Connection of 40mm pipe with 20mm valve

This depends on a few things. If full (or nearly full) line flow must be maintained through the various instruments (e.g., flowmeter), then you should not reduce the line size. On the other hand, if your instruments are "dead ends" branched off the main line (e.g., pressure gauges), then smaller valves are probably okay. A drawing or sketch, together with flow rates, would help in deciding this.

A. At downstream of your ball valve, you will have considerable pressure loss due to flow abrupt restriction (40mmΦ pipe to 20mm Φvalve)

Is this in someway connected to a storage tank? What is that level instrument doing in the line?

Flow instruments is most preferably located some length = MxΦ of pipe just to ensure the flow is laminar, but for a pressure transmitter, its not a big concern.

B. If its not a delicate process where you can have a tolerable loss of pressure and wont damage quality of products. Why not introduce a reducer 40x20mm reducer Its best next option to consider. But do take measure to equate the amount of pressure losses(energy loss)/time(money) vs. cost of 40mm ball valve (frequency of replacement)/time(money)--> this will make your decision justified.

Yes, the instruments are just located on the side of pre-heater to measure level and pressure and i think no flowmeter is connected. Line is directly connected to PT through ball valve.

I think 40x20mm reducer will not have any significant effect, especially, I presumed that this is a low velocity line.

Assuming this line to be a branch connection (almost definitely since the measurements gauges/transmitters are pressure and level ) there will be absolutely no effect on the readings by the size reduction. Since the instruments form a dead end to this branch.

In most of the lubrication systems you may observe that the tapping points will be of the order of 1/2" (and that is maximum), the 3/8", 1/4" impulse lines are much more common. In these the sockolets will be welded on the pipe at 90 degrees and from there the tubes will be led upto the instruments.

In your case since the branching is already done inside, the best way is to reduce it through reducer as suggested above and then route it to the instruments through 20mm tube.

yah, fight like a man. would you? It's not about pride. its about learning. you know That would have been fun if you show who you are.

Thanks very much guys. We will put a reducer and 20mm valve instead of one 40mm ball valve. As we also have to consider the available spacing, is it possible for me to use Butt welded or screwed ball valve (20mm) instead of flanged? I think length of flanged valve in more as compared to welded so I assume I can simply weld it directly with the reducer. Please let me know if you see any problem with that.

Thanks

Sam, below 50mmΦ valves is usually made in screw connections although DIN has available flange 50mmΦ, above 50mmΦ is usually in flange connection.

Yes, but we are dealing with high pressure and high temperature slurry so it might be an issue. I am just considering welded end connection due to space shortage

In my service (industrial refrigeration) there are lots of weld-end globe, Y-pattern, and angle valves. Ball valves are less common; with threaded, brazed-socket copper, or socket-weld ends; but no butt-weld ends that I've seen so far. I don't recall if you have mentioned your service yet, but if weld-end valves are offered, they would be a good, compact choice. You did say slurry, so your pipe size reducers should be of a smooth internal contour such as butt-weld reducers rather than bushings.

Welding might burn the valve seat

Please check valve seat used for the service, maximum temperature from that link is only up to 500 deg C

The media never came out in discussion till now.

May we know the media and the Temperature/ Pressure?

Using NB20 instead of NB50 will change everything in case the viscosity is too high.

Yes, our media is slurry with 25% solid contents, not sure about temp and pressure but I assume its pretty more than ambient.

Can you please tell me how Viscosity could be an issue? Our pressure is around 35 bar, temperature 200C and slurry is quite viscous.

When you are handling highly viscous fluid, the reducesr will act like orifices and there will be quite high pressure drop across it, espacially since this is being used as level monitor too and thus is not exactly blind connection (in which theoritically the pressure remains uniform in incompresssible fluid). In case of level measurement, you will need a loop connection/ end opened to atmosphere. Though in your case, at 35 bar system pressure you are more likely to loop back rather than having opened to atmosphere.

In addition the highly abrasive fluid will make the piping and valve prone to abrasive erosion even at the normal fluid movement and that will be dependant on the velocity. Making the diameter half will increase the velocity to 4 times in normal piping and may be just a bit more in valve.

Yes, we loop back the entire connection to the bottom of preheater. It seems like we have to review the recommendation again based on the possibility of pressure drop and increased velocity which may cause abrasion to the smaller valve.

