Steam Warm Up Systems

The initial start-up/warm-up stage of a steam system is often the most problematic and at which high condensate and thermal expansion levels within the steam system and steam line occur.

To counter these issues, a steam warmup valve is therefore essential to ensure the safe and reliable operation of the wider steam system.

Here, to optimise safety and reliability, the steam line is warmed over a predetermined period to bring the system to its desired pressure and temperature.

Steam warmup valves are usually installed on the steam line in a piped or bypass loop configuration and work in conjunction with an isolation valve (typically of gate, butterfly or ball valve construction) or fitted within a pressure reducing valve station. During the predetermined warmup period, the smaller warmup valve is opened ahead of the larger isolation valve or PRV, allowing small quantities of steam into the system to gradually warm up components and pipes. This warming also helps to ensure pressure is equal on both sides of the larger valve, which is essential as it enables the valve to be opened without external force and reduces wear and tear by reducing thermal shock, water hammer, wire drawing and erosion.


Warmup valves are most commonly used on steam lines of at least 3 inches in diameter, with longer and larger pipes requiring a larger valve. Therefore, the size of a warmup valve should be determined by the length and diameter of the steam line that needs warming. It is also possible that warmup valves be installed, one for warming up and the second for isolation on large steam lines with larger pipes.

The type of warmup valve specified should also be considered depending on the following characteristics:

  • a needle valve is the preferred solution for throttling steam
  • globe valves also considered for internal valve design
  • the internal permissible leak rate standard should be higher than a Class IV shutoff
  • outlet pipes need to be increased by one pipe diameter (e.g. ¾” valve = 1” pipe)
  • both a warmup valve and isolation valve should be installed on the warmup line

In steam systems using ball or butterfly (quarter-turn) valves for isolation, warmup valves are also installed for the control of pressure and heating of the system that would not otherwise be possible using just the quarter-turn valve itself.

Product Variations

To ensure the correct specification of a steam warmup system, Valveforce can undertake site surveys to determine:

  • bespoke system design and construction
  • installation
  • commissioning
  • servicing/maintenance contracts

 If you’re looking for new steam warmup system or replacement warmup valves for your steam line, call Valveforce on 0121 711 1908 or email to discuss your requirements.


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