Table of Contents s279

Fuel Tank MAE 435 Final Report 4/22/2014

Albert Ochagavia Josh Harris Pithan Rojanavongse John Alexander 2

Table of Contents Table of Contents...... 2

List of Figures...... 3

Abstract...... 4

Introduction...... 5

1...... Instruments/Devices ...... 7

1.1 Refueling Methods 7

1.2 Gauges & Sensors 9

1.3 Shut-off/Relief Valves 10

1.4 Other Part 10

2...... Layer Design ...... 11

2.1 Inner Shell Thickness 11

2.2 Insulation Thickness 11

3...... Tank Design ...... 12

3.1 Inner tank Shell 12

3.2 Ullage Tank 14

3.3 Insulation Layer 15

3.4 Outer Tank Shell 16

3.5 Manifold 17

3.6 Overall Tank View 18 3

4 Limitations and Future Work 18

5 Gantt Chart

References...... 20 4

List of Figures:

Figure 1: Carter Fuel Dispenser Schematic...... 8 Figure 2: Carter Nozzle Schematic...... 9 Figure 3: Example Tank Fuel Schematic...... 10 Figure 4: Lower Portion of Inner Shell ...... 13 Figure 5: Top Portion of Inner Shell...... 13 Figure 6: Inner Tank Bottom Rivets...... 14 Figure 7: Rivets Sitting in Outer Tank Slots...... 14 Figure 8: Ullage Tank Attached to Tank Lid...... 15 Figure 9: Insulation Layer...... 16 Figure 10: Outer Tank Layer...... 17 Figure 11: Manifold...... 17 Figure 12: Tank Assembly...... 18 Figure 13: Full Tank View 18 5

Abstract

Liquefied natural gas (LNG) is an up and coming fuel resource that Liebherr is interested in using to fuel their T264 Mining Trucks. A LNG fuel tank will be designed to potentially replace the existing diesel fuel tank. This will be accomplished by first examining the properties and characteristics of LNG. Upon examination, it is revealed that there must be a material and insulation selection process in accordance to the properties of LNG. The material and insulation selected were A240 Type 304 Stainless Steel and Multi-layer Insulation (MLI) respectively. Possible tank designs were analyzed to meet the design specifications given by Liebherr. Liebherr requested that the space utilized be restricted to the volume enclosed by the diesel tank. There were two possible mitigation systems to be implemented in the tank design which are the use of pressure release valves and ullage tank. Our research called for the implementation of an ullage tank due to the boil-off gas produced within the tank. The pressure release valve will act as a safety measure for specific levels of pressure build up within the tank. From here we will begin modeling and optimizing the tank design in SolidWorks. The goal of the project is to provide Liebherr with a design scheme to implement LNG fuel tank technology on future mining trucks. 6

Introduction

Liquefied Natural Gas (LNG) consumption is a rising market in the United States with a growth estimate of 24.4 trillion cubic feet in 2011 to 29.5 trillion cubic feet in 2040 [1]. In the projection, vehicle use of LNG was the largest percentage of growth with an estimate of 40 billion cubic feet in 2011 rising to over 1 trillion cubic feet in 2040 [1]. The rise of LNG use as vehicle fuel suggests a more detailed investigation of LNG fuel tanks to replace the diesel tanks on the Liebherr T264 Mining Trucks. The difficulty of LNG fuel tank design lies in the shape, size, space availability, and material composition of diesel fuel tanks. LNG must be kept at a temperature of minus 160o C (minus 260o F) and is a highly flammable substance [2]. Therefore, gasoline/diesel tanks must be modified or swapped to effectively store LNG fuel. LNG powered trucks are the future of the mining vehicles market [3] with companies already committing to have all new haul trucks with LNG-electric engines by 2015-2016 [4,5]. As shown by Franklin [6] the cost of LNG is two and a half times lower than diesel prices. LNG has a cleaner environmental impact than other fossil fuels such as coal and petroleum and the new discoveries of natural gas shells in the United States guarantee its availability. Liebherr, aware of the advantages of using LNG, ordered the design of a LNG tank that fits into the T264 Liebherr mining truck. The first step in design of a LNG tank is determining the material selection of the three layers encasing the liquid. Those layers, listed from inside out, are as follows: the inner shell, the insulation, and the outer shell. The inner shell is chosen to directly deal with the primary containment of LNG while the insulation and outer shell handles the changes in outside temperature and secondary containment, respectively [2]. The selection of materials for a LNG fuel tank was crucial because LNG is kept at very low temperatures and can be subjected to high pressure. When materials for the tank were considered, it was important to know that the design of the tank must be capable of withstanding minus 160o C (minus 260o F) and be insulated to slow down LNG boil off causing high pressure within the tank [7]. A typical design of the LNG tank consists of a double-walled insulated pressure vessel that can withstand the temperatures associated with the use of LNG [8]. Insulated materials must be selected based on their high level of thermal isolation and placed between the double-walled vessel [9]. Based on the characteristics of LNG, some form of steel would be best suited for a 7

