TO WHAT STANDARD WILL YOUR "STANDARD PUMP BE BUILT? Will your "Standard" Chemical Pump Really Meet the A VS Requirements? The proposed ASA chemical pump standards specify certain design requirements which help assure acceptable mechanical performance. The standards state that the total calculated shaft deflection under "the worst condition of load" must be .002" maximum at the face of the stuffing box, and that the calculated bearing life must be 2 years minimum "under the maximum loading anticipated." These two requirements determine the size of the shaft and bearings to be used. Pump manufacturers who furnish their Group II "Standard" pumps on light, medium, and heavy duty power ends, have interpreted the "worst condition of load" and "maximum loading anticipated" in different ways. One manufacturer interprets it to mean the worst condition (shutoff) for the selected impeller diameter (usually trimmed) and the operating speed offered. Others add a third qualification by considering the worst condition to
be "at the specified operating point," rather than shutoff. (Shutoff or closed discharge conditions are normally far more severe than operating conditions.) The obvious advantage of qualifying the "worst condition" is to the pump manufacturer, who can make a light duty pump and still call it "standard." The disadvantages are to the user. The light duty pump he buys for one "worst condition" may not meet the "standard" should he want to change any of the qualifying conditions, such as increasing impeller diameter, changing speed, or operating at a lower capacity than originally specified. Since he has to buy two or three different designs of "standard" pumps to cover the range, he has to stock two or three times as many power end parts. The Durco MARK II pump has only one bearing housing for ALL conditions — and that is the heavy duty size! Therefore, every MARK II meets the "standard" require-
ments with the largest size impeller at the fastest allowable speed and under the worst operating condition (closed discharge). Thus, the user can change operating speed, increase the impeller diameter, or change the capacity requirements, and still be within the standards. The additional advantages of one power end, one shaft size, and one mechanical seal size are quite obvious from both an inventory and manufacturing cost standpoint. BE SURE YOUR "STANDARD" PUMP REALLY MEETS THE STANDARDS. BUY THE DURCO MARK II PUMP WITH ONLY ONE BEARING HOUSING-THE LARGE ONE! And remember, only Durco offers the same standard bearing housing and foot mounting dimensions for four self-primers and three Durcon (modified epoxy) pumps. Watch for the announcement of four Duriron and Durichlor 51 wet ends on the same power end. Durco, Durcon, Duriron and Durichlor are all registered trademarks of The Duriron Company.
THE DURIRON COMPANY, INC., DAYTON, OHIO
IDURCO
