To specify the piping plan on an API 682 datasheet, select the plan by its Annex G number on the Annex C datasheet, write the same number as the last field of the seal code, and then state the fluid, reservoir, instruments and supply split that the plan number alone leaves to the vendor.

Everything below follows the 4th edition of API 682, published in May 2014 and reaffirmed in March 2022, which is still the current edition.

What to Settle Before You Write the Plan Number

Settle the seal category, type and arrangement first; in API 682’s selection procedure all three come before the piping plan, which comes last. The plan family then follows the arrangement:

  • Arrangement 1: a single seal, with a flush plan such as Plan 11 or Plan 32.
  • Arrangement 2: an unpressurized dual seal, with a buffer plan such as Plan 52.
  • Arrangement 3: a pressurized dual seal, with a barrier plan such as Plan 53A, 53B or 53C.

The duty-by-duty choice of plan within the family is in our guide to selecting a mechanical seal flush plan.

Where the Piping Plan Goes on the Datasheet

The piping plan is selected on the Annex C mechanical seal datasheet and appears again as the last field of the Annex D seal code. Enter the arrangement and the plan before the entries that depend on them.

You do not have to use API’s form. The standard calls the Annex C, E and H forms representative, but they hold all the information that has to pass between purchaser and vendor, so a company datasheet has to carry the same content.

How to Write the Plan in the Seal Code

The piping plan is the eighth and last field of the 4th-edition seal code, written as the plan number. The fields run in this order: category, arrangement, type, containment device, gasket material, face material, approximate shaft size in millimetres, and piping plan.

The containment, gasket and face fields accept X for unspecified, so a project datasheet can carry a code before those materials are chosen. The old five-character API 610 code (BSTFN and its variants) still appears on pump datasheets, but it does not apply to API 682’s requirements and definitions, and Annex D lists it as obsolete.

When the system departs from a standard plan far enough to need different instruments or operating procedures, write Plan 99. Plan 99 has no defined objectives or equipment of its own, so the whole system has to be defined in the project or purchasing specification. A minor change, such as a pressure indicator swapped for a transmitter, has historically kept the standard plan number.

How to List More Than One Plan on One Seal

Write every plan in the piping-plan field, separated by a slash. The 4th-edition code table gives 11/52 as its example: a Plan 11 flush on the inner seal with a Plan 52 buffer system on the outer seal.

A dry-running containment seal usually needs several plans at once: Plan 72 for the buffer gas, and Plan 75 or Plan 76 to collect and monitor the liquid or vapour leakage. A Plan 62 quench on the atmospheric side is listed beside the process-side plan in the same way.

When to Name 53A, 53B or 53C Instead of Plan 53

Name the suffix whenever you have a preference; a plain “Plan 53” leaves the variant open. The three are distinct systems: 53A pressurizes a reservoir with gas, 53B uses a bladder accumulator and 53C a piston accumulator, as set out in our comparison of the three.

Pressure is the usual reason to name 53B or 53C. The 2nd edition’s tutorial advised a maximum Plan 53A system pressure of 10 bar (145 psi), and the 4th-edition Task Force did not agree whether any such threshold should stay. Treat the 10 bar figure for Plan 53A as a point to settle with the vendor.

If the choice is still between a buffer and a barrier system, that is the Plan 52 vs Plan 53 decision, and it comes before the suffix.

What to Specify Beside the Plan Number

Beside the plan number, state every option of that plan you have a preference on: the buffer or barrier fluid and reservoir, the instruments, who supplies each part of the system, and for Plan 32 the flush source.

Buffer or Barrier Fluid and Reservoir Size

Name the fluid, and state the reservoir requirement as days of operation. Use the term that matches the arrangement: an unpressurized dual seal runs on buffer fluid, and a pressurized dual seal on barrier fluid. The buffer or barrier fluid has to be compatible with both the process fluid and the seal materials.

The 4th edition requires the buffer or barrier working volume to last at least 28 days of operation without topping up. Earlier editions fixed the working volume at 3 gallons for shafts under 2.500 in and 5 gallons above; the 4th edition keeps those pots as the Plan 52 and 53A defaults, so a datasheet note asking for a 3- or 5-gallon seal pot names a pot size, not the 28-day volume. Add the 28-day requirement to it, or state why a different volume is wanted.

Instruments and “If Specified” Options

Call out every instrument that should differ from the 4th-edition default. Since 2014 the default on piping plans is transmitters with local indicators; earlier editions used switches and indicators, and a purchaser who still wants switches has to request them on the datasheet or in the specification.

The plan number does not tell the vendor which instruments you expect, so list the instrument type for each monitored pressure, level or flow.

Seal Vendor and Purchaser Scope

State on the datasheet who supplies the reservoir or accumulator, the instruments, the interconnecting tubing, and the cooling water or makeup supply. API 682 does not fix the split between seal vendor and purchaser: the two agree on the features taken from the standard, and transferring the data is their joint responsibility.

External Flush Source for Plan 32

For Plan 32, the datasheet has to state the flush source in four entries:

  • Fluid: the flush fluid by name, compatible with the process, because it ends up in the product.
  • Pressure: how far the flush pressure sits above seal-chamber pressure.
  • Flow: the flow rate the seal needs.
  • Continuity: that the supply runs continuously, including during start-up and shutdown.

How to Specify Plugged Connections and No-Flush Plans

A seal with no flush, or with ports kept for later use, is specified by plan number like any other:

  • Plan 02: the seal runs in a closed chamber with no circulation, historically used in low-duty services, high-temperature services and fluids with a high solids content.
  • Plan 03: new in the 4th edition, circulation created by the seal chamber’s own design, typically a tapered chamber with flow modifiers, so no flush piping is needed.
  • Plan 61: tapped connections on the atmospheric side of the seal, plugged for the purchaser’s use.
  • Plan 71: containment-seal connections run dead-ended and plugged for the purchaser’s use; it also applies when no other containment-seal piping has been specified.

Plans 61 and 71 are listed beside the process-side plan, separated by a slash.