Steam Blowout Target 2

[BronYrAur]

I have been asked to install a 6" blow out line for a 250 psi steam line that will be powering a turbine. The purpose is to blow out any slag in this temporary blow off line. basically, it will be a 6" line with a gate valve that will vent outside for a couple days worth of testing.

I need to install a "target," but I am not sure what that is or how to install it. I am told that it is basically a soft metal like aluminum that will be inserted in the center of the pipe during the blow off. then the metal will be inspected for damage as an indicator of how much slag is in the pipe.

I have 6" pipe. How would I mount such a target? how big should it be? I was thinking on putting 3" thread-o-lets on opposite sides on the 6" pipe. That way I would have 3" openings through which the targets could be inserted and removed, but how would they be supported? I thought of welding a rectangular plate to a plug that would go into one of the thread-o-lets. Then the aluminum could be bolted to the plate. Don't know.....spitballing here.

Any thoughts?

 

[LittleInch]

Jesus.

So you're going to be blowing unknow sizes and amounts of hard, sharp metal at god knows what velocity into somewhere?

Why?

And why do you even want to guess at how much comes out?

There is no such thing as temporary piping and I usually delete this word as it gets you into a poor way of thinking "It's ok it's only temporary..." I've seen many "temporary things be still there years later patched together. NO. design it like it will always be there.

A central "target will miss most of the slag running along the bottom and what is the purpose? Targets just tell you something hard hit it. Not how often.

A big bit will just destroy it.

I would urge you to step back and think this thing through a bit more. IMHO.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[BronYrAur]

That's why I'm asking. Not my turbine.....I am not running the steam piping to it. I am only being asked to install this blow off piping for a 2-day test, and then the piping will be removed. The purpose is to blow out the crap before connecting to the turbine.

 

[pmover]

to supplement LI post, i'm thinking something like a cyclone separator that is mounted in boiler steam drums. this would allow the "slag" material to fall out and allow steam to vent to atmosphere. however, this cyclone separator does not have a "target" per se. the "slag" material will collect in base of cyclone separator.

i would think this activity should have been done at commissioning.

 

[LittleInch]

How bigs the main line?

What's the velocity in the main steam line when you're busy sending slag into orbit?

What's the velocity i[pre][/pre]n your 6" line?

And why does anyone actually care how much slag is in there? Or are they trying to see when it's "clean"?



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Heaviside1925]

OP,
I would talk to the contractor doing the steam blow, they should be able to provide you with what they need for their targets. They should also be able to give you the planned rates for the blows so you can make sure the piping can handle the loading. The one's I have been involves with the contractor has a checklist/requirement (I think some standard detail drawings as well) of what they need and if you have questions, they've done enough of them, they should be able to provide you with answers.

 

[BronYrAur]

I believe the main is 6" - same as the blow off. Don't know velocities. They want me to put an increaser and short run of larger pipe on the end to reduce velocity and hopefully noise. Planning to transition up to 14" for the discharge. There will be no silencer. I was able to get a little more info from them, so I think I'm ok. I appreciate the help.

 

[Heaviside1925]

OP,
They may be waiting for the final piping design to provide published velocities, but they should be able to provide you with preliminary/unofficial values for you to complete your design within a margin of safety.

 

[KevinNZ]

The target bar and requirements to pass the purge test are usually provided by the supplier or owner of the turbine,
for example
1. target bar - copper
2. test flow and steam velocity is a factor (disturbance factor) above the turbine operating steam flow
3. Expose the bar to the steam for XX minutes (the bar can be in holder that allows the bar to rotate to face the steam flow)
4. scars allowed to pass the test. Say per cm2, no more that one scar >1mm. no more than 5 scars >.25mm.
5. more than one test with cooling between tests

 

[LittleInch]

You still need somewhere to vent the steam and all these bits of metal shooting out...

But a bar would seem like a good method even if the pass mark is a bit empirical...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[georgeverghese]

How about what is commonly called a target T-piece ? Gas flows up to the piping tee, and gas takes a sharp bend to one run out of the tee, while solids, because of solid particles higher momentum, will hit the blinded end of the tee. So the blind is the target.

 

[LittleInch]

George,

might be a good way of measuring total dirt, but the idea of those so called target tees is to get the particles to slow down at the last minute before running into the blind flange and not continue down the side branch.

But for sure you need to get some more information form whoever is asking for this as to what exactly are you measuring and how often des it need checking or renewing and does it need to be done whilst still venting and blowing it all through or can they shut down, retrieve the target, install another one and then start up again.

This does all seem a little bit "basic" though....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[MJCronin]

There are specialty Contractors to do this kind of theing ... It is not wise for Plant Mangers to assign this task to someone who has never done it before .... to someone who has never seen a blow-off target.

