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What is Positive Material Identification or PMI? | Methods, Applications, and Advantages

Written by Anup Kumar Dey in Engineering Materials,Instrumentation

Positive Material Identification or PMI is the non-destructive analysis of a metallic alloy to identify the constituent elements and their quantities. To ensure product or alloy quality as per requirement, PMI or Positive Material Identification testing provides a quick solution. PMI is an on-the-spot (on-site) examination method and is highly beneficial for projects where there is a possibility of a material mix-up. To verify the compliance of material certificates of composition, positive material identification is increasingly used in various industries.

A positive material identification test is normally performed using a handheld positive material identification gun. Once the PMI gun is fired at the material for a specified time it automatically produces the element compositions in its display and identifies the material.

Applications of Positive Material Identification

Several accidents in the petroleum and manufacturing sectors highlighted the need for specific materials during the design stage. Positive material identification ensures that the material provided by the vendor is exactly the same as is asked or deviating. So the mechanical and structural integrity of the plant is maintained. This is the reason PMI is widely used as an inspection tool in recent times. The industries that found the application of positive material identification are:

  • Oil & Gas, Chemical, Petrochemical, Refinery
  • Aeronautical
  • Pharmaceutical
  • Power Plant
  • Steel, etc

For verifying in-stock materials, plant inspection, failure analysis, component validation, operational and installation qualification, etc. PMI is widely used. Positive material identification is used as an integral part of the process safety management system. It can also be used to verify welding materials to check if compatible filler material is used.

Positive Material Identification Test
Fig. 1: Positive Material Identification Test

Positive Material Identification Testing Methods / PMI Methods

PMI Analyzers of recent times use any of the below-mentioned three different technologies:

  • X-ray Fluorescence (XRF),
  • Optical Emission Spectrometry (OES) or
  • Laser-Induced Breakdown Spectroscopy (LIBS).

Depending on the analysis needs, the technology is chosen.

XRF Method of PMI:

The XRF method uses x-rays. The component is exposed to a flux of x-rays released from the PMI gun. The atoms of the material absorb this energy and they emit secondary x-rays that are unique to the elements present. By measuring this energy and intensity of the secondary x-rays, the XRF PMI gun provides the composition of the material. ASTM E 1476 provides a well-defined procedure to guarantee reliable and accurate results. XRF positive material identification is one of the quickest and most comprehensive PMI methods.

OES Method of PMI:

In the OES method of positive material identification, the material is exposed to a spark from an electrode in an argon atmosphere. The spark causes the material to emit light having a unique coloration based on the material composition. The chemical composition of the component can be identified by examining the light emitted.

LIBS Method of Positive Material Identification

LIBS or Laser-Induced Breakdown Spectroscopy method of PMI uses a high-focused laser to ablate the sample surface. The electronically excited atoms and ions form a plasma. As these atoms decay back into their ground states, they emit characteristic wavelengths of light, or “unique fingerprints”. These “fingerprints” are distinct for each element which is analyzed by the LIBS analyzer for producing quantitative and qualitative results. This is the newest technology for positive material identification tests.

All the above three technologies come in a portable format inside a hand-held device known as a positive material identification gun. All three produce reliable results. However,

  • XRF can even be used to analyze hot samples like process components at process or power plants. XRF can analyze any type of component whether it is conductive or non-conductive; metallic or non-metallic, granular, or liquid forms.
  • OES PMI test provides superior performance in measuring nitrogen, carbon, boron, and phosphorous in steel.
  • LIBS PMI technology is particularly good for measuring aluminum alloys and makes it a useful method for sorting scrap metal.

Advantages or Benefits of Positive Material Identification or PMI

PMI testing is versatile and can be used on any shape and size. It comes with a number of advantages as follows:

  • A lightweight Handheld device for positive material identification testing.
  • Produce consistent reliable results with a high degree of repeatability.
  • Quick analyses of components or materials.
  • On-site PMI technology
  • Minimal preparation in most cases
  • Large materials-data library for rapid PMI
  • A required alternative for missing original materials reports
  • Highly accurate results for good quality control.
  • Field testing with laboratory quality.
  • Reduced risk of company liability.
  • Fast audit times.

What are Swivel Joints? Working, Types, and Applications of Swivel Joints

Written by Anup Kumar Dey in Piping Design Basics

Whenever there is a need for moveable pipe connections, swivel joints are one of the solutions. They allow to move or rotate one part/component of the system relative to the other. This slow rotational movement provides very good flexibility to the piping system. In this article, we will learn about the basics of swivel joints, their applications, types, features, working, and selection.

What is a Swivel Joint?

A swivel joint is a precision-machined flexible piping component installed between pipes, hoses, or equipment. Their design allows one component of the system to move/rotate relative to the other. Industrial swivel joints are designed to work for an extensive temperature and pressure range. They have to ability to absorb external forces and generated stresses. Properly designed swivel joints have the ability to allow 360-degree rotation in 1, 2, or 3 planes.

