شیرهای منیفولد on a manifold are typically described in terms of the number of valves in the manifold block, and also by the method of connection to transmitter(s). 2-way, 3-way, or 5-way？ Threaded, or flange？ Not sure which manifold valve you need？ This guide breaks down the types so you can choose with confidence.
1. Classification by Number of Valves
A manifold can be classified based on the number of valves it contains. This includes 2-way, 3-way, 5-way manifolds. As for each type of manifold, it will also be used with a particular type or types of instrument(s).
شیر منیفولد دو طرفه
Used for: Gauge pressure transmitters (static pressure measurement)
Valve functions:
- Block valve: to isolate the process from the instruments
- Bleed (vent) valve: The same as above but on the instrument side to release trapped pressure.
How it works？During normal process operation, the block valve is in the open position & the bleed valve in the closed position. To remove the transmitter from service, shut the block valve. Open the bleed valve to safely vent the instrument side of the transmitter. The reading on the transmitter would return to zero, allowing for removal of the transmitter.
The 2-way manifold is the simplest manifold and is used for isolation of gauge type pressure gauges and/or transmitters for occasional venting.
3-Way Manifold Valve
Used for: Differential pressure transmitters (flow, level and pressure drop measurement).
Valve functions:
- 2 Block Valves, one on the high side of the transmitter and one on the low side.
- One equalizing valve between the two block valves
How does it work? In normal operation, the transmitter is shown fully operational with both block valves open, and the equalizing valve closed.
To check the zero or remove the transmitter:
- Open the equalising or bell mouthed valve to equalise the pressure on both sides of the transmitter.
- Next close both block valves. The transmitter is now isolated from the process. The transmitter now reads zero.
- The transmitter can then be taken out of service and recalibrated as necessary.
The 3-way manifold valve is typically used for differential pressure transmitters used in flow measurement, level measurement and in the monitoring of pressure drop across filters.
5-Way Manifold Valve
Differential pressure transmitters that have to be calibrated or tested while the process is running.
Valve functions:
- Two block valves (high side and low side)
- One equalizing valve
- Two bleed/vent valves (one for each side)
How it works：The 5-way manifold does everything the 3-way manifold does, plus you have the additional feature of dedicated bleed valves. This allows you to:
- Vent each side of the transmitter separately.
- Allow for connection of a pressure calibration device to one side of the transmitter while the process is flowing on the other side of the transmitter.
- Perform 3-point or 5-point calibrations.
The two bleed/vent valves on a 5-way manifold are typically 1/4” NPT in size and are plugged at the end. A pressure generator or a calibration device can be connected at these ports as required.
In many industries the 5-way manifold is the most common type of manifold used in conjunction with differential pressure transmitters.
2. Classification by Connection Type
In addition to the number of valves a manifold can have, a manifold can also be classified based on the connection type to the differential pressure transmitter and the process connections.
Threaded Connection Manifolds
The manifold connects directly to the transmitter and process lines using threaded ports. This is the most common type.
Advantages：
- Simple and compact without extra flanges and gaskets.
- This is very easy to install, as it can be screwed into position.
- Lower cost than flanged manifolds.
Typical thread standards：
- NPT (National Pipe Thread) : most used in North America.
- BSPT or BSPP: They are commonly used in Europe, Asia and the Middle East and also in other parts of the world.
- Metric threads: for OEM equipment
Common port sizes：
- Process connections – 1/2” NPT or 1/4“ NPT
- Instrument connections are typically the same connection size as the transmitter for which you are purchasing a manifold (e.g. 1/2” NPT or M20×1.5).
- Bleed/vent ports – 1/4“ NPT
Threaded manifolds are generally suited for normal industrial applications at moderate pressures. While Flanged manifolds are recommended for high pressure or high temperature applications.
Flanged Connection Manifolds
Flanged Connection Manifolds are attached to a transmitter or pipe work using flanges which are bolted together with a gasket in the middle.
Advantages：
- Better for high-pressure and high-temperature service
- Stronger and more rigid than threaded connections
- Alignment and bolt up in the field is easier.
Disadvantages：
- Larger and heavier than threaded manifolds
- Higher cost
- More parts: flanges, bolts, nuts, gaskets
Typical flange standards：
- ASME B16.5: Typically used in North America. (Class 150, 300, 600, etc.)
- PN16, PN40, etc. according to EN 1092-1 in Europe.
Flange facing types：
- RF (Raised Face) : most common
- RTJ (Ring Type Joint) : typically used for high-pressure gas service applications.
Flanged manifolds are often used in:
- High-pressure steam systems
- High-temperature process lines
- Refineries and petrochemical plants
- Power generation
سوالات متداول
Q1. What material are manifold valves typically made of？
316 Stainless Steel is the typical material used for manifold valves as it can deal with the majority of media and environments. Occasionally Monel is used for seawater / sour gas applications and in extreme cases of corrosion with acids such as Hydrochloric Acid then Hastings C-276 is typically used.
Q2. Do I need to use thread sealant on a flanged manifold valve？
Flanged connections are sealed with a gasket between the faces of the flanges and as such, thread sealant should never be used on the threads of the bolts of a flange connection. The appropriate gasket material must be chosen for the process media and the process temperature.
Q3. What is the difference between a bleed valve and a vent valve？
A Bleed Valve is equal to a Vent Valve. These two names are used for the same type of valves in different industries. A Bleed Valve or Vent Valve is used to release trapped pressure from the instrument side.
Q4. How do I know if my transmitter needs a 2-way, 3-way, or 5-way manifold？
Count the pressure ports on your transmitter. One pressure port → gauge pressure transmitter → 2-way manifold. Two pressure ports (high and low) → differential pressure transmitter → 3-way or 5-way manifold. Need calibration ports？ → 5-way manifold.
نکات پایانی
A manifold valve is an extremely valuable piece of equipment to make connections to your instruments a lot easier. Having all the individual valves for all the instruments in one area greatly reduces the amount of potential leak points and makes maintenance a whole lot easier.
Most of the time, the choice comes down to your instrument type and connection requirements. Still not sure which manifold valve you need？ Contact us. We will help you pick the right one.
