Frequently Asked Questions

Following are frequently asked questions about E/One hydrogen monitoring equipment and hydrogen gas analyzers. If you need more information or a product manual, please contact us for assistance.

GCM-X

GCM-A

GGD II

GGA

DHCP

Generator Condition Monitor, Explosionproof Design (GCM-X)

Application

• What detection principle is used by the GCM-X?
  The GCM-X uses an Ionization Chamber to detect the thermal decomposition of materials such as epoxy paint, core lamination, enamels and other insulating materials within the generator.
• If my generator already has RTDs or thermocouples, why do I need a GCM-X?
  The RTDs or thermocouples are only installed in the generator core (stator) and typically respond slowly to an overheat. The GCM-X will respond at the earliest stage of overheat and can detect overheat in all areas of the generator.
• Can the GCM-X be combined with other equipment as a package?
  Yes; the GCM-X can be provided as a module with other equipment as part of a larger hydrogen skid.
• Are there radioactive materials in the GCM-X?
  Yes; the ion chamber detector has thoriated gas lantern mantles contained within it. Thorium is the active ingredient within the mantles.
• What size generators can use a GCM-X?
  The only generator requirement is that it is hydrogen-cooled and has sufficient fan differential pressure to create a flow through the GCM-X. GCM-Xs have been used on generators as small as 20 megawatts.

Installation

• What are the supply power requirements?
  Input voltage can be 100 VAC to 250 VAC with a frequency of 50 to 60 Hz, +/- 10%, at 100 watts.
• Can the GCM-X be located outside?
  The operating temperature range for the GCM-X is 0 to 65 degs C (32 to 149 degs F). Steps need to be taken to ensure the operating temperature does not go outside of this range. The GCM-X also needs to be protected from rain, snow and salt air.
• How is the GCM-X connected to the generator?
  Flange connections to the generator fan suction, generator and fan pressure and vent lines. Refer to the GCM-X brochure to see the connections.
• Can the GCM-X be connected to the same generator tapping points as other instrumentation?
  It is recommended that the GCM-X have dedicated piping to the generator to eliminate any chance of hydrogen flow interruption. Instruments, such as generator gas dryers, can cause the flow through the GCM-X to vary.
• Where should the GCM-X be located?
  Ideal location is on the turbine deck and as close to the generator as possible.
• Can the GCM-X be located in a hazardous location (Hydrogen)?
  Yes; the GCM-X is designed to operate in a Class I, Zone 2, Group IIB+H2 environment (which satisfies North American Electric Code Class I, Div 2, Group B).
• Can the GCM-X interface with my DCS?
  Yes; the GCM-X has two 4-20 mA output signals: one for the “ICD Output” and one for “Flow”; and three output relays, one for “Warning”, one for “Trouble” and one for “Verified Alarm.”
• Is it necessary to connect the GCM-X to an external recording device?
  It is strongly recommended the that GCM-X 4-20 mA outputs signals, both ICD output and flow output, be connected to the DCS so the outputs can be reviewed should a Verified Alarm occur.
• Is a separate remote panel available for the GCM-X?
  Yes, the GCM-X can be equipped with a remote panel.
• Do you recommend using filters on the inlet and outlet line of the GCM-X to prevent oil contamination?
  E/One recommends that proper piping practices be followed to prevent oil contamination. This will include the use of drip legs on the inlet and outlet lines and an oil moisture trap on the inlet. To prevent the filtering of overheated particulation, the oil moisture trap provided by E/One is the only type filter that should be used.

Operation

• How can I verify a collector sample was taken when my Auto Sampler is set in the Auto position?
  The GCM-X software contains an event log that will note the Auto Sampler on and off time and date.
• How long does the Auto Sampler take a sample?
  The Auto Sampler is set, at the factory, to take a 10-minute sample. The Auto Sampler time is programmable and can be set to a sample time up to 30 minutes.
• How often should I change the verification filter?
  As long as the verification filter is not contaminated with oil, it should never need to be changed. The verification filter is normally not in the hydrogen stream and is only used to verify an alarm condition. The filter can be tested by noting the hydrogen flow under normal operating conditions and noting the hydrogen flow with the verification filter energized. If the filter is good, there will be no change in the hydrogen flow.
• The collector sample data sheet references hot and cold gas temperatures. What are these?
  The hot and cold gas temperatures refer to the temperatures of the hydrogen gas entering and exiting the hydrogen gas coolers.

