**DES Lab A LN2 Test**

**Piping System Engineering Note**

+-------+--------------+-----------------------+----------+----------+
| **    | ## Date      | **Description**       | **Or     | **       |
| Rev** |              |                       | iginated | Approved |
|       |              |                       | by**     | by**     |
+-------+--------------+-----------------------+----------+----------+
| None  | Aug 11, 2008 | Original issue        | T. Tope  |          |
|       |              |                       |          |          |
|       |              |                       | H. Cease |          |
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|       |              |                       |          |          |
+-------+--------------+-----------------------+----------+----------+
|       |              |                       |          |          |
+-------+--------------+-----------------------+----------+----------+
|       |              |                       |          |          |
+-------+--------------+-----------------------+----------+----------+
|       |              |                       |          |          |
+-------+--------------+-----------------------+----------+----------+

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

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

**DES Lab A LN2 Test**

**Piping System Engineering Note**

**Table of Contents**

1.0 Introduction 3

2.0 Flow schematic 3

3.0 Design codes and evaluation criteria 5

4.0 Materials 5

5.0 Piping design and analysis 5

6.0 Pressure relief system 17

7.0 Welding and inspection 17

8.0 Pressure testing 17

9.0 Appendix 17

**DES Lab A LN2 Test**

**Piping System Engineering Note**

1.  **Introduction**

This document constitutes the Piping System Engineering Note for the
cryogenic piping associated with the DES Lab A LN2 test.

The pipe descriptions and a table summary of the operating parameters
are shown in Table 1.1.

+----------------------------+-----+-------+-------+----+----+------+
| **Table 1.1: Cryogenic     |     |       |       |    |    |      |
| piping description and     |     |       |       |    |    |      |
| summary**                  |     |       |       |    |    |      |
+----------------------------+-----+-------+-------+----+----+------+
| **Description**            | **F | *     | *     | ** | ** | **Te |
|                            | lui | *OD** | *ID** | P~ | P~ | mp** |
|                            | d** |       |       | op | ma |      |
|                            |     | **(   | **(   | er | x~ | **(  |
|                            |     | in)** | in)** | at | (p | K)** |
|                            |     |       |       | in | si |      |
|                            |     |       |       | g~ | d) |      |
|                            |     |       |       | (p | ** |      |
|                            |     |       |       | si |    |      |
|                            |     |       |       | d) |    |      |
|                            |     |       |       | ** |    |      |
+----------------------------+-----+-------+-------+----+----+------+
| U-tube LN2 piping          | LN2 | 1.315 | 1.049 | 1  | 1  | 100  |
|                            |     |       |       | 15 | 65 |      |
| 1 in. SCH 40 pipe          |     |       |       |    |    |      |
|                            |     |       |       |    |    |      |
| (vacuum jacketed)          |     |       |       |    |    |      |
+----------------------------+-----+-------+-------+----+----+------+
| Drain Line, Fill Trycock   | LN2 | 0.750 | 0.652 | 1  | 1  | 100  |
| Line, and Fill Line for    |     |       |       | 00 | 50 |      |
| the DES pressure vessel    |     |       |       |    |    |      |
|                            |     |       |       |    |    |      |
| ¾ in. OD tube              |     |       |       |    |    |      |
+----------------------------+-----+-------+-------+----+----+------+
| Vent line                  | GN2 | 0.250 | 0.180 | 1  | 1  | \>   |
|                            |     |       |       | 00 | 50 | 100  |
+----------------------------+-----+-------+-------+----+----+------+
| Cooling Ring               | LN2 | 1.050 | 0.884 | 1  | 1  | 100  |
|                            |     |       |       | 00 | 50 |      |
| ¾ in. SCH 10 pipe          |     |       |       |    |    |      |
+----------------------------+-----+-------+-------+----+----+------+
| Cooling Ring               | LN2 | 0     | 0.666 | 1  | 1  | 100  |
|                            |     | .7500 |       | 00 | 50 |      |
| ¾ in. OD tube              |     |       |       |    |    |      |
+----------------------------+-----+-------+-------+----+----+------+
| Valve Box                  | LN2 | \*    | \*\*  | 1  | 1  | 100  |
|                            |     |       |       | 00 | 50 |      |
| (numerous components)      |     |       |       |    |    |      |
+----------------------------+-----+-------+-------+----+----+------+

\*The largest diameter piece of piping in the valve box is 1 inch pipe.

\*\*The thinnest pipe wall thickness in the valve box is 0.065 inches.

**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".

![](media/image2.png){width="5.626388888888889in"
height="4.372916666666667in"}

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

A schematic of the piping layout at Lab A is shown in figure 2.2 The
200L vessel, instrument lines, all relief valves, and the valve box are
located outside at Lab A. The triple jacket hose is used as a transfer
line to the camera heat exchanger which is located inside Lab A under
the dome.

