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New Venturi Orifice Steam Trap

11/10/2011 8:40 AM

We have recently installed a new design venturi orifice steam trap to a steam system at a customer with very good results. We have previously been in a discussion on this forum regarding these type of traps with some very negative comments about them.

Is there anyone else out there that has tried these types of steam traps? I would love to hear about your experiences. Our customer has seen some very good savings based on controlled measuring. The project included the replacement of all main steam traps as well as all process heat exchangers and cooking pots. The heat exchangers were running with a control valve modulating the steam flow and the cooking pots were manual open / close only.

It was decided that 6 months prior to and 6 months after the project, no other changes would be made to the steam system so that an accurate before and after comparison could be done. After the six months of measuring were completed after the traps were fitted the feedback was that a 18% boiler fuel saving was achieved, heat exchanger applications are performing very well with zero water hammer on the system and with an 8% improvement in reaching temperature on the process. The cooking pot applications are all reaching temperature satisfactorily with no noticeable improvement but also no worse than before.

We are going to be looking into this for further findings but are very encouraged by the results as we have been a bit sceptical regarding these traps.

As I mentioned before, feedback or other experiences would be greatly appreciated.

BEFORE AND AFTER

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#1

Re: New Venturi Orifice Steam Trap

11/10/2011 10:40 AM

I can't directly comment to your particular modifications, however, having done heat rate and efficiency calculations for years I think I can offer some good info.

1) Be very wary of how these "before and after" calculations are done. With regards to plant parameters and ambient conditions, no two points in time are the ever the same - even when the tests are done in the same day. A true before and after type test needs to correct for all of these differences. More often than not, "improved efficiencies" can be shown to be nothing more than changes in ambient conditions, fuel quality, or normal plant operational variations.

2) Be VERY wary of the calculations that are put in front of you. I once analyzed a plant that had a modification done to improve efficiency. The proposal (the purpose and theory behind) for the modification was convincing to the engineers (and they were engineers) who signed off on it. The calculations were all correct!! There was no room to argue with them... however there was lots of room to argue with what they DIDN'T calculate. The problem was, the calculations weren't for the entire process, just one part of the system. It was a simple case of robbing Peter to pay Paul, so to speak... plus the "interest" charges that normally come with any type of energy conversion/transfer... the end result was they were actually less efficient (and paid to install the modification and a bonus to the guy who came up with the idea).

3) Efficiency isn't always the goal. The quick and dirty of this is... would you let me modify your car to get 200 mpg IF the restriction were placed on it that you could only travel 5mph? From an investor's or manager's view, sometimes being more efficient means LESS profit so it isn't desired.

4) Most modifications will at best show small improvements to the bottom line. I'd question an 18% fuel savings as much as I'd question someone if they told me they could sell me "free energy". My experience and instinct tells me that it doesn't happen (the system already had some type of steam traps and even if these were all non-functional I doubt you'd realize an 18% fuel savings). (The best way to save upwards of 18% of the fuel usage is to reduce the loading 18%!)

If you're the sales guy, I don't buy it. If you are one of the plant workers, be VERY wary, it doesn't smell right to me.

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#3
In reply to #1

Re: New Venturi Orifice Steam Trap

11/10/2011 11:23 AM

Not to mention the condition of the steam, are they returning condensate back to the boiler, are there any contaminates such as proteins in the return condensate.

Also what type of improvements did they have? using less steam? Boiler stopped tripping?

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#2

Re: New Venturi Orifice Steam Trap

11/10/2011 11:10 AM

Never worked with that, here is some good info, orifice type traps.

And have worked with traps before, I'm sure your familiar with Armstrong which does have a good site, but in case not, check link above.

It good the customer is happy.

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#4

Re: New Venturi Orifice Steam Trap

11/10/2011 11:40 AM

I suppose I could also offer that based on my experience orifice type steam traps work fine and have low maintenance.

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#5

Re: New Venturi Orifice Steam Trap

11/11/2011 8:18 AM

The 2 pictures do not look as if the installation was on the same site exactly (i.e. the same outlet!).

Also, what is that square box? Looks like another steam trap in line ...?

To compare efficiencies, at least check like to like on the same line and the same equipment.

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#6
In reply to #5

Re: New Venturi Orifice Steam Trap

11/11/2011 8:31 AM

You are correct in noticing that the pictures are not from exactly the same positions. It was not relevant to anything other than to show what the trap set looked like before and after.

The 'square box' is a very expensive Spirax Sarco ST171 25mm Spiratec Chamber. It is a product that Spirax sell to be installed after a steam trap. An even more expensive Spitatec hand held tester is then used to dock with the chamber when you want to test the traps. It basically measures conductivity. The problem with them is that the sensor inside scales up over a short period of time rendering them useless.

As far as the comparisons go, this was measured accross the complete system and not just individual traps.