You can bet that the original maker of the setup used the smallest ( and Cheapest ) ball valve that they could get away with.

Without knowing all of the factors involved it would be dangerous for me to say "yeah mate, stick in a 20mm ball valve. She'll be right!"

Especially if there could be a person nearby when it it blows.

This whole thread continues be confused, because we do not yet have a valid description or P&ID sketch from the OP. The line in question apparently contains a slurry of some sort, but a slurry of what? We don't know yet if this is a flow-through line, or basically a dead end. We don't know whether we are measuring flow, temperature, liquid level, pressure, composition samples, or whatever else. Is the line vertical, horizontal, sloped, or some combination of these? We still have responders recommending abrupt reducers in a slurry line, which is probably wrong. We don't know what parts of the piping may contain liquid versus slurry versus vapor, and we don't know any flow rates or velocities. This is supposedly an engineering forum, and it should be furnished proper engineering information rather than vague guesswork.

OP, please step up to the plate and describe in correct detail what is supposed to be going on here. As yet, there is no way to tell whether the responses are good, bad, irrelevant, or just plain stupid.

Sorry for not providing detailed info, actually, its laterite ore slurry, 25% solid contents, and temp and pressure almost 220C and 35 bar resp. Only Level Transmitters are connected to the branches and then the tube loop back in the equipment. Anway, I am pretty much cleared and ready to discuss the issue with my boss tomorrow and finally he's gonna decide to go ahead with this plan or not.

I'm sorry, but that did not clear up matters very well. The sentence "Only Level Transmitters are connected to the branches and then the tube loop back in the equipment" is a very inadequate description. You can thank your lucky stars that I am not your boss.

Right, actually there are other instruments but we are only dealing with the brach with Level Instruments and FIC and then it this line goes back.

I just stared my career so you can assume I'm not much aware of the complex terms. I am employed as Graduate Mechanical Engineer

I'm sorry again, but this "description" is not understandable in its present form. "And then it this line goes back"?? Up, over, down, across, back where? And what is "FIC"?

Once again, a P&ID (piping and instrumentation drawing) would be desirable, showing orientation, dimensions, pipe and valve sizes, liquid/vapor state of fluid, etc.

Please bear with me. You might not like these questions at the moment, but if you are serious, then sooner or later you will be glad that someone asked these questions.

The lines comes out, where Ball Valve is connected and then goes down along with the Equipment and connected to the bottom of preheater. On this line, a Level transmittor and Flow instrument control are also connected. So the line originating from the middle of preheater, 90 deg turn, goes down and then again a turn and connected to the bottom.

As a Mech Engineer, I just started reviewing PID so not very well aware of it.

Anyway, I am very much thankful to all of you guys to bear with me, at this stage, I think this info is sufficient and my boss may not expect more than that from a fresh engineer :)

From this description, I would conclude that your boss (and/or the system designer) is even more naive than you are. This is most unfortunate, because it looks a lot like the blind leading the blind, with everybody falling into a pit. (There is a medieval Pieter Breughel painting depicting this situation quite poignantly.)

So the last word is now - not recommended ?

On this line, a Level transmittor and Flow instrument control are also connected.

From beginning we have been insisting on no flow and the OP was confirming there is no flow measurement on this line?

Even as a fresh engineer, one should first do the homework before asking clarification here where one would only guess and not know about the actual system. And the modification will only make the equipment collapse.

Dear Mr. SAM12,

1. What is the cost Implication for 40 and 20 mm Valves.

2. Pl. provide a sketch, that will give better idea to understand. If flow is a parameter, then pressure drop will have an impact on the measurement.

"As maintenance of 40mm valve is quite expensive in our case..." First of all I do not agree with your above statement. How and how much expensive is the maintenance? I do not suggest introducing a lower size valve unnecessarily.

Also, please see the contradicting information you have posted at 18 & 19:

"...Yes, our media is slurry with 25% solid contents, not sure about temp and pressure but I assume its pretty more than ambient."

"Our pressure is around 35 bar, temperature 200C and slurry is quite viscous..."

If slurry is quite viscous, reducing valve size may be more desosterous.

Thanks again all of you,

It was first assignment I ever got and the only thing I learned, grab all required information and then furnish any question. I considerd it a very simple problem but as you guys raised question and i explored it in further depth, I found it more and more complex. Anyway, this job wasn't a priority and my boss has assigned me something else so thanks again and no need to add anything anymore.