[1] This patent application claims priority to US Provisional patent application No. 62/393,550, filed September 12, 2016. This patent application is incorporated herein by reference in its entirety.

Field of the invention

[0001] The present invention is directed generally to improvements in pilot actuators for dry pipe type fire protection systems, and more particularly to an actuator coupled to hydraulically controlled dry pipe system valve assembly.

Background of the Invention

[0002] The field of fire protection is of extreme importance to life and property. Firefighting system design presents many challenges to the designer including a need to optimize the effectiveness of the fire protection equipment while at the same time minimizing the cost of installation. Fires grow rapidly and so methods to achieve early fire suppression can significantly reduce overall installation costs by minimizing the scale of the system needed to suppress the fire. The requirement for rapid delivery design requirements can drive a need for large pipe and valve diameters, and/or a need for high operating pressures to accelerate fluid delivery.

[0003] Sprinkler systems are standardized nowadays to deliver the fire suppression fluid to the needed sites. Sprinkler systems comprise a primary fluid distribution system having pipes (commonly known as 'sprinkler lines') that communicates a primary fire suppression fluid to a plurality of individual closed nozzles or sprinklers coupled to the primary distribution system. Common types of such systems include, inter alia, wet pipe systems dry-pipe systems, deluge systems and preaction systems. In 'dry -pipe' type firefighting systems fire suppressant is not introduced into the distribution system piping until a fire detection event has occurred.

[0004] Multiple regulatory and private standards define differing types of firefighting systems. By way of example Underwriter Laboratories© of Northbrook IL, USA, commonly known as UL, publishes UL 260, "Standard for Safety" which relates to dry pipe and deluge valves and provides examples of standardization to the differing types of firefighting systems. By way of example a dry-pipe valve type systems are defined in section 5.8. Similarly, FM Approvals© of Thomaston RI, USA publishes "Approval standards for Dry Type Valve" commonly known as FM class 1021 which provides further description in sections 2.1. Further explanation relating to the nature of this types of firefighting systems is provided throughout the UL 260 and FM Approvals "Approval standards for deluge and preaction sprinkler systems" which are incorporated herein by reference in their entirety. Various standards published by the National Fire Protection Association (NFPA) of Quincy MA, USA, deal with sharpening the distinction with various firefighting systems and their components. Such differing standards differ not only by their intended use, but also by their modes of operation and by the requirements which they must meet. Design of those systems present different requirements to the designer, as well as different methods and modes to achieve the requirements, and oftentimes solutions designed for system type would fail to meet the requirements in another system type. Therefore despite the different systems being aimed at firefighting, clear and distinct differentiation must be drawn between the different types as separate fields.

[0005] Accelerated actuation of the fire suppression system is desired in order to speed up fire suppressant delivery. To that end hydraulic control valves were designed, to transition a control valve from a closed to open state (and in certain cases from open to closed state). In a hydraulic valve, fluid pressure is applied to a control chamber, and the resulting force is transmitted to a waterway sealing member, either directly for effecting water seal in the waterway, or via a trip mechanism that holds the waterway sealing member closed against the incoming fire suppressant. After a fire detection event occurs there is actuation reduction of the pressure in the control chamber. The pressure reduction allows the sealing member to open, and allows distribution of the primary firefighting fluid into the firefighting system. Thus the control valve may be in a "closed", (equivalently known as "standby") state where the valve sealing member impedes flow of fluid between the inlet and outlet, and an "opened", (equivalently known as "actuated" or "activated") state in which sufficient pressure is released from the control chamber and primary firefighting fluid is allowed to flow between the inlet and the outlet.

[0006] Hydraulic control valves should be differentiated from differential type control valves, which are defined for example by UL 260 in section 5.7. In a differential type control valve pressure exists in both sides of the sealing member such as a clapper, usually over a larger area on the outlet side and a smaller area on the inlet side, and there is no need for a control chamber - in closed state the pressure in the outlet side of the sealing member imparts a greater force thereupon then the force imparted by the inlet side, and the valve stays closed. When pressure is released from the outlet side, the sealing member opens and primary firefighting fluid is allowed to the outlet side, while simple in principle, purely differential valves are large, heavy, slow, subject to premature operation due to inlet side pressure surges, and oftentimes less dependable than the hydraulic control valve.

[0007] The terms 'hydraulic valve', 'hydraulic control valve' and 'control valve' are henceforth utilized interchangeably and represent any type of valve which controllably in response to pressure in the valve control chamber holds the primary firefighting fluid from entering the primary distribution system, regardless of valve type such as a diaphragm or a clapper valve. The term control valve extends to hydraulic stop valves, and on/off control valves.

[0008] Controlling the control valve is done with additional devices generally called 'trim'. The control valve trim comprises external connections and accessory equipment, and includes an actuation device colloquially known as 'actuator', that when actuated releases the pressure in the control chamber of the control valve, causing the sealing member to open, in effect transitioning the control valve from the closed to open state and releasing the primary fluid from the inlet to its outlet and thus to the distribution piping which then distributing fluid to effect fire suppression in the protected area.

[0009] A common type of firefighting system actuation method is known as a pilot system. In a pilot system pressurized pipe lines are distributed throughout the area to be protected, and one or more sprinklers are connected to the pressurized lines. The purpose of sprinklers is to vent the pilot lines pressure in response to exposure to an ambient temperature exceeding a sprinkler specific temperature threshold. The resulting pressure drop in the pilot lines causes actuation of the firefighting system and primary firefighting fluid is distributed through the primary distribution system. Several types of 'dry' pilot fluids used to pressurize the lines are known, such as air, nitrogen, and the like.

[0010] Fig. 1 depicts schematically a simplified type of firefighting system known as a dry -pipe system. A dry -pipe type system is a special type of firefighting system where the primary fluid distribution system acts as the pilot line system, where system actuation occurs by mechanical device. Stated differently, the inlet of the control valve 10 is connected to a water supply 2, which acts as the primary fire extinguishing fluid, commonly via a shutoff-valve 5. The outlet of the control valve 10 is coupled to the primary distribution system 15, which during fire distributes water to the fire affected zone via a plurality of sprinklers 55. Under standby conditions (no fire detected) the main distribution system is sealed and is pressurized by the pilot fluid. A pressurizing device 50 such as a compressor or a tank is provided to pressurize the system and to compensate for minor leaks. The control valve 10 is a hydraulic valve, having a control chamber 30, which when pressurized maintains the control valve closed. The supply pressure Pw is supplied from the water supply 2 through a check valve 24 and then via a flow restrictor 25 to the control chamber 30 of control valve 10. When at least one of the sprinklers 55 is exposed to ambient temperature above a predetermined setpoint it trips and begins to vent the pilot pressure Pp in the distribution system. Venting the pilot pressure causes triggering of a mechanical device known as a pilot actuator 35 which is coupled to the pilot line system 15 and to the control chamber 30 of the hydraulic control valve 10 via control vent line 20. The pilot actuator 35 releases the control pressure Pc from the control valve 10 control chamber 30, which in turn allows the control valve to open and for firefighting fluid to flow to the primary distribution system 15 and to the area affected by the fire. Notably in this type of system, the pilot line and the distribution line are both denoted by the numeral 15 as they are essentially the same. While certain piping is utilized only for the pilot system, such as by way of example pipe 15A coupling the piping system 15 to the pilot actuator, those lines may be considered part of the system, for practical purposes.

