Blowdown Vessel Systems

Blowdown Vessel Systems

Overview

As the water in the boiler evaporates into Steam it leaves impurities (Total Dissolved Solids – TDS) which consequently coat the inside of the boiler.
The more these deposits build up, the more inefficient the boiler can become:

  • High TDS – results in Plant & Production downtime.
  • Low TDS – leads to noticeable increases in costs of fuel & chemical treatment.

Therefore, it is essential to ensure accurate blowdown methods in order to maintain steam quality
This is particularly important when continuous blowdown is also used on the boiler. The best way of disposing of this blowdown is to pipe it to a blowdown vessel.

The advantages of a blowdown vessel over a blowdown pit are:

    • They are fraction of the cost and size.
    • Quick and easy to install
    • Low maintenance solution for the replacement of blowdown pits.
    • Safe- no cover plate to lift or open area for staff to fall into.
    • Dissipates heat more readily.

The blowdown vessel is also designed to safely handle continuous blowdown, blowdown from level control chambers and level gauge glasses. It can also accommodate other high pressure drains providing it has been sized to do so.

Valveforce blowdown vessels are designed to cool down water from boiler purges including:

  • Bottom blowdown
  • Level gauge glass blowdown
  • Level probe standpipes blowdown
  • TDS continuous blowdown

As per PM60, the blowdown vessel has to have a design pressure of minimum 25% of boiler design pressure.

Design:

  • Design code: ASME VIII Div. 1 or PD5500 depending on size
  • Design pressure: 7 barg
  • Design temperature: Min 0 / Max 171°C
  • Hydrostatic test pressure: 13.68 barg
  • Material of construction: P265GH plate
  • Inside finish: self colour
  • Outside finish: Wire brushed clean with one coat metal primer
  • Inspection opening gasket: Silicone

Blowdown from a single boiler

 

The TDS blowdown can be connected to the bottom blowdown pipeline downstream of the bottom blowdown valve and then in a single pipeline to the blowdown vessel. The blowdown from Level Control and Level Gauge drains can be manifold into a single, separate line to a separate, dedicated connection on the vessel.

 

Blowdown from two or more boilers

When blowdown from two or more boilers is manifold to one blowdown vessel, the vessel must be sized for the total blowdown rate. To safeguard personnel, who may be working on a shutdown boiler, the pipework must be designed to prevent blowdown from one boiler entering any other. The blowdown vessel must have three separate inlets for each type of blowdown drain – one each for Bottom Blowdown, Automatic TDS system, and Level Control/Level Gauge drains. Manifolds are connected to each of these inlets. The number of branch connections on each manifold equals the number of boilers. The drains from each boiler are run to the relevant manifold in separate pipework, each pipe terminating at the manifold in an isolating valve and check valve.

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