Inverted Bucket Steam Trap

What is an inverted bucket steam trap?

An inverted bucket steam trap is a mechanical steam trap that works by employing the principle of density difference between water and steam. The steam that enters the inverted bucket steam trap makes the bucket float and closes the discharge valve. The condensate enters the inverted bucket steam trap alters the bucket to a sinking weight and opens the trap discharge valve to eject the condensate. The inverted bucket steam trap manufacturers design the trap in a way that makes it possible to vent carbon dioxide and air continuously at the same steam temperature. As the bucket moves down and up in the condensate, a linkage mechanism connected to the bucket opens or closes the discharge valve which traps condensate or allows it to escape. The maximum efficiency is achieved when steam space is kept free from condensate. 

Figure: Inverted bucket steam trap.

How does inverted bucket steam trap work?

As the name suggests, an inverted bucket steam trap is made up of an inverted bucket that is attached to a valve by using a lever mechanism. Inverted bucket steam trap manufacturers design the trap with an air vent at the top. The figure below shows the working of an inverted bucket steam trap as described below: 

1. Initially, the bucket is hanging down which makes it pull the valve off from its usual seat. This makes it possible for the condensate to flow at the bucket’s bottom to fill the body and flow away via the outlet. 
2. In the second step, the steam arrives causing the bucket to float. This makes it rise and shut the outlet. 
3. In the third step, the inverted bucket steam trap shuts until the bucket steam condenses or bubbles via the vent hole at the top of the trap. It later sinks and pulls off the main valve from its seat. The condensate that has accumulated is released and the cycle starts again. 

In step (ii) getting to the trap in the beginning makes the bucket float and closes the valve. The vent hole on the bucket is necessary for allowing air to escape to the top of the inverted bucket steam trap for the final discharge via the main valve seat. The pressure differential and the hole are small making the trap slow when venting air. 

Working of an inverted bucket steam trap

Types of inverted bucket steam trap

Types of inverted bucket steam traps are in terms of materials used to make the body and piping configurations. As such, the types are as discussed below. 

All-stainless steel inverted bucket steam trap

This is an inverted bucket steam trap whose body is made using tamper-proof stainless steel to enable them to stand freezing without damage. These traps can be used in outdoor drips, tracer lines, and services that can be experiencing freezing. It can work in high temperatures of up to 427 ^oC and pressures of 4.5 mega Pascal 

Cast iron inverted bucket steam traps 

These are inverted bucket steam traps made of cast iron material. This type of trap is used for general service at a pressure of around 1.7 mega Pascal and 232 ^oC temperatures. Inverted bucket steam trap manufacturers make these traps with side connections that have basic strainers and top outlet and bottom inlet connections. 

Forged steel inverted bucket steam trap 

This is an inverted bucket steam trap made of forged steel material and used in high temperature and high pressure including superheated steam applications. These traps can withstand very high temperatures of around 560 ^oC and pressures of 18.6 mega Pascal. 

Cast stainless steel inverted bucket steam trap 

These are inverted bucket steam traps meant for corrosive and high-capacity applications. These traps are repairable and can withstand pressures of around 4.7 mega Pascal and 263^oC temperatures. 

Characteristics of an inverted bucket steam trap 

• Dirt and sediments are kept suspended until ejected with condensate. 
• Inverted bucket steam trap drains condensate completely at saturation temperature. 
• They have only two main parts that is bucket and lever mechanism. 
• Inverted bucket steam trap does not cause condensate sub-cooling. 
• It does not tolerate freezing temperatures. 
• Cycles are fully closed or open which can cause noise. 
• Manually primed to enhance water seal. 

Applications of inverted bucket steam trap 

• Used in laundry machines. 
• They are used in steam separators. 
• They are used in the process main drip trap to enhance continuous operations. 
• Heat exchangers without adjusting the steam regulator.
• They are used in areas where condensate needs to be lifted or flow to a wet return line. 
• It is used in tilting kettles and siphons. 
• High-pressure applications. 
• Roller dryers.

Features of inverted bucket steam trap 

• Internal components are made of stainless steel to make them corrosion resistant. 
• The bodies are made of cast iron which is very strong thus enhancing the trap’s long and reliable life. 
• Have a wide range of available seat pressures.
• They have easy-to-remove covers for easier in-line service.
• Designed with an optional strainer to reduce the number of pipeline connections. 
• They are manufactured with an optional vent to enhance faster heating. 

