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Regulating Valves vs. Modulating Valves

02/23/2010 8:43 PM

Frankly,is there any real difference between regulating valve and modulating valve?

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#1

Re: regulating valve and modulating valve

02/23/2010 9:06 PM

I could be wrong but my understanding is that a regulating valve is used to regulate the pressure or flow to keep a constant output pressure or flow when the input varies. A modulating valve does the same thing but is used where the pressure or flow rate changes very rapidly and must be compensated very quickly.

More knowledgeable people will give you a much better explanation, but may take a little time.

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#2

Re: Regulating Valves vs. Modulating Valves

02/24/2010 10:37 PM

A regulating valve requires no external energy source.

It is a fully mechanical device and self-contained. It has its own built in controller and the operating energy is taken from the process.

A modulating or control valve requires an external energy source, normally an air supply.

Control valves also receive a command signal from an external controller.

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Anonymous Poster
#3
In reply to #2

Re: Regulating Valves vs. Modulating Valves

02/24/2010 10:47 PM

To know more about regulators and control valves I reccommend you to purchase following book:

Control Valve Primer, 4th Edition, ISA Press. It was written by Hans D Baumann.

David Rodrigues

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#4

Re: Regulating Valves vs. Modulating Valves

02/25/2010 8:10 AM

Regulating valve - controls pressure or flow applied to the valve to hold it constant or in a tight range. Typical use is to maintain a lower limit for back pressure on a plant water supply loop, so as use increases, there is still some pressure maintained at the drops. It is placed at the end of the loop, after all tap offs and before the supply tank.

Modulating valves typically run across a broader range and are often used to regulate the pressure or temperature of the line they are in, but the end result is tight regulation of another process. They usually have an external input to control them, often in another line.Typical use of a control valve is in the utility feed to a heat exchanger to control the heating or cooling rate of the exchanger. This regulation is based on the temperature of the process side output, and is the process being held to a tight range, not the utility process. The modulating valve is sized to allow a typical range of 30% to 70% modulation, but the temperature of the process side output is held in a few degree range.

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#5

Re: Regulating Valves vs. Modulating Valves

02/25/2010 11:12 AM

Hi wingman1985,

My answer will probably cotradict some of what has been said already.

The regulation valve is essentially a commissioning device and is typically found on HVAC installations where it provides a semi-permanent flow control by virtue of having a lockable element forming part of the body. Once set, usually done during the setting up of the installation it will remain unaltered. Sometimes called DRVs or double reg valves they can also feaure pressure tappings which enable flow readings to be obtained when coupled to an appropriate instrument.

The modulating valve comes in many forms but is essentially an actuator controlled 2,3 or 4-port device which varies the flow of the energy carrying media from shut-off to full flow. It would therefore be found downstream of the regulating valve which would be used to set the maximum load flow requirement.

As has been said the actuation of this type of valve can be direct acting where the signal is derived from either a temperature or pressure sensing element or from a controller using electronic measurement and converting to a 4-20mA output proportional to the deviation to set point.

You will see from this that there is a profound difference in the MO of these two types of valve and each has a specific role to play in the management of fluid flows.

Hope this helps.

Massey.

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#6

Re: Regulating Valves vs. Modulating Valves

02/26/2010 12:30 AM

From Tim Hawley Master Mech

Hello wingman1985,

A regulating valve allows you to preset and regulate or maintain a specific pressure or flow rate. They require an in-line solenoid valve to turn on and off pressure or flow.

A Modulating Valve can be turned on the off while regulating a specific temperature or pressure.

Examples: A home furnace has a regulating valve that meters the gas pressure and flow. The modulating valve is controlled by thermo couple. If the thermo couple doesn't detect the pilot light has a flame it will not allow the solenoid modulating valve to open allowing gas to flow, (Safety).

Also if the heat coil doesn't detect the heat exchanger has reached a specific temperature it will not turn on the forced air blower. This could be considered a modulating switch with dual purpose. If the heat coil gets to hot it will cause the modulating valve to closed, shutting off the gas not allowing it to flow (Safety).

Regards,

Tim

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