Deviation to API 676 performance tolerance para 8.3.6 a(table 5 )

[scorpiorajan]

Hi,
We have some pumps for permeate extraction for Jazan project ( client : Saudi Aramco)
Type of pump: Lobe type as per API-676
The lobe is coated with elastomer/rubber material

As per the pump manufacturer " they cant comply to performance tolerance as specified in para 8.3.6 (table 5 ) of API-676.
Test tolerances will be only positive (e.g. no negative) meeting the intent of API 676, 3rd
Ed at rated capacity + 15% (max).
Instead pump manufacturer following German VDMA rules for positive displacement pumps (VDMA 24284), Class
II, Grade II are offered for rated power:
Motor tolerances:
Rated power at rated capacity:
< 5 kW + 25 %
5 - 10 kW + 20 %
11 - 50 kW + 15 %
< 50 kW + 10 %
These tolerances are applicable for Lobe pumps as rotor material will be an
elastomer/rubber material which has larger tolerance range then Rotary pumps with
metallic liners.
In this case Kindly advise to accept the exception to API -676 tolerances ?

Thanks for your kind reply.
regards,
rajarajan

 

[Cecorros]

Ideally you would need to check with Saudi if they are willing to accept the efficiency levels that come with the VDMA tolerances in power that you mention, i.e. a maximum of %25 to values inferior of 5 kW

The rated capacity tolerance that you say is contained in API-676 is 15% maximum - does this apply to any value of a rated power?

It would help if you can post details of the application, e.g. pump curve, data sheet. What power does your pump have?

 

[scorpiorajan]

Hi
Sorry for the delayed response, please find the attached performance curve of the pump.( the data might not be clear enough to read), i am trying to get the readable copy.

I made a mistake in my previous mail, its a API -676 progressive cavity pumps and not the lobe pumps.

This pump is operating at 2 case with Adjustable frequency drive.

Thanks for your prompt advice.

 

[scorpiorajan]

The attachment was missing in my previous thread, please find the below link.
Sorry for the inconvenience.

http://files.engineering.com/getfil...&file=performance_curve_and_process_data_.pdf

 

[Cecorros]

The absorbed power of the pumps you are offering will fall then in between 11-50 kW: +15% tolerance - from what you've written the VDMA rules state.

API-676 Table 8.3.6 highlights a tolerance of +4% for the rated power - see from below link.

http://pmo5e085f.pic23.websiteonline.cn/upload/api676-2009_zw33.pdf

Again, go back to Saudi and ask them if they are willing to have a a 15% tolerance in the pump power instead of 4% when testing.

If you could then come back confirming that they would.