Armstrong EDD-6 (Double Duty® 6) steam trap/pump combination offers a low profile solution to draining heat exchangers in various applications. The Double Duty® 6 is a CE marked carbon steel vessel according to PED 97/23 EC (or ASME code stamped for DD-6). It offers the versatility of combining a pump within a steam trap to aid in condensate drainage under all operating conditions.

Application

When there is modulating control on heat exchange equipment, there is a possibility that the system will stall (no longer be able to drain condensate). If only a steam trap is used, condensate could flood the heat exchange equipment causing corrosion, water hammer, and poor temperature control. The Double Duty™ has a steam trap with an integral pump to prevent the system from stalling. If the condensate floods the body of the Double Duty™ and reaches its upper trip point, high pressure steam will enter the body and push the condensate out. This prevents condensate from accumulating in the heat exchange equipment.

Features

• Economical, non-electric operation: Uses steam motive with no electricity or special mechanical seals required.
• Low-maintenance operation: No leaking seals, impeller or motor problems. No NPSH issues.
• Space-saving size: Low-profile body fits in tight spaces while allowing minimal fill head.
• Lower installation costs: Single trade installation.
• Peace of mind: Intrinsically safe. Can be used in pits or sumps without fear of electrocution or circuit breaker defaults.
• Carbon Steel durability: Rugged construction material means long service life.
• Efficiency: A closed loop means no motive or flash steam is lost. All valuable heat is captured and returned to the system.
• Accessible Mechanism: The pump mechanism is attached to the cap which can be removed from the body without taking it out of the condensate line, and the steam trap mechanism can be accessed through the cap opening.

Operation

Operating as a trap (system pressure greater than back pressure)

As the condensate flows through the inlet check valve, the trap and pump floats become buoyant and rise with the fluid level. The upward movement of the float causes the trap valve to open. If the system pressure is greater than the back pressure, the condensate will flow through the steam trap valve into the condensate return.

Operating as a pump (system pressure less than or equal to back pressure)

If the system pressure is less than the back pressure, liquid floods the body. When the condensate reaches the upper trip point of the pump mechanism, the motive inlet valve opens and the vent valve closes. The open motive valve allows the motive fluid to enter and pressurize the body. The pressure inside the body shuts the inlet check valve and when it is greater than the back pressure, pushes the water through the discharge check valve into the condensate return line. The float lowers with the water level and when it reaches the lower pump trip point, the motive inlet valve closes and the vent valve opens. This relieves the pressure in the body and allows it to fill again.

Maximum Operating Conditions & Materials

• Maximum allowable pressure: 14 bar @ 204°C (200 psig @ 400°F)
• Maximum operating pressure: 14 bar @ 204°C (200 psig @ 400°F)
• Minimum Motive Differential: 10 psi

Component	Material
Body	Carbon Steel (ASME Code Stamped or CE Marked)
Springs	Inconel X-750
Internals	All stainless steel

Physical Data

Dimension	EDD-6 (DIN)	EDD-6 (ANSI)
"A"	887 mm	920 mm
"B"	DN40	1-1/2"
"C"	DN25	1"
"D"	1" BSPT	1" NPT
"E"	1/2" BSPT	1/2" NPT

(Note: All dimensions and weights are approximate. Use certified print for exact dimensions.)

Capacities

Pump Capacities

Motive (bar)	Back Pressure (bar)	Capacity (kg/hr)
1	0.34	1 089
1.7	0.34	1 361
3.5	0.34	1 814
5	0.34	2 041
7	0.34	2 087
8.5	0.34	2 132
10.34	0.34	2 177
12	0.34	2 177
14	0.34	2 087
1.7	1	907
3.5	1	1 270
5	1	1 542
7	1	1 633
8.5	1	1 678
10.34	1	1 724
12	1	1 633
14	1	1 588
2.5	1.7	816
3.5	1.7	1 043
5	1.7	1 315
7	1.7	1 361
8.5	1.7	1 361
10.34	1.7	1 315
12	1.7	1 134
14	1.7	1 043
3.5	3	635
5	3	907
7	3	1 089
8.5	3	1 134
10.34	3	1 134
12	3	816
14	3	771
5	4	680
7	4	816
8.5	4	907
10.34	4	771
12	4	680
14	4	635

Note: Published capacities are based on the use of external check valves supplied by Armstrong. Fill head measured from drain point to top of pump case.

