Level Indicator (Level Gauge)

Hi, 

Several days ago, I was called by my manager to his room and he asked me about level indicator (level gauge) which I signed in that document, He asked me about type of level gauge, connection, visibility length and c/c length, since I am new in this area so I just can answered some. He always remain me that even you are new in this area, you have responsibility since you sign in the document. learn form that so I discovered about level gauge and found good resource to learn, here it is:

Definition of Level Indicator
Level indicators are devices used in the measurement of level of fluids at various industrial applications. These devices are used to determine the level of liquid in tanks, drums. pressure vessels etc..

Level Indicator

Cited from reference no. 1 on 28 April 2015.

There are many level indicators to suit the needs of different applications. Normally, fluids are used in many forms in highly commercial industries. Without proper devices it will be very difficult to find the quantity and level of fluid stored. Also, in certain situations where the nature of fluid is dangerous or the place in which the liquid is stored is of such a nature that it is manually impossible to find the level, then the level indicators are of utmost importance.
Depending on the type of application used, the type of level indicator should be selected. For example, in the process industry, tubular level indicators are used for better visual liquid level indication. If it is for non-contact type level measurement, then radar type indicators or ultrasonic type indicators are to be used.

Types of Level Indicators
There are many different types of level indicators, each with its own application.

• Transparent level indicators are highly useful in chemical industries and petrochemical fertilizers. As the fluid is stored in high pressure and high temperature, the transparent level indicator is very useful to find the fluid level.
• Reflex level indicators are for applications that involve high temperature, high pressure and use of corrosive fluids. The colorless fluid used in this apparatus gives better clarity to level indication.
• Magnetic level indicators are red followers that need magnetic level indicators. Cylindrical floats and powerful magnets are used to find the level of the fluid. The float movement is followed by magnetic capsules, and thus, the level in indicated. This type of indicator has good visibility and is absolutely safe to use as it contains non-fragile metal chamber.

Some other level indicators for reference are tubular level indicators, float and board level indicators, sight flow indicators, window type sight flow indicators, manometers, and bi-color indicators. Some of the level indicators are provided with various features, such as a built-in controller, continuous output measurement, and adjustable alarm switches.

Transparent Level Gauge
Working principle
Apart from glass tube level gauges, transparent level gauges are always fitted with two plate transparent glasses between which the fluid is contained. The fluid level is indicated as the result of the different transparency of the two media and in some cases (for water steam), by conveying upwards on to the surface of separation (between liquid and gaseous substances) a source of light located at the back of the gauge, the rays of which are totally reflected down to the observer.

Transparent Level Indicator

Cited from reference no. 1 on 28 April 2015.

Applications
Transparent level gauges are suitable for almost all installations.
In fact they permit:

• the use of mica shields or Polytrifluorochloroethylene shields to protect the glass from the corrosive action of the process fluid.
• the observation of interface.
• the observation of the liquid colour.

This instrument consists of a metal body, machined to have an internal chamber and one or more front windows (on each side of the gauge). On each window a special high resistance plate transparent glass is applied with sealing joint and metal cover plate hold by bolts and nuts.
The chamber is connected to vessel with cross fittings and flanged, threaded or welded ends. Usually, between the instrument and its connecting ends, valves are fitted to consent shut-off piping and to disassemble the level gauge without to empty the vessel. Drain valves can also be fitted to cross fittings device.

To avoid leakage in case of glass breakage, safety ball-check device can be provided in cross-fittings or shut-off valves. This kind of indicator is suitable for water/steam. To protect glass surfaces from corrosive action of the process fluid, Transparent Level Gauges can be fitted with Mica shields or Polytrifluorochloroethilene shields. This kind of indicator is suitable for liquids colorless and very fluid.

In some case (i.e. for water / steam) the best reading is obtained by conveying upwards on the surface of separation (liquid/steam or vapor interface), a source of light, located on the back of the gauge, the rays of which are totally reflected down to the observer.