Typical Swivel Joint Fittings
Fig. 1: Typical Swivel Joint Fittings

Applications of Swivel Joints

Swivel joints are used in various industries including

  • Chemical and petrochemical industry
  • Power plants
  • Metal and mining
  • Water preparation and municipal technology
  • Pharmaceutical industry
  • Food and drink industry
  • Refining industry
  • Test stands
  • Cooling water supply and water treatment plants
  • Hydraulic systems and pneumatics
  • Ink and paint industry
  • Brewing and distillation industries
  • Automotive industry
  • Recycling industry
  • Loading equipment
  • Aviation and shipbuilding
  • Paper and wood industry
  • Cryogenic industry
  • One of the common uses of swivel joints is in marine loading arms.

Materials for Swivel Joints

Swivel joints are manufactured from a range of materials depending on application requirements. Some of the common swivel joint materials are:

Characteristics of Swivel Joints

The main characteristics of swivel joints are:

  • They are compact engineered components.
  • They provide tight Seals
  • They have a protected bearing chamber
  • Long-Life Bearings
  • Easy Lubrication
  • No Field Adjustment is Necessary
  • They are rigid, safe, and sustainable
  • Swivel joints are available in various sizes starting from 3/4 inches.
  • They are usually produced in flanged, threaded, and butt-welded end connections.

Working of a Swivel Joint

Swivel joints are usually made up of two main components; the sleeve and the body. They are locked in place by one or more ball-bearing races. These ball-bearing races keep the body and swivel sleeve properly aligned to allow the swivel to have a rotary motion around its axis. As the two parts of the swivel can rotate, the piping system components connected to the two ends of the swivel will also rotate freely and independently around the swivel’s axis. To have multiple axes of rotation, multiple swivels are installed with different orientations. This allows the system more freedom of movement between the sides of a fluid conveyance system. Different types of lubricants can be used to lubricate the bearing races.

The actual mechanical work is performed by the swivel’s ball bearings. However, the most important part of the swivel joint is the liquid-tight pressure seal that retains the pressurized working fluid. Pressure seals can be made from thermoplastics or elastomers like PRFE, FKM, Kalrez, fluoroelastomer, Chemraz, and nitrile rubber. The properties of these seal material options make them suitable for service with various fluids over a range of operating temperatures.

Types of Swivel Joints

Swivel joints can be categorized based on various parameters as mentioned below:

Depending on the end connection, there are three types of swivel joints

  • Flanged swivel joint
  • Threaded swivel joint, and
  • Welded swivel joint.

Depending on the working component parts, swivel joints can be of three types:

  • Compact O-ring swivel joints that use an o-ring for pressure seal.
  • V-ring swivel joints that use a triple v-ring packing for sealing. They are robust in construction and suitable for severe applications.
  • Split Flange swivel joints that use a separate bearing pack design with an H-ring and two O-rings.

Depending on the flow paths, there are basically three types of swivel joints:

  • Straight through swivel joints having coaxial flow path.
  • Right-angle swivel joints having outlet ports perpendicular to inlet ports.
  • Offset swivel joints are a combination of both of the above designs

Depending on the axis of rotation, swivel joints are available in various styles which vary from manufacturer to manufacturer.

Selection of Swivel Joint

There are various parameters that must be considered for selecting a swivel joint for an application. Some of these factors are:

  • Type of Fluid used
  • Operating parameters of the fluid
  • Space requirement
  • Machining tolerances
  • Insertion types like Seals, o-rings, wear rings, v-ring, bearings, etc
  • Load requirements
  • Environmental requirements
  • Duty Cycle, torque requirement
  • End connection requirement
  • Material requirement, etc

Proper specification of swivel joint internal components is very important to reduce leaking possibilities. All parts must be designed based on recommended design guidelines.

What is a Desander? Types, Working, Features, and Selection of Desanders

Written by Anup Kumar Dey in Pipeline

A desander is a vital component of the mining and drilling process. Desander is a solid control device with a series of hydro cyclones that separates sand and silt from the rig’s drilling fluid. The desander is fixed at the top of the sludge tank, just after the shale shaker and the degasser, and before the desilter. As they are usually installed at the wellhead in the oil and gas field, they are also known as wellhead desander. Wellhead desanders are produced in both ASME and API design ratings as per requirement.

Desanders are basically solid control devices. Cyclonic desander and desilters use a centrifugal force to separate solids from liquids. There are no rotating components. Centrifugal force is created by turning the head of a centrifugal pump into a high-speed rotating flow inside a cone.

Solids are concentrated near the cone wall in proportion to their mass and exit as underflow at the bottom of the cone. Clean liquids and fine solids return from the overflow at the top of the cone.

Demineralization and sand removal hydro-cyclones are simple mechanical devices with no moving parts, but they facilitate the solids sedimentation process. Drilling mud laden with solids is drawn into the body of the hydro-cyclone and the iatrogenic force of the flow separates the heavy solids from the lighter solids. The heavier solids are discharged at the lowest point (underflow) of the hydro-cyclone and the lighter solids at the highest point (overflow). Solids removal is dependent on feed particle size, liquid concentration, liquid feed pressure (as a function of liquid density), and hydro-cyclone size.

