Recent Posts

Pumps & Pumping Systems

Written by Anup Kumar Dey in Mechanical,Piping Design Basics,Piping Interface

What are Pumping Systems?

Pumping systems account for nearly 20% of the world’s electrical energy demand. Furthermore, they range between 25-50% of the energy usage in certain industrial plant operations. The use of pumping systems is widespread. They provide domestic, commercial, and agricultural services. In addition, they provide municipal water and wastewater services, and industrial services for food processing, chemical, petrochemical, pharmaceutical, and mechanical industries.

The function of a Pump

Pumps have two main purposes:

  • Transfer of liquid from one place to another place (e.g. water from an underground aquifer into a water storage tank)
  • Circulate liquid around a system (e.g. cooling water or lubricants through machines and equipment)

Components of the Pumping System

The main components of a pumping system are:

  • Pumps (different types of pumps are explained in section 2)
  • Prime movers: electric motors, diesel engines, or air system
  • The piping used to carry the fluid
  • Valves used to control the flow in the system
  • Other fittings, controls, and instrumentation
  • End-use equipment, which has different requirements (e.g. pressure, flow) and therefore determines the pumping system components and configuration. Examples include heat exchangers, tanks, and hydraulic machines

Pumping System Characteristics

The pressure is needed to pump the liquid through the system at a certain rate. This pressure has to be high enough to overcome the resistance of the system, which is also called the “head”. The total head is the sum of the static head and friction head.

Static head

Static head is the difference in height between the source and destination of the pumped liquid (see Fig. 1)

Static head is independent of the flow (see Fig. 1)

The static head consists of:

  • Static suction head (hS): resulting from lifting the liquid relative to the pump centerline. The hS is positive if the liquid level is above the pump centerline, and negative if the liquid level is below the pump centerline (also called “suction lift)
  • Static discharge head (hd): the vertical distance between the pump centerline and the surface of the liquid in the destination tank

The static head at a certain pressure depends on the weight of the liquid and can be calculated with this equation as shown in Fig. 1:

Pumping System and its Characteristics
Fig. 1: Pumping System and its Characteristics

Friction head

  • This is the loss needed to overcome that is caused by the resistance to flow in the pipe and fittings.
  • It is dependent on size, condition and type of pipe, number and type of pipe fittings, flow rate, and nature of the liquid.
  • The friction head is proportional to the square of the flow rate as shown in Fig. 2.
  • A closed-loop circulating system only exhibits a friction head (i.e. not a static head).

In most cases, the total head of a system is a combination of static head and friction head as shown in Fig. 2. The left figure is a system with a high static head (i.e. the destination reservoir is much higher than the source). The right figure is a system with a low static head (i.e. the destination reservoir is not much higher than the source).

Friction Head and Performance curve
Fig. 2: Friction Head and Performance curve

Pump performance curve

The head and flow rate determine the performance of a pump, which is graphically shown in Fig. 2 as the pump performance curve or pump characteristic curve.

Fig. 2 (Top Left) shows a typical curve of a centrifugal pump where the head gradually decreases with increasing flow.

As the resistance of a system increases, the head will also increase. This, in turn, causes the flow rate to decrease and will eventually reach zero. A zero flow rate is only acceptable for a short period without causing the pump to burn out.

Pump operating point

The rate of flow at a certain head is called the duty point. The pump performance curve is made up of many duty points.

The pump operating point is determined by the intersection of the system curve and the pump curve as shown in Fig. 3

The Best Efficiency Point (BEP) is the pumping capacity at maximum impeller diameter, in other words, at which the efficiency of the pump is highest. All points to the right or left of the BEP have a lower efficiency.

Pump Suction Performance

Pump Cavitation or vaporization is the formation of bubbles inside the pump. This may occur when the fluid’s local static pressure becomes lower than the liquid’s vapor pressure (at the actual temperature). A possible cause is when the fluid accelerates in a control valve or around a pump impeller.

Vaporization itself does not cause any damage. However, when the velocity is decreased and pressure increases, the vapor will evaporate and collapse. This has three undesirable effects:

  1. Erosion of vane surfaces, especially when pumping water-based liquids
  2. Increase of noise and vibration, resulting in shorter seal and bearing life
  3. Partially choking the impeller passages, which reduces the pump performance and can lead to loss of total head in extreme cases.

The Net Positive Suction Head Available (NPSHA) indicates how much the pump suction exceeds the liquid-vapor pressure, and is a characteristic of the system design.

The NPSH Required (NPSHR) is the pump suction needed to avoid cavitation and is a characteristic of the pump design.

Pump Operating point and Pump classification
Fig. 3: Pump Operating point and Pump classification

Type of pumps

  • Pumps come in a variety of sizes for a wide range of applications. They can be classified according to their basic operating principle as dynamic or positive displacement pumps
  • In principle, any liquid can be handled by any of the pump designs.
  • The centrifugal pump is generally the most economical but less efficient.
  • Positive displacement pumps are generally more efficient than centrifugal pumps but have higher maintenance costs. Click here to know the differences between a centrifugal pump and a positive displacement pump.

Positive displacement pumps are distinguished by the way they operate: liquid is taken from one end and positively discharged at the other end for every revolution.

In all positive displacement type pumps, a fixed quantity of liquid is pumped after each revolution. So if the delivery pipe is blocked, the pressure rises to a very high value, which can damage the pump.

Positive displacement pumps are widely used for pumping fluids other than water, mostly viscous fluids.

Positive displacement pumps are further classified based on the mode of displacement:

  • Reciprocating pump if the displacement is by reciprocation of a piston plunger. Reciprocating pumps are used only for pumping viscous liquids and oil wells.
  • Rotary pumps if the displacement is by rotary action of a gear, cam, or vanes in a chamber of the diaphragm in a fixed casing. Rotary pumps are further classified as internal gear, external gear, lobe, and slide vane, etc. These pumps are used for special services with particular conditions existing in industrial sites.

Dynamic pumps are also characterized by their mode of operation: a rotating impeller converts kinetic energy into pressure or velocity that is needed to pump the fluid.

There are two types of dynamic pumps:

  • Centrifugal pumps are the most common pumps used for pumping water in industrial applications. Typically, more than 75% of the pumps installed in an industry are centrifugal pumps.
  • Special effect pumps are particularly used for specialized conditions at an industrial site.      

Centrifugal Pumps

A centrifugal pump is one of the simplest pieces of equipment in any process plant. The figure (Fig. 4) shows how this type of pump operates:

The liquid is forced into an impeller either by atmospheric pressure or in the case of a jet pump by artificial pressure.

The vanes of the impeller pass kinetic energy to the liquid, thereby causing the liquid to rotate. The liquid leaves the impeller at high velocity.

The impeller is surrounded by a volute casing or in the case of a turbine pump a stationary diffuser ring. The volute or stationary diffuser ring converts the kinetic energy into pressure energy.

A centrifugal pump has two main components. First, a rotating component comprised of an impeller and a shaft. And secondly, a stationary component comprised of a casing, casing cover, and bearings.

Centrifugal Pumps
Fig. 4: Centrifugal Pumps

What is an Impeller?

An impeller is a circular metal disc with a built-in passage for the flow of fluid. Impellers are generally made of bronze, polycarbonate, cast iron, or stainless steel, but other materials are also used.

The number of impellers determines the number of stages of the pump. A single-stage pump has one impeller and is best suited for low head (= pressure)

Types of Impellers

Impellers can be classified on the basis of (which will determine their use):

  • The major direction of flow from the rotation axis
  • Suction type: single suction and double suction
  • Shape or mechanical construction: Closed impellers have vanes enclosed by shrouds; Open and semi-open impellers; Vortex pump impellers. Fig. 4 shows an open-type impeller and a closed-type impeller

Shaft

The shaft transfers the torque from the motor to the impeller during the startup and operation of the pump.

