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OPERATIONS MANUAL

LNG VEHICLE FUEL TANK SYSTEM LNG VEHICLE FUEL TANK SYSTEM LNG VEHICLE FUEL TANK SYSTEM

(2)

PREFACE I

SECTION DESCRIPTION PAGE NO.

I Preface . . . .2

Table of Contents . . . .2

II Equipment Description . . . .3-5 III Specifications . . . .6

IV Safety . . . .7

V Operation . . . .8-9 Filling . . . .8

Fuel Supply . . . .8

VI Tank Installation . . . .10-11 VII Maintenance . . . .12-17 Component Replacement . . . . .12

Loss of Vacuum . . . .13

Liquid Level Gauge . . . .14

Service Pressure . . . .12

Fuel Leak Repair . . . .12

Valve Repair . . . .12

VIII Parts List . . . .18-19 Illustration . . . .18

Part Numbers . . . .19 MVE, Inc.

3505 County Road 42 West Burnsville, MN 55306-3803 USA Customer and Technical Service:

Phone: 612-882-5000 Toll Free: 888-877-3093 Fax: 612-882-5188

email: appliedtech@mve-inc.com

This manual is designed to familiarize experienced mechanics and vehicle operators with the features, safety precautions, operating procedures and maintenance of the LNG Fuel System provided by MVE, Inc.

No attempt should be made to fill or maintain this equipment until this manual and its supplements have been read and fully understood.

The following abbreviations are used throughout this manual:

LNG – Liquefied Natural Gas SS – Stainless Steel

NFPA - National Fire Protection Association

The following terms are used throughout this manual:

WARNING: Description of a condition that can result in personal injury or death.

CAUTION: Description of a condition that can result in equipment or component damage.

NOTE: A statement that contains information important enough to repeat.

(ITEM): Item numbers that reference component replacement parts.

MVE LNG vehicle tanks may be covered by one or more of the following United States patents:

5,651,473 5,404,918 5,421,161 5,421,162 5,163,409

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II EQUIPMENT DESCRIPTION

Super Insulation

Inner Vessel

Vent Valve Relief Valve

Evacuation Plug Do Not Remove

Outer Vacuum Jacket

Fuel Delivery Connection Protection

Ring Excess Flow Check Valve

Fill Check Valve Economizer

Regulator

LNG Vehicle Fuel Tank

The LNG fuel tank is a cryogenic container that is designed as two separate pressure vessels, one inside of the other. The inner vessel stores the cold LNG in its liquid form. The inner vessel is wrapped with multiple layers of non-combustible insulation and reflective foil (super-insulation), then sealed within the outer vessel. The space between the inner and outer vessels is then evacuated to produce a superior insulation system. The outer vessel and its support system are designed to withstand the stresses associated with over the road vehicles.

The inner vessel is protected from over pressurization by two safety relief valves. The first to open is the primary relief valve. It is designed to safely vent excess pressure from the inner vessel due to normal heat leak through the insulation and support system, or accelerated heat leak due to loss of vacuum or a fire condition. The secondary relief valve, with a higher set point, provides protection in the event the primary relief valve malfunctions or is blocked.

The outer vessel is protected from over-pressurization by an annular space evacuation plug. In the event of an inner leak into the outer vessel, the evacuation plug will open and safely vent off any excess pressure. In the event of an exterior leak into the annular space and the vacuum is lost, abnormal sweat or frost will show on the outer vessel. (Some frost and condensation on the plumbing end of the tank is normal).

All plumbing components are located on one end of the vessel and are protected from damage by a protection ring or a shroud.

(4)

EQUIPMENT DESCRIPTION II

LNG Vehicle Fuel System

The LNG vehicle fuel system, as described in this manual, consists of a LNG vehicle fuel tank (Item 18), engine coolant vaporizer (Item 15) and a fuel tank liquid level gauge (Item 13 & 14). The system is designed to

receive, store, and supply LNG as vapor gas to the vehicle’s engine. The fuel tank portion of the system can be attached to various single hose fill connections (C-1) that are provided separately by MVE.

Fuel Supply To Engine Engine Coolant Out

Engine Coolant In

20 15

22

E F

13 14

Remote Filling Connector

C-1

18 16 4

3 2 19 12

5

9 8

17 11

21

ITEM DESCRIPTION FUNCTIONS

2 Secondary Relief Valve Used to limit pressure in fuel tank.

3 Primary Relief Valve Used to limit pressure in fuel tank.

4 Manual Vent Valve Used to vent pressure from the fuel tank.

5 Economizer Regulator Used to control operating pressure of the fuel tank.

8 Fill Check Valve Used to prevent reverse flow in the fill line.

9 Excess Flow Valve Used to restrict excess flow in event of a fuel line breakage.

11 Fuel Shut off Valve Used to shut off fuel supply.

12 Probe Connection Used to “feed thru” capacitor signal from tank to fuel sender 13 Fuel Gauge Sending Unit Used to convert the capacitance signal for the fuel gauge.

14 Fuel Gauge Used to display fuel level in the tank.

15 Vaporizer Used to convert the liquid fuel to gaseous fuel.

16 Vent Connection Used to connect to the vent line.

17 Filling Connection Used to fill the LNG fuel tank.

18 LNG Tank Used to store LNG and supply fuel to the engine

19 Fuel Tank Pressure Gauge Used to display fuel tank pressure 20 Liquid Withdrawal Tube Used to deliver liquid

21 Vapor Withdrawal Tube Used to deliver vapor

22 Liquid Spray Bar Used to top fill the tank and collapse the vapor C-1 Remote Fill Connection Used to fill the LNG Fuel Tank

(5)

II EQUIPMENT DESCRIPTION

LNG Liquid Level Gauge

The MVE liquid level gauging system is a solid state capacitance metering system consisting of three subsystems: the fuel capacitance probe, the sender unit and the fuel gauge.

