When is it worth opting for a rapid steam generator instead of a conventional boiler?

When does a fast-starting generator make sense?

Variable consumption or shift work. If steam is only required at certain times of the day, for example during a single shift or on a line that starts and stops according to orders, a conventional boiler kept at a constant temperature consumes fuel even during periods when steam is not being used. The rapid-start generator can reduce the losses associated with maintaining the system at operating temperature and pressure, as it can be switched off and restarted more easily when consumption is intermittent.

Frequent starts and stops. A process that requires steam in short bursts, several times a day, reduces the efficiency of a conventional boiler every time it has to be restarted from cold. The rapid-start generator is designed precisely for this mode of operation, with a shorter time to return to operating conditions than a comparable conventional boiler.

Limited space. The small water volume of a rapid generator also results in a smaller physical footprint than a conventional steam boiler of equivalent capacity, which is particularly relevant for workshops or halls where available technical space is limited.

Potentially simpler authorisation and operating procedures. The design and parameters of certain rapid steam generators may result in different authorisation, monitoring and operating requirements compared to those applicable to a conventional boiler.

Classification cannot be determined solely on the basis of steam flow rate or the equipment’s trade name. Before purchase, the applicable technical specifications, the type of authorisation or approval required, the obligations regarding RSVTI and operating personnel, as well as periodic inspections, must be verified in writing.

If your situation does not fit any of the above scenarios and you require a constant supply of steam throughout the entire working day, and the installation falls under the scope of ISCIR in any case, a conventional steam boiler generally remains the more suitable solution.

What needs to be checked from an ISCIR perspective?

The ISCIR classification must be determined for the specific model and configuration of the installation. Factors such as pressure, volume, flow rate, heating method, auxiliary equipment, steam pipes and monitoring methods may be taken into account.

The assessment must specify:

• whether authorisation or approval for operation is required;
• whether the installation must be registered;
• which periodic technical inspections are mandatory;
• whether an RSVTI operator is required;
• which staff may operate the equipment and under what conditions;
• what obligations apply to the fuel supply system and steam pipes.

These requirements must be confirmed by the supplier in consultation with an authorised specialist before selecting the equipment.

Where does the cost difference lie, and why is it not just about the energy bill?

The cost difference between the two technologies is not only reflected in the fuel or electricity bill, but also in two categories of costs that are often overlooked.

The time required to reach operating conditions. When the process cannot begin until the plant is supplying the required flow rate and pressure, the start-up time affects the time available for production. The impact must be calculated based on the actual working schedule, the number of start-ups and the availability of other steam sources.

ISCIR compliance costs. The periodic inspections, authorisations and qualified personnel required by law for equipment exceeding the ISCIR thresholds represent a recurring cost which does not appear on the equipment’s price tag but influences the total long-term operating cost.

These two categories of costs explain why a comparison based solely on the purchase price provides an incomplete picture of the actual operating cost.

Water quality and total operating cost. Water treatment is important for any steam-generating plant. In the case of JUMAG equipment, the manufacturer specifies the use of a water softener sized according to water hardness, fresh water consumption and the plant’s operating regime.

The total cost must include the equipment, water treatment, fuel or energy consumption, blow-downs, condensate recovery, maintenance, consumables, technical inspections and plant shutdowns.

A rapid-start boiler may have an initial cost comparable to or higher than that of a conventional solution. The actual savings depend on the consumption profile, the number of start-ups, the degree of condensate recovery and how the entire system is sized.

When might a conventional boiler remain the right choice?

A conventional boiler may still be a justified choice when the existing plant is well-sized and efficient, the base load is high and stable, and the savings achieved through replacement do not cover the investment.

However, the decision cannot be based solely on the fact that the process operates continuously. Rapid-start boilers can be sized for continuous operation and can be installed in parallel to accommodate higher flow rates, load variations and redundancy.

The comparison must be made between specific configurations, at the same flow rate, the same pressure and the same requirements regarding steam quality and availability.

Can a rapid-start generator handle high flow rates and deliver dry steam?

The maximum flow rate is not determined solely by the type of technology, but by the chosen model and the system configuration. For higher requirements, several generators can be used in parallel, with units being started and stopped according to consumption.

Steam quality must be verified by the degree of dryness achieved at the system outlet. JUMAG specifies a residual moisture content of 3–5 per cent before the dryer and less than 0.1 per cent after a suitably sized dryer.

Before purchasing, the available flow rate at the required pressure, behaviour during consumption peaks, dryness level and the system’s ability to maintain process parameters must be compared.

When the existing system is oversized

A common situation in older workshops is inheriting a conventional steam boiler sized for a production volume that has long since ceased to exist. Over time, production or the business profile has changed, but the conventional steam boiler originally installed has remained the same and has become oversized for the current steam requirements.

The result is equipment that continues to be kept warm at high capacity, even though the factory’s current requirements could be met by much smaller equipment or a rapid-start generator, without the standby costs associated with a large reserve that is not utilised to its full capacity.

Modular configurations for variable consumption

For steam demand that varies significantly, several rapid-start generators can be installed in parallel. The units start up and shut down according to demand, and the system can provide both flexibility and redundancy.

Another option is a hybrid configuration, in which an existing boiler covers the base load, whilst a rapid generator handles peak loads. The choice between the two options depends on the existing plant, the magnitude of the peaks, the available space and the total cost of the modification.

Jumag solutions distributed by Texco

Texco distributes individual JUMAG steam generators and modular systems comprising multiple units. For sizing purposes, data is required on average and peak flow rates, working pressure, number of start-ups, operating hours, water quality, condensate recovery and available space.

Based on this data, it is determined whether the application can be met by a single generator, by multiple units that come on stream according to demand, or by a configuration integrated with existing equipment. The technical recommendation must include installed capacity, redundancy requirements, water treatment and estimated operating costs.