Troubleshooting

• What happens if my GCM-X becomes contaminated with oil?
  Oil contamination will affect the operation of the GCM-X Ion Chamber Detector (ICD). If the oil contamination is significant, the ICD may have to be replaced by E/One's Field Service Group. Contact Field Service at 01.518.579.3035.
• The GCM-X goes into “Warning” frequently.
  The Warning provides an early indication that the output from the ion chamber detector has dropped below a set point, which is factory set at 70 percent. The Warning level can be changed by selecting WARNING LEVEL from the SETUP MENU. Contact E/One Field Service at 01.518.579.3035 if you are getting frequent warnings.

Generator Condition Monitor, Air-Cooled (GCM-A 2)

Application

• How does the GCM-A operate?
  The GCM-A uses a Wilson Cloud Chamber to detect submicron particles that were created by overheated insulating material.
• Do I need a fan differential pressure or case pressure for the GCM-A to operate?
  No; the GCM-A has an integral blower that draws cooling air from the generator case.
• Can the GCM-A be part of a larger monitoring package?
  Yes, the GCM-A can be packaged with other monitoring equipment, such as partial discharge analyzers and vibration systems to create a more complete monitoring package.
• How is the GCM-A different from a partial discharge monitoring system?
  A partial discharge analyzer is used to monitor the integrity of the high voltage windings, whereas a GCM-A is used to detect overheat of insulating material anywhere in the generator.
• If I already have thermocouples, why do I need a GCM-A?
  The RTDs or thermocouples are only installed in the generator core (stator) and typically respond slowly to an overheat. The GCM-A will respond at the earliest stage of overheat and can detect overheat in all areas of the generator.
• Does the generator need to have a closed loop cooling system?
  No; the GCM-A is capable of detecting submicron particles in generators that have open loop cooling systems as well.

Installation

• How is the GCM-A connected to the generator?
  The GCM-A has two sampling ports, one that takes a sample of the ambient air outside the generator and one that takes a sample from inside the generator case or cooling air. The ambient air sample is usually collected using one sample head. The cooling air sample is usually collected through a sampling probe that is designed according to the generator coolers and cooling air flow.
• What are the supply power requirements?
  The GCM-A can either be powered by 115 VAC, 50/60 Hz or 230 VAC, 50/60 Hz.
• Can the GCM-A be located outside?
  The operating temperature range for the GCM-A is 0 to 50 degs C (32 to 122 degs F). Steps need to be taken to ensure the operating temperature does not go outside of this range. The GCM-A system is housed in an enclosure that provides some protection from the environment but needs to be protected from rain, snow and salt air.
• Can the GCM-A be connected to my DCS?
  Yes, the GCM-A has six relays: alarms, warnings, and troubles; and three 4-20mA signals that can be connected to the DCS.
• Do I need to connect the output of the GCM-A to a recording device?
  Yes, it is recommended the 4-20mA signals be connected to the DCS so the outputs can be reviewed should an alarm occur.
• How far away from the generator can the GCM-A be located?
  The GCM-A should be located as close as possible to the generator to minimize the length of tubing and number of bends.

Operation

• How do I adjust the sample air flows to the GCM-A?
  A DP gage is used to monitor the differential pressure across an orifice located in the zone manifold. The flow rate is set to 14 LPM.
• Do I need to calibrate the GCM-A?
  No; the only setup that needs to take place is that the flows need to be adjusted.
• Is the water used in the GCM-A special?
  The GCM-A requires distilled water to be used.
• How often do I need to add distilled water to the GCM-A?
  The GCM-A has a level sensor that will indicate when distilled water must be added.
• How often do the zone manifold filters need to be changed?
  The GCM-A will issue a flow fault when the filters become blocked. The recommended preventive maintenance interval is three months.

Troubleshooting

• Is there a way to test the GCM-A to ensure it is operating properly?
  Yes, incense sticks or a lit match can be used near the ambient sampling system head to create submicron particles. Resistors coated with insulating paint can also be overheated in the generator casing to simulate overheating.

