Opti-Valve uses one or more sensors to operate a "snap action" electric solenoid valve to cause a controlled flow through the pump during churn conditions. Sensors that start and stop the flow are available for pressure, temperature and motor current.
The Opti-Valve Casing Relief System is a pre-engineered set of components that addresses each of the shortcomings of the present state of the art. To develop an improved solution to the fluid overheating problem the following issues were considered:
- Reliable. Fluid must flow in the bypass when the pump is churning hot fluid and not at any other time.
- Predictability. During system upset the relief valve must revert to a known condition, either open or closed, depending on application.
- Flexible. Present designs require the placement of the components and piping in fixed locations, due to mechanical constraints separating the detection and valve operations, it becomes possible to locate the mechanical valve where it would work best, even on the high-pressure side of the discharge check valve. Separate devices, which can be installed where most appropriate, monitor pump operation.
- Modularity. Each system is a package of pre-engineered, proven parts assembled specifically for a particular pump application.
- Independence. The system should be self-contained and not rely on other systems or components. It includes its own backup power source, if required.
- User Friendliness. The system must be building code compliant, safe, and easy to set-up and troubleshoot.
- Simplicity. No special tooling, or skilled labor to install.
All Opti-Valve Systems use these four components:
- a valve or orifice to determine the volume of fluid to flow,
- a “snap action” valve to turn the fluid on and off,
- a sensor device to detect the churning pump, and
- a means to allow the sensor to operate the snap action valve.
The volume control is achieved with a gate valve or a pipe union with an internal orifice plate located next to the pump. The snap action valve is a “piloted diaphragm electric solenoid” device available in either a “normally open” or “normally closed” configuration. Three sensor devices have been identified for pressure, temperature, and motor current. These sensors complete a circuit allowing current to flow through the solenoid valve coil from a power source. An energy limited, low voltage transformer or a battery pack with internal charger provide the operating power.
To provide for the number of possible combinations of valves, sensors, and power options, as well as to make it both user friendly and easy to install, a modular kit approach is used.
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1) Power Pack --It reduces incoming voltage and provides electrical isolation between the valve control circuit and facility power. Three different power packs are available
- a small modular plug-in the wall unit (Shown at right) similar to those used for calculators and some computer peripheral equipment,
- a small metal box with “knock outs” in the bottom designed for fixed mounting to a wall or similar location with permanent power wiring,
- a metal enclosure containing a small sealed lead acid battery and battery charger which is also intended for permanent power connection.
The modular power pack plugs into any vertically installed standard three-prong grounded duplex wall outlet. Both prefabricated cables (from the valve itself and the sensor) connect at the power pack. Operating below 24 VAC and supplied by a listed, labeled “class 2” energy limited transformer interconnecting wiring would not be required to be installed in EMT conduit. The transformer itself is rated 20 watts, 550 ma, 22 VAC when connected to a 120 VAC, 60 Hz. sources. Due to the typical wet environment in most pump rooms a Thomas & Betts “Code Keeper Wet Location Cover” is supplied to enclose the duplex outlet into which the transformer is installed.
The fixed mounting power pack supplies approximately the same electrical characteristics as the modular unit with internal connections. The fixed mounting power pack is comprised of a class 2 transformer rated at 20 VA, 24 VAC, 50/60 Hz. It is mounted in an enclosure that is galvanized and rainproof with a “NEMA 3R” rating.
The battery pack consists of a 15 Ah (amp-hour) maintenance-free rechargeable battery and a battery charger. The battery charger operates from 120 VAC, 0.5 amps 60 Hz. power source and supplies up to 2 amps at 12 VDC to the battery. An automatic float mode feature is included.
The battery pack is intended for mounting on a vertical surface with the incoming 120 VAC power supply connected directly to the battery charger input. The sealed lead acid battery is connected directly to the battery charger output. Rated at 15 Amp-Hours a fully charged 12 VDC battery can hold the solenoid of a normally open valve in the no-flow position for 24 hours.