The fuel capacitance probe is an integral part of the fuel tank and is not externally serviceable. Its function is to generate a signal to the sender assembly that is proportional to the amount of the fuel in the tank. The signal is unaffected by the state of the product (liquid or gas phase) or by tank pressure. It will accurately reflect the actual mass of the product in the tank. The fuel probe is located at the fuel pickup near the plumbing end of the tank. It is designed to dampen the effects of acceleration, braking, hills and cornering, although some variation will be seen in the readout under these transient conditions, similar to its gasoline and diesel counterpart. On multiple tank applications, the capacitance is summed from all of the tanks to give an accurate reading representing the total amount of fuel onboard.

LNG Vaporizer

The fuel exists in the fuel tank as both a cold liquid and cold vapor. It can be withdrawn from the fuel tank in either liquid form or as a mixture of liquid and vapor.

The LNG vaporizer converts it to a consistent warm vaporous form. The vaporizer is located between the fuel tank and the engine. The vaporizer is connected to engine coolant which flows through it and around the vaporizer coils. As the LNG comes into the vaporizer the heat from the engine coolant turns it into vapor and warms it. The vaporous fuel can then be supplied to the engine. Various sizes and configurations are available.

The coolant flow must be plumbed in the same direction as the LNG flow. The vaporizer can be mounted either horizontally or vertically. When mounted horizontally, the coolant nipples must be positioned straight up to prevent air entrapment.

NOTE: The vaporizer does not increase the fuel pressure.

Vehicle Vaporizer Assembly

LNG IN

VAPORIZER COILS

GAS OUT

COOLANT IN

WATER JACKET

COOLANT OUT

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SPECIFICATIONS III

All HLNG models have the following specifications in common.

Shrouded Plumbing Cabinets...(20” And Up) Inner and Outer Vessels...304 Stainless Steel Plumbing Components...Stainless Steel & Brass Maximum Allowable Working Pressure (MAWP)...230 psi Operating Pressure Range...Factory Set @ 25 - 200 psi

*Full weight calculations are based on a 3.5 lb/gal (.42 kg/liter) density LNG.

Gallons

17 24 41 63 72 97 119-

Dimensions in (mm) in (mm) in (mm) in (mm) in (mm) in (mm) in (mm) Diameter 16.0(405.0) 16.0(405.0) 20.0(508.0) 24.0(610.0) 24.0(610.0) 24.0(610.0) 26.0(600.0) Length 32.0(810.0) 42.0(1065.0) 48.0(1805.0) 50.0(1270.0) 57.0(1450.0) 72.0(1450.0) 76.0(1930.0)) Capacity Gal. (Lit.) Gal. (Lit.) Gal. (Lit.) Gal. (Lit.) Gal. (Lit.) Gal. (Lit.) Gal. (Lit.)

Net 15.0(55.0) 21.0(70.0) 37.0(140.0) 57.0(215.0) 65.0(245.0) 88.0(335.0) 108.0(410.0) Gross 16.0(60.0) 24.0(90.0) 41.0(155.0) 63.0(240.0) 73.0(275.0) 97.0(365.0) 120.0(450.0) Weight Lbs. (Kg.) Lbs. (Kg.) Lbs. (Kg.) Lbs. (Kg.) Lbs. (Kg.) Lbs. (Kg.) Lbs. (Kg.) Empty 100.0(45.0) 125.0(55.0) 225.0(102.0) 275.0(125.0) 320.0(145.0) 440.0(200.0) 505.0(230.0) Full* 150.0(70.0) 200.0(90.0) 350.0(160.0) 475.0(215.0) 550.0(250.0) 750.0(340.0) 885.0(400.0)

PART NO. HORSEPOWER A B C D E

RATING

10582851 150 11-1/4 4-1/2 6-1/2 7-1/2 4-5/8

9722999 300 19-1/4 4-1/2 14-3/4 15-1/2 4-5/8

10668725 450 26-1/2 5 21-1/2 22-1/2 5-1/8

Specifications:

Max. Operating Pressure (LNG): 300 p.s.i.g.

Max. Coolant Pressure: 50 p.s.i.g.

Material: 730+ Stainless Steel

Vaporizer Fuel Tank

A

GAS OUT (3/8” FPT) B

COOLANT OUT (1/2” FPT)

D

COOLANT IN (1/2”)

LNG IN (3/8” FPT)

E

C(MAX)

(7)

IV SAFETY

General

This section of the manual deals with the safety precautions that are necessary with cryogenic equipment. For more complete information on safety and handling of Cryogenic Liquids, refer to CGA* P- 12. The potential hazards in handling Liquefied Natural Gas (LNG) stems mainly from the physical properties:

The liquid is extremely cold, -260°F. LNG boils at atmospheric pressure.

Very small amounts of LNG are converted into large amounts of natural gas. Pressures may rapidly increase if a means of relief is not provided. The expansion rate of LNG is approximately 620:1.

Natural gas is an asphyxiant.

Natural gas is flammable.

