View source for Sweet Gas Cooler(HT-1101)

[[File:SweetGasCooler.png|center|frame|Overview]]
==Overview==
The treated sweet gas exiting the top of the contactors will be saturated with amine/water and flows to the sweet gas cooler. (See Figure 5.) Here the gas is cooled to condense and recover any amine/water mixture. The cooler reduces the load on the TEG unit by condensing some of the water the TEG unit would have to remove. 

The sweet gas cooler is an aerial cooler with one bay equipped with two fans to cool the sweet gas to 104F. One fan runs at a fixed speed, while a variable frequency (VFD) motor controls the other. The outlet temperature is controlled by varying the speed of the VFD. The sweet gas cooler also uses a combination of internal air recirculation and fresh intake air to maintain stable cooling.

The plenum temperature is controlled by adjusting the position of two side louvers and the inside recirculation louvers. In FNNPF’s cold winters, warm air is recirculated in the cooler to prevent the condensed water from freezing in the tubes. This recirculating air is created by closing the top louvers and opening the recirculation louvers inside the cooler to:
*sufficiently cool the Sweet Gas leaving the contactor to condense some of the water vapour from the gas
*sufficiently warm the Sweet Gas leaving the contactor to prevent the water from forming ice or hydrates that could block the gas flow and/or rupture the tubes

During summer months the recirculation louvers are closed to move air across the tube banks and out through the top louvers to enhance cooling.

<u>The Sweet Gas Cooler (HT-1101) is equipped with:</u>
*a double tube bank (tube fin exchanger) with inlet and outlet header boxes at the west end
*two underside fans (one at the East end and one at the West end)
:-each fan discharges an upward flow of air through the cooler’s tube-fin exchanger
:-the west fan is belt-driven by a VFD-equipped 50 HP electric motor that operates under gas outlet temperature control with start/stop control
:-the east fan is belt-driven by a constant-speed 50 HP electric motor with start/stop control
*a heating medium coil below the tube bank
*air intake louvers at the base of the East and West sides . The side louvers:
:-can operate automatically on DCS plenum temperature control (described below)
:-are provided with seasonal fluff screens
*top outlet louvers that can operate automatically under DCS outlet temperature control - described below
*east recirculation louvers that can operate under DCS plenum temperature control - described below

===Outlet Flow===

The cooled mixture of sweet gas and water leaves the tube bank’s outlet via the outlet box has two outlets and connected from one line there is a 2” drain to the amine drain vessel . The two outlets combine into a single Cooler outlet flowline; the cool gas/water mixture:
*flows past an outlet temperature transmitter (TIT-1070) - described below
*flows through a block valve (normally open)
*flows to the [[Wet Sweet Gas Scrubber(PV-1105)]]

==Temperature Controls and Instrumentation==

''Inlet temperature instrumentation:'' The temperature transmitter (TIT-1059) upstream of the block valve on the gas inlet relays to DCS for onscreen display only.
''Plenum temperature controls and instrumentation:'' Maintaining the stream of air discharged by the fan at a constant temperature-(i.e., a constant plenum temperature) contributes to steady cooling and prevents tubes from freezing during the winter. To control the plenum temperature, the cooler is equipped with:
*two plenum temperature thermo elements ( installed above each fan) that relay to DCS for onscreen display and control.
*3 DCS-based temperature controllers (TC-1071A/B/C) that the CRO can set to either AUTO or MANUAL mode.

When the ambient controllers are set to AUTO mode, the controller:
*continually receives temperature data from the two plenum temperature thermo elements and selects the lowest of the two received temperatures
*based on the selected plenum temperature, modulates the following to maintain the setpoint plenum temperature:
**the base louvers on the east and west sides
**the east recirculation louvers

When the ambient controller is set to MANUAL mode, the CRO (via DCS) adjusts the louvers to maintain the plenum temperature - see winter configuration below.

''Outlet Temperature Control and Instrumentation:'' The cooler is equipped with:
*an outlet temperature transmitter (TIT-1069) that relays to DCS for onscreen display and control
*two DCS-based temperature controllers (TC-1070) and (TC-1070A) that the CRO sets to either AUTO or MANUAL mode.

When the controllers are set to AUTO mode, based on the received data, both controllers work as follows to maintain the setpoint cooler outlet temperature (85–90° F):
*one controller (TC-1070) modulates the VFD
*the other controller(TC-1070A) modulates the position of the top louvers

When the controllers are set to MANUAL mode, the CRO (via DCS) monitors the cooler outlet temperature and remotely adjusts the top louvers and south fan speed (see Winter Configuration, below).

==Operating Controls==

Each Cooler fan has its own local panel with START/STOP controls. The west fan’s local panel also has a manual speed selector switch with FAST/SLOW settings. Both fans are protected against excessive vibration; each has a local high-vibration shutdown switch and reset button.

