I've gotten away from my series on diagnosing pump problems. Hopefully, you've been able to read and digest previous posts. For this post, I'll discuss the issue of low discharge pressure. I look forward to your emails and continued discussion on these topics.
Low discharge pressure can be caused only by loss of flow. Pump discharge pressure is caused ONLY by the system's resistance to the flow provided by the pump. Either the pump is not providing the flow expected, or the system is not offering expected resistance to that flow. It is possible that flow into the pump is being restricted (cavitation or suction starvation). This phenomenon is usually accompanied by noise and vibration. Or, it could be that the pump is not producing its rated flow (pump worn or damaged), or that the pump flow is bypassing rather than being delivered into the system as intended (open, improperly set, damaged or worn discharge system valve). If the pump is relatively new and not being used in abrasive service, it is most probable that discharge flow is bypassing. The most likely paths for such unwanted bypass are the system pressure relief valve (sometimes built into the pump), a bypass pressure regulator leaking (typical of a fuel oil burner system), an inadvertently open bypass valve, or any of these valves having worn valve seats, incompletely closed stems, incorrect signal control or broken springs.
Many pumps can receive a quick, though incomplete, inspection in place without disturbing piping or pump alignment. If the pump does not turn over by hand or with a little leverage assistance and in a smooth manner, the pump itself may be the problem. If one or more of the pumping elements can be visually inspected without major tear down or pump removal, do so. Enough wear to cause a pressure reduction (flow loss) should be readily visible.
It is sometimes difficult to determine if a valve is bypassing when it shouldn't, especially if the valve is built into the pump. It is probably best to remove the valve, do a partial valve dis-assembly and examine the mating valve seat surfaces or seat seals for wear or damage. Check any spring to be sure it is not broken. Work the valve mechanism manually if possibly to detect any binding or galling.
If the problem has still not been identified, be sure the pump river speed is being achieved and that the pump shaft is actually rotating at is correct speed. These conditions must be met, especially in a new system start up.Sean McCandless Industrial Market Manager Colfax Fluid Handling
The Colfax Fluid Handling team was on display at the Power Gen show in Las Vegas. If you attended the show, hopefully you had a chance to come by and say hello. Overall, I thought the show attendance was greater than the 2009 Las Vegas show, but less than the 2010 show in Orlando.
The quality of leads generated at the show was, however, solid and the Colfax team was fortunate to talk with people who -
- Had problems with water in their lubrication Oil (recommend the ThermoJet or PurLube)
- Was interested in pumping sulfuric acid within the environmental system of his plant (recommended the Zenith metering pump)
- Was interested in using a progressing cavity pump in a vertical configuration to save space in his sump (recommended the Allweiler branded progressing cavity or Emtec pump)
- Needed to understand how to size three screw pumps for a fuel oil plant that they were building in the Middle East (recommended the IMO or Allweiler branded three screw pump)
These were only some of the applications that we discussed with show attendees. These leads also show the diversity and flexibility of the Colfax portfolio and the global coverage that we offer our customers.
Finally, we always welcome the opportunity to conduct a lunch and learn seminar for your associates. We offer topics such as the basics of centrifugal vs. positive displacement pumps, design and considerations for lubrication oil systems and three and two screw pumps benefits and design considerations. If you're interested, let me know.Sean McCandless Industrial Market Manager Colfax Fluid Handling
Colfax Engineered Systems was introduced in 2007 and since that time has grown into a valued supplier for multiple markets, including power generation and oil and gas, and a leader in the Custom Engineering solution of Colfax Corporation. Recently, the team at CES completed a fuel system for Mitsubishi Power Systems Americas which marked a significant step forward in their engineering and production capabilities. The team and Colfax are very proud of their accomplishment and certainly most impressive are the comments from our customer -
Colfax provided several value-added benefits that substantially improved the MPSA offering, including assigning an engineer-manager to manage the project. ”We were able to go to him for all technical questions, order updates, quality inspections, etc., which greatly improved the communication and efficiency.” - Tim Shore, Project Manager for MPSA.
I spoke with Ellen Donlin, Colfax Engineered Systems General Manager, about system design and the criteria that she focuses on in her business group to drive value for our customer.
“There are five criteria that I like to focus on and discuss with customers – Speed, Engineering and Design Innovation, Lean Assembly Techniques, Welding and Fabrication Capability and Project Management. I believe that these criterion continue to resonate with our customer base and is what I focus on with my team. The Mitsubishi Power Systems Americas Project is a good example of all five coming together.”
I’ve included a link to a couple slides that display the capability of the CES group, Colfax Engineered Systems Success Stories . To get a true appreciation for the team’s capabilities, please contact Greg Privette or Ellen Donlin.