api plan 52 mechanical seal made in china

Depressurised buffer fluid circulation in outboard seal of a dual seal configuration through a seal support system. Circulation is maintained by using pumping ring in running condition and by thermosyphon effect in stand still condition.

1. Keep the sealant vessel vent continuously open, which is necessary to maintain buffer fluid pressure close to atmospheric pressure and vent the vapors to flare.

6 US GAL API682 Plan52 Plan53A Mechanical Seal Support System performs all basic function of a buffer/barrier system for the operation of double seals:

In the past there was only one Plan 53, but with the 2nd Edition of API 682 and the 1st Edition of ISO 21049 other variations of Plan 53"s were created.

Plan 53A is the former Plan 53. Plan 53B is what had been in the past denoted as Plan 53 Modified; this is especially popular in European and other countries in the Middle East. Plan 53C is a variation of this that has also been used in the past and is now formally recognized.

The major difference in the plans is that Plan 53A uses an external reservoir, while Plans 53B and 53C run within a closed loop system with a make-up system piped to it for replenishment of the barrier fluid.

In dual pressurized sealing arrangements the inner process seal can have its own flush plan; in such applications the complete flush plan system designation should include both plans. For example, Plan 11/53A means that the inner seal has its own flush plan, Plan 11. The API/ISO default is for no separate flush plan when using any of the Plan 53"s, but this can vary with the application conditions.

With the older traditional back-to-back seal arrangement the inboard seal usually does not require a separate flush. In applications such a hydrofluoric acid, where it is both extremely hazardous and corrosive, a Plan 32 can be used in conjunction with a Plan 53. The dual pressurized face-to-back seal arrangement eliminates some of the potential problems associated with the back-to-back design. This face-to-back seal arrangement sometimes incorporates a reverse pressure capability that is not a default with the back-to-back design.

Also, face-to-back arrangements do not have a dead zone underneath the inboard seal that can become clogged by dirty process fluid and lead to seal hang-up. However, the face-to-back arrangement is not a cure-all. With the product on the seal O.D. and with it being used on API pumps that still incorporate throat bushings, it is advantageous to provide a flush for the inboard seal on a number of applications.

Abrasives can accumulate in the more closed API type seal chambers compared to the newer generation chemical duty pumps with large cylindrical bore or tapered bore chambers. The use of a Plan 11 or similar bypass type flush for the inner seal has advantages. It can help keep the seal chamber clean. It also has an improved overall heat transfer setup versus just using a Plan 53 system alone.

In comparison to a Plan 54, Plans 53A/B/C are usually less complex and less expensive. With Plans 53A/B/C, both the inner and the outer seals are lubricated by the barrier fluid, which can be selected for optimum seal performance. Plans 53A/B/C are usually selected for dirty, abrasive, or polymerizing process services which might be difficult to seal directly with single seals or with dual unpressurized seals using a Plan 52. There will always be some leakage of the barrier fluid into the process with any pressurized system.

With some of the Plan 53 systems the volume of barrier fluid is limited, especially compared to a Plan 54 system. Venting of the seal chamber is essential for all Plan 53"s where vapor locking can if vapor bubbles collect near the pumping ring or in the piping.

Plan 53A uses an external reservoir to provide barrier fluid for a pressurized dual seal arrangement. Reservoir pressure is produced by a gas, usually nitrogen, at a pressure greater than the maximum process pressure being sealed. The gas pressure is regulated by a system that is outside the schematic of the piping plan. Circulation of the barrier fluid is maintained by an internal pumping ring.

Like Plan 52 reservoirs, cooling is accomplished internal coil of tubing to remove the heat. Also like Plan 52 reservoirs, the volume of barrier liquid can vary from two gallons to 5+ gallons, where API and ISO standards specify 3-gal and 5-gal, depending upon the shaft diameter.

For non-API specifications, smaller reservoirs - typically 2-gal - are often used, especially at ambient pumping temperatures. Pressure alarms, pressure gages and level switches are typically standard equipment and are required by API 682/ISO 21049.

The usual guideline for Plan 53 barrier pressures is that they be a minimum of 20-psi to 50-psi above the maximum process pressure seen by the seal. Barrier pressure is normally supplied by a plant wide distribution system. Nitrogen bottles should not be used as they require a lot of attention and maintenance.

API 682/ISO 21049 recommends that the system be limited to 150-psig due to gas entrainment into the barrier fluid. Field experience has shown that with the proper barrier fluid, Plan 53A systems can be used up to 300-psig if the temperature is controlled to less than 250-deg F. A variation to this would be to use an accumulator to eliminate gas entrainment.

Disadvantages (vs. other Plan 53 systems)The barrier fluid in Plan 53A is subject to gas entrainment due to direct exposure to the pressurizing gas. Different barrier fluids have varying levels of gas entrainment.

Installation should be limited to a single seal installation even on between bearing pumps. Therefore for a large number of installations, Plan 53A can be more expensive than Plan 53B or 53C.

nlike a Plan 53A that incorporates a pressurized reservoir within the circulation loop, Plan 53B incorporates a bladder type accumulator along with the piping and an air or water cooled heat exchanger to provide for barrier fluid capacity.

Some installations use finned tubing as the heat exchanger, but these should be used with caution as the heat removal depends upon a positive air flow across the tubing to be effective. Gas entrainment is not a problem with this plan since it incorporates bladder accumulator to maintain the barrier pressure within the closed loop circuit.