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#7

Re: New Venturi Orifice Steam Trap

11/11/2011 9:03 AM

Old system: wye strainer (installed up-side-down), mystery box (water separator?), process trap (float type).

New system: mystery box (water separator?), thermodynamic trap with integrated wye strainer (Spirax Sarco?).

18% makes me weary. Also, the six month split in testing. Was that Summer to Winter?

BTW, is that a liquid to air heat exchanger with the cooling fins all beat to hell?

In my experience there is a time and application for orifice type traps (freeze protection, steam tracing). Ultimately they are just slow leaks into your condensate system. I would NEVER use them on process exchangers. So, installing them across the board in the entire plant and getting 18% boiler fuel savings?? Fishy fishy.

-A-

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#8
In reply to #7

Re: New Venturi Orifice Steam Trap

11/11/2011 9:26 AM

I guess it is human nature to jump to conclusions looking for faults in something instead of asking questions and finding possible positives in something.

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#9
In reply to #8

Re: New Venturi Orifice Steam Trap

11/11/2011 9:49 AM

I don't see my statement as "finding faults." I posted many, many questions. And, I stated my doubts as to the veracity of your claims based on the incredibly high fuel savings.

In my post I included instances where I thought an orifice type trap would be useful.

It is possible that the system was running SO poorly to begin with that the installation of orifice type traps was a significant improvement. Just as installing new tires on a car that previously had none is a performance improvement.

An orifice trap is a hole. A venturi type orifice trap is a fancy hole. They do not adjust to ambient temperature changes or changes in load. When there is condensate present, they allow your steam pressure to push that condensate to the condensate return header. When there is no condensate present, they blow live steam to the condensate return header.

Their greatest redeeming feature is that they are amazingly cheap to manufacture and therefore return an incredibly high profit to whoever is selling them.

Please help me with my ignorance and answer the questions in my first post. Firstly, why does you venturi type steam "trap" look like a Spirax Sarco TD42?

-A-

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#10
In reply to #9

Re: New Venturi Orifice Steam Trap

11/12/2011 5:47 AM

The line at the end of your sign off says "Question Everything" which I guess is probably not a bad idea when there is so much information being thrown at us these days and also bold savings statements like the 18% saving I mentioned. I was probably being a bit defensive about this.

OK, so yes I am the manufacturer. We are a very small company based at the tip of Africa in Cape Town, South Africa. We have spent 2 years developing our new DSV model alongside a local oil refinery's R&D department after they performed a 3 year trial on our previous model to determine suitability to their system. We presented the new design to them and over the 2 year period we got to the point where they were satisfied with the new design, results and performance of our model on their steam tracer systems. They are in the process of replacing all TD main line and thermostatic tracer traps with our DSV venturi orifice traps. They have not yet begun testing our venturi orifice traps on their process applications as they are wanting to finish the roll out on all main line and tracer traps first. We will probably begin process testing in 2013 with their energy research team.

As you can see from the picture below, we have designed the body to be almost identical to a standard TD trap to make replacing the old TD traps easier. The bodies are cast 316L stainless steel and not simply machined from bar stock. That is where the similarities stop. The internals have a removable venturi orifice insert and a dual strainer system. Traps can be screwed, welded or flanged into a line and maintenance can be performed on them without having to remove them from the line by simply opening the top and bottom caps. Maintenance on these traps should be minimal but there is always the chance of a strainer blocking or even the orifice and this is why it is NB to have access to these parts. Orifice blocking is minimal though but can happen. We have fitted thousands of main line orifice traps with very few instances of blocking. We have registered a full international patent on this design. I would give you the link to our website but do not know if I that is acceptable for this forum as it may be seen as advertising.

Summer winter conditions are important to take into consideration when looking at comparative figures but having said that, the temperature difference in Durban, South Africa between summer and winter are so small that it would make very little difference on the results. The before and after information was based on kg of product manufactured against kg of steam produced. Boiler hotwell temperatures were monitored and maintained, boiler fuel quality was monitored, boiler was cleaned before start of both monitoring periods and all systems were kept the same throughout the testing period.

We were not involved in the evaluating or monitoring process and only supplied the equipment and were given the final results.

The condition of the old mechanical float and thermodynamic traps was poor and there is no doubt that they were wasting steam and in need of replacement before the trial but I think one positive that comes from this is that it clearly shows how poorly a mechanical trap will work over time especially when compared to a venturi orifice trap which have shown result over the last 10 - 12 years of not having widened orifices and not ever blowing steam through even on varying load conditions where a control valve is in place.

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#11
In reply to #10

Re: New Venturi Orifice Steam Trap

11/14/2011 11:52 AM

Thank you Steam, for a thoughtful and detailed reply.

Everything in your reply is consistent with my experiences. I understand and appreciate your savings numbers now that you have explained the before and after conditions.

