OMD™
User’s Manual
Heath Consultants Incorporated Houston, TX
713/844-1300
Fax: 713/844-1309
1-800-HEATH-US
www.heathus.com
Heath....Leadership, Innovation, Performance
Then, Now and Tomorrow
Rev1 E
2
TABLE OF CONTENTS
SPECIFICATIONS ....................................................................... |
5 |
CHAPTER I |
|
OVERVIEW ................................................................................ |
7 |
CHAPTER II |
|
INSTALLATION PROCEDURE .................................................. |
10 |
Crossbar Installation ................................................................. |
10 |
Additional Notes On Crossbar Installation .................................. |
11 |
Power Box Installation .............................................................. |
12 |
Cable Assemblies Installation .................................................... |
13 |
Display Installation .................................................................... |
14 |
Display Connectors ................................................................... |
15 |
Vehicle Grounding Strap ............................................................ |
15 |
Protective Cage ........................................................................ |
16 |
CHAPTER III |
|
OPERATING PROCEDURE ....................................................... |
18 |
Start Up .................................................................................... |
18 |
Display Function ....................................................................... |
20 |
HOLD .................................................................................. |
20 |
LIGHT ................................................................................. |
21 |
SAMPLE .............................................................................. |
22 |
PPM Range .............................................................................. |
23 |
Alarm Set Point ......................................................................... |
25 |
Error Messages ........................................................................ |
26 |
Shut Down ................................................................................ |
27 |
CHAPTER IV |
|
ALIGNMENT PROCEDURE ...................................................... |
28 |
Lamp Alignment ........................................................................ |
29 |
Receiver Alignment ................................................................... |
30 |
CHAPTER V |
|
CALIBRATION CHECK ............................................................. |
31 |
Verifying Calibration With Internal Cell ....................................... |
31 |
Verifying Calibration With External Cell ...................................... |
32 |
3
CHAPTER VI |
|
MAINTENANCE INFORMATION ............................................... |
34 |
General ................................................................................... |
34 |
Recommended Spare Parts ...................................................... |
34 |
Troubleshooting ....................................................................... |
34 |
CHAPTER VII |
|
SERVICE INFORMATION ......................................................... |
37 |
Warranty and Warranty Repairs ................................................ |
37 |
Customer Assistance and Service Locations ............................. |
38 |
Appendix A |
|
SURVEY PROCEDURES - MOBILE OMD™ ............................. |
40 |
Appendix B |
|
DRAWINGS ............................................................................. |
55 |
USING ADOBE ACROBAT READER......................................... |
60 |
4
SYSTEM SPECIFICATIONS
OMDTM System Specifications
Configuration: |
Double - ended |
Sensitivity: |
1 PPM / meter CH4 |
Measurement Range: |
1 to 200 PPM |
Accuracy: |
± 10% (1 to 100 PPM range) |
|
± 20% (100 to 200 PPM range) |
|
Above 200 PPM = Not relatively |
|
accurate |
Display Ranges: |
10, 30 and 90 PPM |
Self - test: |
During boot – up |
Calibration/Test: |
Via operator, self - contained |
Calibration: |
Via RS-232 through software |
Base - Line Compensation: |
Via RS-232 through software |
Display: |
Back-lit 2" x 6" graphics LCD, |
|
adjustable contrast |
Operator Interface: |
Sealed membrane switch overlay |
Operator Alarms: |
|
Signal: |
High pitch audible with |
|
adjustable set point, pitch |
|
increases with concentration. |
|
Adjustable volume. |
Error: |
Low pitch audible with |
Error alarms |
adjustable set point |
|
|
provided for: |
Warm-up, Low Light, |
|
Communication Failure & |
|
Battery low |
System Power: |
72 Watts @ 12 VDC |
System Voltage: |
12 - 16 VDC |
NOTE: To avoid damage to the OMD™ power box, the fuse must be removed prior to charging or jumping the battery in the survey vehicle!
5
SYSTEM SPECIFICATIONS
System Weight: |
|
External Sub - Systems: |
17 pounds |
Power Box |
6 pounds |
Internal Display |
3 pounds |
Cables |
4 pounds |
Crossbar Assembly Length: |
63.25, 32, 51.25in. ± 2in. |
Mechanical Mounting: |
Strut bracket mount |
Installation Time: |
2 hours, typical |
External Housing Rating: |
NEMA 3S and IP 54 |
Display Housing Rating: |
Spill proof |
External Sub - |
|
System Materials: |
Aluminum and plastic |
Environmental PCB Control: Conformal PCB coating |
|
Operating Temperature |
- 22°F to 122°F |
Range: |
|
Operating Humidity Range: |
5 to 100 % RH, non-condensing |
6
Chapter I
OVERVIEW
The Optical Methane Detector (OMD™), is the first of the “next generation” leak detection systems which address the high cost presently associated with leak surveying. This new technology combines sensitivity, selectivity and speed through the combined use of optics and electronics. The OMD is mounted on the front of a survey vehicle and detects the presence of methane in air. It provides for the detection of gas leaks down to 1 part per million (PPM). It has no moving parts that will prevent the instrument from operating. It requires no support gases and is virtually maintenance free.