[0011] For brevity the present specifications will describe dry-pipe firefighting system where the primary firefighting fluid is water, and a dry pilot type containing air. The use of the terms water and air should be construed as a shorthand notation for any type of primary firefighting fluid and pilot fluid respectively, within the context of the pilot, distribution, and trim and control system. The term 'water' is used interchangeably to a primary

firefighting/fire suppressant fluid, and the term 'air' to a pilot fluid.

[0012] Unlike, for example a pre-action or deluge type systems where system actuation may be electrical, fluid hydraulic, and the like, the dry -pipe type system control valve must be directly operated by a change in pilot pressure, the change in pilot pressure imparting changing force via a mechanical device comprised of fluid hydraulic and mechanical components cooperatively interacting to operate the hydraulic valve. The mechanical device can be of various arrangements of pressure differentials and their effects on mechanical components such as diaphragms, pistons, pawls, arms, levers, and the like.

[0013] The pilot actuator 35 has a pressure sensing member in communication with the distribution system 15 which is pressurized to act as a pilot line. The pilot pressure Pp acts on a sensing member, and is translated to a sensed force which is mechanically transferred to a pilot actuator sealing member. The pilot actuator sealing member is in fluid communications with a vent line 20 from the control valve control chamber 30, and controllably holds the vent line closed, or vents the content thereof to the atmosphere. The sensed force resulting from pressure in the pressurized pilot/distribution system 15 maintains the control valve control chamber 30 vent line 20 in a closed state by being applied to the pilot actuator sealing member. Upon sufficient pilot line pressure drop, as will be caused by activation of a sprinkler as a result of a fire, the pilot actuator sealing member transitions from the closed state to an open state, allowing the control valve control chamber to vent to atmosphere, resulting in actuation of the control valve, thus delivering fire suppression fluid to the sprinklers via the distribution system to the area to be protected.

[0014] The term 'pilot actuator' , or equivalently 'dry pilot actuator' in these specifications relates to a device which when properly installed in a dry -pipe valve type sprinkler based fire suppression system, acts in response to change in pressure in a piping system, to vent a control chamber of a hydraulic valve of such system, directly or indirectly, to the atmosphere, thus transitioning the force acting on the waterway sealing member directly or indirectly via intermediate components, allowing opening of the hydraulic valve and delivery of the fire suppression fluid to the sprinklers.

[0015] The pilot actuator has a vent port in fluid communications with vent line 20, the vent port is in fluid communication with a sealing port, and henceforth controllably to a drain outlet 40. A sealing member 175 is mechanically coupled, directly or indirectly, to the pressure sensing element, and is moveable thereby between at least a sealed state and an open state, and commonly with a plurality of intermediate states. The sealing member has a seal 180 which cooperates with the sealing port to seal fluid passage through the sealing port when the sealing port is in the closed state, and allows at least partial fluid communication between the inlet line and the drain in other states. When the sealing member is in the closed state, the pilot actuator is also considered to be in a closed state.

Conversely, when the sealing member allows fluid passage between the vent port and the drain, the pilot actuator is considered to be in partial or full open state. The sealing member has an area which is exposed to fluid from the vent port when the pilot actuator is closed, and that area is termed the ' Sealing surface' in these specifications. Oftentimes the sealing area would be on one of the faces of the seal.

[0016] When configured in a firefighting system, the pilot actuator vent port is connected via a vent line 20 to the control chamber 30 of the control valve 10. The pilot chamber is in fluid communication with the pilot line or lines 15. The drain 40 is generally at, or close to, ambient atmospheric pressure. When the firefighting system is in standby state, the pilot line, and thus the pilot chamber are pressurized, and the pressure Pp acts on the sensing surface which in turn urges the sealing member to the closed state. Control fluid under pressure Pc is communicated to the vent port from the control valve control chamber 30, and is sealed by the sealing port which cooperate with the seal.

[0017] In most embodiments the pilot pressure Pp in the pilot chamber is lower than the control fluid pressure Pc in the vent line 20, when the pilot actuator is in closed state, the control fluid pressure in the vent line effects a sealed fluid opening force on the sealing member. In order to allow the pilot actuator to affect sealing of the control line from the drain, the sensing surface of the diaphragm is larger than the sealing surface, and thus the diaphragm, sealing member, and seal may act to properly seal the sealing port. The ratio between the area of the sealing surface and the sensing surface is referred to in these specifications as advantage ratio, symbolized by the symbol Ra. In order to provide sealing, the total force imparted by the pilot fluid to the sensing surface must exceed the opposing opening force imparted by the control fluid on the sealing member.

[0018] In these specifications, the state at which the pilot actuator begins its transition from closed to open is referred to as 'drip' state, and the state at which the pilot actuator is fully open, or at least sufficiently open to result in fast and full draining of the control chamber to cause control valve actuation is referred to as 'trip' state. An infinite number of intermediate steps exist between the drip and trip states.

[0019] Pilot actuators are well known in the art. By way of example US Patent Publication No. 20140182865 to Ringer discloses a high liquid to gas trip ratio pilot actuator. Several models of a pilot actuator exist, such as by way of example the Model LP manufactured by the Reliable Automatic Sprinkler Co., Inc. of Elmsford NY, U.S.A., model H-l 1 is supplied by HD Fire Protect PVT. LTD. Of Thane, India, the Series 776 manufactured by Victaulic Co., of Easton PA, U.S.A., and the Tyco (Lansdale PA, U.S.A.) model DP-1 are but few examples. Conceptually, pilot actuators are divided into two main categories, namely direct acting and indirect acting. Generally, both actuator types comprise a chamber exposed to the pressure of the pressurized pilot line or lines. However while in a direct acting type pilot actuator the force exerted by the pilot fluid on the sensing surface is mechanically transferred to act against the force exerted by the control fluid invent line 20 on a seal surface, in indirect type pilot actuators an intermediate fluid chamber is utilized to provide the force required for maintaining the pilot actuator in the closed state. The chamber exposed to the pilot pressure Pp is referred to as pilot chamber in these specifications.

[0020] In US Patent 6,068,067, Beukema describes the state of the art in old type dry -pipe systems utilizing differential valves, as well as the current state of the art in systems utilizing hydraulic valves with direct acting pilot actuators. Beukema's shows that in differential type dry -pipe systems the common pilot pressure setpoint Ppn is between 20 and 50 PSI, However, Beukema touts a hydraulic dry pipe valve with an direct acting pilot actuator having a larger diameter diaphragm which engages a reduced diameter orifice so as to provide a very low air/water pressure trip ratio, thereby permitting a low air pressure in the system, with air/water pressure trip ratio in the range from about 1: 10 to about 1:20 so that the pneumatic pressure required to keep the dry pipe valve closed is in a range from about 5 psi to about 20 psi.

