jharris3
Mechanical
- May 3, 2011
- 52
I'm not sure if someone has addressed this issue already in a previous posting so please let me know if that is the case. Here are the details of the pumps followed by my questions
Three triplex pumps in parallel with each other discharge to a pipeline. The pumped fluid is from the brine and fast rinse cycles of a water softening plant and the brine is mixed using oilfield produced water. A separate source of filtered produced water is pumped by centrifugal pumps where both flows are being transported through the pipeline to disposal. The resulting system provides a variation of backpressure to the triplex pumps of between 800 and 1200 psi. The discharge piping is full port except for some glove valve style piston check valves. The two different pump system discharges tie-together far away from either of the pump batteries.
The triplex pumps have a seal flush of fresh water, a suction pulsation dampener, and a discharge pulsation dampener. The suction is 6" and the discharge 3"x4". The source for the brine is pumped through some filters and a pressure control valve upstream of the filters maintains a set pressure above the suction pressure requirements of the triplex pumps plus the dirty filter pressure drop. The pumps are mounted on steel blocks and a steel frame together with the gear box and motor. The steel is W shape I-beam 12" deep, anchored and grouted to the foundation.
The triplex pumps are 3.25" dia pistons with 5" stroke and the pumps are operated at between 100 and 400 rpm on an adjustable speed drive. The pulsation dampeners both have an opening equal to the respective pipe diameter and appear to be the correct volume. We have checked the charge on the suction and discharge and it appears to be the correct charge. We checked the bladders and they are holding.
The problems:
-At certain speeds the discharge pulsation dampener will vibrate (wobble) more than is typical but the suction dampener is barely moving at all; and then at other speeds the opposite is true. This is independent of whether 1 pump or 2 or 3 pumps are running together. Also, the sound around the pumps is not abnormal and the pumps are running smoothly.
-at any speed including when the dampeners are NOT wobbling and the pumps sound smooth then the vibration at the rack is sufficient to cause more significant movement in the smaller piping (but not the rack steel or the larger rack piping) in the rack such as the 3/4" pipe supplying the pumps with flush water. (we are working to isolate the smaller lines from the rack/pump better)
-
why only one dampener wobbles at a time?
I have read on a PD supplier brochure that if the diameter of the piston is more than 1/2 the length of the stroke then the size of the pulsation dampener needs to be different than the simple sizing calculation gives?
The pump isn't vibrating that much so why the dampeners and the rack?
Why one dampener and then the other at DIFFERENT speeds if both are charged per instructions?
I am hoping the answer is more complicated than that we are hitting several harmonic frequencies in our system and getting resonance.
Three triplex pumps in parallel with each other discharge to a pipeline. The pumped fluid is from the brine and fast rinse cycles of a water softening plant and the brine is mixed using oilfield produced water. A separate source of filtered produced water is pumped by centrifugal pumps where both flows are being transported through the pipeline to disposal. The resulting system provides a variation of backpressure to the triplex pumps of between 800 and 1200 psi. The discharge piping is full port except for some glove valve style piston check valves. The two different pump system discharges tie-together far away from either of the pump batteries.
The triplex pumps have a seal flush of fresh water, a suction pulsation dampener, and a discharge pulsation dampener. The suction is 6" and the discharge 3"x4". The source for the brine is pumped through some filters and a pressure control valve upstream of the filters maintains a set pressure above the suction pressure requirements of the triplex pumps plus the dirty filter pressure drop. The pumps are mounted on steel blocks and a steel frame together with the gear box and motor. The steel is W shape I-beam 12" deep, anchored and grouted to the foundation.
The triplex pumps are 3.25" dia pistons with 5" stroke and the pumps are operated at between 100 and 400 rpm on an adjustable speed drive. The pulsation dampeners both have an opening equal to the respective pipe diameter and appear to be the correct volume. We have checked the charge on the suction and discharge and it appears to be the correct charge. We checked the bladders and they are holding.
The problems:
-At certain speeds the discharge pulsation dampener will vibrate (wobble) more than is typical but the suction dampener is barely moving at all; and then at other speeds the opposite is true. This is independent of whether 1 pump or 2 or 3 pumps are running together. Also, the sound around the pumps is not abnormal and the pumps are running smoothly.
-at any speed including when the dampeners are NOT wobbling and the pumps sound smooth then the vibration at the rack is sufficient to cause more significant movement in the smaller piping (but not the rack steel or the larger rack piping) in the rack such as the 3/4" pipe supplying the pumps with flush water. (we are working to isolate the smaller lines from the rack/pump better)
-
why only one dampener wobbles at a time?
I have read on a PD supplier brochure that if the diameter of the piston is more than 1/2 the length of the stroke then the size of the pulsation dampener needs to be different than the simple sizing calculation gives?
The pump isn't vibrating that much so why the dampeners and the rack?
Why one dampener and then the other at DIFFERENT speeds if both are charged per instructions?
I am hoping the answer is more complicated than that we are hitting several harmonic frequencies in our system and getting resonance.
