Liquid Nitrogen Distribution System

04/19/23 EOS Tutorial #EOS220 1

Liquid Nitrogen Distribution System

This tutorial is intended to familiarize EOS personnel with the operation of the Liquid Nitrogen Distribution System (LNDS)

Contents:

1. System Description

2. Manual Control Panel

3. Remote Control

4. Alarm Response


System DescriptionThe APS has installed a Liquid Nitrogen Distribution System (LNDS). This system consists of four modules: A - D. Each module is supplied by a 3000 gallon liquid nitrogen dewar. These dewars are located in the open gas yards between 431/432, 433/434, 435/436, & 438. The system is operated at approximately 40-psi pressure and is always kept full under normal operating conditions. The lines are vacuum jacketed for insulation purposes and do not show evidence of the cryogenic liquid inside. Piping is marked to indicate that the line contains liquid nitrogen.

3000 Gal. Dewar

Pneumatic Dewar Valve

Vacuum Jacketed Transfer Line

Shut Off ValveSystem Relief Valve


System Description: Graphical RepresentationEach module has a temperature sensor at its center and each end. There are a total of 35 individual drop lines supplying LN2 to each of the Insertion Device (ID) beamlines.

Interconnect valve

User Drop Valves

3000 GallonStorage Dewar

Dewar Valve

Main Feed lineUser Drop Line

Temperature sensorlocated here

Mechanical keep full valveElectrical keep full valveTemperature sensorlocated here

Mechanical keep full valveElectrical keep full valveTemperature sensorlocated here


System Description: Graphical Representation

D

C

B

A

A P S R =

1 7 5 m

D ew ar

In te rc o n ne c t V a lv e s , 3

A P S L N D S

M K F V alv e , ty p . 8

V en t o u td o o rs

D ew ar D ew ar

D ew ar

D u al

R e lie fs, 4

A u to -F ill, 4

ACT M arch 2001

A u x illa ry

E K F V alv e , ty p . 8

V en t o u td o o rs =

In te r-S ec tio n ,

B ay o n e t c o u p led ,

F le x S e c tio n =

ty p . = 3

L egend : M K F = M echan ical K eep Fu ll va lve E K F = E lectric al K eep Fu ll va lve T T = T em peratu re T ran sducer


System Description: Interconnect ValvesThe modules are joined by pneumatic interconnect valves. This allows an alternative source of LN2 for a Module should its own 3000 gallon dewar run low. The interconnect valves are between Modules A-B, B-C, C-D

Interconnect valve


System Description: Dewar and Drop Valves A pair of manual and pneumatic valves connect the 3000 gallon dewar supply to the

distribution line circling the storage ring mezzanine. Each truck lock also contains an LN2 fill station for experimental dewars. The fill stations are isolated from the main dewar by a manual shut off valve.

Manual shut off valve for fill stations

Manual isolation valve for LNDS

Pneumatic Dewar valve for LNDS

Pneumatic User Drop valve

Compressed Air Line for pneumatic valve operation

The LNDS supplies liquid nitrogen each ID beamline. The User Drop valve is a pneumatic valve used to control the flow of LN2 to the beamline. Components and connections to each drop vary with user need.


User Drop Valve

Temperature sensorMonitors line temperature to determine if liquid is present.

Mechanical float keep full valve Vents gas to keep liquid in the line.

Electrical keep full valve (used only as a back-up)

Distribution Line

System Description: Keep Full System

User Drop Line

The lines are kept full via mechanical float Keep Full valves (one on either side of each module) that vent boil off gas thus keeping liquid in the line. As a back up, electrical keep full valves are adjacent to the mechanical valves.


System Description: Pneumatic Valve Position

Position IndicatorOpen Limit Switch

Shown OPEN

100% (open)

0% (closed)

The pneumatic valves have two limit switches used to communicate their position (open or closed) to the programmable logic controllers (PLCs) that monitor the system. A 0 – 100% position indicator can be used to visually indicate if a valve is opened or closed.

