Types of Steam Trap: Ball Float Steam Trap

Steam Trap Types:

Based on the working principle of the Steam Trap can be classified as follows:

Density Operated Steam Trap:

  1. Ball Float
  2. Inverted Bucketed

Temperature Operated (Thermostatic) Steam Trap:

  1. Balanced Pressure
  2. Liquid Expansion
  3. Bimetallic

Kinetic Energy Operated Steam Trap:

  1. Thermodynamic
  2. Impulse or Orifice

Ball Float Steam Trap:

 The Ball Float Trap works on the principal of sensing the difference in the density of Steam and Condensate. The accompanying sketch below (refer Figure-1, Exhibit 34.3) shows the constructional details of the above Trap.

Ball float steam trap

Ball float steam trap

Ball float steam trap

Ball float steam trap

The Condensate on reaching (and eventually filling) the trap body, causes the Float to rise as per the level of Condensate in the Trap body, consequentially lifting the disc element offs itsseat to allow the Condensate to exit out.

The level of the disc/ seat assembly is so adjustedthat it always remains immersed in the Condensate even at the lowest level of Float (i.e. whenthe flow of Condensate is fully stopped).

Therefore the steam can never escape from the exitport. More over the Float responds almost instantly to any buildup of Condensate above itsminimum level causing the Condensate to exit out of the discharge port as soon as it isformed.

With regards to venting of initial air, the Float Traps are normally fitted with anauxiliary vent (pressure balanced thermostatic trap) which remain wide open (at cold condition) to allow quick venting of air during startup.

However as soon the Steam/Condensate (following cold air) fills the trap the auxiliary vent on sensing the steam temperature snaps shut to disallow the steam to escape.

Salient Features of Ball Float Steam Trap:

  1. Continuous and modulating discharge prevents any pressure fluctuations in the condensate system.
  2. High heat transfer efficiency (i.e. condensate is discharged as rapidly as it is formed without any banking up.
  3. High air venting capacity through fully open auxiliary vent
  4. It can successfully perform for a fairly high range of steam pressure.
  5. Large and bulky.
  6. Ball float mechanism is susceptible to damage due to Water Hammer.
  7. Can easily freeze under subzero ambient conditions and hence must be provided withSteam Lock Release Valve (SLR) feature.