I have an application where my P1=10 barg, P2=3.5 barg, max flow required is 1150 Nm3/hr of air. As I have a flow meter downstream of the regulator that requires 20D of undisturbed straight runs, just wondering if the Type 299H would be more suitable for my application, since its dual registration design has no downstream bleed if I understand the product bulletin correctly. If I understand correct, both the Type 99 and 1098 require downstream bleed with the external registration design. Is this correct?
Great to see you in the community, Eric. I reached out to a few of our Experts, look for some solutions to be posted here soon. :)
Best Regards,
Rachelle McWright: Business Development Manager, Dynamic Simulation: U.S. Gulf Coast
In reply to Rachelle McWright:
Hello,
The 299H with dual registration will sense internally and externally. I am a bit confused on what you meant by no downstream bleed. However yes the 299H with the 3/4" orifice will be suitable for your application.
The Type 99 and 1098 both do require sensing lines, i.e. they are designed with external registration.
Back to the 299H, you will also need to install a control line but with dual you get a faster speed of response due to the internal sensing capability.
Hope this answers your questions.
In reply to Fernando_Gallegos:
I'll add one note:
I believe what you are refering to is the no-bleed MONITOR configuration of the 299H. The monitor configuration adds a level of added safety to your system by allowing for a backup pressure regulating device to take over pressure control in the event of a primary regulator failure. Unfortunately at your process conditions this option is not available.
The 299H, type 99 and type 1098 will all have a downstream bleed when used in a single regulator (non-monitor) configuration. This is the nature of a pilot operated regulator. However I'm not exactly sure how this would play into your flow meter operation?
Is there a specific concern that is being brought up?
Jake Buford
In reply to Jake Buford:
If Etam concerns about the sensing port between 299H outlet and flow meter will disturb the fluid and impact the flow meter accuracy, to put the flow meter (10D looks orifice plate or tubine flow meter) before regulator can help good flow measurement and also achieve the pressure control by 299H, 99 or 1098.
In reply to Lucy_Liu:
Hi Guys,
Thank you for your valuable replies, which helped me to understand the characteristics of these Fisher regulators. For some reasons that I don't understand, I did not receive any notifications on updates to this thread, hence my late reply.
Lucy's understanding of my flow meter concerns is correct. The suggestion to install the flow meter 10D upstream of the regulator is a good idea, which I didn't think of before. However, the drawbacks I see in my case are that the fluctuating upstream pressure might reduce the turndown performance of the flow meter and also increase the length of my skid's footprint. Since I also need to monitor the differential between the two gas streams after pressure regulation, I'll also need to install an additional pressure transmitter (one for flow meter and one for regulator downstream).
Jake,
While researching though my regulator options, I found a pilot operated regulator option that features a static pressure sensing line with no downstream bleeding:
onedrive.live.com/redir
The pilot in this setup works in the opposite way as in conventional pilot operated regulators by controlling the bleed rate of gas that was initially balancing the pressure on the two side of the elastic sleeve when P1 = P2. When P2 < P1, gas from P1 is bleed off through the pilot and into the downstream port of the AFV. As gas from the supply port is being restricted, this creates a negative pressure relative to P1 and allows the elastic sleeve to lift up from the flow cage, creating flow. This seems to be an advantage if there are flow sensitive instruments installed downstream of the regulator such as flow meters.
In reply to Eric Tam:
Would love to hear more thoughts on the pilot operated regulator? Eric, we had an issue with some email notification getting stuck on the server, but those issues have now been resolved with our hosting team--we apologize for the inconvenience. That said, if you get this note in a timely manner, it will verify the fix "sticks". :)
Thanks Rachelle for giving me the heads up, I got the notification.
Cheers, Eric
Eric,
The regulator you posted about appears to have a downstream bleed as well. The operation of that regulator appears to be similar to the type EZR regulator, please see the link below:
www2.emersonprocess.com/.../ezr-ezrosx.aspx
I still am not sure the bleed would affect the flow meter operation however. The bleed is discharging into the main line, so any bled fluid would immediately be assimilated into the flow of the valve. The amount of fluid being bled into this main line would be almost infinitesimally small compared to the overall flow of the valve and wouldnt cause any added turbulence to the flow of the valve.