Also of note, is the fact that the replacements were done on steam tracing lines and that TS and TD traps were replaced. This is also consistent with my experiences and original post.

I have never been to SA, and I am surprised to hear of the near constant temperatures given it's southern latitude. I have friends from Africa who say SA is a fantastic place to be. I think I should like to go someday.

This sounds like an exciting project and I would love the opportunity to argue with you until the wee hours over the data and details. But alas, from this distance I can only say, "Best of luck, my friend!"

-A-

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#12

Re: New Venturi Orifice Steam Trap

11/15/2011 3:06 AM

It was very prudent that you had the Spiratec chamber removed because it would most certainly register a "leaking trap" signal when the venturi blows steam at low load - unless it is so undersized that there is always condensate backing-up into the coil

Yes, these things are great where one can accept condensate-logging and where the loads are consistent. Even though ambient changes would result in fluctuating loads, product tracing lines are nevertheless a good application for this technology. But, if processing times need to be as fast as possible and if one requires precise and rapid control of process temperature, a true modulating steam trap (which provides an immediate controlled interface between steam and condensate) needs to be used.

We can all appreciate "Steam"'s enthusiasm in trying to expand the market for his wares. However, in doing so, he risks sullying the reputation of a fine product which is suitable for a particular application by trying to position it as an alternative in applications where it's not.

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#13

Re: New Venturi Orifice Steam Trap

11/15/2011 6:04 AM

Besides for the fact that we are manufacturers of these traps, I am in no way trying to market on this forum. I find the discussion interesting and believe it is an opportunity for us all to debate a very 'hot' topic wrt steam trapping.

Let us for a minute ignore steam tracing and main line drainage applications and any other constant load application and look at varying load process applications.
A reputable make ball float steam trap is an excellent product and works exceptionally well when fitted to this kind of application. There main downfall is that they do, over a period of time (normally years but sometimes even over days or weeks) fail open and waste massive amounts of steam or fail closed and waterlog the steam system. When these traps fail closed it is normally picked up very quickly due to product temperatures not being achieved but when they fail open it is not normally noticed straight away and this ends up not only costing money but can also affect the rest of the system through back pressure, etc.

A venturi orifice steam trap on a process application with a varying load and modulating control valve in place WILL perform as well as a new ball flaot steam trap and continue to perform like this for many years to come without any problems. Venturi orifice traps on process applications do not fail closed as there are no moving parts like a ball float to collapse and drop and the orifice is not really small enough to plug unless the system is in a very poor state but in that case all traps would plug.
The orifice traps will also not pass massive amounts of steam, contrary to popular belief.

The following is an excerpt from an article we published regarding the working of our traps over a varying load:

"The final condition is if an application that has a control valve, that is regulating the flow of steam to a unit. Below is a model of the function of a Delta steam trap operating on a heat exchanger.

The model simulates a heat exchanger (with a10m2 surface area heating water from 20OC to 80OC). It shows how the change in the flash steam varies as the flow rate of water to be heated, varies.

FULL LOAD

PART LOAD

LOW LOAD

Water Flow Rate

37 700 kg/hr

30 371 kg/hr

18 900 kg/hr

Energy Required

2 639 kW

2 126 kW

1 323 kW

Steam Flow Rate

4 750 kg/hr @ 10 bar

3 675 kg/hr @ 5 bar

2 165 kg/hr @ 1 bar

Flash Steam Generated

16%

11%

4%

Flash Steam Flow

760 kg/hr

408 kg/hr

83 kg/hr

As less condensate arrives at the trap there is less pressure forcing it through the orifice, but because the temperature of the condensate has reduced, there is less flash steam generated. The percentage of flash steam drops and the mass flow reduces.

The reduction in the flash steam being generated means that there is less back pressure generated so even though there is less pressure forcing the condensate through the orifice of the trap, there is less back pressure holding it back.

The nett result of all this is that as the process conditions change the capacity of the DELTA Trap changes accordingly.

The output characteristic curve of a heat exchanger is not linear, but a curve which starts at the maximum condition (maximum flow and maximum pressure) and regulates down to zero as the control valve closes completely.

The capacity of the DELTA Trap is a function of the orifice size and the dimensions of the venturi section. By utilising the natural laws of physics, i.e. the change in the amount flash steam with change in pressure, the capacity of the DELTA Trap can vary with the changes in process conditions. The internal dimensions of the DELTA Trap are designed in such a way that the capacity of the DELTA Trap changes with the changing capacity of the application."

Perhaps this will help shed some light on the workings of these kinds of traps.

Lastly, if you are still sceptical about our claims and have access to a site where there is an application you want to test this on let me know and I will send you a trap at no charge to try this on. There are very simple comparative measuring methods that can be used which I can supply you to check and agree on. The condition of us supplying the trap would be that you would give us a letter stating your findings and confirming or dismissing our claims that we will post on this forum and perhaps our website.
Let me know.

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