API 610: 1. 1.1
What's It All About?
General Introduction
API 610 has been written to ensure safe and reliable pumps are used in a dangero us industry. Below we have summarised the major features and requirements of API 610. This paper has been written to provide you with an overview. You should not rely on this paper for your full knowledge of API 610 nor to make a decision as to whether you use, or do not use the API 610 standard. We recommend that that y ou read and understand the standard before deciding whether to, or how to, apply it to your application. 1.2
Scope
API 610 is a standard that covers the minimum requirements for centrifugal pumps for use in petroleum, heavy duty chemical and gas industry services. It include s pumps running in reverse as hydraulic power recovery turbines. 1.3
Why is API 610 Published?
API 610 has been written to ensure a minimum standard for: Safety: Safety is of prime importance in the petroleum industry. A cracked pump casing, failed bea ring or leaking mechanical seal can lead to a major catastrophe. Reliability: After safety, production is of prime importance in the petroleum industry. If production stops, it can cost millions of dollars per day. Maintainability: If a pump is removed for an overhaul, it must be back in ser vice as quickly as possible to ensure safety back up and no loss of production.
1.4
Who Publishes API 610?
The API standards are published by the American Petroleum Institute. 1.5
Who Uses API 610?
Owners and operators of the following facilities typically specify API 610 when purchasing all of their pumps: Offshore Oil Platforms Onshore Oil Fields Oil Processing Facilities Oil Refineries Oil and Petroleum Product Pipelines and Terminals Gas Processing Plants LNG Plants It is also used by owners and operators of the following facilities to purchase heavy duty (high pressure or high temperature) pumps, not covered by other indus try standards:
Chemical Processing Plants Power Stations (Boiler Feed Water Pumps) Co-Generation Power Plants 1.6
Pump Types Covered
API 610 covers all types of centrifugal pumps likely to be required in the oil a nd gas industries, these include: Horizontal and vertical Single stage, two stage and multi-stage Single case and double case (barrel type) Vertical sump and vertical canned (or double case) 2. Features of the API 610 Standard 2.1
Long Reliable Life
API pumps must be designed and constructed for a minimum service life of 20 year s and at least 3 years of uninterrupted operation (clause 2.1.1). In practice there are many API 610 pumps in industry that have been operating fo r in excess of 40 years and many oil refineries are now reporting MTBF figures i n excess of 7 years. 2.2
Casing Design
The pump pressure casings must be designed using the stresses, welding and inspe ction practices given in the pressure vessel code (2.2.1). Overhung pumps, between bearings radially split pumps, multi-stage pumps and ver tical double case pumps are to be designed with a pressure rating equal to the l esser of 4,000 kPa-g or an ANSI 300# flange rating (2.2.2). Radially split casings are required if temperature of fluid is above 200 deg C, the fluid SG is less than 0.7 or the discharge pressure is above 10,000 kPa-g (f or flammable or hazardous fluids) (2.2.6). Overhung horizontal single stage pump casings should have centreline supports (2 .2.9). 2.3
External Nozzle Forces and Moments
API 610 lists the maximum forces and moments, which the pump nozzles must be abl e to take, and still give satisfactory performance. Case distortion and shaft mi salignment are considered when assessing satisfactory performance (2.4.1). The pump must meet these requirements without any bearing housing support (3.3.6 ). 2.4
Rotors
Default impeller design is closed and constructed as a one piece casting. Except on vertical suspended pumps, impellers must be keyed to the shaft and secured b y a cap screw or cap nut, which in turn must have a positive mechanical locking
method (2.5.1, 2.5.2, 2.5.3) Shaft runout is limited to 0.001 inch (2.5.6). Shaft stiffness must limit the deflection at the mechanical seal faces to 0.002 inch (2.5.7). This is most important for long mechanical seal life. 2.5
Wear Rings
Pumps must have renewable wear rings on both the casing and impeller (2.6.1). Th e minimum wear ring clearances are specified (2.6.4). 2.6
Mechanical Seals
There is now an API standard for mechanical seals, API 682 (2.7). Both API 610 and API 682 specify seal chamber dimensions. These dimensions help ensure an ideal environment for the mechanical seal. 2.7
Vibration
API 610 specifies maximum allowable vibration levels nominally 3.0 mm/s RMS unfi ltered, at the bearing housing (2.8.3). 2.8
Balancing
Balancing and balance grades are specified for the various pump configurations, these can be summarised as: Single stage and two stage pumps: 8.4.1).
impellers dynamic balanced to Grade G1.0 (2.
Multi-stage pumps: impellers and major components balanced to grade G1.0, roto rs balanced to G2.5 (5.2.4.2) 2.9
Bearings
Minimum L10 design bearing life is 25,000 hours, at rated conditions (table 2.7) . In practice most API 610 pumps will have an L10 bearing design life far in exc ess of this figure. Bearing housings must have constant level oilers fitted. 2.10
Drivers
Driver power ratings must be at least equal to the following (table 3.1): Motor kW Percentage of Rated Pump Power <22 125% 22-55 115% >55 110% 2.11
Baseplates
Strict guidelines are given for baseplate design. These design criteria ensure m inimal misalignment of pump and driver shafts (3.3.5). Baseplates must be single piece drain rim or drain pan design, to ensure that an y leakage is contained within the baseplate (3.3.1, 3.3.2). Pump and drive train components must have mounting pads, fully machined flat and parallel. Values are specified for measuring compliance (3.3.3).
2.12
Inspections
The manufacturer must keep quality records for at least 20 years (4.2.1.1). 2.13
Material Inspections
The purchaser should specify which parts are to be subjected to surface and subs urface examination, and the type of examination required (i.e. magnetic particle , liquid penetrant, radiographic or ultrasonic) (4.2.1.3). The standard lists the appropriate procedure and acceptance criteria for these e xamination methods (4.2.2). 2.14
Testing
All pressure casings must have a hydrostatic pressure test, with liquid at a min imum of 1.5 times the maximum allowable working pressure (refer to the standard for special provisions) (4.3.2). All pumps are to be performance tested unless stated otherwise. The standard giv es detailed requirements for the testing and tight tolerances on test results (4 .3.3). NPSHR and Complete Unit Tests (i.e. test of pump and driver train complete with all auxiliaries) are optional, to be performed when specified (4.3.4). 2.15
Summary
In summary, the features of API 610 are: Heavy duty casing design Centreline supports Low shaft stiffness ratio Low shaft deflection at the seal faces Long design bearing life Low vibration levels High allowable forces and moments on nozzles Stringent testing requirements These features help ensure a long safe and reliable life for your complying API 610 8th edition pump. References Centrifugal Pumps for Petroleum, Heavy Duty Chemical, and Gas Industry Services API Standard 610 American Petroleum Institute Related Topics Specifying an API 610 Pump