The function of the Pump Casings

Casings have two functions

  • The main function of the casing is to enclose the impeller at suction and delivery ends and thereby form a pressure vessel.
  • A second function of the casing is to provide a supporting and bearing medium for the shaft and impeller.

Types of Pump Casing

There are two types of casings

  • Volute casing (Fig. 5-A) has impellers that are fitted inside the casings. One of the main purposes is to help balance the hydraulic pressure on the shaft of the pump.
  • The circular casing has stationary diffusion vanes surrounding the impeller periphery that convert speed into pressure energy. These casings are mostly used for multi-stage pumps. The casings can be designed as solid casing (one fabricated piece) or split casing (two or more parts together)

Assessment of pumps

The work performed by a pump is a function of the total head and of the weight of the liquid pumped in a given time period. Pump shaft power (Ps) is the actual horsepower delivered to the pump shaft, and can be calculated as follows:

Pump shaft power Ps = Hydraulic power hp / Pump efficiency ηpump

or Pump efficiency ηpump  = Hydraulic power / Pump shaft power

Pump output, water horsepower or hydraulic horsepower (hp) is the liquid horsepower delivered by the pump, and can be calculated as follows:

Hydraulic power hp = Q (m3/s) x (hd – hs in m) x ρ (kg/m3) x g (m/s2) / 1000

Where:

  • Q = flow rate
  • hd  = discharge head
  • hs = suction head
  • ρ = density of the fluid
  • g = acceleration due to gravity

In practice, it is more difficult to assess pump performance. Some important reasons are:

Absence of pump specification data

Pump specification data (see Worksheet 1 in section 6) are required to assess the pump performance. Most companies do not keep the original equipment manufacturer (OEM) documents that provide these data. In these cases, the percentage of pump loading for a pump flow or head cannot be estimated satisfactorily.

Difficulty in flow measurement:

It is difficult to measure the actual flow. The methods are used to estimate the flow. In most cases, the flow rate is calculated based on the type of fluid, head and pipe size, etc, but the calculated figure may not be accurate. Another method is to divide the tank volume by the time it takes for the pump to fill the tank. This method can, however, only be applied if one pump is in operation and if the discharge valve of the tank is closed. The most sophisticated, accurate, and least time-consuming way to measure the pump flow is by measurement with an ultrasonic flow meter.

Improper calibration of pressure gauges and measuring instruments

Proper calibration of all pressure gauges at suction and discharge lines and other power measuring instruments is important to obtain accurate measurements. But calibration has not always been carried out.  Sometimes correction factors are used when gauges and instruments are not properly calibrated. Both will lead to incorrect performance assessment of pumps.

Energy efficiency opportunities

This section includes the factors affecting pump performance and areas of energy conservation. The main areas for energy conservation include:

  1. Selecting the right pump
  2. Controlling the flow rate by speed variation
  3. Pumps in parallel to meet varying demand
  4. Eliminating the flow control valve
  5. Eliminating by-pass control
  6. Start/stop control of the pump
  7. Impeller trimming
  8. Selecting the Right Pump

Selecting the Right Pump

Fig. 5-B shows typical vendor-supplied pump performance curves for a centrifugal pump where clear water is the pumping liquid.

In selecting the pump, suppliers try to match the system curve supplied by the user with a pump curve that satisfies these needs as closely as possible.

The operating point is where the system curve and pump performance curve intersect (as explained in the introduction)

The Best Efficiency Point (BEP) is the pumping capacity at maximum impeller diameter, in other words, at which the efficiency of the pump is highest. All points to the right or left of the BEP have a lower efficiency.

Pump Curves
Fig. 5: Pump Curves

The BEP is affected when the selected pump is oversized. The reason is that the flow of oversized pumps must be controlled with different methods, such as a throttle valve or a bypass line. These provide additional resistance by increasing friction. As a result, the system curve shifts to the left and intersects the pump curve at another point. The BEP is now also lower. In other words, the pump efficiency is reduced because the output flow is reduced but power consumption is not.

Inefficiencies of oversized pumps can be overcome by, for example, the installation of VSDs, two-speed drives, lower rpm, smaller impeller, or trimmed impeller

Controlling Flow: Speed variation

A centrifugal pump’s rotating impeller generates a head. The impeller’s peripheral velocity is directly related to shaft rotational speed. Therefore varying the rotational speed has a direct effect on the performance of the pump.

The pump performance parameters (flow rate, head, power) will change with varying rotating speeds. To safely control a pump at different speeds it is therefore important to understand the relationships between the two. The equations that explain these relationships are known as the “Pump Affinity Laws”:

  • Flow rate (Q) is proportional to the rotating speed (N)
  • Head (H) is proportional to the square of the rotating speed
  • Power (P) is proportional to the cube of the rotating speed

As can be seen from the above laws, doubling the rotating speed of the centrifugal pump will increase the power consumption by 8 times. Conversely, a small reduction in speed will result in a very large reduction in power consumption. This forms the basis for energy conservation in centrifugal pumps with varying flow requirements.

  • Controlling the pump speed is the most efficient way to control the flow because when the pump’s speed is reduced, the power consumption is also reduced.
  • The most commonly used method to reduce pump speed is Variable Speed Drive (VSD).
  • VSDs allow pump speed adjustments over a continuous range, avoiding the need to jump from speed to speed as with multiple-speed pumps. VSDs control pump speeds using two types of systems:
  • Mechanical VSDs include hydraulic clutches, fluid couplings, and adjustable belts and pulleys.
  • Electrical VSDs include eddy current clutches, wound-rotor motor controllers, and variable frequency drives (VFDs). VFDs are the most popular and adjust the electrical frequency of the power supplied to a motor to change the motor’s rotational speed.
  • The major advantages of VSD application in addition to energy-saving are:
  • Improved process control because VSDs can correct small variations in flow more quickly.
  • Improved system reliability because wear of pumps, bearings, and seals is reduced.
  • Reduction of capital & maintenance costs because control valves, by-pass lines, and conventional starters are no longer needed.
  • Soft starter capability: VSDs allow the motor to have a lower startup current.

Parallel Pumps for Varying Demand

Operating two or more pumps in parallel and turning some off when the demand is lower, can result in significant energy savings. Pumps providing different flow rates can be used.

Parallel pumps are an option when the static head is more than fifty percent of the total head.

The Fig. 5 shows

  • the pump curve for a single pump, two pumps operating in parallel, and three pumps operating in parallel.
  • that the system curve normally does not change by running pumps in parallel.
  • that flow rate is lower than the sum of the flow rates of the different pumps.

Eliminating Flow Control Valve

  • Another method to control the flow is by closing or opening the discharge valve (this is also known as “throttling” the valves).
  • While this method reduces the flow, its disadvantages are
    • It does not reduce the power consumed, as the total head (static head) increases. Fig. 6 shows how the system curve moves upwards and to the left when a discharge valve is half-closed.
    • increases vibration and corrosion and thereby increasing maintenance costs of pumps and potentially reducing their lifetimes
  • VSDs are a better solution from an energy efficiency perspective.

Eliminating By-pass Control

The flow can also be reduced by installing a bypass control system, in which the discharge of the pump is divided into two flows going into two separate pipelines. One of the pipelines delivers the fluid to the delivery point, while the second pipeline returns the fluid to the source. In other words, part of the fluid is pumped around for no reason, and thus is an energy wastage. This option should, therefore, be avoided.

Start / Stop Control of Pump

A simple and reasonable energy-efficient way to reduce the flow rate is by starting and stopping the pump, provided that this does not happen too frequently. An example where this option can be applied is when a pump is used to fill a storage tank from which the fluid flows to the process at a steady rate. In this system, controllers are installed at the minimum and maximum levels inside the tank to start and stop the pump. Some companies use this method also to avoid lowering the maximum demand (i.e. by pumping at non-peak hours).

