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Significance of Space Velocity of Reactor

Written by Partha Pratim Panja in Piping Interface,Process

What is Space Velocity?

In chemical engineering, space velocity refers to the

Space velocity = flow rate of the feeds/ volume of the reactor (or volume of the catalyst)

Space Velocity signifies how many reactor volumes of feed can be fed in unit time (for instance, a reactor with a space velocity of 1 hr−1 is able to process feed equivalent to one time the reactor volume each hour). It is reciprocal of the reactor space-time.

Mathematically, it is expressed as SV = Vo / V. where Vo is the volumetric flow rate of the reactants, and V represents the volume of the reactor or the volume of the catalyst. This expression is the reciprocal of space-time, τ (i.e.  SV = 1/τ).

Types of Space Velocities

There are different types of space velocities which are as follows:

  • GHSV, gas hourly space velocity: It is basically the ratio of volumes of gas present in feed gas at STP/hr to the volume of the reactor or catalyst denoted as gas feed @ scfh/ft3.
  • LHSV, liquid hourly space velocity: It is the ratio of the Volume of liquid present in feed at 60″F/hr to the volume of reactor or catalyst & denoted as liquid feed@ scfh/ft3.
  • WHSV, weight hourly space velocity: It is the ratio of wt of feed/hr to the weight of the catalyst

Among these three types of space velocities, LHSV is frequently used in the oil and gas industry. It has significant impacts on hydrotreating reactions mainly in hydro-desulphurization (HDS), hydro-denitrogenation (HDN), and hydro-dearomatization (HDA).

How does LHSV affect hydrotreating reactions?

As the Liquid Hourly Space velocity (LHSV) is the ratio of the volumetric flow rate (hourly) of the liquid feed to the volume of the catalyst present in the reactor. So, LHSV is reciprocal of the space-time. Reducing LHSV generally results in an enhancement of the hydrotreating reaction. However, an excessive reduction of LHSV can create the operation difficult due to the hydraulic perspective & it can cause channeling which leads to liquid mal-distribution and under-utilization of the catalyst. A significantly high LHSV not only reduces the feed & catalyst contact time but also increases the reactor pressure drop and other hydraulic challenges.

How does LHSV affect feed vaporizations?

The higher the LHSV the faster will be the vaporization of feed as well as H2 dissolution. An increase in LHSV implies a hike in the feed flow rate (liquid). According to Raoult’s Law, with the increase of the mole fraction of a component in a solution, the partial pressure also increases, and consequently the escaping tendency increases. Therefore, more liquid feed is introduced into the reactor, and evaporation rates also become faster. Also, by increasing the liquid flow rate, there is more liquid volume for H2 to dissolve in. Hence, increases in H2 dissolution were observed.

How does LHSV affect conversion?

LHSV, which is the reciprocal of space-time, signifies the time spent in the reactor of the reactants. It was observed that reducing LHSV leads to an increase in the conversion in HDS, HDN, and HDA reactions (see the below figure).

The Effects of increasing LHSV & other parameters on hydrotreating activities.

Variables  TemperaturePressureLHSV
Ranges300-450°C4.5-12.5 MPa0.5-4 h-1
HDSIncreaseIncreaseDecrease
HDNIncreaseIncreaseDecrease
HDAIncreaseIncreaseDecrease

Variation of LHSV & Coke Laydown

The formation of coke is desirable during reaction in the reactor as it reduces catalyst activity tremendously.

As the quantity of catalyst is constant, the only way to vary LHSV is by varying the feed flow rate. A change in feed capacity will change the space velocity & the reactor inlet temperature must be changed to maintain the same severity.

To avoid coke formation the following rules shall be applied:

  • Decrease reactor inlet temperature before lowering the feed flow rate.
  • Increase the feed flow rate before increasing the reactor temperatures.

Calculation of Space velocity

Space velocity especially for hydrocracking & hydrotreating reaction is calculated by conversion of BPSD (rated) into equivalent cubic feet at 60oF i,e (BPSD x 5.615)/24, for a day. The total catalyst volume is to be determined in ft3 by taking the cross-sectional area of the reactor x sum of the vertical heights of a bed of the catalyst excluding the top disc & alumina supported balls.

