“Smart” Meters by the Pair

A proven technology just got better. The iMeter Module, the latest model of Dresser Wayne’s hydraulic metering systems for dispensers, combines both the beauty of duplex housing and the brains of “intelligent” pulsers. Join Joe Totten for a tour of the new technology.

iMeter Module - Remote System

How often have you heard the admonition “If it ain’t broke, don’t fix it”? Frequently, that stance is taken by those who, for good or bad reasons, are dead set against proposed changes in the way things are done. Such a posture may be a valid and understandable reaction to change just for the sake of change. But, the fact that something is working well does not mean that it cannot be improved.

The interests of advancing technology are better served by the more positive attitude toward change: “There’s always a better way.” This attitude underlies one of the key principles in modern-day quality management theory: Make continuous efforts to improve your products and services.

Such must have been the attitude of Dresser Wayne when the company set out in 1995 to see how its already-proven and popular dispenser technology could be made even better. As a result, the long-standing “unbroken” technology of hydraulic metering systems in gasoline dispensers is about to be improved significantly.

The new technology is dubbed the “iMeter module.” It is slated to be integrated into Dresser Wayne’s main Vista pump and dispenser product line beginning in the first quarter of this year, and into its smaller Global Century line beginning mid-year. This means that the iMeter module will soon be in every new Dresser Wayne dispenser worldwide.

Gasoline meter technology 101
Before elaborating on how the iMeter technology is different and better, let’s get a fix on the basics: When a service station customer refuels a car, the volume is metered and the total cost of the amount dispensed is calculated and displayed on a digital readout on the face of the dispenser. The customer pays the amount displayed, perhaps a little perturbed at the price, but with little or no worry about the accuracy of the measurement and calculation. This scene is replayed millions of times daily.

The equipment and technology at work behind the scene include a hydraulic meter, a “pulser,” a computer, and a display. All of these work together to measure the volume of liquid, calculate its price and communicate the data to the customer, POS workstations and other interfacing data-processing components.

The data is used not only to determine what the consumer pays for the fuel, but also for such management functions as inventory monitoring, purchasing and receiving, leak detection, accounting and tax administration.

The general reliance on metering system integrity is based on time-proven accuracy and reliability of the equipment, which is under vigilance by weights-and-measures regulatory officials (see “Controlling Dispenser and Meter Accuracy” by F. Michael Belue in the April 1998 issue of PE&T).

So, given such widespread acceptance and success of the existing metering technology, what’s with the new iMeter module?

Building a better meter
The new technology employed in the iMeter module provides significant benefits in the following areas:

• improved flow rate performance
• increased accuracy
• easier and more accurate calibration
• simpler access
• reduced leak potential
• greater reliability
• lower initial and operating costs

The main features of the new module, which allow these improvements to take place, include: (1) duplex housing (two meters in one casting); (2) simplified direct flow path; (3) global “all model” design; (4) absence of external dynamic seals; (5) increased internal meter volume; (6) increased number of pulse outputs to computer; (7) built-in pulser intelligence and data storage; and (8) vertically-oriented strainer/filler casting. Let’s compare these to Dresser Wayne’s pre-existing technology.

One housing, two meters
The iMeter module is, basically, a repackaging of Dresser Wayne’s existing 2PM meter system, first introduced in the mid 1950s. In virtually all of the company’s dispenser designs, the 2PM meters are used in pairs. “So,” asked the engineers, “why not build two meters into a single housing?”

Such a duplex design, some said, would mean that if one meter were to fail, the other would also be dysfunctional; two hoses would be out of service and the entire duplex module would have to be replaced. While accepting this as a valid observation, the engineers felt that, in light of past experience and recent improvements in tank systems, the minimal number of meter failures would allow the risk to fall well within an acceptable range.

