FORM 2
THE PATENTS ACT. 1970 (39 of 1970)
COMPLETE SPECIFICATION (Section 10, rule 13)
A PILOT OPERATED GAS PRESSURE REGULATOR CONFIGURED TO FAIL OPEN
Chemtrols Industries Limited
an Indian Company registered under the provisions of the Companies Act, 1956, with our Corporate office at Amar Hill, Mumbai 400 072., Maharashtra, India.
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

FIELD OF INVENTION
The present invention relates to a pilot operated gas pressure regulator configured to fail open.
BACKGROUND
Pressure regulators are devices designed to monitor and control the amount of pressure running through a system of some type. Regulators are used to allow high-pressure fluid supply lines or tanks to be reduced to safe and/or usable pressures for various applications. A pressure regulator -must supply a quantity of flow that matches a downstream, usage, demand. If the required flow rate is small, the regulator plug or disk should approach its seat and restrict the flow. When the demand increases, the plug or disk should move away to create a larger opening. Ideally, a regulator should provide a constant downstream pressure while delivering the required flow. Therefore, regulators automatically adjust the flow rate to meet the downstream demand. Typically, gas pressure regulators are of two categories:
a) Self-Operated/ Direct-Operated Pressure Regulator; and
b) Pilot-Operated Pressure Regulator.
a) Self-Operated/ Direct-Operated Pressure Regulator: Direct-operated regulators have three
essential elements:
i) Restricting Element: The regulator's restricting element is generally a disk or plug that can be
positioned fully open, fully closed, or somewhere in between to control the amount of flow.
When fully closed, the disk or plug seats tightly against the valve orifice or seat ring to shutoff
flow.
ii) Measuring Element: The measuring element is usually a flexible diaphragm that senses
downstream pressure as pressure beneath it changes. The restricting element is often attached to
the diaphragm with a stem so that when the diaphragm moves, so does the restricting element.
iii) Loading Element: A weight or spring acts as the loading element. The loading element
counterbalances downstream pressure unbalance between the loading element and the measuring

element determines the position of the restricting element. Therefore, we can adjust the desired amount of flow through the regulator, or set point, by varying the load. Some of the first direct-operated regulators used weights as loading elements. Most modern regulators use springs.
An example of a self-operated regulator is a spring-opened valve directly opposed by a diaphragm assembly at increasing downstream pressure, acts on the diaphragm assembly to overcome the force of the spring, closing the valve. When downstream pressure falls, spring force is greater than the force of the gas acting on the diaphragm and the valve opens. In all type of regulator valves, a control inaccuracy caused is by "droop" or "offset". Offset effect occurs as the demand for gas in the downstream system increases. When the regulator is required to pass more gas to the downstream system, the regulator valve plug must be opened to allow more flow. To allow this opening of the valve plug, the downstream pressure sensed by the diaphragm must decrease. By allowing the downstream pressure, to decrease, less , force opposes the compressed spring and the valve plug is pushed farther open to meet the flow demand of the system. The net effect is a decrease or offset of downstream control pressure from the desired set pressure.
b) Pilot-Operated Pressure Regulator: In the evolution of pressure regulator designs, the shortcomings of the direct-operated regulator naturally led to attempts to improve accuracy and capacity. A logical next step in regulator design is to use what we know about regulator operation to explore a method of increasing sensitivity that will improve all of the performance criteria.
To improve the sensitivity of the regulator, a downstream pressure is to be sensed and then somehow make a change in loading pressure that is greater than the change in downstream pressure. To accomplish this, a device called a pilot can be used. The major function of the pilot is to increase regulator sensitivity. If we can sense a change in downstream pressure and translate it into a larger change so that the regulator will be more responsive (sensitive) to changes in demand. In addition, droop can be significantly reduced so its effect on accuracy and capacity is minimized.

OBJECTIVES
An object of the present invention is to regulate the gas pressure with maximum possible
accuracy.
SUMMARY OF THE INVENTION
Present invention introduces a device for regulating gas pressure in a pipe or duct carrying high pressure gas. The pilot operated gas pressure regulators are commonly used in high pressure natural gas pipelines. This device has an additional function of opening the regulating shutter in case of any failure in the actuating mechanism or power source for actuation. Such a regulator is generally referred to as a regulator configured to Fail Open. By doing so it allows the use of a second regulator of the Fail Close configuration connected downstream to take over regulation and provide gas downstream without interruption.
BRIEF DESCRIPTION
Figure 1 illustrates a schematic of a pilot operated gas pressure regulator of present invention.
DETAILED DESCRIPTION OF THE INVENTION
Present invention introduces a device for regulating gas pressure in a pipe or duct carrying high pressure gas. The pilot operated gas pressure regulators are commonly used in high pressure natural gas pipelines. Natural gas is transported through pipelines under high pressures to minimize the cost and for convenience. At the point of use the pressure required is much lesser than the high pressures at which it is transported. This pressure reduction is achieved through pressure regulators at different stages. The flow rate of the gas depends on the consumption of the gas by the end users and a constant supply pressure is maintained by a regulating valve which responds dynamically to these changes in the flow rates.