Safety Precautions

These hazards require that certain safety precautions be taken when working with or around natural gas and/or LNG:

1. Keep the LNG equipment away from open flames or electrical sparks.

2. Never permit smoking in an area where LNG equipment is repaired, filled, or stored.

3. Always wear eye protection such as goggles or a face shield, and gloves when working with or around LNG.

4. Always empty the LNG fuel tank and remove any pressure on the system prior to removing parts or components for repair.

While MVE equipment is designed and built to the most rigid standards, no piece of mechanical equipment can ever be made 100% foolproof. Strict compliance with proper safety and handling practices is necessary when using the LNG fuel tank system.

We recommend that our customers emphasize safety and safe handling practices to their employees and customers. While safety features have been designed into the unit and safe operations are anticipated, it is essential that the user carefully read and fully understand the WARNINGS, CAUTIONS, and NOTES throughout the manual. Periodic review of this information is recommended.

WARNING

COVER EYES AND EXPOSED SKIN. Accidental contact to LNG or cold issuing gas with the eyes or skin may cause a freezing injury similar to a burn. Protect the eyes and cover the skin whenever possible contact with cold liquids or gas exists.

WARNING

KEEP THE EQUIPMENT AREA WELL VENTILATED. Although LNG is non-toxic it can cause asphyxiation in a confined area without ventilation. Any atmosphere that does not contain enough oxygen for breathing can cause dizziness, unconsciousness, or even death.

Natural gas, being colorless, odorless, and tasteless cannot be detected by human senses.

Without adequate ventilation, natural gas will displace the air and give no warning that a non- life supporting atmosphere is present. Store LNG in a well ventilated area.

WARNING

REMOVE PRESSURE. The LNG fuel system is a pressurized system. Liquid natural gas will boil and cause pressure to build in the system.

Always empty the vessel of LNG and any pressure before working on the LNG fuel system.

DO NOT allow LNG to become trapped in piping, as between two closed valves. The liquid will vaporize and rapidly increase pressure, bursting the pipe.

WARNING

KEEP AWAY FROM FLAME OR SPARK. Natural gas is flammable. Smoking, open flames, and general purpose electrical equipment shall be prohibited where liquefied natural gas is stored or handled. Liquefied natural gas shall be stored and transferred under positive pressure to prevent the infiltration of air or other gases.

* Compressed Gas Association, Inc.

1235 Jefferson Davis Hwy.

Arlington, Virginia 22202

(8)

OPERATION V

Fuel Supply

The supply of vaporous fuel to the engine is the primary objective of the LNG fuel tank system. . The fuel tank is usually at a high pressure after periods of non use. The economizer is factory set at the fuel supply pressure desired by the engine. A final line regulator may be added to the fuel supply line at the engine to limit the maximum pressure. The final line regulator is usually set at 15 PSI over the economizer setting to insure that high pressure fuel is not allowed to reach the engine.

Liquid Withdrawal

When the tank operating pressure is below the economizer setting, the economizer regulator (Item 5) will close. While the engine is running, the tank pressure will push only liquid from the bottom of the tank (item C) into the vaporizer (Item 15). The liquid will be turned into gas and warmed before it is delivered to the engine. The pressure decay will be minimal since a small amount of liquid can be vaporized into a large amount of gas.

Liquid Withdrawal Normal Filling

Filling the LNG vehicle fuel tank is done through a single hose. When the fill nozzle (item C-1) is connected to the quick connect receptacle (item 17), and LNG is supplied at a pressure higher than the vehicle tank, LNG will enter the inner vessel through connecting pipe. The liquid is sprayed into the top of the inner vessel through the top fill spray header (Item A). This top filling action will collapse the vessel head pressure during the fill and eliminate the need to vent or recover vapor. The filling valve is a check valve (Item 8) that automatically allows the liquid into the vessel without the need to be manually opened or closed. The fill is terminated automatically at the proper fuel level. As the top spray ports are covered with liquid, the pressure quickly rises in the vessel to that of the delivery pressure. When these pressures become equal the filling stops.

Vent Filling

The LNG vehicle fuel tank can be filled from a pressurized storage tank. A single fill line connected between the storage tank and the remote fill fitting (C-1) will start the liquid to flow. As the pressure in the fuel tank rises, throttle the vent valve such that the saturation pressure of the transferred fuel is not lowered past the operating pressure required by the engine. Continue to fill until Liquid LNG spits from the vent valve. Close the vent valve first then the liquid valve, and remove the filling hose from the (C-1) fitting.

NOTE: A completely full tank will rapidly build pressure and may open the relief valve.

Warm Tank Filling

The LNG vehicle fuel tank is considered to have a warm inner vessel either prior to the initial filling of the tank, or after the tank has been out of service for more than two weeks. The recommended procedure for a warm tank fill is as follows. Fill the vehicle tank with approximately 5 gallons of LNG and allow it to build pressure. This will begin to cool the inner vessel down and build enough pressure to allow a leak test to be performed. The pressure may now be vented down and a normal fueling sequence may be done. A vent filling sequence may also be used on a known warm tank.

18

A 16 4

C1 8

17

Filling

(9)

V OPERATION

Vapor Withdrawal

When tank operating pressure is higher than the economizer setting, the economizer regulator (item 5) will open. While the engine is running, the tank pressure will push both gas from the top of the tank (item B) and liquid from the bottom of the tank (item C) into the vaporizer (item 15). The 2-phase mixture will be vaporized into only gas and warmed as it proceeds to the engine. Significant pressure decay within the tank will occur until the economizer setting pressure is reached.