Placing two meters into one housing allows for a more compact, modular product with flexibility in layout configurations and easier assembly, retrofit and servicing. This development also allows for the same duplex design to be used to house the pulsers (discussed later) and follows along with the design already in the duplex computer, used in Wayne dispensers since 1986. These duplex arrangements reduce the number of needed components, such as power supplies, circuit boards and wire connectors.

iMeter Module - Suction System

Same old meter, only better
The meters in the iMeter module use the same piston-driven positive displacement technology as the Wayne 2PM meter. However, the iMeter technology is different in the following major ways:

• duplex instead of single housing
• in-line pistons (rather than placement at 120-degree angles)
• modified crankshaft timing (to maintain the same flow dynamics as the 2PM meter)
• integrated meter valve seats into the casting
• absence of external shaft seals
• reduction in the number of internal seals
• increased internal volume (by five percent)

The iMeter module has a single inlet passage that runs through the meter body to a single meter dome casting, which is divided for measurement to either side of the module. Each passage has a check-pressure relief valve. Top access to these valves allows inspection without draining the body and, thereby, reduces the chance for an accidental release of product.

In remote dispensers, the inlet filter/strainer casting is at the bottom of the iMeter module. The filter is positioned vertically to avoid spilling product when it is removed. Also, the filter/strainer casting is designed to accept either standard fuel filters or high-flow filters, using an adapter ring installed at the factory or in the field.

The iMeter has no external moving parts. No piping or functional assemblies are needed between the product inlet and outlet to the flow control valves on the iMeter discharge ports. Calibration is done electronically. All of this simplifies installation and service and minimizes the opportunity for leaks.

Pulser with an IQ
The brains of the iMeter module are its “intelligent” pulsers which, in themselves, represent two significant advancements in meter technology. First, they feature the Hall effect (magnetic) sensor technology, which is similar to that used on anti-lock brake systems on automobiles. Second, intelligent pulsers not only communicate flow volume signals to the dispenser’s computer component, but have their own microprocessors.

The Hall effect sensor technology replaces the slotted disk and infrared photocell pulser that was used with the Wayne 2PM meter. This modification improved the pulser’s resolution, and thus its accuracy, by increasing the number of pulses per gallon by 40 percent, quite a feat in view of the exemplary reputation of the replaced technology.

Redesign of the pulser provides an opportunity to use the latest advances in material processes to develop a nylon-based disk, which could be “in-mold” magnetized to ensure consistent performance in a harsh environment.

The microprocessors (explained later) provide the means for electronic meter calibration, with the capability to store calibration factors, performance data, audit trail information, high-speed data communications and future remote diagnostics. These microprocessors also provide the potential for self-calibration, using empirical (actual) performance characteristics. Further, because the intelligence resides with the pulser, the stored information is not lost with the replacement of the dispenser computer.

To complement the arrangement of the iMeters, the intelligent pulsers are packaged in a duplex, two-in-one assembly—one for each meter. This duplex meter-pulser module interfaces to a standard duplex computer through a modified version of the intrinsically safe barrier, which separates the electrical sources of ignition from fuel-handling components.

How it all works together
During the dispensing process, fuel enters the iMeter module’s single inlet passage and passes through the meter body to the single meter dome. Here, the fuel flows to either side of the meter, each of which is equipped with a check valve with integrated pressure relief. Each side of the iMeter module works, in effect, as a three-cylinder motor: the two meter cylinders plus the center chamber. Because the filling and discharging ports in the valve are oriented 180 degrees apart and the port openings in the valve seat are radially oriented 120 degrees from each other, there is no dead-center position in the meter.

Filling the meter is continuous: Before one chamber is completely filled, the next one is starting to fill. The same applies to the discharging operation. The filling and discharging operations each occupy 180 degrees of crankshaft rotation. Flow measurement is determined by (1) the known quantity represented by the displacement of each cylinder, together with the displacement from the center chamber; and (2) the direct and substantially constant relationship between the flow and the crankshaft rotation.

Inside the meter dome, a rotating magnetized disk generates a changing magnetic field. The Hall effect sensors, located outside the meter housing in the pulser, convert changes in the magnetic field into digital pulses. The actual pulse count is modified by the intelligent pulser’s calibration factor (the amount that the computer adds or subtract to ensure the accuracy of the measurement) before it is sent to the computer. Because the intelligent pulser contains its own processor and memory, it can store totalization values, calibration factors, error codes and other diagnostic information.

Each side of the iMeter module is capable of simultaneously delivering about 15 gallons (approximately 57 liters) per minute. The unit of measure for the intelligent pulser is set at the factory to either US gallons or liters. Once the unit of measure is set, it is stored in the pulser’s computer chip.

iMeter Module - Three Product Dispenser

Logical calibration
Calibration of the iMeter is done electronically through the intelligent pulser. Calibration logic in the pulser software counts the incoming pulses and compares them to a stored calibration factor. Before initial calibration of the meter, there is no pulse count correction.

