What is the difference between "Hunting" and "Hunching"?

Hunch, when you think you know what the answer is. Hunching may possibly mean using your experience to solve a problem. Just a guess.

Regards JD.

Hi idretired, Thanks for your response. I'm pretty sure they were talking about a technical term. We were discussing the difference between a valve "Chattering" and a valve "Hanching". I'm pretty sure he was talking about valve hunting, but when I looked into it, I read that there was something called "Hunching Phenomenon". I know what "chattering" is, and am pretty comfortable with what "valve hunting" means, but I'm uneducated about the "Hunching Phenomenon". I'd like to more about that...

http://www.patentstorm.us/patents/6389809-description.html - (sorry, link no longer available)

The main change-over valve is switched between a large volume position and a small volume position in accordance with a pilot pressure (load pressure) which is fed through the pilot valve, allowing a pilot pressure receiving area to be changed between the large and small volume positions to prevent the occurrence of hunching at the time of switching from one to another volume.
More particularly, when the hydraulic motor volume is switched from a small to a large volume, the load pressure tends to decrease, so there is a fear that the motor volume may be switched again from the large to the small volume as the load pressure decreases. The load pressure increases upon switching of the motor volume to the small volume, so that the motor volume is again switched from the small to the large volume. Thus, what is called hunching phenomenon occurs.
According to the foregoing conventional construction, for preventing the occurrence of such a hunching phenomenon, the pilot pressure receiving area of the main change-over valve is varied between the large volume position and the small volume position to impart, for example, such a hysteresis characteristic as shown in FIG. 5 which will be described later to a set value of the pilot pressure (load pressure) for changing the motor volume.

Perhaps this will help, Regards JD.

Hi JD, I had a look at that too. Do you think that sounds a bit like valve hunting too?? I thought so when I read it... Regards, Sean

I think your friend was using the word 'hunch' to mean guessing.

"I'm 'guessing' or 'hunching' that the problem is . . . "

Using the word 'hunch' this way is somewhat unorthodox. This is the first time I'm seeing it.

Hope this helps.

Orpheuse

You should have asked your colleague on the spot.

One word has many meanings, both technical & non tecxhnical, you may never know what he was really referrirng to.

I regret a lot about my past for not being curious & quick enough to ask questions.

Good Point. I went into his office and asked him this morning. He said "Hanching...Isn't that English???" I said it sounded English but could be Hunting or Hunching. He asked me what the difference between them was!!!

In my opinion hunting is oscillation about the desired state, and, is normally caused by not damping the feedback (critically). There seem to be several Japanese sites where they have used the word hunching instead of hunting:-

http://www.ntcl.co.jp/en/products/motor/

The flow control valve mounted in this thermostat is helpful for prevention of hunching(unstable situation of water temperature repeating up-and-down behavior under certain temperature control) and accordingly the durability of engines improves.

Another meaning to hunch is to bend or bulge, and sometimes in hydraulic lines you can get a chatter, I had it caused by a hydraulic pump pressure controlled by a shut off valve that closed when pressure was needed and excess pressure released thought a relief valve, this causes the lines to bend and distort and make a noisy racket. Maybe this is what he is referring to, the flexibility in the pipe lines?

Regards JD.

Hi, SeaninJapan!

It would appear from the responses that there are two distinct and unrelated phenomena called "hunting" and "hunching".

Hunting is a regulatory response swing where there is an incomplete feedback loop, as so beautifully expressed by Randall, "In my opinion hunting is oscillation about the desired state, and, is normally caused by not damping the feedback."

And hunching is an hydraulic term that describes the sudden buildup of pressures/fluid delivery [loading] during change over in the system due to pilot valve limitations in assisting diminishing fluid access through a valve, as illustrated by JDRetired, in the part that reads, "The load pressure increases upon switching of the motor volume to the small volume, so that the motor volume is again switched from the small to the large volume. Thus, what is called hunching phenomenon occurs."

JDRetired goes on to say that he has witnessed hydraulic system 'chatter' as a predicatble result of hunching. Water hammer could conceivably be a result of stop/start liquid delivery in an oscillating (hunting) system where the variance in flow-through is under-controlled.

The similarity seems to end at the end-result of system noise, since the causes for each are not the same, although both result from a monitoring deficiency.

Mark

Hi Mark,

We make the valves for water systems in buildings and plants. When the Japanese engineers are talking to me it's very important that I understand what they are talking about, but I must admit that sometimes I don't due to language troubles. In the interest of not getting bogged down, we carry on with the meeting and I usually talk to them about it later. So I really appreciate your and everyone else's responses. During this discussion we were talking about pressure reducing valves. I'm was pretty sure that he was talking about valve hunting. The valve we were talking about was a pilot-operated pressure reducing valve without flanges. He mentioned that the pilot reacts quickly to differences in inlet pressure, but the main valve is slower. Sometimes the pilot tells the main valve to close, but before it completely closes, the inlet pressure is changed, causing the pilot to open the main valve. This repeated oscillation is valve hunting.

I've become interested in hunching now. He didn't seem very aware of what hunching was. So, in your opinion, hunching can cause water hammering?

Hi, SeaninJapan!

No, I don't think hunching has anything to do with water hammer. Hunching is a visible line stuttering phenomenon due to a flow restriction. Hammer is a loud sound caused by change of pressure energy to sound energy.

JDRetired indicates hunching is an hydraulic line phenomenon. The changeover from the large-flow valve to the minor-flow valve necessitated the overall flow rate be self-down-adjusted to accommodate the smaller motor; and it caused, as I understand it, a temporary backing up of hydraulic fluid/pressure. The greater flow had been used to drive a larger motor. It was restricted before the smaller motor and a sudden series of releases was the pilot before the smaller motor accommodating itself to even out the flow of the greater throughput. The lines magnified this "chatter" under the stop/start of flow until an even flow was established.

While a pilot valve is a control mechanism, its function is that of a 'feeler', not a controller which monitors and predicts flows at lightening speed to maintain a level or constant flow.

Water hammer in an oscillating system is a loud bang or series of bangs caused by the shock waves of a (suddenly) interrupted flow where there is no release for the pressure wave that sudden interruption builds up; and it may also be caused by air/cavitation in the piping where suddenly release of fluid, [in certain unique cases by an unregulated, swinging, or "hunting" controller because it cannot keep pace with the demand/release of the system's fluid requirements,] into an empty space bangs into a valve or a full pipe.

Mark

haha, growing up in the South, I had to laugh at all of the different quesses about hunching. Here "hunch" is a slang term for movement during sex, so it could be somewhat like a water hammer or other "banging" in the pipes

"Here "hunch" is a slang term for movement during sex,..."

Is that N. Carolina only? I've always heard it called "hump", or "humping".

It maybe the same difference as between "RICE" and "LICE"

(Just soking....)

Wangito