Anti water hammer 1

[aladin5020]

Hi,
we are designing an offdshore firefighting network (using sea water). We have added an anti-water hammer to protect the network. I didn't found any product wich can be used in an offshore application.
would you please have any recommendation.

 

[cloa]

You can't just add anti-water hammer device- you need to evaluate your system as to the likelihood and nature of water hammer and if appropriate add the correct water hammer features. Try searching for water hammer on this forum first. What's special about off-shore other than perhaps needing 316 or a particular standard to meet?

 

[stanier]

First model your system. Then consider what devices will solve the challenge presents. Then model the system to ensure that the device will perform. The attached Powerpoint will give you some idea of what can be used. There are no devices I am aware of that cannot be used on an offshore rig. The main concern is space on a rig and large gas ccumulators may not be preferred.

“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King

http://waterhammer.hopout.com.au/

 

[aladin5020]

Thank you guys for your repplies. I cannot download the powerpoint file to explain more the system; we have a non pressurized firefighting network. We have a risk of water hammer when we close a valve since the pump is working.

 

[stanier]

If you are using a pump you have a pressurized system? Slow valve closing times is a legitimate way of mitigating surge. Without modeling the sysem you are guessing. The system designer should model the system for surge.

“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King

http://waterhammer.hopout.com.au/

 

[aladin5020]

The firefighting network is not under pressure when the pump is not working ( we didn't have jockey pump, hydrophore...)I think that we can use gate valve as a a slow closing valve.I have found this product but i don't think that it is suitable in this application:

http://www.solenoidvalvesuk.co/dynamicdata/data/docs/alf 2010.pdf

 

[stanier]

This a tiny gas accumulator and it is hard to see how it would work effectively. As I have said if you get a specialist waterhammer engineer to analyse your system the engineer will come up with a design that will work. This may only be the time to close the gate valve.

You also need to look at pump start up & trip as scenarios.

You can't guess these things. It has to be designed There will come a day when you need the firefighting system and it breaks because it hasnt been designed. The rig burns down, you lose your house, job, family and you go to jail.

“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King

http://waterhammer.hopout.com.au/

 

[LittleInch]

stanier - I think that's a bit dramatic - it wouldn't only be aladin5020's rsponsibility, but the general point is accepted, i.e. aladin, there are many times in life when you need to accept that you don't have the required skills and experience to do certain things and guessing or using sites like this to answer your basic design questions is simply wrong. Fire fighting systems need to work first time, every time and are a critical safety feature on an plant, but even more so offshore and need to be designed properly.

One of the contributory factors on the Piper Alpha disaster where 167 people died was that the fire water system had been turned to manual because the lift pump was contained in one leg of the platform and divers were working in close proximity and didn't want to get sucked up into the pumps if it went off automatically. Unfortunatley they didn't turn it back to auto and once the fire started, couldn't get to the switch to turn it back on. You don't want your fire fighting system to not work when it's needed....

See

http://www.theenergylibrary.com/node/13090

7pm, but also worth a re-read for all of us that work with offshore systems

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[Frank1344]

Hi Aladin5020,

Would you be able to provide more info on this anti-water hammer like vendor website,brand etc....

Can we use them in Industrial applications?

Thanks in advance,
Frank

 

[aladin5020]

We will not add an anti water hammer device we have designed all the system to avoid water hammer. thank you guys for your help and recommendations.

 

[stanier]

LittleInch,

Engineers in Australia have been charged with manslaughter where negligence was involved. Isnt there a charge of depraved indifference in the state of New York. A large tank constructor is a self insurer. it instructs its engineers that if they stray from compnay standards they will be personally liable.

Your attitude of sweeping such engineering responsibilities under the carpet and considering them to be "drammatic" is frankly very disturbing. Managers are good at ducking responsibilities and leaving the engineer to be hung out to dry.

“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King

http://waterhammer.hopout.com.au/

 

[LittleInch]

Stanier, I had no intention of sweeping engineering responsibility under the table and i accepted your general point. My point was that there should be quality rules in place such that one single engineer should not be in the position of making errors that cause such a catastrophe.

Companies and individuals can be liable for negligent design, but there really should be procedures in place to prevent individuals from making such errors. It is when those procedures aren't applied or used properly which is when things happen. Your example of a tank constructor is the one that would worry me. Clearly if you go outside company procedures you can be fitted, but procedures should be in place to prevent those actions from becoming reality and causing accidents and incidents.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[stanier]

Littleinch,

We dont all have the luxury of a bureaucracy controlling our every action. Australia was built by engineers who have to design with little back up after a facility has been built and handed over. Engineers have to be smart enough to know when they are out of their depth and get professional help. They are required by their code of ethics to only practice in their field of competence. But sometimes they are on their own when it comes to resources. Asking the boss for $30k to do a study is frowned upon.

Many organisations in Asia have the same problems. In this isntance we are talking about a fire protection system on an existing rig. The original design will likely have been by a major engineering company. Then it is left to the cash strapped maintenance crew to keep it running and modify it.

Many a time I have had to fix up a system that just didnt work. But then I dont have anyone checking my work. But I know when I cannot service my clients as things are outside may area of competence. I have also seen drawing & specifications with 6 signatures and the content is wrong.

As for negligence there are plenty of lawyers out there that will get you off the hook.

Let me give you an example. A specification lists every standard local and international with the "hope" that a product will be fit for purpose. Thrown into the specification is the term "good engineering practice". The lawyer will point to the ignorant spec author the common law "contra preferentum " applying.

http://en.wikipedia.org/wiki/Contra_proferentem.

Then will explain that "good engineering practice" is a nice to have but doesnt actually mean anything in law. Enginneering documents have so much garbage in them that it is easy to avoid responsibility. Engineers are generally poorly trained when it comes to legal matters.

“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King

http://waterhammer.hopout.com.au/

 

[LittleInch]

Stanier

I totally agree with you. If you read my post carefully, I think (hope) I made exactly the same points about engineers needing to know when they don't know enough. I've also been in situations where I know that what ever I designed or specificed wasn't in reality going to be scrutinised or checked properly or at all and it didn't make me very comfortable, but at that point I knew what I was doing. My point was that I don't think that is at all acceptbale, especially where critical situations are present and lives are at risk, such as the fire fighting network on a rig that we were talking about.

Hope I have explained my position a little better and that we can now leave it there?

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way