[0021] In US Patent 6,378,616, Reilly describes the current state of the art in systems utilizing hydraulic valves with indirect acting pilot actuators. Reilly 's touts a hydraulic dry pipe valve with an indirect acting pilot actuator having indirect acting diaphragms. These diaphragms effect a constant pilot line trip pressure less than 10 PSI and independent of water supply pressure. Reilly provides yet another example to the prevailing wisdom in the art teaching that it is desirable to operate dry fire control sprinkler systems at as low a system gas pressure as possible to minimize the time required for gas pressure to fall when the system is actuated.

[0022] Thus, in prior art dry -pipe systems utilizing hydraulic valves with direct acting actuators the actuator air-water trip ratio is in the range of about 1 : 10 to about 1 :20. Further, the standby pilot pressure Pp is set to a nominal pilot pressure Ppn at or below 20 PSI, for reason that will be explained below. Following the concept described by Beukema, common wisdom in the art aims for low pilot pressure in dry -pipe distribution systems. And, in prior art dry -pipe systems described by Reilly utilizing hydraulic valves with indirect acting actuators the activation pressure is a constant not more than about 10 PSI, and the standby pilot pressure Pp is set to a nominal pilot pressure Ppn about 20 psi.

[0023] An important consideration in the design of a pilot actuator hydraulic valve firefighting system is the requirement for a nominal pilot set point pressure Ppn that is above the pilot trip pressure R by a sufficient safety margin pressure Ps (Ps = Ppn - Pt) to prevent fluctuations in control chamber pressure Pc or fluctuations in pilot pressure Pp from causing unwanted actuation of the hydraulic valve due to low Ppn. On the other hand, overly high Ps is also undesirable. An overly high Ps will result in delayed hydraulic valve actuation and delayed delivery of fire suppression fluid delivery to the fire. Overly large pressure difference Ps from nominal set pressure Ppn to trip pressure R delays the hydraulic valve actuation endangering life safety and resulting in increased property damage in a real fire event. And in cases where Ps is not sufficiently large the low safety margin pressure Ps commonly results in unintended activations of fire dry pipe systems (both conventional differential types and hydraulic control types). Unintended activations are expensive where personal injury or property water damages result.

[0024] Hydraulic valves are subject to large fluctuations in the control fluid pressure Pc. Such control fluid fluctuations make selection of a safety margin pressure Ps and nominal set point pressure Ppn in the pilot line an important design consideration. The safety margin pressure Ps included in Ppn must be sufficiently high to offset the highest Pc fluctuations to prevent unintended hydraulic valve actuation. Control fluid pressure Pc may vary significantly due to many factors. Water supply pressures vary due to high and low demand periods such as high demand morning shower and lawn sprinkler cycles, low demand early morning times, commercial user periods of high demand, during shutdowns due to piping system maintenance, from water hammer, and for many other reasons. Water hammer is a particularly onerous piping pressure fluctuation and has many causes such as when nearby equipment quickly open or turn off high water demand activities, or merely from common water system operations.

[0025] All dry pipe systems with hydraulic valves are required by NFPA regulation to have a supply line check valve 24 in the control chamber supply piping to retain supply pressure in the control chamber. The supply line check valve retains peak upward water supply pressure fluctuation in the control chamber. Even a Hydraulic valve with low nominal supply pressure (such as NFPA minimum 20 psi) often will have a control chamber pressure of 100, 200, or more PSI due to water supply pressure Pc upward fluctuations. As a result, pilot actuators for hydraulically controlled dry pipe systems must have pilot set pressure Ppn with sufficiently large safety margin Ps to offset reasonably expected water supply pressure fluctuation factors.

[0026] When determining the magnitude of Ps and resulting nominal pilot set point Ppn it is important to consider the slope of the air/water pressure trip ratio of the actuator. A steeper slope Pt/Pc ratio results in a greater difference between Pt at low control chamber pressure Pc and Pt at high control chamber pressure Pc. A pilot actuator with steeper Pt/Pc ratio slope requires a higher safety margin pressure Ps and higher Ppn over the range of control chamber pressures. Pilot actuators with shallower Pt/Pc ratio slope can have a lower safety margin pressure Ps and lower Ppn. This lower safety margin pressure for pilot actuators with shallower slope Pt/Pc ratio can be more than the safety margin pressure Ps for numerous other factors.

[0027] Another important consideration in the design of a pilot actuator triggered firefighting system are fluctuations in the pilot fluid pressure Pp. Pilot fluid is often a gas such as air or nitrogen, and the pilot pressure Pp may vary significantly due to temperature changes alone. Other common factors that cause fluctuations in Pp are compressor on/off cycles and hysteresis in pressure regulators, and minor leaks. Such pilot fluid pressure fluctuations make selection of safety margin pressure Ps and nominal pressure Ppn in the pilot line, an important design consideration. The safety margin pressure included in Ppn must be high enough to compensate for low Pp fluctuations. Failure to have a sufficiently large safety margin pressure margin in the pilot pressure commonly results in unintended activations of fire dry pipe systems which are expensive where personal injury or property water damages result.

[0028] Another important characteristic of direct acting pilot actuators is the pressure interval between the pilot pressure required to place the pilot actuator in drip state at pilot pressure Pd and the pilot pressure required to place the pilot actuator in a trip state at pilot line trip pressure Pt. This interval is referred to as the trip range Pd-Pt. Pilot actuators are further characterized by the full open state at a pilot line pressure Pfo where any further change in pilot line pressure has no incremental effect on pilot actuator opening state. Oftentimes, Pt=Pfo

[0029] It is desired to minimize the trip range since smaller intervals allow faster fire suppression system response to fire detection, and long interval or indecisive transition between closed to trip state may lengthen the firefighting system response time, and in certain cases may even lead to fire protection system failures. [0030] In case of a fire, the sprinkler 55, acting as a fire sensor, drains pilot fluid from the pilot line. The decay rate Dp/Dt of pressure in the pilot line, measured as change in pressure per unit of time such as PSI per minute, is in direct relation to the rate of discharge affected by the sprinkler 55. For a fixed size sprinkler in a pilot line the larger the volume of the pilot system the slower the decay rate Dp/Dt of the pilot pressure. However it is important to note that higher starting pilot pressure results in faster decay rate for any size pilot system. As a sensor orifice drains fluid from the pilot line the pilot pressure is reduced and the force exerted thereby on the sensing surface of the pilot actuator is also reduced, until it falls below the force exerted by the control fluid on the sealing member, and the pilot actuator transitions to an open state. In a simple system the time for opening the pilot actuator may be approximated by

Ta= (Pp - Pt)/(Dp/Dt)

where Ta is the elapsed time from detection of a fire and beginning of venting pressure from the pilot line until the pilot actuator reaches it trip point, and Pt is the pilot line pressure at which the actuator trips, so that the control valve may trip and fire suppressant be freely discharged from the control valve into the primary distribution system piping.