Based on the absorption of infrared (IR) radiation by methane, the OMD consists of an IR light source directed at an IR optical detector. These two are spaced approx. four feet apart across the width of the vehicle. An optical filter in front of the detector transmits primarily methane specific IR wavelengths from the light source. In the absence of methane, these wavelengths are unaffected and produce a steady output signal from the detector. When the vehicle passes through a plume of natural gas, methane in the plume will absorb some of the IR light reaching the detector. As a result there is a sudden decrease in IR light at the detector causing a decrease in detector output. This change in detector output is transmitted to the display panel located next to the vehicle’s driver and becomes a signal, both audio and visual. Gas concentration is calculated in the OMD by converting the methane to light ratio to PPM. The data is displayed in both analog and digital form. The analog display appears as a peak scrolling across the display screen. The OMD will also detect other hydrocarbons such as ethane and propane but with less than half the sensitivity.
7
OVERVIEW
The OMD operates reliably under a variety of environmental conditions including dry weather, snow, ice and temperatures from -22° F to +122° F. Its sensitivity, calibration or response |is not affected by small fluctuations in the light beam or by reasonable amounts of dust, or snow on the optics. An internal calibration test cell is included so the operator can verify proper operation from the vehicle cab at any time before, during or after a leak survey. An Installation Mounting Kit is available for mounting the OMD to the front of a vehicle. All interconnecting cabling is provided with the OMD including the cable to obtain power to operate the instrument from the survey vehicle 12 volt battery. An RS232 port is included whereby a personal computer may be connected to acquire and save the survey data with the appropriate software.
Depending on local meteorological conditions, a given amount of gas escaping from the ground will produce a plume that varies in size and uniformity of concentration levels. The plume, of its very nature, defies quantification by fixed or moving detectors. Regardless of these uncertainties, it is of paramount importance to be able to detect gas when gas is present. Concentration levels of the measured gas are of interest, but are of secondary importance. Consequently, the ability of a detector to detect the plume with accuracy and precision is not as important as its ability to do so with good sensitivity (or a low detection limit) and with a minimum of false alarms.
There are two kinds of false alarms: false negatives and false positives. False negatives occur when a leak is missed. The detector is saying there is no gas present when, in fact, a leak was present but undetected. False positives occur when the detector says that a gas leak is present when it really is not. Examples of false positives experienced include the detection of
8
OVERVIEW
auto exhaust and swamp or sewer gas. Due to the selectivity of the OMD, false positives caused by auto exhaust are greately minimized.
NEW
Experienced operators should use their discretion. Operators should take into account that the wind must be favorable, towards the path of the OMD light bar, to obtain the optimum results. Increased speed from FID survey comes from the instantaneous response of the OMD; however, there are a variety of factors to consider such as, legal limits, terrain and inclement weather for the OMD operation. Please refer to the GPTC Guide for Transmission and Distribution Piping Systems: 1998-2000 Guide Material Appendix G-192-11 Section 4 Leak Detection, 4.4 Leakage surveys and test methods (a) Surface Gas Detection Survey. Part (3) Utilization. The use of this survey method may be limited by adverse conditions (such as excessive wind, excessive soil moisture or frost or surface sealing by ice water). The survey should be conducted at speeds slow enough to allow an adequate sample to be continuously obtained by placement of equipment intakes over the most logical venting locations, giving consideration to the location of the facilities and any adverse conditions which might exist.
9
Chapter II
INSTALLATION PROCEDURE
It is virtually impossible to predict the exact installation procedure for every different type of vehicle on the market. There are some details that will have to be worked out on the spot with your particular vehicle and here are a few ideas to consider.
There are five parts to consider when installing the OMD: 1) The crossbar assembly, 2) The power box, 3) The cable assemblies, 4) The display unit, and 5) Vehicle Grounding Strap.
Crossbar installation:
The OMD components are pre-aligned at the factory and should not require re-alignment when the system is installed on the vehicle. It is, however, important that the u-bolts be attached in such a way that they do not bend the support rod. The u-bolts should be tight enough to hold the OMD crossbar securely in place, but not so tight as to distort the crossbar. If that happens, re-alignment may be required. We recommend using only two insulated u-bolts to mount the OMD crossbar to minimize the possibility of distorting the crossbar. The following procedure will generally work best.