Close Limit Switch


Manual Control Panel Each module has a manual control panel

located in a rack on the storage ring mezzanine. These controls are just downstream of the cross over piping from each truck lock area to the LN2 distribution line circling the storage ring mezzanine. These racks are designated:

7-ID-AR-RR02

15-ID-AR-RR02

23-ID-AR-RR02

34-ID-AR-RR02


Manual Control Panel: Valves All pneumatic valves for a module can be

operated from its control panel. All valves capable of being controlled have a three-position toggle switch with positions labeled

OPEN - CLOSE - AUTO

Each valve can be opened or closed by placing the switch in the appropriate position. Valve position is indicated on the panel by either a green (open) or red (closed) LED.

Only those valves whose toggle switches have been placed in the AUTO position can be remotely operated. Remote operation can be controlled by the touch panel screen or via an EPICS control screen run on a PC or UNIX workstation.

Operation in manual mode is restricted by the LNDS System Manager.


Manual Control Panel: 24VDC Power Supplies

Each module has a PLC (programmable logic controller). It is powered by a 24VDC power supply. The voltage and current meters are on the left hand side of the control panel.

A second 24VDC power supply provides power to the valve solenoids, position limit switches, etc. The voltage and current meters are on the right hand side of the control panel.

The voltage for both should read 20 VDC to 24VDC. The current will vary depending upon the devices activated.

Controls Power SupplyVoltage and Current

Field Device Power SupplyVoltage and Current


Manual Control Panel: LOVE Controllers Modules A, B, and C each have three

thermocouples which monitor the temperature throughout their distribution lines; the D module has four. They are located at either end of each module and at its center. The fourth thermocouple for Module D measures the temperature at the very end of the LNDS.

LOVE controllers on the control panel monitor and display the thermocouple temperature readings. These readings are used to indicate that there is liquid nitrogen within the line. If the reading is –155 °C or colder, liquid nitrogen is present.

The temperature at each electronic Keep Full (KF) valve is monitored and will read -60 °C if there is liquid in the main line. Alarm points are set to report if the system is warming up.

LOVE controllers on the control panel also display the pressure and level for its 3000 gallon dewar. Dewar pressures range from 30 - 40 psi. Dewar levels are displayed in “Inches of H20” and are scaled from zero (completely empty) to 100 (full). Alarm points are set at 17 inches of H20 to report low levels.

1 - Upstream line temperature2 - Center line temperature3 - Downstream line temperature

Dewar Pressure (PSI)Dewar Level (In of H20)

1 - Upstream KF temperature2 - Downstream KF temperature


Manual Control Panel: Touch Screen Display A touch screen display located at

the top of the Manual Control Panel is the primary control device for any LNDS module.

Three different screens display all relevant information regarding the system. Normally, a graphical representation of the module is displayed. This STATUS SCREEN provides the same information as the LEDs on the control panel and values as displayed on the LOVE controllers. It does not contain any control functions.


Manual Control Panel: Touch Screen DisplayAdministrative

By touching the area marked “GO TO ADMIN SCREEN”, a new screen is displayed which requires a password. (The System Manager and designee use this screen to set the administrative restrictions.)

Pressing “GO TO ADMIN SCREEN” yields touch Pad Screen

Type the correct password, press ENT and then press “GOTO ADMIN SCREEN” for access.


Manual Control Panel: Touch Screen Display Administrative

When the correct password is entered, a screen appears that allows administrative selection of which valves can be controlled via the touch screen and/or EPICS.

If the ENABLE DEWAR is not granted, the Dewar valve cannot be remotely controlled.

If GLOBAL ENABLE is not given, no valves in the module can be remotely controlled.

Individual valves can be remotely controlled when the proper permit is granted by pressing the ENABLE VALVE OPERATION buttons. Permits are shown by a green indicator light.

By touching the area marked “GO TO OPERATIONS SCREEN”, the operation screen appears.


Manual Control Panel: Touch Screen Display Operation

The User Drop valves can be operated from the OPERATIONS screen provided that the switch on the control panel controlling the valve is in the AUTO position and that ENABLE VALVE OPERATION permit has been granted by the LNDS System Manager to allow remote operation of that valve. Remote control of these valves via EPICS requires that the same conditions be met.


Remote Control: EPICS

Remote control and monitoring of the LNDS is achieved through EPICS display screens.

XFD-Display.adl is the main control screen used by the Floor Coordinators. From this screen there is a button used to access LNDS_Top.adl.

