Monoflanges and Instrument Manifolds

Jump to the Various Sections of this and other Instrument Fittings and Tubing Page: Monoflanges and  Instrument Manifolds | Frequently Asked Questions associated with Monoflanges and Instrument Manifolds | Instrument Monoflanges | Instrument Manifolds | Instrument Fitting Technical Information | Gauging Instrument Threads and Fittings |


Monoflanges and  Instrument Manifolds

Monoflanges and Instrument Manifolds are used as an alternative to multivalve systems. They have been specifically designed to provide a compact installation for gauge or transmitter instruments. An application where a monoflange is used is in place of other equipment. For example, the instance where instead of having one valve and relying on it to close so that a transmitter can be isolated, two valves are used. A double block and bleed monoflange can be used in place of the two valves. It takes away that need for two valves and reduces it all into one. That is the monoflange has two valves on it, which are closed, and a vent that is opened to reduce the pressure between. It has reduced weight and minimum leak paths providing a higher integrity system. The reduced length of the installation also reduces the risk of damage through vibration.

Monoflange manifolds can be mounted directly onto vertical or horizontal flanged connections, allowing a gauge to be kept in an upright position. Suitable for both primary isolation (double block and bleed) and instrument (block and bleed) duties a Monoflange provides isolation, venting and instrument mounting in a single compact unit. The designs incorporate safety features that limit vibration and reduce the overall height of a gauge installation.

In order to ensure System Integrity one must not lose sight of the fact that Monoflanges and Instrument Manifolds are subject to Process Conditions eg., pressure and temperature, therefore it is important to purchase high quality units. 


Frequently Asked Questions associated with Monoflanges and Instrument Manifolds

What materials are used and why?

The materials generally used in producing a suitable alloy are Carbon, Silicon, Manganese, Chromium, Molybdenum, Nickel and Copper in different proportions to create different mechanical properties, such as tensile strength, depending on the conditions in which they are to be placed. That is, for example, whether the environment is corrosive, hot, wet or changeable etc.

What does NPTF thread stand for?

NPT thread stands for National Pipe Taper. It refers to the thread that tapers inward to create a better seal. It is recommended that care is taken in regards to the thread tolerances and only the best quality units are purchased to achieve this. It is imperative that any manufacturer has demonstrated quality assurance to a high standard. It is worthwhile ensuring the quality of threads by gauging at least a proportion of the threads to ensure compliance. Also it is recommended that  thread tolerances and gauging should be specified to a tolerance better than the requirements of ASME B1.20.1. ICEweb's compression fittings page has a more detailed explanation of the gauging and tolerance requirements.

What does ASTM/UNS stand for?

ASTM stands for American Society for Testing and Materials.
UNS stands for Universal Numbering System.

What is an OS&Y valve?

An OS&Y valve is an Outside Screw and Yoke valve. It is a part of the piping specification. It has a firesafe outside screw construction.

Why is the Molybdenum content of 316SS 2% minimum in an offshore environment?

The molybdenum content is at a minimum 2% to prevent chloride corrosion.

Why is 303 or 304SS not to be used in an offshore environment?

303 or 304SS is not to be used because their molybdenum content is nil and thus the material is subjected to chloride corrosion.

Is there a maintenance issue when Close Coupled Monoflanges are used?

If the Monoflange is installed on a clean, non blocking process then it is not an issue in that access to the tapping point is required very rarely. This is especially so on Fieldbus and HART systems as the transmitter provides a huge amount of diagnostics on-line.  The huge advantage of Close Coupling is that many instrument fittings are no longer required, thus eliminating potential leak failure points. 


Instrument Monoflanges

More Details on Monoflanges - From Prochem Pipeline products.

Close Coupled Monoflanges - This design incorporates all the integrity features of the convention models, however adds even more safety and cost saving features. The design eliminates the requirement for instrument tube, fittings and threaded connections. Mono Flange Direct, can be provided in a direct mount version or a interface mounting plate can be facilitated if required - From Prochem Pipeline products.

Installation, Operation and Maintenance of Monoflanges - Comprehensive Information from Anderson and Greenwood.


Instrument Manifolds

Comprehensive Catalogue of Instrument Manifold Technical information and specifications - From Anderson and Greenwood - with 162 pages this is a large 6 Meg download. 

