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Thread: Frick RWH-852E

  1. #1
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    Frick RWH-852E



    Hi All,
    In my LPG/NGL plant we have three above mentioned compressors and one of them seal is leaking, leak rate is very high even though vendor has replaced O ring but leak still persist. refrigerant is propane.
    Please explain following also,
    oil lose on low suction super heat, how?
    what is the optimum suction superheat for these compressors.
    Condenser LTs always fluctuating from zero to 100%, what operational changes to be done to stablized the levels.
    what level should be maintained in condenser and chillers to avoid carryover liquid in compressor suction.
    Thanks
    Toor



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    Re: Frick RWH-852E

    Quote Originally Posted by Toor View Post
    Hi All,
    In my LPG/NGL plant we have three above mentioned compressors and one of them seal is leaking, leak rate is very high even though vendor has replaced O ring but leak still persist. refrigerant is propane.
    Please explain following also,
    oil lose on low suction super heat, how?
    what is the optimum suction superheat for these compressors.
    Condenser LTs always fluctuating from zero to 100%, what operational changes to be done to stablized the levels.
    what level should be maintained in condenser and chillers to avoid carryover liquid in compressor suction.
    Thanks
    Toor
    It is simple ... low suction super-heat means you have very wet suction gases and you draw a lot of droplets and then probably your discharge temperature (discharge temperature should be at least 80C) is low and you loose oil...

    SSH depend on refrigerant and not on compressor ... not sure but for propane should be minimum 6K

    Both levels you would keep constant ... otherwise

    First you should come with compressor at working values both suction and discharge ... at some low capacity

    Level within chillers try to keep low and then by time try to increase as per required duty, but not over maximum working level ...

    For the moment try to increase condenser pressure i.e. condensing temperature ....

    All this is guessing, because, we do not know anything about your system design ... set points .. control logic ... duty ... etc ...

    Best regards, Josip

    It's impossible to make anything foolproof because fools are so ingenious...

    Don't ever underestimate the power of stupid people when they are in large groups.

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  3. #3
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    Re: Frick RWH-852E

    Hi Josip,
    Here is plant pfd, compressor discharge go to condenser and then propane receiver and from propane reciver to economize and Deethanizer condenser and water chiller.
    Economizer and water chiller pressure is , 4.2 barg , temp 10C and Deethanizer condenser pressure is 0.1 barg and temperature is -36 C.
    SSH some time is going to below 5C and discharge is varing from 30 to 40 C. Compressore discharge temp is 85 C.,
    I operated my economizer and chiller with very little valve opening and condenser inlet to 60% max out put, compressor suction pressure is 1.1 bara.
    Hence you have good exeprience, pllease explainer further on SSH and seal leak and condenser level problem.
    Toor

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    Re: Frick RWH-852E

    Quote Originally Posted by Toor View Post
    Hi Josip,
    Here is plant pfd, compressor discharge go to condenser and then propane receiver and from propane reciver to economize and Deethanizer condenser and water chiller.
    Economizer and water chiller pressure is , 4.2 barg , temp 10C and Deethanizer condenser pressure is 0.1 barg and temperature is -36 C.
    SSH some time is going to below 5C and discharge is varing from 30 to 40 C. Compressore discharge temp is 85 C.,
    I operated my economizer and chiller with very little valve opening and condenser inlet to 60% max out put, compressor suction pressure is 1.1 bara.
    Hence you have good exeprience, pllease explainer further on SSH and seal leak and condenser level problem.
    Toor
    Hi, Toor

    It will be much better if you can upload your PFD scheme with pressure and temp values ... you can make it by hand or you can use original and then put values by hand and make a scan...

    I am not a lawyer ... unfortunately, from above description I am not able to imagine your plant and working logic... hope to be able to help you, but need some more info.

    What is working envelope for your compressors, condensers, water chiller ... by the working instruction book?

    SSH seems quite low, but I do not understand which discharge is varying from 30-40C.

    Best regards, Josip

    It's impossible to make anything foolproof because fools are so ingenious...

    Don't ever underestimate the power of stupid people when they are in large groups.

    Please, don't teach me how to be stupid....
    No job is as important as to jeopardize the safety of you or those that you work with.

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    Re: Frick RWH-852E

    Hey,
    I think good to give more information, you use propane refrigeration process for what?
    Shaft seal-changed you ?, O-ring must understand that even carbon has an O-ring, you have also changed ?=5 pcs O ring, change the complete shaft seal and will be well. Propane is used FPM Viton O ring.
    Josef.

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    Re: Frick RWH-852E

    Toor,
    Above mentioned by Josip required for better results.
    If condensing pressure changes quickly it could foam oil in oil separator causing oil to be carried over.
    You would have to explain how condensing pressure is controlled & what type of condenser, example water cooled & what type of control valve contols discharge pressure.
    As for leaking shaft seal, can only suggest end float of rotor be checked, if OK , install complete new shaft seal, check coupling alignment.
    Suction superheat can be as low as 1 deg C on flooded evaporator, as far as correct level would need drawings or photo's at a minimum.
    To much Oil in system could cause some issues with level controls if not transferred back to compressor.
    If discharge temperature stays at 80 deg C at all times would not think liquid is returning to compressor, unless it happens at random.
    Coalesces in oil separator could also be a problem for oil carry over
    Level control on evaporator also required, type of valve & heat exchanger.

