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dreamz
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SWAS Sampling Line To Determine Dosing

07/27/2016 4:26 AM

The discharge of CEP is being dosed with ammonia and hydrazine. To measure the amount of dosing and get the required quality of water to HRSG, sample for SWAS is taken and is analysed.

Their is one school of thought which says that the SWAS sample of the condensate, should be taken from upstream as well as downstream of the dosing line connections. This is necessary to understand the amount of dosing necessary, and the subsequent quality of water after dosing.

Another school of thought is that once we know the amount of dosing to be done then, it is not required to take a sample downstream of the dosing connection.

Note: Here, upstream of dosing could be from the condenser hotwell and downstream of dosing could be from the LP drum.

Which is the best method out of the both? Is it essential to take samples from both the locations?
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Pathfinder Tags: CEP Chemical Dosing Sampling System SWAS
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Randall
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#1

Re: SWAS sampling line to determine dosing

07/27/2016 5:49 AM

CRIMINAL

I've got "Steam and Water Analysis System", and, "Heat Recovery Steam Generator", but can't figure out "CEP".

When you're talking to people in your industry (and country) you can probably get away without defining your terms or describing what you're talking about. But clearly the answers you're looking for are not readily available amongst your peers and colleagues. If you're asking for opinions from a wider range of people from different disciplines it's better to expand your acronyms and explain in more detail what you're asking about.

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JPool
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#2
In reply to #1

Re: SWAS sampling line to determine dosing

07/27/2016 9:10 AM

possibly Condensate Extraction Pump? Just a WAG.

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SolarEagle
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#3
In reply to #2

Re: SWAS sampling line to determine dosing

07/27/2016 11:17 AM

Maybe Cation Exchange Plant.....To the OP...Using acronym's is fine, but they should be used with definition when using for the first time in an exchange...This is an international forum that deals with every engineering discipline from every angle imaginable....We could take time to probably work out what you mean, but why should we? Clarity is needed for speed, our time is valuable....

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#4
In reply to #1

Re: SWAS sampling line to determine dosing

07/27/2016 12:09 PM

GA

Eschew obfuscation

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dreamz
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#5

Re: SWAS Sampling Line To Determine Dosing

07/27/2016 1:14 PM

Sorry for everyone's confusion and being a criminal
By CEP I mean Condensate extraction pump..
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James Stewart
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#7
In reply to #5

Re: SWAS Sampling Line To Determine Dosing

07/27/2016 4:07 PM

In our combined cycle unit, we do sample both the upstream water (hot-well) and the downstream (economizer inlet in our case). We are not using hydrazine and ammonia.

We have brass condenser tubes from legacy equipment, and ammonia is just too corrosive on that. Morpholine works better for our application.

As to hydrazine, I would caution strongly, since this is a known carcinogen, inhalation toxin, etc. Carbohydrazide is used in place of hydrazine, and breaks down in steam conditions to hydrazine, same problems with the decomposition of hydrazine leading to ammonia under certain conditions.

We are using Methyl Ethyl Ketoxime with excellent results. I do not know who supplies this in your country. Solenis supplies a 10% solution of this in the United States. Actually, with MEKO, the iron oxide formed in the boiler system is more of a purplish red color (when ORP (oxidation-reduction potential) is maintained between -50 and -150 mV (absolute). The purplish red oxide adhers to the metal with a very thin coating, forms an effective barrier against rapid pitting damage during upsets, and does not throw a lot of corrosion product into sample lines, making analysis easier. Other products we used in the past were bad about black color throw during unit start up. MEKO is a very safe product to use, and if you overtreat with it, about all that will happen is a cleaning of the steam turbine blading.

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Randall
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#6

Re: SWAS Sampling Line To Determine Dosing

07/27/2016 2:21 PM

There's a technical note from ABB here:-

https://library.e.abb.com/public/fda218a411cf3f8dc12569580054c7aa/3_do_hyd.pdf

which describes several monitoring points and why they are important.

I suspect that you are far better qualified to judge the quality of the document.

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lyn
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#8

Re: SWAS Sampling Line To Determine Dosing

07/27/2016 5:30 PM

Sample the stream at the point where chemical balance is most critical to the process, or to the equipment.

