We are having problem in the C-arm part of our Bi-plane Cath-labs system.The problem is the spark that occurs in the terminal base plate of the tube on the left side.The main question is what causes the spark ; is it possible that the cause is from outside the tube since pulse fluoroscopy at 50 kv 50 mA can be done normally and the spark does occur only in continuous fluoroscopy at 50 kv 0.5 mA.The spark damages the coimator board anf the stereo board at the C-arm control cabinet.Or does the defect of the board cause the spark ?Can anybody advise us on what is the cause.Wiring has been checked and other parts of the system are working well.
If the tube is the factor what should be done ?
rsmht@indosat.net.id
This is just from general experience and not based on your machine. 1) there shoud be a large grounf wire from the tube housing to the ground on the generator. 2) make sure the ground on the generator is good. 3)Make sure the shields on the HT cables are good. You have a grounging problem, there will never be a visable arc from the tube if properly grounded. Most modern systems isolate the tube housinf from the "C" arm. If you remove the grounds from the Tube there should read open from the tube housing to the "C" arm.
Is this a metal center section x-ray tube? The insert lead should be securely grounded at the HT transformer or metered through the anode MA circuit. If the insert lead is open, it could cause such a phenomenon.
Thank you for your advice.
This late after noon , our technician took the digital picture of the
internal arc and then they did some isolation and the arc decreased
dramatically but still persist.The correct grounding will be done tomorrow
and I will send you the digital picture of the arc before and after the
isolation attempt.The main spark evidently comes out of a cable that goes
into the tube housing.I will keep you posted.
Sir,
With or without isolation there should be no spark if the cables are in good condition and the system is properly grounded. What exactly do you mean when you say isolation? I reality there should be zero voltage differential between the tube housing and the C Arm. Another item to check is that the ma monitoring circuit is complete. If it is open at the transformer or the monitoring circuit is open voltage to the tube is floating with reference to ground and can cause a very unsafe condition.
If you want to contact me directly my private email is jkopf@optonline.net
i am agree with Jack Kopf, you need a good grounding and if you still feel there is some arcing left then you should arrange for a proper 150KV earth, i have faced this problem many times and proper grounding is best solution.if you need any more help you can contact me any time.
If after being sure that the tube, and Generator grounds are good look at the ma signal. The high-tension transformer is comprised of 2 75kvp transformers. One end of each winding set is tied to the tube and the other ends are tied to ground. On the anode side (+) you should find a circuit for the ma feedback. Normally there is a resistance inserted in series with this center winding from the anode to allow a voltage to be generated to allow monitoring of the actual tube current. If this circuit is open the anode side is no longer referenced to earth.
The high voltage cables are rated for 75 kvp to earth. In the event of a floating anode or cathode the potential from the cable core to ground could be well in excess of 75kvp. This could cause the cable insulation breakdown. Should this happen you will need new cables.
So far nothing you have described indicated a tube issue. The only exception might be if you have a metal insert tube and do not have the insert referenced to earth. An easy check for this is the tube port glass? Can you see the filaments? If you can see the filaments you have a glass insert.
Lastly when looking into the tube port window do you see air bubbles? If you have a glass insert and do not have bubbles in the oil it is most likely not a tube problem.
Some questions for you. 1) What system are you working on GE, Siemens?
2) At what kvp and ma does the arching start? Do you have a MAS meter on the system and if so what does it read when this happens? Do you have an invasive method to measure KVP (divider tank)? What does the kvp waveform look like?
If this system has a triode tank then maybe the blocking is not correct or the blocking triode is bad, otherwise it sounds like the tube is bad and breaking down at certain Kv's or the HT cables are bad perhaps there is a cut in them or the shielding has broken but I don't believe that it is a ground wire problem. To get a arc like you describe it is a bad HT cable, tube or triode in my opinion the arc feeds back thru the grounds and destroys the other boards! This was a common problem with older Siemens Pandoros generators before high frequency came out-- I have seen this a 100 times
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Abdul Radjak
Bi-plane Cath-labs problem
November 22, 2004 04:25
We are having problem in the C-arm part of our Bi-plane Cath-labs system.The problem is the spark that occurs in the terminal base plate of the tube on the left side.The main question is what causes the spark ; is it possible that the cause is from outside the tube since pulse fluoroscopy at 50 kv 50 mA can be done normally and the spark does occur only in continuous fluoroscopy at 50 kv 0.5 mA.The spark damages the coimator board anf the stereo board at the C-arm control cabinet.Or does the defect of the board cause the spark ?Can anybody advise us on what is the cause.Wiring has been checked and other parts of the system are working well.
