barrier fluid for mechanical seal in stock

Lubriplate Barrier Fluids are ultra-clean, polyalphaolefin (PAO) synthetic based fluids recommended for all types of mecahnical seals. While they are NSF H1 registered food grade, they may be used for all applications requiring barrier fluid for mechanical seals.

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DRYDENE SYTHETIC BARRIER FLUID A5 is designed to cool and lubricate the seal face of double and tandem mechanical seals. It may be also be used in certain food processing machinery applications where incidental contact with food may be considered safe (see FDA CFR 178.3570).

​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Chesterton 662 FG is an ISO VG Grade 22 high-performance lubricant designed specifically as a barrier fluid for double mechanical seal applications. 662 FG is suitable for all industrial and food/beverage/pharmaceutical applications.  662 FG is NSF H1 registered.

The ultra-clean 662 FG delivers premium thermal stability while minimizing the abrasive-particle wear of the seal faces and extending equipment ​life.

Wenzhou Landmark Seal Manufactuing Co,.Ltd is established in 2011, Producing small standard mechanical seals with quantity more than 250000 pcs per month. Our advantage is small seals with all range of stamping and rubber moulds. The production is ISO 9001 , TUV , SGS, ROHS certificated.

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As operators of pumping equipment become more focused on the safety, reliability and environmental impact resulting from shaft seal leakage, dual mechanical seals have become more prevalent in the industry. A dual mechanical seal offers a second (outer) seal to contain the pumped fluid by creating a cavity or chamber between the inner and outer seal that can be filled with a fluid. When this fluid is unpressurized, it forms a buffer between the pumped fluid and atmosphere and is commonly referred to as a buffer fluid. When pressurized, it forms a barrier between the pumped fluid and atmosphere and is known as a barrier fluid.

Although mechanical seal designs are available in configurations that use either a liquid or a gas as a barrier fluid, the following discussion focuses on liquid buffer and barrier fluids only. In addition to separating the pumped fluid from the atmosphere, liquid buffer and barrier fluids lubricate the mechanical seal and transport frictional heat and absorbed heat from the mechanical seal to a heat exchanger. This controls the fluid’s temperature and lubricating properties.

Buffer/barrier fluid can be stored, monitored and delivered using many methods. Each is identified by a piping plan number that describes the minimum requirements of each system. The most commonly referenced piping plan originates from the American Petroleum Institute’s standard API 682.

A Plan 52 system (see Figure 1) provides a reservoir that stores the buffer fluid. Supply and return lines are connected to the mechanical seal and circulation of the buffer fluid is achieved by an internal circulating device (pumping ring) within the mechanical seal. The vapor space above the buffer fluid in the reservoir is vented to atmospheric pressure typically via a flare or vapor recovery system. The reservoir can be instrumented to measure the liquid level and pressure in the reservoir. Ports are fitted to the reservoir to facilitate maintenance activities—such as inspection and cleaning or refilling and draining the buffer fluid. Cooling is accomplished using an internal heat exchanger.

Pressurized dual seal systems contain the same essential components as an unpressurized system. However, they also contain a way to pressurize the barrier fluid. The following plans may be used for pressurized dual seal systems:

Plan 53A—A pressurized gas blanket in the reservoir pressurizes the fluid. Nitrogen is normally used and the pressure is controlled via a pressure regulator (see Figure 2). The barrier fluid is in direct contact with the pressurized gas.

Plan 53B—Pressure is generated as a nitrogen-filled bladder is compressed by the addition of barrier fluid into the bladder accumulator. The bladder prevents direct contact of the pressurized gas with the barrier fluid.

Plan 53C—A pressure amplifying piston uses pressure from within the pump (typically the seal chamber) to amplify the barrier pressure by the ratio of the area on each side of the piston. The barrier fluid is not exposed to any pressurized gas.

Plan 54—An external system is used to pressurize and circulate the barrier fluid. A Plan 54 system can be broadly classified into two groups: closed- and open-loop systems. In closed-loop systems, the barrier fluid is stored in a large reservoir and pumps pressurize and circulate the fluid. In open-loop systems, a compatible process stream is used as the barrier fluid and is circulated through the mechanical seal and returned to another point downstream in the process.

