api 682 mechanical seal data sheet excel free sample

Table of Contents API 682 / ISO 21049 .............................................................................................................................. 4 Introduction History of API 682 and ISO 21049 Scope of the Standard ............................................................................................................................ 6 Key Concepts .......................................................................................................................................... 7 Seal Types ............................................................................................................................................... 8 Type A Type B Type C Rotating vs Stationary Flexible Element Seals Seal Arrangements and Orientation Codes ............................................................................................. 10 CW - Contacting Wet CS - Containment Seal NC - Non-Contacting Arrangement 1 Arrangement 2 Arrangement 3 Seal Categories ....................................................................................................................................... 15 Dimensions .............................................................................................................................................. 17 Design Requirements ............................................................................................................................... 18 Accessories ............................................................................................................................................. 25 Inspection, Testing, and Preparation for Shipment .................................................................................. 29 Liquid Seal Testing Containment Seal Testing Dual Gas Seal Testing Hydrostatic Testing of Glands Air Testing of Seal Assemblies Pump Manufacturer Seal Test Overview of Annexes ............................................................................................................................... 35 Seal Selection Procedure ......................................................................................................................... 35 Piping Plans ............................................................................................................................................. 38 Plan 14 Plan 53A Plan 53B Plan 53C Plan 65 Plan 71 Plan 72 Plan 74 Plan 75 Plan 76 Data Sheet .............................................................................................................................................. 43 Seal Code ............................................................................................................................................... 43 Sealing Considerations in API 610 / ISO 13709 .................................................................................. 44 API 610 Seventh Edition (Obsolete) API 610 Tenth Edition / ISO 13709 Sealing Considerations in ASME B73 ................................................................................................. 49

API 682 / ISO 21049 Introduction API-682 First Edition was really a landmark document in the field of mechanical sealing. The standard was not a simple technical document but rather a complete overview of mechanical sealing in the refinery environment.

to the equipment types most commonly supplied (not every sealing solution but only the most common ones that have proven to be successful in the field)…

of meeting the objective of three years of uninterrupted service (the seal must be designed so it is capable of at least three years of service without adjustments, alterations, or refurbishment)…

Since the First Edition was officially published in 1994, it has become the highest selling API standard on mechanical equipment. It has been sold in over 25 countries and is universally recognized as THE standard for mechanical seals in the refinery industry.

Due to the success of the First Edition, API recognized the need for a Second Edition. One of the driving forces was the knowledge that the standard was being used in industries outside of refineries. Companies were using API pumps in chemical and petrochemical facilities. In addition, refineries were also ANSI/ASME pumps for many general or low-duty services. In either case, it was difficult or impossible to apply the First Edition to these applications.

Sealing technology has made great advancements since the release of the First Edition. Dual dry running seals and containment seals were now used commonly in refineries and chemical plants. New piping plans were developed to support these new seal types. There was confusion on how to designate these new seals, arrangements, and piping plans.

All of these factors influenced the direction of the Second Edition. The goal was to continue with the objectives of the First Edition while expanding into new industries and capture new seal technology. This was done with the clear intention of having the standard issued as an ISO international standard. Due to the long lead times required for ISO document review and approval, the Task Force decided to release the Second Edition ahead of the formal ISO document release. This way users could begin using the standard years ahead of the ISO release.

ISO 21049 was released in February of 2004. While the document is a little more polished than the Second Edition, the two are virtually identical in content. Any seal that was designed in accordance with our standards for API 682 seal design will also meet the requirements of ISO 21049.

The release of an updated “682 standard” in the form of ISO 21049 left API in am awkward situation. There were now two standards that were very close but not identical. Which standard should the user invoke? Most importantly to API, would people stop using the Second Edition because they believed that ISO 21049 was the latest release?

To solve this problem, API decided to release the Third Edition. This edition is identical in content to ISO 21049 – essentially a copy of ISO 21049 with an API cover on the front. In this way, both standard have the same requirements and it removes the confusion of which standard to use.

From Flowserve’s perspective, any seal that was designed in accordance with API 682 Second Edition design standards will fully meet the requirements of both ISO 21049 and API 682 Third Edition. All seals that were qualified in accordance with API 682 Second Edition are also qualified under the other two standards. The release ISO 21049 and API 682 Third Edition have little impact on our seal selection and design practices.

Scope of the Standard As stated earlier, the 682 Task Force did not intend this standard to cover every piece of rotating equipment in a refinery. It was intended to cover perhaps 90% of the sealed rotating equipment. The various editions have the following scopes.

The First Edition used the term “Seal Size” throughout the standard. This lead to some confusion since differ- ent seal OEMs use different criteria for determining their commercial designation for a seal size. The Second Edition (and beyond) uses the shaft diameter which is unambiguous. With this cleared up, the First Edition was limited to seal sizes from 30mm to 120mm (1.50” to 4.50”). The Second Edition (and beyond) is applica- ble to shaft sizes from 20mm to 110mm (0.75” to 4.30”).

The First Edition was written specifically to be used in API 610 8th edition pumps. API 610 was later adopted by ISO and designated as ISO 13709. The Second Edition (and beyond) still applies to the API 610/ISO 13709 pumps. It has also been expanded to include ANSI B73.1 and B73.2 seal chambers and ISO 3069 Frame C seal chambers. On the ANSI/ASME pumps notice that this applies only to the seal chambers (often called big bore boxes). This standard does not apply to seals designed to fit into the small stuffing boxes designed for packing.

Key Concepts One of the challenges the First Edition Task Force had was to standardize a number of concepts in the sealing industry. Up to this point, every OEM and user had developed their own methods and terminology when referring to seals. We will briefly cover some of these concepts now and they will be covered in more detail later in the training program.

There are literally hundreds of different seals in use today. API 682 defines three basic seal types that are used in this standard. These definitions include design details as well as materials of construction.

Seal arrangements define the number of seals, orientations of the seals to each other, and function of the seals. The First Edition allowed only three basic seal arrangements. The Second Edition expanded this greatly due to the addition of new seal types.

