In ball valve which one is more better Reduced port or Full port? (Open discussion) 1

[NDS_21]

Hey,
subject says the query!
This is what I know that full port are mostly used where pigging in pipeline is required while reduced port are used where negligible pressure drop is not of concern.
And also I have observed reduce port are less costly compared to same size of full port.
Is the pressure drop really negligible that it can be neglected?(It would be great if anyone can explain with a legit calculation)
THANKS IN ADVANCE.

 

[gerhardl]

Some general rules:
Reduced bore is often best/cheapest for smaller valves (one inch and less) with normal pressures and up to highest.
Reduced bore is often used as cheaper for larger valves where pigging is not necessary or pigs can pass, and pressure loss is low or insignificant. Increased use of reduced bore with higher pressure.

Very often general questions can not be answered very specific. More specific questions with limitations for size, fluid, pressure and application are easier to answer. Pro- and con for each specific construction will vary with all different details above. In addition to this will specific details and quality, as well as price, vary from valve to valve of the two constructions, else equal in size and pressure.

We engineers tend to forget that the real test of the best valve selection is the lowest total cost/lifetime : total cost including cost of operation, maintenance, repair, cost of stop and change / per unit of the systems lifetime.

 

[LittleInch]

For CV look at websites like this

https://www.engineeringtoolbox.com/ball-valves-flow-coefficients-d_223.html

What does that translate into in practice? depends on your flow and velocity.

I did a quick calc for 8" and for the same (highish)flow the pressure drop across a full bore was 0.005 bar, for same flow across a RB, 0.08 bar

Pretty negligible in the scheme of things, but if you've got a load of them in series then it can add up or if you've got a very low DP. You can also get pockets of liquid in a two phase system develop as the inlet into the valve is essentially a reducer.
The impact is bigger at lower sizes , 6" and below) as the reduction in area is greater.

In general on manifolds etc RB is standard, but piggable systems specify FB.

Look at your piping spec to see

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[DGrayPPD]

Some typical applications where you would need full bore over reduced bore:

1) PSV Inlet/Outlet
2) Pipelines requiring pigging
3) Sloped piping (for horizontal lines) to avoid low points
4) Piping in steam service (for horizontal lines) to avoid low points
5) Piping in slurry service (for horizontal lines) to avoid low points

In all other situations, reduced bore valves are used mostly as a cost savings in my experience. In most other situations, from what I have seen, there is not a significant concern over the pressure drop associated with reduced bore. If the pressure drop is that big of a concern, there may be more underlying issues with that line than just what type of valve port to use.

"Tell me and I forget. Teach me and I remember. Involve me and I learn."

- Benjamin Franklin

 

[georgeverghese]

To @DGrayPPD's list item (1), also add auto isolation valves in low temp depressuring service lines where hydrates could otherwise settle at RB ball valves.

 

[NDS_21]

@gerhardl @LittleInch @DGrayPPD @georgeverghese
Thanks for involving in discussion!
So like you guys said that certain applications only require full bore to be used while use of reduced bore can be considered as standard practice in market. Right?
And looking at the table of CV as @LittleInch specified, the difference in CV for a 3 inch ball valve the difference is 880. That's a lot I guess. So difference in CV doesn't have any relation with pressure drop?

 

[zdas04]

Pressure drop in a valve is a function of Reynolds Number. Gas has a very low density, so changes in velocity have a smaller effect on Reynolds Number (and therefore dP) for a given Cv than you wold see in a liquid. Big changes in Cv for a gas system rarely correspond to big changes in dP.

After a major fire in Southern New Mexico a few years ago all of the pipeline companies were required to smart-pig their mainline systems. Since (smart) pigging was never anticipated on these lines, the pipeline companies had to spend billions of dollars to replace their RP valves (you can run a maintenance pig through a RP valve, but smart pigs won't go). Keep this in mind while making a "Piggable or non-piggable?" decision. I use full port valves for any isolation in the body of a system. For valves on manifolds, around control equipment, etc, it is usually reasonable to use RP valves, but the cost savings are small enough that I don't risk having RP valves in a project inventory because you never know when someone will grab the wrong valve for a block valve in the body of the system.

[bold]David Simpson, PE[/bold]
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[LittleInch]

The CV value is quite different and it does have a direct relation with pressure drop, but what that pressure drop is is actually quite low.

Remember that the definition of CV for liquid is US GPM that results in a pressure drop of 1 psi.

The flows you need at that sort of CV are very high to have any sort of appreciable pressure drop.

I do agree with zdas04 though and if the difference in cost is marginal, just use FB valves everywhere. For a lot of these RB valves the difference is actually quite difficult to see in a hurry as the bores are often tapered down and normally something like a 8"x6" or 10"x8" RB. For flow if they get it wrong no problem, but try sending a pig along when it doesn't know it's there - big problem.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[bcd]

I have seen recommendations to only specify full port in several posts, which may not be good advice for your situation. Here are a few facts to help guide your decision. For an NPS 6 Class 150 flanged, carbon steel floating ball valve with PTFE seats:

Full bore weighs 240 lbs, reduced bore weighs 120 lbs (Full bore costs more to ship, and may increase your costs for pipe supports)

Torque to open full bore against full DP is 600 ft-lbs. Reduced bore is 250 ft-lbs. Large difference results because the ball is smaller in diameter on reduced bore. (Full bore can increase your cost to automate since a larger actuator may be needed)

Cv has already been discussed above. Big difference in the values, but in actual use, flow velocities in pipes are usually limited for noise and erosion considerations, so the net difference in pressure drop can be insignificant.

Bare stem valve cost: $1662 for full bore, and $1238 for reduced bore. $424 difference, which may not seem so much for a single valve, but if you are working is a large chemical plant using hundreds of them, it does make a difference.

Overall, more reduced bore valves are sold in all industries combined than full bore. Roughly 60/40 ratio. Industries such as oil & gas upstream pipelines mostly use full bore. Pulp and paper and mining where slurries are flowing through the valves, again full bore is mostly used. Chemical and Petrochemical, a very large industry for ball valves uses a high percentage of reduced bore.

My main point is to not generalize one versus the other. Both products have a need in the market place. Make your decision based on facts that affect your needs.

 

[NDS_21]

@zdas04 @LittleInch @bcd
So basically we can't conclude which one is better of the two options because each one has its own advantages based on its required application.
And pressure drop is not as much as I was wondering.
Last question would be if you are to manufacture ball valves, which valve market you would target first- Reduced bore or Full bore?
let's consider you want to go for 1" floating 3-piece ball valve with PTFE seats first in terms of design (That's what I was thinking to go for).

 

[LittleInch]

Floating 3 piece 1" - RB

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.