Products
Pumps

Condensate Return Pumps

Condensate Return Pumps are used for returning the hot condensate back to the feedwater holding tank in the boiler room. Pumps are required to overcome gravity, pressure drops from long piping runs, and back pressures in return lines. Condensate Return Pumps are either electrically-driven centrifugal pumps or pressure motive pumps (PMPs) that use steam pressure as the motive force to pump the condensate.

Boiler Feed Pumps are always electrically-driven centrifugal pumps that are regulated by the boiler control system to pump condensate from the feedwater holding tank into the boiler.

Pressure Motive Pumps (PMPs)

Pressure Motive Pumps (PMPs) are pressure-driven pumps which return condensate back to the boiler room; using steam pressure as the motive force. PMPs can be supplied as individual pump – which include a pump tank, the internal pump mechanism, and a set of inlet and outlet check valves – or as a packaged system which includes the vented receiver tank (to collect condensate) mounted on a common base.

Models of PMPs are designated by both their Inlet and Outlet check valve size. For example a 3x2 PMP has a 3” inlet and 2” outlet. Increasing check valve size will increase overall pump capacity. Other factors that affect pump capacity are Fill Head height, Motive Steam Pressure, and system Back Pressure. The PMP pump tanks are available in either Ductile Iron, Carbon Steel, or Stainless Steel depending on Model.

Pump Tank Model/Materials:
PMPC = Ductile Iron
PMPF = Fabricated Steel
PMPSS = Stainless Steel
PMPNT = Ductile Iron or Stainless Steel

Complete Package System (PMPs with a Vented Receiver)

The installation of a Pressure Motive Pump (PMP) requires a vented receiver for initial collection of the condensate. The receiver volume must be adequate to temporarily store enough condensate during the pumps discharge cycle when the pump tank is pressurized with steam. Vent line size must be sufficient to properly vent the flash steam and maintain 0 psig inside the receiver. Vent line size is based on both condensate volume and condensate temperature entering the receiver.

Complete Packaged Systems are available. Simplex, Duplex, and Triplex systems include stand-alone PMP pumps with check valves and a vented receiver mounted on a common base. All components of the system are properly sized and pre-piped together; requiring only four connections to be made in the field. Duplex & Triplex systems can be used for increased capacity or in the event of a single pump failure

Electric Pumps

Electric Condensate Return Pumps are designed to work intermittently, discharging condensate only when the receiver tank is nearly full. This is accomplished with a float switch. Watson McDaniel electric pumps are offered in Simplex and Duplex models. Also available with control panels.

W4100 Simplex & Duplex with Steel receivers
W4200 Simplex & Duplex with Cast Iron receivers
W4300 Simplex & Duplex with Stainless Steel receivers

Condensate Return System

Shown below is a simplified view of a steam system from steam generation to condensate return. Steam generated by the boiler travels through the steam distribution lines supplying steam to various pieces of process equipment. The steam flowing to this equipment is separated from the condensate return lines by steam traps. Relatively small steam traps, referred to as “Drip traps,” are used for optimization and protection of steam systems by draining condensate from steam distribution lines into the condensate return line. Process Applications refer to draining condensate from the actual process using the steam into the condensate return line. The steam traps used in these applications have relatively high condensate capacity and are referred to as “Process traps”. A large plant may have many separate pieces of process equipment and thousands of drip traps discharging condensate into the condensate return lines. On effifficiently run steam systems, this condensate is returned back to the boiler for reuse.

Condensate Return Pumps

In certain cases, the steam pressure of the system may be sufficient to push the condensate through the steam traps and condensate return lines, back to the condensate holding tank in the boiler room. In most practical situations, however, one or more condensate return pumps are required to assist in overcoming gravity, pressure drops from long piping runs, and back pressures in return lines. Condensate Return Pumps are either electrically-driven centrifugal pumps or non-electric mechanical pumps that use steam pressure as the motive force to pump the condensate. Non-electric pumps are referred to as Pressure Motive Pumps (PMPs).

What is the purpose of a Vented Receiver?

Condensate from several different sources that are operating at different pressures are often discharging into the same condensate return line. The discharge from one of the higher pressure sources increases the pressure in condensate return line and restricts the flow of condensate form other process application operating at lower pressures. By connecting the condensate return line to a vented receiver, the pressure in the return line will be effectively equalized to atmospheric pressure, allowing condensate to freely drain from all condensate sources. The receiver and vent must be adequately sized to allow for the discharge of flash steam without building up pressure. Higher condensate pressures or loads would require larger receiver and vent sizes. Condensate then flows by gravity from the vented receiver to the condensate return pump.

Advantages of a Packaged Pump System

Packaged Systems ensure that all components and ports are sized correctly, and that installation will be simplified with only four connections to be made in the field. Simplex, Duplex, and Triplex Systems include PMP pumps with check valves and a vented receiver tank, mounted on a steel base and frame. Multiple PMPs can be used for increased capacity, pump failure or for system redundancy.

Boiler Feed System

Shown below is a simplified view of a steam system from steam generation to condensate return. Condensate is separated out by the steam traps and is returned to the boiler feed tank either by gravity or a condensate return pump.The boiler feed pump is used to pump feedwater into the steam boiler. The feedwater may be freshly supplied make-up water or returning condensate. The pump must generate sufficient pressure to overcome the pressure of the boiler.

