MOL pump auxiliary seal flushing

Does this help? Seal-flushing in centrifugal-pumps, improved methods and apparatuses Document Type and Number: United States Patent 4878676 Link to this page: http://www.freepatentsonline.com/4878676.html Abstract: Disclosed is an improved method of centrifugal pump impeller-shaft seal-flushing; comprising the step of supplying pressurized seal flush fluid to a centrifugal pump impeller-shaft seal within an operating centrifugal pump: (a) axially, from the rear; (b) radially, circumferentially evenly; and (c) circumferentially, inclined forwardly at a positive acute angle from parallel-to-axial. Thus resulting in greatly prolonged seal life.

So you are using the Plan 32 connection then, external flush? So you know 100% of the flush will enter the pump and be gone into the discharge diluting your oil? Just checking.

Flow to each seal is one US gallon per minute per inch of diameter. So a 4 inch seal needs 17 liters/m. If you have a between bearing pump with two seals then each seal must be 2 inch to be able to use your 17 liter pump. If this is a more than a single stage pump without a balance line, then the seal nearest the suction flange is near suction pressure (maybe .3 barg higher) and the other seal chamber is the suction pressure, plus half of the discharge pressure. If there is a balance line, then both seal chambers will be at about 0.3 barg above suction pressure.

Pressure should be 2 barg or so above the seal chamber but ask Sulzer and also ask the seal guy because it depends on how the seal faces are with respect to the flush entry point. Too much pressure will erode them. Seal people tend to know more than pump people about seals.

The Plan 31 should have orifice plate and a check valve if there is a Plan 32 also. So what is the pressure takeoff point of the Plan 31? Match that pressure and you can reuse the orifice.

This article may be of interest.

www.hydra-cell.com

Flush water should enter the process (crude oil) after the stuffing box. External flushing connections are Plan 61. Plan 31 takes the crude straight from the discharge of the MOLP (approx. 42 barg) and it does have the restriction orifice, but the Plan 31 piping shall be modified so to include two new valves for cutting off the crude inflow to the stuffing boxes (drive and non-drive end) during the flushing operation. Aux. pump pressure was chosen bearing in mind the following: the aux. pump pressure should be great enough to overcome all frictional losses, stuffing box pressure (MOL's suction), breake possible solid clogs and to finally enter the process on the suction side of the MOL pump runner. So the main concerne is, is 25 barg going to be enough in worst case (this should be MAWP for the aux. pump)?