**DES Lab A LN2 Test**

**Operating Procedures**

+-------+--------------+-----------------------+----------+----------+
| **    | ## Date      | **Description**       | **Or     | **       |
| Rev** |              |                       | iginated | Approved |
|       |              |                       | by**     | by**     |
+-------+--------------+-----------------------+----------+----------+
| None  | Aug 7, 2008  | Original issue        | T. Tope  |          |
|       |              |                       |          |          |
|       |              |                       | H. Cease |          |
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|       |              |                       |          |          |
+-------+--------------+-----------------------+----------+----------+
|       |              |                       |          |          |
+-------+--------------+-----------------------+----------+----------+
|       |              |                       |          |          |
+-------+--------------+-----------------------+----------+----------+
|       |              |                       |          |          |
+-------+--------------+-----------------------+----------+----------+

Reviewed by: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

Date: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_

**DES Lab A LN2 Test**

**Operating Procedures**

**Table of Contents**

1.0 Introduction x

2.0 Flow schematic x

3.0 Required Training Prior to Operating the System x

4.0 Fill Procedure x

5.0 Drain Procedure x

6.0 Heat Exchanger Cool Down Procedure x

7.0 Liquid Circulation Start up x

8.0 Abnormal Conditions Procedures x

**DES Lab A LN2 Test**

**Operating Procedures**

**1.0 Introduction**

The Lab A LN2 System is used to perform preliminary tests of the cooling
system and to cool the Multi-CCD Test Vessel. The MCCDTV is a prototype
camera vessel for the Dark Energy Survey Camera. The LN2 reservoir and
valvebox are located outside lab A. A triple jacketed hose that contains
supply, return and vacuum jacket is used a transfer line from the valve
box to the heat exchanger inside Lab A. The heat exchanger is a simple
tube heat exchanger and is used to cool the MCCDTV.

**2.0 Flow Schematic**

The flow schematic for the cryostat is shown in Figure 2.1. The flow
schematic is also available at
<http://des-docdb.fnal.gov:8080/cgi-bin/ShowDocument?docid=1537> as
"Process and Instrument Diagram - ME-436389REVA". Valves and instruments
are referenced by number in the operating
procedures.![](media/image2.png){width="5.626388888888889in"
height="4.372916666666667in"}

**Figure 2.1:** DECAM Lab A LN2 test flow schematic.

**3.0 Required Training Prior to Operating the System**

A general overview of the Lab A LN2 Test system and familiarity with the
FESHM chapters are required prior to operating the system. A general
overview can be obtained with on the job training and reviewing all of
the documents associated with the cryogenic safety review which can be
obtained at
<http://des-docdb.fnal.gov:8080/cgi-bin/ShowDocument?docid=1537> or near
the Lab A LN2 Test controls desk.

As described in FESHM 5032 "Cryogenic personnel should attend the
Fermilab safety courses, \"Oxygen Deficiency Hazards,\" \"Cryogenic
Safety\" and \"Pressurized Gas Safety\" or their equivalents.  Other
courses, as described in Chapters 4010 and 4030, may also be
appropriate.  General training in cryogenic principles may also be
beneficial, particularly to personnel involved in operations."

FESHM 5031, Pressure Vessels, includes a general description of what
requirements are expected of a system that contains a pressure vessel.
The operator should be familiar with the information contained within
FESHM 5031.

FESHM 5101, **Personal Protective Equipment (PPE)**, outlines protective
equipment needed while working with cryogens. Cryogenic gloves and a
full face shield shall be worn at all times while operating manual
valves or working around the safety relief devices. Long pants and
closed toe shoes are recommended while working with cryogenics.

Before any of the following procedures are performed, get training from
a person experienced with the complete system.

**4.0** **Fill Procedure**

The 200L Vessel is filled using 160L portable dewars. Station the 160L
dewar near the fill line on the 200L vessel. The first time the 200L
vessel is filled, two 160L dewars are needed to completely fill the
system.