[0031] For a given pilot line volume and sensor orifice size the pilot pressure decay rate Dp/Dt will be faster for a higher pilot line pressure and for a smaller pilot line volume. By way of example figure 9.1 of Underwriters Laboratories Standard 1486 graphically depicts the relationship of pilot system volume and Dp/Dt for a standard orifice sprinkler where smaller volumes have faster Dp/Dt, and higher starting pilot line pressures have higher Dp/Dt. Pilot setpoint pressure Ppn must be set high enough above the drip pilot pressure required to overcome fluctuations in both the pilot Pp and control fluid Pc pressures. However in common pilot systems higher than necessary pilot setpoint pressure causes longer delay between the sensor fire detection and the pilot actuator tripping. The effect of longer delays are amplified when a pilot actuator's trip pressure Pt is low due to lower Dp/Dt. When the pilot actuator trip pressure Pt is below the pilot actuator drip pressure Pd the difference between set pressure Pp and trip pressure Pt must be larger, again resulting in longer time between sensor actuation and control valve actuation.

[0032] Indirect acting dry pilot actuators have large advantage ratios RA, but these type actuators have relatively small clearances and components which are subject to fouling obstruction, which may cause actuation impairments. Generally the common wisdom in the state of the art for direct acting dry pilot actuators for dry pipe firefighting systems calls for advantage ratio Ra between the sealing surface area and the pilot surface area being about 1 :20 or less. The state of the art in present day dry -pipe systems calls for setting the nominal pilot pressure Ppn at a setpoint that is below 20 PSI.

[0033] Early detection can provide a successful way to achieve rapid delivery, and/or can be a method to reduce valve/pipe diameters or operating pressures. Another successful manner to achieve rapid delivery is to adjust the interrelationships of system air pressure and system piping layout design in conjunction with the compressibility of air inside the system piping to accelerate fluid delivery to a fire. In addition to early response, rapid delivery, and minimizing cost, designs that insure improved life safety performance as a result of increased high reliability are of- course also desired.

[0034] It is seen that the design of a fire suppression system presents a complex compromise between the requirements of high reliability, fast actuation, avoidance of nuisance actuation, and reducing costs and complexity. Various organizations invest significant efforts and resources into such optimization. There is therefore an ongoing need for optimizing the design of direct acting pilot actuators and of various components and piping arrangements in fire suppression systems, to provide faster actuation, reduced drip/trip interval, and reduce dependency on pressure fluctuations in the control and pilot fluids.

Summary of the invention

[0035] The special nature of a dry -pipe type systems, driven most prominently by the integration of the distribution system and the pilot line which results in relatively large volume of the system sprinkler piping pilot lines, combined with the demand for mechanical actuation, presents special challenges to the system designer.

[0036] Current wisdom in the art calls for high safety margin pressure Ps as a percent of overall pilot pressure, and low pilot pressure nominal setpoint pressure Ppn. In contrast, the instant invention presents a lower safety margin pressure Ps between the actuator nominal setpoint pressure Ppn and trip pressure Pt as a percent of overall pilot pressure, and higher pilot pressure setpoint Ppn. Those features increases the reliability and speed of operation of the system, and increases its resistance to false tripping. A lower safety margin pressure Ps as a percent of overall pilot pressure and a higher pilot pressure, both allow for smaller percentage in pressure drop to activate the actuator. Furthermore, reducing the gap between the drip point pressure Pd and the trip point pressure Pt offers further reduction in the safety margin pressure Ps, provides faster system response and preserves reliable operation of the hydraulic control valve. The reduced operating range of the trip pressure can also offer higher resistance to pressure fluctuations. In general the above is achieved by different novel combinations of a sealing to sensing area ratio which provides flatter slope and shorter trip difference, a spring to urge the actuator valve to an open state, which biases the pressure operating point towards higher pressures, and piston accelerating surfaces that can reduce the gap between drip point and trip point pressures.

[0037] An aspect of the present invention is directed to providing a pilot actuator that couples the pilot line pressure to the control valve control chamber vent and effects rapid actuation of control chamber venting while also reducing the dependence of the sensing line pressure on fluctuations in control chamber or pilot pressure. Further aspects of the invention relates to arrangements, and parameter settings that will allow fast fire suppression system response time to fire, while minimizing nuisance tripping.

[0038] Aspects of the invention provides large flow paths and component clearances for reduced likelihood of failure to operate, and small differences between pilot actuator drip pressure Pd and pilot actuator trip pressure Pt. Those small differences allow for a sharp transition from pilot actuator closed state to open statei Furthermore, aspects of the invention allow raising the operating point of the pilot pressure, enabling smaller margins of safety in pilot line pressure which increases system actuation speed and improves simplicity of pilot line system design. Additionally, aspects of the present invention provide high resistance to false tripping stemming from low sensitivity to variations of control chamber supply pressure Pc, and mechanical coupling of the pilot sensing pressure to the control vent line seal, which eliminates components and flow path design complexity that can impede actuation. In contrast to present day dry -pipe systems, the invention allows utilizing high pilot pressure setpoint which improves system actuation speed.

[0039] To that end, there is provided a direct acting pilot actuator comprising a housing having an internal cavity, and a pressure sensing member having a sensing surface which at least with a portion of the internal cavity defines a pilot chamber; A pilot port is in fluid communications with the pilot chamber, for allowing connection to a pilot line. A vent port and a drain port are also provided where the vent port is in controllable fluid communication with the drain port via a sealing port. A seat is disposed about the sealing port, the seat comprising a seat face circumscribing the sealing port. A sealing piston is coupled directly or indirectly to the pressure sensing member, and may be integral thereto, the sealing piston having an active end portion movable between a closed state and at least one open state. The seat and the active end form a sealing arrangement therebetween when the piston is in the closed state, for sealing fluid communications between the vent and drain ports. The advantage ratio Ra between the sealing surface area and the pilot surface area being at least about 1:22 and preferably equal or larger than 1:25, 1 :30, and even greater than 1 :50 up to about 1 :95. Optionally the actuator further comprising a spring which imparts to the sealing piston or the pressure sensing member or a combination thereof an opening force greater than or equal to an opposing force which would be imparted to the sensing area by a pressure of 5 psi. The large 1 :22 or higher advantage ratio is particularly advantageous in dry -pipe system due to normally high pilot system volume.

[0040] Operationally, the sealing surface is the surface of the piston exposed to control fluid pressure when the piston is in the closed state.

[0041] In certain embodiments the advantage ratio Ra is at least equal or larger than 1 :25, 1 :30, and in certain embodiments even greater than 1:50 up to about 1 :95.

[0042] Optionally the pressure sensing member comprises a diaphragm, and at least a portion of one side off the diaphragm, comprises the sensing surface. As described above the skilled in the art would recognize that other embodiments, such as a piston or a clapper by way of example, may also be utilized, and such a piston or clapper would have a side exposed to the pilot chamber, and another side acting as a sealing member. The sealing member and the pressure sensing member may be different portions of a single element, or distinct elements coupled directly or indirectly. Stated differently, in embodiments where a diaphragm is utilized, the sensing face is formed on one face of at least a portion of the diaphragm.