Impeller Trimming

  • Changing the impeller diameter gives a proportional change in the impeller’s peripheral velocity
  • Changing the impeller diameter is an energy-efficient way to control the pump flow rate. However, for this option, the following should be considered:
  • This option cannot be used where varying flow patterns exist.
  • The impeller should not be trimmed more than 25% of the original impeller size, otherwise, it leads to vibration due to cavitation and therefore decrease the pump efficiency.
  • The balance of the pump has to be maintained, i.e. the impeller trimming should be the same on all sides.
  • Changing the impeller itself is a better option than trimming the impeller, but is also more expensive and sometimes the smaller impeller is too small.
  • Figure 6 illustrates the effect of impeller diameter reduction on centrifugal pump performance.
Centrifugal pump Performance
Fig. 6: Centrifugal pump Performance

Figure 6 illustrates the effect of impeller diameter reduction on centrifugal pump performance.

  • With the original impeller diameter, the flow is higher
  • With the trimmer impeller, the flow is lower
ParameterChange control valveTrim impellerVFD
Impeller diameter430 mm375 mm430 mm
Pump head71.7 m42 m34.5 m
Pump efficiency75.1%72.1%77%
Rate of flow80 m3/hr80 m3/hr80 m3/hr
Power consumed23.1 kW14 kW11.6 kW

The above table compares three options to improve energy efficiency in pumps:

  • changing the control valve, trim the impeller and variable frequency drive.
  • The VFD clearly reduces power most, but a disadvantage is the high costs of VFDs.
  • Changing the control valves should at all times be avoided because it reduces the flow but not the power consumption and may increase pump maintenance costs.

Few more Pump Related Resources for you..

Cause and Effect of Pump Cavitation
Major Factors Affecting the Pump Performance: An article
NPSH for Pumps: Explanation and Effect
Water Hammer Basics in Pumps for beginners
Mechanical Seals for Rotary Pumps

Emergency Response Procedures and Measures for Process Units

Written by Anup Kumar Dey in Piping Interface,Process

This article covers the design consideration of emergency response procedures and measures in petroleum refineries, chemical plants, and similar plants. This can be used in conjunction with the Job Specification, the client’s standards and intent, the licensor’s instructions, and related regulations. This article describes the emergency response design consideration of the following emergency measures.

Emergency Response Measure Pressure Relieving

Of the various measures for protecting a plant from the emergency situation, pressure-relieving through safety valves and rupture discs shall be examined first. This part will be covered in separate articles.

Isolation with Emergency Shut-off Valve

This section describes the installation standards of Emergency Shut-off (Block) Valves (ESV)used for isolating the equipment from the units in an emergency.

First, the following should be clarified with the client.

  • Client’s general philosophy for safety
  • Reliability for sensor(application of 2 out of 3 or not etc.)
  • Category of ESV (local, all shut down, etc.)
  • Inspection under operation (bypass or parallel installation)

The purpose of isolation by ESV is classified into the following.

  • Equipment Protection (Vessel, Tower)
  • Heat Off (Furnace, Steam supply)
  • Fluid or Seal gas Cut(Compressor, Pump), Leak Air Cut (Vacuum Pump)

Emergency Response Plan for Vessels

  • ESV is not always necessary to be provided on the Vessel outlet line.
  • If both the vessel volume of liquid and fluid condition meet the following requirements, ESV shall be provided on Vessel outlet lines.

 (a) Vessel volume-This limitation should be verified with project specifications.

  • Liquefied Petroleum Gas of more than 100 ton
  • Toxic liquid of more than 30 ton
  • SRC – More than 15 ton
  • EXOR – More than 20 m3

 (b) Fluid condition-

  • Liquid both flash point below 22.8°C and boiling point below 37.8°C
  • LPG, Naphtha, liquid with temperature more than auto ignition temp.

A control valve with a solenoid valve may be used as ESV if the following conditions are met:

  • It is not equipped with a minimum stop
  • It will close on the failure of the air supply or power failure.
  • A leak amount of CV is allowable.
  • The client’s approval is obtained 

Emergency Responses for Furnaces

  • Fuel lines to process furnaces and steam boilers shall be provided with remotely operated emergency valves.
  • In addition to the above, a manually operated block valve shall be provided in each fuel line. This includes the pilot gas supply line if it is a separate line. These valves shall be located at least 15 meters horizontally from the furnace or boiler protected.
  • ESV (Emergency shut-off valve) on the snuffing steam line shall be located at least 15 meters horizontally from the furnace and operable from grade.

Emergency responses for Steam Line to Reboiler

  • ESV will be installed on the steam inlet line to Reboiler especially in the case when the control valve is installed on the Reboiler outlet condensate line.

Emergency Measures for Compressors

  • ESV shall be provided in the suction and discharge lines of centrifugal compressors to prevent seal gas leakage.
  • (2) Other specifications for ESV installation are as below.
    • In case when Control Valve closing time is too slow. (Cost study is necessary)
    • A Balance line with ESV between suction and discharge may be requested by the client.

Emergency Response Plan for Pumps

  • ESV will be provided in the suction line of Pumps. (Treated as Vessel Outlet ESV)
  • ESV may be installed on the discharge line of high-head pumps to prevent backflow.

Emergency Response Guidelines: Vacuum Pumps

  • In the case of the NASH Pump, ESV will be installed on the suction line (process side) of Vacuum Pumps to prevent seal liquid from backflow into the process.

Emergency Measures: Depressurizing

When metal is exposed to fire, the metal temperatures may reach a level at which stress rupture could occur. The use of an emergency vapor depressurizing system is one method of avoiding such an occurrence.

Design Base of Vapor Depressurizing

The design base of vapor depressurizing is as follows. (Refer to API RP 520, 521)

  • Depressurizing Valve is of a remotely operated type.
  • Depressurizing initial pressure may be assumed up to design pressure.
  • The depressurized level should beat 7.0 kg/cm2 G or 50% of vessel design pressure, whichever is lower.
  • The duration time of depressurizing should be 15 minutes with a wall thickness of 25 mm, while vessels with thinner walls generally require a somewhat greater depressurizing rate.

Total Vapor Depressurizing Load:

The total vapor load will be obtained as the summation of the following.

  • Vapor generated from the liquid by heat input from a fire
  • Density change of the vapor in the equipment during pressure reduction, plus
  • Liquid flashing during pressure reduction

Design Consideration:

  • For the recycle compressor stoppage, settling out pressure should be investigated.
  • Excessive hot depressurizing gas should not be introduced to the flare header. Cooling should be provided in such a case.
  • As for the temperature effect due to hot depressurizing gas, it is not necessary to take it into account for the determination of the design temperature of each piece of equipment because of short-term conditions. However thermal stress checks of related piping should be necessary as required.
  • Regarding both pressure and flow rate change along with traveling time, the following tentative method may be available.
Relieving rate Calculation
Relieving Rate Calculation
  • The dynamic simulation should be carried out to confirm:
    • RO design for Depressurizing rate.
    • Reactor mechanical bed pressure checks during Depressurizing.
    • H/E with differential pressure design.
    • Mechanical damage for Compressor Seal Oil etc.
    • (NOTE) In the case of Manual Depressurizing with HCV, the above is not necessary.

Emergency Response Procedure: Alarm and Trip System

 (a) Alarm and trip signals are indicated on DCS or CCR panel. When the signal tells abnormal situations happened, it is expected that the operator takes appropriate countermeasure actions in accordance with the operating manual.

 (b) As for compressor and other package units, alarm and trip signals are indicated on the local panel. Only common alarm and trip signals are indicated on DCS or CCR panel. It is expected that the operator explores the cause of the failure at the local panel and takes appropriate actions in accordance with the operating manual.

 (c) Each ESD (Emergency Shut Down) shall be independent of the distributed control system (DCS) and may be activated either by plant transducers (eg. high pressure, low flow) or manually from CCR.

 (d) Typical set point for level alarm and level trip

  •  – High / Low alarms at 80% and 20% of the range
  •  – High / Low trips at 90% and 10% of the range

 A dedicated level switch is provided for the level trips.