Prior to performing a fill,

> Don face shield, and cryogenic gloves.
>
> Check that the 160L fill dewar is pressurized above 200psig,
>
> Attach an all metal transfer line with the proper flare fittings, and
> have wrenches available to tighten the fittings.

1)  Open fill valve MV-6204

2)  Open Fill try-cock valve MV-6208

3)  Slowly open the valve on the 160L dewar to start transferring liquid
    into the 200L vessel Note: The 200L is full when liquid vents from
    the fill try-cock valve.

4)  Slowly close the valve on the 160L dewar .

5)  Close fill valve MV-6204.

6)  Close fill try-cock valve MV-6208.

7)  Wait a few minutes, using the wrenches slowly open the flare
    fittings and remove the transfer line.

**5.0 Drain Procedure**

When the cooling system is stopped, most of the liquid drains back into
the 200L vessel. If maintenance is needed on the vessel, the liquid is
drained from the system.

> Prior to draining the dewar, don face shield, cryogenic gloves. The
> fog produced when venting the vessel is extremely cold and creates a
> low oxygen pressure area. Ensure that this operation takes place slow
> enough that a hazard is not created.

1)  Slowly open the fill try-cock valve MV-6208 to vent excess pressure
    from the 200L vessel.

2)  Slowly open valve MV-6205 and let the liquid vent from the vessel.
    MV-6208 is also used to control the pressure in the dewar and the
    venting rate.

3)  When all of the liquid has been vented, close valves MV-6205 and
    MV-6208.

**6.0 Heat Exchanger Cool Down Procedure**

This procedure is used to cool down all of the piping in the system
prior to operations. The 200L vessel is pressurized, liquid from the
vessel is then pushed thru the piping system. The boil-off gas is vented
using MV-6307. Prior to operating manual valves, don face shield, and
cryogenic gloves.

1)  Close valves MV-6307, 6208, 6205, 6204, 6310, 6302, 6303.

2)  Open valves MV-6216, 6201.

3)  Let the system pressurize to the normal operating pressure, pressure
    can be built up using heater 6102 and setting the set-point on
    TE-6211 to 100K.

4)  Slowly Open return line vent valve MV-6307 and allow the piping
    system to cool down. Approximately 20 Liters are needed to boil-off
    to cool all of the piping down.

5)  Once the system is cold, slowly open MV-6303 and close MV-6307

**7.0 Liquid Circulation Start up**

Liquid circulation can start up once the system has been pressurized and
cooled down. The pump is initially started by circulating all of the
liquid thru the bypass valve MV-6310. Once the pressure stabilizes in
the 200L vessel then liquid can slowly be circulated through the rest of
the piping system until full design flow is achieved. The heater in the
heat exchanger is not used until the full design flow is achieved. Prior
to operating manual valves, don face shield, and cryogenic gloves.

1)  Pressurize the system and cool down all of the piping using the Cool
    Down Procedure.

2)  Close valves MV-6302, 6307, Valve MV-6303 is left open ¼ turn so
    that a trapped volume in the piping system is not created

3)  Open control valve MV-6310 half way

4)  Slowly start pump 6103, increase speed until design flow rate is
    achieved. Confirm flow rate using PDI-6313 and the pump flow curve.

5)  Slowly open valve MV-6302

6)  Once the pressure in the vessel has stabilized, slowly open valve
    MV-6303

7)  Adjust flow rate to the design flow rate using control valve MV-6310
    and confirming the flow rate using FT-6301 and PDI-6313.

8)  Once the flow rate and pressure in the vessel are stable, the heat
    exchanger can be operated.

**8.0 Abnormal Conditions Procedures**

Small leak, Alert other people, Evacuate area,

Large Leak, Alert other people, Evacuate area, call safety -3131

Dewar failure, Alert other people, Evacuate area, call safety -3131