Maintenance - Emerson Fisher ATST Desuperheater Instruction Manual

Instruction Manual
D104734X012
WARNING
Failure to use a strainer could result in nozzle clogging and subsequent property damage or loss. Uncontrolled
temperatures resulting from clogged nozzles may result in equipment or process temperature limits being exceeded.
Exceeding system temperature limits could result in property damage or personal injury.
7. A length of straight pipe is required downstream of the ATST desuperheater to ensure complete vaporization of
cooling water. An example of a typical installation appears in figure 2. Consult the ATST cooler sizing sheet for the
required distance of straight pipe. This is unique for each application and is supplied by Emerson.
8. Typically, a temperature sensor will be mounted downstream of the ATST desuperheater. This distance will vary
depending on a number of factors including steam velocity and percentage of spraywater. Consult the ATST cooler
sizing sheet provided with the unit for this temperature sensor distance. The steam line should not have any branch
lines dividing the steam flow between the ATST desuperheater and the temperature sensor. If you have any
questions, contact your
9. A typical installation is illustrated in figure 2. A temperature sensor (TE) measures changes in temperature and a
temperature transmitter (TT) transmits the signal to the temperature control device. The output signal from the
controller is sent to the positioner on the cooling water (spraywater) control valve (SWCV). The positioner's output
signal strokes the SWCV open, increasing water pressure on the nozzles. Increasing water pressure upstream of the
nozzles increases water flow through the nozzles.
The atomizing steam valve operates either as on/off or control depending on application, and the type of operation
will be listed in the ATST sizing. In on/off operation, the atomizing steam valve is normally controlled so it fully
opens just prior to the spraywater control valve opening. In control operation, the valve signal is modulated based
on a downstream pressure target, as noted in the ATST sizing.

Maintenance

WARNING
Avoid personal injury or property damage from sudden release of process pressure or bursting of parts. Before performing
any maintenance operations:
D Always wear protective gloves, clothing, and eyewear when performing any maintenance operations to avoid personal
injury.
D Use bypass valves or completely shut off the process to isolate the desuperheater from process pressure. Relieve
process pressure and drain process media from the desuperheater.
D Use lock‐out procedures to be sure that the above measures stay in effect while you work on the equipment.
D Check with your process or safety engineer for any additional measures that must be taken to protect against process
media.
Emerson sales office.
ATST Desuperheater
July 2022
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