Seal categories was a new concept introduced in the Second Edition. A seal category is a sub-specification that defines the seal, its use, its applicable pump type, and documentation requirements.

While the First Edition did not cover the design of the component parts of a mechanical seal, it did address many specific design features. The Second Edition continued with the same requirements and adds additional design details for the new seal types.

API-682 seals are designed to meet a minimum of three years of uninterrupted service. The question the Task Force faced was how the standard would give the end user the confidence level that these seals can achieve this goal. The answer was to qualify all seals in a well defined test program that, in some ways, simulated the operating conditions seen in a pump. This included defining the test medium, conditions, and documentation requirements.

One of the most important aspects of seal applications is initially selecting the correct type of seal and piping plan. The First Edition introduced a structured selection process where the user followed a series of tables and flowcharts to arrive at a seal selection. The Second Edition expanded this concept with additional details to cover the new seal types and piping plans.

Earlier we learned that 682 is designed to default to a single solution but that, if applicable, other alternatives would be offered. Where an alternate selection is available, it viewed as technically equivalent to the default selection.

API 682 was the first document to address many of these key concepts. In doing so, it became more than a simple standard. It became a standard, a tutorial, and a textbook on mechanical seal applications.

Seal Types Over the years, seal companies have released literally hundreds of seal designs and variations. Surprisingly, there has been very little effort to standardize seal designs, materials, dimensions, or even their interfaces into a pump. There are some German standards that define interface between component seals and pumps as well as some ANSI, API, and ISO efforts to define a standard seal chamber. Still, the design of seal chambers and mechanical seals has largely been in the domain of the OEMs.

One of the challenges for the API 682 Task Force was to create standard seal types that would define the basic seal design, materials of construction, minimum installation envelope, and operating windows.

A Seal Types is a basic description of the seal. Historically people used terms like spring pusher, bellows, multi- spring, single spring, rotating, and stationary to describe a seal. They would also add other design features such as high balance, multi-port, or distributed flush to further define it. Then to define the materials, they would need to specify the materials for all of the major components. This was an inefficient means of referencing a specific seal.

The Type A seal has a rotating flexible element, multiple springs, and O-ring secondary seals. The figure on the left shows the default configuration where the springs are rotating with the shaft. The figure on the right shows an alternate arrangement where the springs are stationary with the seal gland. This stationary design may be required in higher speed applications.

The default face materials for the Type A seal are Silicon Carbide versus premium grade blister resistant carbon. The standard O-ring materials is a fluoroelastomer (or FKM) such as Viton. The default spring material is Alloy C-276. There is an option where a 316SS single coil spring can be used. The other metal parts such as the sleeve, gland, and spring holder are 316SS. A throttle bushing in the gland is required for all single seals.

Note that the seal type does not designate the number of seals. This will be defined under the seal arrangement. There are also additional design details which will be defined under the seal category.

The type B seal is similar to the Type A seal except the basic seal is now a metal bellows seal. The metal bellows acts as both the spring element and the dynamic gasket.

The default configuration is shown on the left with the bellows mounted onto the sleeve and rotating with the shaft. The figure on the right shows an alternate arrangement where the bellows are stationary with the seal gland. This stationary design may be required in higher speed applications.

The default face materials for the Type B seal are Silicon Carbide versus premium grade blister resistant carbon. The standard O-ring materials is a fluoroelastomer (or FKM) such as Viton. The default bellows material is Alloy C-276. The applies only to the diaphragms of the bellows and not the adapter or face flange materials. All other metal parts including the sleeve and gland are 316SS. A throttle bushing in the gland is required for all single seals.

The default configuration is shown on the left. This is a stationary bellows with the bellows assembly attached to the gland. The rotating configuration, shown on the right, is an option and is generally used in dual seal arrangements.

The default face materials for the Type C seal are Silicon Carbide versus premium grade blister resistant carbon. The standard secondary gasket materials is a flexible graphite. The default bellows material is Alloy 718. The applies only to the diaphragms of the bellows and not the adapter or face flange materials. The face flange is generally a low expansion alloy to maintain the shrink fit to the seal face at elevated temperatures. All other metal parts including the sleeve and gland are 316SS. A throttle bushing in the gland is required for all single seals. A bronze anti-coke device is also required. This directs the seal quench (which is generally steam) towards the seal faces to exclude air and minimize coking.

Rotating vs Stationary Flexible Element Seals The default Type A and Type B seals have a rotating flexible element but can be provided with a stationary flexible element as an alternate. The default Type C seal has a stationary flexible element but can be provided with a rotating flexible element as an alternate. So, each of the seal Types can be provided with either rotating or stationary flexible elements. When should you choose one over the other?

Seal Arrangements and Configuration Codes Now that we have defined the basic seal types, we must look at the options of how these are package for a specific application. The seal arrangement defines the number of seals, their orientation, and details about their operation.

The First Edition was limited to only liquid mechanical seal. These are referred to as contacting wet seals. The Second Edition introduced two new options: containment seals (either non-contacting or contacting dry-running) and non-contacting seals (as wet running primaries or dual dry-running). We need to examine these options before we can discuss seal arrangements.

CW - Contacting Wet Seals The Contacting Wet seal is a typical liquid mechanical seal. This seal is designed to run on a liquid fluid film. This liquid provides lubrication and hydrostatic support of the fluid faces. The faces are generally flat and do not have any face features so this design does not intentionally create hydrodynamic forces to separate the faces. In a good running seal, the faces are operating with a fluid film on the order one-half a micron.

CS - Containment Seal A Containment Seal is designed as a dry running backup seal. It is always the outer seal in a dual non- pressurized seal arrangement. This seal can be either a non-contacting (lift-off) design or a contacting design.

The Containment Seal will operate under relatively low-duty conditions for the life of the seal. It will normally be exposed to only buffer gas or vaporized process fluid. Normal emissions past the primary seal are prevented from reaching atmosphere by the Containment Seal. When the inner seal fails, the Containment Seal can operate under full seal chamber conditions until the pump can be shutdown for seal replacement.