Typical Desanders used in Oil and Gas Industry
Typical Desanders Used in the Oil and Gas Industry

Desanders remove abrasive solids from drilling fluids that vibrators can’t remove. In general, the diameter of the solids separated by the desander is 45 µm to 74 µm and the diameter of the decanter is 15 µm to 44 µm.

Working of Desander

When the drilling fluid reaches the dead grinder, it enters through a pressurized pipe and hits the dead grinder cone first. The way this cone turns the liquid is similar to the flow of water in a sink, except the walls of the desander cone are porous to filter out sand particles.

Desanders have no moving parts and particle removal is accomplished solely by gravity and pressure. Desanders are generally not large tools, about the size of a bathtub for small jobs, and rarely larger than the average car. When the liquid reaches the small end of the cone, it is pushed out of the tube and proceeds to the next step in the purification process.

This type of work is commonly used in the oil industry. Desander is also used in other industries, primarily related to the drilling and extraction of materials such as natural gas. Companies that manage lakes and dams can use desalters and desilters to keep water flowing and remove contaminants.

Types of Desanders

  • Desander of simple cycloning: These are good for sandy or slightly sandy soils. After the sludge has passed through a screening stage to remove oversize, it is fed to a cyclone separator.
  • Desander of double cycloning: Similar to a single cyclone, with the difference that the sludge pass twice through the cyclone so as to separate the finest sand and silt even.

Feature of Desanders

  • Cyclonic desanders and decanters have no moving parts and are extremely reliable solids removal devices when properly operated and maintained.
  • Customized cone configurations.
  • The material of the hydrocyclone is polyurethane, which makes it lightweight and durable.
  • Victaulic clamp connects indoor and outdoor cables for easy removal.
  • Skids mounted with ring bolts welded to the frame.

Selection of Desanders

The parameters that must be looked upon while selecting a desander for the specific application are:

  • The Crude oil quality.
  • External pipe outer diameter and the working pressure of the pipeline.
  • Efficiency and accuracy of Separation.
  • Operating parameters.
  • Desander size requirements
  • Wear resistance and anti-aging properties.
  • Service life.

Advantages of Desanders

Hydrocyclones for desanders and demineralizers in drilling are used to remove sand and silt particles from drilling fluids that have passed through oil and gas vibrating screens. The main advantages of installing a desander are:

  • Preventing solid build-up in equipment and pipelines.
  • Elimination of fine chips
  • Large capacity with a relatively simple structure
  • No rotating parts
  • Easy to use
  • Low downtime and maintenance
  • Protecting downstream equipment from wear and damage

Cavins Desander

Cavins Desander is a specially designed desander by Cavins Corporation which is providing desander solutions for the last 65 years. These easy to install Cavins desanders are widely used to separate abrasive solids from production fluids. They are installed before downhole pumps thus extends the pump life. Desanders by Cavins Corporation works by centrifugal action to separate solid particles. They are available in a range of sizes and flowrates. Cavins desanders are known for long service life, all steel construction, and quality.

Frequently Asked Questions: FAQ

1. What is a Desander?

A Desander is a specialized equipment used in the oil and gas industry for the removal of solid particles, primarily sand, and other abrasive materials, from the production fluids or drilling mud.

2. What is a Desander used for?

Desanders are primarily used to protect downstream equipment, such as pipelines, pumps, and valves, from abrasive damage caused by sand and solids present in oil, gas, or drilling fluid. They ensure the integrity and efficiency of the production process.

3. What are the components of a Desander?

A typical Desander consists of three main components:

  • Inlet Section: This is where the unprocessed fluid enters the Desander.
  • Cyclonic Separation Unit: This component uses centrifugal force to separate solids from the fluid.
  • Outlet Section: Here, the cleaned fluid exits the Desander, while the separated solids are discharged.

4. How does a Desander work?

Desanders work by utilizing centrifugal force to separate heavier solids (like sand) from the incoming fluid. As the fluid enters the cyclonic separation unit, it is spun rapidly, causing the heavier solids to move outward and settle in a collection chamber, while the cleaned fluid continues its path through the outlet.

5. What types of solids can a Desander remove?

Desanders are primarily designed to remove sand, but they can also effectively remove other solid particles such as silt, clay, and small debris from production fluids.

6. Where are Desanders commonly used in the oil and gas industry?

Desanders are used at various stages of the production process, including wellhead facilities, drilling operations, and downstream processing plants. They are also employed in water treatment systems to remove solids from produced water.

7. What are the benefits of using a Desander?

The key benefits of using a Desander include:

  • Protection of downstream equipment from erosion and damage.
  • Improved operational efficiency and reduced maintenance costs.
  • Enhanced production fluid quality and purity.