2) Volume Control -- The Volume Control divice is placed between the pump discharge piping and ahead of the solenoid valve. Control is achieved using either a pipe union with internal orifice (which has a hole drilled to the required size) or a gate valve (which is adjusted to flow the required amount of water during churn conditions).
The second device (A “restrictive orifice union.”) is a device that can be separated into two parts, each of which is mounted on opposing pieces of pipe. A threaded coupling collar slides over one side of the union and engages threads on the opposite side, drawing the halves together. The two faces, drawn together, are machined with groves to accommodate o-ring seals and seal against each other.
A restrictive orifice union, is a pipe union that has a metal disc between the two faces. A hole is drilled in the center of the disc. The size of the hole, fluid characteristics, and the operating pressure determine the amount of fluid that will flow through the orifice plate.
As an alternative, a gate valve may be installed upstream of the solenoid valve toward the pump itself. The design of the gate valve is such that wide adjustments in volume can be made. The selected valves have “spoked” handles allowing a plastic strap to be laced through the handle, and around the pipe and cinched tight to prevent adjustment.
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Two types of solenoid valves are offered. The normally open valve flows fluid when the coil is de-energized, while the normally closed valve will flow fluid when the coil is energized. To decide which one to use the question to be answered is “What should happen when the power fails?” Should fluid flow or not?
The solenoid valve used is a piloted diaphragm operated device; the electric solenoid itself controls the pressure over or under a diaphragm, which in turn operates the main valve mechanism. The electric coil used operates on nominal 24 VAC or 12 VDC and dissipates 5 watts.
The flow control device and solenoid valves are located within 6 inches of each other. Turbulence created by the gate in the flow valve or orifice plate keeps any entrained solids agitated. This self-cleaning prevents interference with proper solenoid valve operation.
Back to Top4) Sensors -- The electric solenoid valve opens or closes when a circuit is completed between the power pack and the solenoid's coil. The various sensors are used as switches to complete the circuit between the power pack and the solenoid valve coil. The amount of power switched is small, 5 watts at 22 VAC. Several sensing devices have been identified which respond to pump operating characteristics. Sensors for pressure, temperature, and motor current are available. Each determines when a particular parameter (say, motor current) has changed to indicate a no-flow condition or hot fluid. Some sensors are metallic contacts while others use solid-state switches.
The temperature sensor is a switch fixed to operate at a nominal 140 degrees F. (60 deg. C) similar to the discharge temperature of a residential water heater. Its temperature differential is fixed at 15 degrees F. In appearance it resembles a large bolt with an electrical connector built into the top. It is installed by threading the “mechanical end” into a tapped hole in the side of the pump volute provided for this purpose. The temperature sensor must be in contact with the fluid at or very close to the actual point at which the heat is being generated. To operate properly it must not be insulated by being installed too far from the pump's impeller. A prefabricated cable can then be attached at the electrical end and connected at the power pack.
The pressure sensor is also a switch which provides metallic contact closures to operate the solenoid valve. The pressure sensor is, however, adjustable as to its trip and reset points. It can be installed at any point in the piping that is connected directly to the pump's discharge (no check valves, etc. between). The sensor is mechanically mounted through a tapped hole in the piping, using a short piece of small diameter pipe. The prefabricated cable is connected to terminals inside the sensor and to the power pack.
The pressure sensor must be adjusted to the particular installation. The key to proper operation of the pressure sensor is a constant pump inlet pressure. Constant inlet pressure will result in a constant discharge pressure. If the inlet pressure is able to change, the settings must allow for the lowest discharge pressure from the pump or the valve may not open. Adjust the operating point while the pump is running.
The motor current sensor is a solid state electronics module, which is usually installed within the motor control center. A three-conductor cable serves to connect the output of the power pack to the motor current sensor. Motor current flow is detected by means of a “current transformer”. This device is used to detect the magnetic field which exists about any current carrying conductor. It is installed by disconnecting one motor current lead, passing it through the center of the transformer and re-connecting to its original location.