The Containment Seal is designed to run for the life of the primary seal (or at least 25,000 hours) under a maximum pressure of 10 PSI. Since the containment seal chamber is normally connected to the flare or a vapor recovery system, this is realistic. When the inner seal fails, the Containment Seal must operate under seal chamber conditions for a minimum of eight hours. This will allow for an orderly shutdown of the equipment. It was not the intention of the standard that this seal can be run indefinitely with a failed inner seal.

NC - Non-Contacting Seal The last seal design is a Non-Contacting seal. This seal can be used as a dual pressurized gas seal or as a inner seal (of a dual non-pressurized seal arrangement) running on process fluids.

The most common use for this design is in dual gas seals. Here the seals operate on a barrier gas provided from an outside source through a control panel.

The use of a Non-Contacting seal as a primary seal can be traced back to applications where the fluid on the primary seal may be impossible to keep in a liquid state.

A Non-Contacting seal is designed to create hydrodynamic forces to separate the faces under all operating conditions. This hydrodynamic lift is created by the use of shallow waves, grooves, or slots. Since these faces are separated by a greater distance than liquid seals, there is normally a higher leakage rate. These seals are also designed to run for a minimum of 25,000 hours.

This chart shows the available Arrangements and Configurations under API 682 Second Edition. The First Edition allowed only three options. The Second Edition has grown to eleven options due to the expansion of the scope and addition of new seal types.

The second column is for Arrangement 2 seals. These are two seals in series with a containment seal chamber pressure less than seal chamber pressure. These are also called a dual unpressurized seals. There are three configurations available for this arrangement depending upon the state of the barrier fluid and the design of the primary seal.

The third column is for Arrangement 3 seals. These seals are operated with a barrier maintained at a pressure above the seal chamber pressure. These are also called dual pressurized seals. Under Arrangement 3, the column on the left is for seals operating with a liquid barrier fluid while the column on the right is for seals operating with a gas barrier fluid. The configurations shown in each column describe the orientation of the two seals.

Arrangement 1 • 1CW-FX or 1CW-FL configuration • Single mechanical seal • May have a fixed or floating throttle bushing • May have single point or distributed flush

The Arrangement 1 seal is a single contacting wet seal. There is only one seal per cartridge. The design features on the illustration is only meant to show the basic seal and orientation. Some of the features shown may or may not be required depending upon other parts of the standard. For example, the bushing may be either a fixed or floating bushing and the flush may be either a single point or distributed (multiport) injection.

This would be a good point to look at the configuration nomenclature. For Arrangement 1, there are two configurations. These are designated as 1CW-FX and 1CW-FL. The first digit, “1”, defines this as an Arrangement 1 seal (or single seal). The next two digits, “CW”, define this as a Contacting Wet seal. The final two digits indicate whether the seal has a fixed (“FX”) or floating (“FL”) bushing.

Arrangement 2 • 2CW-CW configuration • Dual non-pressurized seal with a liquid buffer fluid • Same as the First Edition Arrangement 2 seal

There are several variations of the Arrangement 2 seal but all of them have one thing in common – the buffer fluid (liquid or gas) is maintained at a pressure lower than the seal chamber pressure.

The first configuration we will look at is the “2CW-CW” configuration. This seal is an Arrangement 2 (the first digit) with the inner seal as a Contacting Wet seal (the next two digits) and the outer seal as a Contacting Wet seal (the last two digits). Basically, this is a dual non-pressurized seal with a liquid buffer fluid.

Arrangement 2 • 2CW-CS configuration • Contacting wet seal with a dry running containment seal • Containment seal may be either contacting or non-contacting

The 2CW-CS configuration is an Arrangement 2 seal with a Contacting Wet inner seal and a dry-running Containment Seal (“CS”) for the outer seal. This is the traditional liquid inner seal with a dry running backup seal. The Containment Seal may be either a contacting or non-contacting design.

Arrangement 2 • 2NC-CS configuration • Inner seal is designed to be non- contacting and operate with liquid, vapor, or mixed phase process • Outer seal a containment seal

The 2NC-CS configuration is an Arrangement 2 with a Non-Contacting inner seal and a Containment Seal for the outer seal. The inner seal is designed to be non-contacting and can operate on either a liquid, vapor, or mixed phase process. The outer seal is a Containment Seal.

This configuration requires a little more background. In most cases, the inner seal of an Arrangement 2 seal is a Contacting Wet seal running on the liquid process fluid in the seal chamber. Because the seal is designed to run on a liquid, the standard requires that the pressure in the seal chamber is greater than the vapor process fluid. To insure that it stays a liquid, the vapor pressure margin should be on the order of 50 PSI.

In most cases this can be achieved with the proper piping plan. In some cases though, the vapor pressure margin may be impossible to maintain. This is especially true in service with very light hydrocarbons. For these applications a Non-Contacting inner seal can be designed to operates on the vapor phase process fluids. When there is mixed phase or full liquid phase in the seal chamber, the inner seal will also operate but with higher leakage rates.

All leakage past the inner seal is prevented from going to atmosphere by the Containment Seal. The Containment Seal chamber is vented to a vapor recover system. This configuration has seen only limited applications in the field.

Arrangement 3 Liquid Seals • 3CW-FB configuration • Contacting wet seals oriented in a series (or face-to-back) orientation • Default Arrangement 3 liquid seal • Same as the First Edition Arrangement 3 seal

Arrangement 3 seals are dual pressurized seals with the barrier fluid maintained at a pressure higher than the seal chamber pressure. There are two major subdivision under this arrangement – those with a liquid barrier and those with a gas barrier.

The 3CW-FB configuration is an Arrangement 3 seal with Contacting Wet seals (that is a liquid barrier fluid) in a series or face-to-back (“FB”) orientation. This is also called a dual pressurized liquid seal. The face-to-back configuration is the default configuration for the standard. This means that it is the preferred orientation of the seals. This is also the Arrangement 3 configuration described in the First Edition.

The reason the face-to-back orientation has been selected as the default has to do with the failure mode of the seal. If the outer seal fails and there is a loss of barrier fluid and pressure, the inner seal will be OD pressurized and the inner seal will function as a single seal.