Generator Gas Dryer II

Application

• Why is it necessary to maintain dry hydrogen in the generator?
  Efficiency and risk mitigation: higher hydrogen dew point increases windage losses and can lead to stress corrosion cracking, insulation breakdown and corrosion.
• What size generators can use a GGD II?
  The only generator requirement is that it be hydrogen cooled. GGD II has been used on generators as small as 20 megawatts.
• What takes place during column regeneration?
  The column being regenerated is heated to drive off the moisture and a small amount of dry hydrogen flows through the column to vent. This method is called "open loop generation."
• Why does the GGD II use hydrogen as a regeneration gas?
  Clean, dry hydrogen has been found to be the most effective gas in removing moisture from the drying medium.
• What is an acceptable dew point reading for my generator?
  Most generator manufacturers recommend the dew point be 0 degrees C or lower.
• Can the GGD II be used to dry air or CO2?
  No, the GGD II is designed to only dry hydrogen.
• Can the GGD II be used while the generator is on turning gear?
  Yes; the GGD II incorporates a positive displacement blower that will circulate the hydrogen even when the generator is on turning gear.

Installation

• What are the supply power requirements?
  Supply voltages required are 400 VAC 50 Hz, or 460 VAC 60Hz, 3000 Watt, 3 phase
• How is the GGD II connected to the generator?
  Flange connections to the generator fan suction, generator fan pressure and vent lines.
• Can the GGD II be connected to my DCS?
  Yes, there are two 4-20 mA output signals for the inlet dew point and outlet dew point as well as the followng relay signals: dew point high, trouble, regeneration, blower motor status and circuit breaker status.
• Can the GGD II be located outside?
  The operating temperature range for the GGD II is 0 to 52 degs C (32 to 125 degs F). Steps need to be taken to make sure the ambient temperature does not go outside this range. The GGD II also needs to be protected from rain, snow and salt air.

Operation

• How often do the dew point sensor need to be calibrated?
  The dew point sensors should be recalibrated annually.
• How frequently does the oil in the positive displacement blower need to be changed and what type of oil should be used?
  The oil must be changed annually. The approved oil is Pneulube ISO 100 snythetic oil.
• What gases are recommended to purge the GGD II prior to maintenance?
  E/One recommends that either Nitrogen or Carbon Dioxide be used as a purge gas. If Carbon Dioxide is used, the columns will have to be regenerated without the blower/motor on prior to being put in service. Using Nitrogen as a purge gas does not require the columns to be regenerated.
• How do I know which column is drying?
  LEDs located on the control/display panel indicate which column is drying.
• When should the inlet coalescing and outlet particulate filters be replaced?
  The filters should be changed annually. Note: The O-rings in the filter housings must be replaced at the time.

Troubleshooting

• How often does the molecular sieve (drying medium) need to be replaced?
  The drying medium should be inspected annually and replaced if necessary. If the hydrogen is free of oil, the drying medium will last over five years. When material color changes from off-white to black or brown, the medium has been contaminated and should be replaced.
• Do the heating elements in the columns ever need to be replaced?
  No; the heating elements are designed for the life of the GGD II.
• Does the actuator require any maintenance?
  Contact E/One Field Service at 01.518.579.3035 with your GGD II model and serial number for more information.

Generator Gas Analyzer

Application

• What detection principle is used by the GGA?
  The E/One GGA uses thermal conductivity as the detection principle.
• Can the GGA be used while gassing and degassing the generator?
  Yes. The E/One GGA is a triple-range gas analyzer that can be used during Normal operation (H2 in Air) and during the gassing and de-gassing process (H2 in CO2 and Air in CO2).
• What size generators can use a GGA?
  The only requirement is that the generator is hydrogen-cooled. GGAs have been used on generators as small as 20 megawatts.
• What is the maximum operating pressure of the GGA?
  The GGA can be used on generators with case pressure as high as 100 psig (7 bar).
• Can the GGA be used in a hazardous location (hydrogen)?
  Yes. The GGA is designed to be used in a Class I, Zone 2, Group IIB+H2 environment. This satisfies NFPA/NEC 500 Class I, Div 2, Group B.
• Does the GGA require a fan differential pressure to operate?
  No. If the generator is not operating at full speed, the hydrogen sample leaving the GGA can be vented to atmosphere, providing a small hydrogen flow through the analyzer sensor cell.
• Will changing my case pressure affect the readings of my GGA?
  No; case pressure has no effect on the performance of the GGA.
• Can the GGA be combined with other equipment as a package?
  Yes; the GGA can be provided as a standalone unit or part of a more complex hydrogen auxiliary skid.

