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Vacuum Dropped Alert!!!

The entire week have been an interesting. Besides my routine job, I learned and experienced new things. However, I will share only the following 3 stuffs.


Vacuum dropped due to wet steam

I hate this case!!! When vacuum pressure dropped, the quality of oil is affected and most of the time the oil have to be rejected. In this case, vacuum dropped occurred because of wet steam. Wet steam is basically water carry over from boiler. Boiler is supposed to produce steam and deliver it to plant. When boiler began sending steam + water to the plant (which is not suppose to happen), the vacuum system is interrupted. The vacuum lost its capability to suck fatty acid which is supposed to be removed from the oil. I could not let it happen again. I don't want my plant to reject oil again because of this 'typical' reason. The boiler people never want to admit that they sent steam + water to the plant.

Therefore, I decided to investigate the case further. Few minutes after the 3rd incident ocurred (wet steam) I took a bottle of condensate water sample (this is the condensed steam which became hot water) and tested its TDS (total dissolved solid). We tested the TDS using a digital TDS meter at the boiler house. The TDS of the sample showed 70 ppm. Normal condensate water should display reading less than 10 ppm. This implied that water carry over (wet steam) happened. Why? Because, steam is water (H2O) at 120 ++oC temperature (around 15-17 bar). Hence the boiler is/should only send steam (pure H2O). Pure H2O should have zero or very minimum content of metal/solids/substance inside it. When steam condensed and became condensate water, the content of metal/solids/substance should remain. However, when wet steam occurs (due to water level fluctuation inside the boiler), some water follows the steam to the plant. The water is chemically treated and this increased its TDS. Therefore, if the condensed water is 'rich' of TDS, this confirms that wet steam is taking place.

Up to today, I gathered 2 condensate water samples (as proof) after the wet steam incident and the TDS result is very high!!! The boiler people definitely have to do something to avoid this from worsening or happening again. I'm not accusing anybody to be responsible of the "oil rejection". I sincerely just want to solve the problem. Save cost and time as well.


Checking the Total Dissolved Solid (TDS) at different temperature

When I first checked the condensate water sample which was collected by my supervisor, it showed TDS of 67 ppm. The boilerman said, that is impossible. He claimed that my sample was very cold (I left the sample in my office for about 5 hours before testing it. Therefore the air condition has cooled down the condensate water temperature to about 24-27oC). That's fine....I told him, let's heat the same sample up to 65-70oC and repeat the TDS test. We heated up the sample and re-tested the sample at 65oC. The sample showed reading around 70ppm. At least, it's close the the earlier TDS reading. Before repeating the TDS test, I told the boilerman that TDS have nothing to do with temperature. However, he stubbornly claimed that temperature influenced the TDS reading. After that he kept quiet and admitted that temperature have nothing to do with TDS. Hence, the condensate water really have high TDS which means water carry over (wet steam).

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posted by zaki yamani @ 12:05 AM,

6 Comments:

At Monday, June 25, 2007, Blogger Webworm said...

Steam saturation temperature at 15-17 bar is about 200 degC...Should not be 120 degC...Severe condensation in steam header is expected. Severe condensate in steam line and limited steam trap capacity will lead to condensate accumualtion and carry over into steam tap off point. This further result vacuum device performance drop...Check your steam header insulation...or you can check make up...probably increased.

Scale inhibitor injects into boiler to remove scale, TSS, TDS, etc...check if your scale inhibitor injection is work correctly...

Good luck...

 
At Monday, June 25, 2007, Blogger zaki said...

Thanks for your comment.
Sorry, the boiler can go up to 15-17 bar. But we just produce about 14 bar...That is about 195oC. The steam going to plant is not as high as that. The temperature gauge in the plant steam header shows something like 130-150oC.

Insulation and steam traps are OK. The only problem is the boiler is running high fire all the time to cope and maintain at 14 bar. It's a small boiler (A). The main boiler (B)is under maintenance. Sometimes, the water inside the boiler fluctuates....and send water to the plant. We can see this when our vacuum drops and the pressure gauge vibrates heavily....

Chemical is fine too...The other boiler (C) sending steam to other plant and location is not having that problem. It's basically the problem in boiler A....

 
At Thursday, July 19, 2007, Blogger owais123 said...

I m wokring as a chemical engineer in
GamaLux OleoChemical, Fat Splitting Unit.We r facing the same problem our main boiler is under maintainance and smaller one in progress time and again vacuum drop and our production get effected but when we don't have good vacuum then we hold the plant or
lower down the feed input and product out put but the main problem is that if we lower down the product Fatty acid flow rate then it get chance to stuck in the pipeline then we have to flush the line which is more troublesome. What will u suggest me about how to solve the problem

 
At Wednesday, August 08, 2007, Anonymous Vinay said...

I am working in a textile plant as a maintenance engineer. my steam requirement is abt 5500 kgs/hr. The main line from boiler to header is 4 inch. can a smaller pipeline size will lead to water carryover. we maintain tds level in boiler of abt 4000-4500. ours is a water tube boiler.

 
At Friday, October 12, 2007, Blogger Chai said...

I can solve your TDS problems. TDS is always an issue in boilers and also in Cooling towers. For years we have been trapped by the tradition of addressing this issue with chemicals and of course of late some expensive alternatives. ANalytical SOlutions Sdn Bhd Malaysia sells a tremendous solution for this. The chemical has anti corrosion properties and not only that it resolves the problems of scaling. It is used by many factories already . The problems why this chemical is facing resistance is not because it does not work but the fact it may make many in existence and existing engagements redundant. If you want to know more about this chemical by all means call me ( CHAIYO) on my mobile +60 12 3302084 Malaysia or write to John Mc Williams (john@analytical-online.com)

 
At Thursday, October 18, 2007, Blogger zaki said...

Thanks Chai,

Really appreciate it.

 

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The Author

zyz

I’m Zaki. I used to be a project, process and chemical engineer. Few years ago I successfully became a Chartered Engineer (IChemE) and Professional Engineer (BEM). I'm now employed as a chemical engineering educator/researcher/consultant. Hope you like reading my blog. I welcome any feedback from you. My email: zaki.yz[alias]gmail.com. TQ!


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