Robert X. Perez - Pump Wisdom

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 2.3shows 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 2.4and 2.5are 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.

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 that they have understood the reason and purpose of the clause they are unable or unwilling to meet. Never waste your time on bidders that take blanket exception to your entire specification.

If the owner–purchaser of a process plant grants a waiver to a certain specification clause, he should understand the extent to which noncompliance will lead to increased maintenance requirements, downtime, or even catastrophic failure risk.

In the end you get not what you expect, but you get what you inspect. Inspection is one of the costs of getting reliable process pumps.

1 1 Lubrication Systems Company; “Photo contributed by and used with the permission of Don Ehlert”, Houston, Texas, 2008.

2 2 Ingram, J.H.; "Pump reliability – Where Do You Start", presented at ASME Petroleum Mechanical Engineering Workshop and Conference, Dallas, TX, September 13–15, 1981.

3 3 Alfred Conhagen Inc.; Houston, Texas, 2010.

4 4 Sulzer Pumps, Ltd.; Winterthur, Switzerland. By permission, 2010.

5 5 Bloch, Heinz P.; “Optimized Equipment Lubrication: Conventional Lubrication, Oil Mist Technology, and full Standby Protection”, DeGruyter Publishing, Berlin/Germany, 2021 (ISBN 978‐3‐11‐074934‐2)

Pumps can be found mounted in many different ways; there are times and places to do it at least cost and times and places to do it with uncompromisingly high quality.

Plants that use stilt mounting ( Figure 3.1) often fall short of achieving best‐possible equipment reliability. Best practices plants secure their pumps more solidly on more traditional foundations. Stilt‐mounted pump sets lack overall stiffness but have been used for small ANSI pumps where the sideways‐move capability of the entire installation was thought to equalize piping‐induced stresses. Among its few advantages is low initial cost.

However, there are serious shortcomings since stilt‐mounting will not allow pump vibration to be transmitted through the baseplate to the foundation and down through the subsoil. Proper foundation‐mounting permits transmission of vibration which can result in a significant increase in mean time between failures (MTBFs), longer life of mechanical seals and bearings, and favorably low total life‐cycle cost [1].

Again, proper field installation of pumps has a measurable positive impact on pump life. Even a superb design will give poor results if poorly installed. A moderately good pump design, properly installed, will give good results [2]. Proper installation refers to a good foundation design, no pipe strain (see Chapter 4), and good shaft alignment ( Chapter 14) to name just a few. No pump manufacturer designs its pumps strong enough to act as a solid anchoring point for incorrectly supported piping, or piping that causes casings and pump nozzles to yield and deflect. Also, pumps have to be properly secured to their respective baseplates, and these baseplates have to be well‐bonded to the underlying foundation. Epoxy grout is used to do this bonding in modern installations.