Advantages of inverted bucket steam trap 

• It can withstand high levels of pressure. 
• Has wide tolerance to deter water hammer conditions. 
• These traps can be used in superheated steam applications by use of check valve at the inlet section. 
• Has failure mode always open making it safe when used in applications that need this design such as turbine drain. 
• Inverted bucket steam traps manufacturers apply the concept that makes these traps energy-conserving even in wear cases. These traps can close or open gently which minimizes wear relative to other traps. 
• Made of corrosion-resistant materials. Materials such as stainless steel, cast iron, and forged steel are used to make different types of these traps. These materials are very strong and resistant to corrosion and wear thus being economical. 
• Offers continuous automatic carbon dioxide and air venting without the threat of air binding or cooling lag. 
• Can operate against backpressure. This trap has no severe effect on this trap operation except reducing its capacity due to low differential pressure. 
• Free from dirt. The inverted bucket steam trap is free from dirt since the seat and valve are located at the top far away from large dirt particles that fall to the bottom. 

Disadvantages of inverted bucket steam traps

• These traps eject air very slowly due to small-sized holes at the bucket top face. It is not recommended to enlarge this hole because it would result in the steam passing quickly during normal working. 
• Needs to always have sufficient water in the body to seal around the bucket. If this water seal is lost, the steam will be lost via the outlet valve. This could happen often when there is a sudden steam pressure drop. This can cause part of the condensate in the trap to flash into the steam. As such, the bucket would then not float making it sink, and live steam will pass via the orifice. 
• May need a check valve on the inlet section if the trap has to be used where the plant is expected to have pressure fluctuation. Water and steam can freely flow in their indicated direction but a reverse flow is not possible because the check valve would be strained onto its seat. 
• An inverted bucket steam trap with superheated steam at a high temperature can easily lose a water seal. In such conditions, a check valve would be very necessary. Some inverted bucket steam manufacturers design the trap with a standard integral check valve. 
• These traps are likely to get damaged due to freezing if installation is done in a position exposed to sub-zero ambient conditions. This would need a suitable lagging to help overcome this problem if it is not very severe. 
• Has an orifice meant to work up to certain maximum differential pressure. Subjecting the trap to more differential pressure than recommended will close and thus not discharge condensate. 

Troubleshooting inverted bucket steam trap 

Pressure is very high 

• Orifice enlarged due to wear. Replace it. 
• Gauge pressure from a boiler is malfunctioning. Set a lower reading. 
• Check pressure going into the trap is as recommended. 
• Return line creating a high vacuum line increasing differential pressure. 

The inverted bucket steam trap does not get steam or condensate 

• Pipeline or elbow joints clogged. Check the joints and elbow joints to remove clogged material. 
• Failed valve. Check any failed valve that could alter the flow and replace if necessary. 
• A plugged strainer in front of the trap. Verify if there is a plugged strainer and unblock.

A faulty internal mechanism in the inverted bucket steam trap 

• Check if the trap internal mechanism is broken and repair or replace it as necessary. 

Inverted bucket steam trap body is full of debris 

• Clean strainer to remove dirt. 
• Mount the strainer ahead of the trap. 

Bucket is clogged

• Install trap strainer in front. 
• Clean bucket vent with a scrubbing wire. 

No discharge from inverted bucket steam trap 

• No condensate comes to the trap. It could be due to a broken pipe. Check the siphon pipe. Due to water heater with a vacuum which can prevent drainage. Install vacuum breaker. 

Steam loss 

• The valve is not properly seated. Dirt in the orifice. Remove dirt. 
• Worn trap parts. Check any worn-out parts and replace them. 

Inverted bucket steam trap losing prime 

• Close the inlet trap valve for some minutes, then open it gradually and see if the trap gained its prime. Prime loss can occur due to frequent or sudden pressure drops. Also, verify check valves are working. 

Inverted bucket steam trap having a continuous flow 

• The trap is very small. Replace it with a larger trap. You can also use extra traps in a line. 
• Abnormal water conditions. This could be due to boiler priming or foaming which causes more water flow in steam lines. Rectify conditions in the feed water. 

Trap working but units are not properly heating 

• Install inverted bucket steam traps on each unit. 
• Traps used are small for the task. Install larger-sized trap. 

Inverted bucket steam trap fails if connected to return line 

• The return line is very small. Use a larger return line. 
• Return line blocked. Remove materials causing a blockage. 

Summary 

An inverted bucket steam trap is a mechanical trap that works by employing the concept of density differences between water and steam. Steam enters an inverted bucket and causes that bucket to float closing the discharge valve. The condensate that enters that trap alters the bucket to weight making it sink and open the trap valve to eject the condensate. One advantage of the inverted bucket steam trap is that it can vent carbon dioxide and air continuously at steam temperature.

Inverted bucket steam traps are used in different applications such as high-pressure applications, steam separators, tilting kettles, laundry equipment, heat exchangers among others. Characteristics of inverted bucket steam traps are two moving parts bucket and lever mechanism, open normal failure mode, ability to tolerate water hammer, internal components made of stainless and other strong materials that can resist corrosion. These traps are advantageous in that they can withstand high pressures, can work on superheated steam lines, is safe as their failure mode is always open, is energy conserving with little wear, it is free from dirt relative to other traps, and it can operate against backpressure.