The module tests for two conditions 1) the motor current is high enough to assure the motor is running and 2) motor current is low enough to indicate no fluid movement. When both conditions 1 & 2 above are met, a logical “and” gate function activates the output, which in turn operates the solenoid valve.
As with the pressure sensor the motor current sensor must be adjusted to the individual application. Once mounted and connected the sensor is set for its highest input current. The pump is started under churn conditions and the sensor is then adjusted until the valve opens and flow begins.
Back to TopA final method to control the operation of the solenoid valve is to use a flow switch, and directly monitor fluid flow. These switches in essence consist of a switch and a “paddle” which is inserted into the pipe through a hole in the side of the pipe. At a given flow the paddle will deflect to a point of switch operation.
From a design standpoint, the flow switch cannot distinguish between a no flow condition caused by a closed valve and one caused by stopped pump. For the solenoid valve to operate properly, a modification must be made to the pump motor controller to access a “motor running” auxiliary contact to be wired into the circuit. Because of the differences between the many motor controller suppliers no standardized package could be developed for customer installation.
Additionally the correct flow switch selection must account for factors such as pipe diameter, minimum required flow rate, fluid type, and system pressure. Installation requires drilling a relatively large hole in pressurized piping and “saddle strapping” a liquid tight switch mounting to the pipe. The possible number of combinations coupled with the assistance required for each customer made this an impractical control method.
Back to TopTo assemble an Opti-Valve package several questions must be answered:
- How much fluid needs to be bypassed? A ¾ inch valve can flow up to 40 GPM, while a 1-inch flows 60 GPM.
- Is the power source for the pump the same as the Opti-Valve? In other words can the pump run without power to the Opti-Valve? If so, do you want back-up battery power?
- If power to the Opti-Valve does fail should the valve open or close?
- How will the volume of fluid be regulated? Should volume be adjustable?
- How shall no-flow condition be detected?
- Does fluid temperature change?
Pressure -- Pressure is the classic means to operate a casing relief valve. Pressure sensors are available in various ratings, the most common being the 40-240 PSI water service that has a minimum deadband of approximately 12 PSI. This sensor requires the pump pressure to drop 12 PSI below the trip pressure before the sensor resets. Remember that changes in inlet pressure can cause the valve to malfunction. Also, some centrifugal pumps develop somewhat higher pressures during low flow than at churn, therefore pressure sensors are not recommended in this case. In general, the faster the pump curve falls off from churn pressure, the better.
Temperature -- Because the effect of operating a pump at no-flow is to increase the temperature of the fluid, detecting the fluid's temperature allows bypass only when the fluid is hot -- and then only long enough to cool the fluid to the reset temperature. Flow stops until the temperature rises again. The temperature sensor is mounted through a threaded opening somewhere on or near the pump and is immersed in fluid. It activates at 140 degrees F. and has a deadband of 10 degrees F. If the fluid is hot entering the pump, the bypass may open. The flow control device should be adjusted to prevent too rapid cycling of the solenoid valve.Motor current -- Motor current is a reliable indicator of flow. The minimum motor current, approximately 50 to 60 percent of the motor’s “full load current,” occurs when the pump is not actually moving fluid. While it is adjusted to the particular application, the sensor’s operation is not subject to errors caused by pressure changes or hot fluid. The motor current sensor uses a “current transformer” (it looks like a doughnut) around one of the motor leads in the pump control. The current transformer signal is compared to the adjustment points set at installation and the valve is operated as necessary. Since the current rises as flow increases, minimum current occurs when the pump is at or near zero flow. The solenoid valve closes if motor current rises by more than 10 percent. When the motor current drops below churn level, the valve re-opens.
The current sensor is powered by the power pack and is usually mounted within the pump’s motor control center. No electrical connections are made to the motor controller itself.