 A minimum of 5 minutes will be available for the operator’s intervention after a high or low-level alarm is actuated and before gas breakthrough or liquid flooding takes place. Or an independent ESV is provided for the operator to initiate manually to close the outgoing flow. (to be confirmed by the process engineer)

 (e) Setpoint for temperature and pressure alarm and trip.

 – As specific to the project, contents shall be individually investigated and clarified.

Emergency Response Procedure: Failures & Trips

The failures for units and equipment, as also trip actions are summarized under the following categories.

  • Furnaces
  • Pumps including Hydraulic Power Recovery Turbine
  • Compressors

The trip sequence is summarized on the PID. It is necessary, however, to prepare the sequence logic diagram at the same time. Also, it is desirable to explain the outline of the trip sequence in the operation manual. Typical TRIP SEQUENCE is as follows.

Trip Sequence
Trip Sequence

Motion Amplification Technology (MAT) for Piping Vibration Visualization

Written by Anup Kumar Dey in Mechanical,Piping Design Basics,Piping Stress Analysis,Piping Stress Basics

Iris M from RDI technologies is the first device of its kind that allows users to see – in real-time – the motion that is unseen to the human eye. This patented Motion Amplification Technique lets you see the invisible.

Iris M is a unique, revolutionary technology that detects subtle motion and amplifies that motion to a level visible to the naked eye. By turning every pixel in the camera into a sensor, Iris M takes millions of measurements in a fraction of a second with no physical connection to the machinery or equipment. Motion Amplification™ is a proprietary video processing algorithm that detects subtle movement and then converts that movement to a level visible to the naked eye which enhances the understanding of the components and interrelationships creating the motion.

In a typical traditional data acquisition process, we have to fix the sensors at predefined locations on the machinery or equipment. The data collection is non-simultaneous and prepares a report with a detailed explanation or exception list with spectra and waveforms.

In this revolutionary technology – Iris M, data are collected by a high-speed machine-grade camera in the form of standard video. It measures the movement not visible to the naked eye by turning each pixel into a sensor that measures vibration and motion. It used patented methods and processing algorithms to extract meaningful data. The data is simultaneous and gives a report with detailed displacement and frequency spectrums.

Iris M Platform monitors critical manufacturing operations, processes, quality, piping, and structural components that affect plant reliability and productivity. It is a perfect tool for screening, fault finding, baseline or commissioning, and pre/post repairs or retrofits.

Benefits of Motion Amplifications

  • Improved Safety: Totally non-contact
  • Reduce unplanned downtime: Know what your “Bad Actors” are doing
  • Complimentary Tool
  • Diverse applications – Machines, Structures, Processes, Piping, Visual ODS
  • Setup & acquire data in minutes, easy to deploy, use often as a troubleshooting tool
  • Actionable information: Results are easy to see in a standard video
  • Communications with facility resources are enhanced

The World’s First Non-Contact Motion Amplification Platform – Iris M

Motion Amplification Technology
Motion Amplification Technology

What is a Thermowell? Types of Thermowell

Written by Anup Kumar Dey in Instrumentation,Piping Design Basics,Piping Interface

What is a Thermowell?

Thermowells are cylindrical pressure-tight fittings used to protect the temperature sensors such as thermocouples, thermistors, and bimetal thermometers which are inserted into a pipe or vessel in industrial applications. A thermowell is basically a tube closed at one end and mounted in the process stream. The thermowell acts as a barrier between the sensing element and the process medium. It protects the sensing element against corrosive process media and fluid pressure and velocity.

Thermowells also increase the sensor longevity, allow sensor replacement without draining the system and eliminate the probability of contamination. Thermowells are designed for both high and low-pressure applications.

Thermowells find wide applications in many industrial sectors including refining, cosmetics, petrochemical, food processing, chemicals, Power, pharmaceutical, and other process industries.

Importance of Thermowells

Thermowells play a crucial role in the successful measurement of temperature in industrial processes.

  • They Protect the sensor.
  • Thermowells ensure that process temperature is passed to the sensor (proper heat transfer).
  • Improved heat transfer, results in better accuracy.
  • Allow the removal of the sensing element while maintaining a closed system.

Types of thermowell

Thermowells in the piping industry can be classified based on various parameters as listed below:

Depending on the stem design shape, four types of thermowell are available:

  • Straight Thermowell
  • Stepped thermowell
  • Tapered Thermowell, and
  • Built-up thermowells

Straight Thermowell

Straight thermowell has the same diameter for the entire insertion length. They are simple to fabricate and possess good rigidity and offer protection against corrosion and erosion.

Stepped Thermowell

Stepped thermowell have stepped diameters; Normally at the tip, they have a smaller (typically 1/2″) diameter while a larger diameter (Typically 3/4″) at the top. Due to decreased thermal inertia at the process end, these thermowells allow smoother velocities and respond more rapidly to temperature changes than their straight counterparts.

Tapered Thermowell

The tapered thermowell has varying diameters (smooth continuous taper) over its full insertion length. Tapered thermowell is suitable for high-velocity heavy-duty applications and possesses a fast response time.

Built-up Thermowell

Built-up thermowells are suitable for very long process insertion lengths. They are available in all the above types but a length of pipe is welded between the tip and process connection to give the long insertion length.

Types of Thermowells
Fig. 1: Types of Thermowells

Depending on material types, Two types of Thermowells can be found:

  • Pipe Fabricated.
  • Bar stock thermowells.

Depending on thermowell end connections, five types of thermowells are available. they are

  • Threaded thermowells
  • Weld-In thermowells
  • Socket Weld thermowells
  • Van Stone or Lap Joint flanged thermowells
  • Flanged thermowells

Threaded Thermowell

The threaded type thermowell is generally the least costly and most versatile. Threaded thermowells are normally used for non-corrosive applications. They are screwed into the pipe. Their material is such that it can be welded or brazed to provide additional strength.

Weld-in Thermowell

Weld-in thermowell connections are preferred for food and pharmaceutical industries where contaminants from threads must be avoided.

Socket Weld Thermowell

Socket Weld Thermowells are directly welded into the pipe. Its strong connection helps these thermowells to use as a permanent connection. Applications involving very high temperature and pressure use socket-welded thermowell connections.

Van Stone Thermowell

For high-pressure applications, the Van Stone thermowell is ideal. They are usually machined from a solid bar and are placed in a sandwich position between the nozzle and cover flange. Vanstone flange surface is with a phonographic spiral serration.

Flanged Thermowell

A flanged thermowell is designed with a flange at the top end. This type of thermowell is connected to the pipe using nuts and bolts. Flanged thermowell connections are mostly used in high-temperature applications that require frequent replacements.

Flanged thermowells are used in a wide range of industrial applications where temperature measurement is critical. The flange design allows for easy installation and removal of the thermowell without interrupting the process or requiring any special tools.

Some common applications of flanged thermowells include:

  • Chemical processing: Flanged thermowells are used to measure the temperature of various chemicals in reactors, vessels, and pipelines.
  • Oil and gas: Flanged thermowells are used in oil refineries, pipelines, and gas processing plants to measure the temperature of crude oil, natural gas, and other hydrocarbons.
  • Food and beverage: Flanged thermowells are used in food and beverage processing plants to measure the temperature of liquids, such as milk, beer, and juice.
  • HVAC: Flanged thermowells are used in heating, ventilation, and air conditioning (HVAC) systems to measure the temperature of air and water.
  • Power generation: Flanged thermowells are used in power plants to measure the temperature of steam and other fluids used in power generation.
  • Pharmaceutical: Flanged thermowells are used in pharmaceutical manufacturing processes to measure the temperature of various chemicals, drugs, and biological products.

Overall, flanged thermowells are used in any process where temperature measurement is critical and the protection of the temperature sensor is required from harsh process conditions.

There are two other types of thermowell connections; Scruton thermowell and Sanitary thermowell.

