API PLAN 23
Recirculation from a circulation device in the seal chamber through a cooler and back into the seal chamber.
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- Product in seal chamber is isolated from pumping area using a close clearance throat bushing.
- Increases product temperature margin in the seal chamber thus avoiding vaporization.
- Seal runs at a lower stabilized temperature of the media.
- Removes only the generated seal face heat and the heat soak from the pump area, thus the cooler is smaller and more effective as compared to an equivalent Plan 21.
- Uses a pumping ring for circulation in running condition.
- In idle condition, thermosiphon effect ensures circulation.
- A distributed flush is not recommended for this plan.
- For media with high viscosities and higher freezing points, steam must be used in the cooling lines instead of water.
- A high-point vent valve to be provided to vent the system before start-up.
- A close clearance throat bushing must always be in place to reduce the heat soak from the pump.
- Avoid sharp bends and 90° elbows in piping. Piping should be smooth and continuously rising.
- Cooler to be installed approx. 500 mm (20”) above pump centerline.
- Good quality cooling water is recommended to avoid deterioration of cooler efficiency.
- Flush outlet from seal chamber should be in the top half of the seal gland plate or the seal chamber.
- Hot hydrocarbons.
- Hot water services above 80 °C (176 °F).
- Boiler feed water.
- Applications where increasing seal chamber pressure to improve vapor pressure margin is not possible.
