Process Description and Challenges

Clean steam generation and distribution is a fairly straightforward
process. Steam is generated from a pure water source and then distributed
throughout the facility. Each usage point for steam typically has a steam
trap for condensate removal.

Typical Instrumentation Requirements

Temperature measurement is required at some use points. Be sure to consult
with Sterility Assurance personnel to determine the requirements for
temperature measurement. Thermocouples or RTDs are most often used.

Steam pressure regulation is also required. Typically, spring-driven steam
pressure regulators are used. Care must be taken to avoid dead spots in the
design of steam pressure regulators and steam trap locations.

Sample points will likely require point-of-use condensers. It is typical that
these systems are instrumented with local gauges and manual valves only,
so there is little automation.

Monitoring or recording of steam use may be required. Mass flow meters
are generally the best solution for this. Be sure to choose a design and
location that will not create a problem with condensate build-up.

Control Strategies

Communications

Clean steam generators are typically supplied as a packaged unit with its
own dedicated control system. Distribution systems typically have a
custom-built steam distribution system. There is little valving or instrumentation;
it is possible that all steam distribution valves and instruments
can be "owned" by the unit operation that is drawing the steam. This
greatly simplifies the design, testing, and validation.

Sequences

Steam generation is carried out continuously. Additional sequences may
be supplied for system maintenance.

Steam distribution is a single, continuous operation.

Control Loops

Steam pressure control maintains the system pressure. Of course, relief
valves are required to prevent over-pressure.

Calculations

There are no calculation concerns for clean steam.

Tuneables

If you have a large clean steam distribution system, you may have a common
header, with smaller local headers supplying parts of the operation.
In this case, it is common to put a smaller steam regulator at each of these
branch headers. You will want to tune the regulators so that a single operation
does not starve the main header.