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How to Choose the Correct Pressure Transmitter Manifold

How to Choose the Correct Pressure Transmitter Manifold

Pressure Transmitter Manifold valves consolidate multiple single valves into a single valve block. This method allows the user to use these multiple valves in a single block to perform multiple functions and tasks without removing the Differential Pressure Transmitter (DP) from its installed position. The single block minimizes the number of connections and potential leak points which makes for a more secure process connection.

A valve manifold is often used with a DP transmitter so that it can isolate and equalize pressure exerted on the transmitter whenever any process is taking place. This valve is manual, but it is useful for calibration and maintenance purposes. Find the details about DP Transmitter Application. And the Basics of DP Transmitter.

The 3 Valve Manifold

This device ascertains that the capsule does not exceed beyond its designated range and does not isolate the pressure transmitter manifold from the entire process. As the name implies, the 3-valve manifold actually comprises of three valves— a high pressure block valve, a lower pressure block valve and an equalizing valve.  The block valves work together to isolate the instruments. The equalizing valve, placed in between the low and high transmitter process connections, ensures equal pressure on both sides.

Study the image below depicting a 3 valve manifold shown within the dotted box. Often, an additional valve, referred to as the bleed valve, emits the trapped pressure into the atmosphere.

An image depicting the 3 valve manifold

Though the image above actually shows four valves, a standard 3 valve manifold only features two block valves and one equalizing valves as mentioned earlier; the block valve is often not included. Also, this image depicts the three valves as completely separate devices that have been connected with each other and to the transmitter through tubing. In essence, this kind of valve is fabricated as a monolithic device, featuring all three valves that are casted together into a single metallic block, which is attached to the pressure transmitter with O-ring seals, which often have a flanged face. Bleed valves are, however, connected separately. They are often threaded into the transmitter’s chambers.

Refer to the image given below, which shows another version of a 3 valve manifold, connected to a differential pressure transmitter. Note the upper port on the diaphragm capsule; a bleed valve can be inserted into the port externally.

3 valve pressure trainmaster manifold

Generally, the two block valves are open so that fluid pressure can reach the differential transmitter. However, the equalizing valve is closed tightly to prevent the fluid from passing between the low and high pressure sides. If the transmitter has to undergo maintenance, then it must be isolated first. This is done by shutting off the block vales and releasing the equalizing valve.

Valving a Differential Pressure Transmitter with 3 Valves Manifold into Service

A pressure transmitter manifold can be valved by performing the steps outlined below.

  1. Check and ensure that every valve is closed.
  2. Open the equalizing valves so as to ascertain that uniform pressure is applied on both sides of the transmitter manifold. This uniform pressure is formally referred to as zero differential pressure.
  3. Slowly turn on the higher pressure block valve. Inspect both sides of the transmitter and make sure there are no leakages.
  4. Now shut the equalizing valve such that pressure is locked on either side of the transmitter.
  5. Release the low pressure block valve to exert pressure on the low pressure side of the transmitter. Let the valve remain open until differential pressure has been established.
  6. The pressure transmitter manifold is now in operation.

In some instances, a bleed valve may be required, allowing trapped air to be released into the environment through the capsule housing.

Removing the Pressure Transmitter Manifold from Service

Perform the above steps in reverse order to remove the differential pressure transmitter from service. First shut the low pressure block valve. Now turn on the equalizing valve and then shut the high pressure valve. The pressure transmitter manifold is inoperable now. Ensure that valves are opened and closed in the exact sequence presented here so as to ascertain two main things—that a high differential pressure isn’t reached when isolating the pressure transmitter manifold and that the inside fluid pressure is minimum before the transmitter is vented.

Even after being removed from service, the pressure will still be exerted on the capsule, which should then be decreased through bleeding.  Thus, the last step is to open the bleed valve, which releases the trapped pressure inside the transmitter manifold.

The illustrations below show the final valve positions when a transmitter is in service and when it has been removed.

Operational and non operational states of a pressure transmitter manifold

5-Way Valve Manifold

In this type of pressure transmitter manifold, the bleed valve is built-in. Instead of venting out the pressure at the transmitter itself, this valve allows the trapped pressure to be passed through a tube and released at a remote location. If the 5-way valve manifold is under normal operation, then both the low pressure and the high pressure valves are opened, whereas the other two valves are closed. Please ensure that the equalizing valve is never opened if both blocking valves are released.  Such a state can damage the pressure transmitter and manifold or even expose personnel to hazards if the fluid is too hot or of radioactive nature. Hence, a 5 valve pressure transmitter manifold is often to prevent situations of this sort.

pressure transmitter manifold- DP-transmitter-Eastsensor Technology

The block diagram of a 5 valve pressure transmitter is shown below.

5 Valve Manifold

Valving a Differential Pressure Transmitter with 5 Valves Manifold into Service

  1. Ensure that all five valves are closed.
  2. Open the equalizing valve first so that zero differential pressure is applied to both ends of the transmitter.
  3. Now turn on the high pressure valve slowly, simultaneously checking for potential leakages on both sides of the transmitter.
  4. Turn off the equalizing valve so as to lock pressure.
  5. Turn on the low pressure valve; this should establish a differential pressure.
  6. The transmitter is now said to be in service.

Removing a 5 Valve Manifold Transmitter from Service

Close both the low and the high pressure valves. Release the equalizing valve and then the bleed valve to emit process pressure into the environment. The transmitter can now be said to be out of service. As in the case of a 3 valve manifold transmitter, the capsule will still be under pressure, which can be removed through bleeding.

