Gas pressure regulators 137-BV pilot operated for low and medium gas pressure
Gas pressure regulators 137-BV is pilot operated gas pressure regulator for low and medium pressure, which ensure a constantdownstream pressure (p ). The regulator is controlled by a diaphragm and spring. 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 regulators type 137-BV in its initial position (no gas in the pipeline) is closed, i.e. spring force presses the pad unit against the nozzle through the rod extension and and the rod. The shut-off mechanism head (x) is spaced from its seat on the lateral side of the nozzle carrier allowing the gas flow to the nozzle carrier interior and the pad unit. The pilot is in the open position. When gas in the installations is at pressure (p ), it enters the regulator body and reaches the pilot through 1 the connection. The relationship between the actuators (diaphragm, spring) is established in the pilot according to the set outlet pressure. This leads to the formation of a control pressure, which enters the chamber above the regulator diaphragm via an impulse line, and pulling the diaphragm, it separates the pad unit from the nozzle. Gas flows into the chamber under the membrane establishing the balance, while the bottom chamber is discharged to the outlet line via the impulse line. In this way, the balance is established, which provides the value of the set outlet pressure. The pressure increase causes the gas to enter the pilot and the bottom diaphragm chamber via the impulse line (upstream of the regulator), closing the pilot. The values of the control pressure (under the diaphragm) and the outlet pressure (above the diaphragm) are almost equalised, causing the spring to push the entire diaphragm assembly, rodand pad unit, thereby reducing the outlet pressure to the set value. If the outlet pressure has a tendency to decrease, the opposite happens. These pressure changes are within the limits defined by the regulation unit (AC). This type of the regulator integrates a balance diaphragm, which ensures better regulation and considerably higher flow. Pressure regulator type 137-BV, when failed, is in the closed position In the case that the diaphragm breaks, the pressures above and under the diaphragm equalise causing the spring to close the regulator.
Gas pressure regulators type 137-BV are equiped with a pilot type 117. Pilot type 117 is used for low and medium 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. Letting the gas (inlet gas in regulator p ) in installation, gas flow through the pilot and through impuls pipe act on upper side of regulator 1 diaphragm. Outlet pressure from regulator p2, through impuls pipe, act on diaphragm, which together with spring maintain the control pressure p constant. Control pressure is through impuls pipe bringed up at the upper side of regulator diaphragm. At the setted value of control pressure, pilot is still opened, and gas flow from upper dipahragm hosuing of regulator to lower dipahragm housing of regulator. Further increase od pressure p2 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 clockwise the adjusting screw , and to decrease the control pressure rotate counterclockwise the adjusting screw.
SHUT-OFF DEVICE OPERATION (FOR REGULATORS SIZE DN40 ÷ DN80)
Gas pressure regulator equiped with shut-off device is called 137-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:
– 0 – 2 bar type : GT.BM.VNP.02.65.P.Z
– 2 – 4 bar type: GT.BM.VNP.04.65.P.Z
Shut-off device for protection against high pressure are:
– 0 – 2 bar type : GT.BM.VP.02.65.P.Z
– 2 – 4 bar type: GT.BM.VP.04.65.P.Z
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 valve disc 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 pulling handle. Shut off device used only for protection against high pressure is equipied without spring NP (8) and adjusting ring for NP.
SHUT-OFF DEVICE OPERATION (FOR REGULATORS SIZE DN100)
The impulse line takes the outlet pressure gas p to the shut-off mechanism pilot, which is an actuator of the shut-off 2
mechanism. The pressure increase from p to p increases the force acting on the diaphragm (a) of the shut-off 2 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. (see picture 5.)