Scruton Thermowell

To avoid damages that can be caused due to the mechanical load and critical condition of the process, the Scruton thermowell is designed. They save time and cost on re-work at the site.

Sanitary Thermowell

A sanitary thermowell is used for isolation and protection of the sensing element of any temperature instrument. To avoid bacterial build-up, Sanitary thermowells are built with hygienic connection.

Thermowell types based on End Connection
Fig. 2: Thermowell types based on End Connection

Materials of Thermowells

The right material increases the longevity of a thermowell. Material selection of thermowell will depend on the chemical, temperature, and flow rate of the process fluid. With an increase in temperature and fluid concentration, the corrosive effects of chemicals normally increase. At the same time, suspended particles of the fluid will cause erosion. So all these parameters need to be addressed while selecting thermowell material. Some of the most frequently used thermowell materials are listed below:

  • Carbon Steel
  • Brass
  • SS 316 / SS 304
  • SS316 with Teflon / Zirconium Coated or Tantalum / Titanium steathing.
  • Graphite
  • Chromium/molybdenum steels
  • Incoloy
  • Inconel
  • Monel
  • Hastelloy
  • Haynes Alloy
  • Titanium
  • Aluminum

However, the most widely used thermowell material is stainless steel as it is cost-effective and highly resistant to heat and corrosion. For pressurized vessels, Chromium/molybdenum steel is used. Cobalt, nickel, chromium, and tungsten constitute the Haynes alloy that is widely used for sulphidising, carburizing, and chlorine-containing environments. The use of carbon steel thermowell is only limited to low-temperature pressure applications due to its very low resistance to corrosion.

Thermowell Insertion Length

The length from the connection point to the thermowell tip is known as the insertion length of the thermowell (U dimension in Fig. 4). For better accuracy, the thermowell insertion length should be long enough. This will allow the entire temperature-sensitive portion of the measurement device to extend into the medium being measured.

For measuring the liquid temperatures using a temperature sensor, the device must be extended into the solution for the length of the temperature-sensitive portion plus a minimum of one inch (25 mm). For gaseous or air service, it should be immersed for the length of the temperature-sensitive segment plus an additional three inches. The temperature-sensitive section of a thermocouple or thermistor is short; therefore, the insertion length of the thermowell can be shorter for these devices. Whereas, the temperature-sensitive section of bimetal thermometers, RTDs, and liquid in glass thermometers is between 1″ and 2″ hence, the thermowells must be immersed at least 2½” in liquid for accurate measurements.

Thermowell Installation

Lagging is used when the thermowell is installed through an insulation media on a pipeline or equipment.

Fig. 1: Examples of Thermowells
Fig. 3: Examples of Thermowells

An improperly specified thermowells, will result in:

  • Failure due to poor welding practices.
  • Poor compatibility with the temperature and media.
  • Inadequate temperature transfer.
  • Incompatibility with the process velocity leads to failure due to vibration.
  • The gap between the OD of the thermocouple sheath and the ID of the thermowell must be very close.
  • The bore of the thermowell must be uniform and linear.

Design of Thermowells

  • The design of the thermowell should cater to process media, pressures, temperatures, velocity, specific gravity, etc.
  • Proper MOC (Material of construction).
  • Wall thickness Vs response time.
  • Bore diameter, Insertion length, Taper requirements, Overall length, etc.
  • Vortex shedding
  • Calculate the Vibration using Wake Frequency methods.
Details of Thermowell
Fig. 4: Details of Thermowell
Various dimensions of Thermowells.
Fig. 5: Various dimensions of Thermowells.

Thermowell Installation Requirements

Refer to Fig. 6 and Fig. 7

Requirements during installation
Fig. 6: Requirements during installation
Installation Requirements
Fig. 7: Installation Requirements

Selection of a Thermowell

The key parameters to consider while selecting a thermowell are:

  • Process connection size and type.
  • Process insertion length
  • Lagging length
  • Extension length
  • Sensor length
  • Interior diameter (bore) for the sensor or thermometer
  • Internal threads for the sensor or thermometer
  • The shape of the thermowell (straight, stepped, tapered, built-up)
  • Material of construction

Thermowell Design Code

Piping Designers follow ASME PTC 19.3 for guidelines regarding thermowells.

Thermowell Working Principle

The working principle of a thermowell is based on the concept of thermal conductivity, where heat flows from a region of high temperature to a region of low temperature. A thermowell is a protective casing that is used to house a temperature sensor, such as a thermocouple or a resistance temperature detector (RTD). The thermowell is inserted into the process being measured, and the temperature sensor measures the temperature of the process fluid or environment.

The thermowell is designed to protect the temperature sensor from harsh process conditions, such as high pressure, high temperature, and corrosive fluids. The thermowell is typically made of durable material, such as stainless steel or ceramic, and has a closed end that protects the temperature sensor from direct contact with the process fluid. The thermowell also has an opening that allows the temperature sensor to come in contact with the process fluid and measure the temperature.

The thermowell works by allowing the heat from the process fluid to flow through the wall of the thermowell and come into contact with the temperature sensor. The thermal conductivity of the thermowell material is chosen such that it allows for efficient heat transfer while also providing adequate protection for the temperature sensor. The thermowell also serves to isolate the temperature sensor from the process fluid, allowing for accurate temperature measurement even in harsh process conditions.

Overall, the thermowell working principle is based on the concept of thermal conductivity, where the thermowell material allows for efficient heat transfer while protecting the temperature sensor from harsh process conditions.

Thermowell Vibrations

As thermowells are immersed in the process flow, a bending force will be experienced by them. Additionally, depending on the fluid velocity and thermowell diameter, a certain vibrational frequency will be generated leading to thermowell vibration. In general, such vibrations are of small magnitude and considered negligible. But, the thermowell must have sufficient stiffness and rigidity to absorb those vibrations. In such a scenario, tapered thermowells are preferred as they have more stiffness. However, if the generated frequency approaches the natural frequency of the thermowell, it can cause severe unacceptable vibrations. ASME PTC 19.3 provides formulas to determine if a thermowell is acceptable for a given application. Many thermowell manufacturers have generated a velocity rating table that recommends the maximum fluid velocity for their thermowells to avoid resonance.

Wake frequency calculation following the guidelines of ASME PTC 19.3 standard is performed to prove that the thermowell has the strength to handle hydrostatic pressure limit and dynamic static stress in relation to process conditions. Prior to the manufacturing of thermowell, these types of calculations ensure that the thermowells can cope with the stress and strain produced by any kind of process media.

Information required for Purchasing Thermowell

The following information must be supplied to the thermowell manufacturer/vendor while placing an order.

  • Process Connection Size
  • Thermowell Insertion Length
  • Lagging extension
  • Shank configuration
  • Process Connection type
  • Nominal Bore
  • Thermowell Material
  • Process Design temperature and pressure

Disadvantages of Thermowell

The main disadvantages of a thermowell are:

  • Compared to a naked sensor, slightly slower response to temperature changes.
  • Resistance to flow medium.
  • Increased cost for purchasing a thermowell.

Differences between a Thermowell and a Thermocouple: Thermowell vs Thermocouple

A thermowell and a thermocouple are both used for temperature measurement, but they are different in their design, function, and application. Here are some of the main differences between the two:

  • Design: A thermowell is a protective tube that is inserted into a process or fluid to provide a barrier between the sensor and the environment. A thermocouple, on the other hand, is a sensor that measures temperature by generating a small voltage in response to a temperature difference.
  • Function: The purpose of a thermowell is to protect the temperature sensor, usually a thermometer or a thermocouple, from damage or corrosion in harsh environments, high pressures, or high-velocity fluid flows. The thermowell provides a barrier between the sensor and the environment while allowing the sensor to detect the temperature of the process fluid. A thermocouple, on the other hand, is a sensor that directly measures temperature by generating a voltage in response to a temperature difference.
  • Application: Thermowells are typically used in process industries such as oil and gas, chemical processing, and food and beverage production. They are often used to protect temperature sensors that are installed in pipelines, tanks, and vessels. Thermocouples, on the other hand, can be used in a wide range of applications, including temperature monitoring in HVAC systems, laboratory equipment, and industrial processes.