Another way of calculation is, first convert BPSD to mt/hr, i,e BPSD/(6.29 x S.G of oil @ 60’F) divided by 24 hrs. The volume of (ft3) of active catalyst is converted to weight through the multiplication of the bulk density of the catalyst. Normally loaded density depends on sock loading or dense loading & this density falls between 45 lbs/ft3  sock loading to 50 lbs/ft3 dense loading.

What is space-time in a reactor?

The Space-time of a reactor is defined as the time required to process one reactor volume of feed into a reactor at the inlet condition. It is basically denoted as τ (tau) = V/Vo where V is the reactor volume & Vo is the volumetric flow rate of feed.

Residence time & Space-time

Both times are similar but not exactly the same. Space time is the time needed to process a reactor volume of feed at the reactor inlet condition and the residence time is the average time spent by a reactant particle until it exits from the reactor.

What is a U-bolt? Types, Installation, and Applications

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

A u-bolt is a u-shaped curved bolt having threads on each end used as support in the piping and pipeline industry. U-Bolts are one of the simplest and most widely used types of piping support. They work mainly as Rest+Guide+Hold down support; though with a little installation, changes can be made to work as line stops as well. U-bolts with their curved shape fit nicely around the pipes which are then secured with a secondary member using nuts. They are easily available in various sizes and thicknesses. The important dimensions of a u-bolt are shown in Fig. 1 below:

Major dimensions of a U-bolt
Fig. 1: Major dimensions of a u-bolt

Applications of U-bolts

U-bolts have an extended range of applications. They are widely used as piping support solutions. The common uses of u-bolts in piping solutions are:

Use of u-bolt as pipe supports:

They are used to provide lateral restraints to pipes. For small-bore piping systems, u-bolts are the most simplest and widely used type of piping support. In any plant, for supporting bare pipes lesser than 8-inch size, u-bolts are extensively used. As already stated they function as rest+guide+hold down. U-bolts are capable to suppress line vibrations by providing rigidity to the system. For supporting vertical elevated runs of pipe, U-bolts are a good choice.

Uses of u-bolts for pipe shipping:

In the pipe and pipeline shipping industry, u-bolts are used to avoid pipe movement and breakage. U-bolts prevent haphazard pipe movements due to transportation loads.

Materials of U-bolts

Even though u-bolts can be manufactured from any type of strong and durable materials; in the piping industry, the following materials are widely used.

  • Plain Carbon Steel, and
  • Stainless steel.

Sometimes, protective coatings are added to prevent corrosion. Some of the usual u-bolt coatings are:

Types of U-bolts: Gripped vs Non-gripped U-bolts

In general, u-bolts are used as guide+hold down. However, they can be used to work like anchors as well. Depending on these u-bolt functions, they are classified into two groups; Gripped u-bolt and non-gripped u-bolt.

Non-gripped U-bolt: U-bolt as Guide

Non-gripped u-bolt is the most common and simple installation to work as the pipe guide. It does not restrict axial movement. In non-gripped pipe u-bolt installation, one nut is placed on the top and the other on the bottom of the support beam. Both nuts are fixed, keeping a gap in between the pipe and the u-bolt surface.

Gripped U-bolt: U-bolt as Anchor

In gripped u-bolt configuration, the u-bolt work as an anchor and stop pipe movement at the support location. To work the pipe u-bolt as an anchor, the u-bolt needs to be installed such that there is no space between the pipe and u-bolt. Both bolts are placed at the bottom of the secondary support structure and tightened to snug against the pipe. The friction force in between the clamp and pipe surfaces restricts the pipe movement in the axial direction to work as a directional anchor. However, with an increase in line stops axial forces, the frictional force may not be able to withstand the axial force and may slip. This is the reason the use of u-bolt as anchors is limited to lower-size pipes; usually up to 6-inch pipes.

Fig. 2: Gripped vs Non-gripped U-bolt

Installation of U-bolts

Installing a pipe U-bolt is very easy. The size of u-bolts is decided based on the pipe OD. All properly sized u-bolts come with threads and nuts. The only job is to drill the hole in the support beam, properly align the bolt through those holes, and tighten the nuts depending on the support type (anchor type or guide type).

What is a Wear Pad? Functions of Pipe Wear Pads

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

To protect surfaces and improve sliding properties, wear pads are used in industrial applications from earlier days. Also known as slider pads, wear pads increase the wear resistance capability and provide higher strength. In this article, we will explore more details about Piping Wear Pads.

What is a Pipe Wear Pad?

