Hi

Today in our site we adjust the accumulator pressure to 52bar. (GE frame 5).

as I know hydraulic pressure is almost 90bar and 63HQ act in almost 75bar so how 52bar pressure of accumulator in hydraulic oil path can compensate transient fluctuations in circuit?

 

dontknowman,

I typed this into my preferred Internet search engine (with double quotations):

"how to calculate hydraulic accumulator charging"

This was near the top of the results:

http://engineersedge.com/hydraulic/accumulator_equations.htm

Think of it this way--if the pressure in the accumulator is the same as or higher than hydraulic system pressure, then no hydraulic fluid will enter the accumulator, and the accumulator will not be able to maintain pressure when the flow is higher than the pump can accommodate.

The accumulator has a couple of purposes--to minimize pressure pulsations (by "absorbing" spikes and "supplying" dips with oil from the accumulator vessel), and to maintain system pressure when flow temporarily exceeds pump flow-rate capability and causes system pressure to decrease (by forcing hydraulic oil out of the pressure vessel into the hydraulic system).

So, the pressure in the bladder of the accumulator must be less than system pressure in order for some oil to flow into the accumulator pressure vessel. The pressure inside the bladder will increase to equal system pressure and at the point there will be no hydraulic oil flowing into the accumulator. As soon as pressure in the system drops below accumulator pressure oil will flow out and it will flow back in when system pressure increases.

The hydraulic oil port of the accumulator also acts as a small orifice to limit flow to a small extent to try to prevent making any pressure fluctuations even worse.

So, the bladder is charged (usually with nitrogen) to about half of rated system pressure--to inflate the bladder and to allow the bladder to compress as hydraulic oil at system pressure enters the accumulator and when the hydraulic oil system pressure and the bladder pressure are equal then there is no flow into or out of the accumulator and everything is in balance.

The hydraulic system of GE-design heavy duty gas turbines are actually pretty "static" systems with very little or no flow when the turbine is running at a steady operating point.

When the turbine is operating at a steady-state condition, all of the hydraulic actuators are being held in a stable position--meaning there is no hydraulic flow into or out of the device actuators. Only when load changes or during starting or shutdown when valves and IGVs are moving is there any flow of hydraulic oil into or out of the hydraulic actuators of devices--at all other times the hydraulic pump is just maintaining hydraulic pressure with little to no flow until some device is commanded to move which requires flow.

Typically, the largest actuator (the one that requires the most flow to make large position changes) is the IGV actuator. So, it's the IGV actuator making large movements that typically requires the most hydraulic oil and causes the biggest dips in hydraulic system pressure under normal operating conditions.

Hope this helps!

 

>Hope this helps!<

surely that helped me CSA! Honestly I was waiting for your replay!

Now CSA I have a question:
I've worked some years on GE gas turbines and almost entire of my experience is in field. I know instrument, their GE code, test and callibration of them P&ID diagram and...

Now I'm searching hard for a comprehensive and classic source for training speedtronic(specially Mark5). But I couldn't find anything useful and There is not any valid training course in my country.

Can U show me or introduce me some reliable and useful resources?
I'm too eager for such thing to study and work on. I wish U can.

best regards

 

1) Do you have a copy of the MKV manuals.

2) I can send you a copy of Fundamentals of MKV, a good document to start learning.

Drop me an Email to [email protected]

 

dontknowman,

I'm glad to have been of help--and thanks for the feedback!

Now, about your question regarding Mark-specific training (Mark V, in your case). There are very few companies--and individuals--which offer Mark-specific training in various parts of the world--but I'm not aware of any that offer much in the way of on-line or "correspondence" training (as it would have been called before the World Wide Web).

I, however, have a question--not just for you but for anyone reading this thread and interested in the same kind of Mark-specific training offered on-line. How much would you be willing to pay for this training? How much would this training affect your ability to improve your employment status and increase your income level--not just immediately, but over time--say, 10-20 years (presuming you're going to remain working that long)?