Co-Planer Instrument Manifolds -  Read from page 105 - Anderson Greenwood MC & MT series Integral Manifolds are designed specifically for Rosemount Coplanar style transmitters including Model 3051C, Model 3051P, Model 2024, and the Model 3095 Multivariable transmitters.

Manifold and Isolation Valve Mounting System for Direct Mounting DP Transmitters - The system does not require impulse lines, thereby considerably reducing installation and maintenance costs.

Co-Planer Instrument Manifolds - This technical engineering note from Rosemount gives a good description of the advantages and benefits of these manifolds.

Information on Manifolds 


Instrument Fitting Technical Information

ICEweb’s Instrument Fittings Technical Data Page - This comprehensive page covers just about all the engineering information that you need to know including Design, Interchangability, Installation, Maintenance, Thread Tolerances, Material Selection, Gauging and much more!


Gauging Instrument Threads and Fittings

The following excellent links are from Glastonbury Southern Gage.

  • Fittings Technical Information covering NPT Pipe Threads, Sealing Theory, Pipe Nomenclature, Gauging, Indirect Measurement, Dryseal, Step Plug and Ring, Zones and Truncation Limits, Interchangability of Gauges and Straight Pipe Threads.
  • Definition of Terms - A list of terms pertaining to thread gauges.
  • Gage Criteria - Includes Standards, Reference documents and Gauge criteria.
  • Gage Allowances - A feature which must be considered is the allowance. This computed amount is subtracted from the basic pitch diameter to attain an adjusted maximum size for the external product.The purpose of this is to guarantee ease of assembling the internal and external products.
  • Thread Forms - External and Internal thread Geometry, Unified Inch Screw Threads per ASME B1.1, Federal Standard H28/2, Inch "J" Series SCrew Threads: per Military Standard, MIL-S-8879C (25 July 1991):Metric Screw Threads:per ASME B1.13M, Federal Standard H28/21, Tolerance and Allowance Grades.
  • Master Setting Plugs - Master Set Plug Gages, Thread Ring Diagnostics & Setting, Tightness of Fit
  • Use of Thread Plug Gages - Description on the use of "Go" and "No Go" gauges.
  • Southern Style Thread Rings - This page explains the use and setting of the Southern Style Ring.
  • AGD Style Thread Rings - This page explains the use and setting of the American Gage Design (AGD) Ring.
  • Comparison of Southern Style and AGD Ring - This page is an analysis of the differences between the Southern Style Ring and the American Gage Design (AGD) Ring.
  • Variable Thread Gages - A thread gaging system comprises a list of thread characteristics that must be inspected and the gaging necessary to inspect these characteristics to assure product acceptability. Many organizations through their quality system provide methods / systems for the inspection and acceptability of their product. ASME has set an industry standard of gaging systems for screw threads known as ASME B1.3M. These systems provide different levels of inspection to insure dimensional conformance has been achieved. Covers system 21, 21A, 22 and 23.
  • Pipe Thread History
  • Frequently Asked Questions about Thread Gauges - Some of your questions answered here.
  • Download Comprehensive Technical Book on Gauges - This is a large download >20Megs but is worth it for your library, coving all the Glastonbury Southern Gauge Technical Data it is a great resource.
  • What is a Fixed Limit Gauge? - Part 1 and Part 2 - The objective of this publication is to offer, in usable, simple terms, a basic summary, and source of information for those individuals given responsibility for the purchase and use of attribute or fixed limit gages.

Thread and End Connection Identification Guide - a 56 page document from Swagelok.

Instrumentation - Includes information on;