8. What is the maintenance required for a Desander?

Maintenance for Desanders typically involves regular inspections, cleaning or replacement of worn components, and monitoring of fluid flow rates. The specific maintenance requirements may vary depending on the application and usage.

9. Can Desanders be customized for specific applications?

Yes, Desanders can be customized to meet the specific requirements of different applications. They can be designed with various flow capacities, materials of construction, and control systems to suit the needs of a particular project.

10. Are there alternatives to Desanders for solids removal in the oil and gas industry?

Yes, alternatives such as Desilter (for smaller particles), hydrocyclones, and various filtration systems can be used for solids removal. The choice of equipment depends on factors like particle size, flow rates, and the nature of the solids in the process fluid. Desanders are favored when dealing with larger, abrasive particles like sand.

What is a Pressure Control Valve (PCV)? Types and Applications of PCV

Written by Anup Kumar Dey in Instrumentation

A pressure control valve is a type of control valve that regulates the pressure in the system to regulate the torque of the hydraulic motor shaft or the force of the hydraulic piston rod. The pressure control valves are usually used to create extreme pressure within the system and avoid overloading.

They keep the outlet pressure permanently at the fixed point and at the same time protect the system from overloading. These types of valves are designed for economical pressure control in an accumulator-operated circuit which is employed as an emergency control power source.

Functions of Pressure Control Valves of PCVs

From the term itself, it is clear that the primary function of each PCV is controlling the pressure. Other benefits that pressure control valves provide are:

  • Sequential control
  • Restrained movement control
  • Managing the load
  • Limiting system pressure
  • Controls the pressure in the selected section of the circuit
  • Sequence motion
  • Actuator sequence control
  • Pump loading and unloading control
  • Protecting systems from overpressure

Pressure control valves are used in almost every hydraulic and pneumatic system. They perform different functions from maintaining system pressure below specific limits to maintaining set pressure levels in loop sections. The efficient working of the pressure control valve is very important to ensure the efficient working of the system.

Types of Pressure Control Valves

The pressure control valve or PCV has the following four major types:

  • Pressure Relief Valves
  • Sequencing Valve
  • Pressure-Reducing Valve, and
  • Counterbalance Valve

1) Pressure Relief Valves

Maximum pneumatic and hydraulic drive appliances are planned to work within a specific pressure range. This pressure range is the force function that the actuators in the system need to produce to perform the desired task. Without regulating these forces, they may damage expensive power parts and equipment.

A pressure relief valve may prevent your system from this hazard. This valve limits the extreme pressure in the system by venting excess gas when the pressure is too high. The cracking pressure is the limit of the pressure at which the relief valve first opens and fluid flows.

As your valve bypasses the maximum rated flow, it has the maximum flow pressure. The main difference between cracking pressure and full flow pressure is occasionally denoted as differential pressure or bypass pressure.

Sometimes, this pressure release may not be a problem. Wasting energy on stray gas from the valve before the maximum setting is reached can be harmful. This may increase the extreme system pressure beyond the ratings of other parts. Click here to learn about pressure relief valve sizing and types.

2) Sequencing Valve

Circuits with multiple actuators may require the actuators to move in a definite sequence or order. Limit timers, switches, or other digital control units used in conjunction with sequencing valves can be used to achieve this.

A sequence valve is a normally closed, two-way valve that controls the order in which various functions occur in a circuit. They are similar to direct-acting safety valves, but the spring chamber is generally vented to the outside rather than internally vented to an outlet like a relief valve.

Sequencing valves allow compressed fluids to flow to a second function only after the precedence function has been accomplished and satisfied first. Closing the sequence valve permits fluid to flow freely to the main circuit and performs the 1st function until the valve pressure setting is reached.

Cylinders can also be sized according to the load they must move to achieve the desired sequence. The cylinder that needs the lowest pressure to move expands first. At the stroke end, the system pressure improves and the 2nd cylinder extends.

In many applications, space constraints and power needs dictate the size of the cylinder. In such cases, sequence valves are employed to activate the cylinders in the desired order. Sequence valves may have check valves that permit reverse flow from the secondary circuit to the primary circuit.    

However, the sequence actions are only provided when the flow is from the parent loop to the child loop. In some applications, an interlock prevents the sequence from occurring until the main actuator reaches a certain position. This happens remotely.

3) Pressure-Reducing Valve

The pressure-reducing valve is one of the most efficient types of pressure-control valve. It is used for maintaining low pressure in pneumatic systems. It is typically a two-way valve that opens and closes when there is enough downstream pressure.

pressure-reducing valves have the following two types:

  • Direct acting valve
  • Pilot operated valve

A direct-acting valve is a pressure-reducing valve that limits the extreme pressure available in the secondary circuit irrespective of pressure variations in the primary circuit.

This assumes the workload produces no backflow into the reducing valve port, in which case the valve will close. The pressure-sensing signal comes from the secondary circuit.

This valve is normally closed and senses the inlet pressure so it works in reverse to the relief valve. When the outlet pressure reaches a specific pressure, the valve closes and only a small amount of gas escapes from the low-pressure side of the valve. It usually flows via the orifice in the spool.