Other orientations are available in Arrangement 3 liquid seals. The 3CW-BB (back-to-back) or 3CW-FF (face-to- face) orientations are also acceptable. This may be required for specific applications or pump designs.

Arrangement 3 Gas Seals • 3NC-BB configuration • Default Arrangement 3 gas seal • Non-contacting gas seals in a back-to-back configuration

The other major subcategory under Arrangement 3 is the gas barrier fluid seals. These are also called dual gas seals. These have seen widespread use throughout the refinery and chemical industries since the introduction of the First Edition.

The 3NC-BB seal is the default Arrangement 3 gas seal. This is an Arrangement 3 Non-Contacting seal in a back-to-back orientation. This has been the most widely used orientation for these seals.

Other orientations are also recognized by the standard. These alternates include the 3NC-FF (face-to-face) and 3NC-FB (face-to-back) orientation. As with the liquid seals, there may be applications where these alternate designs are more suitable.

Categories One of the biggest complaints of the First Edition was that it specified a seal that was designed with all of the features required for severe duty in a hazardous service. While this addressed many of the needs of a refinery, it proved to be overkill for low duty application. The end users and Task Force recognized that different applications may require different levels of seal sophistication.

Until the release of the Second Edition, this was handled by users specifying “modified” API-682 seals. This lead to such requests as “design it like a 682 seal except without the…” or “design it in the spirit of 682”. This defeated some of the benefits of having a standard.

With the inclusion of more pump types (with smaller seal chambers) many of the required features may not physically fit in the smaller installation envelope.

And last but not least, the users recognized that the new seals were often more expensive than non-682 seals. If the extra features improved seal performance, this could be justified. If the extra features were not required, it became more difficult to use the new seal.

All of these factors lead the Task Force to consider creating sub-specifications within the 682. These would describe seals for different levels of severity, operating windows, design features, and documentation. These have been designated as seal Categories.

Category 1 seals are designed for general duty services. They are to be installed into the smaller chemical duty pumps in lower pressure and temperature applications.

Category 2 seals are similar to the seals defined in API-610 7th edition. These are heavy duty refinery seals used in API 610 pumps. They do not however require all of the features of the API-682 First Edition seals.

Category 3 seals are for heavy duty services requiring all of the features necessary for severe applications. This is essentially the same seal that was defined in the First Edition.

Here is a chart showing a comparison of some of the features of the three seal Categories. This is taken from Annex A of the Second Edition. You need to study this in detail but we’ll go over it briefly now.

Category 1 seals are designed for the ANSI/ASME B73.1 and B73.2 big bore seal chambers as well as the ISO 3069 Frame C seal chambers. The Category 2 and 3 seals are for API-610 pumps.

The temperature range for the Category 1 seal goes up to 260°C (500°F) while Categories 2 and 3 go up to 400°C (750°F). Category 1 seal have applications up to 22 bar (315 PSIA) while Categories 2 and 3 are up to 42 bar (615 PSIA).

The default face materials for Category 1 seals are direct sintered SiC vs Carbon. This is because these seals will likely be exposed to more corrosive environments in chemical pumps. The default material for Categories 2 and 3 is reaction bonded SiC vs Carbon.

Distributed flush is required for Category 3 seals. The default for Categories 1 and 2 is a single point injection unless the users specifies a distributed flush or there in inadequate vapor pressure margin in the application. The criteria to determine this is in the standard.

All seals require the gland to make metal-to-metal contact with the seal chamber face. In a Category 1 seal, it is only necessary to have contact inside the stud circle. Categories 2 and 3 require contact both inside and outside the stud circle.

While there are some specific shaft sizes used in the ANSI/ASME and ISO pumps, there is some variation in what is actually supplied by OEMs. For this reason, there are no defined seal shaft sleeve increments for Category 1 seals. Category 2 and 3 seals are designed for the 10mm shaft size increments used in API-610. In practice, the seal OEMs will supply seals in whatever size the customer orders.

Category 1 single seals require a fixed Carbon throttle bushing in the gland. A floating bushing is optional. The Category 2 seal requires a fixed non-sparking metal bushing with a floating Carbon bushing as an option. A Category 3 seal requires a floating Carbon bushing.

We will be discussing seal qualification testing in a later module. For now, note that Category 3 seals require testing as complete assembly. Category 1 and 2 seals can be designed from components that have been previous qualified in different tests.

The remainder of the differences apply to the level of documentation required for each seal. Categories 1 and 2 require minimal documentation to help reduce the cost to both the user and the OEM. Category 3 require extensive documentation from both the user and the seal OEM.

While the concept of Categories introduces a level of complexity to the standard, ultimately they will allow the most appropriate seal to be applied for a service without introducing unnecessary features, costs, or documentation.

Dimensions API 682 Second Edition was been written as an international standard. The use of metric units through the standard as well as the entire formatting of the document was directed towards its release as an ISO 21049.

This document has focused on the use of SI units. This trend began in API 610 8th Edition and API 682 First Edition and has being carried on in the Second Edition and beyond. For the standard to truly be accepted as an international standard this is necessary. It is also necessary to respond to the needs of countries using US Customary units

To address both of these needs, the Second Edition and beyond allows the purchaser to specify whether their order will be provided in SI or US Customary units. This includes all data, drawings, hardware, fasteners, and other equipment.

For most items such as drawings or data sheets, these can easily be (or, in some cases, already are) provided in dual units. Hardware issues such as fasteners will be more difficult to address. Some OEMs will likely provide user interface fasteners (such as drive collar set screws) in the units requested while the internal fasteners on the seal remain as originally designed.

Design Requirements One of the primary goals of the standard is to specify seals that have proven to be successful. One of the ways of achieving this is by specifying design requirements for the seals. The standard does this in three sections - general design requirements (which apply to all seals), category specific requirements (which may be different between the three categories), and arrangement specific requirements (which cover the different seal arrangements and configurations).