[0043] In yet another aspect of the invention there is provided A dry -pipe type firefighting system comprising a control valve having an inlet coupled to a fire suppression fluid supply, and an outlet coupled to a distribution system having a plurality of fluid distribution ports, the control valve having a control chamber for maintaining the system in a standby state when the control chamber is exposed to an operating control pressure, and transitioning to a deployed state in response to reduction of control pressure in the control chamber below a predetermined level. The distribution system is exposed to pilot pressure, and thus acts as a pilot line. At least one of the plurality of fluid distribution ports is a sprinkler capable of venting the pilot pressure upon activation thereof. A direct-acting pilot actuator having a pilot chamber is coupled to the distribution system via a pilot port, the pilot actuator also has a vent port in fluid communications with the control chamber of the control valve, and a drain port. The vent port is in controllable fluid communication with the drain port via a sealing port. The pilot actuator further has a pressure sensing member having a pilot pressure sensing area operatively exposed to the pilot pressure. The pressure sensing member is mechanically coupled - directly or indirectly - to a sealing piston having a sealing area which is operatively exposed to the control pressure when the sealing piston is closed. The ratio between the sealing area and the pilot pressure sensing area is at least 1 :2. This ratio is the advantage ratio Ra. The sealing piston is operative to impede fluid flow between the vent port and the drain when the pilot pressure applies to the pilot pressure sensing area imparts a closing force that is larger than an opening force applied by the control pressure to the sealing area, and allow fluid flow between the vent port and the drain when the opening force is larger than the closing force. [0044] In certain embodiments the advantage ratio Ra between the sealing area and the pilot pressure sensing area being equal or greater than a ratio selected from 1 :22, 1:25, 1 :30, 1 :40, 1 :50, 1 :75, and 1 :85, however preferably the advantage ratio Ra does not exceed 1:95.

[0045] Optionally, the pilot actuator further comprises a spring imparting a spring opening force to the sealing piston, the pressure sensing member, or to a combination thereof, the spring force being greater than a force equivalent to the force imparted to the pressure sensing area of the pressure sensing member by a pilot pressure of 5 PSI, and wherein the opening force comprises the opening force applied by the control pressure to the sealing area and the spring force, while the spring may be implemented in numerous configurations, applying the spring force to various portion of the assembly of the pressure sensing member and the sealing piston, and the spring may apply forces to that assembly at different angles, the spring force is considered the force component which directly acts to oppose the closing force imparted to the sealing member by the pilot pressure operating on the pilot pressure sensing area. This spring force may be applied by one spring or a plurality of springs, imparting force to the pressure sensing member and/or the sealing piston, however the spring force relates to a force equivalent of the forces of the one or more springs which is added to the opening force and operates in parallel thereto. In some embodiments the spring force is greater than an opposing force which would be imparted to the pressure sensing area by a pressure value selected from 10 PSI, 15 PSI, 20 PSI, 30PSI, 40 PSI, 50 PSI, and 75 PSI.

[0046] In certain embodiments the pilot actuator of the dry pipe firefighting system described above comprises a housing having an internal cavity, the pressure sensing member pilot sensing area with at least with a portion of the internal cavity define a pilot chamber. A seat is disposed about the sealing port, the seat comprising a seat face circumscribing the sealing port. The sealing piston has an active end portion movable between a closed state and at least one open state, the seat and the active end form a sealing arrangement therebetween when the piston is in the closed state, for sealing fluid communications between the vent and drain ports. The sealing arrangement defines the sealing area which is exposed to fluid pressure from the sealing port when the piston is in closed state. Optionally the pilot actuator further comprises a spring for imparting the spring opening force to the sealing piston, the pressure sensing member, or to a combination thereof.

[0047] In certain embodiments the sealing piston is integral to the pressure sensing member. The pressure sensing member may be embodied by a diaphragm and at least a portion of one side of the diaphragm comprises the pilot pressure sensing area. Only areas of the pressure sensing member which are capable of transmitting pilot pressure applied thereto to a closing force transmitted to the sealing piston are considered as pilot pressure sensing area.

[0048] Optionally, the pilot actuator further comprises a seat acceleration surface extending from the seal contact area towards the seat edge, and a piston accelerating area disposed at or about the piston active end and extending from the seal contact area to the piston edge. The piston acceleration surface and the seat acceleration surfaces are at least in partial registration when the piston is in the closed state.

[0049] The dry -pipe firefighting system has a pilot pressure setpoint which is set to a pressure at or above a pressure calculated by the sum of a) opening forces acting on the sealing member under the nominal control pressure, and divided by the sensing surface, and b) a safety margin pressure to accommodate fluctuations in control pressure above nominal, and c) a safety margin pressure to accommodate fluctuations in pilot pressure below mean pilot pressure. Elements b) and c) above form together the combined safety margin Ps. In certain embodiments the control pressure safety margin pressure is the difference between the mean pressure and the highest pressure expected to be present in -l ithe control chamber of the control valve. In certain embodiments the pilot pressure safety margin pressure margin is the calculated difference between the mean pilot pressure and the lowest pilot pressure expected to be present in the distribution system/pilot lines without the detection of a fire. The expected control pressure fluctuations and the expected pilot pressure fluctuations may be calculated, arbitrarily set, such as by regulatory, standard, or design requirement, or experimentally determined. Similarly any safety margin pressure may be selected arbitrarily, as a design parameter, as a result of a standard, as mandated by regulatory requirements, and the like. The highest opening forces acting on the sealing member comprise at least the highest force exerted by the control fluid, or a combination of the spring and the highest force exerted by the control fluid, while considering pressure fluctuations, water hammer effects, and the like, and any other opening force exerted on the sealing member during system standby state.

[0050] There is further provided a method of operating a firefighting system, the method comprising of providing dry -pipe type firefighting system as described above; pressurizing the pilot line to a pilot pressure; pressurizing the control chamber to a control pressure, wherein the pilot pressure exerts a sensed force on a pilot pressure sensing surface and the control pressure exerts an opening force on a sealing surface, and wherein the ratio between the sealing surface and the pilot surface is at least 1:22 and preferably equal to or larger than 1 :25, 1:30, and in some embodiments of the invention even greater than 1 :50 up to about 1:95. In some embodiments the actuator further having a spring imparting a force greater than or equal to an opposing force which would be imparted to the sensing area by a pressure of 5 PSI or greater, the spring force urging the pilot actuator towards an open state, and wherein the pilot setpoint pressure is set to a pressure at or above a pressure calculated by the sum of a) opening forces acting on the sealing member under the highest nominal expected control pressure, and divided by the sensing surface, and b) a safety margin pressure margin to accommodate fluctuations in control pressure above nominal, and c) a safety margin pressure to accommodate fluctuations in pilot pressure below mean pilot pressure.

Short description of drawings

[0051] The summary above, and the following detailed description will be better understood in view of the enclosed drawings which depict details of preferred embodiments. It should however be noted that the invention is not limited to the precise arrangement shown in the drawings and that the drawings are provided merely as examples.

[0052] Fig. 1 depicts a simplified diagram of a dry -pipe fire protection system.

