Fixed Orifice vs. Venturi Technology Steam Traps
Steam traps have been around for over one hundred years to discharge condensates and non-condensable gases. Over the years engineers have designed new technology to effectively discharge condensates and non-condensable gases and contain live steam in their system. One relatively new technology is the Venturi style steam trap.
Venturi steam traps have no moving parts and operate by continuously removing condensate from the steam system. It allows any condensate present in the steam line to pass into the condensate return system as it is formed. The operation of the trap is based on the difference in density between water and steam. It is designed to handle varying loads of steam, and then self-regulates the capacity through the nozzle. With this new technology and the way it operate, it has been compared to a less effective technology which are Fixed Orifice style steam traps.
In this article, we discuss some misconceptions about Fixed Orifice steam traps and go through some FAQ on the large differences between the two technologies. After reading this you will understand how comparing Fixed Orifice steam traps to Venturi Technology is like comparing apples to oranges.
Fixed Orifice Steam Traps look like this:
The Delta Venturi Steam Trap looks like this:
FAQs
What are the main differences between Fixed Orifice Plate steam traps and Venturi technology steam traps?
The Venturi steam trap works differently to an orifice steam trap. The main feature is the venturi design after the tunnel orifice on the trap. Condensate flashes into steam in the mouth of the venturi, this flash steam acts like a plug to the less denser steam and allows the denser condensate through.
As the upstream load conditions change so does the point of flash steam change. The point of flashing moves closer to the mouth of the venturi and further away as the upstream conditions change (varying load) allowing the venturi steam trap to be able to regulate the condensate load without backing up condensate or leaking steam. This flash area is like a plug that moves in and out continuously as the upstream load changes, thereby allowing the venturi steam trap to easily handle varying loads.
Why is the Venturi technology a better design than Fixed Orifice?
A Fixed Orifice does not have a venturi after the orifice and therefore cannot use the flash steam as a moveable plug to handle varying loads.
A venturi steam trap has the venturi design after the tunnel orifice and therefore is able to use the high pressure zone flash steam to regulate the flow out of the steam trap.
Based on the design, why can Venturi Technology handle startup loads but Fixed Orifice steam traps cannot?
On start-up load the condensate is cold and passes through the venturi trap at 3 to 4 times the speed of running load. It does this because when it starts up the condensate is cold and has free flow through the trap. When the start-up condensate has been ejected and the hot condensate arrives and the system gets up to running load then the hot condensate starts to flash a percentage of the condensate back into steam.
The Venturi steam trap then uses this flash steam as a high pressure zone to restrict live steam but allow condensate through. Therefore the venturi steam trap is able to pass start-up load conditions as well as running load conditions.
Is waterlogging and corrosion an issue with Venturi Technology?
Waterlogging and corrosion is a problem for Fixed Orifice Plate Traps. The Venturi style steam trap is sized for maximum load and is able to handle the varying load, therefore they are not undersized to discharge running load and not start-up load. Venturi steam traps discharge start-up load without waterlogging and then using the flash steam plug at the mouth of the venturi are able to pass the reduced running load without leaking steam.
Conclusion
The Fixed Orifice style steam trap can only effectively drain condensate for a specific condensate flow condition, which means this type of trap cannot handle varying loads.
If the amount of condensate which needs to be discharged reduces, the localized back pressure from the flash steam expansion will not be present. The condensate plug will be reduced which will lead to live steam being lost. Conversely, if the condensate load exceeds the design flow for the orifice plate, then condensate will back up which may affect process temperatures or lead to waterhammer.
With Venturi technology, the flashing moves closer to the mouth of the venturi and further away as the upstream conditions change (varying load) allowing the Venturi style steam trap to be able to regulate the condensate load without backing up condensate or leaking steam. This flash area is like a plug that moves in and out continuously as the upstream load changes, thereby allowing the Venturi steam trap to easily handle varying loads.
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About The Author
Business Development – Process/MRO
Greg Bayerl is a Business Development Representative based in Buffalo, NY. He has been with the Peerless team for 6 years specializing in the MRO market.