Description
早会开场白
Many applications require a control valve asmbly to remain in the position where it is prior to a specific system failure (lock-in-last position).
The type DSC-24 Tiara® signal comparator, shown in Figure 1, is specifically designed to英语面试常见问题
monitor 4-20 mA input signal to a valve positioner.
Upon loss of this signal, or when the signal falls below a pre-configured threshold, the comparator will activate an internal safety circuit. This safety circuit, placed between a solenoid valve and its power supply, will eventually cau the solenoid valve to trip.
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The solenoid valve, combined with a switch valve, can be placed in the line with the actuator to provide lock-in-last function.
Features
∙ Fast Respon – with a extremely small dead-time, the comparator responds faster than the positioner system to the signal failure.
∙ Versatile – can be ud with either conventional electric-pneumatic positioners or HART® communicating smart positioners.
∙ Ea of U – the input signal threshold value
is
adjustable.
The白萝卜英文
comparator
engagement time ud to delay the relea of the locking system, is also adjustable. Figure 1. A Front View of Type DSC-24
Signal Comparator
∙ Flexible Mounting – the water-proof housing allows it to mounted in the field or control room.
Typical Lock-in-Last Solution
Figure 2 is a schematic of a single acting actuator with lock-in-last capability on loss of supply pressure or loop current. The valve asmbly with a single acting actuator us a three-way switching valve with a solenoid valve.
Under normal operating conditions, power is supplied to the solenoid valve and adequate supply pressure is available to the switching valve. Upon loss of supply pressure, the t point of the switching valve is exceeded and the switching valve trips, causing the pressure locked in the actuator.
未冷藏疫苗流入
Tiara ®
Signal Comparator
Shanghai Tiara
Tiara
enjoying®
Data Sheet
Form: 51.DSC-24 May 2006
Type DSC-24
tofel考试报名
Figure 2. Lock-in-Last Position on Loss of Supply Pressure, Loop
Power and Control Signal for a Single Acting Actuator
Upon loss of loop current, the internal safety circuit actuates. This cuts off power to the
solenoid valve, causing the solenoid to trip.
When the solenoid valve trips, the supply pressure that was holding the switching valve open is exhausted to atmosphere. This
等位基因频率
simulates a loss of supply pressure, causing the switching valve to trip.
The same principle ud for a control valve
asmbly with a single acting actuator is ud for a control valve asmbly with a double acting actuator. In double acting applications, a trip valve with two output ports is required to provide locking pressure capability on both sides of the double acting actuator.
Specifications Detailed specifications are shown in table 1. Table 1. Specifications
Wiring For wiring details of the unit, e Figure 3. Note To avoid personal injury or property damage, do not connect low voltage cables to high voltage terminals, or vice
versa.
Page 2 Type DSC-24
Data Sheet
Form: 51.DSC-24
May 2006
Figure 3. Comparator Wiring
Installation
The comparator can be mounted on the valve actuator in the field or on the marshalling panel in the control room.
Figure 4 shows a typical mounting on the actuator in the field.
耻辱的意思Figure 4. A Field-mounted Comparator
Data Sheet
教师编制考试内容Form: 51.DSC-24 May 2006
Type DSC-24
Page 3
Shanghai Tiara M&E Co Ltd
Rm 202, Bldg 25, Lane 621, Weiye Road Shanghai 201100
Tel: 021 5499 7269
Fax: 021 5499 7273
© All rights rerved, 2006
Data Sheet Form: 51.DSC-24
May 2006
Type DSC-24