The valve positions for both operational and nonoperational states are shown below.

5 Valve Manifold Transmitter under operation and removed from service

Please bear in mind never to release the equalizing valve if both block valves are opened simultaneously. If care is not exhibited, process fluid can reach the low and high pressure transmitter sides by passing through the equalizing valve. This can damage the transmitter and may even lead to human injuries. If the tubes connecting the process and manifold are filled up with a fluid like glycerin or steamed water, it will be lost. Full fluids may be used for directing process water away from the impulse tubes.

2-Way Valve Manifolds

The 2-way valve pressure transmitter manifold works best for gauge pressure applications and it has single block-and-bleed configurations. The low pressure port is released into the atmosphere, whereas the high pressure port is connected to the device.

2 Valve DP Transmitter

For removing the transmitter out of service, shut the blocking valve and release the bleed valve. This will vent out process pressure into the atmosphere.

The following image depicts eight pressure transmitters connected to each other. Seven of these feature a single capsule containing both the block and bleed valves, whereas the eighth transmitter (second transmitter from the left, located in the bottom row) comprises of a 5 valve manifold transmitter.  Study the figure carefully and note that a single bleed valve is attached to all the upper ports. Only the 5-valve transmitter is equipped with two bleed valves because it is the only device that can establish differential pressure. The rest of the transmitters are gauge pressure units, and hence, feature only a single bleed valve.

pressure transmitter manifold 5-valve-manifold

Operational Advice

When opening valves, back them off at least one quarter of a turn. This prevents seizing under normal operations and allows personnel to easily figure out the states of the valves.

A closed valve doesn’t turn easily because it is completely tightened in place, whereas an open valve can easily turn in either direction. However, closed valves shouldn’t be “backed off” because they must be secured tightly into place to remain in the shut-off position.

Pressure Transmitter Flange Table

Pressure Transmitter Flange Table

Pressure Transmitter Flange is commonly used to connect pressure transmitter into pipework making it easier for removal and maintenance. There are many common Flange Standards and Pressure Transmitter Flange within the same standard can either be flat (commonly cast iron, ductile iron) or raised face (commonly cast steel and stainless steel).

Click to Find Out details of Diaphragm Seals for EST4300 Smart Pressure/Differential Transmitter

Below is a reference table for critical flange dimensions to help identify what standard you have.

Pressure Transmitter Flange Table-eastsensor2

ANSI B16.5ISO 7005 (DIN)DiameterBolt Circle DiameterNumber of BoltsBolt SizeDiameter of Bolt Hole
ANSI 150PN203 1/2″ / 89mm2 3/8″ / 60mm41/2″5/8″ / 16mm
ANSI 600PN1003 3/4″ / 95mm2 5/8″ / 67mm41/2″5/8″ / 16mm
ANSI 900PN1504 3/4″ / 121mm3 1/4″ / 83mm43/4″7/8″ / 22mm
ANSI 1500PN2504 3/4″ / 121mm3 1/4″ / 83mm43/4″7/8″ / 22mm
ANSI 2500PN4205 1/4″ / 1333 1/2″ / 89mm43/4″7/8″ / 22mm
ANSI B16.5ISO 7005 (DIN)DiameterBolt Circle DiameterNumber of BoltsBolt SizeDiameter of Bolt Hole
ANSI 150PN203 7/8″ / 98mm2 3/4″ / 70mm41/2″5/8″ / 16mm
ANSI 300PN504 5/8″ / 117mm3 1/4″ / 83mm45/8″3/4″ / 19mm
ANSI 600PN1004 5/8″ / 117mm3 1/4″ / 83mm45/8″3/4″ / 19mm
ANSI 900PN1505 1/8″ / 130mm3 1/2″ / 89mm43/4″7/8″ / 22mm
ANSI 1500PN2505 1/8″ / 130mm3 1/2″ / 89mm43/4″7/8″ / 22mm
ANSI B16.5ISO 7005 (DIN)DiameterBolt Circle DiameterNumber of BoltsBolt SizeDiameter of Bolt Hole
ANSI 150PN204 1/4″ / 108mm3 1/8″ / 79mm41/2″5/8″ / 16mm
ANSI 300PN504 7/8″ / 124mm3 1/2″ / 89mm45/8″3/4″ / 19mm
ANSI 600PN1004 7/8″ / 124mm3 1/2″ / 89mm45/8″3/4″ / 19mm
ANSI 900PN1505 7/8″ / 149mm4″ / 102mm47/8″1″ / 25mm
ANSI 1500PN2505 7/8″ / 149mm4″ / 102mm47/8″1″ / 25mm