The spool of a pilot-operated pressure-reducing valve is hydraulically balanced by the downstream pressure across the valve. The pilot valve exhausts enough air to position the spool so that the flow rate through the main valve meets the requirements of the pressure-reducing circuit.

High-pressure gas leaks into the pressure-reducing section of the valve and returns to the tank through a pilot-operated relief valve. This type of valve usually contains a larger spring adjustment range and better repeatability than direct-acting valves. But in hydraulic applications, oil contamination will block flow to the pilot valve and prevent the main valve from closing properly. Click here to learn more about pressure-reducing valves.

4) Counterbalance Valve

The counterbalance valve is normally closed and is most commonly employed to maintain precise pressure on a section of the circuit, typically to balance weight. The valve design is best suitable for balancing external forces or counteracting weight in the press to prevent free fall. The primary port of the valve is linked to the rod end of the cylinder and the secondary port is linked to the directional control valve. The pressure is fixed somewhat more than necessary to prevent the load from free-falling.  

When hydraulic fluid flows to the head end, the cylinder extends, increasing pressure at the rod end and moving the main piston within the valve. This generates a flow path for the fluid through the secondary port to the directional control valve and reservoir. When the load increases, the built-in non-return valve opens and the cylinder can contract unhindered.

A counterbalance valve can be remotely operated to relieve cylinder back pressure and increase power at the bottom of the stroke if required. As the cylinder is extended, the valve should be open and its secondary port linked to the reservoir.

Pressure Control Valve Applications

The pressure control valves are most commonly used in pneumatic and hydraulic systems. These valves also help in a variety of functions, from keeping system pressures safely below a desired upper limit to maintaining a set pressure in part of a circuit. Major applications of PCV are found in:

  • Air compressors
  • Boiler houses and distribution mains.
  • Tracer lines.
  • Small tanks.
  • Acid baths.
  • Unit heaters.
  • Small heater batteries.
  • OEM equipment.
  • In inlet of the flow of load in pressure reactors.
  • Aircraft and Aerospace
  • Cooking water pressure reduction.
  • Oxyfuel welding and cutting.
  • Propane/LPG gas – industrial. transportation and storing.
  • Mining industries
  • Tooling and Automation

Further Studies and Video Courses

If you wish to enhance your knowledge further then you can have a look at the following online video courses:

What is a Demister Pad? Its Working, Application, Types, and Features

Written by Anup Kumar Dey in Process

A demister pad is a device that can remove micron-size entrained liquid droplets from a gas/vapor stream. Demister means the removal of the mist, and hence the main function of demister pads is to remove liquid particles and dust particles from the gaseous phase. Sometimes they are also known as mist eliminators or vapor pads. Demister pads are often found to be installed just below the top vapor outlet of a vapor-liquid separator or distillation tower. In this article, we will learn about the working, types, features, and applications of demister pads.

For gas and liquid separating and filtering, Demister pads serve as an efficient and economical product. In chemical, pharmacy, petroleum, papermaking, food, mineral, and other industries, Demister pads are widely used in gas and liquid separator towers. Some of the applications of demister pad include

  • Inlet Scrubbers
  • Compressor System
  • Three Phase Separators
  • Cold Separators
  • Glycol Dehydration
  • Compression Operations in Natural Gas Processing
  • Amine Absorption Column
  • Steam Drums
  • Seawater Desalination Plant
  • Flue Gas Desulphurisation
  • Catalytic Cracking
  • Gas Absorption and Stripping
  • Condensation
  • Gas Compression
  • Dehumidification and Drying
  • Spray Removal and Desalination
  • Crude Oil Distillation
  • Alkylation
  • Stripping Operation in Desulphurization and Hydro Fining Process
  • Sulfur Condensers
  • Knockout Drums

The demister with its high filtering efficiency (usually greater than 99%) is composed of knitted wire mesh. They are specially woven and interlocked to ensure even and smooth meshes for efficient filtering. Depending on the different filtering requirements, the mesh design can be customized.

Working of a Demister Pad

The demister pads function by coalescing smaller liquid droplets to grow bigger by creating an obstruction in the flow path and then isolating them by gravity. When a demister pad is installed in the path of a rising gas stream, the wire meshes create an obstruction. This causes the mist particles to collide with the mesh filament where the mist diffuses on the filament surface to create droplets that follow along the filaments of the two-wire intersection. These droplets stick together and grow bigger and when they are too heavy to rise with the gas stream, they isolate. The gas stream is not affected by the obstruction and can easily escape.

Working of Demister Pads
Fig. 1: Working of Demister Pads

Separation of the liquid from the gas improves the operating condition by optimizing the process indicators. It also reduces the corrosion possibility of the equipment which in turn extends equipment life. The liquid droplet separation also increases the recovery of valuable materials, thus protecting the environment and decreasing air pollution.

