Armstrong 401-SH and 501-SH Series inverted bucket steam traps are specifically designed to overcome the difficult combination of superheat and high pressure/low load service. To survive this severe steam service, Armstrong created an inverted bucket trap with a unique accumulation chamber. The chamber collects sufficient condensate to ensure full discharge cycles. A cup in the chamber floats up and down on the steam inlet tube, sealing it off as the condensate level rises. At the same time as the chamber collects condensate, steam continues to flow under the bucket, making sure that the discharge valve closes tightly until the condensate rises into the trap body and the bucket falls down. The operation is on/off, with no throttling or dribbling.

Features and Benefits

Furthermore, it combines all the advantages of an inverted bucket steam trap:

• High resistance to wear, corrosion, and water hammer with no gaskets.
• A unique leverage system multiplies the force provided by the bucket to open the valve against system pressure.
• The mechanism is located at the top. No dirt can collect on the orifice. Small particles of dirt will be held in suspension until discharged by the full differential purging action.
• The discharge orifice is surrounded by a water seal, preventing live steam loss. Automatic air venting is provided by a small hole in the bucket.
• Inverted bucket traps require no adjustment. They do not allow condensate backup and are resistant to water hammer.

Materials

• Body (401-SH): Carbon steel ASTM A106 Gr. B Sch. 80 pipe
• Body (501-SH): Stainless steel 316L ASTM A312 Sch. 80 pipe
• Internals: Stainless steel 304
• Valve and seat: Titanium
• Connections (401-SH): Stainless steel 304
• Connections (501-SH): Stainless steel 316L

Dimensions and Weights

Model	401-SH	501-SH
Pipe Connections (in)	1/2, 3/4	1/2, 3/4
Pipe Connections (mm)	15, 20	15, 20
"A" Diameter (NPT, BSPT or SW)	4 in (100 mm)	4 in (100 mm)
"B" Height (NPT, BSPT or SW)	11 in (275 mm)	13-9/16 in (344 mm)
"C" Diameter (Flanged)	4-5/8 in (117 mm)	4-3/4 in (121 mm) to 5-1/8 in (130 mm)
"D" Height (Flanged)	15-1/8 in (384 mm)	18-3/16 in (462 mm) to 18-11/16 in (475 mm)
Weight NPT, BSPT or SW	12 lb (5.5 kg)	15 lb (7 kg)
Weight Flanged	15 lb (6.7 kg)	29 lb (13 kg)

Operating Cycle

Trap Draining Drip Leg on Steam Main With the steam feed tube to the trap chamber sealed, condensate flows through the condensate feed tube (from accumulation chamber) into the trap chamber. This sinks the inverted bucket, which opens the discharge valve, cycling the trap.

Cycling – Discharge Valve Wide Open

Cycle Ending As the level of condensate in the accumulation chamber falls, the cup sealing the steam feed tube moves downward, opening a passage for steam to flow into the trap chamber.

Trap Closed As steam begins to flow through the accumulation chamber and up the steam feed tube under the inverted bucket in the trap chamber, the discharge valve closes tightly.

Cycle About to Repeat As the level of condensate rises in the accumulation chamber, the cup floats up until it again seals the steam feed tube, and the cycle repeats.

Installation Recommendations

What little condensate there is on superheat and high pressure/low load service usually forms in drip legs and in the traps themselves. Therefore proper piping and drip legs of adequate size and diameter are essential for the successful operation of the Armstrong superheat trap.

Drip Leg Sizing

The properly sized drip leg will capture condensate. Too small a drip leg can actually cause a venturi “piccolo” effect where pressure drop pulls condensate out of the drip leg and trap.

Recommended Steam Main and Branch Line Drip Leg Sizing

Steam Main Size (in)	Drip Leg Diameter (in)	Supervised Warm-Up Min Length (in)	Automatic Warm-Up Min Length (in)
1/2	1/2	10	28
3/4	3/4	10	28
1	1	10	28
2	2	10	28
3	3	10	28
4	4	10	28
6	4	10	28
8	4	12	28
10	6	15	28
12	6	18	28
14	8	21	28
16	8	24	28
18	10	27	28
20	10	30	30
24	12	36	36

Insulation Warning

Because insulation reduces the condensate available to the trap for the maintenance of the water seal, leave the trap and 2-3 feet of inlet piping uninsulated. This will help extend trap life. If personnel protection is required, install a wire cage.

Troubleshooting

Whenever a trap fails to operate and the reason is not readily apparent, the discharge from the trap should be observed. If the trap is installed with a test outlet or discharges to atmosphere, this will be a simple matter - otherwise, it will be necessary to break the discharge connection.

Cold Trap - No Discharge

• If trap fails to discharge condensate: Wrong pressure originally specified, PRV out of order, pressure gauge on boiler reads low, or orifice enlarged by normal wear.
• No condensate or steam coming to trap: Stopped by plugged strainer ahead of trap, broken valve in line to trap, or pipe line/elbows plugged.

Hot Trap - No Discharge

• No condensate coming to trap: Trap installed above leaky by-pass valve, or bottom chamber not yet full. These special traps will not discharge until enough condensate accumulates. This may take 15 minutes.

Steam Loss If the trap leaks or blows live steam, trouble may be due to:

• Valve may fail to seat: Piece of scale lodged in orifice, or worn parts.
• Trap may lose its prime: If the trap is blowing live steam, close the inlet valve for a few minutes. Then gradually open. If the trap catches its prime, the chances are that the trap is all right. Prime loss is usually due to sudden or frequent drops in steam pressure.
• Trap may be venting air and noncondensibles: To test, take a bucket of cold water and submerge the end of the discharge pipe. If bubbling continues, it is air. If bubbles collapse and disappear, the valve is leaking.

Continuous Flow

• Trap too small: A larger trap, or additional traps should be installed in parallel. High pressure traps may have been used for a low pressure job.
• Abnormal water conditions: Boiler may foam or prime, throwing large quantities of water into steam lines. A separator should be installed or else the feed water conditions remedied.