Steam Turbine on Load Valve Stroking

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vikneswaran Member Join Date: Jun 2013 Posts: 5	Steam Turbine on Load Valve Stroking 06/09/2013 9:40 AM
	We operating Parson steam turbine with capacity of 105MW. This steam turbine consist of HP turbine and LP turbine only. Superheater steam flow to HP turbine control by 1Emergency Stop Valve, and 2 Governor Control Valve. Recently we having problem with emergency stop valve, can't close during shut down. The valve only able to close after 6 to 8hrs. One of posible root cause we suspected was, not doing on load valve stroking. As in OEM manual, emergency valve should stroke close 50% daily during operation. Can anyone share experiances on onload valve stroking for steam turbine with 1 Emergency stop valve....
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RAMConsult Guru Join Date: May 2007 Location: NYC metropolitan area. Posts: 3230 Good Answers: 444	#1 Re: Steam turbine On load Valve stroking 06/09/2013 2:23 PM
	Why are you questioning the OEM manual? What do you want us to do, tell you that it's ok to ignore the OEM? If it clearly states that you should do a 50% stroke on a daily basis then there is a reason for it. As you have observed by not following their instructions, the valve gets stuck and does not operate. Be thankful that there hasn't been an incident that required that the valve operate and perform its function as an EMERGENCY Stop Valve. Now find the person(s) who decided not to follow the OEM's procedures and remind him of who will be liable when the turbine overspeeds (and possibly self-destructs) on a full load rejection trip because the ESV didn't stop the steam flow immediately. And do take the unit offline immediately until the SAFETY valve is fixed, the life you save may be your own. __________________ “Tell me and I forget. Teach me and I remember. Involve me and I learn.” Ben Franklin.
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IRSHAD Power-User Join Date: Nov 2008 Posts: 121 Good Answers: 4	#2 Re: Steam Turbine on Load Valve Stroking 06/09/2013 11:59 PM
	There are partial reciprocation devices for checking the functioning of stop valves during steady running. A pulse given to the reciprocating mechanism, will cause thew valve to move 10 to 20% of the stroke and giving another pulse will return the valve to fully open condition. The operation can be carried out both from control room as well as in the field and hardly takes 2 to 3 minutes. During steady running the stop valves remain fully open and due to sludge or varnishes in oil gathering between he piston and the cylinder of the operating hydraulic mechanism, the valve may get stuck up when required to close. Following OEM practice is a must to avoid such cases.
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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 32175 Good Answers: 839	#3 Re: Steam Turbine on Load Valve Stroking 06/10/2013 3:53 AM
	Is there any particular reason why the local Parsons representative hasn't been called in to investigate and remedy the fault? Is there any particular reason why emergency shutdown systems are not being properly tested and maintained? Are there any other emergency systems at the facility that are not being properly tested and maintained? Do advise so that CR4 readers can stay away for their own safety. __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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vikneswaran Member Join Date: Jun 2013 Posts: 5	#4 In reply to #3 Re: Steam Turbine on Load Valve Stroking 06/11/2013 9:21 AM
	Thank you guys... As our previous record, there was few attemp onload stroke test, but failed. Now already contected Uk Parson to assit us to do test during this June Minor Inspection. Hopes we can rectify. TQ
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