Trap Capacities

Differential Pressure (bar)	Capacity (kg/hr)
0.14	4 309
0.34	5 625
0.7	6 804
1.7	9 253
3.5	10 206
5.2	10 206
6.9	10 206
10.3	10 206
13.8	10 206

Capacity Conversion Factors for Other Filling Heads

Filling Head (mm)	0	150	300	600 or greater
Double Duty EDD-6	0.7	1.0	1.08	Consult factory

Discharge per cycle typically 13.6 litres (3.5 gallons) for EDD-6. Note: Fill head measured from drain to top of cap.

Installation

1. Filling head: Install the DD6 below the equipment being drained. Fill head is the distance from the top of the cap to the bottom of the receiver. The standard fill head for the DD6 is 6 inches (150 mm).
2. Liquid reservoir: Liquid flowing from the heat exchange equipment must be stored during the pump discharge cycle. A liquid reservoir or receiver should be installed above the unit to prevent flooding the equipment.
3. Vent piping: The vent pipe must be pitched to self drain. The vent connection is 1” NPT/BSPT.
4. Replace any temporary plastic plugs with appropriate fittings.
5. Gauge glass connections are ½” NPT/BSPT and 10” center to center.

Installation Instructions

• Before installing make sure the piping is clean and free of debris. Debris can affect proper operation and performance.
• The DD6 must be installed with the vent and motive vertical and the condensate inlet and outlet horizontal. The product will not function properly if not installed in the correct orientation.
• When connecting pipes, unions or flanges should be used close to the DD6 connections to reduce maintenance time.
• Attach strainer with blow down valve on motive steam inlet.
• Attach check valve on condensate inlet and discharge.
• Attach the motive drip trap to the steam motive line.

Start-up Procedures

Caution

Make sure all connections are secure before opening valves. Open valves slowly to reduce the chance of water hammer.

1. Open isolation valve(s) in condensate discharge.
2. Open isolation valve in equalizing line.
3. Open motive isolation valve. Confirm that the steam does not flow into the pump body or equalizing line by checking pressure gauges.
4. Open the isolation valve on the thermostatic air vent.
5. Open the isolation valve on the condensate inlet.
6. The start-up is complete if the Double Duty Six performs trap operation or pump operation and is confirmed by use of the gauge glasses and pressure gauges.

Maintenance and Troubleshooting

Most failures occur because of debris in the piping.

Caution

Before starting any maintenance make sure the Double Duty™ 6 is completely isolated from the system. Make sure the system is at atmospheric pressure.

Problem	Diagnosis	Solution
Condensate not discharging	Inlet isolation valve closed	Open valve
	Pump inlet and outlet switched	Re-pipe
	Motive inlet and vent switched	Re-pipe
	Discharge isolation valve closed	Open valve
	Equalizer line isolation valve closed	Open valve
	Motive pressure not adequate	Adjust pressure
	Motive inlet isolation valve closed	Open valve
	Motive strainer clogged	Clean or replace
	Air vent damaged	Replace air vent
	Motive pressure exceeds pump rating	Adjust pressure
	Outlet check valve installed backward	Install check valve properly
	Outlet check valve does not open	Replace
	Inlet check valve does not open	Confirm lack of pressure in body
	Inlet check valve is not completely closed	Disassemble and clean check valve
	Vent valve leaks	Disassemble, clean and inspect - replace defective parts
	Motive steam valve leaks	Disassemble and replace inlet valve
	Float damaged	Disassemble and replace float
Motive steam remains on	Motive steam valve leaks	Disassemble and clean or replace
	Mechanism not assembled properly	Assemble so the motive valve is inserted in motive seat
Steam leaks out of body	Body gasket leaks	Replace gasket
	Plugs leak	Remove, add thread sealer and reinstall