The Complete Steam Guide

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Why is a Steam Distribution Header needed in a Steam Distribution System? How is their Sizing done?

The steam distribution header is a manifold where steam from a single / battery of boilers is collected and distributed to different utilization sections, blocks or equipment. Isolation valves are provided on inlet line as well as the outlet lines.

As a good practice spare nozzles should also be provided to allow the addition of a new boiler / user subject to provision being kept in the sizing of the header for increased capacity.

The objectives of a steam header are :

  • To facilitate isolation of any Boiler or any user plant from a single location, ie. in the Boiler house or at the battery limits of the blocks / sections.
  • If the Plant has expansion plans involving addition of a boiler and or user plant to the existing set up, the steam distribution header can be suitably designed to conveniently execute the expansion plans. For this spare capacity, spare nozzles have to be provided within existing Header. This enables the plant to build in modularity in the distribution network for ease of future additions.
  • The Header acts as buffer to cope up with fluctuations in the Steam demand of the Process at steady pressure.

Steam headers are designed for steam velocity of 15 m/s. This reduced velocity ensures :

  • Effective separation of steam, air and condensate.
  • The size of the header is greater than that of steam line. Thus, the header provides space for the steam to separate air and condensate from it.

    It is recommended to install following accessories on the Distribution Header –

    • An air vent
    • Drain with thermodynamic drain trap
    • Pressure Gauge
    • Thermostatic Air Vent with Dial Thermometer
    • Safety valve

    With this, the quality of steam leaving the header improves.

Can I take a tapping from my existing Steam Distribution Header?

Steam line headers are sized for a particular steam load. Adding another tapping would mean increasing the steam flow-rate. It should be first checked whether the boiler can generate extra steam and if the steam header is capable of handling this increased steam flow-rate.

If these conditions are satisfied then additional tapings from the main line can be taken. However, such modification of Header involves certain steps for approval / Inspection by statutory Inspection agency like IBR which has to be followed.