A pipe wear pad is a type of pipe support used to isolate the main pipe surface from direct rubbing with structural surfaces. By installing these on outside pipe surfaces, wear pads for pipe reduce the metal-on-metal damage. Piping wear pads basically replace the contact point from the main pipe to the wear pad material.

What are the Materials used for Pipe Wear Pads?

Wear pads for pipes can be made of metallic or non-metallic/composite materials. Depending on the requirement and temperature of the piping surface, the wear pad material is decided. Common wear pad materials for piping systems are:

Purpose/Functions of Pipe Wear Pads

As the outer surfaces of the piping system are constantly experiencing corrosion, wear, and tear they can be weakened easily. Over time, these can even cause the failure of the components leading to plant shut-down or major hazards. In such a scenario, piping wear pads are one of the easy solutions to reduce corrosion and increase pipe system longevity. The main functions that pipe wear pads serve are:

1. They eliminate metal-to-metal damage. There are two modes of damage that can happen:
Metal-to-metal wear damage by rubbing caused by thermal and pressure fluctuations. Wear pads fit on the pipe’s outer surface on support locations and preserve the pipe material.
Galvanic Corrosion due to dissimilar metals: Galvanic corrosion by the electrochemical reaction can occur when dissimilar metals remain in contact with each other. Pipe wear pads isolate dissimilar materials and discourage galvanic corrosion.

2. Wear pads eliminate the possibility of crevice corrosion of the piping system. When a pipe moves over the structure, the motion can pull off the pipe’s outer layer. So, grooves are created for microbes to creep in, resulting in crevice corrosion by bacteria. Wear pads for piping systems to stop these corrosive cells to form by absorbing the surface impact themselves and safeguarding the pipe material.

3. As wear pads are directly fixed on the pipe, they displace along with the pipe without leaving any scope for dust or grit accumulation on the pipe surface which in turn avoids damages that may be caused by dust or grit particles.

4. Installing composite wear pads does not require welding on the pipe which in turn keeps the pipe system fully intact. They are usually fixed to pipes by extremely strong epoxy adhesives.

5. Composite wear pads absorb the frictional forces within then keeping the parent pipe material safe.

6. Wear pads safeguard the piping systems from damaging vibration effects by providing a damping effect and increasing stiffness. Pipe wear pads help the parent pipe material from banging on the support structures.

So, in a nutshell, wear pads drive long-term performance by reducing corrosion, and wear, and thus preserving pipes.

Installing Pipe Wear Pads

Metallic wear pads are welded with pipe similar to reinforcing pads. Composite wear pads are bonded with pipe using epoxy adhesives. Wear pads can fully or partially enclose the pipe. The image in Fig. 1 shows a typical wear pad used in piping systems.

Pipe Wear Pad
Fig. 1: Pipe Wear Pad

Length of Wear Pads

The minimum length of pipe wear pads is calculated as follows:

  • For wear pads with line stops the minimum length of wear pad=structure (beam) width+2*each line stop member dimension+2*one side gap for line stop+50 mm.
  • For wear pads without line stops the minimum length of the wear pad= structure (beam) width +maximum thermal movement at that support location+50 mm.

When to use Wear Pads?

Pipe wear pads are extensively used during the following situations:

Use of Metallic Wear Pads:

  • Metallic wear pads are used for strengthening thin-walled pipes to avoid local damage in support locations.
  • If piping support is experiencing a relatively higher load then wear pads are suggested to safeguard the pipe from support load reaction.
  • Wear pad supports are normally suggested for line stops with relatively high loads. In many consultancy organizations, it is a standard engineering practice to use wear pads for all pipe supports of pipes exceeding 24-inch size.

Use of Composite Wear Pads:

Composite wear pads are widely used for

  • reducing corrosion.
  • damping vibration.

Difference between RF Pad and Wear Pad

The main differences between reinforcement pads and wear pads are

RF pads or Repads are used for pressure integrity. When a piping system is not able to withstand pressure stresses locally due to removing metal for branch connection or high stresses, Repads are used to provide local strengthening. Reinforcing pads are usually provided in equipment nozzle connections, pipe branch connections, or trunnion connections.

On the contrary, wear pads are used as pipe supports. They provide wear resistance and high strength to pipes in support locations.

