![\"Chemical](\"https:\/\/www.longgangpump.com\/wp-content\/uploads\/2026\/09\/How-to-Select-a-CO2-Booster-Pump-for-CCUS-Projects-Structure-Seals-and-Materials_inline_2-1.jpeg\")
<\/p>\nBoiler feed pump mechanical seals need a cooling plan that keeps water liquid at the seal faces throughout the operating cycle. Plan 21 cools a flush taken from the pump’s high-pressure side. Plan 23 recirculates liquid within the seal chamber through a cooler. Plan 23 often reduces the cooling load in clean hot-water service, but its circulation and venting requirements must be met. Water temperature alone cannot settle the choice.<\/p>\n
Longgang Pump supplies API 610 11th-edition centrifugal pumps for chemical plants and refinery utilities, including multistage boiler feed water pumps. When installing new or replacing seals, start by determining the condition of the seal room and the site cooling facilities and what they can do.<\/p>\n
<\/p>\n
The boiler feed pump can deliver the required flow at the designated head, but the mechanical seal may still operate in an unacceptable environment. The vapor pressure of hot water is higher and its viscosity lower than that of cooler water. If the water should locally flash, the seal faces will no longer be coated by a film of liquid, which lubricates them. A suitable cooling circuit must be established to form and maintain this liquid film; the plan number alone does not provide any information on the seal temperature.<\/p>\n
The important pressure for an assessment is the chamber pressure. Discharge pressure on a multistage pump is not necessarily the relevant pressure. The engineer needs to know the chamber pressure and temperature over the operating range, and the water chemistry, solids content, etc. as well as the expected transients. These conditions define the vapor margin and will establish whether or not a proposed flush circuit is adequate.<\/p>\n
The pressure difference is used to send process water through a flow-control orifice and cooler into the seal chamber. For the LDD BB4 high-pressure segmented multistage pump<\/b><\/u><\/strong><\/a>\u00a0proposed circuit the available pressure between flush takeoff and chamber needs to be checked. The cooler for the incoming hot water is running continuously and thus both the flush rate as well as the degree of temperature reduction are important for the size of the cooler.<\/p>\n One installation maleic anhydride plant Xinyang Technology uses an LDD 145-65\u00d710 BB4 for boiler feed pump P-51837A. The normal water temperature for this installation is stated to be 105\u00b0C. The rated flow for this pump is 138.2 m\u00b3\/h and 648 m head. The pump operates with Plan 21. This is a specific operating example and not a temperature limit for the plan.<\/p>\n Plan 23 uses seal chamber liquid, cools it and returns it to the seal chamber. A pumping ring on the seal is used to circulate the liquid. The effective throat bushing prevents too much exchange with the hotter pump casing water. It does not make a completely isolated pressure vessel out of the seal chamber.<\/p>\n The cooling can then be aimed at the heat that is generated by the seal itself and the heat that enters the seal area from the surrounding parts of the pump. Importantly, the cooling stream is not running against a fresh stream of hot process liquid as it would be under Plan 21. However, the load on the cooler must still be calculated for the particular seal, the chamber and the associated piping.<\/p>\n For Huizhou Yuxin\u2019s maleic anhydride project, the selected boiler feed pumps P-1844A\/B are LDD 340-155X8 BB4 pumps running with Plan 23. Normal water temperature is 152\u00b0C, normal flow 282m\u00b3\/h, rated flow 326m\u00b3\/h and head 1,200m. As mentioned previously, the above installed condition is for selection of the Plan 23, which is not the operating range for Plan 23.<\/p>\n Another Plan 23 installation, Puyang Shengyuan’s deaerated-water feed pumps P-922A\/B, used an LDD 250-120X5+1D BB4 at a normal temperature of 104\u00b0C, rated flow of 250 m\u00b3\/h and 610 m head. Its temperature was close to the 105\u00b0C Plan 21 example. The different selections show why a fixed water-temperature threshold is insufficient. The chamber design, cooling duty and purchaser requirements still need evaluation.<\/p>\n Utility data required for a water-cooled seal cooler should detail the hottest water supply condition, plus the available flow and pressure, any return restrictions and water quality. Coolers sized for best case conditions in winter may have very little margin for summer operation. Fouling is also a major heat transfer reducer. Arrangements should allow for easy isolation plus be readily inspected and cleaned.<\/p>\n Plan 23: It is wise to pay special attention to this during the piping design. The pumping ring has a limited ability to overcome resistance. Thus, short piping runs, suitable pipe diameters and few restrictions in the piping will be necessary. In addition, high-point vents must be designed in such a way that air and vapor can leave the chamber, the piping and the cooler before start-up. An oversized cooler with poorly routed piping runs can still not provide any useful circulation.<\/p>\n A procedure must be established to setup a filled and vented seal system and to connect up cooling prior to start-up. In many cases a pumping ring is used to circulate the seal-chamber liquid while the shaft is rotating. Even though the shaft is stationary, heat can continue to enter the seal chamber from the hot pump and process fluid. Natural circulation of cooling may be adequate in well designed systems but must not be assumed. Hot standby, loss of cooling water and startup after shutdown are examples that must be covered in the thermal assessment by the seal supplier.<\/p>\n Other surfaces affected by water quality include seal faces, elastomers, and cooler surfaces. Approval of materials for these items and for water treatment chemicals must be made separately from the approval for the pump casing. Additionally, the boiler feed pump requires to be protected at minimum flow and this must be a true recirculation system as opposed to a seal cooling loop.<\/p>\n The Longgang Pump supply boiler-feed-pumps for chemical and refinery projects. Details of the pump and associated equipment supplied by Longgang for the Qingdao refinery boiler-feed-pump package<\/b><\/u><\/strong><\/a>\u00a0under review are noted. Space must be allowed for future maintenance around the pump and associated plant. Details of the seal system would be better given by means of a General Arrangement and associated Piping drawings rather than by reference to individual plan numbers.<\/p>\nPlan 23 Recirculates Seal-Chamber Liquid<\/b><\/strong><\/h3>\n
![\"Longgang](\"https:\/\/www.longgangpump.com\/wp-content\/uploads\/2026\/11\/Longgang-pump-skid-with-auxiliary-piping.jpg\")
<\/p>\nSimilar Water Temperatures Can Lead to Different Plans<\/b><\/strong><\/h3>\n
Make the Cooling Loop Work on Site<\/b><\/strong><\/h2>\n
Account for Startup, Standby and Water Quality<\/b><\/strong><\/h2>\n
![\"Longgang](\"https:\/\/www.longgangpump.com\/wp-content\/uploads\/2026\/11\/Longgang-boiler-feed-pump-package-on-a-trailer.jpg\")
<\/p>\nSpecify the Complete Seal Package<\/b><\/strong><\/h2>\n