Theta Enterprises Newsletter - March, 2003
How to Enter Pumping Unit Data in RODSTAR, RODDIAG, or XDIAG
Even though our software comes with a huge pumping unit database of about
4000 units, sometimes you may find a unit in the field that is not in our database.
When the pumping unit you have is not in the program’s database, you have
two options available:
- Use a unit that is close in size and stroke length to the one you have,
- Measure the dimensions of the pumping unit and enter them in the software.
The advantage of the first option is speed. If you can select a unit that is
close to the one you have, the results should be very close to the truth. The
most important item you want to match when you select the first option is the
stroke length. The second most important item to match is the gearbox size,
and the third one is the structural rating of the unit. Just in case you forgot,
the pumping unit API designa-tion is as follows:
Where: X is the unit type, GGG is the gearbox rating in thousands of inch
pounds, TTT is structural rating in hundreds of pounds, and SSS is the maximum
stroke length in inches.
For example, C-320-256-120 is a Conventional unit with a 320,000 in-lb gearbox
capacity, a structural capacity of 25,600 lbs, and a maximum stroke length
of 120 inches.
The disadvantage of the first option is that if you select a unit that is not
geometrically close to the unit you have, the results from the software may
be somewhat inaccurate depending on how different your actual unit is from the
one you selected.
The advantage of the second option is improved accuracy. Since you measure the
dimensions of the unit, you will get accurate results from the software. However,
you must be careful when making these measurements to make sure you measure
the correct dimensions. RODSTAR, RODDIAG and XDIAG provide extensive help on
After you measure the dimensions of your unit, you need to enter them in the
software. You can do this in the setup window. The steps you must follow are:
- Click on the setup icon (fourth one from the left on the tool-bar)
- Click on the “Custom Equip-ment Lists” tab.
- Select “Measured pumping units” as shown here.
- Then click on “New…” to enter the dimensions for your
pumping unit, as shown on the next figure.
- Complete all the fields that you see on this form. If you need help with
an item, press F1 to get help.
- One of the items you need to enter is articulating moment of inertia. This
is a value you cannot measure, but there is a way around this. If you don’t
know what the articulating moment of inertia is, leave it blank as first.
Then, after you enter all the other pumping unit dimensions, click “OK”
to exit Setup and save the dimensions you entered. Then, load a file into
the program (it does not matter which file), go to the pumping unit input
window and select a pumping unit that is as close as possible in size as the
one you entered dimensions for in setup.
- Go to the Motor Information window and select to include motor speed variation.
This will activate the rest of the options in that window, and the Articulating
moment of inertia for the unit you selected will appear at the bottom right
hand corner of the motor information window. Double-click in this input field
to highlight the value of the articulating moment of inertia. Then, right-click
on it and select “Copy.” Next, click on the setup icon, select
the “Custom Equipment Lists” tab, and select “Measured Pumping
Units.” Then click on the unit you entered data for previously, and
click on the “Modify” button.
Then, right-click in the “Articulating Inertia” input field, and
select “Paste.” This will copy the articulating moment of inertia
value in the input field. Then, click on the “OK” button to exit
the window and save the data.
Figure 2. Pumping