World Leaders in Ultra-Pure Heating
Revision 10
www.heateflex.com
01/17/13
405 E. Santa Clara St.
Arcadia, CA 91006-7218
Tel: (626) 599-8566 Fax: (626) 599-9567
_________________________________________________________
4.2.2 Shellside (Steam) Over-Temperature
Over-temperature protection is provided by a thermocouple, which senses the steam
temperature in the exchanger vessel and acts as an input to the Auto-Shutdown System, which
will close the pneumatic ball valve on the steam supply at the inlet to the exchanger if the
steam temperature ever exceeds 130°C. This value is set at the factory and is not adjustable by
the user.
_________________________________________________________
4.3 Tube Side (Process) Safety Mechanisms
The tube side of the exchanger is ultra-pure D.I. water, which under low flow conditions can
reach approximately 120°C, equal to the shellside steam temperature. The working pressure of
the Sygef PVDF piping system, used for the D.I. water, has a working pressure of 60 psig (with
a twenty-year, 220% safety factor) at this temperature and constitutes the working-pressure
rating of the unit overall.
In actuality, the only section of the PVDF piping that will "see" this temperature is between the
exchanger outlets and the hot mixing-valve located on the right side of the main control panel.
The balance of the piping is exposed to temperatures at or below the system set point
temperature.
_________________________________________________________
4.3.1 Process Over-Temperature
Although the PVDF piping and other components on the unit itself are designed to withstand
any temperature up to the shellside steam temperature, the customer‟s equipment and piping
downstream of the unit may not be. Therefore, the Auto-Shutdown System monitors the D.I.
water temperature at the outlet of the unit and will close a pneumatic ball valve on the steam
supply inlet to the exchanger if there is an over-temperature condition in the process water
leaving the unit.
Additionally, since the tube side temperature can go no higher than the temperature of the
shellside steam, which is limited to approximately 130°C by the Auto-Shutdown System, over-
temperature of the tube side is de facto protected by the shellside safety mechanisms as a back-
up to the primary, Process Over Temperature Alarm protection.
The Process Over-Temperature alarm set point and alarm delay can be modified on the
Diagnostic Information screen of the Process Over-Temperature Alarm. The default Process
Over-Temperature Alarm and Process Over-Temperature Alarm Delay set points are 95
o
C and
20 seconds respectively.
