Online Truing FAQs
- How do I know if my collector rings/commutator would benefit from Cutsforth™ Online Truing?
When you experience excessive brush vibrations (> 6 Mils), arcing, grooving, or photographing (also called imaging, ghosting or footprinting) on your ring or commutator. One or more of these issues likely makes your collector rings a good candidate for Online Truing.
- How long has Cutsforth™ been performing Online Truing?
Our company has been performing our Online Truing process on rings and commutators since 1991.
- How safe is Online Truing for collector rings and commutators?
We have safely performed truings on units around the world since 1991 and have never had a serious injury in any plant while truing.
- How much time does it take Cutsforth™ to perform the Online Truing process?
The time varies from a 2-10 hours depending on the condition of the collector rings or commutator.
- Do we need to reduce the load on our generator when the Online Truing service is in progress?
No, this is not necessary. The Online Truing process can be safely performed at full load.
- How do Cutsforth™ techs know what the run-out is when the ring is at full speed?
Our service techs measure the movement of the brush with a vibration analyzer in mils displacement. Basically, a round ring will register a low reading (generally < 2 mils) and an out of round ring will register high readings (> 6 mils is over the OEM recommended limit).
- Is the Online Truing really as accurate as other machining processes?
The process is often more accurate at creating a round surface because the work is performed on the generator while at normal operating speed and temperature. A round ring on turning gear does not always equal a round ring online.
- How do I know if my collector ring has enough life left for Online Truing?
As long as there is still a helical groove, it can be trued.
- Should I be concerned about our unit being tripped during this process?
The biggest risk of tripping a unit comes from the ground detection system. Service techs will inspect and monitor the unit for oil contamination and the collection of particles to avoid alarming the ground detection system. In rare cases, if the oil film is severe enough, they may choose to not proceed with the process until the oil leak is resolved. Cutsforth™ has tripped < 0.1% of the units it has performed Online Truing on over the past 20 years.
- How much lead-time does Cutsforth™ need to schedule Online Truing?
If you believe your unit is in an emergency state, we can usually respond within 24 hours for an expedited charge. If your unit can wait, we will work with your plant to schedule it in a timely manner.
- Who can perform this service?
All of our field service technicians are experienced and capable of performing Online Truing at your plant.
- What if I discover that the spiral groove in the collector ring is missing in places?
No problem! If tolerances allow, Cutsforth™ can restore the spiral groove at your next scheduled outage. Most collector rings are able to be re-grooved once in their lifetime. The minimum recommended depth of a helical groove is 0.03″.
Removable Carbon Brush Holder FAQs
- What types of generators benefit from Cutsforth™ EASYchange® carbon brush holders?
Our carbon brush holders are currently installed on gas and steam turbines, hydroelectric and at nuclear power plants. Other retrofits include chemical plants, paper mills, and oil & gas refineries. From the smallest power producers to some of the nation’s largest power companies, Cutsforth™ brush holders are quickly becoming the BEST choice for an in-service removable brush holder. In addition to the United States, Cutforth brush holders have been installed overseas in several countries.
- What brands of generators are Cutsforth™ EASYchange® carbon brush holders installed on?
General Electric, Westinghouse, Allis Chalmers, Electric Machinery, Alstom, ABB, ASEA, GM, Siemens and Hitachi.
- Why should I consider a retrofit with Cutsforth™ EASYchange® carbon brush holders?
Our brush holder will bring increased personnel safety, increased collector ring and brush rigging reliability, and decreased maintenance costs to your plant.
- What problems will Cutsforth™ EASYchange® carbon brush holders address on my generator?
Arcing, brush binding, poor terminal connections, poor spring pressure, and photographing.
Our brush holders can reduce collector ring wear and improve and protect the critical brush-to-ring connection.
- How long does a Cutsforth™ EASYchange® carbon brush holder retrofit take?
Entire retrofits can usually be completed in one business day. The Cutsforth™ team works with your company and/or outage coordinators to get our brush holders installed during your outage.
- How long has Cutsforth™ EASYchange® holders been operating in generators?
Our holders have been in service and operating for about 20 years. There are currently over 40,000 Cutsforth™ EASYchange® brush holders in operation worldwide.
- How reliable has Cutsforth™ carbon brush holder been?
We are proud to proclaim that we have never had a failure to date from our brush holder.
- Has Cutsforth™ carbon brush holders ever been installed on DC motors?
Yes, on larger critical applications. We have our brush holders on larger DC motors such as
- Can Cutsforth™ EASYchange® carbon brush holders be installed on commutators, pilot exciters and Alterrex ring sets?
Yes, The installation variables are the brush size, ring or commutator size (width) and the existing brush rigging setup.
- How can we clean the brushes and collector rings?
Denatured alcohol combined with clean, lint free rags is the best way to clean the brush holders and collector rings.
- How can I see a demonstration or receive more information?
We regularly schedule online demonstrations, which consist of a web-based meeting and conference call for plant personnel. Please schedule a demo by filling out this form.
Brush Condition Monitoring (BCM) FAQs
- Which brush holders are compatible with Cutsforth™ Brush Condition Monitoring (BCM)?
