3 replies to this topic

[rsk]

As a role of process engineer in pump selection & sizing how he is concerned in pump specific speed, please start a discussion.
Thanks

[Art Montemayor]

rsk:

In order to discuss a subject, it is important to start the discussion knowing what it is that is going to be discussed and WHY. In order to continue the discussion, it is also important to know beforehand if it will entail a sharing of information and experience - or will it be a learning vehicle to pass on information to some of the participants. If the latter is what is desired, then the "discussion" is - in fact - NOT a discussion but rather a transfer of knowledge. If that is the case, then why not simply cite or state a series of quesitons and queries that are being pondered and will serve to profit those who are in need of such information? Discussions without a set plan or outline, ultimately wind up wasting a lot of time and wandering in many different directions - leaving those who lack the knowlege and background without any profitable gain. Discussions are best used among peers - persons who share the same level of expertise and experience. However, students, by definition, lack the background - but yet need the information for their formation and profit.

For example, the subject you propose as a discussion: centrifugal pump specific speed is a dimensionless index number which is used to relate the hydraulic performance of a centrigual pump to the shape and physical proportions of its impeller. This is a very specific and narrow subject - and quite honestly, one that most (if not all) students will fail to understand once the details are brought out.
On the other hand, Suction Specific Speed is a much more practical and useful centrifugal pump characteristic. The Suction Specific Speed is a function of the NPSH available in the centrifugal pump and is used to design and control the performance of a pump. In general, the change in vibration increases with increasing energy density, higher specific speed, and higher suction specific speed.

I recommend you and other students list out your queries and seek out answers to specific questions.

[rsk]

As u are saying suction specific speed is used to design a pump, whether this will have any basis in selecting the speed of pump in addition to mechanical considerations. Also some where in books i have read designing specific speed in the range og 8000-10000 metric units will have efficient operation. Also higher specific speed will call for multi staging design.

[djack77494]

As a role of process engineer in pump selection & sizing how he is concerned in pump specific speed, please start a discussion.
Thanks

rsk:
In this, your initial post, you ask about the role of the process engineer. In designing a hydraulic circuit, the heart of which is the pump, the process engineer typically completes the basic process data on a pump datasheet. He/she would include the pump's capacity, required head, fluid density, temperature, viscosity, and perhaps a calculated hydraulic horsepower. Also supply the available NPSH. He/she would not typically complete fields with the pump's speed, size, or any other mechanical details, which are left for the rotating equipment engineer to complete. (Or in today's world where we seem to be averse to doing engineering, this is sometimes left to the pump vendor. Yuck!)

An interesting phase often follows when the rotating engineer presents a list of vendor offerings which he/she feels will meet the stated requirements. An analysis of the relative merits of each offer may follow.

While I don't disagree with most of the other discussion in this thread, it has strayed from this initial inquiry. I concur with Mr. Montemayor's suggestion that you'd be better served with specific inquiries.
Doug.