+ve Displacement Pumps

2.1.15 self explanatory - if your design capacity (required) is 100LPM the pump should be rated for 110LPM at least.

2.1.16 - the actual flow should have an error of less than 1% when it is checked over a range (= turn down ratio ie from the rated to 10% of the rated). Check here. In the positive displacement pumps we procure the flow must be constant over a outlet pressure range (rated to 10% of rated - ours are rated at 400 Bars so it should have constant flow between 40 bar to 400 bar)

Guest i think there are a number of issues here and I have some other views from the other guest

2.1.15 On the basis of your process design you have come up with a requirement. When you specify this flow to a pump vendor the pump they supply must be rated (ie capable of pumping) 110% of this flow. It is always prudent ot have a 10% margin on flow from a pump to allow for debottlenecking so that there is more flow than you expect; practical developments which might change the rate of addition of the chemical and so on. It is just not sensble for ht epumpt o be only just capable of supplying the required flw. ALso yo uneed to allow for manufacturing tolerances. Note that the pump motor needs to be designed for this 110%

2.2.16. The other guest is talking about a range of pressure outputs which I dont htink is the intent of this clause. (Apart from it being a surpriising process arrangement)

You would normally expect these pumps to operate reliably between 10% or normal flow and 100% of normal flow. IMHO the turndown on a pump refers to the flow rate not the pressure delivered. This is much wider turndown than you would get with a centrifugal pump.

The pump is required to give a flow accuracy at 1% over the full range to turndown.

Say Pump Normal Flow = 100 litres / min

The Turndown Flow - 10 litres / min

At turndown flow accuracy is 1% ie 0.1 litres / min

So I thinkt he intention is that the pump delivered flow is accurate to 1 in 1000 at the normal flow. This seems a very strenuous demand.I cannot imagine how oyu would measure it as many flowmeters are not that accurate!

hi

Regarding cl.2.1.15 , The rated capacity as defined by the API is the flow rate during the normal operation.Does this mean rated conditions are operating conditions.In that case maximum capacity of the pump should have been greater than the operating/rated capacity? Pl clarify