Testing Armstrong Steam Traps

For maximum trap life and steam economy, a regular schedule should be set up for trap testing and preventative maintenance. Trap size, operating pressure and importance determine how frequently traps should be checked.

How To Test
Test valve method is best. Fig 3-1 shows correct hookup, with shut-off valve in return line to isolate trap from return header.

Here is what to look for when test valve is open.

A. Intermittent discharge - trap is okay.
B. "Flash" steam - do not mistake this for a steam leak through the trap valve. Condensate under pressure holds more heat units - btu's - per pound than condensate at atmospheric pressure. When condensate is discharged, these extra heat units re-evaporate some of the condensate.
C. Dribble or semi-continuous discharge - trap is okay. This type of discharge is caused by air mixed with steam or a light condensate load.
D. Continuous steam blow - trouble.
E. Continuous condensate flow - trouble.
F. No Flow - possible trouble.

Pyrometer Method of testing. This method of testing is still used today, however current research has shown that information from this method is not as valid as the ultrasonic stethoscope.

Listening Method of Testing. The ultrasonic stethoscope is the most accurate and up-to-date device available for testing traps today. An ultrasonic stethoscope can be used to listen to the outlet of the trap and "hear" the flow. It should be remembered that an ultrasonic stethoscope helps to detect the need for quick preventive maintenance.

Inverted Bucket Air Trap Operation. There is an intermittent air loss through an inverted bucket trap draining water from compressed air. This is the air that passes through the small vent in the top of the bucket and amounts to approximately 10 cu. ft. of free air per hour. When the trap has a lot of water to handle, the air loss is materially reduced. All inverted bucket air traps must be primed before starting.

INSPECTION AND REPAIR

Frequency: All repairable traps should be opened at least once a year to check the operating mechanism.

Valves and Seats.  If the valve seat has a sharp smooth edge, and if there is a narrow bright ring all the way around the ball valve, chances are that the valve is tight. Valves and seats which have become wire drawn or badly grooved from wear should be replaced. Do not use a new seat with an old valve or vice versa. Valves and seats are factory-lapped together in matched sets for perfect fit.

Years of experience have proved that when valves and seats have worn enough to require renewal, a new lever and guide pin assembly should also be installed to get maximum performance from the new valve parts.

Valve Seat Installation.  When installing valve seats in Armstrong traps, do NOT use any pipe dope or lubricant of any kind on the seat threads.  The joint is made, not by the threads, but rather by the contact between the ground end of the valve seat and the beveled seating area at the bottom of the tapped hole. See Fig. 11-1. Make sure that this seating area is perfectly clean.

Fig. 11-1. Important! Valve seat seal is made at point of contact indicated, not by threads. Be sure to read paragraph above.

Replace Lever and Guide Pin Assembly. When new valve parts are used with an old lever, bucket travel, valve opening and trap capacity are reduced. With used and worn guide pins, the valve is not guided as closely to its seat. Poor guidance develops leaks quickly because the valve can strike the side of the seat instead of the corner.
When you install a new mechanism less bucket or a pressure change assembly, you make the trap as good as new.

Alignment of Guide Parts. To check the alignment of the guide pins, hold the lever assembly against the valve seat with the valve contacting its seat, and the two fulcrum points resting on the face of the seat. When the lever is held in this position, the guide pins should be central in the guide pin holes. See Fig. 12-1. There should be equal side-to-side movement of lever as shown in Fig. 12-2 and Fig. 12-3. It is a very simple matter to bend the pins until they are centrally located. Care should be taken so that the pins will remain perpendicular to the guide pin plate so that the lever can drop until it rests on the guide pin hooks.

Fig 12-1 shows CORRECT ALIGNMENT of guide pins. When correctly aligned, lever can be moved sideways the same distance to the right (Fig. 12-2) as to the left (Fig. 12-3).

Fig 12-4 & 12-5 show two examples of INCORRECT ALIGNMENT. Guide pins should be bent in the direction of the arrows until they center in holes shown in Fig. 12-1.

Guide Pin Assembly Installation. Install with guide pins pointing away from the adjoining gasket surfaces as shown in Fig 12-6.

The Lever Assembly is hooked over the guide pins. In a few sizes of traps, particularly at low pressures, the valve lever assembly must be slipped on the guide pins before the guide pin assembly is fastened into position.

Buckets. Cracked or corroded buckets should be replaced.

Fig. 12-6. Guide Pin Plate Locations. Pins always point away from adjoining Gasket Surfaces.

Thermic Buckets. Hold over a steam jet or lighted match to see that disc seats properly when bi-metal strip is heated.

Dirt In Trap. Remove all sediment and other dirt from the trap body. The mechanism may require cleaning by immersing in approved cleaning fluid. Model 1010, 1810 and 2010 Series Stainless Steel traps may be back flushed with compressed air or water under pressure to clean them. If there is an exceptional amount of dirt, install a strainer ahead of the trap. The strainer will have to be blown down and cleaned every 3-6 months, or as conditions warrant.

By-Pass Valve Inspection. It traps are installed with a by-pass, it is highly important that the by-pass valve be checked to make sure it is perfectly steam tight. If the trap can be operated without the by-pass, by all means remove it. Avoid the practice of opening by-pass valves and leaving them open.

Internal Check Valve Installation. Since November, 1946, all Armstrong trap bodies have been tapped on the inside to take Armstrong spring-loaded check valves. To install one of these check valves after a trap has been installed in the line, simply remove the trap cap and the extended inlet tube from the body and screw the check valve, tube and coupling. This does NOT apply to Model 1810, 1010 or 2010 Series Stainless Steel traps.