What is a Pipe Anchor? Its Definition, Types, and Functions

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

A pipe anchor is a type of pipe support that is used to control pipe movements by fixing the pipe with secondary civil structures. Piping anchor supports are very important in piping and pipeline systems. The complete thermal behavior of the piping system is decided by the location of the pipe anchor supports. For proper control of thermal expansion and contraction, there is no alternative to pipe anchors. In this article, we will try to understand the basics of pipe anchor supports.

Types of Pipe Anchors

Depending on the restriction pipe anchor supports provides to piping at the support location, they are classified into two groups:

  • Fixed pipe anchors or Full anchors, and
  • Directional pipe anchors.

Fixed Pipe Anchors

As the name suggests, Fixed pipe anchors fix the pipe at that location. We all know that a point in space has six degrees of freedom. Three in the translational direction and three in the rotational direction. Fixed pipe anchors restrict the pipe from moving in all six directions. In actual applications, the pipe at that location is either directly welded or bolted to the support beam so that the pipe can not move in that location. As the pipe is fully restricted at this location depending on the piping configurations forces and moments in all six directions will be generated. So, these types of pipe anchors must be designed considering forces and moments from all directions. Fixed pipe anchors are rarely used in piping systems. Usually, they are preferred for high vibration-prone lines, near pressure control valves, blowdown valves, locations where thrust force can generate, etc.

Typical Fixed and Directional Pipe Anchor
Typical Fixed and Directional Pipe Anchor

Directional Pipe Anchors

Directional pipe anchors arrest the movement only in the pipe longitudinal direction. In all other directions, piping directional anchors allow movements. They are also popularly known as line stop supports, axial stop supports, or limit stops. These types of supports usually experience only vertical and axial forces and are easier to design. In pipe and pipeline systems, pipe directional anchors find wide applications. One of the most widespread applications of directional pipe anchor supports is in the design of expansion loops. On either side of the pipe and pipeline expansion loops, one line-stop support is provided.

Locating Pipe Anchors

Deciding the locations of pipe anchors are very important. The best location to use anchor supports is at the neutral points of piping and pipeline configurations. Locating pipe anchor supports near-neutral points will provide the lowest thermal loads. However, it is not always possible to locate piping anchors at the neutral point. So, depending on the requirement, these supports must be judiciously located to safeguard the pipe system.

Functions of Pipe Anchors

Piping anchor supports in a piping and pipeline system usually serve the following purposes:

  • It helps in the proper distribution of pipe thermal displacements.
  • It provides sufficient rigidity to the piping system to avoid the damaging effects of vibration.
  • It safeguards the pipes from detrimental seismic, wind, and other dynamic events.
  • Pipe anchors are extensively used to absorb thrust forces, PSV reaction forces, Slug and Surge forces, etc.
  • It helps in equipment nozzle load qualification by limiting pipe movements to the equipment.
  • Pipe anchors help pipe stress engineers in pipe system breaking. So, the whole plant can easily be broken down into a number of smaller systems, thus helping the stress engineers in easy handling and analysis.
  • Pipe anchors are also used for scope demarcation between vendors to decide boundary conditions for each client of the same project.
  • By controlling the pipe movements as per design requirements, pipe anchors improve the performance and longevity of the piping and pipeline system.

Factors affecting Pipe Anchor Design and Installation

While designing and installing a pipe anchor in pipeline and piping systems, the engineer should pay attention to various factors like:

  • Pipe Support material: When welding directly to the pipe, anchor material should be compatible with the pipe material to avoid galvanic corrosion. For all other cases, the anchor support material should be of sufficient strength to resist all the loads arising due to pressure and temperature fluctuations in a pipe.
  • Support loads: For deciding member sizes of pipe anchors actual loads must be considered. Usually, pipe stress engineers provide loads experienced by pipe supports after pipe stress analysis.
  • Corrosion resistance: Sometimes, to reduce the effects of corrosion, pipe anchors may be equipped with hot-dip galvanizing, anti-corrosive materials, or protective coatings.

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What is a Pipe Shoe? Its Types and Functions

Written by Anup Kumar Dey in Piping Stress Basics,Piping Supports

Being a piping engineer you must be familiar with the term “Piping Shoe”. Pipe shoe supports are highly popular for insulated lines. As insulation material is usually not capable to withstand high piping loads, piping shoes are used to transfer the piping loads to secondary civil structures without damaging the insulation.

What is a Piping Shoe?