  • Anderson Greenwood
  • ATKOMATIC Solenoid Valves
  • BuTech Pressure Systems - System components are available in every imaginable alloy to handle pressures form vacuum to 150,000 PSI (10,000 bar) in tube and pipe sizes from 1/8" to 1" and temperatures from -423°F (-253°C) to over 1200°F (649°C). Suitable for extreme application of erosive or corrosive solids, liquids or gases.
  • Circor Tech
  • Circle Seal
  • Classic Filters - These filters are suitable for a variety of gas and liquid applications and are used in a wide range of industries around the world. The disposable microfibre filter elements are extremely efficient as well as being low cost. There are a number of benefits with this type of element and they offer high flow rates with very low pressure drops.
  • DOPAK® Sampling Systems - Due to the growing complexity of the industrial processes in general and more specific for processes in the (petro)chemical and pharmaceutical industries, the need for tests and analyses increases continuously. The need for representative samples plays a critical role in ensuring product verification. Yet sampling directly from the process often includes the risk of exposure to the operator, as well as contamination and pollution to the environment. The Manual Sample Systems method reduces such risks with its patented design and simple method of operation.
  • GO Regulator®
  • GYROLOK® Twin Ferrule Tube Fittings
  • HOKE® Instrumentation Valves
  • King Instrument Company - King Instrument Company offers a comprehensive line of variable area flow metres including acrylic, polysulfone, glass and metal tube metres. Optional alarms and 4-20 mA transmitter available on selected models. See more technical information on ICEweb's Flow page.
  • Leak-Check
  • Prochem NPT Ball Valves - Full Bore 2-piece threaded valves allowing straight-through flow. Virtually no head loss and a superior performer with mildly abrasive as well as corrosive fluids. Ideal for in-line control of process fluids.
  • Saddles
  • Stainless Steel Braided Hoses - Teflon® Lined
  • Stainless Steel Tube
  • Thread Tape & Thread Paste
  • Tooling
  • HOKE® Pipe Fittings

Hydraulic - Includes information on; 

  • Tube-Mac Piping Technologies
  • Tube-Mac - PYPLOK System
  • Tube-Mac Non-welded Flange Connections
  • Seamless Steel Tubes
  • PYPLOK Tooling
  • Stainless Steel Ball Valves - Hydraulic
  • Stainless Steel JIC Fittings - JIC Fittings and Adaptors provide a straightforward, positive, mechanical seal. They have been used for many years for reliable sealing in commercial, industrial and military applications. They are proven to supply dependable, reusable connections under a wide range of operating conditions including extremes of vibration, temperature and shock.

Valves and Actuators - Includes information on;

  • Prochem Actuated Valve Packages -  Specialising in Poyam, ATC, BSM, Pacson and Habonim - Prochem can deliver actuated valves in any combination to suit your valve, actuator and control system specification.
  • AMPO Poyam Valves - These are high-technology valves with best performance and low maintenance costs. Applications include Cryogenic Service, High Pressure, General Service, Metal Seated and Special Application.
  • BSM Valving Solutions - Emergency Fast Track Valve Producers and Delivery Specialists, providing Ultra fast deliveries.  Hard to obtain valves need specialist engineering.  These valves are manufactured  in a wide range of exotic materials to tight specifications..
  • ATC Actuators - The heart of the ATC actuator design is the revolutionary torque conversion mechanism combined with the integrated actuator spring. The simple operating principle offers a combination of high efficiency and small displacement, thereby creating greater design flexibility and improved reliability. This design flexibility, combined with the innovative integration of all actuator parts, results in the most compact actuator available in the market. In virtually all applications, irrespective of hydraulic or pneumatic supply, the ATC actuator diameter is smaller than the Face-to-Face dimension of the valve.
  • Pacson Valves - These are high integrity valves specifically designed for the Oil and Gas Industry.
  • Anderson Greenwood Primary Isolation Valves - Anderson Greenwood Instrumentation Products provide the ultimate solutions for a compact range of forged body Primary Isolation Valves, featuring a choice of end connections, body styles and valve technology.
  • Habonim Industrial Valves and Actuators - Habonim’s new series of ZERO-Stem-Leak valves, is based on the HermetiX™ technology. HermetiX™ is a patented stem seal designed to reduce stem leaks to a minimum and to provide maintenance-free service.