Check Valve Inspection. Make sure that check valves ahead of traps, in traps, or in return lines, are tight and in good condition.

Pressure Changes. An Armstrong Steam Trap will operate at any pressure lower than the maximum for which it is furnished. The maximum pressure depends upon the diameter of the discharge orifice used in each size of trap. If it is necessary to change the working pressure of the trap to obtain greater capacity at lower pressures, or to enable the trap to work at higher pressures, a complete pressure change assembly (PCA) is required. This applies to all Armstrong inverted bucket traps except the Model 1810, 2010 and 1010 Series Stainless Steel traps where the complete trap needs to be replaced. The pressure change assembly (PCA)  consists of a valve seat, a valve retainer, a valve lever with valve, guide pin assembly and (2) two screws. The diameter of the valve seat is stamped on the face of the seat itself, on the valve lever, and on the guide pin assembly. Parts having different stampings should never be used together.

A valve lever and guide pin assembly are matched with the valve and seat to obtain the maximum possible leverage and trap capacity. At low pressure a low leverage is necessary to obtain full opening of the large orifice. As the orifice size decreases, less valve travel is required, hence, higher leverages can be employed. Because of this highly efficient leverage system, it is usually possible to handle a given job with an Armstrong Trap having pipe connections one size smaller than those of other makers.

Fig. 14-1 Diameter of orifice is stamped on valve parts.

How to Order Repair Parts. For all operating mechanism parts, specify trap number and maximum operating pressure or orifice size. For gaskets, specify trap model number. For body and cap, specify trap model number. For body and cap, specify trap model number and size of pipe connections.

Trouble Shooting

The following summary will prove helpful in locating and correcting nearly all steam trap troubles. Many of these troubles are in reality systems troubles rather than trap troubles. 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, 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, then:

A. Pressure may be too high.
  1. Wrong pressure originally specified.
  2. Pressure raised without installing new pressure change assembly (PCA).
  3. PRV out of order
  4. Pressure gage in boiler reads low.
  5. Orifice enlarged by normal wear.

B. No water or steam coming into trap.
  1. Stopped by plugged strainer ahead of trap - or plugged screen in integral strainer traps.
  2. Broken valve in line to trap.
  3. Pipe line or elbows plugged.

C. Worn or defective mechanism. Repair or replace as required.

D. High Vacuum in return line. Increases pressure differential beyond which trap may operate. Install correct pressure change assembly for pressure differential encountered.

E. Trap body filled with dirt. Install strained or remove dirt at source.

F. Bucket vent filled with dirt. Prevent by:
  1. Installing strainer.
  2. Enlarging vent slightly.
  3. Using bucket vent scrubbing wire.

Vent Scrubber. If the bucket vent should be closed by an oil film, either enlarge the vent or install a scrubbing wire. For vent enlargement, first try a No. 46 drill. If this is not enough, then use a No. 42 drill. Make scrubbing wire as shown in Fig 16-1 to the length shown in Table 16-1. The hole in the center rib of the trap should be 5/32". Enlarge vent with No. 37 drill.

Fig 16-1 Vent scrubbing wire for use when oil plugs vent. Trap inlet tube must be removed.

Hot Trap - No Discharge

A. No water coming to trap.
  1. Trap installed above leaky by-pass valve.
  2. Broken or damaged siphon pipe in siphon drained cylinder.
  3. Vacuum in heat exchanger coils may prevent drainage. Install a vacuum breaker between the heat exchanger and the trap.

Steam Loss. If the trap blows live steam, trouble may be due to any of the following causes:

A. Valve may fail to seat.
  1. Piece of scale lodged in orifice.
  2. Worn valve parts.

B. Trap may lose its prime.
  1. 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.
  2. Prime loss is usually due to sudden or frequent drops in steam pressure. On such jobs, the installation of a check valve is called for. If possible locate trap well below drip point.

Continuous Flow. If the trap discharges continuously, check the following:

A. Trap too small.
  1. A larger trap, or additional traps in parallel should be installed.
  2. High pressure traps have been  used for a low pressure job. Install correct size pressure change assembly (PCA).

B. Abnormal water conditions.
  1. Boiler may foam or prime, throwing large quantities of water in steam lines. A separator should be installed or have the feed water conditions remedied.

Sluggish Heating. When trap operates satisfactorily but units fail to heat properly:

A. One or more units may be short-circuiting and the remedy is to install a trap on each unit.
B. Traps may be too small for job even though they may discharge intermittently. Try next-size-larger trap.
C. Trap may have insufficient air-handling capacity, or air may not be reaching trap. In either case, use auxiliary air vents. Use of thermic buckets may help.

Mysterious Trouble. If trap operates satisfactorily when discharging to atmosphere, but trouble is encountered when connected with return line, check the following:

A. Back pressure may reduce capacity of trap.
  1. Return line too small (trap hot).
  2. Other traps may be blowing steam (trap hot).
  3. Atmospheric vent in condensate receiver may be plugged (trap hot or cold).
  4. Obstruction in return line (trap hot or cold).
  5. Excess vacuum in return line (trap cold).

Imaginary Troubles. If it appears that steam escapes every time trap discharges, remember: Hot condensate forms flash steam when released to lower pressure, but flash steam usually condenses quickly in the return line.

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