Selection of sealing flushing plans plan21 and plan23
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Regarding the choice between sealing flushing solutions 21 and 23 per API682, let me first share my understanding. 21: The flushing medium is drawn from the pump outlet, passes through an orifice plate and a heat exchanger, and then reaches the sealing area. 23: The flushing medium is drawn from the sealing chamber, passes through a heat exchanger, and reaches the sealing area; internal pump impellers are required for circulation. Since the medium is drawn from the outlet in route 21, the pressure is high, so an orifice plate is needed to regulate both pressure and flow rate ； 23 The medium is drawn from the sealed chamber; the circulation pressure difference (power) is provided by the impeller, and the circulation volume also depends on the impeller. Question: Based solely on these superficial explanations, when the medium temperature is above 80 degrees Celsius and under clean conditions, both approaches can be used. So what exactly should be chosen? On the surface, 21 increases the circulation volume, but the flushing fluid is involved more fully in the internal flow; with back blades on the impeller, a large circulation can even be formed ； As for 23, it seems that the circulation takes place only within a small area inside the sealed chamber; it gives the impression of a \"dead\" circulation. Moreover, with an additional internal pump wheel, is the cost of sealing for 23 relatively higher compared to 21? Please share your opinions; the key question is how to choose between the two? This article is from: Pump and Valve Technology Forum – http://www.pumpvip.com/ For the full article, please visit: http://www.pumpvip.com/viewthread.php?tid=51412&extra=
23 By utilizing the pump-efficiency thread circulation, the temperature here is already a bit lower than that inside the pump chamber, which thus facilitates cooling further.
A temperature of over 80 degrees is sufficient with Plan 11. Personally, I think the 80-degree threshold is too conservative; for water, a temperature of over 90 degrees is more appropriate. Generally, pump manufacturers use setting 21, as it yields an excellent heat exchange effect, while setting 23 is rarely used
Personal opinion: Plan21 is suitable for use when the medium is clean, and operational issues arise at moderate temperatures, between 110° and 250°. If the pressure difference between the inlet and outlet exceeds 10 bar, a flow-limiting orifice plate should be used. Plan23 is used in media at temperatures above 250°; it relies on circulation through the pump ring to cool only the sealing chamber, and there is a vent hole on top of the seal oil tank. It uses the same high-temperature auxiliary sealing system as any other.
Our plant’s hydrogen production facility is equipped with a boiler forced circulation pump that follows the 23 design scheme; the cooling auxiliary system appears to be quite complex, with numerous maintenance points. There are quite a few problems with the seals; they need to be replaced every two months on average. This is mainly due to the fact that the sealing gaskets cannot withstand high temperatures. Incidentally, the operating temperature for this pump is 230 degrees, with a pressure of 2.5 megapascals.
Compared to the 21 scheme, the 23 scheme mainly differs in terms of thermal load. The latter has a heavier cooler load, higher heat exchange efficiency, but is more prone to tube blockage
Generally, use 23 for temperatures above 180, and 21 for those below 180, but 23 is used for all hot water
Plan21 introduces the medium through the outlet; compared to Plan23, it has higher flow rates and pressures. When the medium is water, it can easily vaporize upon reaching the sealed surface, thereby damaging the seal. 23: Small-scale self-circulating cooling; the cooling effect of high-temperature water for flushing is more reliable than that of 21.
In this case, you need to contact the manufacturer; there is definitely a problem with the sealing material used. The washer must be heat-resistant. If it is fluororubber, perfluororubber may be required. The prices differ greatly.