Several critical properties of a buffer or barrier fluid must be considered when making a selection. An ideal buffer or barrier fluid will have the following properties:

Water offers several benefits as a buffer/barrier fluid. Its thermal conductivity is about three times greater than oils and its specific heat is about twice that of oils, so it is good at transporting heat away from a mechanical seal. Water is inexpensive, easy to handle and store, has few seal material compatibility issues and is nonflammable. It is also compatible with many aqueous pumped solutions. Its viscosity is generally around 1 centistoke at moderate temperatures which offers low resistance to flow in the barrier system.

However, the viscosity becomes low at elevated temperatures limiting its effectiveness as a lubricant for the mechanical seal faces. Water is also susceptible to freezing during the winter months. This results in a narrow window of service and environment temperatures in which water can be used.

Generally, oils can be used in a much wider range of service temperatures. Compared to water, oils offer greater fluid stability at elevated temperatures and are not susceptible to freezing. They also provide excellent lubrication of the mechanical seal faces and, therefore, have the potential to offer longer seal life. Few compatibility issues with mechanical seal materials exist.

Oils are available in a wide range of types, compositions and viscosities. Traditional oils used in the industry include turbine oils and automatic transmission fluids. However, performance as buffer and barrier fluids has not been as successful as other oils, primarily because of the complex mixture of additives in these fluids.

Good performance can be achieved from oils with viscosity below that of ISO Grade 32 oils. High viscosities can result in damage to the mechanical seal faces, particularly when carbon is used as a face material. Paraffinic-based oils also generally perform better than naphthenic oils while synthetic oils offer even better performance. Synthetic lubricants specifically developed for use as a buffer/barrier fluid are now available in the marketplace and offer excellent performance. However, this performance is achieved at the sacrifice of cost.

We invite your suggestions for article topics as well as questions on sealing issues so we can better respond to the needs of the industry. Please direct your suggestions and questions to sealingsensequestions@fluidsealing.com.

As end users face increasingly restrictive leakage and safety regulations, a growing number are turning to multiple seal arrangements. Multiple sealing arrangements require a liquid or gas buffer or barrier fluid to operate, introducing a new factor that end users must monitor.

Below are some best practices for liquid buffer and barrier fluids. By selecting an appropriate fluid and following proper maintenance procedures, end users can promote system reliability and extend their systems’ operating lives.

In addition to process fluid, all multiple seals use an external fluid. Depending on the sealing arrangement, this external fluid is called buffer fluid or barrier fluid. American Petroleum Institute (API) Standard 682 specifies that unpressurized dual seals, also known as traditional tandem seal arrangements, use buffer fluid. Pressurized dual seals, on the other hand, use barrier fluid, which isolates the pump process liquid from the rest of the system.

When selecting a fluid, end users should weigh the pros and cons of their applications. Some common barrier and buffer fluids, which have benefits and potential risks, are:

Glycol solutions — These, which usually contain 50 percent ethylene glycol and 50 percent water, are the simplest and most common barrier or buffer fluids. Because inhibitors can come out of the solution and damage the seal faces, end users should use uninhibited glycol in these solutions instead of glycol with inhibitors, such as antifreeze. Since some areas restrict the use of ethylene glycol, end users may need to use propylene glycol instead.

Petroleum-based hydraulic, conventional gear and bearing lubricating oils — Because they are widely available, they are popular choices. However, the viscosity of these oils can cause carbon seal face blistering, particularly with oils that are Grade 32 or higher on the International Organization for Standardization (ISO) scale.

Synthetic oils specifically formulated for barrier or buffer use — These have grown increasingly popular during the last decade. These synthetics are typically polyalphaolefin-based, and they range between ISO Grade 5 and Grade 20 (approximately). Lower-viscosity synthetics are the most popular option among end users. Higher-viscosity synthetics, which are more expensive, are the best choice for applications with high temperatures or low shaft speeds.

Heat transfer fluids — Although useful in extremely high-temperature services, these fluids can pose problems because they tend to decompose and form coke, or hard carbon formations.

After choosing the correct fluid for their system, end users must maintain the fluid and the sealing environment properly to ensure peak performance. Checking the fluid each month for changes in pH, color, viscosity, consistency and the presence of solids is a good way to help promote system reliability.