[0053] Fig 2A depicts an example actuation graph of a prior art pilot actuator, and Fig. 2B depicts an example actuation diagram of an embodiment of the present invention. Fig. 2C is a graph showing drainage rates of pilot fluid from pilot lines with an open standard sprinkler orifice coupled thereto.

[0054] Fig. 3 depicts a perspective view of an example pilot actuator.

[0055] Fig. 4 depicts a cross-section of a pilot actuator in a closed state.

[0056] Fig. 5 depicts a cross section of the pilot actuator of Fig 4 in an open state.

[0057] Fig. 6 depicts a detail view about the sealing port of a pilot actuator in a closed state.

[0058] Fig. 7 depicts a detail view about the sealing port of a pilot actuator as it begins to open.

[0059] Fig. 8 depicts a detail view about the sealing port of a pilot actuator in an open state. [0060] Figs. 9 and 10 depict a detail view about the sealing port of a pilot actuator using different sealing arrangements.

Detailed Description

[0061] Several aspects and embodiments of the invention are described herein to facilitate understanding of the invention and provide certain details thereof, but the invention is not limited by the example embodiments.

[0062] Fig. 3 depicts a general view of a pilot actuator 100 incorpo rating aspects of the invention. The pilot actuator comprises a housing 110 having body 115 and a cover 120 which cooperate to define an internal cavity 125 (fig. 4). In this embodiment a pilot port 130 disposed on the cover 120. A drain port 135 is visible on the body. A vent port 140 is not visible in Fig 3. It is noted that location of the ports is a matter of design choice.

[0063] Fig. 4 depicts a cross-section of the pilot actuator of Fig. 3 in closed state, and Fig. 5 depicts a cross section of the pilot actuator in an open state. The body and the cover cooperate to define an internal cavity 125. Vent port 140 and drain port 135 are in controllable fluid coupling via sealing port 165 (depicted only in Figs. 5-9 for clarity). A seat 168 is disposed about the sealing port, the seat comprising a seat face 170 circumscribing the sealing port.

[0064] A pressure sensing member, embodied in the present embodiment as a diaphragm 145, divides the cavity 125 and in cooperation with portions of the housing define a pilot chamber 150 within the cavity 125. The pilot chamber is in fluid commumcation with the pilot port. Oftentimes the diaphragm 145 is supported by having portions thereof mounted between the pilot actuator body ! 15 and the cover 120. In some embodiments the diaphragm or another embodiment of the pressure sensing member is supported by lips or other structures. In the context of defining the pilot chamber the term diaphragm relates to any portion thereof exposed to the chamber, and the chamber may be defined by additional structures as well as the body and the pressure sensing member.

[0065] The surface of the diaphragm exposed to the pilot chamber is referred to hereinafter as the 'sensing surface' 155 since it is exposed to the pressure Pp in the sensing pilot line when the firefighting system is operational in standby mode. It is noted however that other embodiments of a pressure sensing member are explicitly considered such as a piston with peripheral seal, a clapper, a gasket with peripheral seal, and the like. However it is noted that only the portion of the diaphragm which when acted upon by the pilot pressure may transfer a force to the sealing member 160 is considered to be included in the pressure sensing surface. There may exist areas of the diaphragm which are exposed to the pilot pressure but do not participate in the force transfer to the sealing member and such portions are excluded from the pilot pressure sensing surface.

[0066] In the depicted embodiment a sealing member 160 is mechanically coupled to the side of the diaphragm opposite the sensing surface. The sealing member is equivalently referred to as a piston. In certain embodiments the piston may comprise the actual opposite side of the pressure sensing member from the sensing surface. By way of example when the pressure sensing member 145 is embodied in a diaphragm with one side being the pressure sensing surface, the opposite side of the diaphragm may act as the piston, and similarly a clapper type pressure sensing member one side of the clapper would act as a sensing surface while the other may act as a sealing surface, or intermediate elements may couple between the sealing surface and the pressure sensing member. In the depicted embodiment a distinct piston 160 element may be observed, and such element may comprise a separate element mechanically coupled directly or indirectly to the pressure sensing member 145, or be embodied in an integral element thereto, such as by being cast together, co-formed, and the like. The piston is moveable between a closed state a plurality of partially open states, and an open state.

[0067] The piston comprises an active end 175 facing the seat face 170. The pilot force, which is the force summing the product of the pilot pressure Pp operating on the pressure sensing surface 155, and the size of the sensing area (by way of example pressure which is measured by Pounds per Square Inch - PSI, and the sensing surface in square inches) urges the sealing member and the active end 175 to the closed state. It is advantageous but not mandatory to arrange the active end such that the pilot force would operate at right angles thereto, to exert force concentric and perpendicular to the sealing port 165. The sealing face comprises a seal 180, commonly made of elastic material such as rubber, Teflon, nitrile, silicon, ethylene propylene diene monomer (EPDM) and the like. The active end 175 is disposed such that when the piston is in the closed state, the seal contacts the seat face 170 at a seal contact area 195. The seal contact area 195 surrounds the sealing port 165 and thus in the closed state the seat face 170 cooperates with the seal 180 to impede fluid flow between the vent port 140 to the drain port 135.

[0068] In some embodiments, the seal 180 comprises a ridge 185 extending from the piston active end 175 towards seat face 170. In some such embodiments the ridge may define the seal contact area, however in certain embodiment the ridge may completely collapse when the pilot actuator is in the closed state, and the seal contact area includes larger portions of the seal, potentially to the edge of the sealing port. In other embodiments, such as depicted by way of example in Fig. 9, the seat face forms a ridge 180A extending from the seat face towards the seal on the piston active end 175. The sealing face in these embodiments may be flat. In certain of these embodiments the ridge may form a line upon first contact with the sealing face on the piston active end and as the ridge reaches the closed state the seal contact area includes larger portions of the sealing face. As described supra the ridge is optional as a whole, and in certain embodiments may alternatively extend from the seat face towards the seal. A plurality of ridges may be utilized. In certain embodiments the seal 180A is disposed on the seat, as shown for example in Fig. 10. Optionally a flat seal may be utilized and the seal ridge may extend from the piston active end (not shown).

Selection of the sealing arrangement may be utilized with all the actuator embodiments disclosed herein.

[0069] The seal portion in contact with the opposite face circumscribes and defines a sealing surface 190 on the piston active end, which is exposed to pressure P _c from the inlet and sealing port when the pilot actuator is in the closed state. The pressure P _c operating on the seal surface results in an opening force, acting to urge the pilot actuator into an open state. The sealing surface may include only the seal, or various portions of the piston active end 175, fasteners 192, intermediate parts, and the like. Stated differently, the area exposed to the pressure present in the sealing port while the piston and the seat are in sealing relationship is the sealing area.

[0070] While the pilot actuator is in standby state the pilot force is mechanically transferred to the piston active end and the seal. The pilot force acts to oppose the opening force, and is greater than the opening force, thus the pilot actuator is closed and no fluid communication exists between the vent port 140 and the drain port 135.