The intelligent pulser enters the calibration mode by opening a calibration door. Once in the calibration mode, a five-gallon test measure is filled (assuming a US gallon is the chosen unit of measure). At exactly five gallons, the calibration door is closed. The pulser then has the information to calculate a calibration factor according to an established equation.

For security, each calibration door on the intelligent pulser is sealed just as with the calibration knob and stem on the 2PM meter. A seal wire passes through an opening in the door and through a flange on the meter assembly, which can then be sealed by an authorized representative. If the calibration door is left open, the dispenser will shut down immediately after the normal test filling range (five gallons or 20 liters) is reached.

X-ray vision for trouble shooting?
Since the iMeter module has no visible moving parts, people cannot use the traditional method of “eye-balling” gear rotation and other external clues to determine hydraulic function. Therefore, Dresser Wayne has developed a diagnostic tool that service technicians can use to “look inside” the meter. This tool is held close to the iMeter dome, where it can tell the rotational direction and relative speed of the magnetic poles of the rotating disk. Such diagnostic information is in addition to the pre-programmed information and computer fault codes, which are the first things checked when troubleshooting.

Speaking of trouble, the presence of metal flakes or ferrous materials in fuel storage systems would suggest a potential effect upon the magnetic disk and the intelligent pulser. In fact, they are affected, but in a positive rather than negative way because the flakes increase the magnets’ field strength and enhance the intelligent pulser’s sensitivity.

Looking ahead
While not integrated into today’s package, Dresser Wayne has designed the iMeter module so that remote diagnostics can be part of future designs. Every casting has pads located at key points in the hydraulic path for the eventual purpose of housing or mounting dynamic sensors that would provide real-time information on flow rates, line pressures, differential pressures, temperature and other data. Each intelligent pulser provides the capability of storing and communicating these key parameters to a POS or to a back office control system for valuable remote diagnostic capability.

Another potential for the future is meter self-calibration, based on empirical performance characteristics. Such calibration would be independent of any testing or personal intervention and, thus, would save downtime and money. It also has the potential to provide greater accuracy—zero errors across the whole range of flow rates—compared to typical accuracy curves. Self-calibration will, of course, require major changes in weights-and-measures regulations. Making the appropriate changes take time and evidence showing that the public interest remains protected.

There is yet another futuristic feature. Additional pads on each casting allow for the future application of service plugs. These plugs could be used to drain product from the entire iMeter module without any disassembly.

Flow control and vapor recovery
Along with the new iMeter technology has come new flow control valve technology to replace the Dresser Wayne two-stage diaphragm valve design. The new technology is an extended sleeve design, with the valve body and coil separated by the dispenser vapor barrier. The valve body remains in the hydraulic cabinet and the coil resides in the head. There is a two-stage extended sleeve version for non-blending dispensers and a proportional extended sleeve version for blending dispensers. The extended sleeve technology is the same technology used in the Vista blending dispenser.

The main advantage of separating the valve body from the coil is that it allows the iMeter module to be identical for all dispensers, whether they are blending or non-blending dispensers. It also moves the flow control valve up and out of the way in the hydraulics cabinet, opening up space and improving access.

The vapor recovery system on the new iMeter dispensers is functionally the same as the standard Vista models, with modifications for higher pulse resolution of the intelligent pulser.

Changes not for change sake
Dresser Wayne did not set out to change its hydraulic meter technology because something was broken. Neither were changes pursued simply because none had been made for some 40 years; nor, because the company had engineers with time on their hands. The effort did not result in “new technology looking for a job” or “solutions looking for things to fix.”

Dresser Wayne understands the international requirements for fuel handling, measuring and dispensing. Add to this the company’s recognition that world-class equipment suppliers do not remain world-class without challenging tradition and seeking innovative improvements, even for successful products. Management literature is full of case studies of failed companies that were committed neither to understanding their customers, nor to making continuous efforts to improve. Dresser Wayne’s new meter design efforts seem to be is a classic example of the other kind of case.

Discuss