If the tube is the factor what should be done ?
rsmht@indosat.net.id
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Jack Kopf
Re: Bi-plane Cath-labs problem
November 22, 2004 10:58
This is just from general experience and not based on your machine. 1) there shoud be a large grounf wire from the tube housing to the ground on the generator. 2) make sure the ground on the generator is good. 3)Make sure the shields on the HT cables are good. You have a grounging problem, there will never be a visable arc from the tube if properly grounded. Most modern systems isolate the tube housinf from the "C" arm. If you remove the grounds from the Tube there should read open from the tube housing to the "C" arm.
Good Luck
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Marty Kulis
Re: Bi-plane Cath-labs problem
November 22, 2004 05:15
Hi,
Is this a metal center section x-ray tube? The insert lead should be securely grounded at the HT transformer or metered through the anode MA circuit. If the insert lead is open, it could cause such a phenomenon.
Marty Kulis
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Abdul Radjak
Re: Bi-plane Cath-labs problem
November 23, 2004 10:39
Hi Jack ,
Thank you for your advice.
This late after noon , our technician took the digital picture of the
internal arc and then they did some isolation and the arc decreased
dramatically but still persist.The correct grounding will be done tomorrow
and I will send you the digital picture of the arc before and after the
isolation attempt.The main spark evidently comes out of a cable that goes
into the tube housing.I will keep you posted.
to rate and post a comment
Jack Kopf
Re: Bi-plane Cath-labs problem
November 24, 2004 01:32
Sir,
With or without isolation there should be no spark if the cables are in good condition and the system is properly grounded. What exactly do you mean when you say isolation? I reality there should be zero voltage differential between the tube housing and the C Arm. Another item to check is that the ma monitoring circuit is complete. If it is open at the transformer or the monitoring circuit is open voltage to the tube is floating with reference to ground and can cause a very unsafe condition.
If you want to contact me directly my private email is jkopf@optonline.net
Good Luck
Jack
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Abdul Radjak
Re: Bi-plane Cath-labs problem
November 24, 2004 06:19
The problem is with the tube because the arc still persist after regrounding.
A.Radjak.
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shahzad Ahmad
Re: Bi-plane Cath-labs problem
November 23, 2004 11:39
i am agree with Jack Kopf, you need a good grounding and if you still feel there is some arcing left then you should arrange for a proper 150KV earth, i have faced this problem many times and proper grounding is best solution.if you need any more help you can contact me any time.
to rate and post a comment
Abdul Radjak
Re: Bi-plane Cath-labs problem
November 24, 2004 06:16
After regrounding the arc still persist so it is now clear that the problem is with the tube.
A.Radjak.
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Jack Kopf
Re: Bi-plane Cath-labs problem
November 24, 2004 09:58
If after being sure that the tube, and Generator grounds are good look at the ma signal. The high-tension transformer is comprised of 2 75kvp transformers. One end of each winding set is tied to the tube and the other ends are tied to ground. On the anode side (+) you should find a circuit for the ma feedback. Normally there is a resistance inserted in series with this center winding from the anode to allow a voltage to be generated to allow monitoring of the actual tube current. If this circuit is open the anode side is no longer referenced to earth.
The high voltage cables are rated for 75 kvp to earth. In the event of a floating anode or cathode the potential from the cable core to ground could be well in excess of 75kvp. This could cause the cable insulation breakdown. Should this happen you will need new cables.
So far nothing you have described indicated a tube issue. The only exception might be if you have a metal insert tube and do not have the insert referenced to earth. An easy check for this is the tube port glass? Can you see the filaments? If you can see the filaments you have a glass insert.
Lastly when looking into the tube port window do you see air bubbles? If you have a glass insert and do not have bubbles in the oil it is most likely not a tube problem.
Some questions for you. 1) What system are you working on GE, Siemens?
2) At what kvp and ma does the arching start? Do you have a MAS meter on the system and if so what does it read when this happens? Do you have an invasive method to measure KVP (divider tank)? What does the kvp waveform look like?
Thanks
Jack
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shahzad Ahmad
Re: Bi-plane Cath-labs problem
November 24, 2004 10:46
but you mentioned it works good on pulse flouro, so i think your earth plate of gounding become weeken so you should check it.
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Kevin Cassidy
Re: Bi-plane Cath-labs problem
November 24, 2004 11:42
If this system has a triode tank then maybe the blocking is not correct or the blocking triode is bad, otherwise it sounds like the tube is bad and breaking down at certain Kv's or the HT cables are bad perhaps there is a cut in them or the shielding has broken but I don't believe that it is a ground wire problem. To get a arc like you describe it is a bad HT cable, tube or triode in my opinion the arc feeds back thru the grounds and destroys the other boards! This was a common problem with older Siemens Pandoros generators before high frequency came out-- I have seen this a 100 times
Good Luck
Kevin
imgsvcs@sbcglobal.net
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