ANSI B16.5ISO 7005 (DIN)DiameterBolt Circle DiameterNumber of BoltsBolt SizeDiameter of Bolt Hole
ANSI 150PN204 5/8″ / 117mm3 1/2″ / 89mm41/2″5/8″ / 16mm
ANSI 300PN505 1/4″ / 133mm3 7/8″ / 98mm45/8″3/4″ / 19mm
ANSI 600PN1005 1/4″ / 133mm3 7/8″ / 98mm45/8″3/4″ / 19mm
ANSI 900PN1506 1/4″ / 159mm4 3/8″ / 111mm47/8″1″ / 25mm
ANSI 1500PN2506 1/4″ / 159mm4 3/8″ / 111mm47/8″1″ / 25mm
ANSI B16.5ISO 7005 (DIN)DiameterBolt Circle DiameterNumber of BoltsBolt SizeDiameter of Bolt Hole
ANSI 150PN205″ / 127mm3 7/8″ / 98mm41/2″5/8″ / 16mm
ANSI 300PN506 1/8″ / 156mm4 1/2″ / 114mm43/4″7/8″ / 22mm
ANSI 600PN1006 1/8″ / 156mm4 1/2″ / 114mm43/4″7/8″ / 22mm
ANSI 900PN1507″ / 178mm4 7/8″ / 124mm41″1 1/8″ / 29mm
ANSI 1500PN2507″ / 178mm4 7/8″ / 124mm41″1 1/8″ / 29mm
ANSI B16.5ISO 7005 (DIN)DiameterBolt Circle DiameterNumber of BoltsBolt SizeDiameter of Bolt Hole
ANSI 150PN206″ / 152mm4 3/4″ / 121mm45/8″3/4″ / 19mm
ANSI 300PN506 1/2″ / 165mm5″ / 127mm85/8″3/4″ / 19mm
ANSI 600PN1006 1/2″ / 165mm5″ / 127mm85/8″3/4″ / 19mm
ANSI 900PN1508 1/2″ / 216mm6 1/2″ / 165mm87/8″1″ / 25mm
ANSI 1500PN2508 1/2″ / 216mm6 1/2″ / 165mm87/8″1″ / 25mm
ANSI B16.5ISO 7005 (DIN)DiameterBolt Circle DiameterNumber of BoltsBolt SizeDiameter of Bolt Hole
ANSI 150PN207″ / 178mm5 1/2″ / 140mm45/8″3/4″ / 19mm
ANSI 300PN507 1/2″ / 191mm5 7/8″ / 149mm83/4″7/8″ / 22mm
ANSI 600PN1007 1/2″ / 191mm5 7/8″ / 149mm83/4″7/8″ / 22mm
ANSI 900PN1509 5/8″ / 244mm7 1/2″ / 191mm81″1 1/8″ / 29mm
ANSI 1500PN2509 5/8″ / 244mm7 1/2″ / 191mm81″1 1/8″ / 29mm
ANSI B16.5ISO 7005 (DIN)DiameterBolt Circle DiameterNumber of BoltsBolt SizeDiameter of Bolt Hole
ANSI 150PN207 1/2″ / 191mm6″ / 152mm45/8″3/4″ / 19mm
ANSI 300PN508 1/4″ / 210mm6 5/8″ / 168mm83/4″7/8″ / 22mm
ANSI 600PN1008 1/4″ / 210mm6 5/8″ / 168mm83/4″7/8″ / 22mm
ANSI 900PN1509 1/2″ / 241mm7 1/2″ / 191mm87/8″1″ / 25mm
ANSI 1500PN25010 1/2″ / 267mm8″ / 203mm81 1/8″1 1/4″ / 32mm
ANSI B16.5ISO 7005 (DIN)DiameterBolt Circle DiameterNumber of BoltsBolt SizeDiameter of Bolt Hole
ANSI 150PN209″ / 229mm7 1/2″ / 191mm85/8″3/4″ / 19mm
ANSI 300PN5010″ / 254mm7 7/8″ / 200mm83/4″7/8″ / 22mm
ANSI 600PN10010 3/4″ / 273mm8 1/2″ / 216mm87/8″1″ / 25mm
ANSI 900PN15011 1/2″ / 292mm9 1/4″ / 235mm81 1/8″1 1/4″ / 32mm
ANSI 1500PN250112 1/4″ / 311mm9 1/2″ / 241mm81 1/4″1 3/8″ / 35mm
ANSI B16.5ISO 7005 (DIN)DiameterBolt Circle DiameterNumber of BoltsBolt SizeDiameter of Bolt Hole
ANSI 150PN2010″ / 254mm8 1/2″ / 216mm83/4″7/8″ / 22mm
ANSI 300PN5011″ / 279mm9 1/4″ / 235mm83/4″7/8″ / 22mm
ANSI 600PN10013″ / 330mm10 1/2″ / 267mm81″1 1/8″ / 29mm
ANSI 900PN15013 3/4″ / 349mm11″ / 279mm81 1/4″1 3/8″ / 35mm
ANSI 1500PN25014 3/4″ / 375mm11 1/2″ / 292mm81 1/2″1 5/8″ / 41mm
ANSI B16.5ISO 7005 (DIN)DiameterBolt Circle DiameterNumber of BoltsBolt SizeDiameter of Bolt Hole
ANSI 150PN2011″ / 279mm9 1/2″ / 241mm83/4″7/8″ / 22mm
ANSI 300PN5012 1/2″ / 318mm10 5/8″ / 270mm123/4″7/8″ / 22mm
ANSI 600PN10014″ / 356mm11 1/2″ / 292mm121″1 1/8″ / 29mm
ANSI 900PN15015″ / 381mm12 1/2″ / 318mm121 1/8″1 1/4″ / 32mm
ANSI 1500PN25015 1/2″ / 394mm12 1/2″ / 318mm121 3/8″1 1/2″ / 38mm
ANSI B16.5ISO 7005 (DIN)DiameterBolt Circle DiameterNumber of BoltsBolt SizeDiameter of Bolt Hole