LNG fuel tank. The steel selected for a LNG fuel tank must be designed to have high strength, notch toughness, low thermal conductivity and weldability [10]. For safe operation of a LNG fuel tank for vehicles, the steel selected in the design of the tank needs to meet specific characteristics such as: good corrosion resistance, ductility, high yield strength and tensile strength [10,11]. Since there are a variety of low-temperature steels available, the advantages of each must be considered based on the characteristics mentioned above. Since LNG is required to be at minus 160o C (minus 260o F) and in liquid form, insulation is needed to decrease heat transfer. When evaluating insulation materials to be placed between the double-walled steel tank, low values of thermal conductivity and high values of thermal resistance are to be considered. Perlite insulation and multilayer insulation (MLI) appear to be viable options based on their thermal conductivity and low service temperature. Perlite insulation provides excellent insulation for cryogenic applications [12]. MLI has similar properties of Perlite but requires a lower thickness to achieve said values [9]. An evaluation of space follows to determine the dimensions of the LNG tank. When evaluating the tank’s shape and size, researchers [4, 5, 13] often choose a cylindrical shape to minimize critical points in the design. A thorough investigation of the space available on the T264 Truck must be undertaken to restrict the design boundaries of the LNG tank. Near the end of the research phase of the project Liebherr allowed for a more liberal use of the space available. The previous restriction of placing an LNG tank inside of the old diesel shell was scrapped and the LNG tank is now to be designed so that it may use all of the space in which the diesel tank had previously taken up. Later the tank, in its entirety, is to be modeled and a finite element analysis will be performed. Finally the entire design scheme along with model and analysis will be presented to Liebherr as a final product. 8

1. Instruments/Devices 1.1 Refueling Methods:

There were several assumptions made before choosing a specific fueling method: the temperature will adjust from the heat exchanger within the fueling facilities (indicated in the diagram below) and the outside pressure will be standardized (at atmospheric pressure). The different types of fueling methods for LNG are: pressure transfer, gravity transfer, and the fuel dispenser. The fuel dispenser will be implemented and would need a vapor hose to control the pressure while fueling the LNG storage tank. The fuel dispenser fits the design because a pressure drop can be more easily read to know when the tank is full. This characteristic follows from the use of an ullage tank that will be explained further along in the report (topic 3.2). Within the fueling dispenser method, there were two other methods which would need to be considered: the slow fill (which takes 8 hours) and the fast fill (which takes 10-20 minutes). Many different fuel dispensers were considered; however, several properties of the fuel dispenser needed to be considered. The properties considered for the fuel dispenser are: the fuel dispenser must function at cryogenic temperatures and time efficient. The most common material for the fuel dispenser was stainless steel because it is the least expensive and convenient for the scenario. Other materials such as brass could not function at low temperatures – which would render the fuel dispenser useless. By considering the important factors of fueling the LNG storage tank, two fuel dispensers were considered: the Parker & Carter couplings. Many LNG companies utilize the Parker & Carter couplings because they are the most effective couplings within the LNG industry. After considering the different specifications and schematics of each coupling, the LNG Carter coupling was chosen. The fueling rate for the Carter coupling is 50 gallons per minute and has a quicker setup time compared to the Parker couplings. The setup time for the Parker coupling takes several minutes while the Carter coupling takes only a couple of seconds. The 50E701(-1) Nozzle and 62050 Receptacle will be implemented in the LNG storage tank design. When fueling the LNG storage tanks, the Carter coupling will not require a vent line unlike the Parker coupling. The following schematics of the 50E701(-1) Nozzle and 62050 Receptacle will be implemented in the design (Figures 2 & 3) [15]. However, it is recommended that a vent line be 9 implemented on the tank design to prevent fuel loss and damage to the environment. By venting to the LNG fueling facility, both fuel loss and the effects of LNG on the environment will be minimized. The vent hose for the LNG storage tank will be the ½” Vent Hose (PN 241888) from Carter Couplings [15].