API 682 contains literally hundreds of details on features required on an API 682 seal. Yet the First Edition states that the “standard does not cover the design of the component parts of mechanical seals…” Ironically, this statement is followed by 16 pages of specifications that directly affect the design of seal components. The Second Edition and beyond follow the same path and contains even more specifications on seal design.

What the First Edition Task Force was really saying is that the detailed design of seal components is up to the seal OEMs. The selection of stress levels, deformation limits, the seal balance, the selection of manufacturing methods, and many other design decisions are entirely up to the OEM. The Task Force did, though, have a great deal of experience on what seals features worked in actual services. The requirements in this standard are an attempt to capture design features that have proven to be successful in the field. During the development of all of these standards, Task Force members from the major seal OEMs were present and provided guidance and buy-in to these requirements.

All mechanical seals will be cartridge seals. Cartridge seals slide onto the shaft as a complete assembly and do not rely on the position of the shaft to set the seals. Component seals are not allowed. Hook sleeves are not allowed. Hook sleeves with a snap ring (pseudo-cartridges) are not allowed.

The default configuration for Type A and B seals are with a rotating flexible element. If specified, these can also be provided with a stationary flexible element as shown in the figure on the left. The default Type C seal has a stationary flexible element. If specified, it can be provided with a rotating flexible element as shown in the figure on the right.

In either case, all seals where the seal faces surface speed is greater than 4500 ft/min (or 23 m/s) will be provided with stationary flexible elements.

Seals must be designed to handle both normal and transient motion of the pump shaft. This is seen primarily as a concern in between bearing, high-temperature pumps. This can also be seen in vertical pumps or other designs that rely on motor bearings for axial shaft positioning.

The sealing surfaces around O-rings are required to have minimum surface finishes. For dynamic gaskets (such as balance shoulders), the finish must be a minimum of 32 microinches Ra. For static gaskets, it must be a minimum of 63 microinches Ra. Corners or steps must be chamferred or radiused to prevent O-ring damage during installation. All O-ring grooves must be sized to allow for the expansion of perfluoroelastomers.

For vacuum services, the seal design shall insure that all components will be positively retained against becoming dislodged. Under these conditions, the faces must also remain in contact and not open up.

The minimum radial clearance between a rotating and stationary components will be 3mm (1/8 inch). There are several exceptions to this. Pumping rings and containment seal bushing may have a minimum clearance of 1.5mm (1/16 inch). Throttle and throat bushing may also be tighter depending upon design.

Seal glands must be designed for the MAWP of the pump. Unless specified, the gland shall have bolt holes and not slots. All stationary seal faces must be supported by a shoulder with a minimum thickness of 3mm (1/8 inch).

Seal OEMs must design the seals to be tolerant of a perpendicularity between the shaft and seal chamber face of 0.5 micron/mm (0.0005in/in) of seal chamber bore. There is a recognition that some multistage pumps that experience shaft sag under static conditions may not be able to meet this requirement.

Seal chamber conditions must prevent the flashing of process fluids. The standard states that the seal chamber pressure shall be not less than a 30% margin between the seal chamber pressure and maximum fluid vapor pressure. Alternately, there must be 20ºC (36ºF) product temperature margin based on maximum fluid temperature. This means that if the fluid temperature were to increase by 20ºC (36ºF), the fluid would still not flash under seal chamber conditions. The standard also outlines remedies if these conditions can not be met. This includes using cooling, an external flush, and a close clearance throat bushing. Under any circumstances, the seal chamber pressure must be maintained above .35 bar (5 PSI) under operating conditions.

Since there has been an increase in the number of configurations and the function of the seals, the Second Edition introduced significant changes in the connection port requirements. The chart from the standard has been broken into three slides to show the required details of the connections.

The chart is divided to columns showing the applicable seal configuration, required symbol, the function of the port, the radial location of the port when viewed from the driver, the size requirement of the port, and whether the port is always required or required only when specified.

Most of the connection symbols and locations are the same as the First Edition. One of the differences is found in dual seals. Connection designations have changed from BI and BO (buffer in and buffer out) to LBI and LBO (liquid buffer in and liquid buffer out).

The size requirements of the connections have also changed and are now a function of the seal category and shaft size. There is still a differentiation between the size of connections intended for process fluids and connections to the atmospheric side of the seal.

The containment seal drain (CSD) is intended to allow for liquid phase or mixed phase process fluids to drain from the bottom of the containment seal chamber.

The containment seal vent (CSV) is located at the top of the containment seal chamber and will allow vapor phase process to be piped off to flare or a vapor recovery system.

The gas buffer inlet (GBI) is used to provide a inert gas sweep of the containment seal cavity and to help isolate the containment seal faces from process leakage.

Barrier fluid connections designate whether the connection is for liquid or gas. LBI and LBO designate liquid barrier inlet and liquid barrier outlet. GBI and GBO designate gas barrier inlet and gas barrier outlet. In practice most dual gas seals are run dead-ended and the GBO port will be plugged.

It is important to note the angular location of the connections given in these charts. At first, this may be interpreted as the location of the port on the outer diameter of the seal gland. This is not the intention of the standard. The location designates where the connection though-hole breaks into the ID of the seal gland. This may be into the seal chamber, the containment seal chamber, or the buffer/barrier fluid chamber. The connections are often required at these locations to allow for venting or to promote thermosyphoning of the fluid. The actual location of the port on the OD of the gland may be angled to provide a tangential outlet or to avoid pump obstructions.

Additional design requirements include the need to plug all connections in the gland. This is intended to prevent a user from inadvertently leaving a connection opened during commissioning of the seal. Plugs must be solid plugs made out of the same material as the gland and in accordance with ASME B16.11.

Since the glands and connecting piping are considered to be pressure containing parts of the sealing system, all connections must be suitable for the MAWP of the seal chamber or gland plate.

Sleeves provided on all mechanical seals are to be provided by the seal OEM. The First Edition issued requirements that the clearance between the sleeve bore and shaft OD shall not be more than 0.003 inches (including tolerances). This created some problems with seal installation and removal of seals in the field. The Second Edition attempts to improve this situation by setting sleeve clearances based on shaft diameter. The standard used ISO 286-2 F7/h6 which ranges from 0.020mm to 0.093mm (0.0008 inch to 0.0037 inch) depending upon the shaft diameter.

