New pump with Plan 32 question? 1

[justabitconfused]

Hello all, we are looking to install a new pump in our facility and I am happy with the pump being offered along with a single seal with Plan 32. What I am not so happy with is the proposed supply of demin water that is proposed to supply the seal plan. The pump is being installed into a piping system with class 150 flanges and typically has a discharge pressure of around 7 barg. The demin water supply is going to be taken from a system that is normally at around 11 to 12 barg but it can go as high as ~15 barg. What concerns me with the Plan 32 system is that if the suction and discharge valves are closed on the pump, then it seems to me that the full pressure of the demin water system can be applied to the pump casing through the Plan 32 needle valve and the seal chamber throat bush. I think this exceeds the rating of the class 150 flanges fitted to the pump. Should I insist that a relief valve is fitted to the Plan 32 tubing? Thanks.

 

[flexibox]

very interesting question that I had experienced before and in that case the field experienced a problem with the RV and Plan 32 was not affective because of a problem with the RV. They changed seal arrangement to Plan 53B.
Surprised to see that you are using demin water as Plan32. can you give us some details on the duty condition, product, temp, SG etc as you may have alternative seal arrangements that may not need Plan32. I assume that demin water is not an issue for you to use but on the other hand this can be expensive and as you know diluting the process which may not be an issue for you.
once you provide some details we can make further comments to assist. I personally do not like the idea of installing a PRV in a Plan 32 system

 

[justabitconfused]

Thanks for the interest flexibox, it's appreciated. The chemical being pumped is at around 40 Deg C and has something of a tendency to crystalise on the seal not so much as Sodium Hydroxide, for example, but it does so to an extent. The Plan 32 is intended to help reduce that tendency and extend seal life. The duty is actually to pump the chemical to dilution facility using the demin water, so adding it at a Plan 32 seal arrangement is not an issue. Thanks again.

 

[flexibox]

You can consider an upstream pumping seal which uses a non pressurized seal pot (plan 62mod). This seal has spiral grooves that picks up the water contained in seal pot and pumps it across the seal face. The fluid film is water and avoids crystallization. This arrangement is very reliable and avoids your pressure rating issue. Water consumption is very low in the order of cc/hr, the seal pot should be equipped with an auto shutoff valve on the water supply line.

Trust this helps

 

[justabitconfused]

I haven't seen a Plan 62 using an un-pressurised pot before but I can see how it would work. Thanks for the interest.

 

[knapee]

I wonder why demi water is used as supply in plan 23.
Cause API Plan 23 is generally used on hot application and minimizes the load on the heat exchanger. It needs to cool only the heat generated by the seal faces and the heat that has migrated through the seal chamber casing.

Thanks.

 

[justabitconfused]

Knapee, I'm talking about Plan 32, not 23! Thanks.