How can a trap that has a fixed diameter orifice with no moving parts operate on applications with a variable load?
There are typically three conditions that cause variation in condensate load:
- Start up load: On indirect heating applications, the volume of condensate is much larger at the beginning of the cycle. Because in this condition the condensate is much cooler the venturi trap can discharge 2 to 3 times the operating load during start up.
- Varying steam pressure: Condensate load is typically a product of differential pressure. Heating processes are normally controlled through a modulating valve. In steam systems pressure is directly proportional to temperature. Higher temperatures require higher differential pressures. The flow rate through an orifice is logarithmically proportional to this differential pressure and the orifice diameter. Simply stated the higher the temperature, the higher the pressure differential, the larger the condensate load but the higher the capacity of a fixed orifice to pass large condensate volumes.
- Varying heat load: In some applications, the condensate volume is not controlled by varying the steam pressure but by changing the product required to be heated. A typical example is a shell and tube heater which could have multiple product cycles. At a constant differential steam pressure, it may heat a fluid which has a specific heat capacity in one batch and a different specific heat capacity for the next batch. If the process time is the same for both processes, there will be a difference in condensate load but the differential steam pressure remains the same. The ECOFLOW venturi orifice steam trap system incorporates an orifice and venturi section (as the name implies). This gives the steam trap a range. Starting from the maximum physical flow rate (determined by the orifice diameter) down to a minimum point where the orifice is oversized and some steam leakage occurs. This range is known as the ‘turn down ratio’ and applies to the orifice diameter at a constant pressure. University studies and practical field tests have shown zero steam leakage down to 20% of maximum flow. Giving the steam trap an 80% range of zero steam leakage at a constant differential steam pressure.
Don’t orifice traps block easier than conventional mechanical traps?
Blockages are caused by particles in the steam system. If water treatment or pipework material selection increase the incidence of particulate in the steam system then there is a probability for blockages. This probability exists in equal measure with mechanical traps which have many small and complicated parts. The ECOFLOW Venturi trap is fitted with a filter. For highly contaminated systems it is possible to fit a second filter. In practice blockages are no more or no less likely to occur than if mechanical steam traps were fitted.
Can I use them on all the applications that mechanical traps may be used?
Yes they can be used in all applications, with the exception of traps used for overflow applications on the bottom of flash vessels or as vacuum breakers.
Don’t they continuously lose steam in operation?
No in simple terms, it’s because of the physical properties of steam and condensate. Condensate it 1000 times more dense that steam. Steam cannot pass through a film of condensate. When the orifice is completely saturated no steam can pass and therefore there is no steam loss.
What happens over time does the orifice wear and the traps begin to leak excessive amounts of steam?
In practice when steam is present in any system there will be losses causing condensate to form. Once a drop of condensate is formed in the orifice, no steam can come into contact with the nozzle surface. The very aggressive steam phase therefore cannot wear the orifice. It is simply condensate (very hot treated water) in contact with stainless steel.
They are expensive to buy surely this makes them un-economic to install?
This is all too often the “buyers” argument. It is important to distinguish between the buy price and the cost of capital equipment. Typically mechanical steam traps have a working life of about two to five years at best. Our ECOFLOW venturi orifice trap comes with a ten year performance guarantee. This alone means that you would buy two or three conventional mechanical traps in the same time period. During the working lifetime the mechanical traps can lose the entire buy price in steam losses in a single year. This could effectively mean the equivalent of buying four or five mechanical steam traps for every ECOFLOW venturi orifice trap purchased over a ten year period.
They do not operate any better than my conventional mechanical traps so why bother?
ECOFLOW venturi orifice steam traps have a different operating principle to mechanical steam traps. They discharge continuously when condensate is present using the difference in density between steam and condensate. Operating in about 70 – 80 % of the total working range of the trap. Often mechanical steam traps are many times oversized for the specific application. Sometime only operating at 10% of the working range of the trap. All too frequently “as long as the plant runs” is a mantra that hides inefficiencies and poor efficiency of steam operating plant. Assessing steam trap performance is extremely difficult with most testing simply a review of ‘pass’ or ‘failure’ and little knowledge of the actual efficiency of the system.