RODSTAR can automatically design steel or fiberglass rod strings. A context sensitive expert help system warns the user of rods that need slim hole couplings, pump sizes that are too big for the tubing, pumping speeds that are too high, or designs that may result in severe under travel.
RODSTAR includes a large pumping unit data base and is completely menu driven. Although expert users can enter their own designs, taking advantage of the program's expert capabilities minimizes the time and expertise required to design rod pumping systems.
Unlike conventional rod pump system design programs that rely on a trial and error approach, RODSTAR can automatically calculate the strokes per minute (spm), plunger size, and rod siring design to obtain the "target" production entered by the user. RODSTAR can simulate steel or fiberglass rods and any pumping unit geometry including long stroke non-beam pumping units. RODSTAR combines expert rod pumping knowledge with state-of-the-art wave equation and pumping unit modeling algorithms.
Reference: By John Svinos, President E8 LLC ( or ).A "smart" predictive computer simulator of rod pumping systems called RODSTAR has been developed. You may also need to change the pumping speed to maintain the target production (RODSTAR will calculate the SPM you need). counterbalance moment you need to XBAL and see when the counterweights need to be moved to balance the pumping unit after you change the pumping unit stroke length. Keep the same rod string as the one in the well (do not ask RODSTAR to design the rod string) and then run the program to see what the gearbox loading will be when the unit is balanced. Then, at the pumping unit input window try using the next smaller stroke length.
Enter a target production that is a bit higher than the maximum expected production per day and have the program calculate the pumping speed you need. In this case, if the well is pumped off, you may be able to reduce system capacity to better match available production by using a smaller stroke length which reduces gearbox loading. However, if gearbox loading is over 100% and the unit is in good balance then the problem is that the gearbox is too small. balanced counterbalance moment in XBAL to find out where you need to move the counterweights to balance the pumping unit and minimize gearbox loading. If XDIAG shows the gearbox to be overloaded but it’ll be okay if it’s balanced, then you can use the calculated max. counterbalance moment (from XDIAG) or the measured CBE.
This program will allow you to enter both the measured dyno and the measured max. It is also recommended to use a measured dynamometer card and a diagnostic wave equation program such as XDIAG.
counterbalance moment either by running a software program such as XBAL, using counterbalance charts from the pumping unit manufacturer, or by measuring the existing Counterbalance Effect (CBE). To find out if this is the cause of the gearbox overload you need to determine the existing max. The pumping unit may have been designed with the correct size gearbox, but if the existing maximum counterbalance moment is not ideal to keep the unit balanced (which minimizes gearbox loading) then the gearbox can still be overloaded. This is because even if a predictive program (such as RODSTAR) shows the gearbox not overloaded when the well is pumped off, this is typically for a balanced pumping unit (a common assumption when designing new rod pumping systems). The reason may be more difficult to find as compared to structural loading. Pumping unit balancing has no effect on structural loading.Ī short term increase if structural loading can also cause a failure especially in cases where the pump may be sticking due to sand or scale, a seized pump, etc. Peak structural loading is only a function of peak polished rod loading. When simulating the system always use fluid level at the pump (zero fluid level over the pump) to predict the highest possible peak polished rod load which is used in the calculation of structural loading. This can be checked using a rod pumping system design software program such as RODSTAR or SROD. A chronically overloaded pumping unit structure can be due to selection of a pumping unit whose structure rating is below the required rating based on peak polished rod load.
Overloaded pumping unit structure or gearbox, damage due to improper maintenance (gearbox and bearing lubrication), etc.
The following list shows the most common reasons for a failure and how to prevent or minimize its occurrence in the future: 1) Causes of pumping unit failures: However, the right answer may or may not be simple to find. When there is a catastrophic pumping unit failure it is natural to wonder what happened and how this failure could have been prevented.