Vapor Withdrawal

LNG Vehicle Fuel Tank Installation

Fuel Tank Mounting

The LNG vehicle fuel tank is mounted to the chassis frame of the vehicle by way of tank brackets. Two rubber backed brackets per tank are required, one on each end of the tank just inboard of the weld seam.

In accordance with NFPA 57 guidelines the combined straps should have a design failure point of at least 8 times the weight of the tank and fuel. A list of tank bracket manufacturers is available upon request.

The plumbing component end of the tank should be mounted towards the rear of the vehicle for optimal performance. There is a driver’s side and passenger’s side for the saddle mounted tanks.

These tanks are set up with the plumbing component end to the rear of the vehicle. This will ensure that the liquid will always be available for delivery during hard accelerations and going up hill.

The orientation of the tank should be with the liquid withdrawal circuit at 1:30 as on the clock and the fill circuit at 3:00. This will ensure that the liquid pick-up tube is located at the bottom of the tank and submerged for proper performance.

Component Mounting

Fueling Receptacle

There are a variety of fueling connectors and fueling methods available. The tank is capable of being filled with either a single or dual hose fueling connection.

MVE recommends the use of the Parker Hannifin single hose fueling nozzle and receptacles. The fuel receptacle should be attached to a rigid mounting plate. According to NFPA 57 guidelines the plate must be strong enough to withstand normal coupling and uncoupling loads, and also to prevent failure in a drive away situation with the hose still connected.

Other considerations should be to allow room for the vent receptacle and pressure gauge. For larger tanks, the fuel receptacle should be plumbed with 3/4"

or 1" S.S. tubing, on the small 40 gallon or less tanks, a 5/8" fill line is adequate. The receptacle can be directly connected to the fill check valve, there is no need for a shutoff or a line valve in this application.

The fill line should be kept as short as possible.

CAUTION: Where a fuel receptacle is mounted to the side of the vehicle an “S” bend in the tubing is recommended for side impact purposes.

NOTE: Saddle mounted tanks have the fuel receptacle mounted in the shroud of the tank. The receptacle is located at 10:30 as on the clock for the driver’s side and 1:30 on the passenger’s side.

Vent Receptacle

There are a variety of vent connectors available, MVE recommends the use of the MVE vent receptacle.

The MVE receptacle has a positive 1/4 turn locking device and is easily installed and removed. The vent receptacle should be plumbed with 3/8" or 1/2" S.S.

tubing.

CAUTION: Where vent receptacle is mounted to the side of the vehicle an “S” bend in the tubing is recommended for side impact purposes.

NOTE: The vaporizer is being supplied liquid at all times, when the economizer opens, it also allows vapor into the liquid stream.

C

(10)

TANK INSTALLATION VI

Liquid Level Fuel Gauge

The liquid level fuel gauge is to be installed in the cab of the vehicle. The power requirement for the gauge is a 13.8v positive feed and negative ground. The sending unit assembly located at the head of the tank will also need a 13.8v positive and negative feed. The signal wire (green) from the sending unit to the fuel gauge will need to be run. The fuel gauge illumination light may be connected to the dash light circuit if needed.

CAUTION: The fuel level gauge is not weatherproof and therefore should be installed inside of the vehicle.

Vaporizer

The vaporizer may be mounted anywhere in the fuel delivery circuit. For maximum system performance MVE recommends that the vaporizer be mounted as close to the tank as possible within a maximum of 6 feet. Two clamps are provided for attachment. The coolant lines should be of 5/8” heater hose for runs of 10 feet or less and 3/4” for runs of more than 10 feet.

A minimum flow rate of 4 gallons per minute of coolant at full throttle is required. The coolant flow must be directed in the same direction as the natural gas flow through the vaporizer. The vaporizer can be mounted vertically or horizontally, if mounted in the horizontal position, the engine coolant ports must be pointed upwards to prevent entrapment of air within the vaporizer. The gas inlet and outlet ports are 3/8" fpt and the coolant inlet and outlet ports are 1/2" fpt. If a manual shut off valve is to be installed, it is recommended that it be attached to the system after the vaporizer, this is also recommended of any down stream pressure regulators needed.

NOTE: Saddle mounted tanks have the option of a heat exchanger mounted in the shroud of tank, the coolant ports are 1/2" fpt. This option has the gas lines

plumbed to and from the heat exchanger. There are bulkhead fittings installed in the side of the shroud for plumbing to the engine control package.

Component Plumbing

Relief Valves

The relief valves are a spring operated, weep type relief valve with a soft seat that opens gradually at their set pressure. Each relief valve is sized to handle the worst possible combination of pressures and flows that can be encountered by the tank. The primary relief valve should be plumbed to the rear of the vehicle, up and away from the passenger compartment. Stainless steel or copper lines are recommended. The relief line should be of 1/2"

in diameter or larger. MVE recommends that only the primary relief valve be piped away. The secondary relief valve should be left with the factory installed plastic cap in place. If a line blockage due to ice, or collision were to occur rendering the primary relief valve inoperable the secondary relief valve would function properly. It is also recommended that a relief line low point drain be installed in the circuit to prevent any water accumulation that might occur.

CAUTION: The water drain should be plumbed away from the passenger compartment, 1/8" tubing is recommended for the water drain.