Manufacturing - Includes information on; 

  • Quality Management System
  • Fully Traceable and Complying Threads
  • Leaders in Thread Manufacture
  • Exotic Alloys
  • Engineered Solutions
  • World Class Manufacturing
  • Safety, Integrity and Reliability
  • Special Service
  • Standard Products - BSP Fittings
  • Standard Products - NPT Fittings
  • Standard Products - Other

Piping Products - Includes information on; 

  • Branch Fittings - Details on a  range of Buttweld, Socketweld, Threaded and Flanged reinforced branch fittings from 8 (1/4") NB upwards.
  • BSP Fittings - Prochem manufactures a complete range (from 6 (1/8") - 100 (4") NB) of BSP tapered, BSP parallel and BSP fastening and sealing threads for a variety of applications, in class 150 and 3000. All our BSP threaded fittings are checked with calibrated gauges during manufacture. Each batch is further confirmed as being in compliance with the international standard and before they are released into the market, all products undergo a final visual and dimensional inspection by thread profiling.
  • Buttweld Fittings - Concentric and eccentric reducers, equal and reducing tees, 45° and 90° elbows, buttweld caps and stub ends, are all part of the comprehensive range of buttweld fittings carried by Prochem.
  • Duplex Stainless Steels - Duplex Stainless Steels are unlike the 300 (Austenitic) and 400 (Ferritic) series of stainless steels in that they have a structure consisting of approximately equal amounts of both ferrite and austenite. Therefore, they are often referred to as ferritic-austenitic stainless steels. With a chromium content ranging from 18 to 28 percent, they have improved passivity compared to standard grades. The nickel content ranges from 4.5 to 8 percent which is insufficient to promote a complete austenitic crystal structure, hence the mixed ferrite-austenite structure. Most grades contain molybdenum in the range of 2.5 to 4 percent plus small amounts of nitrogen - enhancing both strength and pitting resistance.
  • Flanges - A flange is designed to connect sections of pipe, or to join a pipe to an assembly such as a pressure vessel, valve or pump. Flanges are joined by bolting, and sealing is completed with the use of gaskets, and fixed to the piping system by welding or threading.
  • Heat Exchanger, Condensor & Boiling Tubes - Useful technical datasheet.
  • Hygienic and Tube - Prochem is well established as a supplier to the food industry. A comprehensive range of BSM, Tri-clover and buttweld fittings and valves are available throughout Australia, complete with welded and annealed polished tubes to suit. 
  • NPT Fittings - NPT fittings are designed for high-pressure (class 3000 - class 6000) applications, and have a distinctive profile for maximum strength. All NPT products are checked with calibrated gauges during the manufacturing process and each batch is further confirmed as being in compliance with the international thread standard. Before they are released into the market, each item is subject to a final visual and dimensional inspection by thread profiling. Materials used comply with ASTM A403 or A182.
  • Pipe Nipples - Pipe nipples are available in ASTM A403 WP316/316L or 304/304L materials, from 6 (1/8?) NB upwards, threaded BSP or NPT, beveled or plain ended. Prochem has the ability to manufacture pipe nipples up to 6000 mm (6 m) in length in sizes 6 NB to 80 NB.
  • Saflok Self-Locking Quick Coupler Range - Prochem provides the safest quick couplers on the market from Saflok. Included the patented locking cam arm, the Saflok design has no peer among other quick couplings.
  • Socketweld Fittings - Prochem manufactures and supplies an extensive range of the highest quality Socketweld fittings, all thoroughly inspected to ensure complete dimensional compatibility with the requirements of the ASME B16.11 manufacturing standards.
  • Swage and Pipe Nipples - Prochem manufactures, stocks and supplies a range of plain, bevelled and threaded concentric and eccentric swage nipples, from 8 (1/4") NB through to 100 (4") NB, with other sizes available on request. All swage nipples are either manufactured from seamless pipe or bar material and have an available working pressure equivavlent to straight seamless pipe. These fittings are available in ASTM A403 WP316/316L or 304/304L materials with other materials available on request.
  • Stainless Steel Shim - Grade 316 shim, annealed and with a hardness rating of HV200, is available in coiled 305 mm (12?) wide rolls, in various thicknesses and sold by the linear metre.
  • Stainless Water Solutions Package - With increased height of buildings, pressures, and life time expectations, people are turning to Stainless Steel for their Water Solutions. These pipe and fittings bear the Water Mark logo ensuring compliance to the industry specifications. Coupled with roll grooving, Prochem has the complete package to offer your Water Solutions package. All designers, architects and builders should contact Prochem to see how we can save you money!!
  • Swing and Spring Check Valves.


Welded Duplex Tube - Welded Duplex Tube to: ASTM SA789/A789 UNS S31803/S32205.

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