Mechanical steam traps may be of the ball-float type or the bucket type.

Ball-Float Trap

In a ball-float steam trap, such as the one shown in figure 13-33, the valve of the trap is con-nected to the float in such a way that the valve opens when the float rises. The operating princi-ple of the trap is quite simple. When steam cools, it condenses (changes state) back to water. The liquid water, called condensate, flows by gravity into the chamber around the ball valve. As the water level rises, the float is lifted, thereby lifting the valve plug and opening the valve. The con-densate drains out and the float settles to a lower position, closing the valve. The condensate that passes out of the trap is returned to the feed system. In figure 13-33, the two white circles directly above and below the ball float are con-nections (holes) for a gauge glass, which the operator checks to set the desired liquid level in the steam trap.

Figure 13-33.-Ball-float steam trap.

Bucket-Type Trap

Figure 13-34 shows a common bucket trap which is suitable for high pressures and tem-peratures and has a large capacity. Its operation may be described as follows: As soon as sufficient water enters the trap, the bucket, being buoyant, floats and closes the valve. As condensation in-creases, the body of the trap fills and water enters the bucket, causing it to sink. The bucket being attached to the discharge valve, opens the dis-charge valve and the trap begins to discharge, con-tinuing to do so until the condensation is blown out of the body to the edge of the bucket. At this point, the water in the bucket continues to be forced out until the bucket again becomes buoyant and rises, closing the valve.