NOTE: Saddle mounted tanks have a bulkhead fitting installed in the shroud of the tank for the primary relief valve plumbing. The primary relief valve to the bulkhead fitting is plumbed at the factory.

Fuel Delivery Lines

The fuel delivery line is broken down into two lines. The first being the cold liquid line running from the fuel tank to the vaporizer and the second line being the warm vapor line running from the vaporizer to the engine control package. The larger diameter line is necessary to minimize pressure drop. The gas that is now being delivered to the engine is at a lower density than the liquid.

All of the tubing should be supported against vibration.

Teflon or polyethylene coated clamps spaced every two feet is recommended.

NOTE: Saddle mounted tanks have a bulkhead fitting mounted to the shroud of the tank for the liquid out. This bulkhead fitting is 3/8" fpt. The excess flow valve to the bulkhead fitting is plumbed at the factory.

The liquid line should be 3/8” OD .035” wall stainless tubing for runs of 6’ or less and 1/2” OD for runs greater than 6’. The gas line should be 1/2” ID for runs of 15’ or less and 5/8” for runs greater than 15’.

Pressure Gauge

The pressure gauge should be located in an area that is easily readable while fueling operations are occurring. MVE recommends a 0 to 300 psig gauge.

The gauge should be plumbed with 1/8" S.S. tubing.

There is a 1/8" female pipe thread fitting located on the head of the tank for the pressure gauge connection. Fittings used for gauge connections must not have an inner hole bigger than 0.059” as per NFPA-57.

NOTE: Most tanks are shipped from the factory with a pressure gauge located on the head of the tank and the ones that do not, have a pressure tap.

(11)

VI TANK INSTALLATION

Tube Fittings

The tube fittings should be of either stainless steel or brass construction, and should incorporate either a double ferrule or 3 piece flare. Parker A-Lok, Swagelok or Hoke Gyrolok are the recommended fittings. All check valves and pipe fittings should be backed up with a wrench when installing the tube fittings. Leaks may occur if the tube fittings are not properly installed.

Sealants

For threaded pipe fittings 1/2 inch and larger, use Loctite PST567. For smaller than 1/2 inch pipe size, use Loctite Hydraulic Sealant 569. If used on stainless steel (or if faster cure times are desirable) Loctite Klean-N-Prime 24163 must be used on the fittings. The primer must be preapplied and allowed to dry (minimum 15 minutes) before applying the sealant. Fittings must be tightened clockwise only, if tightened past the desired point, remove the fitting and start over, don’t backup. The sealant must be allowed to cure before applying pressure. PST with Klean-N-Prime requires 4 hours and Hydraulic Sealant with Klean-N-Prime requires 30 minutes.

Without Klean-N-Prime, full cure time on PST is 3 days and Hydraulic sealant is 1 day. Neither sealant will ever cure on stainless steel without the use of Klean-N-Prime. The sealants and primer can be purchased from MVE direct or from local vendors.

For the nearest vendor, call 1-800-LOCTITE.

Multiple Tank Installation

The fill and withdrawal circuits are completely independent from one another, multiple tanks are simply piped parallel on the fill and withdrawal lines.

There is no need to cross connect any lines to try and maintain uniform liquid levels in the tanks. If one tank goes empty before the other, the fuel will simply be provided by the tank with the remaining liquid. The driving force of the fuel is the liquid itself (saturation pressure). The liquid withdrawal line from each tank may be plumbed to a “tee” fitting and then a single line may be plumbed from the

“tee” fitting to the vaporizer or a “tee” fitting may be installed in the vaporizer and the two liquid lines plumbed independently of each other. The fuel lines from each tank do not have to be of the same length or increased in diameter due to the multiple tank configuration. The liquid fill lines may be connected to one another prior to attachment to the fill receptacle. If one tank goes full first it will continue to fill the other tank. The manual vent lines may be connected to one another prior to attachment to the vent receptacle. MVE recommends one-way check valves be installed at each of the manual vent valves when plumbing the vents together. The primary relief valves may be plumbed together and then a single line may be run out to the rear of the vehicle. The relief line will need to be increased in diameter to accommodate the flow of the multiple tanks.

NOTE: When fueling a warm multiple tank system with the liquid fill lines connected, the tank opposite the tank being filled will need to be vent filled separately. The fuel lines and the fuel tank is in a warm condition and will flash off the liquid at a greater rate than is being supplied.

(12)

VII MAINTENANCE

Leak Detection

A portable methane detector should be used to check for natural gas leaks on the vehicle (refer to Methane Detector Manufacturer’s Instructions for proper use).

Periodic leak checks should be performed as well as whenever the vehicle is in for service. If a leak is found, it should immediately be repaired. Sometimes it may be difficult locating the exact source of the leak with a methane detector in which case a soap bubble solution such as snoop may help identify the source.

Fuel Leaks

All fuel leaks should be fixed as soon as possible.

Pipe threaded leaks should be removed, cleaned and re-installed with an approved sealant. Refer to sealants in Section VI. Tube fitting leaks should be removed and inspected for proper installation. If the appearance of the nut and ferrules looks to be OK, re- install the tube and tighten the nut. Re-inspect for pressure leak. If the leak is found to be in the economizer circuit or in the relief valve tree and its circuit, the tank must be vented down to zero pressure before attempting to fix the leak. If the leak is found to be in the fill circuit before the fill check valve, the fill line may be removed without the need to vent the pressure down inside the tank. The fill check valve will seat and not allow any pressure to escape.

