Vent and Drain Connections

From ethanhan

Why vent and drain are needed in pump??? probably where is it located?

Hor Win Han

-----------------------------------------------------------------------------------------------------

Dear Ethanhan,

I think you are referring to vent and drain connections pursuant to API 610 sealing plans.

I will assume that your query relates to API610.

Within API 610 there are a number of shaft sealing plans which I believe cross-relate to API 682 Shaft sealing systems for centrifugal and rotary pumps. See also ISO 21049.

The standards will provide for a number of tappings (normally half inch NPT I think?) in the seal chamber on the API 610 pumps. These tappings may be used, or not used, dependent on the pumping application. These are normally located in the seal chamber.

The vent and drain connection – sometimes also called the quench connection can be used for a number of purposes. For example suppose you were pumping some really thick stuff like bitumen or tar you could introduce low pressure steam to stop the ‘liquid’ solidifying on the shaft/mech seal when the pump was stopped or when the liquid cooled down to ambient temperature.

You could also use the tapping to use a water flush to take away any leakage from the seal area. In the event of a seal failure (if a double mech seal was used) the ‘vent’ could take away this liquid – this is handy for example if you were pumping something nasty like acid or other highly corrosive or toxic liquids.

But please look at API 610 and API 682 for further guidance as I am no expert in this field.

Regards

John

-----------------------------------------------------------------------------------------------------

From S. L. Abhyankar

Senior Member

Vent and Drain are also provided on most volute casings of centrifugal pumps.

The vent connection is to release any air or gases likely to get entrapped in the casing, which is always a possibility especially with split casing pumps and end-suction pumps with side discharge volute.

Drain connection is of course at the bottom-most portion to drain, better still, flush and drain any settle-able foreign matter entraining in the flow or material disintegrating due to corrosion or abrasion.

The drain connection will be of fairly large size in case of solids-handling pumps, such as paper stock pumps.

Hygienic pumps, such as pumps in dairies need flushing at regular intervals. So, instead of a simple drain connection, the pumps are provided with quick clamping and unclamping feature.

S. L. Abhyankar

Rated Duty & Nominal Duty

From rainman

Member of Forum at www.lightmypump.com

March 14th, 2008,

Pump Rated Conditions

---

For centrifugal pumps, what do the term “rated” parameters (flow, NPSHr, etc.) mean? How do the pump manufacturers determine these values? Are these values specified by the customer or the pump manufacturer? My questions arise because I wonder if my rated flow for any particular pump should change when the normal flow for this pump is changed, as a result of a new condition being implemented in the plant where it is used (say a revamp). To illustrate my point further, I have a pump originally designed to handle a normal flow of 50 m3/h and for which a “rated” flow of 56 m3/h, was defined, according to the information provided in the pumps data sheets for the original project. After some years, a revamp of the plant is under way, which requires a new normal flow of 53 m3/h. Under these circumstances, will I have a “new” rated flow also, if the pump and the hydraulic (curve) system remain the same? What if I change my system (by increasing, for instance, some pipe diameters)?

Thank you all in advance for your feedback,

Rainman

From S. L. Abhyankar

Senior Member

March 17th, 2008,

Dear "Rainman",

By my understanding of the terms "Rated Duty" and "Normal Duty", Rated Duty would be the duty on the nameplate of the pump, printed by the manufacturer, declaring the pump's compliance with the duty mentioned in the order from the buyer. "Nominal Duty" would either be

i) the duty at the point of best efficiency (BEP) or

ii) If it is a pump supplied as per a standard, such as ISO-2858, there are "Nominal" duties or ratings specified in the standard

Coming to your point about changes that may happen in the performance of the pump, or change needed in the performance of a pump during revamp, the duty obtainable from a pump is the point of intersection of the system curve with the pump's curve. For example, if you change the system, using larger pipe sizes, as mentioned by you, the system curve would become one with less friction. So, one would get more discharge from the pump. Whereas less friction and higher flow would mean better performance of the pump, at higher flow the driver may get overloaded. So, one needs to also check the power requirement of the pump at the changed duty.

I hope, I have touched most of the points raised by you.

S. L. Abhyankar