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Flange for nozzle of pump

Flange for nozzle of pump

Flange for nozzle of pump

The related subject after search in the forums is shown here.

Does thrust force appear at the flange of a pump?

In the existing plant, I found the use of flange Class 600 at suction and discharge nozzle of pump. The shut off pressure of pump is less than the pressure rating of flange Class 300.

? Is this general practice to specify the higher rating of flange for pump nozzle?
? What is the factor to increase the flange Class? If Class 150 can withstand the internal design pressure, should we use Class 300 for margin?

Please comment.

RE: Flange for nozzle of pump

Whether or not the thrust force is carried by the flange of the pump depends on the pipework arrangement. Usually there are bends and valves bolted directly to the pump nozzle and a dismantling joint somewhere in the arrangement. The designer may chose to carry thrust through the pipework or transfer it to adjacent structures through supports and thrust blocks. The pump manufacturer assumes you are going to carry the thrust on the flange. He will also determine the class to suit the maximum rated pressure for the pump range he is selling. The delivery pressure is related to the suction pressure and the pump manufacture doesn't know what your arrangement will be. i.e he builds a machine and fits flanges that are rated for a certain pressure. You should determine the pipe and flange class that is adequate for your system - eg the maximum pump shut in head that the pump can generate on your system not the rated pressure of the pump.

RE: Flange for nozzle of pump


For some applications, pumps may be mounted in series in which case each pump in the train will see an increased pressure, both at the suction flange, and at the discharge flange.  It could be that, for your application, only one pump is required, with a substantially lower pressure than the pump is capable of handling.

As BRIS indicated, determine the pipe and flange class required for your system.


RE: Flange for nozzle of pump

If the application has a class 600 installed - the chances are that there is a solid reason for it - and if the rating condition is not the explanation - then it is probably linked to the stress in the piping lines. This is particularly relevant for applications where the temperature of the pumped liquid is significantly different from the ambient. I suggest to be very cautious before you contemplate derating your flanges. Do not forget one of the main laws of the mechanical life : do not fix something that works.

RE: Flange for nozzle of pump

It may be that the manufacturer has rationalised the body casting and drilling jigs for that pump size. The pump casing may be used on higher pseed applicatins where the shutoff head is greater than yours.

You dont mention if the pump is an API 610 or other standard that would help understand the question.

RE: Flange for nozzle of pump

Thanks for all comments.

The pump is conformed to API 610.

-Suction pressure of pump is 4 barg. The carbon steel piping upstream of pump is flange class 150.
-Discharge pressure of pump is 30 barg. The carbon steel piping downstream of pump is flange class 300.
-The hydrocarbon fluid has temperature 100 C.
-Both suction and discharge nozzles of pump are flange class 600.

I do not want to derate the existing flange...just curious about the design.

RE: Flange for nozzle of pump

the rating of a flange dependes on:
flange material (i.e. allowable stress)

all three combined.

the use of a 600 flange by the manufacturer may be due to an economic factor and not a technical one...

usually the casings are cast. having different models for the same size pump just because of the flange rating may not make economic sense...
it will affect the customer at the 1st connecting flange, only.
on the other hand the manufacturer can lower the price of their units because they do not have to develop a model for each flange rating... i.e. the "one-size-fits-all" approach.

using 600# will cover most of the industrial uses except the very high pressure/high temp designs (e.g p > 1440 psi for CS or low alloy steel between -20 and 100 F or p > 70 psig for AISI 316 for t > 1500F).

the NEMA and API standars limit the forces and moments imposed on nozzles.


RE: Flange for nozzle of pump

The can be difference in strength between a forged and a cast flange.  One reason to use physical dimesion of a higher Class flange.

RE: Flange for nozzle of pump

some companies (or sites within these companies) likes to specify pumps (and perhaps other components) to a higher flange rating than required by standards.

This is usually done based on experience showing that in this particular service frequenct service or maybe people stepping up on the pipes etc. requires selection to be conservative.

Best regards


RE: Flange for nozzle of pump

Thanks again for all comments. The casing material is JIS SCPH2 (Equivalent to ASTM A216-WCB).

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