Marine Boilers and Water Washing

[SailorPhil]

I need some help with Boiler Safety Valve regulations. Does anyone know the value at which to set a boiler safety relief valve? like xx% or something?

Also I would like to know what oil water washing is. I've come across this question in an exam and need to know why water washing of oil is undesirable. Any info that can be passed on?

Many Thanks.

 

[jme1976]

SailorPhil,

Try Warsash maritime college, all the lecturers there are Class 1 Chief's and very up to date with reg's and code's etc. If they don't know, which is unlikely, they will find out!

+44 (0) 1489 576 161

http://www.solent.ac.uk/wmc

(I could give you a few names but not sure on the legal aspect of it over a forum.)

J


Motor yacht Engineer

http://www.jonathanevered.com

 

[jme1976]

Better still -

http://www.warsashcentre.co.uk

Motor yacht Engineer

http://www.jonathanevered.com

 

[TEOMECH]

Hi......
As much as i know the class (Lloyds,ABS,DNV,GL,BV,etc)approves the safety valves opening pressure.
And this pressure it is normally equivalent to the design pressure + a margin of 0,03%.
So the design pressure of each boiler is always stamped at the name plate and also mentioned at its instruction manual.
As far as i know there is not such a rule for closing pressure of safety valves but normally it is at the 85% - 90% of the design pressure
I would be pleased if you give me mores details about the oil water washing...because i have something in my mind...but not sure...

 

[SailorPhil]

jme1976 Thanks for the link! TEOMECH - I don't have any more information other than giving you the whole question from the exam: "Explain why the water washing of oil is undesirable" (from what I can remember!)

 

[TEOMECH]

Just there was an old engineering tip to water wash the M/E sytem oil (crosshead engines) while the latter contaminated by cylinder oil.
Water washing use to be performed while water droplets mixed in a small amounts with system oil after the purifier.
Of course as far as i know this is undesirable, beacause the compositions of oils have changed so no results can be achieved.
So,old techniques many times cannot meet the advanced technology......
That was in my mind....
Hope to answer your questions...

 

[SailorPhil]

That's awesome teomech! I got an email yesterday from an old instructor of mine saying that water washing is used to remove acids from the oil. I found an article on google from a refinery stating that they use water washing to remove salts that are carried by and not dissolved by the oil.

Thanks for the info!

 

[BrianBT]

Safety valve settings- 3% above approved boiler working pressure. The valve must close (blowdown) at 5% below setting although they tend to be set at 3% to prevent excessive water loss


Water washing of lube oils- This practice has stopped as it removed the water soluble additives in the oil.

Water washing of fule oils - I have seen this is practice in shore based facilities but not marine. It was being used to remove sodium due to concerns on sodium-vanadium slagging corrosion.

 

[baldski]

To Sailor Phil:

Boiler Safety valve settings have to take in account if the boiler is equipped with a superheater. Normally you will find two drum safety valves and one superheater safety. The superheater safety has to open first to ensure flow thru the superheater, hence, it will be set lower than the drum valves. A 900 psi boiler might have a superheater set at 950 psi and the drum valves at 1040 and 1050.

Atlantic Refining tried water washing bunker fuel to remove ash and other impurities aboard their tankers. I do not know the results.