A review of ISO and ANSI pump standards

Standards are an extremely important part of the industrial and commercial landscape. By specifying standards-compliant products, buyers can be assured that the items they acquire will meet important performance and safety requirements, even if they come from companies that the buyers have never dealt with before. Standards also guarantee an important degree of interoperability between products from different manufacturers. All of this contributes to competitive markets and economic efficiency.

Given that standards are so useful, it is perhaps not surprising that there are a lot out there, including “industry standards” (standards set by a dominant industry player), standards set by trade associations (e.g. NEMA for electrical equipment or API for oil and gas production machinery), national standards (e.g. ANSI, CSA, DIN…) and international standards (ISO). This article will focus on a comparison of two important sets of standards for industrial pumps: ANSI B73.1 and ISO 5199.

A Bit of History

The American National Standards Institute (ANSI) is a private, non-profit membership organization that was founded in 1918 as a cooperative venture by engineering organizations such as the IEEE, ASME and ASCE, and several US government departments. There are currently over 10,000 American National Standards (ANS) covering a wide range of products and processes.

ISO (a language-neutral title for the International Standards Organization) traces its roots back to 1946 when delegates from 25 countries met in London to discuss the future of international standards that could bridge the many national and industry-specific standards. There are now more than 19,500 international standards covering many aspects of technology and business.

Historically, ISO standards have had more impact in Europe and Asia, while ANSI standards are widely observed in the US and other parts of the Americas. However, there has been a degree of convergence as the two standards bodies borrow from each other. With the rise of globalization, ISO standards are increasingly influential.

ANSI B73.1 (Sometimes referred to as ASME B73.1.)

This standard was developed to address the needs of the chemical industry for a robust family of single-stage end-suction centrifugal pumps. The standard covers 27 pump sizes and specifies a number of key dimensions for each of these. Dimensions include overall height and length of the bare pump, nozzle and shaft diameters, the size, location and spacing of mounting bolts, etc. ANSI B73.1 also specifies some performance characteristics and a number of design features that are intended to ensure provide reliable service and simplified maintenance (e.g. back pull-out construction with replaceable wear rings).

Standardizing dimensions, mounting arrangements and basic layout means that ANSI B73.1 pumps from different manufacturers can be readily substituted for one another.

ISO 5199 (and ISO 2858)

These two standards cover the same type of industrial pumps as ANSI B73.1. The older ISO 2858 focussed on external dimensions and mounting details, while ISO 5199 also specifies a variety of performance requirements (e.g. minimum bearing life) and construction features (e.g. general layout, seal configurations). In some aspects (e.g. maximum permissible vibration levels) ISO 5199 is more stringent than ANSI B73.1

In general, pumps manufactured to meet the ISO 5199 standard will meet or exceed ANSI B73.1 requirements in terms of performance, reliability, serviceability and longevity. However, ISO 5199 pumps can’t be used as direct substitutes for ANSI B73.1 machines without some adaptations to the mounting plates and motor couplings. This is because mounting bolt layouts, shaft diameters and intake/discharge nozzle locations are different, even for equivalent size pumps. Because of their respective areas of origin, many ANSI B73.1 pumps have been designed to be attached to asynchronous electric motors with 60 Hz power supplies, with ISO 5199 pumps designed to be compatible with 50 Hz electrical services. However, most manufacturers of ISO 5199 pumps have 60 Hz models available. As well, the increased popularity of variable frequency drives (VFD’s) makes this distinction largely irrelevant.

While of course the easiest and most straight forward option for a North American company may be to pursue only ANSI standard products, doing so significantly limits your choices.  Many of the ISO certified products coming out of Europe, and Germany specifically, have impressive new energy efficient technologies that may not be available in their ANSI counterparts. There is a reason that German designed products are known for their quality, efficiency, and long service lives.  Why not at least consider an ISO pump for your system, even if it isn’t the easiest choice?  Energy savings from a European ISO product may just make it worth the effort.