Operation of a Boiler Feed System

For Boiler Feed applications, the operation of the pump is controlled by the water level control system on the boiler. When the boiler requires water, the pump switches on pumping water from the receiver into the boiler. The receiver tank also contains an internal make-up water valve actuated by a stainless steel float. If the amount of condensate being returned to the receiver tank is inadequate to supply the boiler, additional make-up water is added to the receiver tank. This condition may occur when more steam is being produced than condensate being returned; common at system start-up.

An overflow pipe is used to dump excess condensate to drain during times when less boiler feed water is required than the amount of condensate being returned. Larger boiler feed tanks may be advantageous to keep systems in balance.

Boiler Feed Pumps
W4100 Simplex & Duplex with Steel receivers
W4200 Simplex & Duplex with Cast Iron receivers
W4300 Simplex & Duplex with Stainless Steel receivers

Pump-Traps

A Model PMPT pump-trap contains a pump mechanism with a steam trap internal to the pump body. When the process steam pressure is greater than the back pressure pump-traps will function exactly like a standard float operated trap. If the process steam pressure falls below back pressure, condensate will be discharged by the pump. Pump-traps allow for complete drainage of condensate from the heat exchanger under all operating conditions including vacuum.

Pump-Trap Applications

When steam pressure in a Heat Exchanger is less than the back pressure on the discharge side of the steam trap, the condensate backs up, causing inconsistent heat transfer and potential waterhammer. This condition is referred to as Stall. This frequently occurs on applications where a temperature control valve is used to supply steam to a Heat Exchanger based on product temperature. The temperature control valve increases and decreases steam flow to the Heat Exchanger to satisfy the temperature set point. When system demand is high, the steam pressure in the Heat Exchanger is maybe adequate to overcome system back pressure; however, when system demand decreases, steam pressure to the Heat Exchanger must also decrease and can fall below the back pressure, causing condensate to back up into the Heat Exchanger. To prevent condensate back up under stall conditions, a pump-trap must be used in place of a steam trap.

Problem: Condensate Backs Up Into Heat Exchanger

The diagram shows a temperature control valve delivering steam to a Heat Exchanger that is using steam to heat water. Condensate formed in the heat exchanger is being discharged through the steam trap into the condensate return line. This particular application demonstrates what happens when the return line is elevated and/or pressurized. The plant steam pressure on the inlet side of the control valve would be adequate to purge (push) the condensate through the trap and into the return line. However, the steam pressure in the heat exchanger is controlled by the valve and is dependent on the demand of the system. When the demand for HOT water is low, the steam pressure in the Heat Exchanger falls below the back pressure and the system backs up with condensate, creating unstable temperature control and waterhammer. This undesirable condition, referred to as Stall, occurs when the steam pressure in the heat exchanger falls below the back pressure due to a decrease in the demand (flow rate) of hot water.

Solution: Use a Pump-Trap to Avoid Condensate Back-up & Improve Temperature Control

To eliminate condensate backing up (STALL), the standard float trap is replaced with a PUMP-TRAP. When steam pressure in the Heat Exchanger is greater than the back pressure, the steam pressure will push the condensate through the Pump-Trap and it functions like a standard float-operated trap. When the steam pressure to the Heat Exchanger drops below the back pressure, the condensate backs up inside the PUMP-TRAP, raising the float. When the trip point of the mechanism is reached, the high-pressure steam valve will open to drive the condensate out.

Pump with Internal Steam Trap

PMPT Simplex & Duplex with Stainless Steel receiver

Pump with External Steam Trap

WPT Simplex & Duplex with Steel receivers

Complete - PMP Pump System
Used for pumping condensate back to the boiler room using steam as the motive force. Simplex, Duplex, and Triplex packaged systems include stand-alone pumps and check valves with a vented receiver tank, mounted on a steel base and frame.
Stand Alone Pressure Motive Pump
Pressure Motive Pumps (PMPs) are pumps which return condensate back to the boiler room using steam pressure as the motive force. These stand alone units require a separate vented receiver in order to operate.
Electric Pumps
Watson McDaniel’s Condensate Return and Boiler Feed Pumps are equipped with Cast Iron bodies and Bronze Impellers. The pump receiver tanks are available in either Carbon Steel (W4100), Cast Iron (W4200), or Stainless Steel (W4300) in Simplex or Duplex configurations.
Pump-Trap Combinations
A Pump-Trap is used in place of a Steam Trap to drain condensate from a process application when the steam pressure in the process is not sufficient to push the condensate thru the steam trap and into the condensate return line.
Sump Drainers
Sump drainers are similar to the standard PMP models except that they discharge the condensate vertically upwards. This piping configuration allows them to easily fit into below ground sump pits with limited space.
Accessories for PMPs
  • Gauge Glass
  • Cycle Counter
  • ASME Code Stamp
  • Insulation Cover
  • Pre-pipe
  • Replacement
  • Mechanisms
  • Rebuilt
  • Mechanisms
  • Retrofit