ANSI 150PN2013 1/2″ / 343mm11 3/4″ / 298mm83/4″7/8″ / 22mm
ANSI 300PN5015″ / 381mm13″ / 330mm127/8″1″ / 25mm
ANSI 600PN10016 1/2″ / 419mm13 3/4″ / 349mm121 1/8″1 1/4″ / 32mm
ANSI 900PN15018 1/2″ / 470mm15 1/2″ / 394mm121 3/8″1 1/2″ / 38mm
ANSI 1500PN25019″ / 483mm15 1/2″ / 394mm121 5/8″1 3/4″ / 44mm
ANSI B16.5ISO 7005 (DIN)DiameterBolt Circle DiameterNumber of BoltsBolt SizeDiameter of Bolt Hole
ANSI 150PN2016″ / 406mm14 1/4″ / 362mm127/8″1″ / 25mm
ANSI 300PN5017 1/2″ / 445mm15 1/4″ / 387mm161″1 1/8″ / 29mm
ANSI 600PN10020″ / 508mm17″ / 432mm161 1/4″1 3/8″ / 35mm
ANSI 900PN15021 1/2″ / 546mm18 1/2″ / 470mm161 3/8″1 1/2″ / 38mm
ANSI 1500PN25023″ / 584mm19″ / 483mm121 7/8″2″ / 51mm
ANSI B16.5ISO 7005 (DIN)DiameterBolt Circle DiameterNumber of BoltsBolt SizeDiameter of Bolt Hole
ANSI 150PN2019″ / 483mm17″ / 432mm127/8″1″ / 25mm
ANSI 300PN5020 1/2″ / 521mm17 3/4″ / 451mm161 1/8″1 1/4″ / 32mm
ANSI 600PN10022″ / 559mm19 1/4″ / 489mm201 1/4″1 3/8″ / 35mm
ANSI 900PN15024″ / 610mm21″ / 533mm201 3/8″1 1/2″ / 38mm
ANSI 1500PN25026 1/2″ / 673mm22 1/2″ / 572mm162″2 1/8″ / 54mm
ANSI B16.5ISO 7005 (DIN)DiameterBolt Circle DiameterNumber of BoltsBolt SizeDiameter of Bolt Hole
ANSI 150PN2021″ / 533mm18 3/4″ / 476mm121″1 1/8″ / 29mm
ANSI 300PN5023″ / 584mm20 1/4″ / 514mm201 1/8″1 1/4″ / 32mm
ANSI 600PN10023 3/4″ / 603mm20 3/4″ / 527mm201 3/8″1 1/2″ / 38mm
ANSI 900PN15025 1/4″ / 641mm22″ / 559mm201 1/2″1 5/8″ / 41mm
ANSI 1500PN25029 1/2″ / 749mm25″ / 635mm162 1/4″2 3/8″ / 60mm
ANSI B16.5ISO 7005 (DIN)DiameterBolt Circle DiameterNumber of BoltsBolt SizeDiameter of Bolt Hole
ANSI 150PN2023 1/2″ / 597mm21 1/4″ / 540mm161″1 1/8″ / 29mm
ANSI 300PN5025 1/2″ / 648mm22 1/2″ / 572mm201 1/4″1 3/8″ / 35mm
ANSI 600PN10027 1/2″ / 699mm23 3/4″ / 603mm201 1/2″1 5/8″ / 41mm
ANSI 900PN15027 1/2″ / 699mm23 3/4″ / 603mm201 1/2″1 5/8″ / 41mm
ANSI 1500PN25032 1/2″ / 826mm27 3/4″ / 705mm162 1/2″2 5/8″ / 67mm
ANSI B16.5ISO 7005 (DIN)DiameterBolt Circle DiameterNumber of BoltsBolt SizeDiameter of Bolt Hole
ANSI 150PN2025″ / 635mm22 3/4″ / 578mm161 1/8″1 1/4″ / 32mm
ANSI 300PN5028″ / 711mm24 3/4″ / 629mm241 1/4″1 3/8″ / 35mm
ANSI 600PN10029 1/4″ / 743mm25 3/4″ / 654mm201 5/8″1 3/4″ / 44mm
ANSI 900PN15031″ / 787mm27″ / 686mm201 7/8″2″ / 51mm
ANSI 1500PN25036″ / 914mm30 1/2″ / 775mm162 3/4″2 7/8″ / 73mm
ANSI B16.5ISO 7005 (DIN)DiameterBolt Circle DiameterNumber of BoltsBolt SizeDiameter of Bolt Hole
ANSI 150PN2027 1/2″ / 699mm25″ / 635mm201 1/8″1 1/4″ / 32mm
ANSI 300PN5030 1/2″ / 775mm27″ / 686mm241 1/4″1 3/8″ / 35mm
ANSI 600PN10032″ / 813mm28 1/2″ / 724mm241 5/8″1 3/4″ / 44mm
ANSI 900PN15033 1/4″ / 845mm29 1/2″ / 749mm202″2 1/8″ / 54mm
ANSI 1500PN25038 3/4″ / 984mm32 3/4″ / 832mm163″3 1/8″ / 79mm
ANSI B16.5ISO 7005 (DIN)DiameterBolt Circle DiameterNumber of BoltsBolt SizeDiameter of Bolt Hole
ANSI 150PN2032″ / 813mm29 1/2″ / 749mm201 1/4″1 3/8″ / 35mm
ANSI 300PN5036″ / 914mm32″ / 813mm241 1/2″1 5/8″ / 41mm
ANSI 600PN10037″ / 940mm33″ / 838mm241 7/8″2″ / 51mm
ANSI 900PN15041″ / 1041mm34″ / 864mm202 1/2″2 5/8″ / 67mm
ANSI 1500PN25046″ / 1168mm39″ / 991mm163 1/2″3 5/8″ / 92mm
All you need to know about Transmitter Flange Size and Class