Sleeves with O-rings shall be sealed at the impeller end of the sleeve. Sleeves that rely on mechanical compressed flexible graphite gaskets shall be sealed at the bearing end of the sleeve and the gasket shall be captured between the sleeve and shaft.

To help prevent unnecessary seal run out, the bore and the OD of the seal sleeve must be concentric within 25 microns (0.001 inch). The sleeves shall be piloted near both ends with the center of the bore relieved. Drive collars set screws should not pass through the piloted area of the sleeve since deformation of the shaft under these screws would make removal of the seal more difficult.

Other design requirements such as the use of single springs on Type A seals and the exclusion of lapped joints for sealing seal faces are included in the standard.

The standard defines default materials for all major seal components. Seal faces shall be carbon versus silicon carbide or silicon carbide versus silicon carbide. Most metal components (other than bellows diaphragms and springs) are 316 stainless steel or its equivalent. Type B seals require Alloy C-276 bellows and Type C seals require Alloy 718 bellows.

There are alternative material stated for many components. Additionally, for chemical compatibility reasons, more exotic metallurgy or materials in the pump may require the seal design to also upgrade to more corrosion resistant materials.

Category 1 The standard seal flush for a Category 1 seal is a single point injection. On Arrangement 1 and Arrangement 2 seals with rotating flexible elements, the purchaser may specify a distributed flush arrangement. Additionally, if there is inadequate vapor pressure margin for the application, a distributed flush arrangement may be required by the standard.

Gland gaskets must be confined. This requirement eliminates the use of full face flat gaskets. In addition, only controlled compression gland gaskets such as O-rings or spiral wound gaskets are allowed. Upon installation, the gland must come into metal-to-metal contact with the seal chamber face.

Category 2 The standard seal flush for a Category 2 seal is also a single point injection. On Arrangement 1 and Arrangement 2 seals with rotating flexible elements, the purchaser may specify a distributed flush arrangement. Additionally, if there is inadequate vapor pressure margin for the application, a distributed flush arrangement may be required by the standard.

Gland gaskets must be fully confined in a groove. In addition, only controlled compression gland gaskets such as O-rings or spiral wound gaskets are allowed. Upon installation, the gland must come into metal-to-metal contact with the seal chamber face both inside and outside the gland stud circle. This requirement minimizes the potential to distort the gland during tightening of the gland nuts.

Category 3 Category 3 seals share the same requirements as Category 2 with the exception that a distributed flush is required on all Arrangement 1 seals with rotating flexible elements.

All seals must also have a throttle bushing. For Category 1 seals, the default design has a fixed carbon bushing. If specified, a floating carbon bushing shall be provided.

For Category 2 seals, the default design has a fixed, non-sparking, metal throttle bushing. If specified, a floating carbon bushing shall be provided.

Arrangement 2 - General Arrangement 2 seals are designed with two seals in a face-to-back orientation and with a buffer fluid cavity maintained at a pressure less than seal chamber pressure. In the First Edition, a contacting wet seal with liquid buffer fluid (2CW-CW) was the only option. In the Second Edition, there are additional options.

The default inner seal for all Arrangement 2 seal is a contacting wet (CW) seal. Since the buffer fluid cavity is almost always connected to a flare or vapor recovery system, the inboard seal must be designed to handle pressure upsets in the barrier fluid. In inner seal must be designed to withstand a reverse pressure differential of 2.75 bar (40 PSI).

Where possible, the seal sleeve shall be designed as one piece. Designs that utilize an auxiliary sleeve (or adapter sleeve) on the inboard are acceptable. Auxiliary sleeves are often used to aid in the assembly of the seals or to allow common seal sizes to be used for the inner and outer seal.

Arrangement 2 - 2CW-CW A 2CW-CW configuration is a dual seal in a face-to-back orientation with a contacting wet inner and outer seal and a liquid buffer fluid.

For Category 3 seals, tangential buffer fluid connections are required. For Category 1 and 2 seals, tangential connection may be required (as determined by the seal OEM) or specified by the purchaser.

Arrangement 2 - 2CW-CS and 2NC-CS In configurations that use a containment seal (2CW-CS or 2NC-CS), the containment seal cavity will be exposed to leakage that comes across the primary seal. To help isolate the containment seal from this leakage, a fixed, non-sparking bushing shall be provided between the CSV/CSD and the containment seal faces. Leakage is then directed to exit the containment seal cavity through the vent or drain.

If the seal uses a Plan 72, an inert buffer gas in injected at the gas buffer inlet (GBI) connection. This gas will flow through the narrow annulus under the bushing towards the CSV/CSD further preventing inner seal leakage from reaching the containment seal.

The containment seal bushing shall be designed so that the minimum radial clearance between the bushing and rotating seal components is 1.5mm (0.060 inch).

Arrangement 3 - General Arrangement 3 seals are dual seals where the barrier fluid is maintained at a pressure higher than the seal chamber pressure. The barrier fluid may be a liquid or a gas. The inner seal in all Arrangement 3 configurations must be designed so that the inner seal will withstand reverse pressure without opening. The default design requires that the seal consist of two seal rings and two mating rings. If it is recommended by the seal OEM and approved by the user, a common mating ring (or rotor) may be provided.

Like Arrangement 2 seals, Arrangement 3 seal sleeves shall be designed as one piece where possible. Designs that utilize an auxiliary sleeve (or adapter sleeve) on the inboard are acceptable.

If specified, a flush connection into the seal chamber shall be provided. This may be required to provide an external flush to isolate the seal chamber. In 3CW-FB configuration, an injection onto the inner seal (Plan 11) would also help remove heat from the inner seal in the event of a loss of barrier fluid.

