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THREE LINE ATMOSPHERE FLOW CONTROL
One line carries the hydrogen, one line the process/purge inert gas and one line the emergency inert purge.
HYDROGEN LINE FLOW CONTROL
Hydrogen line includes manual shut off ball valve, pressure regulator, relief valve, pressure gauge, solenoid for automatic shut off, flowmeter with regulating valve, low flow switch, flame arrestor and check valve.
INERT PROCESS AND PURGE LINE FLOW CONTROL
Inert gas purge line includes manual shut off ball valve, pressure regulator, pressure relief valve, pressure gauge, flowmeter with regulating valve, solenoid for automatic actuation, and check valve. Purge gas may be nitrogen, argon or helium.
EMERGENCY INERT PURGE
A totally separate emergency inert gas purge line includes manual shut off ball valve, pressure regulator, pressure relief valve, pressure gauge, flowmeter with regulating valve, normally open solenoid for automatic actuation, and check valve. This must be connected to a separate tank of inert gas.
INERT PURGE AROUND ELEMENT CHAMBER
The furnace has a separate inert atmosphere purge between the outside of the retort and the elements. This has its own flowmeter with regulating valve and branches off the inert process gas purge. This protects the system in case of a leak in the retort. It is especially important when operating with hydrogen below 1400F (760C).
ATMOSPHERE SAMPLE PORT
An alloy sample port is provided. There is a ball valve to close this off when not in use. This is used to sample the atmosphere for oxygen and hydrogen content.
ELECTRIC BURN OFF IGNITOR
An electric ignitor made of silicon carbide maintains a positive ignition source at the gas exit. This includes an electronic sensor which signals an alarm to shut off hydrogen if the ignition source is lost. As an option, two ignitors can be provided.
WATER COOLING SYSTEM
On retorts that have water cooled seals a manual ball valve shut off, flowmeter and regulating valve, relief valve and low flow switch are included plus hook ups for the inlet and outlet.
VISUAL AND AUDIBLE ALARMS
A piezo buzzer with push button silencer is provided to indicate any alarm condition. In addition, specific pilot lights indicate precisely which alarm conditions are activated. Silencer does not turn off pilot light indicator.
VISUAL INDICATION OF GASES
There are pilot lights which indicate which gases are flowing.
HYDROGEN LOW FLOW SWITCH
Hydrogen line has a low flow switch to shut it off if hydrogen flow is not sufficient to maintain positive retort pressure. There is a delay timer to temporarily bypass the switch for hydrogen introduction.
DOOR INTERLOCK
There is typically a door interlock switch which prevents hydrogen from flowing unless the door is closed.
POWER FAILURE
Emergency purge is activated if there is a power failure. (There is a normally open solenoid to do this.)
EXTERNAL MUFFLE PURGE FLOW ALARM
A low flow switch shall initiate emergency purge if there is a low flow of purge gas around the retort.
NITROGEN PURGE CAPABILITY ALARM
A pressure switch on both the process and back up emergency nitrogen supply monitors the ability of the nitrogen to flow in case of an alarm condition. Low pressure opens solenoids from both lines.
LOSS OF BURN OFF FLAME IGNITION SOURCE
Turns off hydrogen and initiates inert purge.
WATER COOLING ALARM
On furnaces equipped with a water cooling system (typically for a door seal), there is a low flow switch alarm which turns off element power and hydrogen, and initiates a purge.
PURGED CONTROL PANEL
The main electrical control panel is purged with either instrument air or nitrogen. A differential switch must be activated for the control system to operate.
LOW TEMPERATURE ALARM
The control has a temperature based alarm which can be set at any temperature (normally 1400F - 760C) below which hydrogen shuts off. This is not strictly necessary when using the purge in / purge out method of hydrogen introduction / removal; however, it is an extra level of safety that can be used when desired.
ELECTRICAL ATMOSPHERE CONTROL SYSTEM
All electrical components that are in the hydrogen flow area are either explosion proof, intrinsically safe or rendered safe as per N.E.C. Articles 500 and 501.
FITTINGS AND PIPING
Pipe is normally copper throughout the flow panel. Fittings are brass flare type NPT fittings where possible. These are easy to disassemble for maintenance work and are extremely tight.
BACK PRESSURE CONTROL
The outlet from the retort has a needle valve which allows control of the back pressure of the furnace. There is a pressure relief valve before the needle valve to prevent over pressurization of the retort. There is a pressure gauge calibrated for between 0 and 90" W.C. pressure.
FLOW CONTROL PANEL
A floor standing flow control panel contains all the flow train components. This panel is constructed of 10 gauge steel from the floor to the top of the panel. The panel has an open back for easy maintenance and 12” deep side panels for protection of the components and good appearance.
LOSS OF EXHAUST VENTILATION
Specific alarm contacts and differential pressure switch to be installed in the ventilation system are provided. This initiates inert purge and shuts off power in the case of low ventilation flow.
SAFETY REGULATIONS
This atmosphere system is designed to meet or exceed the regulations of the National Fire Protection Agency for controlled atmosphere furnaces (NFPA-86C.)
IRI OR FM APPROVAL
L&L will provide all necessary information to customer’s insurance carrier for approval purposes.
ATMOSPHERE INSTRUCTIONS
A very complete instruction manual is included. This includes theory of operation of all major systems and subsystems, full maintenance instructions and schedules, component lists, component instructions, data sheets, emergency procedures, cautions, star t up and shut down procedures, and a complete flow schematic of the atmosphere system.
NOTE CONCERNING INTRODUCTION OF HYDROGEN
The hydrogen must be introduced into the furnace manually by activating a switch on the control panel. This is according to the NFPA-86C regulations. An automatic purge cycle with automatic introduction of hydrogen is not allowed. Using the “purge in” method the operator must confirm that the oxygen content inside the furnace is below 1% before introducing hydrogen.
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