All you need to know about Transmitter Flange Size and Class

A Transmitter Flange is an external or internal ridge, or rim (lip), items connected with flanges can be assembled and disassembled easily.

There are many different Transmitter Flange standards to be found worldwide. To allow easy functionality and interchangeability, these are designed to have standardized dimensions. Common world standards include

  • PN/DIN (European)
  • BS10 (British/Australian)
  • JIS/KS (Japanese/Korean)
Flanges Standards Versions
DIN Flanges EN FlangesASME FlangesJIS Flanges
German National Standards InstituteEuropean StandardsAmerica Society of Mechanical EngineersJapanese Industry Standard
DIN 2527DIN EN 1092-1:2002-06 and 2007ANSI B 16.5:2009B2220:2004

In the USA, ANSI stopped publishing B16.5 in 1996, and the standard is ASME B16.5

In this article, we mainly talk about ASME and EN-DIN Standard

ASME Standards (U.S.)

ASME (American Society of Mechanical Engineers, of which Australian Pipeline Valve is a member company) is a group of standards, which are in turn covered within the American Standards Institute (ANSI), hence their flanges can be referred to as ANSI or ASME class.


  • ASME5 (the latest version)
  • ASME B16.47
  • MSS SP-44.

They are typically made from forged materials and have machined surfaces.


  • ASME B16.5 refers to nominal pipe sizes(NPS) from ½” to 24″.
  • ASME B16.47 covers NPSs from 26″ to 60″.


  • ASME B16.5 further delineates flanges into seven primary ratings/class: 150 LBS, 300 LBS, 400 LBS, 600 LBS, 900 LBS, 1500 LBS and 2500 LBS.
  • ASME B16.47 delineates its flanges into pressure classes 75 LBS, 150 LBS, 300 LBS, 400 LBS, 600 LBS, and 900 LBS.
  • A Class 300 flange is rated to a higher pressure than a Class 150 flanges, because a Class 300 flange is constructed with more metal and therefore can withstand more pressure. However there are a number of factors that can impact pressure capability of a flange, obviously temperature is one of them.
  • The Pressure Class for flange is often expressed in ‘pounds’. Different names are used to indicate a Pressure Class. For example: 150Lb or 150Lbs or 150#, all mean the same.


Materials for flanges are usually under ASME designation including types as below

  • SA-105 : Specification for Carbon Steel Forgings for Piping Applications
  • SA-266: Specification for Carbon Steel Forgings for Pressure Vessel Components
  • SA-182: Specification for Forged or Rolled Alloy-Steel Pipe Flanges, Forged Fittings, and Valves and Parts for High-Temperature Service.

In addition, there are many “industry standard” flanges that in some circumstance may be used on ASME work.

The below two tables are examples of two material groups according to ASTM

ASTM Group 2-1.1 Materials
Nominal DesignationForgingsCastings
C-SiA105 (1)A216 Gr.WCB (1)
C-Mn-SiA350 Gr.LF2 (1)-
3 1/2NiA350 Gr.LF3-
C-Mn-Si-VA350 Gr.LF6 Cl 1 (3)-
(1) Upon prolonged exposure to temperatures above 425ºC, the carbide phase of steel may be converted to graphite. Permissible but not recommended for prolonged use above 425ºC.
(2) Do not use over 260ºC.
ASTM Group 2-1.1 Materials
Nominal DesignationForgingsCastings
16Cr-12Ni-2MoA182 Gr.F316LA351 CF3M
18Cr-13Ni-3MoA182 Gr.F317L-
18Cr-8NiA182 Gr.F304L (1)A351 CF3
(1) Do not use over 425ºC.

Click to Download Corrosion-resistance Reference Sheet of Diaphragms when you choose certain material, the compatibility matter the most.


The above seven primary classes do not correspond to maximum pressures in psi. Instead, the maximum pressure depends on both the material of the flange and the temperature.

For example, the maximum pressure for a Class 150 flange is 285 psi, and for a Class 300 Flange it is 740 psi (both are for ASTM A105 Carbon Steel and temperatures below 100F).

The below 2 tables show ANSI/ASME class 150 to 2500LB pressure/temperature ratings for group 2-1.1 and 2-2.3

Pressure-Temperature Ratings for ASTM Group 2-1.1 Materials
Working pressure by Classes, BAR
-29 to 3819.651.168.1102.1153.2255.3425.5
Pressure-Temperature Ratings for ASTM Group 2-2.3 Materials
Working pressure by Classes, BAR
-29 to 3815.941.455.282.7124.1206.8344.7

European Dimensions EN / DIN/ISO7005


DIN is a type of Standards

When it comes to German flange manufacturing standards, on the other hand, the governing body is the German Institute of Standardization or Deutsches Institut für Normung (DIN).


DN = Diameter Nominal

The term Diameter Nominal refers to the internal diameter of a pipe. The nominal diameter DN is indicated with reference to the corresponding DIN standard. The metric sizes are stated as ‘DN’ (Nominal Diameter) in mm, equivalent imperial sizing is rounded to the nearest multiple of 25mm (for 2” and over) as below.

1/2″DN152 1/2″DN6512″DN30024″DN600
1 1/4″DN325″DN12516″DN40032″DN800
1 1/2″DN408″DN20018″DN45036″DN900

EST4300 Smart Remote Diaphragm Seal PT/DPT use different kind of 1199 Remote Diaphragm Seal Systems (Click to Download Datasheet), the pressure rating have been exactly classified as per above standard.


