Flow Section

Nitriding Gas Supply

 

The Nitriding gas supplies enter the flow section from the top.  Each gas has a manual shut off valve as well as a regulator (regulators optional).  The regulators are to protect against fluctuations in incoming supply pressures.  The location for each incoming gas inlet is as follows from left to right: Nitrogen, Ammonia, and Disassociated Ammonia. Pressure regulation should be set between 12 and 20”.

 

High and Low Pressure Switches

 

Each gas has a High and Low pressure switch.  The location of these switches are just below the manual valves for the incoming gas.  The High Pressure Switch is on top and the Low Pressure Switch is on the bottom.  The switches have green LED indicators to indicate the pressure condition.  Example, If the LED indicator is OFF on the High Pressure switch then the incoming pressure from the supply gas is to high and the condition generates an audible alarm.  Each pressure switch has a dial setting on the front to make adjustments to the switch.  The pressure switches are set by SSi at the time of panel checkout.  SSi presets the regulators for 15” water.  The High and Low Pressure switches are set based on this value.  Any questions on the settings please call SSi technical support at 513-772-0060.

 

Vessel Pressure Switches

 

Vessel Pressure is the accumulated pressure of all gases flowing through the furnace.  The switches for Vessel Pressure are located to the immediate right of the gas pressure switches.  These pressure switches have LED’s to indicate high and low pressure. 

 

Sample Ports

 

Each gas has a sampling port below the pressure switches.  To take a flow pressure reading using a manometer, just connect the manometer to the sampling port and turn the manual valve until it is open.  Make sure the incoming supply valve for the gas being checked is also opened.

 

Emergency Nitrogen

 

Emergency Nitrogen can be added to the system in the event of an emergency.  The operator can initiate Emergency Nitrogen purge by turning the Emergency Nitrogen switch on the front of the control panel to ON.  The Emergency Nitrogen solenoid is a normally open solenoid and will be open on power failure to the control panel. 

 

Flow Head Unit

 

The process gas flow system is located below the sampling The flow head unit is divided into the following parts; flow control boards, valves, High and Low limits. 

 

Flow Control Boards - Each gas has an individual flow control board associated with the gas.  The board is located in the flow head unit and communicates to the 9210 controller.  The flow control board has a comm port on it that can be switched between RS-485 and RS-232.  The board must be in the RS-485 mode to communicate with the 9210.  The RS-232 mode allows for communication directly to a PC running the configuration software.  The RS-232 mode allows for downloading of flow curves and troubleshooting.  On the front of the flow head unit the LED display shows flow of each gas in SCFH.  The LED’s on the front of the unit display the following: Auto/Manual, Alarm, V1, V2.

 

Auto/Manual - When the Auto/Manual LED is ON the board is in the Auto Mode being controlled by the 9210.  The switch on the front of the control panel for each gas allows for the board to be put in Auto, Hand (Manual) or OFF.  The LED will be OFF when the switch is in Hand position.  The operator can turn the valve wheel by hand in this condition.

 

ALM – This indicator shows when the board is in an Alarm condition.  Alams include max range or high limit switch made.

 

V1 – V1 indicates the direction the valve is moving.  The LED is OFF when the valve is closing and ON when the valve is opening.

 

V2 – V2 indicates the board is given a Run/Stop command.  The LED is OFF when the valve is receiving a Stop signal.  The LED is ON when the valve is being given a Run signal.

 

Valves - Each gas has a needle valve attached to a motor.  The motor drives the needle valve via a worm gear.  The needle valve shaft has a wheel attached with a set screw that allows the valve to be turned by hand.  If adjusting the wheel by hand unplug the connector from the drive so the 9210 is not trying to open or close the valve during hand adjustment.

 

Limit Switches - Each valve has a limit switch that will not allow the valve to open past a preset limit.  These upper limits need to be set in the field for each gas. Before setting the upper limit, the maximum SCFH needs to be known for each flow meter. 