Reflex Level Gauge
Working principle
Reflex glass level gauges working principle is based on the light refraction and reflection laws.
Reflex glass level gauges use glasses having the face fitted towards the chamber shaped to have prismatic grooves with section angle of 90°. When in operation, the chamber is filled with liquid in the lower zone and gases or vapors in the upper zone; the liquid level is distinguished by different brightness of the glass in the liquid and in the gas/vapor zone. The reflex level gauges do not need a specific illumination: the day environmental light is enough. Only during the night an artificial light must be provided.
The different brightness in the two zones is obtained as explained below:

Liquid zone
This zone appears quite dark when the gauge is in operation and lighted as above said.
Given the construction, most of the environmental light rays incident on the external face of the glass are quite perpendicular to said face and, therefore, not deviated by the glass. These rays reach the glass/liquid interface with an inclination of approx. 45°. The critical angle glass/liquid is always superior to 45°. Therefore the rays incident within the critical angle (practically the totality) are refracted within the liquid and, since the internal walls of the gauge chamber are not reflecting, the rays cannot be seen from the outside. In fact the zone will appear dark, nearly black, to the observer.

Gas/vapor zone
This zone appears almost silver bright to the observer.
As for the liquid zone, the light rays reach the glass/gas-vapor interface with an angle around 45°. Since this angle is greater than glass/gas-vapor critical angle, the rays are not refracted , but totally reflected making 90° turn, thus reaching the nearest glass/gas-vapor interface again with angle of 45°. For same reason they will be reflected and turned by 90° towards the observer, to whom the zone will appear silver bright.

Applications
Reflex glass level gauges can be used in most of the cases and offer great advantages in terms of: low initial cost, low operating cost, easy level reading.

Reflex level gauges cannot be used in certain cases as for example:

• when the separation level between two liquids has to be read (interface).
• when besides the level indication, the observation of the liquid colour is required.
• when the process fluid is high-pressure water steam, since in this case the glass must be protected from the solvent action of the boiler water by using mica shields.
• when the process fluid is such that can corrode the glass (e.g. high temperature alkaline solutions or hydrofluoric acid), since ica shields or Polytrifluorochloroethylene shields must be used to protect the glass.

Magnetic Level Gauge
The Magnetic Level Gauge is the instrument to read a level indication in whatever plant or operating conditions giving free maintenance, preventive security against leakage, environmental safety, sure and trouble free application with chemically aggressive, pollutant, harmful or poisonous, inflammable or explosive, optically similar fluid interface.

Magnetic Level Indicator

Cited from reference no. 1 on 28 April 2015.

Operating principle
The operation of the magnetic level gauge is based on some elementary physical principles:

• The principle whereby the liquid in communicating vessels is always at the same level
• Archimede's principle according to which a body immersed in a liquid receives a buoyancy equal to the weight of displaced liquid
• The principle of attraction between North and South poles of two permanent magnets and that of repulsion between like poles.

This principle has two applications in the magnetic level gauge:

• first between the magnet in the chamber float and every single magnet of the indicating scale
• second between the magnets of the indicating scale

Applications
The application range is very wide and includes all the situations where the fluids are:

• at high pressure, at low or high temperature
• at low pressure, at low or high temperature
• chemically aggressive
• pollutant to environment
• noxious or poisonous for people health
• inflammable or explosive
• with identical optical characteristics of the superimposed phases (interface)

Design
The magnetic level gauge consists of:

• a vertical chamber consisting of a tube of suitable diameter and thickness containing a float wherein a permanent magnet is placed exactly on the liquid level line
• two horizontal stub pipes for connection to the vessel containing the liquid of which we wish to know the level
• two stop valves (recommended, but not mandatory) one on each stub pipe, to isolate the level gauge
• an indicating scale, outside the vertical chamber, consisting of a case of non-magnetic material with transparent front face containing a set of small permanent magnets enclosed in small cylinders which can rotate on their horizontal axis.