In summary, a thermowell is a protective barrier that surrounds a temperature sensor, while a thermocouple is a temperature sensor that directly measures temperature. They have different functions and applications but can both be used for temperature measurement in various industries and applications.

Thermowell Probe

A thermowell probe is a temperature measurement device that consists of a temperature sensor, such as a thermocouple or a resistance temperature detector (RTD), housed inside a protective tube called a thermowell. The thermowell is typically made of metal and is inserted into a process or fluid, providing a barrier between the temperature sensor and the environment. The thermowell is designed to protect the temperature sensor from damage or corrosion caused by harsh process conditions such as high temperatures, high pressures, and corrosive fluids.

The thermowell probe allows temperature measurement without directly exposing the temperature sensor to the process fluid or environment. The thermowell can be removed and replaced if necessary without affecting the process or equipment, making it a useful tool in many industries, including chemical, oil and gas, and food and beverage production. The selection of a thermowell probe depends on factors such as the process conditions, the type of temperature sensor used, and the required accuracy and response time.

Thermowell Temperature Sensor

A thermowell temperature sensor is a device that measures temperature using a thermowell as a protective barrier between the temperature sensor and the process fluid or environment. The temperature sensor can be a thermocouple or a resistance temperature detector (RTD) and is typically housed inside the thermowell, which is inserted into the process or fluid being measured. The thermowell protects the temperature sensor from damage caused by harsh process conditions such as high temperatures, high pressures, and corrosive fluids.

The thermowell temperature sensor is commonly used in industries such as chemical processing, oil and gas, and food and beverage production, where accurate temperature measurement is essential for maintaining the quality and safety of products and processes. The thermowell temperature sensor can be installed directly into pipelines, tanks, and vessels, allowing temperature measurement of liquids, gases, and solids. The thermowell can be designed to meet various requirements, such as high temperature and pressure ratings, different materials of construction, and various process connections. The selection of a thermowell temperature sensor depends on factors such as the process conditions, the type of temperature sensor used, and the required accuracy and response time.

Rack Piping for a Piping Stress Engineer

Written by Anup Kumar Dey in Piping Design Basics,Piping Stress Analysis,Piping Stress Basics

A pipe rack is a very important part of process piping. A Pipe Rack can be defined as a steel-framed structure that supports and carry pipes inside the processing plant and transfer the fluid between equipment and storage facilities or utility areas.

While designing a pipe rack, there are two main factors into which a stress engineer should look at details. Those are

  1. Expansion loop design and placement and
  2. Pipe rack loading to Civil for the rack design.

The following write-up will list the considerations while designing the pipe loop and rack loading.  

A typical Pipe rack in a Process Plant
Fig. 1: A typical Pipe rack in a Process Plant

Expansion Loop design and placement

In most organizations, there are no defined criteria for designing and placing an expansion loop in a pipe rack. So most of the time the expansion loop is designed and located based on user experience. The important parameters which govern the design of the expansion loop are listed below:  

  •  A. Design/Maximum operating temperature of the line
  • B. Allowed Displacement or movement (Normally allowed thermal displacement is 250-300 mm inside a loop and 75-100 mm in outside turns)
  • C. Allowed Expansion stress (normally within 80% of code allowable)
  • D. Line size (Bigger sizes require more leg to absorb expansion)
  • E. Loop Supporting Requirements (locations at which the loop will be supported)
  • F. Fluid type (Normally Flare and condensate lines require a 2D loop)
  • G. Line sagging criteria from Project specification (Sometimes Steam, Condensate, Two-Phase flow lines, and Flare lines require sagging limited within 3-5 mm for others it can go up to 15 mm)
  • H. Rack length and width    

After having the above-mentioned parameters ready one can proceed to locate the loops over the rack. Follow the below-mentioned steps as a preliminary guideline:  

a. Select an elevation of the pipe rack and check what the lines running over that rack.

b. Select the line with maximum temperature first. Check the allowed maximum movement outside loop (say 75 mm) and place the first anchor at a distance that will be nearer to the allowed thermal movement (75 mm) as mentioned above.

c. Now as one anchor is fixed one can easily calculate the thermal displacement at design temperature towards the other end/turn. If the displacement is within the allowed displacement (75mm) then an expansion loop is not required. But if the calculated displacement is more (>75mm) then the expansion loop is required. From this displacement, you can decide how many expansion loops are required for the straight run allowing a maximum of 250-30 0mm displacement inside the loop. (Care should be taken for expansion leg requirement as sometimes allowing 300 mm displacement may cause expansion failure or huge anchor load. In that case, increase the number of expansion loops.)

d. It is better to place lines with high temperatures outside of the rack so that a longer loop length can be achieved on the other side.

e. It is better to nest the loops in a single location (the same structures can be utilized for supporting)

f. Don’t mix lines that required 2D loops with lines that required a 3D loop in the same elevation.

g. It is better to place anchors in similar locations for deciding anchor bay.

Typical Expansion Loop
Fig. 2: Typical Expansion Loop

Pipe Rack Loading  

Rack loading is provided to CSA for the economic design of the pipe rack. Providing pipe rack loading is a very difficult task for a stress engineer as most of organizations do not have any guidelines. Normally Pipe rack loads are transferred in 3 stages:    

  • a. Initial rack loading for rack foundation design (before piling): The project has just started and very little data is available. The piping design places the lines over the rack based on preliminary P&ID. Rack loads are provided mostly based on assumption/experience. Conservative loads are to be provided.
  • b. Rack loading for member sizing (after 30% model review): Most of the data has started arriving. Loads are to be provided based on actual analysis.
  • c. Rack loading for final member checking (after 60% model review): All vendors are decided. Line size and locations are finalized. All critical lines are fixed. Loads are provided for checking designed members again. Loads are to be provided based on Software analysis.

Few points to keep in mind while providing Rack loading:

  • 1. Operating, Water filled, and Occasional loads for big-size lines (> 16-inch NPS) are to be provided separately. For guides and anchors, loads with and without friction should be provided.
  • 2. For the Flare line 1/3rd water-filled weight can be considered.
  • 3. Proper directions to be marked.
  • 4. After the long run doesn’t provide a guide in the immediate first possible location after the bend.
  • 5. Consider concentrated loads of inline valves, flanges, equipment, etc.
  • 6. Sometimes large equipment is placed over the pipe racks (Air Fin Fan Cooler, Heat Exchangers, etc). So take the operating weight of equipment from the mechanical group.
  • 7. Cable tray loads are to be taken from the electrical/instrumentation group. (In absence of data a uniformly distributed load of 1.0 KPa for a single level and 1.9 KPa for a double level of cable trays can be considered)
  • 8. Include the forces of PSV reactions if applicable.  

In the absence of data, the following guidelines can be used as preliminary piping loads:

  • a. A uniformly distributed load of 1.9 KPa for piping, product, and insulation can be considered for line size (for each line)
  • b. For line size larger than 12-inch nominal diameter actual concentrated load including the weight of piping, product, valves, fittings, and insulation shall be used.  

Click here to know about the Pipe rack layout design considerations.

Piping Insulation: Functions, Materials, and Types of Pipe Insulation

Written by Anup Kumar Dey in Mechanical,Piping Design Basics,Piping Interface,Piping Stress Analysis

Piping insulation is a crucial aspect of any industrial, commercial, or residential piping system. It serves multiple purposes, from conserving energy and reducing heat loss to preventing condensation and protecting pipes from extreme temperatures. The choice of insulation material is critical and depends on several factors, including the operating temperature of the pipes, environmental conditions, and specific industry requirements. In this article, we’ll try to provide in-depth knowledge about all aspects of piping insulation.

