Previously RegO was informed of two reports (actually only one) with the 3121 unloading adapter being used to remove product from LPG containers using L7579 Low Emission Filler Valves installed. It was reported that when connecting the 3121 unloading valve to the L7579 filler valve a release of product took place.  This would have been caused when connecting the 3121 (in closed position) the stem made contact with the low emission filler valve seat disc which causes movement of the seat disc without turning the handwheel.

RegO engineering has confirmed that the 3121 unloading adapter does not have an issue regarding the use with low emission filler valve L7579.   

Engineering has found that the 3121 adapter when assembled by RegO requires that the handwheel be rotated in the clockwise (Close) direction and to verify that the stem is flush or ¼" recessed (see photos below). The stem is then rotated counter clockwise (Open) direction to verify that the stem extends a minimum of .875".  Any valve not meeting this assembly process is cause for rejection by RegO.

Operational Note: Failure to ensure that the 3121 unloading valve in in the full closed position (stem not flush or recessed) prior to connection to any filler valve could cause a possible release of product.

Occasionally, marketers have a number of dispenser, pump, and compressor units installed in areas with only single-phase electrical service available.

It is highly recommended to use three-phase motors for these types of pump and compressor installations.  But a number of installations decide to go with single-phase motors and sometimes end up under-sizing or engineering with less than desirable performance capability or they experience a number of operating and performance issues or limitations. 

A statement that is often heard when discussing electric motors to run pumps is,   

"A three-phase motor IS the best solution for pump operation!"  

But, it is seldom explained WHY.  This article will attempt to describe why three-phase motors are much better suited to operate pumps over single-phase motors.

The three-phase AC motor is an induction motor.  It's designed specifically to take advantage of the characteristics of the three-phase voltage that it uses for power.  The figure (below) shows a diagram of three-phase voltage wave compared to a single-phase voltage wave.  From this diagram notice that each of the three phases represents a separately generated voltage.  Recall that the three-phase generator has three separate windings that produce the three voltages slightly out of phase with each other.  The units of measure for this voltage are electrical degrees.  An electrical degree represents one sine wave in 360 degrees.  The sine wave may be produced once during each rotation of the generator's shaft or twice during each generator's shaft rotation.  If the sine wave is produced by one rotation of the generator's shaft, 360 electrical degrees are equal to 360 mechanical degrees.  If the sine wave is produced twice during each shaft's rotation, 360 electrical degrees are equal to 180 mechanical degrees.  Since this can tend to be confusing, all electrical diagrams are presented in terms of 360 electrical degrees being equal to 360 mechanical degrees.  In this way the degrees will be the same and one won't have to try and figure out if electrical or mechanical degrees are being used in the example.

Above: Fig. 1: Diagram of three-phase voltage. Notice the phase shift between each voltage sine wave is 120°.

The first voltage shown in the diagram is called A phase and it's shown starting at 0° and peaking positively at the 90° mark.  It passes through 0 volts again at the 180° mark and peaks negatively at the 270° mark.  After it peaks negatively, it returns to 0 volts at the 360° mark, which is also the 0° point.  The second voltage is called B phase and starts its zero-voltage point 120° later than A phase.  B phase peaks positively, passes through zero voltage, and passes through negative peak voltage as A phase does, except that it's always 120° later than A phase.  That is, B phase is increasing in the positive direction when A phase is passing through its zero voltage at the 180° mark.  The third voltage shown on this diagram is called C phase.  It starts at its zero-voltage point 240° after A phase starts at its zero-voltage point. This puts B phase 120° out of phase with A phase and C phase 120° out of phase with B phase.

The three-phase ac motor takes advantage of this characteristic to provide a rotating magnetic field in its stator and rotor that is very strong because three separate fields rotate 120° out of phase with each other.  Since the magnetic fields are induced from the applied voltage, they will always be 120° out of phase with each other.  Don't worry about the induced magnetic field being 180° out of phase with the voltage that induced it.  At this time this phase difference is not as important as the 120° phase difference between the rotating magnetic fields.  Since the magnetic fields are 120° out of phase with each other and are rotating, one will always be increasing its strength when one of the other phases is losing its strength by passing through the zero-voltage point on its sine wave. That is, the magnetic field produced by all three phases never fully collapses and its average is much stronger than that of a field produced by single-phase voltage.

Now that we have explained why three-phase motors are more efficient and better performers than single-phase motors; how can we use them if our location offers only single-phase service?  There are at least three options:  the use of a static phase converter, a rotary phase converter, and a variable frequency drive/inverter (VFD).

A Marketer should review all the variables when selecting solutions for single-phase service: economics, performance, lifecycle, other costs, and any added issues that will impact a decision on WHICH single-phase service to three-phase motor solution he may select.  A lot of the time, the decision is made based only from the up-front cost economics. 

The BEST scenario for any pump system is using a 3PH motor with 3PH service; period!  Best economics, best performance, best life expectancy!

But, as you modify the application due to limited electrical service you have different costs associated with different options; and an effect on the performance and life of the equipment.

For example the use of a VFD or inverter-driven-electricity might affect the life of a motor (bearings) due to power spikes which can also be affected by the distance from the VFD to the motor (the longer the distance, the greater the exposure).  This does not mean there are not a large number of motors in applications that have performed successfully over a long period of time....it only means it is an exposure, and one that is amplified as the distance is increased based on specific operating and performance characteristics.  This can be mitigated with new generation motors that utilize either shaft-grounding brushes or AEGIS bearing protection rings, both of which have added costs.

The use of a static phase converter requires de-rating a motor's output by 20-30%; but by substituting a larger motor we can provide optimum performance for a specific application.  And, the use of a static converter does not increase the exposure of bearing failure from power spikes like in VFD inverters.  

In an example where we have been using a 5HP motor, by upsizing to a 7.5HP-3PH motor we find it utilizes a 213TC frame and has the same shaft elevation as the 5HP-1PH 215TC motor.  The 5HP-3PH motor is a 184TC frame and has a ¾" shorter shaft center-height than the 5HP-1PH and the 7.5HP-3PH motors.  When selecting a more-economical static phase converter, and up-sizing the motor; as a three-phase motor, the additional costs are very low.

In an example to a specific pump application below, we have identified various scenarios using the LGL156C pump and 5HP-1PH, 5HP-3PH, and 7.5HP-3PH motors with varying electrical service supply.  These are all based on 230VAC service.