Sonic Sound in the NH3 plant

[smpsmp45]

One of our customers has Three Plate freezers & TWO Blast freezers with about 500 KW capacity plant. IT also has Pumpen pumps.

Out of that Plate freezers are generally not used.

When the plant is started in the morning, there is a sound in the system.

The operator is closing the Suction valves & the Liquid Line valves of the Freezer units.

Can opening of the suction valves of the Plate freezers help is reducing this noise?

[US Iceman]

What does the noise sound like?

[smpsmp45]

Difficult to exlain. But it is like a explosion & infact It can be heard at a long distance.

It eventually dies down once the plant becomes operational for @ 15 minutes.

[nh3wizard]

Sorta sounds like a CK2 closing, just a guess

[US Iceman]

It seems like you may be experiencing what we call water hammer. I know it's not water, but you see the same thing in plumbing systems.

If liquid is suddenly accelerated by a sudden inflow of the vapor or other liquid very quickly, the liquid is propelled down the pipe until it hits an elbow, valve, or control valve. This causes the liquid to suddenly decelerate and slam into the component. This creates a shock wave in the liquid that bounces back and forth.

If the gas lines are opened first, then the liquid valves opened VERY slowly, the problem may disappear.

[kelvin_27_84]

Yes I agree with Iceman, it is water hammering especially if the PF is not always use, the NH3 just get stuck in between. another way I believe it will work is creating a bypass, and also have a EVRA (danfoss) open at 25%, let it bleed through in that way you can still open at normal speed. Just curious, doesn't it build pressure inside when the plant is turn off? if so do you have and valve to relieve what is left inside the PF each time it is switch off? or do you do a full pump down?

[smpsmp45]

The client is doing a full pump down before closing the system. But at the same time, we shall try out what US ICEman has suggested.

[Tycho]

Could it be that since the platefreezers are not in use they have filled up with liquid, and when the system is started and the LP is going down the OFV valves on the platefreezers start opening and closing *bang bang bang bang* because the LP is gradually going down and they are at the balance point of being open?


Try keeping the suction valves on the platefreezers open and the liquid valves closed when you start the system.

[smpsmp45]

Hi Tycho,

That is what we guess must be happening & hence have asked the client to open up the suction valves. Next week We shall know what is happening.

[smpsmp45]

On site, they have opened up the suction valves for all the plate freezers & for last week or so there is no sound now.

[Tycho]

On site, they have opened up the suction valves for all the plate freezers & for last week or so there is no sound now.

Good show

[Magoo]

I am pleased I and family do not live close to the plant, because something will break soon, and people will be hurt. You should have really good insurance cover, is my best call. Reminds me of that situation in India when a squillion people were snuffed out while a sleep.
magoo

[US Iceman]

Reminds me of that situation in India when a squillion people were snuffed out while a sleep.

I'm assuming you are relating this to the incident at Bhopal, India? That was a completely unrelated terrible accident that occurred due to a breakdown in instrumented safety systems, if I recall.

On the other hand, one of the results of this incident was the better development of safety and operating procedures to ensure something like this did not happen again. So...as a result I can see the similarity if you consider the facility being discussed here has written operating procedures (and the people are trained to follow them) to prevent an accidental release of refrigerant or someone getting hurt (or worse).

[smpsmp45]

I had read one artcile long time back on accidents after liquid line valves were shut off somewheer in USA.

I shall try & find that out & post it in the forum.

[Magoo]

US Iceman, you are the perfect gentleman and general nice guy. You seemed to have missed my safety relationship point. Generally a sonic bang is a relief covering someones brain fade factor. Keep up the good work, I love this site, for the experience and multi- problem sorting thing.
Magoo

[Magoo]

US Iceman, Magoo again.

Having just returned from a project in China. The safety thing there is paramount, people are so safety oriented it is frustrating. Every decision is by committee, long and protracted.
India, on the other hand is the rising star in this Asian region, only a bee's **** behind Chins. there safety standards are seriously miles behind China, and the rest of the world.
So it is no wonder that the Western world cannot compete commercially, we are on a mission to no were.

The US / everywhere/ economy doesnt stand a chance/ sorry. but that is the reality. Hope you all have a plan "B "
Check out the cost of petrol,/gasoline here in NZ it is now the equivelent of US$8.00 a us gallon [4 /litres /usgal].
Service calls by push bike.
China's cost per liter NZ$1.20, subsidized by Gov't to boost economy and infustrcture. Gov't excess trading deficite last year, 300 trillion US , so how as got it right or wrong

regards Magoo

Magoo the doom merchent

[US Iceman]

Hi Magoo.

You last post almost brought me to tears.

What you have said on the safety aspects is true of course. Safety is one of those topics that are cross-disciplined. Engineers and designers have to make the system fool-proof and provide adequate design precautions to cover ANY situation. That's the reason for the HAZOP reviews being done before the system design is finalized. This is where those sonic bangs should be addressed...

Then we have the operations part. If the people are not trained on well written operating procedures then of course anything can happen.

Most of the horrific incidents were for chemical and refinery plants. All of the safety guidelines that came out of that were in my opinion somewhat reasonable to be used for ammonia refrigeration systems. Unfortunately though, a lot of people want to go back to the good ol' days because they think it's cheaper or less aggravation.