PN stands for Pressure Nominal and prefixes the pressure rating. PN is the rating designator follower by a designation number indicating the approximate pressure rating in bars, e.g. a PN16 flange is designed to operate up to 16bar.

  • Typical ratings include PN6, PN10, PN16, PN25, PN40, PN64, and PN100.
  • The American ANSI standard refers instead to a pressure / temperature rating termed ‘Class’.
  • PN ratings do not provide a proportional relationship between different PN numbers, whereas ‘Class’ numbers do.
  • Class Ratings based on ASME B16.5 & Corresponding PN Rating:
Flange Class15030040060090015002500
Flange Pressure Nominal, PN205068100150250420

You can also Click Here to check another post in regards of the details of Transmitter Flange diameter, bolts number, bolts circle diameter etc.


  • British Metric Standard BS4504 is now obsolete and replaced by EN1092-1 edition 09-2008 for steel flanges which also incorporates DIN Standard.
  • Flange drillings in EN1092-1 are generally the same as BS4504 and DIN2501 but EN1092-1 covers a wider range.
  • Most countries in Europe mainly install flanges according to standard DIN EN 1092-1 (forged Stainless or Steel Flanges).
  • ISO 7005 (which AS 4331 is reproduction of) also includes European DIN 2501-1 and BS4504.
  • These flanges are the same as EN1092 but EN1092 also includes higher rated DIN based flanges.
  • Although the standards say they are identical, there are some very minor flange thickness differences between ISO7005 (AS4331) and EN1092.


Design According to EN TypeAccording to DIN
Weld Neck Flange Type 11DIN 2627-DIN2638
Blind Flange Type 05DIN 2527
Thread Flange Type 12DIN 2558,DIN2565-DIN2569
Flat Flange Type 01DIN 2573,DIN2576
Lapped Flange Type 02&Type 04DIN2641,DIN2642,DIN2655


  • EN 1092-1 is for stainless or steel flanges
  • EN 1092-2 is for iron flanges
  • EN 1092-3 is for alloy flanges
  • EN 1092-4 is for aluminum alloy flanges
Four Types of Thread Process Connections Your Need Know – Part 2/2

Four Types of Thread Process Connections Your Need Know – Part 2/2

Comparison Sheet for Thread Process Connections:  M – BSPP – BSPT – NPT – UNC – UNF

UNC (2A)
Metric: Standard/FineInch: BSPP (G)BSPT (R)NPTUNC/UNF
Flank angle60°55°55°60°60°
Thread angle1°47’1°47’
Seal locationO-ring/ Gasket/ConeO-ring/ Gasket/ConeOn threadsOn threadsO-ring/ Gasket/Cone
Major Diameter (mm):
Minor Diameter (mm):
TPI (Treads per inch):

How to Choose Thread Process Connections

There are no criteria to judge which Thread Process Connections mentioned above is better. Actually, each of them appears at a proper time with a proper reason. When it comes to choose a process connection, what really matters is the pipe fitting your pressure transducer is to be used.  It is true that different country has its own standards and it is also a fact that any thread standard is available worldwide.

If you need help in finding what your need. Contact Us! We are always ready to give your support in choosing pressure sensor Thread Process Connections.

Thread Permissible maximum pressure
Cu-alloyStainless steelMonel®
BSP ⅛ (G⅛)4006,00040060004006,000
BSP ¼ (G¼)6008,6001,00015,0001,00015,000
BSP ⅜(G⅜)6008,6001,00015,0001,00015,000
BSP ½ (G½)1,00015,0002,50036,0002,50036,000
M10 x 14006,0004006,0004006,000
M12 x 1.54006,0004006,0004006,000
M20 x 1.51,00015,0002,50036,0002,50036,000
⅛ NPT, R ⅛4006,0004006,0004006,000
¼ NPT, R ¼6008,6001,00015,0001,00015,000
⅜ NPT, R ⅜6008,6001,00015,0001,00015,000
½ NPT, R ½1,00015,0001,60023,0001,60023,000
7/16-20 UNF4006,00080012,00080012,000
The specified values for the maximum pressure are rounded values and are assigned to the nearest standard scale range.
Thread Glossary
ASMEThe American Society of Mechanical Engineers (ASME)
BSPPBritish Standard Pipe Parallel per ISO 228/1
BSPTBritish Standard Pipe Tapered per EN 10226-1. See ISO 7/1.
DINDeutsche Institut für Normung e.V.
ISO 228/1International Standards Organization Specification 228/1, straight threads, reference specification: BSPP, DIN 259, JIS B0202.
JISJapanese Industrial Standard
MetricISO Metric thread is a globally standardized thread
NPTNational Pipe Tapered.
SAESociety of Automotive Engineers
UNUnified Constant-Pitch Thread Series
UNC/UNRCUnified Coarse Thread Series
UNEF/UNREFUnified Extra-Fine Thread Series
UNF/UNRFUnified Fine Thread Series
UNRMale Screw Thread only
UNS/UNRSSelected special combinations of diameter, pitch, and length of engagement
PitchFor the purposes of this guide, pitch refers to threads per inch, instead of the distance between the threads, for fractional screw threads and pipe threads. For all metric screw threads, pitch refers to the distance between adjacent threads.

For the previous knowledge, please refer to Part 1.