Pipe Insulations are materials or combinations of materials wrapped around the pipe which retard the flow of heat energy. Pipe insulation reduces energy losses to a great extent and thereby reduces the energy cost. Piping shall be insulated as per the insulation class, operating temperature, and insulation thickness stated in the P&ID.

Functions of Pipe Insulation | Why is Piping Insulation Important?

A piping insulation system serves three principal purposes:  

  1. The significant reduction in heat transfer of thermal energy to and from the surface of the piping system (Heat Conservation). So, piping insulation conserves energy and improves system efficiency.
  2. The prevention of moisture formation and collection on the surface of the piping system due to condensation on cold surfaces (Cold Insulation).
  3. The prevention of potentially injurious personnel contact with the surface of the exposed piping system (Personal Protection).

However, there are various other benefits of piping insulation as listed below

  • Piping insulation facilitates temperature control of the process.
  • Prevent vapor flow and water condensation on cold surfaces.
  • Increase the operating efficiency of heating/cooling, power, and process systems.
  • Reduce major damages in the piping during fire or accidents.
  • Prevent pollutant emissions to the atmosphere to a great extent.
  • In colder climates, insulation prevents water in pipes from freezing, which can cause bursting and significant damage.
  • Sometimes Steam traced/Electric traced insulation, Regeneration insulation, jacketing, etc. are used as per process/licensor requirements.
  • Some insulation materials can dampen sound, reducing noise levels in a facility.
  • Fireproofing, fire protection, and acoustic insulation (to control noise and absorb vibration) are provided based on project specifications/ ITB requirements.
Hot and Cold Pipe Insulation
Fig. 1: Hot and Cold Pipe Insulation

Pipe Insulation Types

Piping insulation can be classified based on various parameters like

  • Based on the Pipe Insulation Function
    • Hot Insulation
    • Cold Insulation
    • Personal Protection Insulation
    • Acoustic Insulation
  • Based on Insulation Material Types
    • Fibrous Insulation
    • Cellular Insulation
    • Granular Insulation

Piping Insulation Types Based on the Function of Pipe Insulation

Hot Insulation

Hot insulation is applied on the hot surfaces of the piping system to prevent the energy flow from flowing fluid. So, the main aim of hot piping insulation is heat conservation. Mineral Wool, Glass Wool, Calcium Silicate, etc. are normally used as Hot insulating material. Hot Piping Insulation is typically applied for process temperatures above 60°C.

Cold Insulation

Cold Insulation is the insulation used on cold surfaces of the piping system to avoid heat gain from outside (Cold Conservation) or to avoid Condensation. Polyurethane Foam, Expanded Perlite Foam, Expanded Polystyrene Foam, etc. are the widely used cold insulating materials.

Personal Protection Insulation

Personal Protection insulation is provided to avoid personal heat injury. All exposed piping surfaces that exceed 60 degrees C are provided with personal protection insulation. The areas that are not accessible by construction or operating personnel can be left exposed. An open mesh metal guard (Fig. 2), mineral wool, etc. are used as personal protection insulation material.

The criteria for personal protection is that the exposed surfaces located within 600 mm horizontally or 2100 mm vertically of a normal access, walkway, or work area are to be insulated.

Acoustic insulation

Acoustic Insulation is provided for all piping that is considered a potential sound source. The main purpose is to reduce the noise (vibration) to an acceptable limit. The minimum thickness for acoustic insulation is normally 75 mm. Acoustic Foam, fiberglass, polyester/polyurethane foams, rock wool, Mass Loaded Vinyl, etc. are used as Acoustic Insulating material.

Personal Protection Insulation in Operating Plant
Fig. 2: Personal Protection Insulation in Operating Plant

Piping Insulation Types based on insulation material types

Fibrous Insulation

Fibrous insulation consists of small diameter fibers which finely divide the air space. The fibers may be perpendicular or parallel to the surface being insulated, and they may or may not be bonded together.

Common fibers used in piping insulation are Silica, slag wool, rock wool, and alumina-silica. Among these, Glass fiber and Mineral Wool are the two most widely used piping insulations of this type. Their fibers are normally bonded with organic binders for structural integrity.

Cellular Insulation

Cellular pipe insulation material comprises small individual cells separated from each other. Common cellular materials used as pipe insulation are glass or foamed plastics such as cellular glass, phenolic foam, or nitrile rubber.

Typical Piping Insulation for Bends
Fig. 3: Typical Piping Insulation for Bends

Granular Insulation

Small nodules containing voids or hollow spaces constitute granular insulation. As gas can be transferred between the individual spaces, It is not considered a true cellular material. This type is manufactured as loose or pourable material or combined with a binder and fibers. Sometimes they undergo a chemical reaction to form rigid insulation. Calcium silicate and vermiculite are examples of these types of insulations.

Pipe Insulation Material

  • Low-temperature insulation is frequently made of expanded cellular plastic or foam rubber material.
  • Moderate temperature insulations are made from grass fiber products.
  • High-temperature insulation is made of preformed cementations or refractory materials or blankets made from ceramic fibers.
  • Insulation and accessory materials have to be 100% asbestos-free.
  • Normally mineral fiber, cellular glass, ceramic fiber, glass fiber, polyisocyanurate, polyurethane foam, Rockwool, Glass Wool, Expanded Perlite, Flexible Elastomeric Foam (FEF), Flexible aerogel blanket, Calcium magnesium silicate wool (CMS), Alkaline earth silicate wool (AES), Calcium Silicate, etc. are used as pipe insulation material.

The following table provides details of some commonly used insulation materials:

Pipe Insulation MaterialDensity (kg/m3)Temperature Limitation
Mineral Glass Fibre up to 535°C
Mineral Wool140up to 700°C
Rock Wool140up to 550°C
Glass Wool80up to 450°C
Calcium Silicate200-280up to 815°C
Expanded Perlite192up to 550°C
Expanded Silica up to 535°C
Refractory Fiber150up to 1750°C
Polyurethane Foam40from -150°C to 110°C
Polyisocyanurate40-64from -150°C to 125°C
Cellular Glass147up to 350°C
Ceramic Fibre250up to 760°C
Table 1: Pipe Insulation Material Table

Some Typical Pipe Insulation materials are described below:

  • Fiberglass Insulation: Fiberglass is one of the most common and widely used insulation materials. It is made from fine glass fibers and is available in pre-formed sections, blankets, or wraps.
  • Mineral Wool (Rockwool) Insulation: Mineral wool, also known as rockwool or slag wool, is made from molten rock or industrial waste products spun into fibers. It is known for its excellent fire-resistant properties. It can withstand temperatures up to 700°C.
  • Cellular Glass Insulation: Cellular glass insulation is made from crushed glass that is heat-treated to create a closed-cell structure. This material is highly resistant to moisture and chemicals. ASTM C552 gives the Standard Specification for Cellular Glass Thermal Insulation.
  • Foam Glass Insulation: Foam glass is another form of cellular glass insulation but is produced using a different process that results in a lighter, more flexible material.
  • Polyurethane Foam (PUR) Insulation: Polyurethane foam is a versatile insulation material known for its low thermal conductivity and high resistance to water. It is available as spray foam or pre-formed sections. It can operate effectively between -150°C to 110°C.
  • Elastomeric Foam Insulation: Elastomeric foam insulation is a flexible, closed-cell material made from synthetic rubber. It is particularly effective in preventing condensation on cold pipes.
  • Calcium Silicate Insulation: Calcium silicate is a high-temperature insulation material made from lime and silica. It is widely used in industrial applications due to its durability and thermal stability. It is effective up to 815°C. ASTM C533 provides the Standard Specification for Calcium Silicate Block and Pipe Thermal Insulation.
  • Aerogel Insulation: Aerogel is a cutting-edge insulation material known for its ultra-low thermal conductivity. It is one of the lightest solid materials available and offers superior insulation performance. Its effective temperature range is from -268°C to 650°C.

