What is a globe check valve?
A Globe check valve is a type of valve that is used to ensure fluid flow does not reverse. This type of valve combines the design of a globe valve and check valve to produce a superb valve that cannot allow flow backwards. The Globe check valve employs a disc to control fluid flow. The valve disc works to stop flow reversing. This type of valve has two openings in the valve body. One opening is where the media enters the valve and the other is where the media leaves the valve. In most cases, globe-check valves work automatically that is they are rarely controlled by a person. These valves are used in different applications such as cooling and heating systems, boiler, and water systems among others. In most cases, like in boiler applications, these valves prevent steam backflow automatically. Globe check valves are meant to enhance pipeline safety by ensuring no fluid reverses which can damage pump. They serve to open and stop fluid flow. These valves are not used as regulating valves.
Figure: Globe check valve.
Components of globe check valve
The valve body is the main component of a globe check valve. This is because the valve body houses internal components of the globe check valve such as spring, disc, and seat. The valve must be strong to withstand the pressure associated with the fluid. If the strength of the valve body is lower than the internal stresses due to fluid pressure, the valve body can get damaged. This calls for certainty when purchasing the globe check valve to ensure it will withstand the internal fluid flow pressure. Also, the valve body needs to be strong enough to withstand temperatures associated with the fluid. This is very necessary especially for this globe check valve as it is often used in boilers where steam temperatures could be very high. If the valve body is made of material with low-temperature capabilities, it is likely to give in to the temperatures and become thermally distorted.
The bonnet in a globe check valve is used as a cover to the valve body. The bonnet is connected to the valve body using bolts and nuts or by use of screws. When assembling the globe check valve, the internal components of the valve are first assembled in the valve body and finally, the bonnet is attached to the valve body. This helps to hold the valve body and the internal components together tightly. When the valve operator needs to check internal components of the valve, he/she has to first unbolt/unscrew the bonnet to access those components.
The seat in a globe check valve is an internal component that contacts the valve disc to a tight seal. The seat could be a hard seat or a soft seat. The hard seat is made of metallic material and it tends to have some degree of leakage. Soft seat is made of soft material like elastomers and PTFE based on the maximum fluid temperature. Soft seats rarely experience leakage when closed but are limited to high-temperature operations.
This is a movable component in the valve which closes the valve to restrict fluid flowing in a reverse direction. The disc moves linearly to close the fluid flow.
Inlet and outlet ports
These are passages where the fluid enters the valve and where the fluid leaves the valve. Between the inlet and outlet valve, there is the disc. The globe check valve is connected to the piping systems through these ports. The connection methods used include flanges, threading, compression fittings welding among others.
Spring is used to shift the disc to the valve seat to ensure the valve is closed and fluid cannot reverse. During excessive pressure, the spring is compressed forcing the valve to open. The springs used are coil springs. Such springs are made using materials such as stainless steel, zinc-plated steel which are strong and which can withstand high temperatures.
Trim refers to the internal components of the valve. These components include seat, spring, seating surface, disc, bushing, and other surfaces that contact the fluid. All these parts are very important as they work together to ensure the globe check valve works effectively as expected without leakages.
Figure: Components of globe check valve.
How does a globe check valve work?
When the globe check valve has fluid flowing as shown in the arrow below, the disc is lifted from the seat. In this case, fluid pressure allows the fluid to move forward. When in the opposite direction, the fluid and spring push the disc onto the valve seat and it closes the connection restricting backward fluid flow.
Figure: Globe check valve working to enhance forward flow only.
A globe check needs minimum differential pressure between the inlet and outlet (upstream pressure) to open the valve to allow fluid to flow. When the upstream pressure falls below a certain level or when there is backpressure, the valve closes. Based on the globe valve design, the closing mechanism can be assisted by a spring. Backpressure pushes the disc against the orifice to seal it.
Types of globe check valve
Y-type globe check valve
This is a globe check valve that has the valve body designed to have a Y-shape. The spring and disc are installed at a certain angle. These valves can be repaired and cleaned without detaching them. This type of globe check valve needs larger space for installation.
Figure: Y-type globe check valve.
Cast-iron globe check valve
This is a globe check valve also known as a gray iron globe check valve. Globe check valve manufacturers make this valve using alloy made of iron, carbon, and silicone. This type of valve has good resistance to high temperatures as it can handle very high temperatures of around 1150o. These valves are also of high strength. There are two types of cast iron globe check valves based on the pressure class that is class 250 and class 125. The 125 class valve can operate at a pressure of 150 psi and 200 psi while the class 250 valve can work at higher pressures of 300 psi to 500 psi. Cast iron globe check valves are very strong and can work at intense vibrations without getting damaged. The main challenge with these valves is that they are not ductile which makes them crack at slight bending rendering them useless. However, cast iron globe check valves are not expensive relative to other valves.
Forged steel globe check valves
These are globe check valves produced using the forging method. The forging process is best known for making valves extremely strong and tough. Such strong globe check valves are necessary for applications such as steam power plants to control steam and water flow in one direction. Forged steel globe check valves are suitable for applications involving high-pressure and high temperatures. However, globe check valves made using this method are of smaller sizes. For large valves, they have to be made part by part, and later they are connected or welded together to make a complete forged steel globe check valve.
