Pump with a 20inches suction dia. 3

[pump23]

I need to calculate the ALLowable nozzle loads for an axially split case pump with suction dia 20 inches. It is designed according to ANSI standards. Standard for calculating the allowable nozzle loads is ANSI/HI 9.6.2 (Rotodynamics Pumps) but in this standard table for maximum nozzle loads contains load values upto 10 inches dia only.

How Do I calculate loads now? Is there any formula for interpolation of these loads?

One more thing is that it is written that the loads also depends upon the wallthickness of the pump(obvious) but in the standard while calculating allowable loads, wall thickness of the pump is not considered.

Can anyone help?

 

[BigInch]

Use the loads for the 10". Allowable loads are so small anyway. It's not like you're going to get 1000 lbs/inch in allowable loads.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[pump23]

ok..but what about wall thickness??? loads vary with that also right.
we are considering the nozzle size only. How would I know If the thickness is also fine?

 

[BigInch]

Loads on the pump need not depend on pipe wall thickness. Loads placed on the pump due to piping pressure, temperature, product weight, wind, etc., can all be controlled by pipe FLEXIBILITY, ie. configuration, support locations and type of support provided. The basic idea is to make the pipe as flexible as possible near pumps, try to shoot for as close to ZERO load delivered to the pump to begin and with a little luck, when you get the final stress printout, the resulting loads will be lower than what the pump mfgr allows. Intially shoot for load of NONE to ZERO.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[pump23]

I understand your point. But I am not designing a piping system, I am resposible for providing values of Allowable forces and moments on the pump suction and discharge flange (nozzle). Wall thickness which I am reffering to is of Pump's wall thickness.

 

[BigInch]

Then you'd better post that question in the pump forum. How much case distortion can you tolerate.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[pump23]

Earlier I posted a question related to allowable nozzle loads in pupm engineering forum but did not get any good replies, so I thought may be piping guyz know because they deal with kind of same situation on the pipes also.

 

[BigInch]

We are always told to not put more than 75 lbs on them, or some other rediculously low load on them, and we don't get a chance to argue about it either.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[1gibson]

"Did not get any good replies" huh? Well that just hurts my feelings.

Again you have issues with phrasing the question. There are two problems here:

1) How to extrapolate (not interpolate) loads for flanges larger than 10" to come up with industry acceptable values (linear extrapolation is not going to be acceptable)
2) How to confirm the pump design is adequate to handle these loads without any operational problems


"The loads depend on the wall thickness of the pump." No... Manufacturing a pump with thin suction/discharge piping certainly isn't going to cause a revision to the industry standard to lower allowable nozzle loads. You have it backwards, the wall thickness of the pump depends on the allowable loads.

Put some more thought into the specific areas you are having trouble with, and pose those questions individually. You should mention your goals when relevant, and when it helps clarify the nature of your request. Hard to tell if you want to design piping, design a pump, or just want to fill in some datasheets.

 

[racookpe1978]

Re-read the (very reasonable) answers to your original questions.

You WANT zero loads on the pump suction AND discharge nozzles.

You might have to tolerate very small loads (less than 75 to 50 lbs, or hand pressure when installing), but you WANT zero, regardless of what size pump you are installing.

 

[C2it]

The only way you will get zero piping loads on a pump is to leave it in the stores.

 

[Pumpsonly]

pump23, If i understand you correctly your problem are.

1) you want to find out what is the required allowable nozzle load of a 20 inch suction diameter axially split case pump
designed according to ANSI/HI 9.6.2.
2) But the ANSI/HI 9.6.2 only provide value for required allowable nozzle load for pumps up to 10 inch only.

3) You are looking for fomula/ guide line to calculate the required value for a pump with 20 inch nozzle.

I do not have copy of ANSI/HI 9.6.2. but I believe you are looking for some thing similar to the attached page extract form API-676 3rd Edition.

What is your purpose of finding out the value? do you need the value for your piping design verification or you are designing the pump.

Pump designer will use these required allowable load to determine the casing wall thickness and also the rigidity of the supporting feet.

 

[BigInch]

I've never seen values that high! Not even as high as half. NEVER!

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[1gibson]

I have, those are lower than API 610 values (centrifugal.) I've had customers complain about having to stay within 2x API 610 nozzle loads. For 16" side nozzle, these are X/Y/Z: 3800/4600/3000 lbf, moments X/Y/Z: 10600/5400/8000 lt-lbf. They actually asked me if the nozzlehead was made of tinfoil when I rejected their piping analysis... Ultimately we did an FEA with their desired loads, showed them the 0.015" deflection it caused in the seal chamber area and told them we wouldn't warranty seal failures from misalignment. All of a sudden they changed some assumptions/constants in their piping program and the loads ended up within our original criteria (2x API.) That didn't stop them from asking for 4x API 610 nozzle loads on the next project, ridiculous.

I commented in a thread a few weeks ago about checking nozzle loads transferred to foundations and it may have been seen as nit-picky. Maybe now it makes more sense?

 

[BigInch]

Well ... I must be relatively good at pipe stress.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[1gibson]

I get a lot of 3 pump booster manifolds that look like the designer's previous work experience was making crazy straws. I guess the thermal must really make it tricky when they want to cover -45*C to +100*C in that tight of a space? Reduce the forces by adding flexibility and the moments go up. Try to reduce the moments and the forces go up. That's what I'm told, but at the end of the day I'm just a pump guy who doesn't have much sympathy when the EPC's computer program says there needs to be another zero on the end of my nozzle loads.

Maybe if they weren't building an expansion next to identical equipment with identical service conditions, that was designed without issues and has been operating trouble free for 5 years, I might feel a tinge of guilt telling them to go back to the drawing board.

 

[BigInch]

Just tell them to keep on increaseing flexibility. Nothing can stop the axial forces. Pipe O sections are very good at carrying bending moments, which are reduced in proportion to the square of increasing pipe length.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[C2it]

There is no reported history of pump failures in the North Sea and other areas where Norsok R-001 has been applied since early 1990's. The code (section 5.2.2.1) allows from 2x API 6010 for 150# pumps up to 10x API 610 for 1500# pumps. Yes, ten times API 610.

A better designed pump and base plate will save potentially a huge amount on piping required just for nozzle load load related flexibility, with attendant reductions in space and weight.

 

[BigInch]

There you go. I always had suspicions that the pump mfgrs were slagging us on their allowable pump loads.

"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek

 

[DubMac]

Its about time you guys caught onto us.......been purposely building skinny pumps for years, just to screw the pipers.