At deadhead cond. This give a max diff. Gravity 0, The max pressure in the suction is the max outlet pressure of the sphere. This spere is forseen with a safety stting of 15 Barg. The max. Adding this to the max. So the design pressure taken for the minimum flowline is The quantity taken out is pumped back to the sphere at the time of no demand to the pipeline. The variable frequency drive will lower the speed at that time but the pump will still running. Please any comment?
Thank you in advance. We want to unload a oil well at offshore and send the flow through the Crude oil export pump to other platform. The pump will take suction from a production separator and first feeds a booster pump and then the Crude oil export pump. So the plan is to run the COEP on recycle.
But as the oil is bound to get heated up beyond pump design temperature, designer has proposed to install heat exchanger of the recycle line and cool the oil that goes back to the suction vessel , production separator.
My query is can the pump system survive if the initial well flow is very low about bopd as against bopd in normal condition. Can the min flow recirculation line of such pump have a shell and tube heat exchanger, in which the recycle oil flow passes through the tube side.
Can the recycle stream handle such resistances of passing through the tube side of the exchanger and still satisfy min flow requirements adequately? The minimum flow operation proposed is quite low, as you are obviously aware. Temperature rise is a concern. The pump manufacturer should take a look at this to ensure that the temperature rise does not lead to internal flashing vaporization.
Also, vibration at such low flows will likely exceed API specifications. This may or may not be acceptable and should be discussed with the pump manufacturer. Concerning the shell and tube heat exchanger, these can be readily customized for the application and there should be no problem selecting the tube side configuration to satisfy the flow resistance requirements. The proposed conditions, as generally described, are feasible, but the technical details of the pump and the heat exchanger selections are important.
If we design a pump whose flow can be adjusted by varying stroke of pump can we solve this problem?. Minimum flow, as an operational constraint, is applicable to rotodynamic centrifugal or radial, mixed flow and axial flow pump types.
The value of minimum flow for these pumps varies widely and can depend upon a number of factors. With positive displacement pumps, minimum flow is not so much the issue as is the discharge or back pressure which must not be permitted to exceed a specified value.
Minimum flow on reciprocating pumps is often determined by the method of lubrication. If the power end is splash lubricated, it will need to rotate above a minimum speed to supply adequate lube oil to the bearings. If the pump is force lubricated with an external pump, you can slow them down much more.
Detail of the efficient pump operation instruction will lead us achieving longer pump life. Yes, the closer we are to the most efficient rate of flow for the pump, at a given operating speed, the longer the pump can be expected to operate trouble-free. Hi all I have some questions about minimum flow line for centrifugal pumps: 1. Who is responsible for considering minimum flow line for pump?
This would be filled in by the pump vendor. It is customarily the responsibility of the process engineer to design and specify the minimum flow piping, valves and means of control based on the vendor provided data sheets and the process system requirements. Offhand I would say that for the pump you mention, a minimum flow line is not normally specified. But the process engineer must evaluate the temperature rise and rate of temperature rise, the margin to prevent flashing of product in the pump and mechanical seal and the system overall to determine whether a minimum flow line or special pump sensors and controls might be needed.
Hi Randal, Firstly, great job. This is an excellent and extremely informative discussion forum. Now, coming to my query, I work for a licencor in oil and gas sector and so have very limited direct interaction with vendor.
The selection among these three options is done on basis of power requirement of the pump. Can you suggest a more accurate method to select the type of minimum flow system required in basic engineering phase? Each industry and each pump application is going to have special process, operational, safety and specification requirements to consider. If one narrows the problem down to a specific industry and a specific process type, then design guidelines or a decision algorithm can be developed — you may already have something along these lines.
Power requirement of the pump is the most rational point to start because input power directly affects temperature rise. Conceptually, one might be able to generalize sizing of the piping and the fittings required based on the head and flow of the pump, with different types of minimum flow control arrangements being decided by other factors such as power, process type, etc.
But as one attempts to more broadly cover the range of process applications, or cross over into other industry categories, the level of effort is certain to escalate. Hi Randal, Thanks for the detailed explanation. Just to summarize your view, the approach based on power requirement is quite good in basic engineering phase.
