Specifying vertical turbine pumps
for the municipal market

By

Dennis Lund

While in Engineering school a guest lecturer, David Gossard of MIT, told the assembled students:

"Professors discussing Engineering Design are like Priests discussing marriage: lots of learned thought, but very little practical experience."

The point made was practical knowledge cannot be supplanted entirely with information garnered from scholastic sources alone. A level of synergy, between interested factions, must exist in the development of specifications for vertical turbine pumps. The final specification should reflect the needs and desires of the customer, the hydraulic experiences of the Engineers and the first-hand practical experience of the end user. The method used to deliver this information lies in the specifications written by engineering companies which then results in proposals received from the pump companies, delivered to contractors acting as the medium for presentation or review of the proposed products.

Those involved in reviewing the specifications and in producing the end product have the same goals as the Engineers who write the specifications: To deliver a product that meets the needs of our common customer, the end user, while doing so in a fair and openly competitive manner. To that end it is important that a set of specifications clearly reflects the goals of all involved parties.

With the above as background, following are some factors relevant to the process which need to be kept in mind by specification writers.

The first issue the engineer must be aware of is the purpose of the specifications to all involved, as well as the goals to be achieved. These factors would include:

• Establish the level of quality required for the equipment to be purchased.
• Describe in detail the requirements of the application in a clear fashion.
• Equalize the scope of supply between all potential suppliers.
• Equalize the design parameters for the specified product.
• Provide documented assurances that the supply of the equipment is within specification requirements for design and quality.

Secondly, the priorities of the client; the municipality or agency involved, must be clearly understood. Often times these factors may not be specifically expressed, though the situation is improved if they are. These factors include:

• Cost – is the user willing to pay a higher price to get an end product that will better serve his long term needs?
• Reliability/Longevity – The maintenance capabilities of the end user can impact design options that may add (or negate) design options selected. For example; An end user with a knowledgeable and capable maintenance department may be in a better position to push-pull pumps for routine maintenance.
• Frequency of use – Should a pump designed for occasional use be built to the same level of engineering options as a unit used with a high degree of frequency?
• Redundancy – Is a spare pump to be installed in the system to reduce repair time pressure in the eventuality of the need to pull a pump?
• Experience – What is the level of experience of the end-user including: Various manufactures, the maintenance department, plant standardization and other factors?
• Service – How key is the service to the overall operation of the system? How much downtime can be tolerated in the event of a failure?

Before the engineer develops a specification the above factors should be openly discussed with those involved in the process. The answers may already be known by the experienced members of the engineering team and should be shared during specifications development.

An additional area of consideration; What industrial guides are to be referenced and in what manner? For example, are specific sections or entire documents to be referenced? Some of those available would include:

• ANSI – Primarily used as a dimensional standard for various components.
• Hydraulic Institute – Established in 1917 to define standards: Testing, Terms, performance criteria, Pump Types, sump design and more.
• American Petroleum Institute – Standards first issued in 1924 as a design criteria for pumps in refinery and other petroleum related applications.
• ISO 9001 – Established to monitor procedures in manufacturing of equipment.
• NSF – Federal regulation on lead and other metallic ions leaching into drinking water.
• Other Options - Independent, Internal, or other specifications from suppliers. Relying on past specifications reduces the burden on fresh development, but should be updated on a project to project basis.

In writing a specification the engineer should be aware of both the quality level for the final product desired, as may be reflected by reviewing the parameters mentioned. The manufacturer’s selected to be listed in the specifications should be those whose level of expertise best fits the level desired and experience needed. As we look at the types of pumps made and specifications used to manufacture them we have the following levels of increasing cost and complexity:

Level One: Agricultural – Materials are Cast Iron/Bronze fitted, collets only, Cast Iron head, 150# flanges, no specifications, packed box, no testing or Q/A requirements. Off the shelf availability.

Level Two: Light Industrial and Municipal – As above with either Fabricated steel or Cast Iron head, Mechanical Seals, some Testing and Q/A Documentation, Keyed impellers, wear rings often required. Deliveries times are longer but relatively short.

Level Three: Heavy Industrial – Fabricated heads often required and seals only, high levels of testing, Q/A, specification requirements and documentation. ISO 9001 and NSF may be seen.

Level Four: API/Cryogenic/High Specification Muni – As above but detailed specification requirements including predefined Q/A, testing, documentation and materials, NDE seen, ISO 9001 and NSF usually required. Long lead times are common.

Level Five: Nuclear – Highest level of Specifications, Q/A, NDE documentation and Testing.

Those involved with Vertical Turbine Pumps, be they end users, manufacturers or specifying engineers all share a common goal, that being to produce or use a final product that best serves the goals established as reflected in the specifications written.