For your convenience, we have put together an OMD mounting kit, which includes strut channels, shelf brackets, u-bolts and mounting hardware (Heath P/N 2510651).
Use two strut channels that are approx. 24” long each (Heath P/ N 2510652). These strut channels are mounted vertically to the front bumper of your vehicle, parallel to each other and approx. three feet apart. It is most fortunate if you have a front bumper that is relatively flat vertically, in which case the strut channels can be mounted directly to the bumper. If the bumper
10
INSTALLATION
is not flat, some other type of brackets, supports, etc. will need to be used to attach the strut channels to the front of the vehicle. Mount the two strut channels approx. one-foot from the ground to the bottom of each strut channel. A drawing is included in Appendix A.
Once the strut channels are mounted, use standard strut channel shelf brackets (Heath P/N 2510654) to mount to the strut channels with two bolts (Heath P/N 2510655) and channel-nuts (Heath P/N 2510653) each. The OMD crossbar can then be attached to the shelf brackets with the insulated u-bolts provided (Heath P/N 2510657).
Once this installation is complete, the height of the OMD can easily be adjusted by loosening the bolts attaching the shelf brackets to the strut channel and sliding the OMD up or down to the desired position. In addition, the shelf brackets can be mounted facing upward so that the OMD can be extended another 10” up toward the hood. The shelf brackets can also be mounted downward so that the OMD can be extended another 10” down toward the ground.
Additional Notes On Crossbar Installation:
One of the most important points to consider when installing the crossbar assembly is airflow. Unlike the flame ionization technology, which has a vacuum pump to bring the sample to the analyzer, the OMD relies strictly on the flow of gas through the optical path. Therefore, it is of the utmost importance that you install the OMD in such a way as to allow the gas to flow continuously through the optical path. It is important that you don’t configure your mounting brackets in a way that creates a dead space thus preventing gas from flowing freely across the optical path. A drawing illustrating this problem is included in
11
INSTALLATION
Appendix A at the end of this manual. Many vehicles have vents below the bumper to allow airflow into the engine compartment. This is a good place for the optical path. If you attach the OMD crossbar at bumper height, then hang the optical path slightly below the bumper and gas will flow across the optical path then on into the engine compartment.
The best location for your OMD crossbar assembly will vary from vehicle to vehicle. However, one principle remains the same, install the crossbar in such a way as to allow gas to freely flow across the optical path.
Power box installation:
The original suggestion was if the vehicle had sufficient room, that the Power Box should be mounted under the hood. This reasoning was to eliminate the need for routing multiple cables into the vehicle cab. However, field experience indicates that in some instances, heat from the vehicle engine coupled with high ambient temperatures can result in Power Box failures. The current suggestion is to mount the Power Box inside the cab of the vehicle. The first thing to consider when mounting the power box inside the cab is cable length. The standard cables are at least long enough to mount the power box directly behind the front seat on most vehicles. If you desire to mount it further back, check the length from the desired mounting position to the OMD crossbar assembly mounted in front of the front bumper.
After determining where you want to mount your power box, simply place the box in the desired spot and mark through the mounting holes on the ears of the box with a pencil. Drill starter holes, then attach the box with four # 8 x ½” sheet metal screws.
12
INSTALLATION
Cable assemblies installation:
Each cable assembly for the OMD is uniquely constructed so that it cannot be connected to the wrong mating connector. First, you will need to determine which cable goes where. If you mounted the power box under the hood, then you will only need to route the display cable either through the firewall or through the floorboard. If you mounted the power box inside the cab, you will need to route the other three cables into the cab as well.
Unless a hole large enough to route the cabling through already exists, you will need to drill one. A hole approximately 1-1/8 inches in diameter should be sufficient to route one or three cables. A 1-1/8 inch rubber grommet should be used in this hole to protect the cables from damage. A 1-1/8 inch rubber grommet may be purchased from Heath as P/N 2510686.
13
INSTALLATION
When routing cables from the cab to the front of vehicle, fasten the cables to fixed parts of your vehicle with tie wraps. Tie wraps are available from Heath as P/N 9996350 for 4” (per 1,000) and P/N 0419180 for 8” (each). Be sure to route cables away from exhaust components and shift linkages.
The OMD requires six amperes of continuous current. So connect the system power cable to the vehicle’s battery. Do not connect the system power cable to the cigarette lighter or anywhere else that is not rated for at least six amperes. When connecting power, polarity must be observed. If the positive and negative leads are reversed, the fuse will blow immediately. The red wire should be connected to the positive terminal and the black wire connected to the negative terminal of the battery.