There are multiple "steam blows" required, each will require a "target" ... There are established acceptance guidelines that will tell you when you are done .... This can take a long time and hold up other people trying to get work done

But your MBA boss never told you all this when he hired you a short time ago ?.... No ???

I assume that you are 20-something and have little experience with steam systems

Google the string "steam blow MJCronin target" .... tell us what you find out

LI, as always, puts his finger on the salient issues ...

Your thoughts ??

MJCronin
Sr. Process Engineer

 

[Heaviside1925]

OP,
I hope you are not in the situation MJCronin is mentioning and if you are I would take strong notice of the everyone's advice and cautionary notes as they are speaking for their experience.
I will speak from my experience, and it may or may not be relevant to yours. A few firms I have worked for dealt almost exclusively with petro-chem clients. There seemed to be a period of time (may still be going) where the plant's boiler houses were nearing the end of their lifecycles. A few of clients opted for installing CHPs because the bean counters said it made sense. None of our clients had experience with CHPs nor did my firm who was supporting the projects for our clients (ISBL/OSBL sort of projects). I was involved with the design of the temporary piping system for steam blows as required by the CHP engineering firm and specialty contractor for the steam blows. The requirements of the steam blows, as noted by KevinNZ were likely driven by the turbine owner but also noted, are typically dictated by established acceptance guidelines. My firm and I relied heavily on the advice and guidance of the CHP engineering firm and specialty contractor since this is not something we had done before. This is not something you want to "engineer" yourself. Ask a lot of questions, ask for examples. In my experience the CHP firm and specialty contractors were used to working with firm and customers without prior CHP experience and were all excellent in communicating and providing the information needed to move the project forward. I hope you are in a like situation but if this is something that was "dropped" or "forgotten until the last" and is now in your lap, understand this is not a typical activity and you likely do not have the required experienced for it.

 

[MJCronin]

Superb, Heaviside1925 ... KUDOS for good advice !!

I hope you are in a like situation but if this is something that was "dropped" or "forgotten until the last" and is now in your lap, understand this is not a typical activity and you likely do not have the required experienced for it.

Lets see what happens ... but ...

This is the point in the timeline where we never hear from the OP again ....

https://www.steamforum.com/steamforum_tree.asp?master=1856

Comments from any experienced people ?...... Anyone ??

MJCronin
Sr. Process Engineer

 

[mk3223]

To contact the steam blow service contractor who is specialty in cleaning the steam pipe as needed such as turbine piping.
He will review your steam piping layout, and provide you the proper piping route for testing, the required orifice size for the proper steam flow rate, temporary connecting spools and silencer for blowing test in the job site, etc. You are to buy the pieces of the polished brass targets (about 1”W x 10”L) for testing.

 

[shvet]

How would I mount such a target?

is it what you are looking for?

9.4 Cleanliness criteria
They depend upon the final use of the pipe or the vessel. Compressor's suction lines for instance, have to be far cleaner than drains.
The main criteria are:
• Color of the cloud at the air outlet
At the beginning of the blowing, the cloud is brown (rust colour); it becomes brighter and brighter as long as the blowing lasts.
• Color of a blank fixed perpendicularly to the flow at the outlet:
An aluminum plate or galvanised metal plate is generally used. After the first blowing, the plate colour is brown/gray, due to the multiple impacts. The colour becomes brighter and brighter after each further blowing. (The plate has to be changed after each blowing).
• Number of impacts on a standard plate
When lines have to be very well cleaned (lines upstream a turbine, for example), a plate is placed on a "tail pipe", and the number of impacts (see an example of standard plate in figure C) are counted after 3 minutes of blowing.
10. Cleaning with steam
... The advantage is the embrittlement of rust, scale, welding slag, etc., created by this change of temperature.
The steam blowing shall begin by a slow rise of temperature to allow for thermal expansion of the system (don't forget to drain the condensates at every low point). When the steam temperature is roughly reached in the pipe, allow the steam to flow at a rate calculated for the velocity given in section 9.2.2. At the end of the steam blowing (after 5 min to 15 min), the cleanliness shall be checked according to section 9.4. If another blowing operation is necessary, let the network cool first (take care of the thermal expansion, and prevent it from vacuum, drain all low points); the cooling time may be reduced by blowing air through the system.
When the cleanliness of the pipe meets the requirements, let the system cool down; drain all low points and, if necessary, dry the network and reassemble (see section 14).

also relevant instructions can be found in

https://www.academia.edu/11621145/Piping_and_Vessels_Flushing_and_Cleaning_Procedure

 

[BronYrAur]

Thanks all for your input......even you MJCronin, in spite of your arrogance! People come to this forum for help. You could offer help without being rude.

I have been involved with HVAC steam piping for almost 30 years, but I have never been involved with piping a turbine. In fact, I am not even piping the turbine now. I have just been asked to pipe the blow out line, which strikes me as odd. Not sure I want to be part of it for that reason.