Pump Wisdom. Robert X. Perez

reliability. This standard is often used for pumping services that qualify for one or more of the labels hazardous, flammable, toxic, or explosion‐prone. The API‐610 standard has been called a quality standard, although that should not be viewed as a negative comment on the fitness of ANSI and ISO pumps for safe and long‐term satisfactory service. API pumps are centerline‐mounted (Figure 2.2); ANSI pumps are usually foot‐mounted (as shown earlier in Figures 1.1 and 1.2). The thermal rise of the shaft centerline of a horizontal ANSI pump can be as much as three times greater than that of the centerline‐mounted API pump. Thermal rise is taken into account during pump alignment (Chapter 14).

Figure 2.2 The suction and discharge nozzles on this centerline‐mounted API‐style pump are upward‐oriented. Oil mist lubrication is applied throughout; the coupling guard was removed for maintenance.

      Source: Lubrication Systems Company [1].

      But the API‐610 standard should not be viewed as infallible and the wording in the inside cover of the standard makes that often‐overlooked point. Reliability‐focused users have seen justified to deviate from it when experience and technical justification called for such deviations. This text will deal with some of the issues where API‐610 needs user attention and suitable amendment.

      Experience‐based selection criteria summarize the proven practices of the Monsanto Chemical Company's Texas City plant in the 1970s [2]. Among these was the recommendation of using in‐between‐bearing pump rotors whenever the product of power input and rotational speed (kW times rpm) would exceed 675 000.

      For general guidance [2] asked that API‐610 compliant pumps be given strong consideration whenever one or more of the following six conditions are either reached or exceeded:

       Head exceeds 350 ft (~106 m);

       Temperature exceeds 300 °F (~150 °C) on pipe up to and including 6 in. nominal diameter; alternatively, if the temperature exceeds 350 °F (~177 °C) on pipe starting with 8 in. nominal diameter;

       Pumps with drivers rated in excess of 100 hp (starting at 75 kW and higher);

       Suction pressures over 75 psig (516 kPa);

       Flow in excess of the flow at best efficiency point (BEP) for the pump at issue;

       Speeds in excess of 3600 rpm.

      Exceptions to the six conditions can be made judiciously. To qualify for such an exception, the pumped fluid should be nonflammable, nontoxic, and nonexplosive. In general, exceptions might be granted if the vendor can demonstrate years of successful operation for the proposed pump in a comparable or perhaps even more critical service.

      Best‐in‐class (BiC) pump users are ones that are able to get long failure‐free runs from their pumps. BiCs have on their bidders' lists only vendors (or custom builders) with proven experience records. Such vendors and manufacturers would be well established and would have a record of sound quality and on‐time deliveries.

      Exceptions taken by a bidder to the owner‐operator's specification would be carefully examined for their potential reliability impact. This examination process serves as a check on the pump manufacturers' understanding of the buyer's long‐term reliability requirements. Orders would be placed with competent bidders only.

Because these vendors use a satisfied workforce of experienced specialists, do effective training and mentoring, and have not disbanded their quality control and inspection departments, their products will command reasonable pricing. Reasonable pricing should not be confused with lowest pricing, although reasonable pricing may indeed be lowest in terms of life cycle costing.

Vertical pumps are available in many hundreds of styles and configurations and Figure 2.3 shows a two‐stage pump custom‐built for pipeline service. This pump is unique because the entire pumping element can be removed as one piece for maintenance. The motor mount (with the motor attached) would be removed first, 24 screws are removed next, and the whole pump lifted out. It is a good example of a design that is user‐oriented in terms of maintenance and probable overall reliability [3].

      Both API and non‐API standards are used in custom‐built pumps, depending on user preference, type of service, and prevailing experience. Competent designs are available not only from original equipment manufacturers (OEMs) but also from certain key custom design innovators and manufacturing specialists. We count them among the quality providers.

In all instances, the pump owner‐operator would compile a specification document that incorporates most, if not all, of the items discussed in this text. The pump owner‐operator or its designated project team would mail the document to at least two, but more probably three or four of these quality bidders or quality providers. Their replies or cost quotes would be carefully reviewed. These replies would describe the vendor's offer pictorially, and Figures 2.4 and 2.5 are typical of add‐ons and/or alternatives that the vendor can submit together with suitable documents in support of its claim of proven experience.

Figure 2.3 Custom‐built vertical pipeline pump with drive motor removed.

      Source: Alfred Conhagen Inc. [3].

Figure 2.4 HPI process scheme and API pumps offered for the various services.

      Source: Sulzer Pumps, Ltd. [4].

Figure 2.5 Canned Motor Pumps can be superior alternatives to conventional centrifugal process pumps.

      Source: Hermetic Pumpen, Gundelfingen, Germany.

      What We Have Learned

       Getting good pumps requires an up‐front effort of defining what the buyer really wants. The user's present or future maintenance philosophy will determine what belongs into a specification. The bid invitation must encourage vendor‐manufacturers to alert owner‐purchasers to superior choices, if available.

       Without a good specification, the buyer is very likely to get a “bare minimum” product. Bare minimum products will require considerable maintenance and repair effort in future times. For instance, oil mist lubrication is not usually included in “bare minimum” offers [5].

       The specification document must be submitted to competent bidders only. Some bidders may ask you to grant a waiver to a particular specification clause; insist they prove