Note:
Connect the battery cable up last. Be sure that the receiver cable is connected prior to making the battery connection. Damage to the electronics may occur if not properly connected
Display installation:
The requirements for installing the display include mounting the display at an operator friendly height and position and then plugging in the display cable. A floorboard mounting pedestal or a dashboard console are two possible mounting methods. These types of devices are available from suppliers of cellular phone equipment.
14
INSTALLATION
Display Connectors:
There are three connectors on the side of the display box. The first is for the system cable which comes from the power box connector marked “Display.” Next is the RS-232 connector, which is to connect a computer for data logging, etc. Then there is a 1/8” phone jack for connecting an external speaker. When a phone plug is plugged into the speaker jack the internal alarm speaker is disabled.
Vehicle Grounding Strap
A vehicle-grounding strap is included in the OMD mounting kit. The purpose of this strap is to prevent the buildup of an Electro-static charge, thereby preventing any condition of Electro-static discharge between the operator and the display unit, which can cause a reset condition of the display unit. The ground strap mounting location on the vehicle is at the discretion of the customer. To ensure proper operation, however, certain conditions need to be observed.
·Ground strap must be mounted to the vehicle chassis. Avoid mounting to any surface that is painted or plated.
·Ground strap should have a minimum of three inches of the strap in contact with the surface being traveled over.
15
INSTALLATION
·Verify that the mounting location of the strap will not cause it to come in contact with any rotating parts, such as drive wheels or drive shaft.
NOTE: Ground strap mounting hole is .475”ID and strap length is 30”.
Protective Cage
Because the main part of the OMD is located on the front bumper of the survey vehicle, it is in danger of being damaged due to the possibility of bumping into something. We recommend that a cage be built around the OMD to protect it.
It would be nearly impossible to build one cage that would fit on every type of vehicle used for mobile surveying. Therefore Heath does not offer one at this time. We recommend that you take your vehicle to a local fabrication shop to custom build one for your vehicle.
Following are a few photos of typical protective cages presently in use.
16
INSTALLATION
Photos of Protective Cages
17
Chapter III
OPERATING PROCEDURES
Start Up:
1)Turn on the SYSTEM POWER by pressing the “SYSTEM POWER” button. The red LED above the SYSTEM POWER button will light up and a message will appear on the screen stating, “PUSH DISPLAY FUNCTION TO CONTINUE.” Press the Display Function button twice to enter the normal operating mode.
If the system has been off for more than several seconds, a “SYSTEM WARMING UP,” message will be displayed. The system will require up to approximately 15 minutes before a beep will be heard and a message prompting the operator to, “TURN ON THE LIGHT SOURCE” will be displayed.
2)Turn on the LIGHT SOURCE if not done so already by press-
ing the “LIGHT SOURCE” button. The red LED above the LIGHT SOURCE button will light up and normal operation of the system will begin. If the vehicle will be turned off for a break, turn off the LIGHT SOURCE to save the automobile battery, while keeping the System Power on. A message prompting the operator to turn on the LIGHT SOURCE to resume operation will be displayed. System current consumption with the light is approximately five amperes while system current consumption without the light is less than one and one half amperes, which can be sustained by a good automobile battery, without the use of the engine, for at least 12 hours without causing starting problems. However, extreme cold conditions may require the vehicle to remain running as battery capacity drops significantly with reduced temperature.
3) Allow time for the instrument to stabalize. This may take 45 to
18
OPERATING PROCEDURES
60 minutes. The system is stable when the PPM readings become consistant.
4)Press the CALIBRATION TEST button. The red LED above the CALIBRATION TEST button will light up and a small internal cell containing methane will be placed in the optical path. This test cell will remain in the light path for approximately five seconds unless the button is held down. After five seconds the cell will return to its normal position and the red LED will turn off. The increase in methane above the background should be shown on the calibration data sheet that was shipped with your instrument. In other words, if the baseline on the display at the time of the calibration is 2 PPM and the calibration data sheet indicates that the calibration cell contains the equivalent of 15 PPM of gas, an increase in signal level from 2 to 17 PPM will be expected when the CALIBRATION TEST button is pressed. Some deviation from this exact number is acceptable as indicated by the range on the data sheet. It is good practice to occasionally press the CALIBRATION TEST button during the daily operation of the system to insure that the system is operating properly.
The concentration of the gas within this test cell is actually much higher than the reading listed on the data sheet. The reading obtained from this test cell is equivalent to the reading of a gas cloud that fills the entire volume within the light path, that is, the volume between the lens on the lamp assembly and the lens on the receiver assembly.
5)Set the Audible ALARM SETPOINT by pressing either the ALARM SETPOINT UP or DOWN button. The audible alarm will be sounded if the present methane level is greater than the ALARM SETPOINT level. Holding either the up or down ALARM SETPOINT button will enable the auto scroll
19
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