Model 275 HART Communicator (Travel Cutoff High) in percent, Tvl Cutoff Low (Travel Cutoff Low) in percent,
100
D Tvl Limit High—Travel Limit High defines the high limit for the travel in percent (%) of ranged travel. It is the maximum allowable travel (in percent of ranged travel) for the valve. During operation, the travel target will not exceed this limit. When a Travel Limit High is set, the Travel Cutoff High is deactivated, since only one of these parameters can be active. Travel Limit High is deactivated by setting it to 125.0%.
Ranged Travel, %
125
0
–25 –25
0
Ranged Input, %
100
125
Input Characteristic = Linear 125
D Tvl Limit Low—Travel Limit Low defines the low limit for the travel in percent (%) of ranged travel. It is the minimum allowable travel (in percent of ranged travel) for the valve. During operation, the travel target will not exceed this limit. When a Travel Limit Low is set, the Travel Cutoff Low is deactivated, since only one of these parameters can be active. Travel Limit Low is deactivated by setting it to –25.0%. D Tvl Cutoff High—Travel Cutoff High defines the high cutoff point for the travel in percent (%) of ranged travel. Above this cutoff, the travel target is set to 123.0% of the ranged travel. No rate limiting is in effect when the high cutoff is exceeded. When a Travel Cutoff High is set, the Travel Limit High is deactivated, since only one of these parameters can be active. Travel Cutoff High is deactivated by setting it to 125.0%.
Ranged Travel, %
100
0
–25 –25
0
Ranged Input, %
100
125
Input Characteristic = Equal Percentage 125
100
D Tvl Cutoff Low—Travel Cutoff Low defines the low cutoff point for the travel in percent (%) of ranged travel. Below this cutoff, the travel target is set to –23.0% of the ranged travel. No rate limiting is in effect when the low cutoff is exceeded. When a Travel Cutoff Low is set, the Travel Limit Low is deactivated, since only one of these parameters can be active. Travel Cutoff Low is deactivated by setting it to –25.0%.
Ranged Travel, %
Travel Cutoff Low can be used to ensure proper seating load is applied to the valve. A Travel Cutoff Low of 0.1% is recommended to help ensure maximum shutoff seat loading. Min Open/Close—Select Main Menu, Detailed Setup, Reponse Control, and Min Open/Close. Follow the prompts on the HART Communicator display to configure the following categories under Min Open/Close: Min Opening Time (Minimum Opening Time) in seconds, and Min Closing Time (Minimum Closing Time) in seconds.
0
–25 –25 A6535
0
Ranged Input, %
100
125
Input Characteristic = Quick Opening
Figure 6. Ranged Travel Versus Ranged Input, for Various Input Characteristics (Zero Control Signal = Closed)
D Min Opening Time—Minimum Opening Time is configured in seconds and defines the minimum time for the travel to increase the entire ranged travel. This rate is applied to any travel increases. A value of 0.0 seconds deactivates this feature and allows the valve to stroke open as fast as possible.
13