===West Fan===

The west fan’s motor-starter in the MCC Building is equipped with a remote/off/local switch and a VFD control panel. The motor starter’s remote/off/local switch is used to transfer control to the east fan. When the switch is set to:
*Remote––the fan can only be operated from the Control Room. The CRO can either assume control of the fan (via DCS) or enable the DCS cooler’s outlet temperature controller to automatically control the fan. The Area Operator cannot control the fan from the local control panel in this mode.
*Off––the fan is off and cannot be restarted from the Control Room or from the local control panel at the fan.
*Local––neither the CRO nor the DCS gas outlet temperature controller can remotely control the fan. The fan can only be operated by the Area Operator (as directed by the CRO), using:
:-the local start/stop control panel at the fan to start or stop the fan
:-the local fast/slow speed selector switch at the fan to set the fan speed

===East Fan===

The east fan’s motor-starter in the MCC Building only has a remote/off/local switch. When the switch is set to:
*Remote––the CRO operates the fan from the Control Room. 
*Local––the Area Operator uses the start/stop control panel at the fan to start or stop the fan as directed by the CRO
*Off––the fan cannot be started or stopped from either the Control Room or the local start/stop control panel at the fan.

==Temperature Alarms and Shutdowns==

If either fan’s vibration shutdown switch detects high vibration, the switch triggers:
*that fan’s motor to shut down
*a vibration alarm onscreen in the Control Room.

When a fan shuts down on high vibration, the Area Operator:
*investigates and notifies Maintenance personnel if repairs are required
*ensures the problem is rectified and then uses the fan’s local RESET switch to clear the alarm and reset the switch so that the fan can be restarted (by either the CRO or the Area Operator, depending on the fan’s motor starter setting).

==Additional Specialty Lines and Valves==

===Glycol Heating Coil===

The Sweet Gas Cooler’s heating coil is equipped with manual valves. The Glycol coil is normally blocked in and is manually placed into service by the Area Operator. The coils are used as a preventive measure during a winter shutdown. The glycol coil provides sufficient heat to prevent ice/hydrate formation in the tubes and as a thawing measure, if incorrect winter operation of the cooler has caused ice/hydrate blockages in the tubes.

===Vents and Drains===
To prepare the tube bank for shutdown, the Sweet Gas Cooler (HT-1101): is equipped with:
*2” manual valve-equipped vents at the tube bank inlets (gas vents to atmosphere)
*2” manual drain valves at the cooler outlets (drained liquid flows to the Amine Drain Vessel)

==Operations Monitoring==

2 times per shift, the Area Operator does an inspection walkthrough of the cooler and its underside to ensure:
*the fans are running free of abnormal vibration, belt squeal, and bearing noise
*there is no evidence of tube freezing, leakage rupture

Fluff screens: During spring, summer, and fall operation, the Area Operator ensures that the screens at the cooler’s base intake louvers are properly installed to ensure that fluff does not foul the cooler’s tube bank. The Area Operator also inspects the screens, and, if necessary, cleans them. If the screens frost up during the winter, the Area Operator removes them to ensure adequate air flow at all time.

==Seasonal Configurations==

===Winter Config===

the CRO sets the Sweet Gas Cooler to its winter configuration, which is designed to prevent freezing/hydrate formation in the tubes. The winter configuration minimizes the fresh air intake/flow-through and maximizes internal recirculation of warm air. From the Control Room, the CRO configures the cooler for winter as follows via DCS:
*sets the ambient temperature controller to MANUAL mode, and then remotely:
**fully closes the east and west base intake louvers
**fully opens the recirculation louvers
*sets both gas outlet temperature controllers to MANUAL mode, and then remotely:
**shuts off the speed fan
**Set the VFD fan to slow

===Winter Checks===

on cold winter days, the Area Operator locally confirms that the Sweet Gas Cooler is running in its winter configuration (i.e., to minimize cooling flow through and maximize internal warm air recirculation):
*all base louvers are fully closed
*recirculation louvers are fully open
*One or both fans may be off
*That the underside of the outlet tube bank is warm. If it’s cold it may be indicating of freezing/hydrates in the tube bank.

===Summer Config===
during the summer months the CRO sets the Sweet gas Cooler to its summer configuration, which is designed to maximize cooling in the tubes. The summer configuration maximizes the intake of fresh air and minimizes warm air recirculation; the air flow passes through the tube bank and immediately leaves through the top louvers. From the Control Room, the CRO configures the cooler for summer as follows via DCS:
*sets the ambient temperature controller to AUTO mode and then remotely:
**fully opens east and west base intake louvers
**fully closes the recirculation louvers
*sets both gas outlet temperature controllers to AUTO mode with the setpoint at 85oF to 90oF. With the controllers in AUTO:
**the fixed fan runs at high speed
**the top louvers modulate, but will tend to be wide open
*sets the VFD fan to START

===Summer Checks===
On hot summer days, the Area Operator locally confirms that the Sweet Gas Cooler is running in its summer configuration (i.e., to maximize cooling air flow through and minimize internal warm air recirculation):
*all base louvers are fully open
*recirculation louvers are fully closed
*the east fan is on
*the west fan is running at FAST speed

<u>'''Note:'''</u>

During spring and fall, ambient temperatures vary widely (e.g., warm days, cold nights). Because of this variation, the CRO may have to frequently switch the cooler between its winter and summer configurations