While users should change their barrier and buffer fluids regularly, service life can vary dramatically. In general, fluids operating at high temperatures need changing more frequently than those at lower temperatures.

According to API 682, the allowable temperature rise is 15° F for systems with buffer or barrier fluids that are water-based, diesel or kerosene, and 30° F for systems that use mineral or synthetic oil as buffer or barrier fluids. For example, a system using oil could have an average reservoir temperature of 130° F with an outlet temperature of 115° F and an inlet temperature of 145° F.

When monitoring the decomposition of buffer or barrier fluids, end users should consider this rule of thumb for chemical reactions — the rate of reaction doubles for every 18 F rise in temperature. For example, if a barrier fluid needs changing every six months at an average reservoir temperature of 130° F, the same fluid would need to be changed every three months if the reservoir temperature is 148° F. This simple guideline can be useful for evaluating heat transfer options during system design.

In addition to temperature considerations, buffer fluids can become contaminated by the process liquid and may require more frequent changing than barrier fluids.

While selecting the proper buffer and barrier fluid is an important first step toward sealing system reliability, the following considerations also have a big effect on performance:

API 682 provides useful guidelines and default selections for standardized dual seal systems — including Piping Plans 52, 53A/B/C and 54. By combining the API guidelines with the best practices for buffer and barrier fluids described in this article, end users can keep their systems operating smoothly.

Tegra Synthetic Barrier Fluid is designed to meet the needs of a barrier fluid for dual mechanical seals per API Standard 682, Shaft Sealing Systems for Centrifugal and Rotary Pumps. Dual mechanical seals are used to control emissions of volatile air pollutants from industrial equipment. Leading seal manufacturers recommend the use of low viscosity synthetic fluids for extended seal life of API Standard 682 dual mechanical seals.

Tegra Synthetic Barrier Fluid 17 cSt has a low Volatile Organic Compound (VOC) level, so that the barrier fluid itself will not be the source of volatile air pollutants in higher temperature applications.

3CW-BB dual seal of API 682 arrangement 3 can be used in high pressure, pressure variation and vacuum applications. Internal reverse balanced seal is located inside. The high pressure seal is located outside.

DALLAS – March 7, 2016 – Hydrotex, a national manufacturer and distributor of high performance lubrication and fuel improver solutions, announced today it is introducing two new synthetic barrier fluids: Hydrotex Economy Barrier Fluid, for cost-sensitive applications, and Hydrotex Performance Barrier Fluid, for extended lubricant life and improved low-temperature fluidity. Both fluids outperform the leading competitor in providing superior lubrication and cooling for tandem and dual mechanical seals, as proven through testing by a major mechanical seal manufacturer.

For maintenance and reliability professionals in the refining, chemical processing, and food processing industries, Hydrotex Barrier Fluids ensure the performance and extend the life of expensive cartridge seals. These barrier fluids are also approved for incidental food contact under FDA Regulation CFR 178.3570, Lubricants with Incidental Food Contact and NSF H1 approval is pending.

Mechanical seals, which can number in the hundreds in a typical refinery or plant, are critical in the process of separating and controlling hazardous chemicals, maintaining the integrity of food ingredients and ensuring cleanliness and purity throughout the manufacturing processes. The reliability of each seal also safeguards worker safety and environmental compliance.

“These barrier fluids fill a performance gap,” said John Cummins, vice president, product technology. “Previously available products worked for a short time but didn’t provide long-lasting leak protection.”

Hydrotex Barrier Fluids are available through local Hydrotex representatives. To find your representative, please check www.Hydrotexlube.com or call 1-800-527-9439.

Hydrotex helps customers develop sustainable solutions designed to improve system reliability, save energy, limit pollution, extend fixed asset life, reduce maintenance costs and improve fuel efficiency. Its products and services leverage 80 years of innovation resulting in superior lubrication solutions and high touch customer service. For more information and to find your local Hydrotex consultant, contact www.hydrotexlube.com

Petro-Canada Lubricants’ PURITY FG Synthetic Barrier Fluids are advanced food grade barrier fluids formulated to deliver exceptional performance, by resisting degradation and deposit formation, and are also suitable for service in non-food grade industrial applications. These barrier fluids start clean and remain clean in the most demanding conditions.