Regarding type of industry, we mainly deal with hydrotreating and hydrocracking operations — so gasoil, VGO, diesel, naptha and sour water are the things that we mainly need to pump. And the discharge pressure roughly varies from about 6 kg to 80 kg kg in case of hydrocrackers. Based on this additional information, if you can suggest any other more specific guideline for selection of minimum flow arrangement, it will be very helpful.
Kindly advice the right selection. Sunil, Even though the input power is greater for the second offering, I believe it would be the better of the two. There might be additional factors which could lead me to recommend the first offering or suggest that either of the two offerings are fine. Good luck, Randal. Hello Sir, We are facing peculiar problem in our centrifugal pump. The pump is intended to deliver stabilised crude oil from stripper column to Flow suction Tank crude.
These pumps are new pumps replacing the old pumps. Now the scope was to replace the pumps but there was no scope related to minimum recirculation line updation. We missed to check its adequacy. We asked vendor to revisit the MCSF and reduce the values. Privacy Policy. Shop Our Products.
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Below is an illustration of a simple minimum flow bypass line. Meeting Minimum Flow Conditions Every pump has a minimum flow requirement. Protection Against Deadheading Our Application Engineers always recommend installing a recirculation line when high pressure pumps are in use.
Process Liquid Impact Consideration Meeting minimum flow and protecting the pump against deadheading conditions are the main reasons why recirculation loops are installed.
Previous Story. Next Story. November 11, Mechanical Seals vs. When the energy to bypass minimum flow exceeds 10 brake horsepower, an alternate method can often be justified. Another approach is to install an instrumented flow-control loop, which opens bypasses liquid at low flows and closes when process demand exceeds pump minimum flow. A typical system includes a flow meter, bypass control valve with its related automation, and mainline check valve.
An orifice or other backpressure-creating device may be required to prevent flashing in the bypass valve and return pipe. These valves have multi-purpose built-in functions, including mainline check valve, flow-sensing elements, bypass flow-control valve and bypass pressure-reducing valve. The ARV operates without air or electric power and can be installed with three piping connections, on or near the pump discharge, just as an ordinary check valve would be.
On pump startup and without process demand, the bypass is completely open, recirculating the necessary minimum flow. Once process demand begins, the spring-loaded disc is lifted and held in position by flow demand. Until main flow demand exceeds recommended minimum flow, the valve will bypass enough flow so the sum of the process flow and the bypass flow equals or exceeds minimum flow. As the main flow demand increases beyond recommended minimum flow, the bypass will close, and all flow will go to the process.
Once ARVs are installed and insulated, they should not be forgotten. When investigating minimum flow equipment needs, end users should consider doing the following steps:. Edwards is the vice president for HBE Engineering of Three Rivers, Michigan, a supplier of centrifugal pump minimum flow valves and orifices.
He has worked in the pump and related equipment field since and has a B. Subscribe Now and Get: In-depth articles on pump industry issues Expert insights into important topics in the field Keep up with trends, basics, and more. Breadcrumbs You are here: Home. Understanding the pros and cons of various minimum flow protection systems can help you optimize your entire system.
HBE Engineering. Understanding the causes and effects of minimum flow damage in centrifugal pumps is critical for knowing how to prevent it.
Improving Efficiencies For example, a boiler feed system was designed with three pumps—two for parallel operation and one standby spare. Minimum Continuous Safe Flow Minimum continuous safe flow MCSF is the flow at which a pump can operate continuously without excessive wear from hydraulic anomalies and temperature rise associated with low-flow conditions.
If the answer is yes to any of the following questions, a pump is probably operating below the safe minimum flow: Are the impeller vanes first-stage impeller if a multistage pump pitted or worn through? Are the wear rings or journal bearing bushings worn more on one side even though the pump shaft appears to be centered when in a static condition?
Has the pump experienced shaft breakage that could not be explained? Thermal Damage Since the s, it has been common practice to hold the temperature rise of the product being pumped to at most 15 F. High Radial Thrust High radial thrust is often the common root cause of a single-stage pump failure. Pump Surging If a pump does not have adequate flow, it can build up discharge pressure. Rotor Vibration Low-flow operation results in a mismatch of flow incidence angles in the impeller and diffuser vanes.
Internal Recirculation At reduced flow, centrifugal pumps can experience a flow reversal where the fluid turns and flows back upstream. Table 1. Continuous Recirculation System. Conventional Multi-Component System. References I.
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