Figure 1: Fuel Dispenser JC Carter LLC LNG Couplings: User Manual [15] 10

Figure 2: Nozzle JC Carter LLC LNG Couplings: User Manual [15]

1.2 Gauges & Sensors:

Gauges and sensors need to be implemented on the LNG storage tank design to indicate the fuel, pressure, and temperature readings of the tank. There will be a total of three sensors and three gauges – each one will be utilized for a different function. Similar to the fueling couplings, the gauges and sensors must function at cryogenic temperatures to ensure accurate readings. The pressure gauge chosen from the company WIKA was the Stainless Steel Case, 212.53 [20] due to its similar use in cryogenic applications. The tank will have an emergency pressure relief valve set at 420 psi thus the gauge must have a max pressure reading of at least 450 psi. As for the temperature gauge, the minimum cryogenic temperature should be less than -162 degrees Celsius. The fuel gauge will need to indicate the fuel level to the driver. Similar to the gauges, many sensors cannot function at cryogenic temperatures. The Cryogenic ICP Pressure Sensor 102A14 will be used in our design again due to its similar use in other cryogenic situations [16]. The temperature range of the device is –196 degrees Celsius to 100 degrees Celsius; which is an ideal range for the design. The Silicon Diode CY7-SD from 11

Omega will be considered because it too is able to function in a cryogenic temperature range of 1.4 K – 475 K [19]. 1.3 Shut-off/Relief Valves: For emergency situations, a shut-off valve will be implemented in the design along with the use of relief valves for extreme pressures. There will be two pressure relief valves one set at 350 psi and the other set at 420 psi. The shut-off valve will be placed in an area that is easy to access in emergency situations.

1.4 Other Parts:

Several other parts may need to be included in the design of the tank to ensure the safety of the tank. These parts include a pressure regulator, temperature regulator, defueling valve, fuel valve, fuel connection, venting control valve, fuel check valve, and pressure check valve [18]. Other parts which contribute to processing the fuel into vehicle use may be necessary such as the vaporizer, ignition controlled solenoid valve, fuel filter, and the engine controlled solenoid valve [18]. These parts will be implemented in the design in a similar design to figure 4 [18]. 12

Figure 3: Example Tank Fuel System Schematic [18] 2.Layer Design

2.1 Determination of Thickness for Inner Pressure Vessel:

The determination of the minimum thickness for the inner pressure vessel for the LNG fuel tank is very important not only for safety reasons, but for minimizing heat transfer. The inner vessel will contain the LNG and will have to hold the pressure associated with the vapor natural gas that ensues from the boil off. The thickness is calculated based on the ASME’s Boiler and Pressure Vessel Code’s (BPVC) [23] requirements for safety factors concerning pressure vessels. We also decided on a safety factor of four in accordance with the ASME BPVC Section VIII Division 2 code [23]. Based on that safety factor, we can then calculate the minimum thickness of the vessel wall. The formula shown below was used to solve the thickness. 13 where: P = Max internal Pressure (psi) r = Internal radius (in.)

s = Ultimate tensile stress/ Safety factor (psi) E = Joint Efficiency

Knowing that P=420 psi, rinner=24 inches, s=32000/4 psi, and E=0.8, we determined that the inner vessel thickness is 1.575 inches. Since the thickness is not a nominal size for the 304 stainless steel, we designed the tank with a thickness of 1.75 inch. Once that is calculated, we can then begin to calculate the heat transfer, so that the insulation thickness can be determined.

2.2 Determination of the Thickness for the Insulation:

To determine the minimum thickness of the insulation, the maximum heat transfer in the whole system was to be calculated. Since this is a cryogenic vessel, the heat transfer calculation is a little more complex. In order to start this problem, the boil of gas rate (BOG) in units of kg/day must first be calculated. The maximum heat transfer, in watts, for the entire system is then calculated. Once the maximum heat transfer is known, we can then begin to interpolate different temperatures to calculate the minimum thickness of insulation.

We know that there is going to be convective heat transfer between the outside air and the outer surface of the tank, between the LNG and the inner tank surface and between the outer surface of the inner tank and the inner surface of the outer tank. There is also going to be radiation between the sun and the outer surface of the tank. Conductive heat transfer is also going to take place between the outer surface of the inner tank and the insulation, and between the inner surface of the outer tank and the insulation.