A pipe shoe is a special type of pipe support structure made of structural members or plates with a flat base. Pipe shoes find major applications for supporting the following pipes:

Functions of Pipe Shoes

Pipe shoes act as an intermediate member between the pipe and the secondary steel structure and serve the following purposes:

  • They stop pipes/ insulation from rubbing against structures thus preventing damage to insulation material.
  • By separating the pipe and structure materials separate, they help in preventing galvanic corrosion in case of dissimilar material.
  • Pipe shoes help to increase the structural life by not transferring the high pipe temperature to the structure.
  • Pipe shoes help in preventing pipe damage for thin-walled pipes in support locations by transferring the loads to structures.

Types of Pipe Shoes

Pipe shoe supports are categorized based on various parameters as provided below:

Depending on the material of construction, pipe shoes are classified into two types: Metallic pipe shoes, and composite pipe shoes.

Metallic Pipe Shoes

As the name suggests, this type of shoe is made from metals. This is the most common type of piping shoe support used in the process and power piping industries. Metallic piping shoes are the oldest type of piping shoes that serving the piping industry for decades. Traditionally, metallic pipe shoes are manufactured from I-beams, channels, or structural plates. Metallic pipe shoes are simple and low-cost piping support solutions for high-temperature piping systems.

Composite Pipe Shoes

Composite pipe shoes offer the best corrosion-resistant alternative to metallic pipe shoes. They are usually UV resistant, strong, and durable. They are a relatively new addition to pipe shoe groups.

Depending on the attachment of pipe shoes to the parent pipe, they are classified into two groups: welded shoes and clamped shoes.

Welded Pipe Shoes

When pipe shoes are directly welded to the pipe, they are known as welded pipe shoes. Welded pipe shoes are normally used for carbon steel pipes for which welding is easy and cheaper. Welded pipe shoes have very high load-carrying capabilities and are suitable for axial and lateral loads.

Clamped and Welded Pipe Shoe
Clamped and Welded Pipe Shoe

Clamped pipe Shoes

For certain material, direct welding in pipes are not permitted or welding is costly and difficult. In such a scenario, clamped pipe shoes are used and the pipe shoe is welded on the clamps. For galvanized pipes, stainless steel pipes, DSS pipes, etc clamped pipe shoes are used. Parent pipe-compatible clamp material is chosen so that no galvanic corrosion occurs and then the shoe material is welded on the outside surfaces of the clamps. Clamped piping shoe supports, in general, carry lower loads as compared to welded counterparts. Clamps pipe shoes are not advisable to use as axial stops or line stops.

Depending on the construction, pipe shoes are of two types: T-type shoes and Saddle-type shoes.

T-type Piping Shoes:

They are usually used for pipe shoes having lower loads. Usually, pipes with a size of less than 26 inches use T-type pipe shoes.

Saddle-type Pipe Shoes:

Saddle supports are used for pipes with sizes exceeding 24 inches. They are suitable for carrying high loads.

Deciding Pipe Shoe Lengths

It is a better engineering practice to standardize pipe shoe designs. In most plants, a shoe length of 300 mm is normally used for pipes up to 24-inch size, and a length of 500 mm is used for pipes with diameters exceeding 24 inches. However, depending on the thermal movement at the support location the shoe length needs to be adjusted.

For example, a 300 mm long pipe shoe will support the pipe over the structural member up to a 150 mm longitudinal pipe movement. If the pipe movement is more than 150 mm, then the length of the pipe shoe should be increased accordingly so that the pipe support does not fall off the structural member.

Also, the shoe supports with line stop members usually require more lengths than the standard pipe shoe lengths. So, based on the dimensions of the secondary structural member and line stop member the pipe shoe length needs to be increased.

Pipe Shoe support with Guide and line Stop
Pipe Shoe support with Guide and line Stop

Factors affecting Pipe Shoe Design

The main parameters that affect the design of pipe shoes are

  • Expected Support loads: Members need to be designed based on these loads.
  • Pipe Insulation thickness: Pipe shoe height is decided based on the pipe insulation thickness. Normal practice is Piping Shoe Height=Pipe Insulation thickness (mm)+25 mm.
  • Thermal Displacement at the support location to decide shoe length.
  • Support type in the location: For example line stop supports will require more lengths.
  • Shoe material: To be compatible with pipe material.

There are two other terms that are often associated with pipe shoes; Hot Shoe and Cold Shoe.