PURITY FG Synthetic Barrier Fluid is a PAO based product formulated with specific additives to deliver exceptional protection against oxidation, corrosion, and wear. This NSF H1 registered product is designed to provide lubrication and cooling for mechanical seals to help maximize seal life.

JCI Industries, Inc. is the exclusive provider of Flowserve Fluid Sealing Devices in Kansas, Western Missouri, and Nebraska. We offer a complete line of seals including cartridge seals, dry-running seals, metal bellows, elastomeric bellows, split seals and gas barrier seals for zero emissions.We also carry bearing protection devices and seal chamber auxiliary equipment.

We stock complete cartridge and component seals for all ANSI and API pumps, and maintain over $250,000 of seal related inventory. JCI’s seals specialist has 60+ years of experience, including seal application design & recommendation, seal failure analysis, and complete seal repair and installation.

Flowserve heritage product lines include BW/IP, Pacific Wietz, Durametallic, Five Star, and Pac-Seal. BW/IP was engineered API type seal, Pacific Wietz the gas seals came from, Durametallic and Five Star were the ANSI market seals and the Pac-Seal are for the OEM market.

In the past, external clean, cool fluid was used to lubricate seal faces or dual seals operating on clean barrier fluid. Now, the solution  is to use Diamond Coated Silicon Carbide Faced Seal (UNCD) and let the process fluid itself lubricate the seal even with challenging applications.

Flowserve Mechanical Seal Piping Plan Flip Book – reference book that provides a concise summary of the most essential piping plans used successfully in today’s process plants. Each plan shows all the standard and optional auxiliary components referenced in API Standard 682

See improved performance of replacing John Crane Type 21 ™ with a Pac-Seal 21 utilizing a crimped-head rotary unit removing metal contact from the seal ring and preventing foreign material from collecting under the bellows.

Standard cartridge mechanical seals provide exceptional reliability and standardization in a wide variety of industrial applications and service conditions. ISC2 seals are designed to fit hundreds of pump and rotating equipment models from global manufacturers.

Application Guide: mechanical seals in product pipeline pumps, covering the transmission of crude oil and refined products such as fuel oils, gasolines, crude oils, and natural gas liquids (NGL), propane and ethane.

Increasingly restrictive regulations on leakage and safety have resulted in an increase in the number of multiple seal arrangements. All wet multiple seals use an external fluid in addition to the process fluid that is to be sealed. The terms ‘buffer fluid’ and ‘barrier fluid’ are used to describe these fluids. As defined in API 682, a buffer fluid is used in unpressurized dual seals. A barrier fluid is used in pressurized dual seals to isolate the pump process liquid from the environment. Gases may be used as buffer or barrier fluids depending on the design of the mechanical seals. The following information focuses on liquid buffer or barrier fluids.

Several critical properties should be considered when selecting a buffer or barrier fluid. An ideal buffer/barrier fluid would have the following properties:

A good buffer or barrier fluid should not present any potential danger whether equipment is running or stationary. Safety should be a top priority when selecting a fluid. It should not be a listed VOC (Volatile Organic Compound) or VHAP (Volatile Hazardous Air Pollutants).  It should not be flammable in the considered application.

A process temperature at or above the boiling point of the buffer/barrier fluid would cause the formation of vapor on and around the sealing faces on the atmospheric side. It would not only promote shortened seal life or catastrophic failure, but formed vapor could be a fire risk. The buffer fluid frequently operates near atmospheric pressure and can potentially reach the same temperature as the pump it serves. Therefore the atmospheric boiling point must be considered and should be at least 50°F (28°C) above the process temperature.

Viscosity is one of the most important properties of a good buffer or barrier fluid and is representative of lubricity. The fluid should be viscous enough to separate surfaces and prevent wear without restricting seal movement or heat transfer. High viscosity can also cause carbon blistering. In general, current guidelines for buffer/barrier fluid viscosity are to use lower viscosities than in the past. The following guidelines are helpful:

The buffer or barrier fluid should be a good heat transfer fluid. The physical properties of a fluid that reflect this ability are thermal conductivity and specific heat. The higher the process temperature, the higher these values should be. Water has very good heat transfer capability. The specific gravity should be at least at 0.7 at operating temperature. A higher specific gravity decreases the required flow rate and allows better heat removal.

