Pressure regulator type 149 with or with out incorporated safety shut off device
Pressure regulator type 149, 149-BV is pilot operated gas pressure regulator for high pressure, which ensure a constant downstream pressure (p). The regulator is controlled by a pilot. 2 They can be provided with shut-off device for low and high pressure or for high pressure. They can be used with natural gas, LPG, air, nitrogen, etc.
Gas pressure regulator type 149- BV consists of gas pressure regulator type 149, safety shut off device, first stage pilot regulator type 118- PP, second stage pilot regulator type 119 and choke valve. Named devices are interconnected using impulse pipes. In the absence of pressure, gas pressure regulator type 149- BV is closed ie, shutter is pressed on the nozzle due to force of the spring. SSD pad unit (8) is spaced from the nozzle and gas flows toward lower part of the shutter.
If main regulator inlet pressure value is higher than 25 bars, pilot regulator type 118- PP is build in. When gas is released in the installation, it passes through regulator’s housing and openings in the shutter and enters pilot type 118- PP through the connector. Pressure in pilot type 118- PP is adjusted according to main regulator set pressure (p ‘= p + 2 bars). Gas from pilot 1 set type 118- PP is delivered into pilot type 119 with impulse pipes. Main components of pilot type 119 interrelates according to set pressure thus creates the control pressure which is delivered to lower diaphragm housing (8). Control pressure generates force which lifts the diaphragm and consequently separate the shutter from the nozzle.
This pressure also arrives in the upper diaphragm chamber through choke valve establishing balance of the forces. Upper diaphragm chamber discharges in outlet pipeline through the impulse pipe. Thereby, the shutter positions relative to nozzle in such a way to provide the set pressure value. Choke valve provide inertia needed for fine operation of regulator. From downstream regulator, impulse pipe bring outlet pressure above main diaphragm and bellow pilot type 119 diaphragm. Increase in outlet pressure closes the pilot type 119 which leads to decrease in control pressure. Also, increase in outlet pressure above the main diaphragm closes the regulator until balance is reached again.
This way, outled pressure value remains unchanged within accuracy group AC. If outlet pressure decreases the opposite happens. Gas pressure regulator type 149- BV is fail close ie, when diaphragm fails, values of pressure above and under it will equalize, so spring force pushes diaphragm assembly downwards. This motion is transfered through the rod causing the shutter to move toward the nozzle seating surface to disable flow. There is an option of heating of pilot type 118- PP using warm water (90/ 70 °C) in order to prevent freezing.
Gas pressure regulators type 149 and type 149- BV are equiped with a pilot type 119. Pilot type 119 is used for high pressure control. In the absence of pressure, pilot is in open position, i.e. force of the spring, through stirrup act on the rod and maintain the nozzle opened. Gas from first stage pilot type 118- PP (at pressure p ‘) is brought at pilot type 119 inlet. Outlet pressure from regulator p , through impuls pipe, act on lower diaphragm, and together with spring maintain the control pressure p constant. Control pressure is through impuls pipe bringed up at the lower side of regulator diaphragm. At the setted value of control pressure, pilot is still opened, and gas flows from lower dipahragm hosuing of regulator to upper dipahragm housing of regulator.
Further increase in pressure p close the pilot and pressure in uper and lower dipahragm housing is equalised. Regulator spring close the regulator. Set point of control pressure p is established by the adjusting screw and the spring. In order to increase control pressure,rotate the adjusting screw clockwise, and to decrease the control pressure rotate the adjusting screw counterclockwise. Diaphragm reduction insert is build in for pressures from 16 to 40 bars. For pressures from 1 to 16 bars diaphragm reduction insert is not fitted in pilot. For pressures from 40 to 75 bars instead of a membrane is build piston.
Gas pressure regulators type 149 and type 149- BV are equiped with a pilot type 118- PP when inlet pressure is higher than 25 bars. Pilot type 118- PP is used for high pressure control. In the absence of pressure, pilot is in open position, i.e. force of the spring, through rod act on the shutter and maintain the nozzle opened. Gas from regulator inlet (at pressure p ) is supplied to pilot type 118-PP inlet and flows over perforated sieve and filter cartridge to reach the nozzle.
Outlet pressure from regulator p, through impuls pipe, act on diaphragm, and together with spring opposes inlet pressure thus insures the value of pressure p ‘ to stay constant. Pressure p ‘ is through impuls pipe bringed up at the pilot regulator type 119 inlet. Hot water (90/ 70 °C) flow channels are drilled in the body of pilot regulator type 118- PP to prevent it from frezzing during pressure reduction process. Heating of pilot regulator is optional, not mandatory.
SHUT-OFF DEVICE OPERATION (FOR REGULATORS SIZE DN25 ÷ DN50)
Gas pressure regulator equiped with shut-off device is called 149-BV. Protecting the instalation and the consumers after regulator against extreme (high and low) pressure is the basic function of shut-off device (protection against only high pressure upon request).
Shut-off device for protection against high and low pressure are:
– 1 – 10 bar type : GT.BM.VNP.25÷50.100-06.P.Z.00.00
– 5 – 30 bar type: GT.BM.VNP.25÷50.100-20.P.Z.00.00
– 25 – 75 bar type: GT.BM.VNP.25÷50.100-75.P.Z.00.00
Operation shut-off device for protection against low and high pressure is explained in folowing text. Outlet pressure intake through the pulse pipe under the diaphragm assembly. Pressure increasing move the diaphragm assembly upper, through lever cause moving of rod which release the tooth from the rod. The rod under the spring load move the pad unit to close the nozzle. Increasing outlet pressure act uppon diaphragm assembly and overcome the high pressure spring load (VP). Decreasing outlet pressure move the diaphragm assembly down under the low pressure spring load (NP) and through lever move the rod and release the tooth from the rod.
Activate pressure is realized by setting springs and by adjusting ring for VP and adjusting ring NP. Rotate adjusting ring clockwise for increase pressure or rotate adjusting ring counterclockwise to decrease activating pressure. Shut-off device is manualy reset by turning the wheel. Shut-off device used only for protection against high pressure is equipied without spring NP and adjusting ring for NP.
SHUT-OFF DEVICE OPERATION (FOR REGULATORS SIZE DN65÷DN200)
The impulse line takes the outlet pressure gas p to the shut-off mechanism pilot, which is an actuator of the shut-off mechanism. The pressure increase from p to p increases the force acting on the diaphragm (a) of the shut-off blv mechanism pilot and releases the high pressure spring (b), which results in axial movement of the pilot lock stem (c), which turns the key of the shut-off mechanism (e) by a puller (d).
By turning the key, the space for the lock ball is provided (f) and the stem (g) forced by the spring pushes the lock head (h) against the seat stops the gas flow. A pressure drop from p to p decreases the force that acts on the pilot diaphragm of the shut-off mechanism, causing the low pressure spring (i) to move the pilot lock stem, which activates the shut-off mechanism as in the previous case. Deactivation of safety shut-off device (mechanism):
Protection against high and low pressure:
– close the globe valve at the outlet of the regulation line.
– turn the handwheel (clockwise) and equalise the pressure and then continue to turn the handwheel in order to
unlock the mechanism.
– gradually open the globe valve at the outlet of the regulation line