These cylinders show an external surface having two different colours.
According to the orientation of each magnet (due to the action of the magnet in the float) each cylinder will show externally half of its surface of one colour or the other.
The indicating scale will be of one colour (e.g. white) over the chamber area taken up by gas, vapour or steam phase contrasting with the other colour (e.g. red) over the chamber area taken up by liquid phase.
Alarm system for damaged float. The three bottom cylinders of the indicating scale are placed lower than the bottom connection of the magnetic level gauge. They are used for control of float efficiency. With float damaged and its consequent sinking in the liquid, these three cylinders show the yellow surfaces.

These level gauges are very suitable for interface reading: the level gauge float has only to sink in the liquid having lower specific gravity and to float on the liquid having higher specific gravity.

References:

1. http://www.wermac.org/specials/levelgauge.html (28 April 2015)

That's all.

Breather Valve Introduction

Hi, 

For this time I will let you know about breather valve and I found perfect resource for explanation, this is it:

What are Breather Valves?

Breather Valves, also known as direct acting Pressure/Vacuum Relief Valves, are special types of Relief Valves which are specifically designed for tank protection. The range includes pressure only, vacuum only and combined Pressure/Vacuum Valves, all available with flanged outlets or vented to atmosphere.

Breather Valve

Cited from reference no. 1 on 20 April 2015.

Pressure/Vacuum Relief Valves are used extensively on bulk storage tanks, including fixed roof tanks with floating covers, to minimize evaporation loss. The Valves prevent the build up of excessive pressure or vacuum which can unbalance the system or damage the storage vessel. Pressure and vacuum protection levels are controlled with weighted pallets or springs and can be combined to provide the required Pressure/Vacuum settings. It is common to combine pallet and spring systems in one unit i.e. pressure settings require a spring section, whilst the vacuum settings use the pallet method.

Why use Breather Valves?

The Breather Valve is a protection device mounted on a nozzle opening on the top of a fixed roof atmospheric storage tank. Its primary purpose is to protect the tank against rupturing or imploding. Breather Valve Without an opening or a controlled opening, a fixed roof atmospheric tank would rupture under increasing pressure caused by pumping liquid into the tank or as a result of vapor pressure changes caused by severe thermal changes. Imploding, or the collapsing of a tank, occurs during the pumping out procedure or thermal changes. As the liquid level lowers, the vapor space pressure is reduced to below atmospheric pressure. This vacuum condition must be alleviated through a controlled opening on the tank. In short, the tank needs to breathe in order to eliminate the possibility of rupturing or imploding. Because of its primary function, this Valve is called Breather Valve. Valve selection should be in accordance with American Petroleum Institute Standard API 2000 or other applicable standard.

How Breather Valves operate?

Most atmospheric tanks require a venting device that will allow large volumes of vapor to escape under relatively low pressures. Usually the allowable set pressure is in inches of water column pressure, both for positive and vacuum conditions. This is because most large storage tanks have a relatively low maximum allowable working pressure. These tanks are generally large volume welded vessels that are built to API 650 standard. In order to accommodate large volumes at low set pressures, these Valves have ports that are greater in area than the inlet or nozzle connection. The low setting required necessitates weight loading the Valve as opposed to spring loading. Because of the above, a Breather Valve requires approximately 100% over set pressure in order to reach full opening of the Valve.

How Breather Valve Operate?

Cited from reference no. 1 on 20 April 2015.

However, when deciding on a set pressure, the weight-loaded Valve operation MAWP should be at least twice the required set pressure to obtain optimum flow. If the MAWP is less than 100% above the required set, the Valve could be larger in size than normally required. The possibility of Valve chatter and accelerated seat and diaphragm wear will exist if less than 20% over pressure is allowed. Simply stated, a Pressure/Vacuum Valve is not exactly like a high pressure safety Relief Valve and should not be sized at 10% or 20% over pressure. When sizing a Pressure/Vacuum Valve, consult the manufacturer flow curves and allow sufficient over set pressure.