For our given problem the outside air temperature will be assumed to be an average of 100F over five days, since that is when the most heat transfer is going to take place. We are also going to make a couple of assumptions to simplify our problem:

 All evaporation of LNG takes place at the surface of the liquid.

 During evaporation, vapor-liquid are in equilibrium. 14

 The density and temperature of LNG remain constant during process.

Once we calculate the minimum thickness for the insulation we can then determine the outer tank thickness.

3.Tank Design

3.1 Inner Tank Shell:

The fuel tank contains an inner shell, which is the layer that is designed to be in contact with the fuel, liquefied natural gas. The material used to construct the shell is made of 304 stainless steel. The LNG tank has been developed to withstand internal pressures up to 420 psi.

The inner shell has been designed with a thickness of 1.75 inches to withstand this pressure. The inner shell is made of two different pieces that will be put together by a standardized cryogenic welding method, called Shielded Metal Arc Welding. This method is one that provides certain properties that are crucial for the tank’s design. Such properties consist of high toughness, as well as low lateral expansion and low heat transfer. A pumpless system will be assumed in the practice of conditioning prior to fueling by the fueling station or fuel supply vehicle. The conditioning maintains the LNG fuel at a saturation vapor pressure of 100 psi [22]. Heat transfer into the tank will help keep the tank pressure above 100 psi so that the engine can withdraw the fuel without a pump [22]. The overall inner structural dimensions are displayed on the images below. 15

Figure 4: Lower Portion of Inner Shell Figure 5: Top Portion of Inner Shell

The lower part of the inner shell contains four rivets designed to create both vertical and horizontal support, in order to prevent flotation problems where the inner shell would circulate, causing harmful pressures to the insulation layer. Each of the four rivets are 3 inches long, with a diameter of 2 ½ inches. These rivets have been created with the ability to pass through the insulation layer and to sit securely on the bottom of the outer shell as seen in the Figures 1 and 2 below. 16

Figure 6: Inner Tank Bottom Rivets Figure 7: Rivets Sitting in Outer Tank Slots

3.2 Ullage Tank:

The ullage tank is an empty tank space attached to the bottom of the top portion of the inner tank. The “bell” portion of the top tank is designed with multiple holes to access the inside tank.

Holes:

 Fueling Hole: has a 1 inch diameter; functions to have direct access from the

fueling facility to the fuel tank

 Defueling Hole: has a 0.5 inch diameter; functions to pull all of the LNG out of

the tank if needed in scenarios where the truck itself is under maintenance and

prevention of the LNG evaporating is necessary

 Pressure Relief Hole: has a diameter of 0.5 inches; functions to provide access to

the pressure relief valves, both the primary and safety relief valves

The ullage tank has a hole at its top that is 1/8 the size of the cryogenic fill line which is 1 inch in diameter. The main tank and the ullage tank communicate using the 1/8 inch hole. Due to the fill line being significantly larger than the ullage hole the ullage tank will remain mostly empty while filling. At the moment the main tank becomes full, a sharp pressure rise will occur as the flow resistance substantially increases resulting in decrease flow into the main tank [21]. The decrease in flow can be easily detected by an inexpensive flow monitoring device and thus the fill sequence will then be stopped. The available vapor space left in the ullage tank provides 17 space for the inevitable heat leak liquid expansion. This process increases the tanks hold time of

LNG dramatically [21].

Figure 8: Ullage Tank Attached to Tank Lid

3.3 Insulation Layer:

The insulation layer is located between the inner and outer shells. It is made up of a material called multi layer insulation (MLI) (Figure 9 below). This material has been selected for the composition because it has a low thermal conductivity (K= 0.0001 W/m-k), high thermal resistance (R=1440 m^2K/W) and the fact that it is lighter in weight than perilite. The thickness of this layer is 1 inch. 18

Figure 9: Insulation Layer

3.4 Outer Tank Shell:

The outer shell has a diameter of 0.5 inches and is made of 304 stainless steel. This layer will serve as a crucial factor in creating a vacuum that goes in between the inner and outer shell, so that the inner insulation layer, MLI, can work at its best. This vacuum enables the insulation layer to receive a pressure of 0 torr, which thus provides the MLI to work efficiently. The bottom of the outer shell, which has a depth of 3 inches, contains 4 holes that are designed to sit the rivets from the inner shell. The depth of such holes measure 1 inch deep. The outer shell contains both an upper and lower part, which mimics the resemblance of that of the inner shell. These parts are put together by the Shielded Metal Arc Welding Method. 19