Component Replacement

The following contains the information regarding LNG fuel tank care and maintenance. When performing a procedure that is described in this section, refer to the previous sections on operation or the parts illustration for a component item number and location.

Pressure Relief Valves

The inner pressure vessel used in the LNG fuel tank is designed and rated to a maximum operating pressure by the appropriate design code. All of the vessels have been proof tested for that rating. The maximum operating pressure is printed on the data plate located on the head of each tank. Do not install a relief valve with a higher pressure than specified. Lower pressures are commonly used for limiting the maximum pressure of the liquid.

Page 12

The relief valve can be changed in the following manner:

1. Open the vent valve (Item 4) and release all pressure from the vessel.

2. Remove the relief valve (Item 2 or 3).

CAUTION: Do not attempt to repair or reset the relief valve.

3. Clean the sealant from the female threads.

4. Install the new relief valve. Use Loctite hydraulic sealant 569. (Refer to sealants in Section VI) 5. Pressurize the container and leak test.

Economizer Regulator

The economizer regulator on the tank lowers the system pressure by allowing vent gas to flow out to the engine along with the LNG stream when the tank pressure exceeds its setting. The pressure is preset at the factory prior to shipment and is non-adjustable.

A vehicle with a properly functioning economizer should be at it’s operating pressure within an hour of normal driving.

To verify economizer operation, note the frost pattern on the regulator. When the tank is above its normal operating pressure the economizer will be open, the tank pressure will be falling and the regulator will frost up during vehicle operation. Once the tank reaches its normal operating pressure the economizer will close, the tank pressure will be steady and the regulator will thaw (assuming that ambient temperatures are above freezing).

It is necessary to remove the tank from service to change an economizer regulator. The tank must be emptied of fuel and the gas pressure vented to zero pressure prior to regulator removal.

Rebuilding the Operational Valves

The valves that are used on the LNG fuel tank have a spring loaded rotary stem. This automatically compensates for thermal shrinkage and wear. When a defective valve is suspected, follow this procedure to repair it.

(13)

VII MAINTENANCE

Loss of Vacuum

The loss of vacuum on a LNG fuel tank is usually associated with cylinder frosting or rapid pressure rise.

Excessive pressure rise, however, can be normal. A new fuel tank or one that has not been used recently is considered to have a warmer inner vessel. A warm fuel tank will build pressure fast after fueling and vent off the excess. A LNG fuel tank that has been filled and not used will build pressure and vent the excess off. The higher the pressure was in the storage tank at the time of filling, the faster the liquid cylinder will vent off.

Excessive pressure rise can also be an indication of vacuum loss. The LNG fuel tank is equipped with an outer jacket evacuation plug that may pop open if there is a loss of vacuum. The loss of the evacuation plug indicates an inner vessel leak. The evacuation plug is protected from the environment and tampering by a plastic cap. Do not remove the plastic cap or evacuation plug. Return the fuel tank to the factory for repair.

Total loss of vacuum on an LNG tank is an unusual event, typically the vacuum in the cylinder gradually decays over a period of years until the tanks performance reaches an unacceptable level necessitating a re-vac. Typically “soft” vacuums are first detected by rapid pressure rises in stationary cylinders.

If the evacuation plug appears satisfactory and a vacuum loss is still suspected, it will be necessary to check the pressure rise time.

To test the pressure rise time on a cylinder, fill the tank and drive the vehicle until 3/4 to half a tank of fuel remain in the system and the tank has been pulled down to its normal operating pressure by the economizer. Shut off the vehicle, wait 30 minutes and read the tank pressure. Let the vehicle sit stationary for at least 12 hours. The pressure rise on the system should be less than 40 psi/day. if the vehicle is equipped with multiple tanks, and fails, the test should be repeated to isolate the problem tank. The liquid use valve and vent valve should be shut at the 30 minute point so each tank’s pressure rise can be separately determined. It should be noted that warm

31 29 32 26 25 27

28 30 21 33 24 22

34 23

1. Open the vent valve (Item 4) and release any pressure that is in the fuel tank.

2. If the valve to be repaired is the vent valve, allow it to warm up before it is disassembled.

3. If the valve to be repaired is the fuel supply valve (Item 11), the fuel tank should be emptied of LNG and pressure should be vented from the system.

4. Remove the valve handle screw (Item 23), washer (Item 34), retainer cap, and spring assembly (Items 22, 24, 28, 30, and 33).

5. Remove the valve handle (Item 21) and Teflon thrust washer (Item 27).

6. Unscrew bonnet (Item 25) to remove stem (Item 26) and stem seal.

7. Pick out body insert (Item 32) and plug assembly (Item 29).

8. Clean seat.

9. Replace parts as needed and reassemble in reverse order.

Item Part No Qty Description 21 17-1078-9 1 Handwheel 22 17-1086-9 1 Spring Retainer 23 17-1084-9 1 Screw

24 17-1077-9 1 Spring 25 17-1081-9 1 Bonnet 26 17-1089-9 1 Stem 27 17-1088-9 1 Gasket 28 17-1087-9 2 Washer

29 17-1082-9 1 Threaded Body Insert 30 17-1076-9 1 Seal

31 – Body Assembly

32 17-1083-9 1 Seat and Nipple Assembly 33 17-1080-9 1 Washer

34 17-1085-9 1 Washer

– 97-1575-9 – Valve Repair Kit

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MAINTENANCE VII

Page 14

connector. The red wire (pin A) is +13.8 volts DC, the black wire (pin C) is ground and the green wire (pin B) is signal output. The sender is calibrated with a 5%

offset on Full, and a 10% offset on Empty.

