API versus ANSI centrifugal pump

[stewbaby]

I've always struggled as to when to specify an API pump versus an ANSI pump. We have a small refinery and tank farm and except for the few hot and severe duty conditions inside the plant that an API pump is the obvious choice, I see no reason that ANSI shouldn't be used everywhere else. Does anyone have any good "rules of thumb" or specifications they can share?

Also, I like in-line pumps (such as Goulds 3996) due to there simplicity of installation and ease of maintenance. Any "rules of thumb" on when to use a horizontal instead of an in-line for typical oil services (flows less than 800 GPM, press less than 300 PSI, temp less than 300 F)?

 

[Montemayor]

Stew:

There are various ways to decide on the Specification Type of pump you settle on for your applications. But whichever way you employ, you should be thoroughly familiar with the Specifications that you compare. I’m assuming that you are. It would be a waste of time to debate either ANSI or API Specs if both were not completely understood and digested.

I cannot reasonable argue against your consideration of an ANSI spec for your refinery site. I also agree that there are valid and practical reasons for specifying vertical, in-line pumps. I personally developed a hatred for these when I started applying them in the 1970’s. I still think they’re a pain in the neck when the motor is around less than 20 HP. It can be expensive dealing with having to install overhead beams & dolly with lifting capabilities for the smaller motors. Additionally, vertical in-lines can be installed successfully in the majority of cases only when the process design is the original one. To do a vertical in-line pump retro-fit installation after the plant is built and up-and-running is awkward and usually more expensive. Additionally, it is an added expense to invest in special, vertical motors as spare stock. It is an inherent advantage of horizontal pumps that they require only standard, off-the-shelf horizontal motors with their conventional bearing design. This is less expensive.

However, in all fairness, I went through an era when vertical thrust bearings and seals were a pain in the neck for close-coupled vertical in-line pumps. It was a mess. It was such a mess that it forced both ANSI and API to focus on their specifications for this type of application. I’ve seen improvements in the designs today. You have much better bearing design and better access to shaft seals and distance pieces. Also, the motor size and footprint have been considerably reduced. If your personal experience bears out an advantage for vertical in-line pumps, I’d go for it.

Years back, the argument against API was traditionally that it was a belt-and-suspenders, cast-iron specification that covered all possible cases of mechanical failure and corrosion. As a result, it was more expensive to build according to the API specs. Today, I see the advantages of having the API specifications because they have become well-documented and written. One can now easily read and visualize what you are obtaining with such a specification. The API specifications on seals speak for themselves as to detail. API specifications force you to look at all the details before deciding.

My rule-of-thumb has been to always consult and decide with my maintenance department right along side of me and to always heed what they warn against. Of course, there have been arguments and confrontations, but the issue has always been: what is best from a safe, economical point of view? We never allowed any bias or “preference” motives to intervene and distract from the objectives. For example, the issue of non-conventional motor requirements for the vertical in-line pumps should be well understood and accepted before going forward. By becoming knowledgeable of both ANSI and API specs and going through the evaluation exercises you are already well ahead of most other installations in ensuring that you are operating at close to an optimum point – regardless of which specification you decide on.

 

[stopsunset]

The API standard is the most comprehensive engineering document with regards to safety and pump reliability. It was designed specifically for refinery applications whereas ANSI was developed for the chemical industry. The attention given to design detail(nozzle loading,torsional/lateral analysis,sealing,shaft deflection) is un-matched, imho. As a reliability engineer working in a refinery, it's a simple decision. If it handles hydrocarbons(I make no exceptions)I go with API. Anything else ANSI would work.

 

[pmover]

although it has been awhile since reading the ANSI and API pump stds (api i have, but ansi are buried at home), but i seem to recall that ansi pumps are limited to a certain size (i.e. flow and head) and this std is used in chemical industry. the api std is certainly the std widely used in oil & gas applications/industry. as explained to me, the main differences between the two stds are materials of construction (api being more robust) and size limitations (i.e. flow and capacity) for ansi pumps.

best to read the first few pages of the ansi & api std and note any limitations.

-pmover

 

[checman]

Stew: If the pump is used to transfer ambient temperature product at moderate pressures ANSI pumps work just fine. But if you have a pressurized suction or elevated temperature or the pump is part of a critical process API is the way to go. The tank farms in my area for the most part are ANSI pumps and they are pumping everything from HF to fuel oil. I was wondering if maintenance really likes the inline pump. I always thought they where a pain. A horizontal pump with the C face motor option to eliminate coupling alignment has more appeal to me. The pumps bearings and seals can be more easily isolated from the process heat. Less lifting of equipment and if a valve leaks or the product being pumped is extremely hazardous it can be easier to slip a blind flange in.

Regards checman