Arrangement 3 - Liquid Barrier Fluids 3CW-FB, 3CW-BB, and 3CW-FF The buffer fluid system for Arrangement 3 liquid seal shall be designed so the maximum temperature differential (or temperature rise on the system) shall be 8ºC (15ºF) for glycol/water or diesel fluids and 16ºC (30ºF) for mineral oil fluids. The differential temperature is a function of many things such as barrier fluid properties, pump operating condition, reservoir design, and cooling water conditions.

For Category 3 seals, tangential buffer fluid connections are required. For Category 1 and 2 seals, tangential connection may be required (as determined by the seal OEM) or specified by the purchaser.

The default configuration for Arrangement 3 liquid seals is 3CW-FB (face-to-back orientation). 3CW-BB (back- to-back) and 3CW-FF (face-to-face) are acceptable alternate configurations.

Arrangement 3 - Gas Barrier Fluid 3NC-BB, 3NC-FF, and 3NC-FB Arrangement 3 may also be provided with a gas barrier fluid. The default configuration for Arrangement 3 gas seals is 3CW-BB (back-to-back orientation). 3CW-FF (face-to-face) and 3CW-FB (face-to-back) are acceptable alternate configurations.

Seal Chamber Interfaces During the revisions to API 610 and API 682, the task forces decided to remove duplication between the two standards. To achieve this, API-610 removed almost all of the seal references. Likewise, API 682 removed almost all pump references.

The only pump requirements that remain in API 682 Second Edition and beyond pertain to interfaces between the seal and the pump seal chamber. These remain since the are applicable to all pumps (including the newly incorporated ASME and ISO pumps) and they greatly affect the performance of the mechanical seal.

Perpendicularity between the pump shaft and the face of the seal chamber must have a TIR less than 0.5 micron/mm (0.0005 in/in) seal chamber bore. This is measured by attaching a dial indicator to the shaft and reading the total indicator reading through one complete revolution.

Concentricity between the pump shaft and the seal chamber pilot diameter must be less than 0.125mm (0.005 in). This is measured by attaching a dial indicator to the shaft and measuring the total indicator reading through one complete revolution of the shaft.

Accessories Accessories are any components in the seal system (other than the seal) that are required to create an acceptable sealing environment. This can be a great number of different components. The standard specifically covers the accessories listed below:

Auxiliary piping systems Cyclone separators Orifices Seal coolers Reservoirs Pumping rings Condensate collection reservoirs Gas supply panels

Auxiliary Piping Systems Auxiliary piping systems address the requirements for piping, tubing, and fittings used to connect the seal to another accessory or an outside utility. Example of the include piping used to connect the seal to a barrier fluid reservoir or seal cooler. It also includes cooling water piping to reservoirs and seal coolers.

The standard divides up piping systems into three groups. Group I covers seal flushes and other services exposed to the process fluid or barrier/buffer fluids. Group II covers piping requirements for steam injections, water injections, quenches, quench vents/drains, and inert gas quenches. Group III cover cooling water systems to support any other accessory.

Piping shall comply with ANSI B31.3 Seal flush and barrier fluid piping is considered part of the pressure containing components and shall be rated for the MAWP of the pump casing. Piping systems shall be designed so that air pockets are eliminated by manually venting at high points or by designing the system to be self venting. In additionally, the piping must be completely drainable without disassembly of the piping or any accessory. Plan 23 systems must include a permanent stainless steel tag which describes the importance of completely venting the system. Barrier and buffer fluid systems require some means of forced circulation. This can be a pumping device integral with the mechanical seal or an external circulation pump. Designs that rely on internal pumping rings should be designed so that the inlet into the seal gland is at the bottom of the gland and the outlet at the top of the gland. Systems that rely solely on thremosyphoning are not allowed.

Cyclone Separators The first accessory covered in the standard is the cyclone separator. Cyclone separators are used in piping plans 31 and 41. The purpose of a cyclone separator is to remove solid contaminants from the seal flush and provide a better environment for the seal.

Flow Control Devices Orifices are used to control the flow of fluid in seal flush systems. The number and size of orifices is to be determined the vendor supplying the auxiliary piping system.

Seal Flush Coolers Seal coolers are used to reduce the temperature of a seal flush to improve the operating environment of the seal. These components are specifically called seal coolers since the term “heat exchanger” is reserved for larger pieces of process equipment.

Seal coolers shall be designed so that seal flush (or process fluid) is on the tube side of the cooler. The cooling water (or other cooling medium) is on the shell side.

Seal coolers shall be designed so that both the tube and shell side can be completely vented and drained. The shell side shall be equipped with a service valve on at the low point to allow flushing of the cooling water.

Barrier/Buffer Fluid Reservoirs Reservoirs are used to contain and condition barrier and buffer fluids on dual liquid seals. The standard contains many specific requirements for features, dimensions, volumes, and materials. Examples of these include:

A separate reservoir is required for each seal. The height of the normal liquid level shall be at least 1m (3 ft) above the gland plate of the seal. All connecting piping must be continually sloping upward to the reservoir and use smooth, long radius bends. All reservoirs shall have a pressure switch and pressure gauge to monitor the pressure above the fluid level in the reservoir. A low level alarm switch is also required. A high level alarm switch is optional.

One of the changes introduced in the Second Edition was the addition of a new reservoir size. The First Edition required that all reservoirs have a minimum 20 l (5 gallons) fluid capacity at the normal liquid level. The Second Edition allowed the use of smaller fluid capacity for smaller seals. For shaft diameters over 60mm (2.50 inch), the volume shall be a minimum of 20 l (5 gallons). For shaft diameters 60mm (2.50 inch) and smaller, the minimum fluid capacity is 12 l (3 gallons).

Condensate Collection Reservoir The condensate collection reservoir is used to collect leakage from a containment seal cavity. The reservoir is used specifically in the new Plan 75. The purpose of the reservoir is to collect the leakage, allow the liquid and gas phases to separate, and pipe the leakage to the appropriate liquid and vapor recovery systems. The reservoir is also used to monitor the performance of the inner seal and provide an alarm for inner seal failure.

Since leakage from the containment seal cavity will drain to the reservoir, the interconnecting piping shall slope continuously downward towards the reservoir. If the leakage solidifies at ambient temperatures, the interconnecting pipe shall be suitably heat traced and insulated.