The monitoring system only works with Cutsforth™ EASYchange Holders.
- Are the Cutsforth™ Brush Condition Monitoring sensors wireless?
Yes, and they wirelessly connect to an easy – to – read touchscreen user interface, and the control room via PI or InsightCM™.
- What is the standard lead and installation time for Cutsforth™ Brush Condition Monitoring?
Brush Condition Monitoring is a simple and minimally invasive installation, usually completed within one eight-hour shift. Sensors fit easily inside EASYchange brush springs wirelessly talking to the monitors and plant personnel. If plants already own EASYchange holders, BCM installation is even easier and quicker.
- How long does the sensor last in the Brush Condition Monitoring system?
The operational battery life of the sensors is 2-4+ years but may vary depending on the user-defined measurement interval and environmental temperature. The BCM system will display a low battery warning roughly 30 days prior to the end of the battery’s life. The storage battery life is roughly 10 years.
- Should we change the Brush Health Sensor (BHS) every time we change a brush?
The Brush Health Sensor does not need to be replaced with each brush change. The sensors should be replaced at the end of their battery life.
- How do I pair a sensor?
Touch the brush location icon on the screen where the sensor will be installed. Touch “Press to Pair New Sensor” on the screen. Press the rubber button on the sensor, which is shown in the graphic; one short press. You will receive a confirmation message on the screen when the BHS has successfully paired.
- How do I unpair a sensor?
Press and hold the rubber button on the Brush Health Sensor for roughly 3 seconds. The sensor is unpaired once the light on the sensor, opposite side of the button, flashes 3 times.
- How can I confirm if a sensor is already paired and where it is paired to?
While viewing the main screen of the BCM system, single press the button on the BHS in question and that sensor’s brush location icon will flash with a blue border for a few seconds. If none of the brush location icons flash, that sensor is not paired to any of the brush location icons.
- Can a new BHS be installed on a used brush?
Yes, both new BHS and used BHS with battery life remaining can be installed on new and partially used brushes alike. Remember to, in both cases, single press the sensor button after the sensor and brush are installed in the holder, before it is installed onto the generator, to reset the brush length data.
- What is the “Clear Brush Length Warnings” button on the brush detail screen?
When a brush length gets below the user-set threshold set in the CONFIG screen, that brush location icon will turn red, and an exclamation point will flash. Pressing this button will clear the warning until the next time the brush measures low.
- What do I do if I see “No Data” on a brush location icon?
Attempt the following troubleshooting steps in this order:
- Press the button on the associated sensor once, and watch the BCM screen to see if the location in question updates with data within a few seconds.
- If step 1 is unsuccessful, unpair and re-pair the BHS following the instructions listed above then wait for the measurement interval to pass (default is one hour) to see if the location begins showing data.
If steps 1-2 are not successful, please submit a support request at Cutsforth.com/support
Shaft Grounding FAQs
- How long do Cutsforth™ grounding ropes last?
The life expectancy of the grounding ropes is approximately 12 months, but this depends greatly on the environmental factors present. The main contributors to decreased rope life are mechanical wear and electrical wear. Mechanical wear increases with increases in factors like shaft surface speed, shaft surface roughness, and contaminants present on the shaft. Electrical wear occurs mainly on the grounding rope, and less on the metering rope, as the grounding rope carries most of the electrical load. For this reason, we typically find the metering rope to last slightly longer than the grounding rope.
- Is there enough contact on Cutsforth™ braided ropes to properly ground the shaft?
Yes, and as the braided ropes wear, the copper or silver ropes create hundreds of very small contact points to assist in the grounding process.
- Where should the shaft ground wire be terminated?
The purpose of the Shaft Grounding System is to electrically bond the shaft to the unit case immediately adjacent to the shaft to provide a safe and desirable path for the flow of shaft current, and to prevent the flow of shaft current through destructive paths, such as through bearings. Cutsforth™ requires the shaft ground termination to be the lower half of the generator, turbine, or coupling case in the immediate vicinity of the Shaft Grounding Assembly. Examples of unacceptable grounding locations are structural steel, plant AC ground, or an existing grounding pad that requires an extended wire run to reach.
- Can I change Cutsforth™ Shaft Grounding or metering ropes while the generator is online?
Yes, Cutsforth™ Shaft Grounding System is designed to allow safe and easy online rope changes.
- What is the minimum shaft diameter on which the Shaft Grounding Assembly can be installed?
The minimum shaft diameter on which the Shaft Grounding Assembly can be installed is 5 inches.
- What is the minimum width requirement at the shaft grounding location for the Shaft Grounding Assembly?
Cutsforth™ Shaft Grounding Assembly features a narrow profile design which only requires 1.5 inches of shaft space.
- What is the temperature rating of the Shaft Grounding Assembly?
The Shaft Grounding Assembly is rated to 300°F (150°C). All voltage and current monitoring equipment is rated to 158°F (70°C).
- Does Cutsforth™ Shaft Grounding work on large synchronous and induction motors?
Provided enough space is available on the shaft, the Cutsforth™ system will provide grounding.
Shaft Ground Monitoring FAQs
- What voltage and current readings should I expect on my generator?
