In this post, learn why heat exchangers should be installed vertically with API Plan 21 and 23.
There are two API Seal Environmental Control Plans used to keep seals cool and clean in high temperature water applications:
- API Plan 21 (Cooled Discharge Recirculation) provides cooling to the seal with high flush flow rate capabilities by recirculating pump discharge fluid through a flow control orifice and heat exchanger before it enters the seal chamber.
- API Plan 23 (Cooled Seal Recirculation) cools the seal chamber fluid by using a pumping device(pumping ring) to circulate the seal chamber fluid through a heat exchanger and back to the seal chamber.
Effectiveness of both these seal environmental control plans depends largely on the functionality and effectiveness of the heat exchanger to cool the fluid so that the seal faces will have cooler fluid for lubrication.
Heat Exchanger Positioning
The effective functioning of a heat exchanger in a flush system depends on its sizing and positioning. Customers often ask: “Should I install the heat exchanger in horizontal or vertical position?”
As shown in Figure 2, the heat exchanger can be installed in either position, but there are distinct advantages to a vertical installation.
Vertical or Horizontal Installation:
A heat exchanger can be installed in a horizontal position and can provide cooling capabilities when it is mounted horizontally, however it is much more advantageous to mount this heat exchanger vertically as shown in the Figure 1 above. In a vertical position, the cooling coil tubing winds gradually downward and upward for optimum fluid drainage and gas/air venting.
In a horizontal position, it is much more difficult to totally drain both the sealing and cooling fluids. The sealing fluid becomes trapped within the lower turns of the cooling coil, and the shell side cooling water becomes trapped below the lowest drainage point. The heat exchanger would need to be removed and positioned vertically to achieve total drainage. It is also much more difficult to vent air/gas from a horizontal installation because gas/air can become trapped within the upper turns of the cooling coil. A flush might be necessary to remove these trapped gases.
The presence of trapped gas/air is more critical when using a Plan 23. Trapped gases that become entrained in the sealing fluid can reduce the efficiency of a heat exchanger and flow in the seal flush circuit. This can ultimately cause the seal to overheat and fail due to lack of seal face lubrication. A vertically mounted heat exchanger provides the advantage of a thermosyphon effect to help alleviate these detrimental conditions.
For applications that must conform to API standard 682 requirements, the API standard 682 specifies that the heat exchanger must be mounted to allow complete draining and venting of both the cooling water and the process fluid. This capability can be easily achieved with vertical installation.
If you have any questions about either plan or heat exchanger installation, contact your local Chesterton office or our “Ask the Expert” service.