On multiple tank systems utilizing one gage, the capacitance probes are simply teed together with RG- 59U co-axial cable and function as one unit. The gage reading will indicate the combined capacity of the system of tanks. In all cases the co-axial cable is an integral part of the gaging system, changing the cable affects the capacitance input, and hence the output of the sender.

NOTE The coaxial cable is part of the calibration of each unit, if a longer section of coaxial cable is needed, contact MVE LNG Product Support for information on changing the cable.

Diagnostic Procedure

Problems with the gauging system are normally caused by faulty wiring connections. Most problems can be diagnosed with a handheld volt-ohm-meter.

MVE also offers a Weatherpack splice connector that is helpful in diagnosing problems. The Weatherpack splice connects between the two halves of the Weatherpac connector allowing voltages to be read with the entire gauge circuit operating.

NOTE: The fuel gauge is modular in design and is preset at the factory and requires no maintenance or adjustment. If the accuracy of the gauge is in question, contact MVE LNG Product Support for further assistance.

Preliminary Check (always start here for fuel gauge diagnosis)

When diagnosing a liquid level gauge problem, first perform a visual inspection of the fuses, wiring, cables and connections by looking for loos connections, cut, broken, rubbed through, open or shorted wiring and repair or replace as necessary.

Wiggle the connecting wires while watching the gauge for erratic operation to find an intermittent or loose connection.

cylinders, ie: first fill, and cylinders that have been overfilled, may also experience rapid pressure rises.

A tank that has experienced a total loss of vacuum will build pressure at a rate of ~ 1 psi/minute so is quite easy to detect. The outer shell of that tank, particularly near the plumbing manifold and rear support will be cooler than the surrounding metal.

Depending on temperature and humidity conditions the tank may or may not frost or sweat. The presence of condensation alone is not a reliable indicator of the tank’s vacuum. The pressure rise test is the most reliable indicator of the tank’s vacuum performance.

Tanks that have experienced a loss of vacuum must be re-evacuated by a competent repair facility. This may or may not involve removing the tank from the vehicle. Contact MVE customer service for advice on how to proceed.

Liquid Level Gauge

The capacitance level gage used in the tank consists of three elements. They are the capacitance probe, the sender, and the gage readout. The capacitance probe is a variable capacitator located inside of the tank. As the tank liquid level increases, it fills the capacitance probe with liquid changing its capacitance value. The probe has one pole grounded to the tank and the other pole connected to a wire that leads to a ceramic feedthrough and BNC connector on the outside of the tank. The typical capacitance value for a tank is in the range of 200-500 pf.

The sender is the black box located on the outside of the tank. Its function is to take the capacitance signal and convert it to an output useable by the gage readout. There are two types of senders. One type uses an automotive fuel gage to read liquid level and outputs a variable resistance to ground. The second type outputs a voltage typically to a computer input.

The sender has two connectors. One is a coaxial signal wire to the tank that terminates in a female BNC connector and the other is the power, ground and signal wire terminating in a 3 pin Weatherpack

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By using a digital volt-ohm meter and with the gauge system powered up (ie. Key on), check the voltages at the Weatherpac connector and at the gauge 9 where applicable), to verify that there is battery voltage at each of the red power wires and clean tight grounds at each of the black ground wires and repair as necessary.

Next, turn off the power to the gauge and insert the Weatherpac Voltage Splice Connector (MVE part number 109.8918.2) between the two halves of the Weatherpac connector. This connector allows electrical access to each of the terminals of the Weatherpac connector while the gauge circuit is still connected. Power up the gauge circuit again and check the voltage between the Signal wire (Green, Pin B) and the Ground wire (Black, Pin C) and compare with the following applicable chart.

Typical voltage readings for senders with VDO gauges (normally using an analog gauge with needle)

Empty Tank Full Tank Gauge Reading Probable Cause

5.68V 1.68V Normal operation Normal operation

9.24V 9.24V Always reads empty Poor ground at sender

9.73V 4.80V Always reads full Poor ground at gauge

8.95V 8.95V Always reads empty No power at sender

0.35V 0.26V Always reads empty No power at gauge

8.93V 8.93V Always reads empty No signal at gauge

8.74V 8.74V Always reads full BNC shorted

Typical voltage readings for senders with voltage outputs (normally using a digital readout)

Gauge Reading Probable Cause

High output (-0.7 volts less than input voltage) Poor ground

0 V. No power

~0.15V BNC disconnected

High output (~Maximum output voltage) BNC shorted

MAINTENANCE VII

GAUGE ALWAYS READS EMPTY

Always perform the Preliminary Check First. If the problem still exists, then as a last resort proceed on to the Defective or Mis-calibrated Sending Unit section.

GAUGE DOES NOT EVER READ EMPTY

Always perform the Preliminary Check First. If the problem still exists, then check for a water contaminated coaxial cable by inspecting the weatherproofing on the BNC connector and cable and replace the cable or sender as necessary and reseal it to the BNC connection with heat shrink if possible or self vulcanizing tape as a last resort Next refer to the Defective or Mis-calibrated Sending Unit section.

GAUGE ALWAYS READS FULL

Always Perform The Preliminary Check First. If the problem still exists, then refer to the Defective or Mis-calibrated Sending Unit Section.