[0071] As commonly the pressure Pp in the pilot line is significantly lower than the pressure Pc operating on the seal surface, advantage is provided by having a sensing surface area larger than the seal surface area. Hereinafter the mechanical advantage is considered as reflecting the ratio Ra between the area exposed to the pressure present in the sealing port when the piston is in the closed state, and the pilot pressure sensing surface area which is capable of transmitting the forces of the pilot pressure to the seal. Notably, higher Ra reduces the slope of the actuation curves of the actuator. [0072] It is noted that in certain embodiments additional mechanical advantage may be deployed between the pilot force as sensed by the pressure sensing surface and the sealing surface. Such mechanical advantage may be accomplished by levers, cams, gears, and the like (not shown). In these specifications however the pilot force is considered as the force directly opposed to the opening force, regardless of any additional mechanical advantage in the transmittal of force imparted on the pressure sensing surface and transmitted to the seal surface.

[0073] In some embodiments a spring 300 is disposed to exert a spring force urging the pilot actuator into an open state. In many embodiments the spring force is parallel and additive to the opening force. Different spring arrangements would be clear, and thus by way of example, the spring may be a compression spring pushing against the sealing member, or a tension spring being pulled by the sealing member, and the like.

[0074] As described supra in many embodiments the spring imparts a force greater than an opposing force which would be exerted on the sensing area by a pressure of at least 5 PSI. Stated differently, a pilot fluid pressure of at least 5 PSI acting in the pilot chamber 150 is required to counter the effect of the opening force imparted by the spring.

[0075] As shown above, the system time for opening the pilot actuator may be approximated by

Ta= (Pp - Pt)/(Dp/DT).

where Ta is the time to actuate the pilot actuator from detection of a fire and beginning of venting pressure from the pilot line, Pp is the instantaneous pilot pressure at the time of fire detection, Pt is the pilot pressure at which the pilot actuator transitions to trip state and Dp/Dt is the rate of pilot pressure decay. In embodiments that contain a spring the spring force is added to the force of the vent line 20 pressure Pc force operating on the sealing surface area, and the actuator trip pressure point Pt raises. This allows higher pilot pressure set point Ppn, which biases the pilot system operating points to a higher pressure. Stated differently the pressure range Pp/Pt lies over higher absolute pressure. Higher pilot pressure causes a faster rate of decay Dp/Dt, however the range Pp/Pt stays constant. Therefore since the denominator Dp/Dt increases, the actuation time Ta decreases.

[0076] Thus the spring raises the trip pressure of the actuator, and the pilot pressure setpoint required to maintain stable operation and avoid false tripping needs to be raised accordingly. Raising both the pilot pressure setpoint and the actuator drip pressure higher causes the operating pressures involved to be higher while maintaining the interval therebetween. As may be seen in Fig. 2C the higher operating pressure offers faster decay rate resulting from fire detection, thus resulting in faster actuation of the firefighting system.

[0077] By way of example, if fluctuations of the pilot pressure and control fluid pressure, and a desired safety margin pressure are symbolized by X, in a firefighting system utilizing actuator without a spring the pilot pressure setpoint would be Ppn = X+Pd. However in a system utilizing a spring which imparts on the closing member a force requiring an opposing force which would be imparted on the pilot pressure sensing area by a pressure of Y PSI, the drip pressure Pd would be increased by Y, and the pilot pressure setpoint would be Ppn=X+Pd+Y. System actuation would require releasing at least X PSI from the pilot line system in order to bring the actuator to at least a drip state. However as seen in Fig. 2C, the decay rate of X PSI is faster when the operating point is higher (by Y pounds provided by the spring force), which in turn results in faster system actuation.

[0078] Figs. 6, 7, and 8 depict an enlarged view of the area about active end region, seal, and seat face, in closed, partially open, and open, respectively. The spring 300 is not shown in those drawings for clarity. Fig. 7 is shown in the drip state which is the state at which the pilot actuator merely begins to open and allow communication between the inlet and drain ports. Figs. 7 and 8 do not include optional fastener 192, and the seal surface is more clearly visible, however the details of the seal construction are a matter of technical choice, and different seal structure may be utilized on each aspect of the invention.

[0079] It is noted that various embodiments of the present invention may combine certain features in varied combinations. Each item of the list below describe by way of example a pilot actuator embodiment which is beneficial by itself, but which may combine with any embodiment described above, and with any combination of listed features:

a. Advantage ratio Ra larger than about 1 :22 and preferably equal to or larger than 1:25, 1 :30, and in some embodiments of the invention even greater than 1:50 up to about 1:95 b. A spring 300 exerting directly or indirectly an opening force to the sealing member 170. In such embodiments the spring force is equal or greater than a countering force imparted on the piton active end by 5 pounds per square inch of the pressure acting on the sensing member 145; c. A piston accelerating surface, potentially in combination with a seal ridge;

d. A piston accelerating surface in combination with a seat accelerating surface, and optionally with a seal ridge.

[0080] Thus by way of example a pilot actuator embodiment is envisioned that will include the features items a. and d above, however varying subsets of above listed features are also considered as varied embodiments, and an embodiment having items a, b, and d is explicitly considered as combining the various advantages offered by the actuator aspect of the invention, and for a firefighting system according to the invention.

[0081] A non-limiting example is provided to demonstrate one method of selecting a pilot pressure setpoint. It is noted that the example is provided merely as guidance and while clearly sufficient for the skilled in the art, other parameters may be exercised.

[0082] In a dry -pipe type firefighting system having a pilot actuator as descried in any of the embodiments described herein, where only the spring and control pressure impart an opening force on the actuator sealing member, the setpoint is calculated as at least

p ₌ ((Pc _m ax . _ p

¹ pn J ^{~ r} pmin ^r pmean ^c

where Ppn is the pilot pressure setpoint, Pcmax is the maximum pressure expected in the control vent line 20 at the seal, Fs being the force applied by the spring, Ac is the area of the sealing member acted upon by the control pressure Pc. As is the pilot pressure sensing surface area, Ppmin is the minimal expected pilot pressure during system standby, and Ppmean is the mean actual pilot pressure, which in many cases is the setpoint pilot pressure. The term (P _pmtn — Ppmean) is directed to the amplitude of downward fluctuation in pilot pressure and the actual pressure is immaterial. In many embodiments a safety factor ε is added to the calculated result, as otherwise the actuator may be left at undetermined state in borderline pressures. Selecting a safety factor ε may be done to comply with an applicable standard, arbitrarily, according to common engineering standards, and the like. [0083] Fig 2A depicts a schematic example actuation graph of a prior art pilot actuator, and Fig. 2B depicts a schematic example actuation diagram of an embodiment of the present invention. The graphs represent smoothed lines and approximated values. In Figs. 2A and 2B the vertical Y axis represents pilot pressure and the horizontal X axis represents control pressure. Graphs TP and TP 1 respectively (represented by dashed lines) represent the trip point at which the actuator is in tripped state, graphs DP and DPI respectively (represented by dash-dot-dot lines) represent the drip pilot pressure, or the point at which the actuator begins to open, and graphs SP and SP1 respectively (represented by solid lines) represent the recommended pilot pressure setpoint, all as a function of the control pressure. As seen in Fig. 2A and 2B generally higher control line pressure Pc in the control vent line 20 requires higher pilot pressure Pp to maintain the valve in closed state. An example of such correlation is shown by lines TP and TP1. It is desired to reduce that dependency, as the pilot pressure set point Ppn must be set higher than a point which will maintain the pilot actuator closed at the highest expected control line pressure Pc. Thus for any given control vent line pressure lower than the highest expected, the pilot pressure set point Ppn is excessive.

