Reciprocating Compressor Performance – Part 4 – Tuning the Simulation

We’ve started a simulation, ran it and then determined we needed some field analysis to confirm our data.  Our field compressor analysis was performed and we found the discrepancies that were skewing our results from the simulation. Now we can use our field data to fine tune our simulation and start using it for our new reliability tool.

Reciprocating Compressor Performance – Part 3 – Field Analysis

In Parts 1 and 2 we discussed simulating your Reciprocating compressor performance from the computer based simulators available from most compressor manufacturers such as Ariel Corp., Dresser-Rand or G.E. or other programs of this nature. The data required for input, the simulation results and possible problems that may arise were touched on and now we have found ourselves needing to verify some results with field analysis.

Reciprocating Compressor Performance – Part 2 – Simulation Results Now What?

In Part 1 we went through the information we needed to make an accurate model of our compressor for a performance simulation.   Now after all that data is plugged in with all the geometry data, gas analyses and field pressure and temperatures we press the calculate button and… What?  That’s not right, impossible!

Reciprocating Compressor Performance – Part 1 – What are we looking for?

Reciprocating compressor performance can be measured in many ways and is now becoming more of a common activity for engineers to monitor their compression equipment.    So what are we looking for when we want to measure compressor performance in a simulation?

Reciprocating Compressor Vibration – Possible sources and pitfalls

Your analyst team has found a vibration problem with your reciprocating compressor.  Operators are uncomfortable with the vibration, things look scary, “I can see things shaking!”  Now what is the next course of action?

The balance of force and response is the key to keeping vibration levels in check on any piece of machinery, and more so with a reciprocating compressor where there are more complex forces. For vibration to change there must be a change in one of the two factors in the vibration equation.

Vibration= Dynamic Force x Dynamic Flexibility.

Reciprocating Compressor Analysis. The “Cost” of analyzer based analysis.

Seems like an easy target in the Oil and Gas industry here in Alberta, Canada.  Either you are on board with the proven benefits of having a Condition Monitoring program for reciprocating and rotating compressors, or cutting it out of the budget.

The continual battle of having hands on analysis of these assets is being “replaced” (if you can call it that) by remote monitoring programs is more rampant.  On paper, it seems like a cost savings with the ability to “analyze” your machinery at any time with an upload of some field collected pressures and temperatures. Hey, you can have a quick computer generated report come back and say all is good or “blow by” for a confirmation that something may be wrong performance wise.  On an engineering scale, brilliant.. But really is that the big money issue?  How about the risk of some of the mechanical components wearing or failing internally?  Would that be worth the cost of having an actual live analyst taking more in depth data to find and trend?  Seems to me the risk matrix was skewed with the upfront cost of getting each program running and what you are getting in return. The risk and cost of having a mechanical failure would quickly pay for a years worth of hands on analysis.

What makes a good Vibration Analyst these days?

With the recent cost reductions in the market of vibration analyzers and the release of in-house analysts to the market, what makes a good contract analyst these days? In the Reciprocating equipment world, the selection of a good analyst is a daunting task with the different options available out there.

In short, it takes a wide array of skills to make a good analyst.  Some analysts are former mechanics, which is great as you know the internals of most pieces of machinery.  The short fall may be in the theoretical aspect of compression and the properties of compressing gas or vibration and forcing functions.   Others may be representatives of the analyzer manufacturer, which brings many skills in the use and interpretation of the data from the instrument.   Applications may not be as varied here and the sales aspect of getting the instrument sold may steer some analysts focus.

Do what you’ve always done..Get what you’ve always got!

Great quote I’ve heard lately, more about my favorite sports team. But recently working with some clients of ours, I see how this applies to maintenance and reliability programs of today. Recent work with some failed reciprocating compression equipment and talking to maintenance support staff just brought more meaning to this quote.

It seems that anyone in charge of a maintenance or reliability program these days are expecting huge savings from their programs with slashed budgets and reduced work force.   Its hard for me to understand how anyone could ask their maintenance managers to provide better control of repairs and reduced crash maintenance when they are stuck doing the same thing they have done for years.

Articles | Missing a Key Player? The Role of Operations in Reliability Centered Maintenance | ReliabilityWeb.com: A Culture of Reliability

Articles | Missing a Key Player? The Role of Operations in Reliability Centered Maintenance | ReliabilityWeb.com: A Culture of Reliability.

Another great article I just read at ReliabilityWeb.com with more emphasis on the front lines for an effective RCM program.  We have been helping out a client of ours in getting their reliability program off the ground and finding out how much the operations staff is not included in the program is concerning.

Compressor Rod Loads – Whats the limit?

I have been working on and interesting project recently and the primary concern from the analysis results was rod load and rod loading limits.   Quickly using some spreadsheet data and utilizing the pressure data collected we derived that the rod loads for this particular unit were at the manufacturer’s limits for Gas loads only.   No big deal right?  We are just at the limits and we have seen it for years where you can run there for thousands of hours without a problem.

Now the interesting part of the analysis is that from our pressure data, we find the peak internal pressures are well above what any simulator program would estimate and now your instantaneous rod loads are peaking above what the manufacturer provides as, the total rod load or combined limit.  Whats that number for?   Can we use this number to safely limit our machine to not cause a failure?

With accurate reciprocating weights, and reliable pressure data from our compressor end volumes we can calculate the maximum gas rod load and add into the mix the inertia weight of the reciprocating mass.   After we do that we can then apply the combined rod load number to our limits.  Simple right?  Should be, but without accurate weights and good pressure data its still a shot in the dark.  So in a nut shell, gas rod loads are just that, the gas forces on the rod from the act of compression.    Combined rod load or Total rod load take into account the acts of inertia to calculate the combined or total load on the rod.

Fact of the matter is, that without accurate data, you can get mislead into thinking your rod loads are in the limits or are well outside the limits . Getting real time data from the unit, in this case, provided much insight into the actual rod loading being exerted on the machine.  Something that the simulation program or a simple spreadsheet couldn’t estimate.

Jason Hoffman at EMS Inc.