In my case, that was always just before the newly dosed solution was introduced into the process stream.

The down side of this is that if you have a long stream/slow turn-over process stream, your water may be out of tolerance for a longer time.

It's all up to you.
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Mikerho
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#9

Re: SWAS Sampling Line To Determine Dosing

07/27/2016 10:36 PM

How confident are you in the consistency of the composition of condensate? If you are SURE that its composition doesn't change, there is no reason to sample before dosing.

On the other hand, what happens if there is something in the system that causes the composition of the condensate to change? Your post-dosing sample may then be out of spec and you will not know if the dosing was wrong or the composition of the condensate was out of normal.

How much does it actually cost to do both?

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Crabtree
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#11
In reply to #9

Re: SWAS Sampling Line To Determine Dosing

07/28/2016 8:25 AM

"SURE"? I hate abbreviations. :-[

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James Stewart
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#14
In reply to #9

Re: SWAS Sampling Line To Determine Dosing

07/28/2016 4:46 PM

The key point you brought up is about something changing the chemistry of the condensate. Answer: yes, something is always changing the composition of the condensate at levels that result in enhanced corrosivity if left untreated. To better understand (and track changes) in these systems, usually the two sampling points are required. We want to know if there is a condenser leak for example, we want to know just how much non-condensible loading there is in the hot-well below the condenser.

Non-condensibles are carbon dioxide, oxygen, nitrogen, and possibly other gases, including ammonia (can come from breakdown of hydrazine). Usually these all enter the system on the vacuum side through small leaks in gaskets, seal rings, pump seals, etc. Sometimes, they arise from gross boiler leakage by the shear volume of make-up water pulled into the system with little or no de-gassing.

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dreamz
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#15
In reply to #14

Re: SWAS Sampling Line To Determine Dosing

07/29/2016 5:32 AM

Mr. Stewart,

Thank you for your reply.

What I have observed after discussions with many project teams is that, EPC (Engineering Procurement Construction) contractor tries reduce cost and hence gives takes sampling only at one point. While the owner may demand for sampling from both the points. However, the best method is to take sampling from both the points to suitably control the amount of dosing and the quality of teh CEP water.
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dreamz
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#16
In reply to #9

Re: SWAS Sampling Line To Determine Dosing

07/29/2016 5:36 AM

Mikerho,

You are right that it depends on the consistency of the condensate. But then, without measurement the consistency cannot be known. Hence, I think it is compusory to take a sampe before dosing. This will let us know the amount that we need to dose.
Whether to take a sample after the dosing could be avoided since it would act as a safegaurd. We can be totally sure that the condensate after dosing has achieved its required quality.
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HiTekRedNek
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#10

Re: SWAS Sampling Line To Determine Dosing

07/28/2016 4:45 AM

YLA?

IGYA!

HT?:

GAS 2U!

DQMOT, BSF IDK WCA 2TXT W/LOA.

IYO, ITS EZ &PDQ... IDTS.

IMHO, ARE =ADIH. TBH, FUBAR &2M2H. GIAR, PLZ! KISS.

.02

RX

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HiTekRedNek
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#12
In reply to #10

Re: SWAS Sampling Line To Determine Dosing

07/28/2016 1:52 PM

Translation for #10:

Translation:

You like acronyms?

I'll give you acronyms!

How's this?:

Greetings and Salutations to you!

Don't quote me on this, but seriously folks I don't know who cares anyway to text with lists of acronyms.

In your opinion, its easy and pretty darn quick... I don't think so.

In my humble opinion, an acronym rich environment is another day in hell. To be honest. its *fouled* up beyond all recognition and too much to handle. Give it a rest, please! Keep it simple, stupid.

Just my two cents.

Regards,HTRN

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redfred
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#13
In reply to #12

Re: SWAS Sampling Line To Determine Dosing

07/28/2016 3:32 PM

CRIMINAL is much more elegant, IMHO.

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Crabtree (1); dreamz (3); HiTekRedNek (2); James Stewart (2); JPool (1); lyn (1); Mikerho (1); Randall (2); redfred (2); SolarEagle (1)

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