![](media/image3.png){width="5.852777777777778in"
height="4.533333333333333in"}

**Figure 2.2:** DECAM Lab A LN2 test piping schematic.

**3.0 Design codes and evaluation criteria**

The DES Lab A LN2 Test piping must meet all of the requirements of
Section 5031.1 of the Fermilab ES&H Manual. This section states that
piping systems containing cryogenic fluids fall under the category of
Normal Fluid Service and shall adhere to the requirements of the ASME
Process Piping Code B31.3.

**4.0** **Materials**

The piping is fabricated from 304/304L and 316/316L stainless steel tube
and pipe. The allowable stress used in this document is 16,700 psi,
which is the lowest value listed for these pipe and tube materials in
B31.3 Appendix A.

The LN2 piping will be operated at 100 K. This is above the minimum
temperature listed for 304/316 stainless steel pipe or tube (19 K).
According to Table 323.2.2 of the Code, impact testing is not required
for these austenitic stainless steels. However, Table 323.2.2 does
require impact testing of the weld metal and heat affected zone. Except
as stated in Table 323.2.2 Note (6) where impact testing is not required
when the minimum obtainable Charpy specimen has a width along the notch
of less than 2.5 mm (0.098 in). The 1 inch SCH 40 piping that comprises
the inner line of the U-tube assembly has a wall thickness of 0.133
inches and is the only piping in the system with a wall thickness
greater than 0.098 in. See section 7.0 for comments with respect to
impact testing.

**5.0 Piping design and analysis**

A schematic of the piping attached to the vessel is shown in Figure 5.1.
The valve box piping that attaches to the vessel is shown in Figure 5.2.
A flexible vacuum jacketed hose connects the cooling ring shown in
Figure 5.3 to the valve box piping.

![](media/image4.jpeg){width="3.5479166666666666in" height="8.25in"}

![](media/image5.jpeg){width="5.769444444444445in"
height="8.627777777777778in"}

![](media/image6.jpeg){width="5.8125in" height="9.0in"}

[http://www](http://www/)-admscad.fnal.gov/MSDMain/cgi-bin/TP_PPDifind-web.pl

The minimum thickness of the pipes is evaluated using the procedures in
304.1.2(a) of ASME B31.3. The minimum tube thickness for seamless or
longitudinally welded piping for t\<D/6 is given by:

$$t = \frac{\text{PD}}{2(\text{SEW} + \text{PY})}\ $$

where: *t* = wall thickness, (*t* mfg is the manufacturers minimum wall
thickness while *t* req'd is the thickness required by the above
equation)

*P* = internal design pressure

*D* = outside diameter (manufacturers nominal value is used)

*S* = allowable stress from table A-1

*E* = quality factor from table A-1A or A-1B = 0.8 (worst case)

*W* = weld joint strength reduction factor = 1

*Y* = coefficient from Table 304.1.1 = 0.4

Table 5.1 summarizes the results of the wall thickness calculation.

+--------------------+-----+------+------+------+------+------+-------+
| **Table 5.1.       |     |      |      |      |      |      |       |
| Cryogenic piping   |     |      |      |      |      |      |       |
| parameters**       |     |      |      |      |      |      |       |
+--------------------+-----+------+------+------+------+------+-------+
| **Pipe / Tube**    | *   | ***  | ***  | ***  | *    | *    | **M   |
|                    | **P | D*** | S*** | E*** | **t* | **t* | AWP** |
|                    | *** |      |      |      | req  | mfg  |       |
|                    |     | **(i | *    |      | 'd** | min  | **(ps |
|                    | *   | n)** | *(ps |      |      | (i   | id)** |
|                    | *(p |      | i)** |      | **(i | n)** |       |
|                    | sid |      |      |      | n)** |      |       |
|                    | )** |      |      |      |      |      |       |
+--------------------+-----+------+------+------+------+------+-------+
| U-tube LN2 piping  | 165 | 1    | 16   | 0.8  | 0    | 0    | 3,037 |
|                    |     | .315 | ,700 |      | .007 | .116 |       |
+--------------------+-----+------+------+------+------+------+-------+
| Drain Line, Fill   | 150 | 0    | 16   | 0.8  | 0    | 0    | 1,645 |
| Trycock Line, and  |     | .750 | ,700 |      | .004 | .044 |       |
| Fill Line for the  |     |      |      |      |      |      |       |
| DES pressure       |     |      |      |      |      |      |       |
| vessel             |     |      |      |      |      |      |       |
+--------------------+-----+------+------+------+------+------+-------+
| Vent Line          | 150 | 0    | 16   | 0.8  | 0    | 0.   | 3,744 |
|                    |     | .250 | ,700 |      | .001 | 0315 |       |
+--------------------+-----+------+------+------+------+------+-------+
| Cooling Loop       | 150 | 1    | 16   | 0.8  | 0    | 0.   | 1,956 |
|                    |     | .050 | ,700 |      | .006 | 0726 |       |
+--------------------+-----+------+------+------+------+------+-------+
| Cooling Loop       | 150 | 0    | 16   | 0.8  | 0    | 0.   | 1,403 |
|                    |     | .750 | ,700 |      | .004 | 0378 |       |
+--------------------+-----+------+------+------+------+------+-------+
| Valve box\         | 150 | 1    | 16   | 0.8  | 0    | 0    | 1,375 |
| (worst case OD and |     | .315 | ,700 |      | .007 | .065 |       |
| wall THK)          |     |      |      |      |      |      |       |
+--------------------+-----+------+------+------+------+------+-------+