The main objective of demister pads to generate obstruction can be achieved by a variety of geometries. Demister pads can be a mesh-type coalescer, vane pack, or other structure.

The efficiency of demister pads is dependent on the following parameters:

  • Droplet Size
  • Mesh Wire Size
  • Surface Area of Mesh
  • Pad thickness, and
  • Physical Properties of the System

The main design parameters for demister pads are

  • Liquid Loading
  • Gas and Liquid Viscosity
  • Gas Pressure
  • Surface Tension

Types of Demister Pads

Demister pads are usually available in the following four types:

  • Standard type,
  • Efficient type,
  • High penetration type, and
  • Shock absorber type.

Materials for Demister Pads

Industrial demister pads are manufactured from metallic or plastic materials. The common metallic materials are:

  • Stainless steel (For water solution, nitric acid, fatty acid, reduced crude fraction)
  • Carbon steel.
  • Copper.
  • Titanium alloy.
  • Nickel Alloys (Food products, Caustic Soda)
  • Monel (Diluted acid, Alkalis)

On the other hand, the common plastics (for corrosive service at moderate temperatures) used to manufacture knitted mesh demister pads are:

  • PP.
  • PE.
  • PVC.
  • FEP.
  • PTFE.
  • PVDF

Characteristic Features of Demister Pad

A good demister pad should possess the following characteristic features:

  • High porosity and less pressure drops.
  • Simple structure.
  • Lightweight and easy to transport.
  • Large surface area and high separating efficiency.
  • Corrosion and rust resistance.
  • Durable and long service life.
  • Easy to install, operate and maintain.

Demister pads are available in the following shapes (Refer to Fig. 2):

  • Round shape
  • Ring shape
  • Rectangular shape
  • Customized shape
Shapes of Industrial Demister Pads
Fig. 2: Shapes of Industrial Demister Pads

Construction of Demister Pads

Demister pads are designed into various structures to achieve high tensile strength, better efficiency, and higher bearing capacity. The pad surface can be smooth or ginning. For small-diameter applications, the demister pads are made from integral structures whereas they are made from separated structures for large-diameter applications. Support grids are sometimes provided in form of round bars or flat bars to provide greater strength.

Demister Pad Installation

They can be installed vertically or horizontally depending on the application. There are two types of installation; upload type and download type.
Upload-type demister pad installation is suitable for places where the manhole is located above the demister pad. On the contrary, download types pad installation is suitable where the manhole is located below the demister pad.

Demister Pad Specifications

Industrial demister pads are usually specified using the following parameters:

  • Sheet Size
  • Mesh per inch/Mesh Size
  • Wire Size
  • Type and finish
  • Materials
  • Outside Diameter
  • Grid requirements
  • Application/Fluid Service
  • Horizontal or vertical installation
  • Operating Process Parameters
  • Efficiency required

Advantages of Demister Pads

Demister pads or mist eliminators provide various benefits:

  • High separation efficiency
  • Low-pressure drop
  • Easy installation and low maintenance
  • High resistance to fouling
  • Economical

What Does MSS Mean in Piping Industry? List of MSS Standards

Written by Anup Kumar Dey in Piping Design Basics

The full form of MSS is the Manufacturers Standardization Society of the Valve and Fittings Industry. They are a non-profit technical association. Officially founded in the year 1924, the Manufacturers Standardization Society of the Valve and Fittings Industry (MSS) publishes various international codes and standards to ensure compliance, interoperability, safety, and operation of process piping systems for various industries like petroleum, petrochemical, food, beverage, and utility. The MSS standards mainly cover the following product segments:

  • Valves, Actuators, Valve modifications.
  • Pipe hangers.
  • Pipe fittings
  • Flanges
  • Seals, etc

With its 26 technical committees, MSS reviews and writes various useful industry standards. They have a wide range of participations including some of the most prestigious institutions like

  • American Society for Testing and Materials ASTM),
  • American Society of Mechanical Engineers (ASME),
  • American National Standards Institute (ANSI),
  • American Petroleum Institute (API),
  • American Waterworks Association (AWWA), and
  • the National Fire Protection Association (NFPA).

The Manufacturers Standardization Society of the Valve and Fittings Industry provides membership benefits to the member organizations including access to all their standards. Some of the standards and specifications developed by MSS are widely used in the piping industry. The standards developed by the MSS are provided with the term MSS followed by the term SP followed by the number and year of the latest publication (edition). Example; MSS SP-44-2019 or MSS SP-58-2018.

The following section will list the common MSS Standards that are extensively used in the Piping Industry.