API Standard 2000 for Venting Atmospheric and Low Pressure Storage Tanks

Sizing a Breather Valve

API Standards are provided as an engineering aid for specification and selection of "normal" and "emergency" pressure and vacuum Relief Valves for above ground liquid petroleum storage tanks. Normal venting capacity is obtained without exceeding pressure or vacuum that would cause physical damage or permanent deformation to the tank. The following will help in sizing a Pressure/Vacuum Valve:

• Normal Relief: The sum of vapor replacement resulting from emptying or filling and thermal in-breathing or out breathing.
• Emergency Relief: Thermal out-breathing from fire exposure.
• All Tanks: Generally require the sizing of a normal pressure and vacuum Relief Valve to be sized and an independent emergency Relief Valve to be sized separately.
• Flow Curves: These curves provide pressure and vacuum capacity which is required for sizing.

OSHA and API requirements

The OSHA requirement for tank protection published by the Department of Labor and part 1910.106 revised as of July 1, 1985 addresses sizing requirements. OSHA suggest sizing should be in accordance with API 2000. All requirements are clearly defined in this publication.

API 2521

"Pressure/Vacuum Valves on atmospheric pressure fixed-roof tanks are usually set at 1/2 oz. per square inch pressure or vacuum. Test data indicate that an increase of 1 oz. per square inch in the pressure set point over the usual 1/2 oz. per square inch reduces breathing losses by approximately 7 percent. However, the test data indicate that each additional increase of 1 oz. per square inch in pressure set point reduces the breathing losses in progressively smaller increments."

API 2513

"The pressure and vacuum setting of a breather Valve are dictated by the structural characteristics of the tank and should be within safe operating limits. A certain amount of pressure and vacuum beyond this setting is necessary to overcome pressure drop in order to obtain required flow. Proper size and settings can best be determined by reference to API Std 2000: Venting Atmospheric and Low-Pressure Storage Tanks (1992) and to the manufacturers tank data determined in accordance with this publication. The pressure setting for Pressure/Vacuum Valves to be installed on large tanks constructed in accordance with API 12: Specification for Large Welded Production Tanks (1957) usually is limited to 1/2 oz. because roof plates will start to shift when the pressure rises much above 1 oz."

References:

1. http://www.wermac.org/valves/valves_breather.html (20 April 2015).

That's all.

Emergency Shutdown System (ESD) Definition Based On API RP 14C

Hi,

I just want to share about my problem to define between Safety Instrumented System (SIS) and Emergency Shutdown System (ESD). Is there any deferences? I read ANSI/ISA 5.1 2009 to find right symbol for ESD but I got nothing, I also asked to my mentors but still didn't get enough information to know. And enlightenment came when I asked to Google and found forum with subject "ESD vs SIS". From what I know after read information from that forum "ESD is a manual input for SIS" and another informed we should read API RP 14C to know clearly about ESD. So I tried to find that standard and found it. So here is ESD definition I cited from that standard:

An Emergency Shutdown (ESD) system is a system of manual control stations strategically located on a platform that, when activated, will initiate shutdown of all wells and other process stations. This system may include a number of independent process shutdown systems that can also be actuated separately. Activation of the ESD system should result in the termination of all production activity on the platform, including the closing of all pipeline SDVs. The ESD system should be designed to permit continued operation of electric generating stations and fire fighting systems when needed in an emergency.

The ESD system provides a means for personnel to manually initiate platform shutdown when an abnormal condition is observed. Fusible elements of the fire loop may be integrated with the ESD control loop.

So now I know that ESD is part of SIS for safety purpose to protect either plant or people and ESD will active when there is someone activated (manually).

That's all.

Flow Measuring Principle (Coriolis, Differential Pressure & Ultrasonic)

Hi,

I usually open all bookmarks website from my browser as standard in morning (in working day exactly) then today i found good resource to learn principle of flow measurement including coriolis, differential pressure and ultrasonic. So enjoy it:

Coriolis flow measuring principle:

Differential pressure flow measuring principle (orifice, nozzle & venturi):

Ultrasonic flow measuring principle:

That's all.