The OEM usually provides nominal voltage and/or current expectations. “Normal” shaft voltage and current levels vary widely from generator to generator, even two of the same make and model. Establishing a baseline is crucial for proper analysis. We recommend running fresh grounding ropes on a clean shaft surface and monitoring your equipment for a month or so to determine the normal shaft voltage and current ranges for each of your units. From there, focus on the trending of those values. A departure from the normal voltage and current ranges you have established can be a strong indicator that maintenance is warranted.
- What should I do if my shaft voltage and/or shaft current exceed my established acceptance criteria?
The leading cause of increases in shaft voltage is a deteriorated shaft-to-rope contact, either by way of contamination or shaft surface deterioration. In cases like this, cleaning the shaft will typically lower the voltages back below the acceptance criteria. If a more aggressive cleaning is required, inquire with Cutsforth™ about a shaft stoning service. If you have any questions or concerns about the shaft voltage or current levels on your system, reach out to Support@Cutsforth.com.
- Do we need Cutsforth™ Shaft Grounding Assembly to implement Cutsforth™ Shaft Ground Monitoring systems?
Yes, our Shaft Ground Monitoring systems are compatible with Cutsforth™ grounding ropes.
- What are the differences among the Cutsforth™ Shaft Ground Monitoring systems?
Remote Meter Point: Requires a plant technician to use a multi – meter interfaced with the remote test points in order to determine shaft voltage and current. Assurance Shaft Ground Monitoring: measures and displays in real time voltage, current, and ground rope status. Additionally, the system can pass the real time measurements to a DCS or historian. Premium Shaft Ground Monitoring: continuously measures voltage, current, and ground rope status. The system provides multi – level alarming and time domain waveforms for both voltage and current for analysis. Waveform analysis can detect a wide range of defects, including poor shaft conditions to over – heating of the stator core.
Electro - Magnetic Interference (EMI) Monitoring FAQs
- Is the data review a manual process, or is it automated?
The data collection process and assessment of the content within the time domain signals is automated by the Cutsforth™ system. Condition alarms can be set based on the type of signal, e.g., arcing or partial discharge, and the energy content in microvolts. Trend features are available for future trend analysis by subject matter experts.
- What are some ‘rules of thumb’ suggesting which failures may be associated with each frequency?
The important aspect is understanding where the CT is placed, i.e., the generator or a transformer, and the content of the signal, for example arcing or partial discharge.
- How is Partial Discharge Monitoring different than Electro – Magnetic Interference Monitoring?
Usually, Partial Discharge Monitoring uses capacitive couplers on bus work to detect changes in insulation status of windings. Additionally, many Partial Discharge systems measure the time difference between the arrival of signals to approximate the location where a partial discharge occurs. However, Partial Discharge Monitoring ignores other types of discharges, such as arcing and coronal discharges. EMI Monitoring detects Partial Discharge, as well as Arcing, Coronal and Gap Discharges, Sparking, and other signals associated with other discharge events. These events occur through High Frequency Current Transformers that convert radiated or conducted RF signals emanating from the defects to current values that can be assessed for content and severity.
- What are the benefits of continual monitoring over 3rd party annual monitoring?
Third party vendors visiting plants on an annual basis are expensive, and only capture a miniscule snapshot of the generator’s health. Whereas, continuous EMI Monitoring is a one-time purchase. The system creates a power spectrum and time domain waveforms from thousands of frequencies allowing plants to measure and archive data over time to form a more comprehensive view of your generator’s health. This option allows plants and companies ownership of their data without having to pay to access it.
- How do I interpret the data once I have it?
With Cutsforth™ EMI Assessment Algorithm, plants are able to automatically categorize time domain waveforms to establish which failure modes are present. Cutsforth™ also offers access to Subject Matter Experts to assist in reading and analyzing data.
- Do I need an outage in order to install the Cutsforth™ Electro – Magnetic Interference system?
No, EMI Monitoring is a non – invasive installation process requiring NO outages.
Rotor Flux Monitoring (RFM) FAQs
- What are shorted turns that Rotor Flux Monitoring detects?
Failure of insulation between windings in a generator.
- Does Cutsforth™ manufacture and install flux probes?
Cutsforth™ does not manufacture or sell probes. However, our Rotor Flux Monitoring system is agnostic to probes within the industry.
- On which flux probes can Rotor Flux Monitoring be installed?
Any probe that is analog, providing +/- 10 volts inputs.
- What are the benefits of continual monitoring over 3rd party annual monitoring?
Third party vendors visiting plants on an annual basis are expensive, and only capture a miniscule snapshot of the generator’s health. However, continuous RFM Monitoring is a one-time purchase. The system collects data and creates waveforms from thousands of frequencies allowing plants to measure and archive data over time to form a more comprehensive view of your generator’s health. This option allows plants and companies ownership of their data without having to pay to access it.
- How do I interpret the data once I have it?
Cutsforth™ offers access to Subject Matter Experts to assist in reading and analyzing data.
- Do I need an outage in order to install the Cutsforth™ Rotor Flux Monitoring system?
No, RFM Monitoring is a non – invasive installation process requiring NO outages.