List of MSS Standards

The following table lists some of the popular MSS standards:

MSS StandardDescriptionLatest Publication Year
MSS-SP-25Standard Marking System for Valves, Fittings, Flanges, and Unions2018
MSS-SP-44Steel Pipeline Flanges2019
MSS-SP-55Quality Standard for Steel Castings for Valves, Flanges, Fittings, and Other Piping Components – Visual Method for Evaluation of Surface Irregularities2011
MSS-SP-58Pipe Hangers and Supports – Materials, Design, Manufacture, Selection, Application, and Installation2018
MSS-SP-75High-Strength, Wrought, Butt-Welding Fittings2019
MSS-SP-86Recommended Rules and Guidelines for SI (Metric) Data in MSS Standards2021
MSS-SP-92Valve User Guide2021
MSS-SP-96Terminology for Valves, Fittings, and Their Related Components2017
MSS-SP-138Quality Standard Practice for Oxygen Cleaning of Valves and Fittings2014
MSS-SP-144Pressure Seal Bonnet Valves2020
MSS-SP-6Standard Finishes for Contact Faces of Pipe Flanges and Connecting-End Flanges of Valves and Fittings2021
MSS-SP-9Spot Facing for Bronze, Iron, and Steel Flanges2018
MSS-SP-42Corrosion-Resistant Gate, Globe, Angle, and Check Valves with Flanged and Butt Weld Ends (Classes 150, 300, & 600)2013
MSS-SP-43Wrought and Fabricated Butt-Welding Fittings for Low Pressure, Corrosion Resistant Applications2019
MSS-SP-45Bypass and Drain Connections2020
MSS-SP-51Class 150LW Corrosion Resistant Flanges and Cast Flanged Fittings2021
MSS-SP-53Quality Standard for Steel Castings and Forgings for Valves, Flanges, Fittings, and Other Piping Components – Magnetic Particle Examination Method2021
MSS-SP-54Quality Standard for Steel Castings for Valves, Flanges, Fittings, and Other Piping Components – Radiographic Examination Method2013
MSS-SP-60Connecting Flange Joints between Tapping Sleeves and Tapping Valves2021
MSS-SP-61Pressure Testing of Valves2019
MSS-SP-65High-Pressure Chemical Industry Flanges and Threaded Stubs for Use with Lens Gaskets2019
MSS-SP-67Butterfly Valves2022
MSS-SP-68High-Pressure Butterfly Valves with Offset Design2021
MSS-SP-70Gray Iron Gate Valves, Flanged and Threaded Ends2011
MSS-SP-71Gray Iron Swing Check Valves, Flanged and Threaded Ends2018
Table 1: MSS SP Standards

Other MSS Standards

Other MSS SP standards are listed below:

  • MSS-SP-72-2010a: Ball Valves with Flanged or Butt-Welding Ends for General Service
  • MSS-SP-78-2011: Gray Iron Plug Valves, Flanged, and Threaded Ends
  • MSS-SP-79-2018: Socket-Welding Reducer Inserts
  • MSS-SP-80-2019: Bronze Gate, Globe, Angle, and Check Valves
  • MSS-SP-81-2021: Stainless-Steel or Stainless-Steel-Lined, Bonnetless, Knife Gate Valves with Flanged Ends
  • MSS-SP-83-2018: Class 3000 and 6000 Pipe Unions, Socket Welding, and Threaded (Carbon Steel, Alloy Steel, Stainless Steel, and Nickel Alloys)
  • MSS-SP-85-2011: Gray Iron Globe & Angle Valves, Flanged and Threaded Ends
  • MSS-SP-87-1991(R1996 – Reinstated 2011): Factory-Made Butt-Welding Fittings for Class I Nuclear Piping Applications
  • MSS-SP-88-2021: Diaphragm Valves
  • MSS-SP-91-2009: Guidelines for Manual Operation of Valves
  • MSS-SP-93-2020: Quality Standard for Steel Castings and Forgings for Valves, Flanges, Fittings, and Other Piping Components – Liquid Penetrant Examination Method
  • MSS-SP-94-2020: Quality Standard for Ferritic and Martensitic Steel Castings and Forgings for Valves, Flanges, Fittings, and Other Piping Components – Ultrasonic Examination Method
  • MSS-SP-95-2018: Swage(d) Nipples and Bull Plugs
  • MSS-SP-97-2019: Integrally Reinforced Forged Branch Outlet Fittings: Socket Welding, Threaded, and Buttwelding Ends
  • MSS-SP-98-2020: Protective Coatings for the Interior of Valves, Hydrants, and Fittings
  • MSS-SP-99-2016a: Instrument Valves
  • MSS-SP-100-2020: Qualification Requirements for Elastomer Diaphragms for Nuclear Service Diaphragm Valves
  • MSS-SP-101-2014: Part-Turn Valve Actuator Attachment – FA Flange and Driving Component Dimensions and Performance Characteristics
  • MSS-SP-102-1989(R2001): Multi-Turn Valve Actuator Attachment – Flange and Driving Component Dimensions and Performance Characteristics
  • MSS-SP-104-2018: Wrought Copper, Solder-Joint Pressure Fittings
  • MSS-SP-105-2016a: Instrument Valves for Code Applications
  • MSS-SP-106-2019: Cast Copper Alloy Flanges, and Flanged Fittings: Class 125, 150, and 300
  • MSS-SP-108-2020, Resilient-Seated Cast Iron Eccentric Plug Valves
  • MSS-SP-109-2018, Weld-Fabricated, Copper Solder-Joint Pressure Fittings
  • MSS-SP-110-2010, Ball Valves Threaded, Socket-Welding, Solder Joint, Grooved and Flared Ends
  • MSS-SP-111-2020, Gray-Iron, and Ductile-Iron Tapping Sleeves
  • MSS-SP-112-2021, Quality Standard for Evaluation of Cast Surface Finishes – Visual and Tactile Method
  • MSS-SP-113-2021, Connecting Joints between Tapping Machines and Tapping Valves
  • MSS-SP-114-2018, Corrosion Resistant Pipe Fittings Threaded and Socket Welding Class 150 and 1000
  • MSS-SP-115-2017, Excess Flow Valves, NPS 1-1/4 and Smaller, for Fuel Gas Service
  • MSS-SP-116-2019, Service-Line Valves and Fittings for Drinking Water Systems
  • MSS-SP-117-2011, Bellows Seals for Globe and Gate Valves
  • MSS-SP-119-2010, Factory-Made Wrought Belled End Pipe Fittings for Socket-Welding
  • MSS-SP-120-2017, Flexible Graphite Packing Sealing for Rising Stem Valves
  • MSS-SP-122-2017, Plastic Industrial Ball Valves
  • MSS-SP-123-2018, Non-Ferrous Threaded and Solder-Joint Unions for Use with Copper Water Tube
  • MSS-SP-124-2020, Fabricated Tapping Sleeves
  • MSS-SP-125-2018, Check Valves: Gray Iron and Ductile Iron, In-Line, Spring-Loaded, Center-Guided
  • MSS-SP-126-2013, In-Line, Spring-Assisted, Center-Guided Check Valves (Carbon, Alloy Steel, Stainless Steel, & Nickel Alloys)
  • MSS-SP-127-2014a, Bracing for Piping Systems: Seismic-Wind-Dynamic Design, Selection, and Application
  • MSS-SP-128-2012, Ductile Iron Gate Valves
  • MSS-SP-129-2021, Copper-Nickel Fittings
  • MSS-SP-130-2013, Bellows Seals for Instrument Valves
  • MSS-SP-131-2017, Metallic Manually Operated Gas Distribution Valves
  • MSS-SP-132-2022, Compression Packing Systems for Instrument Valves
  • MSS-SP-134-2012, Valves for Cryogenic Service, including Requirements for Body/Bonnet Extensions
  • MSS-SP-135-2021, High-Pressure Knife Gate Valves
  • MSS-SP-136-2020, Ductile Iron Swing Check Valves
  • MSS-SP-137-2020, Quality Standard for Positive Material Identification of Metal Valves, Flanges, Fittings, and Other Piping Components
  • MSS-SP-139-2014, Copper Alloy Gate, Globe, Angle, and Check Valves for Low Pressure/Low-Temperature Plumbing Applications
  • MSS-SP-140-2021, Quality Standard Practice for Preparation of Valves and Fittings for Silicone-Free Service
  • MSS-SP-141-2012, Multi-Turn and Check Valve Modifications
  • MSS-SP-142-2012, Excess Flow Valves for Fuel Gas Service, NPS 1½ through 12
  • MSS-SP-143-2018, Live-Loaded Valve Stem Packing Systems
  • MSS-SP-145-2013, Metal Ball Valves for Low Pressure/Low-Temperature Plumbing Applications
  • MSS-SP-146-2019, High-Pressure Knife Gate Valves: Iron and Ductile Iron, Lug-, Wafer-, and Flange-Type
  • MSS-SP-147-2014, Quality Standard for Steel Castings Used in Standard Class Steel Valves – Sampling Method for Evaluating Casting Quality
  • MSS-SP-148-2019, Low-Pressure Flanged or Lugged Carbon Steel and Iron or Ductile Iron, Cast or Fabricated, Bonnetless, Knife Gate Valves without Liners
  • MSS-SP-149-2018, Preformed Elastomeric and Polytetrafluoroethylene (PTFE) V-Ring Packing Sets for Waterworks Valves
  • MSS-SP-150-2019, Valves for Use in Hydrogen Peroxide Service
  • MSS-SP-151-2021, Pressure Testing of Knife Gate Valves
  • MSS-SP-152-2022, Knife Gate Valves for Double Block and Bleed
  • MSS-SP-153-2017, Modification of New Water Works Valves
  • MSS-SP-154-2018, Low-Pressure Knife Gate Valves for Double Block and Bleed
  • MSS-SP-155-2018, Plastic-Lined Metal Valves
  • MSS-SP-156-2019, Ductile Iron, Metal-Seated, Non-Lubricated, Eccentric Plug Valves
  • MSS-SP-157-2020, Quality Standard for Phosphate Surface Protective Coatings for Valves, Fittings, and Related Steel Piping Components
  • MSS-SP-158-2021, Supplemental High-Pressure Gas Test Procedures for Valves