Pressure pump selection. 3

[Leonardop318]

Hi everyone,

I'm working on a project where a have to design a closed-loop calibration rig that has to work like this:
1. Circulate (1-2m3/h) a fluid at 20°C and 10 bar.
2. Take the readings from the meters.
3. Raise pressure to 30bar, take readings, and then to 50 and 80 bar
4. Raise temperature to 60°C and start again from 10 to 80 bar.

I asked in a previous post and I was told I could use a gear pump to make flow the fluid, and an additional small pump to add/extract fluid in order to increase or decrease pressure.
Do you guys know what kind of pump would do the job?
What else would I need to consider to make it work?
Do you have any additional suggestion?

Thanks in advance.

 

[itsmoked]

Hydraulic oil or something else?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[hydtools]

Would a simple plunger work to change system pressure? Use it to decrease or increase system volume with corresponding pressure increase or decrease.

Ted

 

[LittleInch]

For what I'm guessing is a fairly small volume, a pump or even a hand piston pump is not really what you want and your pressure will be difficult to maintain. Even 2-3 C variation means 10 bar variation on a truly closed system.

If you really want to go that way look into a hand pressurizing pump used for hydrotesting which should be good for 80 bar.

Something like this:

https://uk.rs-online.com/web/p/prod...VREPTCh3UXAXhEAQYAiABEgJLCvD_BwE&gclsrc=aw.ds

As in the other post, I would recommend you use a cylinder off the system about 50/50 air / gas of around 5% of your system volume and then just vary the gas pressure via say a 220bar nitrogen bottle with a pressure regulator.

This will allow you vary pressure up and down ( just vent it) but will also act as a buffer for any temperature variations and pressure fluctuation.

how are you going to heat up and cool down this loop? - You need an inline HX I suggest to allow you to maintain a fixed temperature during your testing which takes ??minutes in total.

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

 

[Leonardop318]

Hydraulic oil or something else?

I was initially going to use water, but I couldn't find a pump that fit the system necessities, and I'm still trying to decide what liquid I could use. I'd say no hydraulic oil though.

 

[Leonardop318]

Would a simple plunger work to change system pressure? Use it to decrease or increase system volume with corresponding pressure increase or decrease.

Do you mean as the second pump or as the main one?

 

[Leonardop318]

The volume would be around 5 liters.

As in the other post, I would recommend you use a cylinder off the system about 50/50 air / gas of around 5% of your system volume and then just vary the gas pressure via say a 220bar nitrogen bottle with a pressure regulator.

I'm not sure if I understand this, so by doing this I would add air/gas to the fluid? what I'm trying to measure is density, so I think this wouldn't be a good idea (please correct me if I'm wrong). I would like to know more about it though, can you tell me where I could find some info?

As for the heat exchanger, my plan is using a counter flow HX fed by something like this

https://www.coleparmer.com/i/cole-p...ol-bath-20-to-100c-230vac-sku-1212204/1212204

P.S. thanks for your answers guys.

 

[LittleInch]

No I meant add a cylinder at the top of your loop on a tee off. So in your diagram remove the second pump and replace the tank worth a cylinder half full of liquid and half full of gas. Only a very small amount of liquid will enter ir leave the loop when the pressure changes.

If you work or how much (I.e. how small) the ampunt of liquid you need to change pressure then you'll see why a pump isn't the way to go when dealing with a relatively small volume.



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

 

[Leonardop318]

Oh, thanks, I think I get it and sounds pretty interesting.

Could you tell me where can I find a cylinder suitable for the job?, or would I have to design it? if so what would it need?

Do you have any thoughts about the HX?

Thanks again.

 

[LittleInch]

Depends on your volume but you could just use some pipe and connections.

The HX I couldn't see enough data but looks ok on the surface. 80 bar will rule out a lot of things so check that first.

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

 

[hydtools]

Use a bladder type accumulator T'd into the loop. Control the gas pressure on the gas side to control the loop pressure.

https://www.hydraulicspneumatics.co...tors/Article/False/6446/TechZone-Accumulators

Ted

 

[shashankTurbomachine]

Depends on your volume but you could just use some pipe and connections.

The HX I couldn't see enough data but looks ok on the surface. 80 bar will rule out a lot of things so check that first.

A well phrased question has answers in itself!!!

 

[Leonardop318]

Wow, thanks hydtools that's really helpful.

 

[Leonardop318]

Hi everyone,

Sorry to bother you again with the same thing but I still have some questions.

I decided to use the bladder accumulator as LittleInch and hydtools suggested.
By doing this would I need to use a check valve as shown in the image below to avoid flow return?

Besides, the pump I'm going to use requires a differential pressure of at least 2 bar regardless of system pressure, Is there an easy way to do this w/o affecting the flow rate at the inlet of the pump?

Is there anything else I should consider?

Thanks.

 

[LittleInch]

I can't see any good reason for the NRV but doesn't cause any big issue.

Normally you put the connection for the pressurisation loop at the pump inlet to avoid any back flow and it ensures the system always has a set minimum pressure, but if the elevation isn't high then it won't really matter.

Pumps usually do like some sort of back pressure to work against, but usually only when flowing so I would simply use a suitable orifice plate or perhaps a length of smaller bore pipe to generate the required back pressure. A simply globe valve might also work for a test loop situation.

If that's a gear pump then your flow rate is dependent on pump/motor speed and the pressure and power rises accordingly to differential pressure. If it's a fixed speed motor then it's a constant flow rate.

I would also / YOU REALLY NEED TO include a pressure relief somewhere and a fill/drain and vent connections, but assume this is just a simplified sketch.

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

 

[Leonardop318]

Well, I saw some systems with accumulators that used the NRV and thought it may be necessary but was hoping it was not.

Ok, let me see if I understand all this.

First. When you say pressurization loop you mean the accumulator, right? I put it there trying to make sure the pressure in both meters was as similar as possible. The elevation is around 1,5m would that be too high?

Second. I got a little confused here (sorry, English is not my first language) So what the seller told me is that I had to make sure the pump inlet pressure was at least 2 bar lower than the pump outlet pressure. With the orifice plate/smaller bore pipe/globe valve can I achieve this? if so where would you place it?

Third. The system will have a pressure relief valve, a tank connected to the top that will only be open when filling it, 2 drain connections, 1 at each side of the pump, and 1 air release & vacuum breaker valve at the top.

P.S I really owe you a beer LittleInch, thanks a lot for your help.

 

[LittleInch]

1 / correct. 1.5 m is not worth bothering about
2) Yes in operation you can do that. I would put it downstream of the pump before the first meter and then adjust your pressure in operation to be whatever you want it to be.
3) I would connect the fill line at the lowest point to drive all the air out when you're filling it otherwise you will spend forever trying to get air bubbles out of your loop. I wouldn't bother with a vacuum breaker - just open the valve. Getting a VB rated for 80 bar might prove quite difficult and you don't need it.


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

 

[Leonardop318]

Wouldn't that (installing the fill line at the lowest point) require external pumping to get the fluid to the highest point? or just turning on the system pump would do the job? (it's a screw pump btw)

Getting a regular air release valve rated for 80 bar has already proved difficult, isn't it possible to get a lower pressure-rated valve connected to the system using a suitable ball valve and after making sure the air is already vented shut the ball valve? or should I keep looking?