FUSE IMMEDIATELY BLOWS

Check for reversed polarity of power leads within fuel gauge circuit and also inspect wiring for being pinched or shorted.

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Page 16

MAINTENANCE

Typical Capacitance Values Tank

Outside Diameter

12”

14”

16”

18”

20”

22”

24”

26”

Empty

190 pf 220 pf 245 pf 275 pf 290 pf 315 pf 340 pf 370 pf

Full (70 psig liquid)*

270 pf 315 pf 350 pf 395 pf 420 pf 460 pf 495 pf 540 pf

Weatherpac Voltage Splice Connector PN 109.8918.2

Replacement Encapsulating Heat Shrink PN 106.9247.7

VII

RG-59U Cable

2’ 35 pf

3’ 52 pf

4’ 70 pf

8’ 139 pf

bnc Tee - 6 pf Sender - 260 pf DEFECTIVE OR MIS-CALIBRATED GAUGE

NOTE: Only remove heat shrink from the BNC connector after performing the preliminary checks. The encapsulating heat shrink is there to keep moisture out of the cable and has to be cut off. If the cable jacket is cut or the connection is reassembled without the encapsulating heat shrink, water intrusion will occur and cause poor gauge operation. Replace heat shrink and/or cable as necessary to insure a dry watertight connection.

Disconnect the BNC connector from the tank. On the sender coaxial cable, short the center pin to the shield (outside of connector). Operational fuel gauge equipped units should read empty when disconnected and full when shorted. Units with voltage outputs will read low when disconnected and high when shorted.

One problem that can cause miscalibration or make the gauge stick high is water intrusion either within the coaxial cable or within the BNC connection. This will change the capacitance signal significantly by shorting the circuit for the sending unit. On all units, it will read more than what is actually in the tank or stay on full (high voltage for voltage output units) depending on how much moisture is present.

Another problem that can occur is that the wrong cable(s) may be used. If the style of connection, cable and/or the length of cable is changed, the capacitance value for that component will also change. Each of the sending units are calibrated for the exact type and length of coaxial cable, number and style of connection(s), size of LNG tank, number and arrangement of tanks and the saturation pressure expected to be normally used within the tank(s).

Lastly, it is possible that there could be a problem with the tank. Below is a list of capacitance values for all of the components supplied by MVE, which can be used to verify capacitance of each of the components separately.

NOTE: The span between the Empty and Full capacitance values will be 10% more with 0 psig LNG, 10% less with 200 psig LNG.

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MAINTENANCE VII

CBA

Green-Signal(S) Black-Ground Red-Ignition(I)

Signal Wire 3 Conductor Red / Black /Green

Gauge Connections

Sending Unit

Coaxial Cable

Dash Light Circuit (+12 Volt DC) Light

Gauge Ground

Signal (Green)

Ground Ignition

(+13.8 Volt DC)

Gauge Wiring Schematic

Probe Sender

Ground Weather Pack

Connector

+13.8 Volt DC Signal Green

(Pin B) Pin "A" – Red– +13.8 Volt DC Pin "B" – Signal Pin "C" – Black – Ground

Fuel Gauge Appendix

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PARTS LIST VIII

1

2

12

11 3

4

5

6

7 6

10 9

8

Components LNG Vehicle Fuel Tank

13

E

F

14

Fuel Gauge Vaporizer

15a 15b 15c

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VIII PARTS LIST

ITEM NO. PART NO. DESCRIPTION QTY

1 1611592 3/8" MPT- Pipe Away Adapter (for relief valve) 1

2 1810462 1/4" MPT- Relief Valve (350 psig) 1

3a 1812172 1/4" MPT- Relief Valve (235 psig) 1

3b 10747431 1/4" MPT- Relief Valve (150 psig) 1

4 Kit Avail. 3/8" FPT- Globe Valve (vent) 1

5 10784048 1/4" NPT- Regulator (70 psig) 1

6 10501685 1/4" MPT- Elbow 2

7 3310031 3/8" Stainless Steel Pipe 1

8a 1715451 3/8" FPT- Check Valve (w/ Teflon seat) 1

8b 10624360 1/2" FPT- Check Valve 1

9a 1718552 3/8" FPT- Check Valve-Excess Flow Valve - Bus 1

9c 10614840 Truck- Check Valve-Excess Flow Valve 1

10 1312131 3/8" Close Nipple 1

11 Kit Avail. 3/8" FPT- Globe Valve (fuel supply) 1

12 8514981 BNC Nipple Assembly 1

13 10637275 Fuel Gauge Kit (specify setup when ordering) 1

14 10923888 Fuel Gauge 1

15a 10682851 Vaporizer Assembly 150 HP 1

15b 9722999 Vaporizer Assembly 300 HP 1

15c 10668725 Vaporizer Assembly 450 HP 1

3830599 Decal Liquid Use Valve 1

3832619 Decal Fill 1

3830619 Decal Vent Valve 1

10647617 Decal 230 psi Max- Yellow 1

10586412 Decal LNG Diamond- Black 1

3835959 Decal UN-1972 5x5 Block 1

3830709 Decal Read Manual LNG 1

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MVE, Inc.

3505 County Road 42 West Burnsville, MN 55306

MVE LNG Product Support Toll Free Ph: (888) 877-3093 Worldwide Ph: (612) 882-5000 Fx: (612) 882-5188

P/N 3835849 Rev A 4/99

References

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