Spirax Sarco SP500 - Page 49

IM-P343-35 CTLS Issue 5
49
SP500 Electropneumatic Smart Positioner
9.5.4 MIN-T - minimum travel setting
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Programming notes
Enables the minimum valve travel to be set as a percentage of the maximum travel obtained during autostroke.
Maximum setting is MAX-T less 33.3%.
Default value is 0%.
Use and keys to alter the displayed value. Press key to accept the displayed value and advance to
the maximum travel setting (MAX-T).
Commissioning notes
Minimum travel should be used where a minimum flowrate is required to be maintained through the valve,
(i.e. a cooling water application). Setting a minimum travel % value will prevent the valve fully closing.
The input signal span range set (MIN-R) and (MAX-R) will operate over the travel limits set. If a value
for MIN–T is set it will exclude the setting of shut-off minimum (S-MIN) for control action direct (DIR)
and shut-off maximum (S-MAX) for control action reverse (REV).
9.5.5 MAX-T - maximum travel setting
•
Programming notes
Enables the maximum valve travel to be set as a percentage of the maximum travel measured during
autostroke. Minimum setting is MIN-T plus 33.3%.
Default values will depend on the selection of valve type (2-port or 3-port) and control action (direct or
reverse) as follows:
Valve type Direct Reverse
2-port 95% 95%
3-port 100% 100%
Use and keys to adjust the displayed value. Press key to accept displayed value and advance to the
next function.
Commissioning notes
The maximum valve travel percentage should be used to prevent a control valve fully opening. This is
useful for applications where the valve is oversized or to restrict the maximum flowrate through the valve.
On 2-port valves the default value is 95% to prevent the back of the plug hitting the bonnet. On 3-port
valves to ensure shut-off on both seats a 100% setting is required.
The input signal span range set (MIN-R) and (MAX-R) will operate over the travel limits set.
If a value for MAX-T is set it will exclude the setting of shut-off maximum (S-MAX) for direct action
(DIR) and shut-off minimum control action (S-MIN) for reverse action (REV).