Mechanical Seal Leakage Problem

[andrenov]

Dear Floor,

Currently in our operational area, we are facing mechanical seal leakage problem on our BFWP. Even though we are using a treated water which regularly monitored for its quality, the leakage is still often occured.

The feedwater pump is horizontal multisatage pumps with a horizontally split casing. A constant speed 4160 HP electric motor drives tat pump. The suction piping of the pump includes a tee type strainer (3/16" dia. removal) which provides additional pump protection from the solids enter the system.

The operating fluid is boiler feed water , with SG 1.0, vaporating presure 7.5 PSIA, 180 Deg F, 1.0 CP viscocity.The chamber pressure is 100 - 300 PSIG, suction pressure is 50-250 PSIG and discharge pressure is 2960 PSIG.We are using API Seal Flush Plan no. 11, with injection rate 4 GPM.

Currently we are using cartridge type of mechanical seal.There is 18" to 10" reducer from the incoming header to the suction piping, and there is 12" to 8" reducer from the discharge piping to the outcoming header.And we are often facing the mechanical seal leak problem.

I also attached the technical drawing and sectional drawing of the mechanical seal together. Please take a look on that.


Kindly need your advice, please.

Thanks

Best Regards,

-andrenov-

 

[andrenov]

The mechanical seal technical drawing.

 

[CaracasEC]

Seal plan 11 with this temperature is not as efficient as plan 23 as normal seal plan with boiler feed water pumps. lubricity of water at 80 deg C and above lessened. Please also check the orifice on the seal piping for possible plug otherwise correct amount of flow cannot reach the seal chamber.

 

[vpl]

Andrenov

Just for clarity -- is this the same pump discussed in thread378-305052 -- only moved to a pump forum as suggested by JJPellin?

Patricia Lougheed

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[andrenov]

@ Patricia Lougheed,


yes this is the same question , somebody from there suggests me to ask in this forum. He said that I might get the better response here..

Thanks

@caracasec,

If changing the seal plan is one of the solution, which one is more appropriate plan 21 or plan 23?

thks

 

[Pumpsonly]

Plan 21 will need higher cooling water flow as the flushing water will be always at the 180F. You only need to add a cooler onto the PlaN 11 piping.

Plan23 will require lesser cooling water flow as you only need to remove the heat generated by the mech seal faces.

But you will most likely need to add a pumping device into the seal cartridge assembly to circular the water.

Adding a TI on the piping after the cooler will help you to control the temp of the flush to acceptable level.

 

[JJPellin]

I would never recommend installing a Plan 21 with a water cooler in 180 °F water. The load on the cooler would be too great and the likelihood of liming up the cooler too high.

Johnny Pellin

 

[CaracasEC]

I agree with JJPellin, Plan 23 is better. Plan 21 is not a preferred plan, either by API or many users due to the high heat load put on the heat exchanger. A plan 23 is preferred.