Use this framework to agree on the design, fabrication and testing of a metering pump product.
by Rick Ray
April 11, 2019

API 675 is a comprehensive standard issued by the American Petroleum Institute (API) that is intended to provide a purchase specification covering controlled volume, positive displacement (PD) pumps for petroleum, chemical and gas industry services. The standard covers hydraulically actuated and packed plunger metering pumps. It provides a framework for the manufacturer and purchaser to agree on the design, fabrication and testing of a metering pump product. The standard is available for purchase on the API website, api.org.

This guide is intended for informational purposes only and is not a substitute or alternative to the API 675 standard itself.

The standard is divided into sections as follows:

  1. Scope—This standard denotes the seller and buyer’s responsibilities. The buyer is responsible for details marked by a bullet at the beginning of a paragraph. Further clarifications can be added to the API 675 data sheet (Annex A), the purchase requisition, and/or the purchase order.
  2. Normative References—This section lists the standards and specifications that apply to pumps furnished in accordance with API 675. Included are API specifications, American Gear Manufacturers Association specifications (AGMA), American Society of Mechanical Engineers (ASME) codes, American Welding Society (AWS) codes, Institute of Electrical and Electronic Engineers (IEEE) codes, International Organization for Standardization (ISO) codes, National Association of Corrosion Engineers (NACE) material standards, National Fire Protection Association (NFPA) code and Steel Structures Painting Council (SSPC) commercial blast cleaning codes.
  3. Terms & Definitions—This section covers the nomenclature used to identify and define performance, construction, manufacture and testing of the product before shipment. Some of the terms covered include acceleration pressure, linearity, steady state accuracy and turndown ratio, which are all critical to metering pump performance.
  4. General—This section covers unit responsibility (the pump vendor is responsible for all sub-suppliers used). It also covers governing requirements and units of measure (U.S. customary [USC] or International System of Units [SI]), and pump designations, types of drives and types of liquid ends.
  5. Statutory Requirements—Determination of responsibility for compliance with any government codes, regulations, ordinances or rules that are applicable to the equipment, its packaging or any preservation procedures employed.
  6. Basic Design—This section gives detailed requirements for the pump, including design for parts such as pressure containing parts, liquid end connections, flanges, check valves, diaphragms, plungers, relief valve applications, drive-train enclosures, bearings lubrication and capacity adjustment. Also covered in detail are materials of construction, including low temperature service, and nameplates and rotation arrows.
  7. Accessories—This section covers motors, couplings and guards, baseplates, controls and instrumentation, pulsation suppression devices, and any special tools required for pump maintenance. It also includes a table listing minimum requirements for piping materials.
  8. Inspection, Testing & Preparation for Shipment—This section covers all aspects of testing that apply to the product components, including inspection records, materials testing, mechanical testing and positive material testing (PMI). A table listing material inspection standards is included. Testing of the finished product—including hydrostatic, performance and mechanical run testing—is covered. Linearity and repeatability testing and acceptance criteria, which are specific to PD pumps, is detailed. Optional testing covered includes net positive inlet pressure (NPIP) testing, sound level test and factory acceptance test (FAT). Optional testing must be specified by the purchaser. Preparation for shipment covers steps taken to protect and preserve the product, including interior and exterior cleanliness and rust prevention, protection of flanged and threaded openings, and identification of lifting points and lifting lugs, to name a few.
  9. Vendor’s Data—This section details the data that is required of the vendor. Categories covered are:
    • General: Includes commercial identifications, such as purchaser name, purchase order number, vendor name, project identifiers and any other information required to properly identify the contractual parties.
    • Proposals: Includes technical aspects of the project, including drawings, technical data and test results such as performance curves, NPIP testing, as well as any specialized testing required by the purchaser.
    • Contract data: Detailed in this section are formats, identification markings and submission timing, as well as considerations for drawings and technical data, progress reports, parts lists and recommended spares, installation operation and maintenance manuals and technical data manuals.

The following annexes are attached to the specification:

  • Annex A (Data sheets): Contains controlled volume pump (API 675-3rd) data sheets in USC and SI units. These data sheets are used to document the site details, performance criteria and equipment furnished. These data sheets are used to clearly outline the expectations of purchaser and seller. • Annex B (Materials): Contains a table of miscellaneous material specifications.
  • Annex C (Inspector’s checklist): Lists suggested items for inspector’s due diligence.
  • Annex D (Controlled volume pump vendor drawing & data requirements): Commonly referred to as VDDRs, this section details the drawings, technical data and test results that are expected to be furnished by the seller for the pump, driver and any accessory equipment that is part of the scope.
  • Annex E (Net positive suction head [NPSH] vs. NPIP): Suction conditions are critical for a positive displacement metering pump. This section covers the differences between NPSH and NPIP. A formula and explanation is provided for calculation of NPIP.
  • Annex F (Pulsation & vibration control techniques): A key consideration in the design and construction of a chemical injection system using a positive displacement metering pump is control of pulsations and vibrations. This section contains two different analysis approaches and discussion of mitigation techniques.

In summation, API Standard 675 third edition is a tool for developing purchasing parameters between the purchaser and the vendor. It clearly defines the scope and responsibilities of the concerned parties and how they should be communicated.