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 How to choose RDG (gas pressure regulator)

 

 Selection of RDG should be done taking into account the following indicators:
- type of gas;
- the designation of the facility where the RDG will be installed;
- gas consumption (max and min value);
- pressure at the input (max and min value);
- pressure at the output (max and min value);
- accuracy of adjustment (class AC);
- whether it is necessary to completely shut off the gas when the RDG is closed;
- are there any restrictions on the noise produced in the place where the RDG is installed.


The main attention should be paid when selecting the RDG for the stability of its operation in various modes. If the gas pipeline is deadlocked (gas is taken at the end of the gas pipeline), then it is better to use a static direct action RDG (PD). For consumers with a large gas consumption is better - indirect action (ND). For branched and ring gas distribution systems (gas distribution networks), taking into account their possibilities for self-leveling, it is allowed to apply all types of RDG, however, since the GDS data traditionally have a significant design capacity, it is better to use astatic RDG ND (with the pilot). The data of the RDG ND allow an accurate maintenance of the required outlet pressure.
Usually, the accuracy class of the adjustment for static RDG PDs is ± (0-20)%, while for static RDG ND (with pilot) and astatic RDG ND - ± (5-10)%.


When regulating on high pressure GRS, with large changes in pressure, and taking into account actually existing RDG systems, one-stage RDG can not always be used. In this case, you can use a two-stage RDG, or use a two-stage reduction, in which at first one RDG reduces the pressure value to an average value, and the second RDG - to the desired with the highest accuracy.


Choosing the RDG, you need to take into account the acoustic characteristics, because when the gas passes under high pressure through the device and the high performance of the RDG there is a rumble. Its occurrence is due to gas-dynamic vibrational motions in the design of the RDG during the passage of gas. If the operating frequency of the oscillation frequency falls into resonance, a rapid increase in the oscillations is possible, which can lead to deterioration and destruction of the valve, to strong oscillatory movements of the RDG itself. To reduce the oscillation amplitudes, a perforated sleeve is used at the outlet after the device.


The throughput of the RDG is also calculated as the flow of gas through a convergent nozzle or nozzle of an unchanged cross section, given that the process is adiabatic. With constant input pressure P1, flow velocity and gas flow rate increase with decreasing pressure at outlet P2 only to the value P2 / P1, which is defined for a given gas value, they are called critical (P2 and P1 are absolute pressure).
In natural gas (PG), for which the adiabatic value is K = 1.31, this critical ratio is assumed to be 0.5. Those. In the RDG, which at the output of 2 kPa, and at the inlet pressure of 0.1 MPa and above, a critical gas flow regime begins. And the speed of the flow of gas passing through the saddle is unchanged and = the speed of sound in this gas reached at a critical pressure ratio.


When selecting RDG proceed from the fact that the reserve capacity is 15-20% of the maximum gas flow per hour. That is, the RDG at the highest flow will work at 80-85% of its throughput, and at the lowest flow rate - no less than 10%. If the specified reserve standards are not met at the maximum gas consumption, the RDG will fully open and in no way be able to regulate the gas. Adjustment is only guaranteed when the free flow of the service valve is reserved. If the gas consumption is lower than the minimum, the vibration (vibration, ripple) of the RDG may appear.
In GDS systems, the most frequently used RDG with a single-stage automatic adjustment of direct action with a spring and lever-spring mechanism. A detailed description of such gas regulators can be found in the Products section.