The buffer or barrier fluid must be compatible not only with the metallurgy, elastomers and other materials of the sealing system but also with the process fluid.

Lubricants are generally non-corrosive to hardware and faces so attention is focused on the elastomeric parts of the seal that are more susceptible to chemical reaction.  In particular, the compatibility of synthetic rubber with an oil is dependent on the value of the aniline point of the oil. A low aniline point causes swelling and softening of the elastomer which may result in extrusion. On the other hand, if the aniline point of the oil is too high, the elastomer may shrink and harden.

The fluid should also be highly compatible with the process fluid being sealed. This compatibility is desired whether a buffer or barrier fluid is being considered. Situations that tend to cause any reaction are to be avoided.  The formation of gases, particles, high viscosity liquids or vapors as a consequence would disturb the fluid flow, plate the seal faces or cause wear and leakage.  Each fluid must be individually considered based on its chemical compatibility with the process stream.

Some buffer/barrier fluids are relatively clear in color. Sometimes the supplier or end user adds a dye to make the fluid easier to see in reservoir sight glasses. The dye may change the properties or compatibility of the buffer/barrier fluid.

Conventional lubricating oils contain various additives according to the intended use of the oil. For example, additives may be used to suppress H2S, resist corrosion, prevent foaming, reduce wear, etc.  Some of these additives are intended to deposit, or “plate out”, on the surfaces being lubricated.  In the case of mechanical seals, such deposits increase seal leakage and are not desirable.  In particular, oils labeled as “turbine oils”, “gear oils” and “EP” (extreme pressure) creates problems for mechanical seal faces and are not recommended.

In Plan 53A pressurized systems, the barrier fluid is pressurized using an inert gas, typically nitrogen, in direct contact with the barrier fluid.  In this case, problems can occur when the gas is absorbed into the barrier fluid. As pressure is relieved or temperature rises, gas may be released from the fluid. This release of gas can cause the pumping to become vapor locked or cause foaming, resulting in loss of lubrication, heat transfer, and circulation.

With stable buffer/barrier fluids, maintenance intervals can be increased.  Requirements for fluid change intervals can vary significantly and are beyond the scope of this document; however, monthly monitoring for changes in pH, color, viscosity, consistency and presence of solids is suggested.

Fluids exposed to oxygen must resist oxidation at operating and static conditions. The oxidation of the fluid causes the formation of acids and carbonized by-products. This results in carbon deposit on the faces (coking), viscosity change, and loss of sealing and heat transfer properties. The oxidation resistance of a fluid is indicated by its total acid number. Synthetic oils are more susceptible to acid formation than hydrocarbons.

Unpressurized buffer fluids may lose volatile materials, causing an adverse effect on their original performance characteristics. Highly volatile fluids should not be used. Fluids with low vapor pressure are essential to keep the volume of the lubricant constant.

Intuitively, buffer/barrier fluids operated at high temperatures should be changed more regularly than those operated at lower temperatures. API 682 guidelines for allowable temperature rise in buffer/barrier fluid systems are 15°F (8.3°C) for water based solutions and diesel/kerosene but 30°F (16.6°C) for mineral or synthetic oils. As an example, a system using oil might have the reservoir at an average temperature of 130°F (54.4°C) with an outlet temperature of 115°F (46°C) and inlet of 145°F (62.8°C). API 682 does not provide guidelines for the average temperature. A simple rule of thumb for chemical reactions is that the rate of reaction doubles for every 18°F (10°C) rise in temperature. This rule of thumb can be applied to the decomposition of buffer/barrier fluids. As an example, suppose that a certain barrier fluid performs well for six months at an average temperature of 130°F (54°C). If the reservoir temperature were 148°F (64°C) then the fluid change interval would probably become three months. This guideline can be useful for evaluating heat transfer options during system design.

Water can be a good barrier/buffer fluid. Viscosity is generally around 1 cSt (31 SUS) at modest temperatures; however, the viscosity of water is low at 212°F (100°C), which is also the atmospheric boiling point. Also, in many climates, water may freeze at ambient conditions.  Traditional automotive anti-freeze has not been recommended because of the corrosion inhibitors in it; however, this may be changing as discussed below.