In the above six cases the manufacturer's minimum wall thickness of the
piping is greater than the minimum thickness required by ASME B31.3.

The "unlisted components" installed in the piping system as defined in
B31.3 Section 304.7.2 are shown in Table 5.2.

  ------------------- ----------------- ----------- ---------- -----------------
  **Table 5.2.                                                 
  Unlisted piping                                              
  components.**                                                

  *Component*         *Source*          *Pressure   *System    *Comment*
                                        rating      Design     
                                        \[psig\]*   Pressure   
                                                    (psig)*    

  Vacuum jacketed     Duraflex part \#  150^(a)^    150        \-\-\--
  flex hose           D010TVJAVCR-720                          

  Bayonet             PHPK, part \#     150^(b)^    150        \-\-\--
                      PBA-10                                   

  See the valve and                                            
  instrument list for                                          
  other components.                                            
  ------------------- ----------------- ----------- ---------- -----------------

> \(a\)
> http://des-docdb.fnal.gov:8080/cgi-bin/RetrieveFile?docid=1537&version=6&filename=Fermi_Triple_Jacketed_wgs.pdf

(b) PHPK literature states that "All bayonets have been computer
    analyzed to meet the ANSI/ASME B31.3 piping code requirements....".

The flexibility of the U-tube piping was analyzed using ANSYS. The model
boundary conditions and results are summarized in Figures 5.2 and 5.3.

The thermal shrinkage was taken to be 321 x 10^-5^ *L/L* for 304/316
Stainless (B31.3 Table C-1). The modulus of elasticity of 304 Stainless
was input as 30.3 x 10^6^ psi (B31. Table C-6) along with a Poisson's
Ratio of 0.30 (B31.3 para 319.3.3).

The model is comprised of ANSYS PIPE 16 (straight), and PIPE 18 (elbow)
elements in which ANSYS calculates flexibility and stress
intensification per B31.1. The stress intensification factors for B31.3
are the same as for B31.1.

As a check of the FEA model, a simple model consisting of a section of
straight pipe was analyzed. The pipe was anchored at both ends and
cooled from room temperature to liquid nitrogen temperature. The stress
reported by the FEA model matched the result obtained by multiplying the
unit thermal strain by the modulus of elasticity.

Per B31.3 Appendix P, the operating stress is computed using equation
(P17a)

$$S_{o} = \sqrt{\left( \left| S_{a} \right| + S_{b} \right)^{2} + 4S_{t}^{2}}$$

where the axial (*S~a~*), bending (*S*~b~), and torsional (*S~t~*)
stresses are combined and compared to the allowable stress *S~oA~* in
para. P302.3.5(d) where

$S_{\text{oA}} = 1\text{.}\text{25}f\left( S_{c} + S_{h} \right)$.

*S~c~* is the basic allowable stress at the minimum metal temperature
expected during the displacement cycle under analysis and *S~h~* is the
basic allowable stress at the maximum metal temperature expected during
the displacement cycle under analysis. Both *S~c~* and *S~h~* were taken
to be 16,700 psi. The stress reduction factor *f* was taken to be 1.0
because this system will see less than 1,000 cycles in its lifetime.

$$S_{\text{oA}} = 1\text{.}\text{25}´1\text{.}0´\left( \text{16},\text{700} + \text{16},\text{700} \right) = \text{41},\text{750}\text{psi}$$

A macro (available in the appendix) was used to retrieve *S~a~*, *S~b~*,
and *S~t~* from ANSYS and then compute the combined stress. The peak
operating stress for the Supply U-tube was found to be 5,280 psi for the
cold case (thermal shrinkage + 165 psid) and 295 psi for the warm case
(165 psid loading only). The peak operating stress for the Return U-tube
was found to be 6,826 psi for the cold case (thermal shrinkage + 165
psid) and 295 psi for the warm case (165 psid loading only).

Thus the operating stress range for both U-tubes is only a few thousand
psi and does not exceed the allowable operating stress limit. These
stresses are well below the 16,700 psi limit for the U-tube piping
components.