 

Instructions for setting the upper limits are as follows:

 

  1. Loosen the set screw on the wheel.

  2. Send a setpoint to the valve to obtain the maximum flow desired.

  3. Allow the valve to settle at the desired flow.

  4. Pull the wheel up till the limit switch is activated.

  5. Tighten set screw.

  6. Repeat for each valve.

  7. Drive each valve closed and then open past the max range to test the limit switch.  Be sure to have the event for that specific flow meter turned on under manual events.

 

Mass Flow Meters

    The Mass Flow Meters are located below the Flow Head Unit.  The flow meters send a 4-20ma signal to the flow boards to indicate actual flow. If there is no flow it will trigger a Lo FL alarm. If the flow meter has reached its maximum, all LED’s will be ON and the last one will be flashing. Each Mass Flow meter is calibrated for a specific range of flow depending on the gas associated with the meter.

 

Gas Solenoids

    Each gas has an associated solenoid, which turns on to allow flow.  The gas solenoids are located below and behind the Mass Flow Meters.  The gas solenoids can be activated manually by turning the switch on the control panel to HAND for the appropriate gas.  The solenoids are also controlled by the 9210 through the events in the recipe and on the manual events menu screen.

 

Back Pressure Valve

 

The Back Pressure valve is located behind and to the right of the Flow Head Unit.  The Back Pressure valve is attached to the exhaust of the furnace.  The valve provides the necessary back pressure to allow flow through the Sample Cell.  The valve also provides the ability to restrict the outside oxygen from entering the furnace through the exhaust.  During a power outage the Back Pressure valve opens fully to vent all gases and nitrogen purge out of the furnace. 

 

Differential Pressure Transmitter

 

The Differential Pressure Transmitter is located to the right and below the Gas Solenoids.  The transmitter sends a signal to the 9210 which controls the amount of back pressure to be applied to the system.  It is critical that no restrictions in the line other than the back pressure valve create the actual pressure.  IF the back pressure valve indicates pressure higher than setpoint and the valve is open this is an indication of a restriction or water down stream.

 

Drip Legs

 

There are three drip legs associated with the flow section.  The drip leg valves need to be opened under the following conditions;

 

  1. Whenever heating up the furnace under air.  Heating the furnace under air causes condensation to build up in the exhaust.  The buildup of water in the exhaust lines affects the back pressure reading.  The error in back pressure will affect the reading of the sample and directly affect dissociation readings.

  2. Prior to the addition of ammonia into the furnace.   After the heat up of the furnace, when the furnace is at temperature, the drip legs should be opened briefly to allow any water buildup to escape.

  3. Any time during blowout of lines during cool down cycles and Nitrogen flow.

 

 

DO NOT OPEN DRIP LEGS DURING AMMONIA FLOW OR DISASSOCIATED AMMONIA FLOW.  GASES ARE TOXIC AND VERY HAZARDOUS.

 

The location of the drip legs are as follows:

 

  1. At the bottom of the exhaust line

  2. Below the differential pressure transmitter.

  3. bottom of the Sample Cell.

 

Sample Cell Solenoid

    The Sample Cell solenoid is energized by event 7 through the program or manual event control.  The solenoid  should only be energized when the furnace is up to temperature and the event is turned ON.   Gas is allowed to flow to the sample cell when the solenoid is energized. 

 

Sample Cell Filter

    The filter on the inlet side of the Sample Cell Box can become clogged.  The part number for a replacement filter is 37051. 

 

DO NOT CHANGE THE FILTER WHILE AMMONIA OR DISASSOCIATED AMMONIA IS FLOWING.  THE GASES ARE TOXIC AND VERY HAZARDOUS.

 

The steps for replacing the filter are as follows;

  1. Close all incoming gas valves.

  2. Unscrew the clear bowl from the filter housing.

  3. Unscrew the filter holder.  The holder is the black plastic knob in the center of the filter.

  4. Pull off old filter and replace with new.

  5. Screw the filter holder back into the top of the filter housing.

  6. Screw the clear bowl back on the housing.

  7. Open incoming gas lines

 

Flow to the sample cell should be a minimum of .5 scfh and a maximum of 2.0.  This flow is critical to the nitriding process.  If flow is low replace the filter.  If you are unable to maintain flow contact Super Systems Inc at 1-513-772-0060 immediately.