Continue reading for information on the importance, usage, and common problems of the back pressure valve in the oil and gas industry.
Valves are regulators of flow control devices that play crucial roles in the efficiency and safety of those working with piping systems. This is why they are used extensively in the oil and gas industry to regulate, handle, and control fluid flow rates such as liquefied petroleum, oxygen, and natural gas.
Valves can also regulate pressure in fluids, prevent backflow, direct the entire refining process of petroleum, and isolate and protect quality equipment. They are also available in a wide range of materials – i.e., metal or plastic – for different fluids (combustible, gas, toxic, etc.). One of the most efficient regulators is known as the back pressure valve.
Before highlighting what you need to know about the back pressure valve and its essential role, let’s find out what back pressure means.
What Is Back Pressure?
In simple terms, back pressure refers to the pressure held back, i.e., against the natural flow of gas or fluid. Back pressure is the upstream pressure maintained or held in multiple production vessels to provide the perfect conditions for processing and separation when used in oil and gas applications.
Examples of some of the vessels requiring back pressure include:
- Free water knockouts
- Separators
- Dehydration units
- Heater treaters
- Compressors
These vessels must maintain constant pressure to execute their unique functions appropriately. This allows gas or fluid to process efficiently through the vessel and beyond for disposal or additional processing.
If the back pressure is inconsistent, the processing and separation of gas, oil, and water would be much more challenging or practically impossible.
Engineers use a particular type of valve to hold pressure on these vessels. This valve is known as a back pressure valve.
Back pressure valves or regulators hold pressure on production vessels. A back pressure valve keeps track of upstream pressure and releases pressure as soon as production reaches – or exceeds – a pre-established set point. Technicians or engineers can readily adjust this set point by tightening or loosening the bolt on top of the valve or regulator.
How the Back Pressure Valve Works
The back pressure valve can be said to be integrated since the pilot, i.e., the key to closing and opening the valve, is directly connected to the valve, making it come out as a single piece.
As stated earlier, the back pressure valve checks upstream pressure. You must turn the adjustment bolt on top when adjusting the set point. A spring depresses the diaphragm assembly, which efficiently positions the pilot plug. This pilot plug then permits gas or fluid from upstream to push down on the diaphragm.
The flow through the back pressure valve is beneath the plunger and pushes up the plunger as the gas or fluid depresses the diaphragm. Since the diaphragm has a much larger surface than the plunger, the same pressure holds the valve in a close position.
At this point, constant back pressure is established, and the valve starts regulating the pressure.
If pressure somehow exceeds the set or pre-established point, the upstream pressure pushes up on the diaphragm assembly, effectively blocking off the pilot plug. Gas vents itself from the top of this diaphragm while the valve regulates the upstream pressure.
What Is the Primary Role of a Back Pressure Valve?
The primary role of a back pressure valve is to control the pressure of any fluid – i.e., in liquid form or gas form, or a mixture of both – within a pumping system.
This valve monitors the upstream pressure that forms into the piping system. Upstream pressure implies the direction of the pressure that runs against the current but toward the source.
Why Use a Back Pressure Valve?
When it comes to efficiency, a back pressure valve is much more efficient than a relief valve.
Almost all direct spring-operated safety regulators have high reseating pressure, which makes them unreliable and inconsistent.
Safety relief valves are primarily designed to protect equipment and downstream personnel if over-pressurization occurs. Therefore, when the pre-set pressure is overcome, the safety relief valve blows wide open instantly, exhausting all the pressure.
It must be capable of handling the entire system’s full flow to exhaust and rapidly protect downstream apparatus. Backpressure regulators are only designed for precise upstream pressure control and are not safety devices.
Steps for When the Back Pressure Valve Is Defective
If you detect that the back pressure valve is not functioning correctly, take the following steps:
1. Check for Dirty or Wet Gas
If you notice your valve keeps venting non-stop, it could be that you have dirty or wet gas in your pipeline.
You can fix this problem by removing the pilot housing and bonnet to access the pilot plug. Next, remove, clean, and dry the pilot plug; afterward, re-install the pilot plug.
Bear in mind that back pressure valves are primarily designed for gas only. Therefore, if this issue continues to be a hindrance, you may consider bringing in nothing but dry supply gas to your valve or regulator.
2. Remove the Stopper from the Breather Plug
What if your back pressure valve is stuck in the ‘ON’ position? It simply means that the red stopper could still be in the breather plug.
The stopper is usually in the breather plug to prevent oil from spilling out during transportation. However, you can easily remove it by hand so that the breather plug does not get air-locked, which may cause more problems in the long run.
3. Tighten – But Do Not Overdo It – The Seat Nut
Is your back pressure valve leaking through the downstream? Perhaps, someone overtightened the seat during maintenance or repair.
You can fix this problem by ensuring the nut is tightened correctly but not enough to bulge the seat. If the seat is already bulging, slacken the nut at least a quarter turn at a time until the seat is sitting flat.
4. Tighten Up the Pilot Plug Seat
If the valve refuses to open, it is possible that the pilot plug seat is a bit loose. You can address this by removing the bonnet and the pilot plug housing. This allows access to the pilot plug seat. Also, ensure the pilot plug seat is very snug.
Conclusion
Valves are regulators of flow control devices that play vital roles in piping systems. They are used extensively in the oil and gas industry for regulating, handling, and controlling fluid flow rates such as liquefied petroleum, oxygen, and natural gas.
One of the most vital regulators is the back pressure valve. Its importance in the oil and gas industry cannot be overstated.