Condition Monitoring/Predictive Maintenance

Maintenance Supervisors should use this tool to train their maintenance techs, welders and contractors - 10-20 minutes - Post them in the Maintenance Shop after use Pipe stress is caused by misalignment of the mating surfaces of two pipe flanges creating abnormal internal stress of pump bearings, seals, motor bearings, couplings, and can possibly change the displacement of a pump. General Rules which must be followed by maintenance personnel and contractors:(if you want to…

Portable instruments have evolved through several iterations to encompass as much data collection, analytical, and correction tools as possible in a single, convenient, and light-weight package.  No matter what, walking (or crawling) from one production machine point to another it is still a dangerous and uncomfortable task in most cases.  What could be better than sitting in an air-conditioned computer room and having instant access to key points on a machine for performing fact-finding, root-cause…

Prioritizing daily tasks is key to successful time management. When you prioritize, you make sure you accomplish the most important tasks first. Make time management a habit, and your stress level (and your boss’s!) will thank you. Follow this process: 1.    Start with a master list. Write down every single task, both mundane and critical, that you need to accomplish. Don’t rank the items at this point. Be sure to include routine duties. Neglecting…

Lubricant Safety While a majority of lubricants (mineral oils) used in a production plant are presently derived from hydrocarbons or synthesized hydrocarbons, the developing trend to increase lubricant performance for specific applications is leading to the increased number of synthetic lubricants. These synthetic lubricants along with all lubricants (oils, greases, pastes, and assembly lubricants) can require special handling and safety precautions that require all individuals involved in lubricant related tasks to read and comprehend the…

A polarization index (PI) test with an index value of greater than 8 may be an indication of heat or age related insulation embrittlement. IEEE-43 suggests for a PI index value greater than 8 to inspect for signs of thermal damage and perform a “Tap test” to see if the insulation has hardened. Hardening of the insulation results in a very slow polarization of the insulation often showing up as a near linear increase in…

Are you ready to buy a blower for a pneumatic conveying system? Look out for the following:

• Is the blower sized for the correct amount of air? Too much air will lead to higher pressure drops and increased power consumption. Too little air will result in line plugging.
• Is the blower and motor sized with enough safety to overcome upset conditions?
• When comparing blowers from various manufacturers, did you look at:
• Reliability
• Efficiency
• Noise
• Maintenance requirements
• If you are conveying food products, you also want to make sure that no particles of the silencer absorption material and no lubrication oil can enter the compressed air stream and thus mix with the conveyed product.

Feel free to comment or contact me to discuss.

Karl Mueller - Industrial Specialist
Aerzen USA
(770) 951-7035
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Sizing - Proper sizing of the blower begins when the buyer provides performance requirements to a blower manufacturer. The buyer should understand the differences between scfm (volumes at standard conditions) and icfm/acfm (volumes at intake or actual conditions).  Knowing the ambient conditions (elevations and temperature ranges) and the required operating pressures which the blower must produce will also effect the manufacturer's selection.

Performance - Only buy Aerzen's blower packages... just kidding, but there is a serious point here.  Any manufacturer's claims of performance need to be verified to insure the correct amount of pressure will be generated for the application.  Insist on knowing the performance and efficiencies (power requirements) of the complete blower package you buy not just the performance of the bare stage.  An undersized drive motor will limit performance.

Package design - Buy a complete package from the manufacturer when possible.  A package assembled by others can consist of mismatched components that could have a negative impact on the blower's performance, and ultimately, its warranty.

Pricing - I put this last, because it is the least important component in the blower selection process.  A decision based solely on a lower up-front capital cost can end up costing much more in the long run when cost of ownership is evaluated and the inappropriate, and possibly, less reliable equipment was selected.

Steve Lungstrum
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 The refinery flare gas can be considered one of the most challenging, but it can be handled with the right compressor.

So how can we compress flare gas from a refinery?

Several types of compressors are being used. 

Centrifugal compressors should not be recommended in refinery flare gas applications because they cannot easily deal with wide swings of mole weight and are sensitive to any solids or liquids entrained by the gas stream. 

Positive displacement machines are best suited for these conditions because they can handle easily wide changes in the composition of the gas.  I know of five types of mechanical compressors being used, more of less successfully in flare gas applications:

• - Sliding vane compressors
• - Liquid ring compressors
• - Reciprocating piston compressors
• - Oil-flooded screw compressors
• - Oil-free screw compressors

Each of these technologies has its place and can be successful when applied correctly. 

A few pros and cons of each of these types of machines:

Sliding vane compressors are simple compressors with a single shaft off-center in a cylindrical housing.  They work best in low pressure clean gas applications.  They are not very reliable when dust or liquid is ingested in the machine and prevent the vanes from sliding back-and-forth in the rotor slots.  Jacket-cooling is required and oil needs to be injected continuously for lubricating the vanes that slide along the housing.  They may require relatively frequent overhauls, but these are relatively easy to handle. Initial costs are low.

Like the sliding vane compressors, the liquid ring compressors are also simple machines. The principle of operation is very similar to that of sliding vane compressors with the exception that a ring of liquid, generally water, is used instead of vanes that slide radially.  Liquid ring compressors are therefore well suited for wet gas,

Buyers have many alternatives when considering which style of compressor is most appropriate for their process requirements. These can include:

1)  Type of compressor:  positive displacement or dynamic

2)  Type of compression:  oil free or oil injected

3)  Construction of compressor:  gastight, hazardous gas or atmosphere, compressor metallurgies, instrumentation, motor type and manufacturer

4)  Operation of compressor:  variable ambient conditions, variable flow and/or pressure requirements, variable properties of the air or gas

Type of compressor is the first and most important selection criteria.  A dynamic compressor will typically provide for small fluctuations in flow and discharge pressure through the use of guide vanes and/or throttle valves.  These compressors operate in-between choke and surge regions and the vanes/valves help the compressor to run at its most optimal point.  With the use of VFD the flow/pressure curve can be shifted on the performance curve to provide some variability.  

These compressors are well suited for applications in which the flow/pressure doesn't vary more than 30%, or the ambient conditions or air/gas composition doesn't exhibit swings of more than 30%.  The positive displacement compressor will provide a relatively constant flow regardless of what the pressure requirement is.  With the use of a VFD this machine can provide for many applications with varying flow and pressure requirements.

The positive displacement is typically simpler than a dynamic compressor since it does not require the use of guide vanes, throttle valves, or sophisticated instrumentation.  Finally, the buyer will need to determine if the compressor will need to be 100% oil free or oil injected.  The oil injected machines can include oil separation and filtration to lower the oil content in the gas down to a few ppm.  Some applications can handle this while others cannot, especially if the downstream oil accumulation over time is detrimental to the process.