Thank you for sharing the link to the EZR regulator. I downloaded the product bulletin and read through it, but found that the pilot setup of this regulator still requires the gas to be bled at the sensing line downstream of the regulator, which might disturb the gas flow into the flow meter.
The design of the EZR is similar to the AFV in a way that the loading pressure is negative relative to the pressure exerted on the plug diaphragm by the main spring (as opposed to 1098's positive loading pressure). It similarly uses a restrictor to create this negative pressure by venting the gas to the downstream. The difference is that the AFV vent this gas right at the discharge port of the valve rather than at the end of the sensing line, hence the bleed gas is immediately assimilate into the high velocity flow stream and causes no additional flow disturbance downstream of the regulator. In the case of the AFV, the gas flow in the pilot sensing line is completely static.
Even though the flow of this bleed gas is relatively small compare to the overall flow of the valve, but if the sensing port is located near enough to the upstream of the flow meter, this bleed gas would be injected at right angles to the main gas stream and would definitely cause a disturbance. Although I have no idea on the magnitude of this disturbance, but a typical velocity based flow meter would require a minimum straight runs of 15D downstream of a pipe reducer, 20D downstream of a pipe elbow and up to 50D downstream of a valve/regulator, which appears to me that the designer of the system should by all means avoid any kind of flow disturbance immediately upstream of the flow meter in order not to compromise accuracy of flow measurements.
Hi,
what about changing the flowmeter to a type that doesn´t require almost no straight runs..
eg. www2.emersonprocess.com/.../index.aspx
Niklas Flykt
Klinkmann Oy
Key Account Manager safety products
nikfly@gmail.com
In reply to Niklas Flykt:
Hi Niklas,
I did consider the Coriolis flow meters before, but both the capital investment (price of instrument and installation) and cost of ownership (energy loss due to pressure drop, calibration cost) is about 4 times the amount of vortex flow meters.
The high art of engineering would be to fulfil the purpose with the best balance between price/performance/maintainability. If by selecting the right type of regulator would achieve the intended purpose while keeping the cost at bay, I would rather attempt that direction first.
Nevertheless, there are situations where only coriolis meters would make sense, such as CNG dispensers where the whole metering station has to be fit inside a very small package and you don't have any luxury of pipe runs.
Hi etam_itm,
I´m sure somebody from the flowside also in this media, would be happy to explain the cost/pressure drop etc. between Coriolis and vortex :)
I checked that if I use the same DN40 size Coriolis meter to measure the same flow rate of compressed air at 3.5 barg, it would produce 0.82 bar drop across the flow meter at 1200 Nm3/h flow, which is about 4.3 times the pressure drop with the same size vortex meter. This means the air compressor would have to work harder to compensate for this loss, which is pure wasted energy. If I need a rather stable downstream pressure, such as in the case of gas mixing, I would have to add a remote pilot setpoint adjustment kit to my regulator, which also add cost/complexity to the system.
As a Coriolis meter is far more complex than a vortex meter, the 4 times higher cost is not an overstatement.
I think we have locked down the question: The regulators you discussed above (Type 99, 299) will NOT bleed down the sensing line downstream. They bleed into the discharge port of the valve as well.
But both my experience with the 299H and the product bulletin of these two regulators stated that they do bleed downstream via the control line. Below are excerpted from the 99 and 299H product bulletin:
99:
• No Atmospheric Bleed—Loading
pressure bleeds downstream through
pilot via downstream control line. No
bleed occurs when regulator is shut off.
(Page 2)
299H:
When the gas demand in the downstream system
has been satisfied, the outlet pressure increases.
The increased pressure is transmitted through the
downstream control line (for external or dual registration)
or through the port (G) (for internal registration) and acts
on top of the pilot diaphragm (F). This pressure exceeds
the pilot spring setting and forces the diaphragm down,
closing the orifice (C). The loading pressure acting on
main diaphragm (E) bleeds to the downstream system
through a bleed restriction (H).
(Page 6)
The only exception is the 299H operating in Internal Registration mode, but the drawback is less accuracy and higher droop.