system pressure is above atmospheric, air will not be drawn into the system, even during the low pressure wave; and even if it is, it is almost always exhausted during just before the high pressure wave hits the main valve. The critical settings of this valve are the flow limiter (used to prevent the main valve from opening excessively and dropping pressure or even setting up a second water hammer event) and the low pressure pilot which must be set precisely to sense the low pressure surge but never try to open during normal low pressure operation in the system. As I mentioned before, I have used this valve for years and they work quite well, as long as the owner is willing to accept the additional maintenance and inherent risk that comes along with the valve. And, as I also indicated; engineers who use this type of valve on a system with limited capacity vs. head will regret it, the first time the valve opens on a low pressure condition and cannot close because the pressure will not rise high enough to reset the pilot and close the main valve. This is NOT the same type of valve as a surge relief type valve as manufactured by GA Industries among others. This type of valve uses pressure sensitive springs for direct valve control, a completely different concept, but one that works well for sewage pump stations where plugging of pilot supply water can be a factor, epbpe.

 

[BobPE]

edbpe:

yes I know the valve, they should not open on the low pressure wave. The timer that starts the valve operation is set based upon system characteristics. I too have designed them into systems for years, albeit larger systems where mistakes of misdesign cannot be tolerated.

You are right though, transient wave propogation does not allow large volumes of water to move into or out of the pipe, but very small amounts do move in and out as a function of the wave pressure. Opening the surge anticipation valve on the low pressure wave will allo a movement into the pipe possibly magnifying the affects of the transient.

I have seen transient cycles from a single event last for minutes making several dozen cycles to dampen, its a crazy pehnomea.

BobPE

 

[epbpe]

In all of my limited experience I have never seen any type of timer connected to a pilot controlled hydraulic control valve, such as a Cla-Val model 52-03 surge anticipator valve. I do know the valves you are talking about, but that type of valve is not the style I am referring to. I don't intend to be argumentative, but the valves I refer to do indeed open during the low pressure wave, there is a pilot on the valve specifically intended for this function. These surges occur so rapidly that the valve almost must be opening during the low pressure wave before the high pressure wave returns to the valve. Admittedly, these valves can be dangerous if misapplied or oversized, but when an experienced designer knows what they are doing, these valves can relieve very high pressure surges, epbpe.

 

[bimr]

Why don't you fellows just answer the question. Relief valves are typically visually checked on daily or weekly system walkthroughs. Annual inspection would entail removal, recertification by an authorized repair facility and reinstallation.

 

[jh118]

Not to sound stupid, but why does opening the surge anticipation valve during a negative pressure wave exacerbate the downsurge?

I am working on a sewage pump station modification right now where they have surge anticipation valves. I need to make recommendations on their optimal timing and would like to undertand the rationale for why their premature opening causes problems. What is it about the air introduced that makes these things a problem?

It seems to me that they would act like a vacuum relief valve, except they are located in the pump station. Am I wrong?

 

[stanier]

These types of surge anticiaption valves, in my experience are not designed for sewage applications as the pilots become block with debris and biological growths.

I have recently come across the Charlatte range of hydraulic dampeners and in my modelling of rising mains give the necessary mitigation of transients on difficult pipelines. Has anyone in this forum experience of using these devices on raw sewage applications?

One downside is that they are registered pressure vessels and thus require the routine maintenance and inspections that go with such units.( This may be different outside Australia). Your responses please.

In regards to surge anticipation valves they do work however if soneone fiddles with the pilot regulators or they become comntaminated then transsients will not be mitigated. They should have the same status as a relief valve in that they are a safety device. Therefore should be tested frequently, be sealed upon setting and not be capable of isolation unless redundancy is provided.

I recently visited a site where such a device had been disconnected from the header because the operator had never seen it work and couldnt be bothered checking it.

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[hydrae]

Stanier
I will have a contractor install a set of them in the next couple of weeks where the air relief valves are regularly destroyed by collum separation. Will let you know.

Charlatte has been most helpful in evaulating and sizing the vessels.

Cannot get around the ASME code since it is not "just water"

Hydrae

 

[PUMPDESIGNER]

Got here late.
One presupposition that is not mentioned but important to know, the only possible way to help yourself is to act before the surge occurs by "anticipating" the surge. That is because a true surge or water hammer event moves much too fast for any known mechanical device to respond to, the speed of sound in water, 4,000 plus feet per second, which no valve made can possibly deal with.

Only other thing I got to say is that whoever suggested that the surge should be analyzed first is correct. Surge anticipators of any kind are not the best solution.

I always have a saying that is applicable here.
If you create a monster (surge) in the system, good luck trying to stop it.

Designing for a no pressure surge system is always superior to trying to respond to it once you have already created it.

PUMPDESIGNER

 

[PUMPDESIGNER]

Find the actual cause of the surge and deal with that if you can. I realize that some or all of the items below cannot be applied, but they are offered as suggestions to look at.
1. Fast closing valves can be changed to slow or linear closing valves.
2. Sequenced shut downs so that no long run of pipe experiences valve closures near the end of the pipe run. If a valve is closed near the end, open another valve up close by at the same time or just before valve closure.
3. Modify pipe systems by completing a loop, adding pipe.
4. Reduce flow rates.

There are many possibilities, but really they all deal with the same things: surge is an inertial problem created by mass moving at velocity. Reduce the mass, reduce the velocity, reduce the time of closure.
Be creative and always attempt to change something in the mass, velocity, time of closure.

I assumed that air was not involved, because air is a whole other issue.


PUMPDESIGNER

 

[Markmcad]

All surge relief, pressure relief, and air release valves are a maintenance concern and should be checked routinely. The fluid being conveyed, solids, grease, air, system characteristics, and other factors will drive the required maintenace effort. Sewage will create a situation where much more valve maintenance is needed than clean water. A reliable maintenance department equipped to perform the work is necessary. You can't get around this.

Evaluating the system conditions for selecting a pressure relief valve is easier than for surge. Going beyond the initial reaction to contact a valve rep is sometimes necessary, particularly for surge and in cases where damage to the pipe could develop. Pipeline collapse caused by negative pressures is a well documented problem. Computer numerical analysis software is available to evaluate the system for surge conditions. The Method of Characteristics is the numerical analysis used for surge conditions. Tullis, Univ of Utah has written books which focus on valves and transients; you may want to learn more on transient analysis from Wylie, Univ of Michigan, an authority on the application of the Method of Characteristics for hydraulic transients. Good Luck

 

[drain]

Having read the above, I now submit my scenario: Static head on the system is about 395 feet, which we're pumping (VFD) against to deliver water to a tank some 1.4 miles away. Using a GA Industries 4" surge relief valve, low velocity of 5 fps (1650 usgpm), to be set to discharge to waste. I'm going to set the valve to open at 10% higher than my system working pressure. I plan to set the surge relief valve to close just above my maximum static pressure to ensure I don't drain the tank. Does this sound reasonable? Any comments welcomed. Thanks.

 

[stanier]

You will likely end up with valve chatter. The system will have transients most likely above the 10% margin that you have set your relief valve at. The valve will unlikely not respond to any passing transient quickly enough to relieve surge but will be constantly opening and closing. You need to engage a professional to study your system.

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