Or, would you prefer to purchase a manual with an ability to ask questions or clarify information in the manual via a Web-based site (limited, but could be expanded on an hourly or incident basis) from knowledgeable and experienced technicians? How much would you--and anyone reading this thread--be willing to pay for such a manual and Web-based support? Let's say this Web-site had access to videos and supplementary documentation for enhanced learning?

Would you be willing to participate in a moderated Web-site to help answer and clarify questions and upload photographs and operating data to support enhanced learning and problem resolution--in exchange for credits which could be used to access more technical support and enhanced learning and improved manuals and documentation? Let's say there was a list of photographs and operating data with "credits" which would be "paid" for the information (after review and analysis for suitability and clarity and completeness)--to be used for buying enhanced learning and improved manuals and documentation and videos?

Let's say you--and anyone reading this thread interested in the same kind of training and manuals and technical support--were keenly interested in purchasing this training and/or manuals. How would you be able to pay--credit card, money order, electronic funds transfer, debit card, or ???

There is a HUGE opportunity here for people to obtain training and knowledge, but preparing the materials and setting up- and maintaining the Web-site costs time and money. Many people think that useful and informative Mark-specific training materials exist--and have been uploaded to the World Wide Web, and I've seen a lot of it (most of it illegally uploaded). And, mostly it's just the generic information that consists of the OEM manuals (which aren't all that great--especially without being able to physically work on the equipment) and some outlines and a few site-specific paragraphs. These might be useful to a few people, but they're not going to provide the level of detail required for anyone to be able to say to an interviewer, "I've studied Mark "X", taken examinations to demonstrate my understanding and knowledge of the equipment and how it works and how to maintain it and troubleshoot it." The level of detail and information required for this kind of statement to be true just isn't available out there anywhere on the World Wide Web--and in very few "classroom" situations, either.

So, your thoughts and ideas and answers would help greatly--this is something that is widely desired and needed. The scale of desire is such that the cost could be relatively "inexpensive" (I understand that is a relative thing in many parts of the world). This is something I've been working on for a while, but there are many hurdles (payments from individuals is one I've encountered--and I'm looking for ideas and suggestions and methods)--the biggest one being copyright protection. People who produce useful and informative documents for others need to make a living, too, while the fruits of their labours are helping others to improve their income ability. There is a LOT of information which could be developed--but the threat of it being illegally uploaded and accessed for free prevents for-profit Companies from making the investment. Or even for-profit individuals, for that matter.

Here are a couple companies you might investigate. The first is an advertiser here on control.com--someone who makes this forum possible: Gas Turbine Controls Corporation (www.gasturbinecontrols.com).

Another is HPC Technical Services (www.hpcnet.com). And, of course, there's always the OEM--though I wouldn't know where to start looking for their training offerings these days. There is great upheaval in the Company, what with the acquisition of Alstom and the move of the Corporate turbine training facility from upstate New York, USA, to Houston, TX, USA. And, I don't know what they're doing--if anything--these days with on-line training (they were testing some on-line courses with mixed to poor results a few years back).

Looking forward to hearing from you--and anyone interested in the same/similar training and information.

 

CSA

I should say that's a very good idea to make a website for supporting and training in gas turbine (or wider control field) which is not free.

But as U know better it has too many problems:the biggest one copyright protection.I dont have any suggestion for this because I think most users of such content like me are asian or third world countries and honestly in these countries there is no internalized value for regarding copyright.

Another point is that salaries in such countries is not comparable to developed countries(for the same work and specialty). So for me,myself I am ready to pay for such thing(in condition of suitability,clarity and completeness) but that is not clear for me to how it should be?for example membershib fee??or....

Another problem for me is how to pay it?

 

A lot depends on what you are trying to do but for keeping the pressure as constant as possible for motion then you want to pre-charge the accumulator to about 80 to 90% of system pressure.
You want the gas volume in the accumulator to be as large as possible but you don't ever want the accumulator to run out of oil.

http://hydraulicspneumatics.com/200...icle/False/43954/TechZone-Accumulators?page=2

Accumulators are essential for good hydraulic motion control because they will supply oil immediately whereas pressure compensated pumps only start to supply oil as the pressure drops which is what you don't want.