Click here for LNDS_Top.adl


Remote Control: EPICS The LNDS_Top.adl screen uses EPICS process variables (PVs) to display the status of

all four modules. Green, yellow and red are used to denote the status of valves, pressures, temperatures and level readings.

Usage Rate / 10 Min intervals are shown at the bottom. A FC has the ability to set a “normal” use rate to compare to and to trigger an alarm when it is exceeded.

Open User Drop valvesOpen Keep Full valvesOpen Dewar valvesClosed Interconnect Valves

Closed User Drop valvesClosed Keep Full valvesClosed Dewar valvesOpen Interconnect Valves

Unknown condition or Fault:-Temperature out of range-Pressure too high/low-Dewar level too low

Use Rate for each module

Average Use Rate setting

User Drop ValvesInterconnect Valve

Dewar Valve

Temperaturereadings

Dewar LevelDewar Pressure

LNDS_Module*.adl control screens


Remote Control: EPICSUse Rates

Abnormally high use rates can be detected when their value exceeds the estimated consumption (in IN of H20) set by the floor coordinator. An overly large use rate can imply a leak in the distribution line.

Values of a use rate < 0.3 are attributable to normal fluctuations. Values of a use rate > 0.3 and < 0.5 imply that 1 user is drawing LN2 from the module. Values of a use rate > 0.5 and < 0.9 imply that 2 users are drawing LN2 from the module. Values of a use rate > 1.0 and < 1.4 imply that 3 users are drawing LN2 from the module. Values of a use rate > 1.5 and < 1.9 imply that 4 users are drawing LN2 from the module.

Because of the nature of the user’s draw of LN2 it is unlikely that one would observe use rates greater than (0.5 * Number of Users allowed to open their Drop Valve). Consequently, alarm points are set depending upon the number of users on a module.

Implies 1 ~ 2 beamlines drawing LN2 from the system

Conservatively set for 4 beamlines connected to this LNDS module.


Remote Control: EPICSAlarm Conditions

Dewar pressure out of range (<28 or >75) Dewar level low (<18”) Line temperature warm (>-155 °C) Use rate out of range. (>EST. IOW)

Module A, Dewar Level Low alarm

When these ranges are exceeded, the EPICS PVs display the fault condition in red. Also, an email page will be sent to the 0101 pager and the LNDS System Manager.


Remote Control: EPICS Valve Control

LNDS_ModuleX.adl (X=A, B, C, or D) are the EPICS control screens each module. They represent the system graphically and are the displays from which the pneumatic valves can be controlled remotely. REMEMBER: the only valves that can be controlled remotely are those whose manual switch is in AUTO and had been allowed administratively to be operated remotely.

Interconnect valve (Normally closed)

Keep Full valve(Normally closed)

User Drop valvesDewar Valve


Remote Control: EPICS Access Status

ACCESS STATUS is used to allow or deny remote accessing of the control PVs used by EPICS. It has three states: User, System Manager, and No Control. Users can control their individual drop valve via their own computer network. The FC is provided with the ability to override the user control if system problems warrant. Remember, though, valve operation from EPICS can be over-ridden via the manual control panel at any time. Any valve switched out of the AUTO position into the OPEN or CLOSED position is no longer controlled through EPICS.

Click to change Access Status

NOTE: When Access Status is changed, Control Access to ALL modules is changed.


Remote Control: PLC monitoring control

Along with the EPICS PVs, the PLCs monitor the readings from the LNDS sensors. The PLCs have been programmed to automatically close valves in order to protect the system from damage. EPICS alarm points are set higher than the values at which the PLCs will act. The reason for this is to allow the Floor Coordinator time to react to the situation and take precautionary steps to isolate the problem.

The PLC for the individual modules are programmed to take the following actions:

Close Dewar valve if the Dewar Pressure is > 85 psi. Close Dewar valve if the Dewar Pressure is < 20 psi. Close All User Drop valves if the Distribution Line Temperature is > -150 °C

These conditions can be overridden via the manual controls. They should not be overridden without first contacting the LNDS System Manager or their designee.


