Variable orifice traps

[taffcad]

We are thinking of starting to use variable orifice type steam traps from a company called GEM trap (Gardner Energy Management). Uses would be for drip legs, flash vessels, and variety of heater batteries. The principle of operation seems very interesting and with no moving parts a guarantee for 10 years is given. They promote an improved energy efficeincy of between 15 to 40% and with no maintenance required it seems an attractive proposition. Any feedback would be appreciated.

 

[katmar]

TaffCad,

A long time ago I worked in a chemical factory where these traps were installed as part of a major energy saving drive. Overall, the project was a failure, but I don't believe it was because of the traps themselves.

I hope we are talking of the same type of traps. Ours were not "variable orifice" traps. The orifice dimensions were fixed, but tapered (or actually stepped).

The reason our project failed was that the representative did not really understand what he was selling, and our project manager was an electrical engineer who did not understand steam. The result was that they decided these traps were the answer to every problem, and they ended up installing them in unsuitable applications (as well as applications where they worked well). Also, many of the traps were undersized because our people did not know what the actual loads were. Traditional traps (floats, buckets etc) have a large margin of safety in them and the user does not have to specify them very accurately.

I believe that orifice traps are ideal in many applications, but I have struggled to get them installed because many operating people have seen similar problems to what I experienced a long time ago, and they flat out refuse to have them.

Part of the problem (IMHO) is the way the manufacturers describe their operation. They put the descriptions in "non technical" words which don't truly reflect what is happening and I think this puts off engineers who have the ability to understand the true mechanisms because the description smacks of "black magic". In the manufacturers' literature you will find statements like "condensate is 1000 times more dense than steam". This is true at 10 PSIG, but at 150 PSIG the ratio is only 150. Steam engineers know this, and are put off by the "misleading" statement when actually they should not be because the 150 ratio might be sufficient to get the trap to work well in their application.

In the days of steam ships, simple plate orifice traps were sometimes used by the US Navy because they were cheap, reliable and unaffected by movement (vibration and/or pitching). Stepped orifices are better than plate orifices because they have higher capacity on cold condensate than on hot condensate and this is important during start-up.

I am sorry that I have made this into a long story. I would suggest that you give them a try, keeping the following in mind

1. Avoid applications with widely varying loads.
2. Try to calculate or measure the load as accurately as possible.
3. If in doubt use a bigger rather than a smaller trap. You can change it later if it blows too much steam.
4. Take start-up loads into account
5. Remember that short duration peak loads on controlled streams (eg steam to a reboiler) can easily vary 25% above the average value.

Please give us some feedback once you have installed them.

regards
Katmar

 

[katmar]

One more thing - do not expect 40% savings unless your current traps are in very bad condition and you have a huge plume of steam permanently over your plant.

 

[hacksaw]

if they only last 10 years, then why install them?

 

[TBP]

taffcad - How are the proposed saving to be measured? Very few plants have any kind of meaningful steam metering in place. Without a baseline, any savings dangled from the proposed project will be all theoretical calculations, filled with assumptions.