The accumulator should be pre-pressurized to between 80 percent and 90 percent of the barrier pressure. This creates a problem in that it limits the volume of fluid within the Plan 53B circuit. The majority of the accumulator volume is gas. The basic setup is comprised of two parts; the closed loop circulating system made up of the piping and heat exchanger and the make up system.

Flow in the circulating system is usually induced by an internal pumping device. The make up system can be configured a number of ways based upon the customer"s preference, ranging from a simple hand pump to an elaborate pumping system feeding multiple pumps/seals.

Like Plan 53A, the flow rate of the Plan 53B circuit is controlled by the pumping ring design, peripheral speed, barrier fluid viscosity, and resistance of the piping circuit; the piping circuit of 53B includes a heat exchanger. The sizing of the heat exchanger depends upon the heat load of the system. The heat exchanger should be designed to contribute minimum resistance.

API 682, 3rd edition does not provide guidelines for sizing the accumulator of Plan 53B, but the total fluid volume of the system should be about the same as the volume of a 53A system.

Disadvantages (vs. other Plan 53 systems)The volume of fluid within the closed loop circuit is very limited, as little as one-half gallon in some instances.

With the limited fluid volume the barrier fluid gets thermally cycled on a much more frequent basis than a Plan 53A, so the service life of the fluid is reduced.

The finite volume of the accumulator requires a designed pressure operating range between refills (in excess of that required for a Plan 53A) and this must be built into the pressure rating of the seals.

The separate heat exchanger introduces additional flow resistance to the piping system and will have a lower flow rate than an otherwise identical Plan 53A.

Plan 53C is a variation of Plan 53B that uses a piston accumulator to track the pressure of the seal chamber. In Plan 53C, the piston accumulator has a reference line from the seal chamber to the bottom of the accumulator. There are differences in diameter of the internal piston so that a higher pressure is generated on the top half, which in turn is piped to the circuit loop into and out of the seal chamber.

Similar to Plan 53B, there is no gas pressurizing the barrier fluid so there is no chance of gas entrainment. Also, like Plan 53B flow is generated by a pumping ring through a heat exchanger. The heat exchanger can be water cooled, air cooled or can be finned tubing if the heat load is small enough. This system should be used with caution, as the reference line to the accumulator is subject to the process fluid. The process fluid may be corrosive, abrasive, or a slurry that could potentially clog the pressure reference line threatening the tracking ability of the system.

The advantages and disadvantages are the same as the Plan 53B system. Additionally, the disadvantage of this system is that pressure spikes or pressure drops in the process pressure will vary the pressure on the outer seal that may create a temporary leakage condition. Also, tracking pressures can always be subject to delays that can cause a temporary loss of positive pressure differential across the inboard seal.

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These reservoir-based seal support systems are designed for both API Plan 52 and 53A applications to support unpressurized and pressurized dual seals. Circulation of buffer/barrier fluid is normally achieved with a pumping ring (or optional circulating pump), and a range of heat exchangers can be packaged with the system — selection dependent on available plant utilities.

Plan 52 uses an external reservoir to provide buffer fluid for the outer seal of an unpressurized dual seal arrangement.  During normal operation, circulation between reservoir outer seal is maintained by an internal pumping ring.  The reservoir is usually continuously vented to a vapor recovery system and is maintained at a pressure less than the pressure in the seal chamber.   The process, or inner seal, of the dual unpressurized arrangement usually has its own piping plan.  For example, the piping plans for a dual unpressurized seal arrangement might be written as Plan 11/52.

Reservoirs are usually made of pipe and piping components with an internal cooling coil. Unlike the heat exchangers used in Plan 23systems, cooling water flows through the coil; the buffer fluid flows over the exterior of the coil.  It is important to realize that Plan 52 systems incorporate a vented reservoir.

Plan 52 systems are usually not controlled directly.  The circulation rate depends on the performance of the pumping ring within the particular closed loop system.  The pumping ring, reservoir and piping are selected to produce the desired operating conditions.  Heat soak as well as heat generation must be considered in determining the desired circulation rate.

In the event that the process, or inner, seal fails, there will be a pressure and/or level increase in the reservoir, which produces an alarm. When this occurs, the reservoir is blocked in by closing the valve near the top of the reservoir. As the process seal continues to leak, pressure and fluid level in the reservoir increases further.  The reservoir can potentially reach the same pressure as the process seal chamber.   For all practical purposes, the outer seal takes over the full sealing duty.  For these reasons, the recommended operating procedure is to begin planning an orderly shutdown and repair as soon as possible after failure of the process seal.

Plan 52 is used for both non-volatile and volatile process services. Although the leakage rate across the main, or process, seal is about the same as for a single seal, the leakage is directed into the reservoir of the dual unpressurized seal.  In non-volatile services, the leakage from the process seal increases the liquid level in the reservoir.  Depending upon the process fluid the reservoir may require periodic cleaning.  In volatile services the leakage from the process seal vaporizes and is separated from the buffer fluid inside the reservoir.  If the reservoir is connected to a vapor recovery system, the actual emission rate can be very low.

Specialized in supplying seal support system according to API Plan 52 or 53 pressured system. Designed by mainly including buffer fluid reservoir, mechanical seal, monitoring part, control part, pipes, hand refill pump, heat exchanger to control mechanical seal`s temperature, improve its lubrication condition and control its working pressure in order to prevent from pollution and provide alarm when seal leakage happens. Build an ideal working environment for mechanical seal, improve reliability and safety of mechanical seal and prolong its life time. Cyclone separator is used to clean aqueous liquids containing dirt and solids. And transfer cleaned liquids to the seal area or other needed areas.