Bolted bonnet globe check valve
This is a globe check valve whereby the bonnet/cover plate is mounted on the valve body using bolts and nuts. This is one of the most common types of globe check valves. This type of valve uses a gasket to seal the joint between it and the body.
Screwed bonnet globe check valve
This is a globe check valve that uses screws to connect the bonnet/cover plate and the body valve. This type of valve uses a simple valve structure and is used in low-cost fluid flow applications.
Welded-bonnet globe check valve
This is a globe check valve whereby the cover plate and the body are connected through welding. This type of valve design makes it free from leakage even at very high pressure. As such, this valve is used in high temperature and high-pressure applications.
What should you consider when selecting/purchasing a globe check valve?
This refers to the fluid or solids that are expected to pass through the valve. This is a critical factor to consider because some fluids could be destructive to the valve or they could not be compatible. Some acidic fluids can cause corrosion on the valve’s internal components coming into contact with the valve. As such, before selecting/purchasing the globe check valve ensure it is compatible with the media.
This is the highest temperature that the valve will experience while in operation. The ability of the valve to work at different temperatures depends on its construction materials. Materials like cast iron can withstand a temperature of around 1150 oC while materials like stainless steel can withstand around 427 oC. Other materials like PTFE and elastomers can withstand lower temperatures relative to their metallic counterparts. So, when checking on the valve’s ability to work at high temperatures first check on the construction materials.
This is the highest pressure that the globe check valve can withstand. Just like maximum temperature, the highest pressure will depend on the construction materials since different materials have different strengths to withstand internal stresses resulting from internal fluid pressure. Materials like cast iron can withstand very high pressure of around 500 psi relative to stainless steel. If the valve body is not strong enough it may cause fluid leakage through the gaskets or joints. Also, very high pressure may damage the valve body and thus the whole valve.
Some globe check valves are meant to be used in applications where clogging is likely to occur often. As such, the valve design used should be easy to clean. Welded globe check valves will be hard to clean as they are completely sealed. Screwed and bolted bonnet valves will be easier to clean as the operator can remove the cover plate/bonnet and remove dirt in the valve.
Applications of globe check valves
- The globe check valves are used in petroleum industries.
- They are used in chemical processing industries.
- They are used in drug manufacturing processes in pharmaceutical processes.
- Globe check valves are used to control water or steam in boilers for power generation.
- They are used in the municipal or commercial water supply.
- Globe check valves are used in HVAC systems.
- They are used in irrigation systems.
Advantages of globe check valves
- Globe check valves help to prevent damage on compressor and pump as they prevent backflow.
- Their maintenance is cheap.
- Globe check valves are fast-acting.
- These valves prevent reverse flow.
- These valves have a wide range of temperatures.
- They have a wide range of operating pressure.
- Globe check valves are automatic.
Disadvantages of globe check valves
- Globe check valves allow flow in one direction only.
- These valves cannot help in throttling applications.
Troubleshooting globe check valves
Globe check valve vibrates or chatters
- This could be due to high velocity. When the valve produces a lot of noise could be due to low downstream pressure, high velocity, or expanded upstream. Ensure that the fluid flow velocity is as recommended by the globe check valve manufacturer.
No fluid passing through the valve
- Follow flow arrow direction on the body.
- Ensure that the downstream valve is open.
- Check if there is blockage downstream and remove if it is there.
Globe check valve slams
- Remove the globe check valve to inspect the coil spring.
- Try furnishing the spring if it is working on high head applications.
- Consult globe check valve technical expert if the problem persists.
Leakage in the globe check valve
- Bonnet is loose. Tighten the bonnet nuts/screws.
- Broken valve body. It could be due to external impact damage or high fluid pressure. Replace the valve body.
- Broken gasket. Replace the gasket.
- Worn-out seat rings. Replace the seat rings.
- Accumulated dirt on the sealing surface. Clean the dirt.
- Damaged seal surface. Replace seat or disc.
Globe check valve is a type of valve designed to prevent fluid from flowing backward. This helps to ensure that the valve is closed before the pump completely stops. This helps to prevent water hammers and surges associated with valve closure. Most of valves are automated. Most globe check valves employ a design with a spring and double guides which helps to ensure that as the pump starts the valve disc opens and that the valve closes before the fluid flows backward upon pump stoppage. Globe check valve manufacturers design the valve components and assemble them in a way that makes them easy to repair and do regular maintenance.
There are several types of globe check valves which include Y-shaped globe check valve, cast-iron globe check valves, forged steel globe check valves, bonnet welded globe check valves, bolted and screwed globe check valves. Each of these valves has certain features and advantages making it suitable for the specific application. This makes it necessary to consider certain factors when purchasing a globe check valve which are maximum temperature and pressure, media type, and maintenance requirements.
The design of a globe check valve employs the design of a globe valve and check valve. This valve uses a disc tasked to ensure the fluid does not flow backward. It only allows fluid flow in one direction that is forward direction from one pipeline to the next pipeline. Globe check valves are designed with two ports: inlet and outlet port. Globe check valves are used in different applications such as heating, ventilation, and air conditioning (HVAC), boiler systems, municipal water supply, irrigation, pharmaceutical industries among others. The advantages of the globe check valve are no reverse flow, cheap maintenance, protects pump and compressor, a wide range of operating temperature and pressure.