Four Types of Thread Process Connections Your Need Know – Part 1/2

Four Types of Thread Process Connections Your Need Know – Part 1/2

Back in the 19th century, screw Threads Process Connections come in a great variety and go incompatible with each other. Nowadays, thanks to the efforts made by people committing to standardizing process connections threads, choices are nailed down to a few when choosing a pressure transmitter. In what follows, three types of thread are introduced, namely, BSP, NPT, and UNF.

British Standard Pipe

BSP, British Standard Pipe, was created by Joseph Whitworth in the middle of 19th century and is now widely accepted from Europe to Asia, in particular in the UK. BSP is a type of parallel thread and the pressure tight seal is enabled with a sealing washer, which is made of different materials depending on the pressure and the medium being used. The most common sizes are ¼ or ½ inch BSP.

1/2"BSP MALE1/2"G EN837 DIN162881/4"G EN837 DIN162881/4"G DIN3852
1_2'BSP MALEEN83701 G_2B G1_2A DIN 16288 FORM B1_4'BSP EN837 DIN162881_4'G DIN3852-2
Thread size (inch)Major Diameter (mm)Minor Diameter (mm)TPIMale Thread size
Female Thread size
Major Diameter (mm)Minor Female
Diameter (mm)
G 1/16”7,7236,56128R 1/16”Rp 1/16”7,7236,49028
G 1/8”9,7288,56628R 1/8”Rp 1/8”9,7288,49528
G 1/4”13,15711,44519R 1/4”Rp 1/4”13,15711,34119
G 3/8”16,66214,95019R 3/8”Rp 3/8”16,66214,84619
G 1/2”20,95518,63114R 1/2”Rp 1/2”20,95518,48914
G 3/4”26,44124,11714R 3/4”Rp 3/4”26,44123,97514
G 1”33,24930,29111R 1”Rp 1”33,24930,11111
G 2”59,61456,65611R 2”Rp 2”59,61456,47611

National Pipe Taper

In the USA, NPT (National Pipe Tapered) is the most popular process connection, especially in businesses of oil and petroleum. Compared with BSP, NPT is easier to cut and user-friendly, and is considered a booster to American Industrial Revolution. Being a kind of screw thread system, NPT is tapered thread with the pressure tight seal being made on the thread itself. The most common sizes are 1/4, or 1/2 inch NPT.

Thread sizeMajor Diameter (mm)TPI
1/16” – 27 NPT7,93827
1/8” – 27 NPT10,28727
1/4” – 18 NPT13,71618
3/8” – 18 NPT17,14518
1/2” – 14 NPT21,33614
3/4” – 14 NPT26,67014
1” – 11 ½ NPT33,40111,5
2” – 11 ½ NPT60,32511,5

Unified Thread Standard

William Sellers also developed what became the Unified Thread Standard. Straight thread Process Connections known as SAE are now called UNF (Unified National Fine) under the Unified Thread Standard.

A common variation of this Process Connections is the M/F-250, or the autoclave fitting. This fitting has a cone at the end of it for pressure ranges above 10,000 psi. It is also commonly referred to as a Sno Trik® fitting as well – though that is a brand name.

The most common types of UN (Unified National) thread are:

  1. UNC – Unified National Coarse Thread, comparable with the ISO metric thread.
  2. UNF – Unified National Fine Thread.

*Compared to standard threads (coarse thread), a fine thread has a smaller pitch.

Unified threads come in three different classes:

  1. 1A (external) & 1B (internal): for applications where a liberal tolerance is required to permit easy assembly even with slightly nicked threads.
  2. 2A (external) & 2B (internal): most commonly used class for general applications
  3. 3A (external) & 3B (internal): for applications where closeness of fit and/or accuracy of thread elements are important.
UNC (2A)UNF (2A)
Nominal DiameterMajor Diameter (mm)Minor Diameter (mm)TPINominal DiameterMajor Diameter (mm)Minor Diameter (mm)TPI
1/4” x 20 UNC6,3224,978201/4” x 28 UNF6,3255,36028
5/16” x 18 UNC7,9076,401185/16” x 24 UNF7,9106,78224
3/8” x 16 UNC9,4917,798163/8” x 24 UNF9,4978,38224
7/16” x 14 UNC11,0769,144147/16” x 20 UNF11,0799,72820
1/2” x 13 UNC12,66110,592131/2” x 20 UNF12,66711,32820
5/8” x 11 UNC15,83413,386115/8” x 18 UNF15,83914,35118
3/4” x 10 UNC19,00416,307103/4” x 16 UNF19,01217,32316
7/8” x 9 UNC22,17619,17797/8” x 14 UNF22,18420,26914
1” x 8 UNC25,34921,97181” x 12 UNF25,35423,11412
2” x 4,5 UNC50,72644,6794.5

ISO Metric Screw Thread

The ISO metric screw threads are the world-wide most commonly used type of general-purpose screw thread. They were one of the first international standards agreed when the International Organization for Standardization was set up in 1947.

The “M” designation for metric screws indicates the nominal outer diameter of the screw, in millimeters (e.g., an M6 screw has a nominal outer diameter of 6 millimeters). (Source from Wikipedia)

ISO 262 selected sizes for screws, bolts and nuts
Nominal diameter D (mm)Pitch P (mm)Nominal diameter D (mm)Pitch P (mm)
1st choice2nd choiceCoarseFine1st choice2nd choiceCoarseFine
10.250.21621.5 or 1.5 or 1.5
1.60.350.2222.52 or 1.5
81.251 or 0.755254
101.51.25 or 1565.54
121.751.5 or 1.25605.54

Please refer to Part 2 for further reading.