The Fill, Drain, and Trycock lines were also analyzed using an FEA model
to investigate the thermal stress. In the FEA model these lines were
modeled as fixed to their respective VCR fittings on the top flange and
to a clamp attached to the Unistrut frame (see Figure 5.1). Figures 5.4
thru 5.6 show the model results. Application of B31.3 equation P17a
resulted in a peak stress of 6,254 psi for the Fill Line, 8,353 psi for
the Drain Line, and 7,770 psi for the Fill Trycock line. Thus the stress
in each line due to thermal shrinkage and internal pressure is less than
the 16,700 psi allowable.

![](media/image7.jpeg){width="5.761023622047244in"
height="4.45in"}![](media/image8.png){width="5.571653543307087in"
height="4.301574803149606in"}

![](media/image9.jpeg){width="5.433333333333334in"
height="4.190277777777778in"}![](media/image10.jpeg){width="5.433333333333334in"
height="4.198611111111111in"}

![](media/image11.jpeg){width="5.3125in" height="4.096527777777778in"}

The Cooling Ring piping bends (Figure 5.3) are analyzed per para.
304.2.1 of the Code. The minimum required thickness is given by:

$$t = \frac{\text{PD}}{2((\frac{\text{SEW}}{I}) + \text{PY})}\ $$

where: *t* = wall thickness

*P* = internal design pressure, 150 psid

*D* = outside diameter, 1.050 in.

*S* = allowable stress from table A-1, 16,700 psi for 304 S.S.

*E* = quality factor from table A-1A or A-1B = 0.8 (worst case)

*W* = weld joint strength reduction factor = 1

*Y* = coefficient from Table 304.1.1 = 0.4

*I* = factor for location in pipe bend: intrados, extrados and
centerline

The following equations are used to determine *I* at the three
locations:

at the intrados:
$I = \frac{4(\frac{R_{1}}{D}) - 1}{4(\frac{R_{1}}{D}) - 2}\ $

at the extrados:
$I = \frac{4(\frac{R_{1}}{D}) + 1}{4(\frac{R_{1}}{D}) + 2}\ $

at the centerline: *I* = 1.0

*R~1~* = bend radius of the tubing, 8.225 in.

The results are as follows:

*t*(in) for 8.225 in. radius: at intrados = 0.0061; extrados = 0.0057;
centerline = 0.0059 (same as straight tube)

The bent pipe has a minimum wall thickness of 0.0726 inches so this
requirement is satisfied.

**6.0 Pressure relief system**

  --------------------------- ------------- ---------------- --------------
  **Table 6.1: DES Lab A LN2                                 
  Test relief settings.**                                    

  *Circuit*                   *Design       *Relief setting* *Relief valve
                              pressure*                      ID*

  Drain line                  150 psid      150 psig         SV-6213

  Fill trycock line           150 psid      150 psig         SV-6213

  Fill line                   150 psid      150 psig         SV-6200-LN,
                                                             SV-6213

  Return U-tube               165 psid      150 psig         SV-6213

  Supply U-tube               165 psid      150 psig         SV-6213
  --------------------------- ------------- ---------------- --------------

**7.0 Welding and inspection**

According to B31.3 Section 341, all piping in Normal Fluid Service shall
be examined. All welding was performed by Lenny Harbacek whose stainless
steel qualification is included in the Appendix. Eight butt welds were
radiographed and the results are available as an attachement. The system
contains 70 butt welds.

B31.3 requires the welding procedure for austenitic stainless steels to
be qualified by impact tests of the weld metal and heat affected zone
for wall thicknesses greater than 0.098 inch when used at liquid
nitrogen temperatures. The 1" SCH 40 U-tube piping has a wall thickness
of 0.133 inches. Fermilab does not have a qualified welding procedure
for use of austenitic stainless steels at liquid nitrogen temperatures.
However, the stress in this piping is far below the allowable stress.
Low stress reduces the likelihood of brittle failure in the heat
affected area. The ASME pressure vessel code recognizes the suitability
of 304/304L & 316/316L for use at liquid nitrogen temperatures. In
Section VIII Division 1, paragraph UHA-51(d)(1) exempts 304/304L and
316/316L from impact testing for both the base metals and the heat
affected zones.

**8.0 Pressure testing**

The piping system will be pressure tested in accordance with Section
5034 of the Fermilab ES&H Manual and 345.5 of the Code. The test
pressure is 110% of the design pressure which is 1.1 x 150 = 165 psig.

**9.0 Appendix**

![](media/image12.jpeg){width="5.884722222222222in"
height="7.752777777777778in"}

Figure A-1: ANSYS macro used to compute operating stress.

![](media/image13.jpeg){width="5.998611111111111in"
height="7.840972222222222in"}

Figure A-2: Leonard Harbacek's welding qualification for stainless
steel.