Customer Service

SNG_V1.0 Sequence of operation

1328 Azalea Garden Rd.
Norfolk VA. 23502
Fax: 757-855-3761

Date: August 2002

Contact: Customer Service (


This bulletin describes the general sequence of operation for Stationary Nitrogen Generators using the FX1n PLC running SNG_V1.0
System setpoints can be checked and modified via interface program BC_LINK.exe

Basic Overview

When an SNG unit is placed in the operational mode by pulling out the ON/OFF switch, the control system will check the system outlet pressure to determine whether it is below the start pressure setpoint (default 4000 psig). If the outlet pressure is below that point, the system will start the feed air compressor which will then pass heated compressed air through the membrane bundle in order to warm it. The gas coming out of the membrane will be dumped to the atmosphere through the soleniod 1SV.

While warming the membrane, the membrane outlet temperature will be monitored via the Temperature switch/gage 2TS. When this switch closes, indicating the membrane is operating at a temperature that will provide suitable purity, the system will close the membrane vent valve (1SV) and then start the Booster.

Once the booster has been started, the high pressure vent valve will be opened in order to purge the gas within the booster interstage separators. During this time the booster outlet will be held at 2000 psig by the outlet back pressure valve.

After a period of 60 seconds, the booster high pressure vent valve will be energised and the system will then be pumping nitrogen into its storage system.

While pumping nitrogen, the control system will open the low pressure condensate drains on a pre set time interval and will monitor the systems safety devices.

Once the system has pressururized the storage sytem to the pre set pressure, it will stop the booster and initiate the shutdown timer. The period of this timer will depend on whether the system has been set for constant run or start/stop operational mode. In start/ stop mode, the low pressure compressor will be operated for a period of ten seconds before the system shuts down. In the constant run mode, the low pressure feed air compressor will remain operational to keep the membrane bundle warm and pressureized to allow for quick restarts. If the unit is allowed to operate in constant run mode but the outlet pressure does not drop to the restart point within fifteen minutes, the system will shut down to conserve energy.


Message Center

During Operation, the first line of the message center will indicate the current status of the system. While the unit is turned of, the message will simply indicate "SYSTEM:OFF" however while the on/off switch is pulled out (ON) the first line of the message center will flash the System status for a period of two seconds followed by a text message indicating what function the system is currently performing. The messages displayed are as follows:

Event Status Display Message Display
System Powered/ Turned Off System: Off NONE
System Powered/ Turned On
Outlet pressure below setpoint
Membrane outlet temp low
System:Running Warming Membrane
System Powered/ Turned On
Outlet pressure below setpoint
Membrane outlet temp at setpoint
The System will start the booster and purge it
System:Running Purging Booster
System Powered/ Turned On
Outlet pressure below setpoint
Membrane outlet temp at setpoint
The purge timer has expired
System:Running Pumping Nitrogen
System Powered/ Turned On
Outlet pressure has reached setpoint
The System has been set to Start/Stop
The system will shut down the booster and operate the Feed air compressor
for 10 seconds
System:Standby Shutting Down
System Powered/ Turned On
Outlet Pressure has reached setpoint
The System has been set for constant run
the system will operate the feed air compressor to maintain system temperature
note: If the system remains unloaded for 15 min it will shutdown
System:Standby Running Idle
System Powered/ Turned On
Outlet pressure has reached setpoint
The shutdown timer has expired
10 seconds for Start/Stop
15 minutes for Contant speed
System:Standby Sleeping

Although the message center displays two lines of text at a time, each 16 characters in length, there are accually 8 lines that can be viewed by using the two up and down arrows below the display. The information to be displayed will be as follows:

Line information to be displayed
1 Message center (see above)
2 System Outlet Pressure
3 Last/Current fault code
4 Booster Temperature (Deg. Centigrade)
5 Feed Air Hourmeter Hr. Min
6 Booster Hourmeter Hr.Min
7 Last/Current Runtime hr.Min.Sec
8 Time to next ACD*

* Automatic Condensate Drain
To setup the system screen go to FX10DM text display setup

System faults.

During operation, the system monitors the following fault devices. When tripped, they will generate fault codes that will be displayed on the message center and begin to flash the fault light next to the message center with a preset number of flashes. The flashes will consist of the fault light being turned on for a period of 1 second and then of for a period of one second until the last flash which will only flicker the light and then hold it off for a period of 3 second before re-starting.

Fault Input Code # of Flashes Descrption
1PS X2 Low_oil 2 2 Booster Low oil Pressure
1TC Analog #2 Hp_Temp 3 Booster High Tempurature
2PS-1 X3 Low_inl 4 Booster Low inlet pressure
2PS-2 X4 HighInl 4 Booster High inlet pressure
1TS X5 Lp_Temp 5 Feed Air Compressor High Temperature
3TS X7 HighMem 6 Membrane inlet tempurature to high
Overrun N/A Overrun 7 The booster has operated without shutting down.
for a period equal to the overrun fault setpoint **
1AL X10 Feed_CBR 8 The low pressure compressor Circuit breaker has opened.

** In order to prevent the unit running while an excessive leak has developed in the high pressure piping and distribution system, the control circuit is programmed to fault out if the setpoint pressure has not been reached within a pre-set period. The default setpoint is 4 hours runtime, resetable with the BC_LINK.exe interface.