Mechanical traps are steam traps that operate on the principle of specific gravity (specifically the difference in the specific gravities of water and steam), unlike other types of steam traps that rely on temperature change or velocity/phase change. In mechanical traps, the valve opens and closes due to the movement of a float that rises and sinks with the flow of condensate.
Mechanical traps are able to operate in precise response to the flow of condensate without their performance being compromised by most external factors. This is one of their distinct advantages over thermostatic and thermodynamic steam traps,
In float traps, the position of the float is affected directly by the level of condensate in the trap. The float responds to condensate flow, opening and closing the valve to compensate accordingly.
In lever float designs, a float is attached to a lever that controls the valve. As condensate enters the trap, the float becomes buoyant and moves the lever, causing the trap valve to open. However, due to the limited movement of the lever arm, the valve head often remains in the path of condensate flow, which may result in an extra pulling force acting to close the valve during high flow conditions.
In inverted bucket steam traps, the bucket within the trap is attached to a lever that opens and closes the trap valve in response to the bucket’s motion. When steam or air flows into the underside of the inverted bucket and condensate surrounds it on the outside, the steam causes the bucket to become buoyant and rise. In this position, the bucket will cause the trap valve to close. There is a vent hole in the top of the bucket that allows a small amount of the vapor to be released into the top of the trap, where it is discharged downstream. As vapor escapes through the vent hole, condensate starts to fill the inside of the bucket,
ADVANTAGES OF THE THERMODYNAMIC STEAM TRAPS
Thermodynamic traps can operate across their entire working range without any adjustment or change of internals.
They are compact, simple, lightweight and have a large condensate capacity for their size.
Thermodynamic traps can be used on high pressure and superheated steam and are not affected by waterhammer or vibration. The all stainless steel construction offers a high degree of resistance to corrosive condensate.
Thermodynamic traps are not damaged by freezing and are unlikely to freeze if installed with the disc in a vertical plane and discharging freely to atmosphere. However, operation in this position may result in wear of the disc edge.
As the disc is the only moving part, maintenance can easily be carried out without removing the trap from the line