How to address vibration in the outlet pipe of high-pressure coal slurry pumps

Vibration in coal slurry pipes is not a minor issue and requires serious attention. In our company, there was an incident where excessive vibration in the coal slurry pipes over a prolonged period led to cracks in the pipe welds, gas backflow, and ultimately an explosion; fortunately, no one was injured. At present, our company uses segmented welding of supports for reinforcement, which has achieved some effectiveness; however, vibrations still occur. Operators are required to conduct frequent inspections and pay close attention, stopping operations immediately if any signs of pipe rupture are detected.

What the poster mentioned about vibrations occurring at the beginning of material feeding is in line with the characteristics of SLUGFLOW. The cause is that as the material passes through valves, elbows, or junctions of branch pipes, changes in flow rate lead to pressure differences, which cause the vibration frequency to approach the natural frequency of the piping system, resulting in resonance. Solutions: 1. It is recommended to conduct a dynamic stress analysis of the piping system. Ideally, the natural frequency of the system can be altered by adding supports or dampers in order to eliminate resonance. 2. If resonance cannot be eliminated by adding supports and dampers through dynamic stress analysis, considering changing the layout of the pipes could help adjust the natural frequency of the system (since this is a system that is already in operation, this approach is somewhat difficult to implement; it would need to be done during major maintenance). 3. By conducting a dynamic stress analysis of the existing piping system, the natural frequency of the system can be determined. This information can then be used in process calculations to adjust the flow rate so that the natural frequency is different from the vibration frequency (this requires skilled process engineers to carry out the calculations; as I specialize in stress analysis, I’m not very familiar with the process-related calculations. However, this method demands a high level of technical expertise from process engineers, but it results in the fastest response time for eliminating vibrations on-site.) This post was last edited by tseng2008 on 2007-11-6 09:40

In the methods mentioned above, it is easy to determine the natural frequency of the pipe using current finite element software; however, the excitation frequency of the fluid within the pipe is not so easy to determine. To achieve good results, one should consider fluid-structure interaction.

Will it vibrate that much even when it’s running normally? Does it vibrate only when material is fed in?

It does not vibrate during normal operation, but only when material is fed in

We didn’t notice any instantaneous vibration during material feeding, as the personnel had left before we started feeding the materials.

It is also possible to consider installing a resistance valve of appropriate size at some point on the outlet.

A buffer tank is installed in the outlet pipeline of the high-pressure coal slurry pump; this tank is filled with gas at a certain pressure, which serves to cushion the pulse pressure at the outlet of the piston pump. Either too high or too low a pressure can affect the pulse effect and cause vibrations in the outlet pipeline. The pressure in the buffer tank should be slightly lower than the operating pressure in the absence of external pressure.

Most of the high-pressure coal slurry pumps used in many coal slurry plants are 4-chambered; if 6-chambered pumps are used, the vibration at the pump outlet is significantly reduced. As far as I know, Sinopec Nanhua Company produces domestic 6-cavity high-pressure coal slurry pumps, which exhibit low vibration at the pump outlet.

This solution is truly simple and practical

Isn’t there a buffer air bag designed at the outlet of the slurry pump? If the gasifier is pressurized first and then fed with material, can this reduce the vibration of the coal slurry pump during startup?

A buffer tank is installed at the outlet of the high-pressure slurry pump; 70% nitrogen is filled into this tank before starting the pump. This not only ensures stability of the slurry but also minimizes vibrations in the outlet pipelines. In our plant, almost no vibration can be observed in the slurry pipelines. The suggestion on the 13th floor to purge the gasifier before feeding material is not advisable, as there are requirements regarding the pressure in the carbon scrubber during the initialization of the gasifier – it must not exceed 6 kilograms. Moreover, there is absolutely no need for such a step. Last edited by Langtaosha on 2008-10-7 at 13:30

I’m not sure what type of slurry pump the original poster is referring to. If it’s a reciprocating pump such as the Chihao pumps from the Netherlands or the Filowa pumps from Germany, then whether it’s a low-pressure or high-pressure pump, these pumps have buffer tanks at both the inlet and outlet! Moreover, the pressure in the outlet buffer tank can be adjusted. Especially when starting up the pump with low load, there are significant pressure fluctuations; therefore, it’s necessary to check the buffer tanks first! However, generally, the pipes vibrate during startup, but this issue resolves itself once the load increases

Vibration problems are no trivial matter; even the slightest negligence can lead to serious consequences.

As the gentleman on the 15th floor mentioned, it’s unclear whether it’s a GEHO pump from the Netherlands or a FELUWA pump from Germany. In addition to the outlet buffer, the Feluwa pump is equipped with its own piston air compressor. The function of this compressor is to supply a certain amount of compressed air to the buffer (of the upper blind type) during the initial stages of pump operation, when the pressure is lower than the nitrogen filling pressure of the buffer’s air sacs (and thus the buffer does not function). This helps to buffer the slurry pressure and reduces pulsations during operation. I have been using this device for 3 years, and there has been no significant vibration in the pipelines. As for the GEHO pump, since there is no air compressor unit, please refer to the suggestions from above first. :P Last edited by liqiaocun on 2008-10-9 13:42 ]

During the operation of our slurry pump, the inlet pipeline vibrates more than the outlet pipeline, mainly due to the removal of the inlet buffer; by adding more pipeline supports, the vibration is reduced.

The vibration in the outlet pipe of the high-pressure coal slurry pump is severe; this is likely related to the nitrogen pressure in the outlet buffer tank. The purpose of installing an outlet buffer tank is to provide cushioning and prevent vibration. It is recommended to fill it with gas at the appropriate pressure as specified in the manual!

After reading everyone’s opinions and suggestions, the senior on the third floor said something very good; the solution they proposed is quite good. It’s recommended to give it a try and participate! !

It is normal for pipeline vibration to occur when Dutch pumps are in operation at your facility! Because the pressure in your outlet buffer tank remains constant and cannot be adjusted according to the system pressure; moreover, the pressure in the buffer tank serves only as a buffering force at the start of normal operation, and it does not provide proper buffering So vibration at the beginning of driving is normal.