Following the steam curve is the key to efficient steam trap performance. Utilizing dual thermostatic/ thermodynamic forces allows Bestobell Steam delta traps to match the steam curve. This means that the energy in the steam is efficiently used by your process, and not wasted in the operation of the steam trap.

Initial System Start-Up
On initial start-up of the steam system, large amounts of cold condensate and air are present in the system. At this point, the bimetallic strip of the delta element relaxes and fully opens the valve assembly to quickly expel the high volume of non-condensable gases and cold condensate through the discharge port.

Thermostatic Forces for Tight Shutoff
As the element senses an increase in the condensate temperature, the bimetal expands and raises the stem to modulate flow. Just below the temperature of saturated steam, the seat will close tightly to prevent live steam from discharging.

Conversely, lower temperature condensate relaxes the bimetal, allowing the valve to open. With this valve opening, the system differential pressure acts on the diameter of the plug, which increases the force of the opening to allow faster and heavier condensate discharge capacity.

Thermodynamic Forces
As high pressure condensate is discharged to a lower pressure variable (either atmospheric or a pressurized condensate return system), thermodynamic forces develop. These forces are introduced via a three stage orifice that contains an expansion chamber that is formed between the seat and skirt of the valve stem. The controlled pressure drop through the second stage orifice into the expansion chamber, and the resulting intermediate pressure, creates an opening force that increases hot discharge capacity. It also results in only a small percentage of the total pressure drop occurring at the valve seat, which significantly reduces wear.

Controlling Flash Steam Provides Higher Discharge Capacities
As the temperature of the condensate increases, the element assembly acts to modulate the flow. As hot condensate is discharged, a portion of it flashes back to steam, and attempts to occupy a space much larger than it would as condensate. The controlled generation of flash steam within the expansion chamber enhances the pressure forces acting on the diameter of the plug to increase hot discharge capacity.

No Live Steam Loss
As the temperature of the condensate nears the steam curve, the delta element expands moving the stem closer to the seat and flashing occurs in the upper portion of the discharge orifice. This momentarily chokes the flow and results in an instantaneous drop off of pressure acting on the plug, causing the plug to be pulled tightly against the seat.

Under extremely low loads, the trap will remain closed until the pressure opening force of the condensate overcomes the temperature closing force of the bimetal. A small seal of condensate is always maintained over the valve orifice to prevent the loss of live steam, because live steam cannot pass through water.

Under normal operating conditions, the trap modulates to follow process conditions and discharge condensate as it is formed. This provides smoother operation than with cyclic discharge traps, thus reducing unnecessary stresses and contributing to long service life.