Wave Face Seal Technology Improves Efficiency and Reliability of Boiler Service

Challenge

Boiler circulating pumps are critical equipment in steam power generation plants, as they circulate boiler water at pressures approaching 207 bar (3000 psi) and temperatures of 315 to 370°C (600 to 700°F). Under these extremes, the pumps can be a costly source of downtime and frequent maintenance requirements. There are also efficiency considerations.

Traditionally, feedwater also cools braided packing and mechanical seals used in boiler circulating pumps. Each gpm of feedwater used for cooling can represent a waste of 2240 BTU/min (0.039374 MWe) that can’t be used to make electricity. Over a year a single gpm represents 1.2 trillion BTU (21,000 MWe) wasted energy – the equivalent of 3.21 railroad cars of coal.

Solution

In the late 1970s and early 1980s, single mechanical end-face seals and later pressure-staged multiplier mechanical seals replaced braided packing. Payback periods were easily justified with reduced energy loss, reduced water makeup costs and maintenance costs.

With the introduction of wave face technology it is possible to seal a 207 bar (3000 psi) discharge pressure in boiler service using only one set of faces without pressure staging or injection cooling. These customer-designed seals can feature either a single arrangement or a dual, non-pressurized tandem arrangement in which the secondary set of faces can act as a full safety back-up seal. It utilizes an API Plan 23 flush.

Wave face technology translates to improved reliability in rotating equipment because the seal support systems are less complicated compared with pressure-staged seal designs. Wave face seals maximize the efficiency of steam electricity generation because no boiler feedwater is needed as a cooling fluid. As a result, utilities have the potential to save in excess of U.S. $500,000 a year simply by upgrading conventional single mechanical seals. Wave face seals optimize generating unit uptime and system output.