Hot Shoes: Hot pipe shoes usually refer to pipe supports for high-temperature piping systems.

Cold Shoes: A cold shoe normally refers to a support component that incorporates an insulating material that attaches directly to the pipe. This pipe shoe with insulation functions as a load-bearing component for transferring the pipe load to the structure.

Click here to learn more about Piping Supports

Online Video Courses on Piping Support

To learn more about piping support design and engineering you can opt for the following video course.

PSIA vs PSIG: Differences | Conversion from PSIA to PSIG and PSIG to PSIA

Written by Anup Kumar Dey in Process

PSI is the most basic unit for measuring pressure in the FPS unit system which is widely used in the United States and European countries. Most of household sporting goods, pressure transducers, etc use the unit PSI which stands for pounds per square inch. PSI signifies the pressure resulting from one pound-force applied to one square inch area. The mathematical symbol for PSI is “lb/in2” and it expresses the unit of pressure or stress. One psi is approximately equal to 6,894.75729 Pa (Pascal)

There is two widely used specific form of pressure measurement under PSI. They are PSIA and PSIG.

What is PSIA?

PSIA is the most common and referenced form of pressure measurement that stands for pounds per square inch absolute. Absolute pressure is defined as the pressure relative to zero or absolute vacuum. PSIA is used on engineering documents like P&IDs.

What is PSIG?

PSIG which stands for pounds per square inch gauge is also used extensively. Gauge pressure is defined as the pressure relative to the ambient atmospheric pressure. PSIG is used for instrument pressure gauges in equipment, oilfield valves, regulators, etc.

Refer to the image in Fig. 1 that clearly explains the concept of PSIA vs PSIG and absolute pressure and Gauge Pressure.

PSIA vs PSIG
Fig. 1: PSIA vs PSIG

What are the differences between PSIA and PSIG? PSIA vs PSIG

From the above discussion, we can interpret the main differences between PSIA and PSIG as follows:

  1. PSIA is the unit of pressure measurement in the English system relative to absolute zero or full vacuum pressure (0 PSI) whereas PSIG is the unit of pressure measured relative to atmospheric pressure.
  2. PSIA is always greater than PSIG.
  3. PSIA indicates the total pressure, whereas PSIG indicates the pressure relative to the atmospheric pressure at the location. In absence of data at the exact location, the atmospheric pressure of sea level (14.7 PSIA) can be used.
  4. PSIA does not change with altitude but PSIG changes with a change in altitude as less air molecules will be present at higher altitudes to create pressure.
  5. PSIA can never be negative but PSIG can be negative. Vacuum pressures in PSIG below atmospheric pressures are negative.

How do I Convert PSIG to PSIA? | PSIA to PSIG and PSIG to PSIA Conversion

It is easy to convert from PSIA to PSIG and vice versa. The formula that describes the relationship between PSIA and PSIG is:

PSIA=PSIG + 1 Atmospheric pressure
PSIG=PSIA – 1 Atmospheric pressure.

So by knowing the atmospheric pressure of any location, you can easily convert pressure from PSIA to PSIG or vice versa. At sea level, the above equation can be written as

PSIA=PSIG + 14.7
PSIG=PSIA-14.7

Should I use PSIA or PSIG?

If the measured pressure is not affected by the changes in atmospheric pressure then you should use PSIG or gauge pressure. Some typical applications are for measuring pneumatic pressure, hydraulic pressure, or the level of liquid in an open tank, etc. The P&ID and Line lists of oil and gas industries usually provide pressures as PSIG.

On the other hand, if the atmospheric pressure affects the measured pressure then you should go for measuring absolute pressure or PSIA. For example, To measure pressure in a closed system or closed container, To measure the atmospheric pressure (weather prediction), and To assess altitude in aeronautical applications, you should use an absolute pressure gauge to measure PSIA. Research laboratories, Food packaging industries, etc use PSIA extensively.

Is 0 PSI a Vacuum?

A vacuum is defined as a partially exhausted space. Vacuum pressure is defined and measured relative to the ambient atmospheric pressure. Usually, air pumps are used to remove air from a confined space and thus create a vacuum. We learned that 1 atmosphere is roughly 14.7 PSIA. So, if the atmospheric air is removed from the space the pressure will fall below 14.7 PSIA and the Vacuum will start to create. Once, the full air is removed from a confined space, it will reach 0 PSIA which is known as the full vacuum.