The silicate inhibited coolant and also HOAT are somewhat problematic because of leaving film on the sealing faces. The film is believed to form as the coolant boiled/evaporated between the faces due to upset condition in the cooling system and in turn leaving residue (silicates) behind which eventually led to uneven gaps on the faces and then failure of the seal.  The tendency to leave deposits gets worse as the concentration of glycol in water becomes more than about 60%

The OAT coolant is not as problematic and deposits little or no film on the face. Since 1996, this OAT antifreeze has been used in GM cars and is marketed as “Havoline DEX-COOL”.   Although OAT coolants are not widely used in mechanical seal systems these coolants appear to be good candidates for replacing traditional inhibited ethylene glycol coolants.

High levels of dissolved chlorides, sulfates, magnesium, and calcium in tap water also cause scale / sludge deposits and corrosion therefore distilled or de-ionized water is preferred for mixing with the glycol.

Commercial inhibited glycol coolants use the older silicate inhibitor technology; this is why uninhibited glycol solutions were recommended for buffer/barrier fluids with mechanical seals.

Many distributors mix and private label their own coolants.  There are also companies selling inhibitor packages for either making your own inhibited coolant or for replenishing used coolant.  There are various references and articles about color codes for glycols and antifreeze but none of these are true standards and there are many variations.

Alcohols can have a high rate of evaporation and frequent refills may be required on a Plan 52 (unpressurized buffer fluid). Check the properties, especially vapor pressure, of the alcohol type that is being considered.

Methanol. Although methanol has been used in the past as a buffer fluid for tandem seals in low temperature services, it is a VHAP and is not recommended. In addition to being toxic, methanol has a low boiling point and low viscosity. It is not a good seal face lubricant.

Propanol. 1-Propanol, or n-propyl alcohol, has replaced methanol as a buffer fluid for low temperature services. However, propanol has an exposure limit of 200 ppm (50 mg/m3) OSHA TWA (Total Weight Average).

The viscosity of diesel fuels and deodorized kerosenes can provide adequate seal face lubrication through a wide temperature range.  However, low sulfur diesel fuel does not appear to be a good seal face lubricant and is not recommended as a buffer/barrier fluid. Although not a flashing hydrocarbon according to API 682, diesel fuels and kerosenes may be classified as volatile organic compounds (VOC), especially at higher temperatures.

Lube oils. Although turbine oils have been used extensively in the past, experience is that the anti-wear/oxidation resistant additives plate out on the seal faces. The lower viscosity grade (less than ISO Grade 32) provide better performance. Paraffinic based oils seem to be better than naphthenic oils. Blistering of carbon seal faces is common when lube oils are used as buffer/barrier fluids, especially ISO grades 32 and higher. Experience has shown that synthetic oils perform better than conventional turbine oils; this may be partially due to the (generally) lower viscosity of the synthetics. Automatic transmission fluid. Automatic transmission fluid has the proper range of viscosities but is not recommended. Actual experience has generally been that automatic transmission fluid is a poor barrier fluid; the assumption is that the various additives are the problem.

Specific purpose buffer/barrier fluids, usually polyalphaolefin (PAO) based synthetic oils, have been increasingly used in the past decade and becoming more and more popular. These synthetics are approximately ISO Grade 5 to 20. The most popular is the lowest viscosity. The higher viscosity oils are used for higher temperatures and/or lower shaft speeds. Unfortunately, synthetics are the most expensive buffer/barrier fluids.

Heat transfer fluids that have the ability to provide adequate lubrication throughout a wide range of temperatures and pressures can be used as buffer or barrier fluids. Heat transfer fluids encompass a broad spectrum of chemical families (water, steam, inorganic salts, certain liquefied metals, organic class fluids …).  This guide addresses the use of organic class heat transfer fluids. They fall into two categories:

Synthetic aromatic fluids, such as the various Dowtherm fluids. These offer higher thermal stability, broader working temperatures range and are more effective than petroleum ‘hot oils’.

Dowtherm.  Dowtherm is a family of synthetic heat transfer fluids manufactured by Dow Chemical Company.  Currently, Dowtherm types are A, G, J, MX, Q, T, and RP.  Dowtherm RP has been used extensively in high temperature tests with good results.

