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2 Pump Selection and Industry Standards

Anybody can buy a cheap pump, but you want to buy a better pump. The term “better pumps” describes fluid movers that are well designed beyond just hydraulic efficiency and modern metallurgy. Better pumps are ones that avoid risk areas in the mechanical portion commonly called the drive‐end. That is the part of process pumps that has been neglected most often and where cost cutting should cause the greatest concern.

Deviations from best available technology increase the failure risk. As three or four or more deviations combine, a failure is very likely to occur. An analogy could be drawn from an incident involving two automobiles, with one driving behind the other. When the trailing vehicle travelled at (i) an excessive speed, with (ii) worn tires, on (iii) a wet road, and (iv) followed the leading car too closely, a rear‐end collision resulted. Had there just been any three of the four violations, the event might be recalled as one of the many “near miss” incidents. Had there been any two of the four, it would serve no purpose to tell the story in the first place.

Too much cost‐cutting by pump manufacturers and purchasers will negatively affect the drive‐ends of process pumps. Flawed drive‐end components are therefore among the main contributors to elusive repeat failures that often plague pumps – essentially very simple machines. Drive‐end flaws deserve to be addressed with urgency, and this short chapter will introduce the reader to more details that follow later in Chapters 5, 8 and 10.

Why Insist on Better Pumps

Well‐informed reliability professionals will be reluctant to accept pumps that incorporate the drive‐end shown in Figure 2.1. The short overview of reasons is that reliability‐focused professionals take seriously their obligation to consider the actual, lifetime‐related and not just short‐term, cost of ownership. They have learned long ago that price is what one pays, and value is what one gets.

Figure 2.1 A typical bearing housing with several potentially costly vulnerabilities.

Anyway, while at first glance the reader might see nothing wrong, Figure 2.1 contains clues as to why many pumps fail relatively frequently and sometimes quite randomly. It shows areas of vulnerability that must be recognized and eliminated. The best time to eliminate flaws is in the specification process. A number of important vulnerabilities, deviations from best available technology or just plain risk areas exist in that illustration:

 Oil rings are used to lift oil from the sump into the bearings;

 The back‐to‐back oriented thrust bearings are not located in a cartridge;

 Bearing housing protector seals are missing from this picture;

 Although the bottom of the housing bore (at the radial bearing) shows the desired passage, the same type of oil return or pressure equalization passage is not shown near the 6 o'clock position of the thrust bearing;

 There is uncertainty as to the type or style of constant level lubricator that will be supplied. Unless specified, the pump manufacturer will almost certainly provide the least expensive constant level lubricator configuration. Putting it another way: The best lubricators are rarely found on newly sold pumps.

Each of these issues merits further explanation and will be discussed in Chapters 5 through 9. Recall also that our considerations are confined to lubrication issues on process pumps with liquid oil‐lubricated rolling element bearings. The great majority of process pumps used worldwide belong to this lubrication and bearing category. Small pumps with grease‐lubricated bearings and large pumps with sleeve bearings and circulating pressure‐lube systems are not discussed in this text.

ANSI and ISO vs. API Pumps

ANSI stands for American National Standards Institute; ISO is the International Standards Institute, and API is the American Petroleum Institute. In general, ANSI and ISO pumps comply with dimensional standards; the measurement conventions are inches and millimeters, respectively. ANSI pumps will have the same principal dimensions regardless of manufacturer, as will ISO‐compliant pumps in their respective size groups. Principal dimensions, for the sake of this overview include, but are certainly not limited to, the distance from base mounting surfaces to the shaft centerline, or to the pump suction and discharge flange faces.

The widely used API‐610 pump standard is aiming for high strength and 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 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.

References

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)