Installation

• Does E/One recommend using filters on the inlet and outlet of the GGA?
  E/One recommends proper piping practices be followed to prevent oil contamination. This will include the use of drip legs on the inlet and outlet lines and a filter on the inlet.
• Can I connect the GGA to my DCS?
  Yes; the GGA has a 4-20 mA output for gas purity in addition to the following relays: Warning, Trouble and Normal.
• What is the supply voltage required to operate the GGA?
  The GGA can either be powered by 115 VAC, 50/60 Hz or 230 VAC, 50/60 Hz.

Operation

• Can the GGA operate while the generator is on turning gear?
  Yes. If the generator is not operating at full speed, the hydrogen sample leaving the GGA can be vented to atmosphere, providing a small hydrogen flow through the analyzer sensor cell.
• Can the GGA be used while gassing and degassing the generator?
  Yes. The E/One GGA is a triple-range gas analyzer that can be used during Normal operation (H2 in Air) and during the gassing and de-gassing process (H2 in CO2 and Air in CO2).

Troubleshooting

• Is there a process for removing oil from my GGA?
  E/One's Field Service group is equipped to perform oil decontamination. Contact Field Service at 01.518.579.3035.

Dual Hydrogen Control Panel

Application

• What application is the DHCP used for?
  The DHCP is designed to monitor and control hydrogen purity in generators with scavenging type seal oil systems.
• Can the DHCP be used while gassing and degassing the generator?
  Yes. The DHCP has two triple range gas analyzers that can be used during Normal operation (H2 in Air) and during the gassing and de-gassing process (H2 in CO2 and Air in CO2).
• Can the DHCP be installed in a hazardous location?
  Yes. The DHCP is designed to be used in a Class I, Zone 2, Group IIB+H2 environment. This satisfies NFPA/NEC 500 Class I, Div 2, Group B.
• What detection principle is used by the analyzers in the DHCP?
  The E/One DHCP uses thermoconductivity as the detection principle.
• What is the maximum operating pressure of the DHCP?
  The DHCP can be used on generators with case pressure as high as 100 psig (7 bar).
• Can the DHCP be used on generators with vacuum type seal oil systems?
  No. The DHCP is specifically designed to be used on generators with scavenging type seal systems.

Installation

• What are the supply power requirements for the DHCP?
  The DHCP is powered by 115 VAC, 50/60 Hz or 230 VAC, 50/60 Hz.
• Can the DHCP be connected to my DCS?
  Yes. Please contact E/One for details.
• Can the DHCP be located outside?
  The DHCP can be provided in NEMA 3R enclosure for outdoor installations. The ambient temperature range for the DHCP is 32 to 149 degs F (0 to 65 degrees C).

Operation

• Can I change the purifier cartridges while the DHCP is in operation?
  Yes. The purifier housings can be isolated and the filter cartridges can be changed.
• What determines when the DHCP will increase the scavenging rate to increase the hydrogen purity?
  There are two methods to energize the solenoid valves that will increase the scavenging rate: using the warning contacts located on the DHCP; or using the DCS to control the increased scavenging.
• How often does the DHCP require calibration?
  E/One recommends annual calibration.
• Can I read the hydrogen purity in the control room?
  Yes. Each analyzer in the DHCP has a 4-20mA output signal that indicates, during normal operation, the hydrogen purity. The 4-20mA signal equals 70 to 100% hydrogen purity.
• What are the Normal contacts used for?
  The Normal contacts indicate the operating mode of the analyzers. Normal operation is when the analyzers are monitoring H2 in Air and the 4-20mA signal equates to 70 to 100% hydrogen.

Troubleshooting

• Why do I get oil in my total flow meter and not in the analyzer flow meters?
  The oil may be coming from the TE and CE scavenging lines, which are unfiltered.
• Is there a process for removing oil from my DHCP?
  Yes, E/One Field Service is equipped to perform oil decontamination. Please call them at 01.518.579.3035.