On-Line Ball Valve

[jaffaotc]

Experts,
Is the Ball valves get jammed in service becasue os some foreign particles between seat and ball, how we can overcome to this issue, is there any method to do in service (on-line)?

regards

Jaff

 

[zdas04]

It depends on the manufacturer. All but the least expensive flanged valves have grease-injection ports that can be used to pump a sealant into the seats that can flush away debris. Another reason to purchase specific valves instead of letting your parts house sell you junk.

David

 

[jaffaotc]

Thanks zdas04,

Actually if any grease injection port will be not there, what will be the next step? and if grease port is there then, which type of sealent is suitable?

Jaff

 

[gerhardl]

Hi, jaffotc!

the answer is highly dependent on all relevant details:
type of ball-valve and operator, size, pressure class, all details on fluid and operating conditions and type of particles and how and where they are stuck.

Sealant could help in some cases and if requirement to thightness is not too high.

If not successfull: flushing with fluid while operating, or if possible blow-through with gas or air?

If seats or ball are scraped or damaged, and particles stuck or burnt on to seats or ball: no inline repair is possible (unless small 3- piece BV with mid section part demountable in line, to be changed for seats, ball or complete).

If recurrent or repetitive to high cost or trouble: check to optimize process or look for more suitable valvetype.

 

[jaffaotc]

Thanks Gerhald,

Actaully, there are so many Ball Valve of size range 4" to 12" with the line pressure around 80 bar, fluid density is also high you can say crude, type of stuck you can say we tried by applying more torque but no movement, if we will go more than that i hope that gear box shaft will twist, actually my question is:
1. If its possible by grease injection point, then which gas is suitable to inject which can solve our problem.
2. If the grease injection point is not there, what will be the next step? then we have to take a shutdown which will be a loss in production.

Jaff

 

[zdas04]

Find a company in your area that maintains valves and get their recommendation for a choice of sealant/grease. Local companies have dealt with local problems and have found solutions (or they would not still be in business).

If there are no injection ports then you've puchased a "disposable valve" that the only option is to dispose of it.

David

 

[tr1ntx]

jaffaotc,

I've never seen a ball valve being jammed by foreign particles in the seat. I don't mean to say that it can't happen. All the cases I've seen are of the seat and/or ball being scraped/gouged by foreign particles. The mechanism to turn the valve provides enough torque to force the particles into and through the seat material, or the ball surface in the case of metal-seats.

I have seen trunnion-type ball valves jammed by foreign particles in the bottom trunnion bearing. They get in between the trunnion stem's surface and the bearing face and just jam in there, gouging up the trunnion stem until there is just so much stuff packed in there that it locks up. I've seen gear operators break gear teeth, valve stems twist off, actuator seals blown, etc.

It might be possible to flush the lower trunnion bearing if there is any sort of bleed port or grease fitting. That might free it up and allow you to operate the valve again. The valves I have seen that have been jammed by the foreign particles have been damaged so badly that the ball needed to be replaced. I mean, that is if you wanted a properly operating valve. The valve would still function, but the trunnions stems were so badly damaged that they were in a condition to tear completely through the bearings in a short amount of cycles and require much more torque to turn. I don't know what that "short amount of cycles" would be . . . 20, 50, 100. I said "might be possible to flush" it out, the ones I've seen had the particles so firmly jammed in that likely wouldn't have been possible.

 

[gerhardl]

.. I agree with all above, especially tr1ntx thourogh answer.

I am afraid that this is a case where not particles but crude oil combined with particles acts as glue on ball, seatsealings and stem sealings, and also in addition have scraped seats etc.

It coild be that the grade of crudeoil could vary, and at surrounding or pipeline temperature could give high viscosity or go to soilid state (asfalt) in some exposed valveparts, especially if valves and pipeline are left exposed to surrounding temp. without proper cleaning.

To overcome your instant problem you could try to heat locally (without causing a fire, use water or steam) and within acceptable limits for seats.

longtime prevention: isolating of pipeline and valves, steam or other firesafe heat-tracing, cleaning between batches, ballvalves with carbon reinforced PTFE if compatible with fluid to be a bit more acceptable with gliding properties at higher temperatures without deforming.

... but I am afraid you have to go to a planned closedown in two steps: one to determine cause and change troublesome valves, and next to change to a more permanent solution.

 

[jaffaotc]

Thanks tr1xnt,

what gerhardl was saying is correct this is because of the crude.

i hope, this method will work, applying an pressure through grease port.

thanks to all,

jaff