Remote Control: Data Verification

There are times when the information displayed on EPICS does not seem to be consistent with normal operations of the LNDS. For example, a temperature reading has been observed as

TS-C3 = - 200

The actual temperature of liquid nitrogen is -196 °C, so this reading should be considered suspect. Readings like this sometimes occur when there are network problems. If there is ever a question regarding the validity of the information on the EPICS screens, the Manual Control Panel should be checked directly.


Alarm ResponseThe EPICS controls software is programmed to alarm if certain PVs report values outside of the expected operational range. If an alarm occurs the LNDS_Top.adl screen should be consulted for an overview of the system. On occasion alarms are caused by problems with the EPICS PV gateways. Regardless, floor coordinators should always determine the cause of any LNDS alarm.

If any TEMPERATURE reading is in alarm it is possible that there is insufficient liquid within the distribution line for that module.

If any PRESSURE reading is in alarm it is possible that there is too little or too much pressure within the system to operate properly.

If any DEWAR LEVEL reading is in alarm this means that there is insufficient liquid in the 3000 gallon dewar for that module.


Alarm Response: TemperatureThe temperature readings fluctuate throughout the day. If a temperature reading is higher than -155 °C, the EPICS software will put a red box around the alarming PV on the LNDS_Top.adl screen. It will also send out an email page. For example:

**LNDS ALARM** D:TEMP3 = -154.0 (01/20 00:15)

In this example, the temperature reading TS-D3 temporarily spiked at 00:15 hrs and triggered an alarm, sending out an email page to 0101 and the LNDS System Manager. When the temperature reading dropped below -155 °C the box around the corresponding PV changed from red to green.


Alarm Response: TemperatureIf any distribution line temperature reading within a module is higher than -155 °C it could mean that there is insufficient liquid within the line. Record the Dewar valve position, the Dewar Pressure, and the Dewar level in the Floor Coordinator shift log.

If Dewar Valve : Open

Dewar Pressure: 28 psi < (Reading) < 75 psi

Dewar Level : >17 Inches of H20

Temperature in alarm for more than 5 minutes

Then Close the Dewar Valve for the module and open the Interconnect valve for the

adjacent module with the greater Dewar Level.

As shown in the previous slide, the system can revert to normal operating temperatures within a few minutes.

Remember, if the temperature rises above -150 °C the PLC will automatically close all of the User Drop valves. If this occurs, close the Dewar valve and open the appropriate interconnect valve IMMEDIATELY.

If the conditions above are not met, contact the LNDS System Manager.


Alarm Response: PressureThe EPICS controls software is set to alarm in an overpressure or underpressure situation. If the system alarms, check the Dewar valve position, the Dewar Pressure, and the Dewar level.

OVERPRESSURE CONDITION


Dewar Pressure: (Reading) > 75 psi




UNDERPRESSURE CONDITION


Dewar Pressure: (Reading) < 24 psi




Pressure values can drop appreciably ( <28 psi ) when several Users are drawing liquid nitrogen from the system at the same time. If you notice the pressure dropping consult the Usage rate and see that the pressure returns to normal operating conditions after 10-20 minutes.


Alarm Response: Dewar LevelThe EPICS controls software is set to alarm if the Dewar Level drops below 17 inches of H20. If the Dewar level in a module alarms, close the Dewar valve, and open the interconnect valve of the adjacent module which has the greater level.

The LNDS is on a three day per week fill schedule: Mondays, Wednesdays, and Fridays. The liquid nitrogen deliveries typically occur before 12 noon.

Since each of the 3000 gallon Dewars will report a low level alarm at 17 inches of liquid, this means that each Dewar only has roughly 80 inches of liquid for use. During peak consumption the LNDS loses 25 inches of liquid per Dewar per day.

Consider an 8:00 a.m. Friday morning fill. At 8:00 a.m. Monday morning there will be roughly 25 inches of liquid left in a particular module. If this is the case for all of the modules, there is insufficient liquid in the system to last one more day. A fill of the entire system is required by roughly noon, otherwise an emergency delivery needs to be initiated. If you suspect that the LNDS is running low, contact the LNDS System Manager.

Fill to: 100 inches of liquid+24 hours 75 inches of liquid+24 hours 50 inches of liquid+24 hours 25 inches of liquidALARM 17 inches of liquid

Liquid Nitrogen Distribution System

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