Figure 10: Outer Tank Layer 3.5 Manifold: The manifold, depicted in Figure 11 below, is the part of the design that is placed on top of the outer shell. Its purpose serves to protect the pipes, connections, and security valves. Some of the components that the manifold possess include 2 gauges, one for pressure and the other for fuel level, fuel intake, a venting valve, 2 pressure relief valves, and the refueling connection.

Figure 11: Manifold 20

3.6 Overall Tank View:

Figure 12: Tank Assembly Figure 13: Full Tank View

4 Limitations and Future Work: Most of the limitations in work are found in the commercial and market of LNG fuels tank on heavy duty vehicles. The difficulties in accurate calculation of heat transfer into the system also limited the work of the project. Future work would be implementing a heat exchanger into the overall LNG fuel delivery system. LNG fuel tank mounting brackets could also be designed to adequately adapt the tank to the frame of the truck. 21

5 Gantt Chart 22

References:

[1] “Market Trends – Natural Gas,” U.S. Energy Information Administration. Internet: http://www.eig.gov/forcasts/aeo/MT_naturalgas.cfm. 2013 [Nov. 3, 2013]. [2] “Liquefied Natural Gas: Properties and Reliability,” Natural Resources Canada. Internet: http://www.nrcan.gc.ca/energy/sources/natural-gas/1200#archived. 2011 [Nov. 3, 2013]. [3] B. Hodgins, “High Performance Natural Gas Technology for Mining and Rail,” Mining Magazine. Westport. Nov. 2010. [4] GFS CORP, “LNG Solutions for Mine Haul Trucks,” March 2013. [5] N. Haigh, “LNG Equipped Trucks,” LME Marketing Report. Liebherr. Nov. 2012. [6] D. A. Franklin, “LNG Giving Producers New Options,” The Americal Oil & Gas Reporter, March 2013. [7] B. White, “LNG has its Own Problems.” Internet: www.arcticgas.gov, June 2011 [Oct. 31, 2013]. [8] “LNG Vehicle Fuel Tank Installation and Operation Manual.” Internet: www.taylorwharton.com/assets/bas/doc/products/cylinders/TW-359 LNG Vehicle Fuel Tanks.pdf, 2004 [Oct. 1. 2013]. [9] “Cryogenic Insulation.” Internet: .technifab.com/cryogenic-resource-library/cryogenic-insulation, [Nov. 1, 2013]. [10] “Steels for Cryogenic and Low-Temperature Service.” Internet: www.keytometals.com/Articles/Art61.htm, Oct. 2001 [Oct. 4, 2013]. [11] “Types 304 and 304L Stainless Steel.” Internet: www.nickelinstitute.org/KnowledgeBase/TechnicalLiterature. Oct. 2012 [Nov. 1, 2013]. [12] “Super Insulating Perlite for Evacuated Cryogenic Service.” Internet: www.perlite.org/industry/insulation-perlite.html, [Nov. 1, 2013]. [13] S. Macdonald, B. Hodgins. “Current and Future LNG Technologies,” Shell. Oct. 2012. [14] http://www.wika.us/company_en_us.WIKA?ActiveID=12618 [15] JC Carter Nozzles & Accessories for LNG [16] http://www.pcb.com/Products.aspx?m=102A14#.UxO7YPm-18E [17] Ashcroft Gauges, General Information [18] Resource Guide for Heavy-Duty LNG Vehicles, Infrastructure, and Support Operations by Kevin L. Chandler, Matthew T. Gifford, Brian S. Carpenter; March 2002. 505 King Avenue Columbus, Ohio 43201 [19] Cryogenic Temperature Sensors. [20] Product Digest: WIKA’s Featured Products [21] https://www.google.com/patents/US6128908 23

[22] Transit Cooperative Research Program, Guidebook for Evaluating, Selecting, and Implementing Fuel Choices for Transit Bus Operations, The Federal Transit Administration, [23] https://www.asme.org/getmedia/1adfc3df-7dab-44bf-a078- 8b1c7d60bf0d/ASME_BPVC_2013-Brochure.aspx