Flowserve Seal Support Reservoir Manual de usuario descargar pdf (Pagina 5)

Buffer/Barrier Fluid Selection

The following should be considered when selecting a barrier/buffer uid:

• Compatibility of the uid with the process pumpage being sealed so as not to

react with or to form gels or sludge when the uids are intermixed.

• Compatibility of the uid with the metallurgy, elastomers and other

materials of the seal/ush system construction.

For an API Plan 53A/ANSI Plan 7353A pressurized barrier uid system where

the method of pressurization is a gas blanket, special attention must be given to

the application conditions and barrier uid selection. Gas solubility in the barrier

uid increases with the rising temperature and pressure. As pressure is relieved

or temperatures cool, the gas is released from the solution and may result in

foaming and loss of circulation of the barrier uid. This problem is normally seen

where higher viscosity barrier uids, such as lube oils, are used at pressures

above 150 psig (10.3 bar). Synthetic barrier uids offer greater compatibility and

wider operating ranges where traditional uids have problems.

The viscosity of the barrier/buffer uid should be checked over the entire

operating temperature range with special attention being given to start-up

conditions. The viscosity should be less than 500 cst at the minimum

operating temperature.

1. For services above 50°F (10°C), hydrocarbon barrier/buffer uids having a

viscosity below 100 cst at 100°F (37.8°C) and between 1 and 10 cst at

212°F have demonstrated proper operating climate.

2. For services below 50°F (10°C), hydrocarbon barrier/buffer uids having a

viscosity between 5 and 40 cst at 100°F (37.8°C) and between 1 and 10 cst

have demonstrated proper operating characteristics.

3. For aqueous streams, mixtures of water and ethylene glycol or propylene

glycol are usually adequate. Commercially available automotive antifreeze

should never be used. The additives in antifreeze tend to plate out (leave a

residue) on seal parts and cause failure as a result of gel formation.

Note: Ethylene glycol may be considered a hazardous material and/or

hazardous waste when used as a barrier uid.

4. The uid should not freeze at the minimum site ambient temperature.

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Flowserve Seal Support Reservoir Manual de usuario Pagina 5