A number of other heat transfer fluids such as Therminol, Multitherm, Paratherm, etc., are commonly used as buffer/barrier fluids. Selection should be based on temperature limits for the selected Plan 52, 53, or 54 system based upon experience with the heat transfer fluid.

The table below shows general temperature guidelines for Buffer/Barrier Fluid Classes.  Use of a fluid from these  families does not necessarily ensure successful operation of a sealing system.

Although it is generally accepted that buffer/barrier fluid systems for mechanical seals should be drained and the fluid completely replaced at certain intervals, there have been no definitive guidelines established for recommending that interval.  The following recommendations are starting points and are not absolute or all-inclusive. Monitoring the fluid for degradation and contamination is strongly recommended and appropriate adjustments should be made to the interval between fluid changes.

The advantage of using this method as an initial estimate of service life is that it provides a means for optimizing operating costs based on buffer/barrier fluid type, pump and system temperatures, seal arrangement and sealing system. For example, system temperature is determined by the size and design of heat transfer equipment such as heat exchangers and reservoirs.

All buffer/barrier fluid systems can be considered to have the bulk of the fluid at some average operating temperature.   Typically, this bulk fluid temperature is less than 150 F but considerably higher average temperatures are sometimes permitted or even used as a design point.  One advantage of high bulk fluid temperature is that heat soak from the pump is reduced.  Another advantage is that the efficiency of heat transfer to cooling water is increased.  As noted previously, a disadvantage is that the buffer/barrier fluid is expected to degrade more rapidly at high temperatures. Another disadvantage is that many end users and local regulations require personnel protection near high temperature reservoirs and piping.

API 682 4th edition does not limit the bulk fluid operating temperature for buffer or barrier systems.  Therefore the maximum allowable bulk fluid temperature remains an operating or design detail that might vary significantly.  However, in absence of other information or requirements, a good guideline for the maximum bulk fluid temperature is 150 F.

API 682 guidelines for allowable temperature rise in buffer/barrier fluid systems are:  15 F for water based solutions; 15 F for diesel/kerosene; 30 F for mineral or synthetic oils.

Buffer/barrier fluids should be drained, the system flushed and refilled with clean fluid at intervals not to exceed six calendar months of continuous or standby operation regardless of seal design, operating conditions or details of the piping plan.  The recommended interval may be less than six calendar months based on the bulk fluid temperature, see below.

The recommended time between fluid changes should be based on the average operating temperature of the system as compared to the base case temperature.

A simple rule of thumb for chemical reactions is that the rate of reaction doubles for every 10 C (18 F) rise in temperature.  This rule of thumb is often applied to lubrication systems and, in the absence of more specific data, will be applied to buffer/barrier fluid systems. For lack of data, the base case temperature for all fluids is assumed to be 150 F and the base case change interval is assumed to be six months.

As an example, suppose that mineral oil is used as a barrier fluid. The base case temperature is 150 F and the base interval is six months.  Based on the rate of reaction doubling for every 10 C (18 F) rise in temperature, if the reservoir temperature is 168 F then the recommended fluid change interval is reduced to three months.

Protect the integrity, efficiency, and flow of your site operations with help from AFT. No matter the size or complexity or your system, AFT and our partner AESSEAL offer the highest quality seals and support systems for your industry.

In many cases, Cartridge Seals may contain the exact same major items that are sold separately as Component Seals. These pieces include the Rotary Seal and Stationary Face as well as other minor parts like O-rings or Gaskets all required at assembly. The advantage of using a Cartridge Seal is that the time required for installation, and even more importantly, the possibility of error during installation is dramatically reduced. When installing a Cartridge Seal, the necessity of having to measure internal components positioning on the shaft to achieve proper face loading is eliminated. Cartridge Seals come pre-assembled from the factory with all internal components assembled with proper face loading and all pieces in place, exactly where they should be. Cartridge Seals eliminate the need to handle delicate, polished parts such as Seal Faces that can be compromised by the presence of dirt, smudges and oils that can result from handling during assembly. So, for the easiest and most reliable Seal installation, Cartridge Seals go a long way towards helping you achieve trouble free startup and extended service life from your equipment.