The device of present invention comprises a control valve with an inlet chamber connected to the high pressure gas duct (1), an outlet chamber connected to the low pressure gas delivery line (2), and an intermediate path connecting the inlet chamber and the outlet chamber.
With reference to figure of the invention, the intermediate path has a regulating shutter (3) or closure element which opens or closes the path. The control valve further comprises of integral actuator comprising an upper chamber (4) and a lower chamber (5) separated by a flexible diaphragm (6) which is attached to the closure element with a rigid rod; and is adapted for closing or opening the closure element (7).
According to yet another embodiment of the present invention, the device further has a first compression spring (8) which is located in the lower chamber of the actuator, exerting an upward force to the regulating shutter and moving it up to open the valve. The pilot (9) is supplying the motorisation pressure to the upper chamber as well as an intermediate pressure less than the motorisation pressure to the lower chamber. The pilot is responsible for sensing the pressure in the delivery line and comparing the pressure with the set pressure. When the sensed pressure is more than the set pressure, the pilot will supply the motorisation pressure to the upper chamber of actuator. The force due to the motorisation pressure is more than the combined effect of spring force and the force due to the intermediate pressure. So the net downward force moves the regulating shutter down and closes the regulator.
When the sensed pressure is same as that of the desired set pressure, the net force acting upwards is equal to the net force acting downwards and thus regulating shutter being remaining stationary. On the other hand if the sensed pressure is less than the desired pressure, the nozzle in the pilot connecting the motorisation pressure and the intermediate pressure is opened. So the motorisation pressure acting in the upper chamber is equal to the intermediate pressure acting in the lower chamber. When there is no net differential pressure across the diaphragm the spring force will tend to open the regulating shutter, resulting in increase in the delivery pressure. The net force acting against the force due to the differential pressure across the diaphragm is the

resultant of the spring force, the weight of the moving parts and the various frictional forces on the moving parts.
The performance of a regulator is assessed by its ability to maintain a constant pressure in the gas delivery line over a large range of operation of the valve, and by the variation it toleratesin the desired set pressure and hence the response of the regulator to a disturbance in the system must be adequately fast. So when there is a disturbance in the pressure in the delivery line, the motorisation pressure must be able to bring about the desired change at the earliest. The frictional drag may lead to delaying the regulation, affecting the regulation accuracy of the regulator. The device of the present invention further has a second compression spring (8). located on the top side of the diaphragm. This additional compression spring helps in overcoming the drawback of the regulator of moving the regulating shutter only when the differential pressure increases to such an extent as to overcome the resultant spring force as well as the drag forces on the moving parts. The second compression spring (8) provides a force sufficient enough to overcome the static forces acting against the closing movement and thereby keep the system in a state of dynamic balance which increases the response and thereby the performance of the regulator.

We claim,
1. A pilot operated device for regulating gas pressure; the device comprising a control valve with an inlet chamber connected to the high pressure gas duct, an outlet chamber connected to the low pressure gas delivery line, and an intermediate path connecting the inlet chamber and the outlet chamber and having a regulating shutter or closure element which opens or closes the path.
2. A device as claimed in claim 1, wherein the control valve further comprises of integral actuator comprising an upper chamber which being connected to the low pressure delivery line and a lower chamber separated by a flexible diaphragm which is attached to the closure element with a rigid rod; and is adapted for closing or opening the closure element.
3. A device as claimed in claim 1, wherein a pilot is meant for supplying motorization pressure to upper chamber of the actuator and further adapted for sensing the pressure in the delivery line and comparing it with the set pressure.
4. A device as claimed in claim 1, wherein the device has a first compression spring located in the lower chamber of the actuator, exerting an upward force to the regulating shutter and moving it up to open the valve.
5. A device as claimed in claim 1, wherein the motorisation pressure being supplied from the pilot to the upper chamber and to an intermediate pressure less than the motorisation pressure
to the lower chamber.
6. A device as claimed in claim 1, wherein when the sensed pressure is more than the set
pressure, the motorisation pressure is supplied from the pilot to the upper chamber of actuator;
the force due to the motorisation pressure being more than the combined effect of spring force
and the force due to the intermediate pressure resulting the net downward force to move the
regulating shutter down and closing the regulator.

7. A device as claimed in claim 1, wherein when the sensed pressure is same as that of the desired set pressure, the net force acting upwards is equal to the net force acting downwards and thus regulating shutter being remaining stationary.
8. A device as claimed in claim 1, wherein when the sensed pressure is less than the desired pressure, the nozzle in the pilot connecting the motorisation pressure and the intermediate pressure is opened; the motorisation pressure acting in the upper chamber is equal to the intermediate pressure acting in the lower chamber.
9. A device as claimed in claim 1, wherein when no net differential pressure across the diaphragm, the spring force open the regulating shutter, resulting in increase in the delivery pressure; the net force acting against the force due to the differential pressure across the diaphragm is the resultant of the spring force, the weight of the moving parts and the various factional forces on the moving parts.
10. A device as claimed in claim 1, wherein the device further has a second compression spring located on the top side of the diaphragm, being responsible to give a force which is sufficient enough to overcome the force required to further compress the spring, the force required to overcome drag forces and any static force acting against the movement of closure element, thereby keeping the system in a state of dynamic balance and increasing the response and the performance of the regulator.