Piping Insulation System

The main part of the Piping insulation system is the insulating material. Other elements that constitute the pipe insulation system are

  • Protective Coating
  • Vapor Barrier
  • The cladding of the metallic sheet.
  • Spacers to enable cladding to retain its shape.
  • Packing to fill the cavities or voids, if any.

Pipe Insulation Forms

Insulations are manufactured in a variety of forms to suit specific applications and functions. The installation method is decided by the combined insulation form and type of insulation. The most widely used insulation forms are:

  • Rigid boards, sheets, blocks, and pre-formed shapes: Cellular, granular, and fibrous insulations are produced in these forms.
  • Flexible sheets and pre-formed shapes: Cellular and fibrous insulations are produced in these forms.
  • Flexible blankets: Fibrous insulations are produced in flexible blankets.
  • Cement (insulating and finishing): Produced from fibrous and granular insulations and cement, they may be of the hydraulic setting or airdrying type.
  • Foams: Poured or froth foam used to fill irregular areas and voids. The spray is used for flat surfaces.
Mineral Wool Piping Insulation
Fig. 4: Mineral Wool Piping Insulation

Normally, Rock and Glasswool are pre-formed in two halves; Polyisocyanurate, Polyurethane, and Cellular Glass are supplied in preformed cylindrical shapes to slit in half lengthwise, and ceramic fiber is supplied in blanket strips.

Piping Insulation Standards

The following codes and standards provide guidelines for industrial piping insulation:

  • ASTM C533, ASTM C547, ASTM C552, ASTM C591, ASTM C592, ASTM C610, ASTM C612, ASTM C795, ASTM C892, ASTM C165, ASTM C240, ASTM C302, ASTM C303, ASTM C335, ASTM C356, ASTM C390, ASTM C446, ASTM C680.
  • BS 1902 Part 6, BS 4370 Part 2, BS 5608
  • IS 11239, IS 12436, IS 9428, IS 8183, IS 4671, IS 3690
  • ISO 15665- Acoustic Piping Insulation
  • EN ISO 23993

Factors Affecting Piping Insulation Performance

For any specific application, the main factors that impact the relative performance of various pipe insulation are:

  • Pipe Insulation thickness
  • Thermal conductivity (“k” or “λ” value) of Insulation Material
  • Surface emissivity value or “ε” value
  • Water-vapor resistance (“μ” value)
  • Density of the insulating material
  • Level of moisture content
  • Opening of Joints

Piping Insulation Thickness Calculation

Click here for details regarding pipe insulation thickness calculation and more details about hot and cold thermal insulation.

Insulated and Non-insulated piping in Operating plant
Fig. 5: Insulated and Non-insulated piping in the Operating plant

Piping Insulation System Design Considerations

Some important design considerations related to piping insulation (May vary from project to project):

  • All insulating materials need to be free from harmful products affecting human health and the environment. To be more specific, the piping insulation material needs to be free from known carcinogens, asbestos, Chlorofluorocarbon (CFCs), Hydrochlorofluorocarbon (HCFCs), heavy metals such as lead or cadmium, and PCBs.
  • Insulation thickness is determined based on pipe size, normal operating temperature,  temperature controlling requirement (extent of heat loss/gain), etc. At a minimum 25 mm pipe insulation thickness is to be used.
  • If the insulation thickness is more than 75 mm then insulation is provided in two or more layers (multi-layer).
  • Insulation shall not be applied until hydrostatic/ pneumatic testing is performed.
  • Insulation up to 12-inch NPS pipe shall be held with SS-304 tie wire and for > 12-inch NPS SS-304 bands are used.
  • All flanges will be insulated other than hydrogen service or high health hazard material services.
  • All valves other than control valves and relief valves shall be insulated.
  • Certain piping items like vents, steam-out and snuffing steam systems, flare and blow-down systems; Piping supports; Steam Traps; Expansion joints, hinged joints and hose assemblies; Instrument connections; Sight flow indicators, etc. are usually not insulated.
  • Each pipe must be insulated separately except where the second pipe is for heat tracing.

Piping Insulation Thickness Chart

A piping insulation thickness chart is a reference chart for piping engineers, designers, and insulation installers when determining the appropriate insulation thickness for various piping systems. The insulation charts are made by economic pipe insulation thickness calculation and presented in a tabular format for easy reference. The piping insulation thickness chart typically includes information on pipe insulation thickness corresponding to the operating temperature range and pipe sizes. A separate table for each type of piping insulation (Hot, cold, or personal protection) is prepared.

The following Image (Fig. 6) shows a typical pipe insulation thickness chart for Heat Conservation Insulation. Note that the image only provides a sample reference for the piping insulation thickness chart, for actual values you must refer to your project-specific data.

Pipe Insulation Thickness Chart for Hot Insulation
Fig. 6: Typical Pipe Insulation Thickness Chart for Hot Insulation

Choosing the right type of piping insulation depends on various factors, including the temperature range of the system, environmental conditions, and specific industry requirements. Proper installation and maintenance of insulation are also crucial to achieving the desired performance.

Frequently Asked Questions: Piping Insulation

How does pipe insulation work?

Pipe insulation works by creating a barrier that reduces the transfer of heat between the pipe and its surroundings. This barrier minimizes heat loss in hot pipes and prevents heat gain in cold pipes. Additionally, insulation prevents condensation on cold pipes and provides a layer of protection against extreme temperatures, which can prevent freezing or overheating.

How thick should pipe insulation be?

The thickness of pipe insulation depends on several factors, including the temperature of the fluid inside the pipe, the ambient temperature, and the type of insulation material used. For most applications, insulation thickness ranges from 1/2 inch to 2 inches. Higher temperatures or more extreme environments may require thicker insulation for optimal performance. The thickness of piping insulation is calculated during the detailed design phase of a project as explained here.

How do I select the right pipe insulation?

Selecting the right pipe insulation involves considering several factors:

  • Temperature Range: Ensure the insulation can handle the operating temperature of your system.
  • Moisture Resistance: If the pipes are exposed to moisture or humid environments, choose insulation with good moisture resistance.
  • Fire Resistance: For high-temperature or fire-rated systems, select a material with excellent fire resistance.
  • Cost and Availability: Consider the cost and availability of the insulation material.
  • Specific Application: Different environments and applications may require specialized insulation types, such as cryogenic systems or underground piping.

What is the best insulation material for pipes?

The best insulation material depends on the specific application. Fiberglass is popular for general use due to its affordability and effectiveness. Mineral wool is preferred for high-temperature applications, while elastomeric foam is ideal for preventing condensation on cold pipes. For extreme environments, materials like cellular glass or aerogel may be the best options.

How do I install pipe insulation?

Installing pipe insulation typically involves the following steps:

  • Measure and Cut: Measure the length and diameter of the pipe and cut the insulation material to fit.
  • Wrap or Slip On: Depending on the material, either wrap the insulation around the pipe or slip pre-formed sections over it.
  • Seal the Joints: Use appropriate adhesive, tape, or fasteners to seal any joints or seams to prevent heat loss or moisture ingress.
  • Protect and Finish: In some cases, especially outdoors or in high-traffic areas, you’ll need to apply a protective jacket or coating over the insulation.

Can pipe insulation be used on hot pipes?

Yes, pipe insulation is commonly used on hot pipes to reduce heat loss, improve energy efficiency, and prevent burns from accidental contact. Materials like fiberglass, mineral wool, and calcium silicate are particularly suited for insulating hot pipes.

Can pipe insulation be used on cold water pipes?

Yes, pipe insulation is effective on cold water pipes. It helps prevent condensation, which can lead to mold, corrosion, and water damage. Elastomeric foam and fiberglass are often used for cold water pipes due to their moisture-resistant properties.

What is the most effective pipe insulation?

The most effective pipe insulation in terms of thermal performance is aerogel insulation. It has an exceptionally low thermal conductivity, meaning it provides superior insulation with thinner layers compared to other materials. However, aerogel is also more expensive and may be overkill for standard applications.