The Ultimate Knowledge about Thread for Process Connection you need know

The Ultimate Knowledge about Thread for Process Connection you need know

What does the Thread Gender mean?

When we do process connection, every matched pair of threads, external and internal, can be described as male and female. For example, a screw has male thread, while the matching hole has female thread.

Process Connection THREAD GENDER

What is the HANDEDNESS of Thread? 

The helix of a thread can twist in two possible directions. Most threads are oriented so that the threaded item when seen from a point of view on the axis through the center of the helix moves away from the viewer when it is turned in a clockwise direction, and moves towards the viewer when it is turned counter clockwise. By common convention, right-handedness is the default handedness for screw threads. Therefore, most threaded parts and fasteners have right handed threads.

Process Connection HANDEDNESS

What does thread PITCH/TPI and DIAMETER mean? 

  • The pitch is the distance from the crest of one thread to the next in mm. TPI (Threads per inch) is used by inch thread.
  • The major diameter is determined by the thread tips.
  • The minor diameter is determined by the groove of the thread.
  • The pitch diameter is the distance of two opposite flanks or the distance of the centerline of the profile.

Process Connection Pitch and TPI

What does thread ANGLE and CREST/ROOT mean? 

The flank angle is the angle between the flank of a screw thread and the perpendicular to the axis of the screw. Tapered threads have a taper angle. This is the angle between the taper and the centre axis of the pipe.

The outer-most part of the thread is called crest, the inner-most part of the thread is called root.

Process Connection ANGLE AND CREST ROOT

How to determine if the thread is tapered or straight (parallel)?

Use a caliper to measure the nominal male or female thread crest-to-crest diameter on the first, fourth, and last full threads.  If the diameters increase for a male end or decrease for a female end, the thread is tapered. If all the diameters are the same, the thread is straight (parallel).

Process Connection P T

What is the difference among BSP-P, BSP-G and BSP-T?

There are mainly two ways of identifying a British Standard Pipe parallel (BSP-P) thread for Process Connection, either with the thread size suffixed by “BSP-P” or prefixed with “G”.  Often the 2nd P is left off because BSPT tapered threads are less common and BSP is assumed to be parallel unless otherwise specified.

Does 1/2 NPT male thread fit 1/2 BSP port?

No, BSP or G parallel threads are not compatible with NPT tapered threads, ideally you should use an adapter between the two threads to be sure of a reliable seal between the two different types of thread.

 Is there any difference between 1/4G and 1/4NPT female threaded connectors?

Yes there is a difference and they are not compatible with each other: 1/4G normally written as G1/4 or 1/4BSP(P) is a parallel thread typically used in Europe.1/4 NPT is a tapered thread typically used in USA.

What is 0.25-18 NPT male?

It is a type of tapered thread process connection, normally written as 1/4inch – 18 NPT male, the 1/4 inch (0.25″) refers to the nominal NPT pipe size and the 18 refers to the number of threads per inch.

How does a 1/4-19BSP P differ from a 1/4 BSP P thread?

They are both the same, since the ’19’ refers to 19 threads per inch (tpi) which is the standard thread pitch for a 1/4 BSP P thread.

What does NPTF stand for: Female, Fine, or Fuel?

NPTF stands for National Pipe Taper Fuel. This could be male or female. NPTF is designed to provide a more leak free seal without the use of teflon tape or other sealant compound. A common mistake is to assume that NPTF stands for NPT female or NPT fine. NPT fine does not exist.

Is it the same way to seal the Tapered Thread and the Parallel/Straight Thread when process connection?

A: Not yet, there is a difference in how straight and tapered threads seal. A straight thread will rely on either a seal O-ring or a gasket. Pressure connections which include the suffix EN 837 or DIN 16288 are sealed on the end of the thread with a small diameter O ring groove which is placed on the shoulder of the hex. In the female mating part of the pressure connection there is a hole with sufficient diameter to locate the male end post without pinching the O ring.

However, a tapered thread requires thread sealant – either a compound or thread tape. Tapered thread seal is accomplished via metal-to-metal wedging; tapered threads ALWAYS require thread sealing (tape or liquid).

What’s more, Liquid Thread-seal is a special adhesive which require 2 things to cure: 1, no air; 2. metal surface (chemical reaction with carbon in the seal)

Process Connection seal the Tapered Thread and the Straight Thread

What need to pay attention before seal the Tapered Thread?

The seal is designed to take place between the tapered threads. Tapered pipe threads always need a sealant to seal system fluids and reduce the potential for galling of the threads. The Tapered thread sealant performs both the lubricating and sealing functions. If the two pieces of metal are forced against each other without lubrication, galling is possible.

After following the sealant and lubricant application instructions, the amount of tightening is discretionary. There is no standard for torque or number of turns.

Is there any tip to tell the difference easily between Parallel thread and Tapered thread?

A parallel (Straight) thread often has a “spigot” at the end of the process thread where it seals, especially when it comes to EN837 or DIN 16288, this makes for easy identification.

What Thread Identification Tools are often used?

Caliper: A caliper is used to determine the thread diameter. (Calibration of calipers is the responsibility of the end user.)

Combination Seat and Pitch Gauge: Seat and pitch gauges are conveniently combined into one tool. The seat gauge is used to determine end connection seat angles of 45°, 37°, and 30°. The pitch gauge is used to identify the thread pitch.

Process Connection Caliper + Combination Seat and Pitch Gauge

Note that a pitch gauge may be Unified (threads per inch), Whitworth (threads per inch), or metric (millimeters per thread) as marked on the back of each gauge form.