Barrier / Buffer Gas Supply Panels Barrier and buffer gas supply panels are used to condition, regulate, and monitor the supply of gas to a containment or dual gas seal. Since the customer requirements can be varied on these panels, the purchaser and seal OEM shall agree on the instrumentation and general layout.

The system must contain the following components as a minimum: an isolation valve, coalescing filter, pressure regulator, flow meter, low pressure switch, pressure gauge, and check valve. The pressure gauge is mounted as one of the last components so that it more accurately measures the gas pressure to the seal. A high flow switch is optional.

Inspection, Testing, and Preparation for Shipment Instrumentation, testing, and preparation for shipment contains all of the requirements dedicated to insuring the seal meets customer satisfaction. The requirements range from inspection at the time of manufacturing through the final shipment to the customer.

General inspection requirements include all of the purchaser’s rights to access to the seal OEM and subcontrac- tors facilities as well as rights to participate in any inspections or testing.

Inspection of seal components contains all of the provision for various forms of NDT including radiographic, ultra- sonic, magnetic particle, and liquid penetrant. These inspections are generally applicable only to welding or cast- ing inspections.

The next three topics will be covered in considerably more detail. Qualification testing involves certifying the basic seal design. Air testing involves documenting the seal’s condition at the time of shipment. Pump OEM test- ing covers concerns about seal performance during pump testing.

Qualification testing is intended to subject the seal to a set of conditions that that will simulate operation in the field. Many test programs in the lab are performed under ideal conditions. The users on the 682 Task Force were concerned that these tests should simulate real world conditions. This includes realistic fluids, pressures, temperatures, and operating cycles.

In the end, the goal of the qualification testing is to provide the user with a level of confidence that the seal will perform as required by the standard.

Qualification testing is intended to qualify a seal model. Testing for a specific seal model will only need to be done once. It is clearly stated in the standard that the seal will be tested as it will offered for sale to the industry. The face materials, balance, spring loads, and other design features are all considered as part of the seal model. If any of these are changed, the seal will need to be retested before it can offered as a 682 compliant seal.

Since the testing will qualify an entire seal model or line, testing is required for different sizes. The standard covers a range of shaft diameters from 20mm (0.75 inch) to 110mm (4.3 inch) so the Task Force thought it would be most representative to test one seal from the smaller end of the range and one from the larger end. The First Edition stated that a 2 inch and 4 inch seal needed to be tested. Since there is no industry standard definition of seal size, the Second Edition requirements were rewritten based on the seal balance diameter. A small seal with a balance diameter from 50 to 75mm (2 – 3 inches) and a large seal with a balance diameter from 100 to 127mm (4 – 5 inches) must be tested.

Testing requirements are different between the different seal categories. In the First Edition, all seals needed to be tested as they were being offered for sale. This requirement was put into place to assure the user that they were purchasing a seal that was practically identical to the design qualified under the test program.

In the Second Edition, Seal Categories were introduced and this affected the testing requirements for the seals., All Category 3 seals share this same requirement as the First Edition. Category 3 seals must be tested in the same configuration as is being offered to the purchaser. There can be no significant changes between the tested seal other than changes in size or adaptive hardware required to fit the pump.

Category 1 and 2 seals have a less stringent testing requirement. The seals still need to be tested but there is an option. The seals may be tested in the same configuration as it is offered for sale. Alternatively, the seal may be designed with seal faces that have previously been qualified in other testing. This means that a seal OEM could take a set of seal faces from a previously qualified seal, repackage it (change the spring type, the spring holder design, the stator support, etc.), and still offer it as a qualified seal.

Another provision of the standard designed to minimize testing requirements concerns face materials. When a seal has been tested with a specific mating pair (that is materials for both seal faces), that mating pair may be applied to other previously qualified seals for that service without additional testing.

Liquid Seal Testing So, how does a person develop a realistic test program for mechanical seals. The First Edition Task Force started by identifying a number of typical refinery applications categories based of the process fluid, the temperature, and the pressure. These would encompass the majority of sealing applications in a refinery. They then selected five test fluids that were representative of the application groups. One of the important considerations was that the test fluids would be practical and safe to use in a laboratory environment.

After selecting the fluid, the next step was to develop an effective test program. It was important to demonstrate that seal would work during long term, steady- state operations. It was equally important to demonstrate that the seal would tolerate the multiple starts and stops seen in service. Pump operating conditions are also subject to variations or upsets in pressure and temperature so the test conditions should simulate these.

In the end, the Task Force developed a set of test parameters for liquid seals that would build confidence that the seal would function reliably in actual serve.

The seal OEM must determine the intended application for a mechanical seal. Let’s say that a fictitious seal model is being sold into the market and is intended to be used in water, sour water, and non-flashing hydrocarbons between 20 and 500F (or up to 750F for ISO 21049 and the Third Edition). The seal OEM would examine the chart and see that the seal must be tested on water and mineral oil. If the seal was also sold for flashing hydrocarbon services at ambient conditions, the seal would also need to be tested on propane.

General duty seal that are intended for many applications will require testing on all fluids. Seals designed for specific purposes (such as high temperature bellows) will require less testing.

The testing cycle was designed to simulate start-ups and shut-downs as well as variations in operating conditions that mat be typical for a mechanical seal in a real application. This chart shows the qualification test cycle for liquid seals. The vertical axis shows the shaft speed (in RPM). Either the seal is static (at 0 RPM) or dynamic (at 3600 RPM). The horizontal axis is for test time. Note that this is not to scale!

The test begins with the seal being started under a set of pressure and temperature conditions called the base- point. The base point is different for the different test fluids. The seal reaches steady state conditions and is allowed to operate for a minimum of 100 hours. The seal is then stopped and maintained statically under base point conditions for a minimum of four hours. Each time the test reaches an asterisk on the time line, critical data needs to be recorded onto the test qualification form.

The seal now begins the cyclic phase of the testing. The seal is started and operated at 3600 RPM and allowed to reach equilibrium. The seal is then subjected to variations in the pressure and temperatu