Jump to content



Featured Articles

Check out the latest featured articles.

File Library

Check out the latest downloads available in the File Library.

New Article

Product Viscosity vs. Shear

Featured File

Vertical Tank Selection

New Blog Entry

Low Flow in Pipes- posted in Ankur's blog

Rov On Mixed Butane Line


This topic has been archived. This means that you cannot reply to this topic.
9 replies to this topic
Share this topic:
| More

#1 rajprocess

rajprocess

    Veteran Member

  • Members
  • 34 posts

Posted 24 March 2015 - 01:12 PM

Dear Forum Members,

 

Mixed butane is the feed stock for our plant. the mixed butane line entering our petrochemical complex runs 2km inside the complex and enters our battery limit. we are the only consumers of mixed butane in our complex. the mixed butane is supplied by one of the largest refinery and it supplies to all the petrochemical plants in the corridor. 

 

Piping:

 

Just after entering the fence there is a ROV ( operation from control room) on mixed butane line, followed by metering skid.

After metering skid the line stretches 2km before entering the plant battery limit.

after entering battery limit the line enters the mixed butane sphere, sphere is provided with sil3 protection for highlevel and pressure.

i am attaching rough schematic for better understanding.

 

Attached File  Complex fencePlant battery limit.docx   22.55KB   13 downloads

 

 

Question:

 

In earlier design there is rov followed by metering skid.

but since 15 years the rov and metering skid are bypassed by providing bypass line ( the reason for bypassing and documents are not available).

while doing the phar study we came across this issue.

 

1. What is the importance of this ROV.

2. Is there any standard for providing rov at fence on butane lines.

 

Appreciate your support and guidance on above queries.



#2 Zauberberg

Zauberberg

    Gold Member

  • ChE Plus Subscriber
  • 2,727 posts

Posted 24 March 2015 - 01:31 PM

This ROV seems to be a simple HIC (HCV) used to regulate inflow to the Butane sphere, in the earlier days. Perhaps there was no SIS at that time so this ROV played the role of control and isolation (battery limit) valve at the same time.

 

You say there are corresponding actions from the SIS in case of high level and high pressure in the sphere, but this is not shown on the sketch. Is there an inlet SDV which closes at high-high level in the sphere?

 

Valves are commonly located at battery limits between plants or between different business entities. Whether they are ROV/HIC, manually operated valves, or SDV's, it is up to the designer (who has apparently taken all relevant facts into account).



#3 rajprocess

rajprocess

    Veteran Member

  • Members
  • 34 posts

Posted 24 March 2015 - 02:14 PM

it is only rov at the fence, SDV's are provided at inlet of the sphere with sil 3 configuration( not shown in the schematic). 

the rov is provided with the back up instrument air vessel so as to operate even in case of instrument air failure, which implies the provision of rov has a significant role.

as rov is bypassed since 15 years there was debate and ambiguity going on in our team.

 

options:

 

to keep it bypassed.

to take back in line.

 

we are unable to make a decision as we dont have enough background and looking forward for support and guidance.

 

it is good to say keep it bypassed, but we may living with risk and will live with risk.

and again it is good to say keep in line, but it requires some capital and time , as the old rov is not maintained since years and cannot be used.

 

thanks and regards,

 



#4 Zauberberg

Zauberberg

    Gold Member

  • ChE Plus Subscriber
  • 2,727 posts

Posted 24 March 2015 - 02:17 PM

How do you control flow to the sphere now? Is it controlled at all from your DCS?



#5 rajprocess

rajprocess

    Veteran Member

  • Members
  • 34 posts

Posted 25 March 2015 - 12:02 AM

Level to the sphere is controlled from control room , there is level control valve on inlet of sphere (sil 3 protection for high level resulting in overpressure)



#6 Zauberberg

Zauberberg

    Gold Member

  • ChE Plus Subscriber
  • 2,727 posts

Posted 25 March 2015 - 03:04 AM

It seems like we are having a small confusion here. The same valve is not normally used for control and for safety function. The first one is a modulating valve, the second one is on-off valve. The first one is a part of DCS, the second one is a part of SIS.

 

Are you saying that there is a dedicated level control valve at the inlet of the sphere, and another shutdown valve? Please confirm.

 

For getting a proper response, you need to submit all relevant details of the problem. Otherwise we can only guess and perhaps even misguide you.



#7 rajprocess

rajprocess

    Veteran Member

  • Members
  • 34 posts

Posted 25 March 2015 - 03:18 AM

Your assumption and the understanding of the schematice is exactly what we have.

we have Control valve and a on/off valve



#8 Zauberberg

Zauberberg

    Gold Member

  • ChE Plus Subscriber
  • 2,727 posts

Posted 25 March 2015 - 03:49 AM   Best Answer

Thank you. I will continue with assumptions further, so I would imagine the ROV with manual isolation valves (gate or ball) upstream and downstream of the ROV. And a bypass line around the ROV, containing a modulating (globe) valve with a similar Cv to that of the ROV. Is this the exact arrangement?

 

The necessity of a battery limit valve is indisputable, at least for two reasons:

 

1) Maintenance of the line, from the fence to the sphere inlet shutdown valve (SIS valve). There is no way you can isolate this line from the remaining (and apparently complex piping network upstream) if there is no valve at the fence/battery limit. If there is a need to repair a segment of this line, it would be impossible to perform adequate isolation from the network, on the side of your facility. As a matter of fact, you would have to have provision for positive isolation of the line which means Double Block & Bleed, or Block & Bleed with a spacer/spade.

 

2) Emergency case (e.g. line rupture). Even if there is a dedicated SDV close to the sphere, rupture of the Butane line between the fence and the SDV would result in uncontrolled loss of containment with possible catastrophic consequences. Without a battery limit valve, there would be no means to stop leaking of Butane from the piping network upstream into facility area. That is extremely hazardous. for this scenario I would consider SDV exactly at the battery limit, not close to the Butane sphere. I hope there is a Fire & Gas Detection system at your facility and linked to SIS.

 

As you can see, the valve is very much needed at the battery limit. For maintenance reasons, it would be sufficient to have manually (locally) operated valve(s). For emergency situations, an SDV would be a proper choice - you don't want to rely only on human/operator reaction of closing the ROV in order to prevent from uncontrolled leakage of Butane. Manual valve is the worst option because an operator has to actually go there himself and manually close the valve. So the current way of operation via bypass is potentially very harmful in case of piping leak or rupture. The ROV is a slightly better option, but it is the SIS valve which should be standing there.



#9 rajprocess

rajprocess

    Veteran Member

  • Members
  • 34 posts

Posted 25 March 2015 - 02:25 PM

Thank You Dejan for your valuable feed back..

Team has decided to take ZV101 in line.

Appreciate your support.



#10 Zauberberg

Zauberberg

    Gold Member

  • ChE Plus Subscriber
  • 2,727 posts

Posted 25 March 2015 - 05:46 PM

You are welcome. Please also investigate if you have provisions for adequate isolation during maintenance. A single valve would probably not be enough, considering that fluid in question is Butane.

 

Also re-run the rupture scenario and confirm if the ROV can be considered as sufficient protection. I would tend to disagree with that.






Similar Topics