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    Re: Frick RWH-852E

    Ranger 1
    Deethanizer condenser pressure is controlled with PCV for non condenceable removal.
    IMG_3849[1].jpgIMG_3852[1].jpg
    Josip
    PFD is attached, Condenser, water chiller and economizer levels are big problem, this compressor have two stages, 2nd stage loaded after compressor capacity reaching to 75% (2nd stage pressure is from water chiller and economizer and 1st stage from condenseer).
    Thanks
    Toor

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    Re: Frick RWH-852E

    Toor lot's of questions,
    Is this a new system, or has it ran OK in the past?

    What type of level transmitter, are they calibrated, do you have a way of seeing level in a sight glass?
    What type of level control valves are used on liquid receiver, economizer, water chiller & DEC2, how are they controlled, on/off, modulating.
    If a fixed load the levels should be stable unless valves controlling levels hunting.
    Could not see de-ethanizer, how is it controlled & where are sensors for it located.
    In heat exchangers, only tube bundle should be just submerged in liquid for correct levels in DEC2, water chiller & economizer.
    Compressor loading to quickly can also cause level fluctuations.
    Last edited by RANGER1; 15-09-2016 at 10:53 AM.

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    Re: Frick RWH-852E

    RANGER 1
    Its a newly commissioned plant, level control valves are normal globe valve, level transmitter are emerson process, yes these are claibrated, level glas is there for reference lavel. propane boilng was witnessed.all liquid control valve are on manual mode because of level hunting.
    Thanks
    Toor

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    Re: Frick RWH-852E

    Hi, Toor

    Quote Originally Posted by Toor View Post
    Ranger 1
    Deethanizer condenser pressure is controlled with PCV for non condenceable removal.
    IMG_3849[1].jpgIMG_3852[1].jpg
    Josip
    PFD is attached, Condenser, water chiller and economizer levels are big problem, this compressor have two stages, 2nd stage loaded after compressor capacity reaching to 75% (2nd stage pressure is from water chiller and economizer and 1st stage from condenseer).
    Thanks
    Toor
    Sorry for late reply, but actually I was very busy with almost the same problem on another plant ...

    This type of design we call single stage with economizer, but it is very close to double stage system and now the name is irrelevant - it will be much easier for you to run two stage system ...

    I will try to give you some suggestion ... but explanation is not simple for me ... we are not using our mother tongue and sometimes some important info can be lost in translation ... but let's try ...

    1. you must have enough refrigerant (propane R290) within your system

    2. try to get you compressor into working envelope (evaporating pressure within your deethanizer condenser (for refrigeration people that is another evaporator or HE) at 0,1 bar/-36*C and your propane condenser at 17 bar/52,2*C) with smaller capacity i.e. try to keep low load within your water chiller ... here is important to keep propane level, but reduce only water flow until you come to required outlet water temperature ... if you have a lot of warm water entering into your water chiller all propane will evaporate and you loose level ... then when your outlet water temperature is Ok you can increase water flow

    3. the same should be with your economizer (seems it is shell&coil as per your drawing) and your level drops every time when LCV for deethanizer condenser opens because into economizer coil enter a lot of hot liquid propane from propane receiver ... try to achieve steady conditions in deethanizer condenser ... if you reduce load within water chiller, probably your economizer will work fine and you'll have enough liquid propane to feed your condenser...

    4. until your compressor not come above 75% capacity both suction ports (first stage and second stage are connected (this is due to mechanical design of compressor and cannot be changed) and within both of them compressor suction pressure is equal ... at compressor capacity higher then 75% second stage port is divided from suction port by slide valve ... now we have two stage system ...

    ... the most important is to change only one value at time and then wait for feedback ... if you change more values (level, pressure, flow) in the same time probably you'll lost control ...

    I know, it is very hard to work with process, because that is very important and operators are thinking only about that (now I have the same situation here on this plant) ... they assume you can follow them whichever changes occur .... unfortunately that is not true ... you have a tool which is designed to work under certain conditions with small fluctuation which can be followed by integrated control logic .. any huge change within utility will affect refrigeration plant ... and we have something we call domino effect ... i.e. system trip ... then we are again at beginning ... starting with small load

    hope this will be of some help to you ... if you need some more explanation please do not hesitate to ask ...


    Best regards, Josip

    It's impossible to make anything foolproof because fools are so ingenious...

    Don't ever underestimate the power of stupid people when they are in large groups.

    Please, don't teach me how to be stupid....
    No job is as important as to jeopardize the safety of you or those that you work with.

  11. #11
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    Re: Frick RWH-852E

    Hi Josip,
    Thanks for your reply and yesterday i was worried about your reply, anyhow, we are operating compressor as you said and now our system is very stable.
    Surely if new problem raised then come on this forum.
    Cheers
    Toor

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    Re: Frick RWH-852E

    Hi, Toor

    Quote Originally Posted by Toor View Post
    Hi Josip,
    Thanks for your reply and yesterday i was worried about your reply, anyhow, we are operating compressor as you said and now our system is very stable.
    Surely if new problem raised then come on this forum.
    Cheers
    Toor

    I am really happy if you succeed to run your plant without problems ...

    Of course, you are welcome anytime to come here with your problem ...

    ... here are many nice people willing to help,

    and for that reason this forum is one very nice community ....


    Best regards, Josip

    It's impossible to make anything foolproof because fools are so ingenious...

    Don't ever underestimate the power of stupid people when they are in large groups.

    Please, don't teach me how to be stupid....
    No job is as important as to jeopardize the safety of you or those that you work with.

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