Excessive pilot pressure cause longer actuation times. It is therefore advantageous to maintain the slope of such trip, or, reduce the magnitude of the drip characteristics curve as low and close to flat as possible, as doing so allows reducing the nominal pilot pressure setpoint. Examination of Fig. 2B shows that as the shallower slopes of the drip and trip pressures, allow shallower slope of the recommended pilot pressure setpoint Ppn. Notably, the drip-trip interval is also smaller.

[0084] As seen in Fig. 2C the rate of pressure decay Dp/Dt in pilot piping systems is faster at higher pilot pressures.

[0085] It is noted that if the optional spring is not implemented the pilot pressure setpoint calculation becomes:

.Pcmax * A _c )\

rpn J ' ^r pmin ^r pmean and results in a lower pilot pressure setpoint Ppn. As explained above the lower pilot pressure setpoint increases actuation time and reduces reliability. While workable the desirability of the spring in combination with the larger advantage ratio.

[0086] In an aspect of the invention, there is provided a method for configuring a firefighting system in any of the configurations described above which comprises an actuator having a spring imparting an opening force thereto, the method comprising setting the pilot pressure setpoint to a pressure equal to or higher than

p ₌ ((Pc _m ax . _ p

rpn J ' ^r pmin ^r pmean ^c

where the spring force Fs in pounds is equal to or greater than a force exerted on the sensing surface of the pilot actuator by 5 pounds per square inch.

[0087] Additional trim components, such as accelerators, latches, alarm actuators, test and drain devices, and the like may be utilized in any of the systems described herein.

[0088] The term 'line' in this context refers to a length of pipe or pipes, and is commonly referred to as the 'ρϋθί Dry Pipe System Lines' or 'Dry System Branch lines'. These "lines' for a dry pipe system relates primarily to the primary fire suppression fluid distribution system piping, with connecting portions, which when pressurized and acts as pilot piping, also known as pilot line. [0089] This firefighting systems disclosed herein may utilize any type of hydraulically controlled valve 10, such as a diaphragm valve, a clapper type valve, and actuated control valves such actuated gate or butterfly valves, and the like.

[0090] Notably, an actuator having either a seat and/or a piston accelerating face is compatible with any type of firefighting system which may benefit from an accelerator valve. Seat and piston accelerating faces are extended faces disposed about the seat and piston active end respectively and extending away from the seal contact area. The piston 200 and seat 205 accelerating surfaces may be seen by way of example in Figs. 6-10. During the pilot actuator transition from closed to open states fire suppressant fluid pressure acts on one or both of the surfaces, adding an opening force and accelerating the pilot actuator opening. In certain embodiments one or both of the acceleration surfaces are textured to increase resistance to fluid flow at the initial operating stage and thus accelerate the opening. When the actuator is completely open the effect of such texture is negligible.

[0091] Oftentimes, the predetermined levels of pressure at which the control valve and/or the pilot actuator would actuate or prevent actuation, are relative to a respective opposing pressure. By way of example, a diaphragm valve would begin to open when the ratio between the pressure at its inlet reaches a certain predetermined ratio with the pressure in its control chamber. Thus a predetermined pressure in the control chamber required to keep the diaphragm valve closed would be expressed in percentage or ratio of inlet/control chamber pressures. Similarly, a predetermined pressure drop required to transition a pilot actuator from close to open state relates to the interval between the actual pilot pressure prior to actuation, and the pressure required to maintain the actuator closed against the force exerted on the sealing surface by the control fluid at the time of actuation. As both the pilot pressure and the control pressures fluctuate, the term predetermined pressure drop should be construed as directed to a relative term, rather than to an absolute pressure level. Such predetermination is done by selection of area ratio, against nominal set points, as a percentage, and the like of an opposing or cooperating force at the time of operation. Such considerations would be clear to a person skilled in the art in view of the present specifications.

[0092] It is important to note that only the area of the pressure sensing member which is exposed to the pilot chamber and can translate pressure in the pilot chamber to a closing force which is transmitted to the piston is considered as the pressure sensing area.

[0093] Unless otherwise specified, relational terms used in these specifications should be construed to include certain tolerances that the skilled in the art would recognize as providing equivalent functionality. By way of example the term perpendicular is not necessarily limited to 90.0°, but also to any slight variation thereof that the skilled in the art would recognize as providing equivalent functionality for the purposes described for the relevant member or element. Terms such as "about" and "substantially" in the context of configuration relate generally to disposition, location, or configuration that is either exact or sufficiently close to the location, disposition, or configuration of the relevant element to preserve operability of the element within the invention which does not materially modifies the invention. Similarly, unless specifically specified or clear from its context, numerical values should be construed to include certain tolerances that the skilled in the art would recognize as having negligible importance as it does not materially change the operability of the invention.

[0094] In these specifications reference is often made to the accompanying drawings which form a part of the disclosure, and in which are shown by way of illustration and not of limitation, exemplary implementations and embodiments. Further, it should be noted that while the description provides various exemplary embodiments, as described below and as illustrated in the drawings, this disclosure is not limited to the implementations described and illustrated herein, but can extend to other embodiments as would be known or as would become known to those skilled in the art. Reference in the specification to "one embodiment", "this embodiment", "these embodiments", "several embodiments", "selected embodiments" or "some embodiments" means that a particular feature, structure, or characteristic described in connection with the embodiment(s) may be included in one or more implementations, and the appearances of these phrases in various places in the specification are not necessarily all referring to the same embodiment(s). Additionally, in the description, numerous specific details are set forth in order to provide a thorough disclosure, guidance and/or to facilitate understanding of the invention or features thereof. However, it will be apparent to one of ordinary skill in the art that these specific details may not all be needed in each implementation. In certain embodiments, well-known structures, and materials, have not been described in detail, and/or may be illustrated schematically or in block diagram form, so as to not unnecessarily obscure the disclosure.

[0095] For clarity the directional terms such as 'up', 'down', 'left', 'right', and descriptive terms such as 'upper' and 'lower', 'above', 'below', 'sideways', ' inward', 'outward', and the like, are applied according to their ordinary and customary meaning, to describe relative disposition, locations, and orientations of various components. When relating to the drawings, such directional and descriptive terms and words relate to the drawings to which reference is made. Notably, the relative positions are descriptive and relative to the above described orientation and modifying the orientation would not change the disclosed relative structure.

[0096] It will be appreciated that the invention is not limited to what has been described hereinabove merely by way of example, while there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various other embodiments, changes, and modifications may be made therein without departing from the spirit or scope of this invention and that it is, therefore, aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention, for which letters patent is applied.