Dipil
Safety Consultant
Kvsundaram
Safety & Production
Harshavardhan13
Hr Executive
+3 Others

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Dear Sirs, Pls. throw some lights on "Pressure Vessels". Vessel of any size of pressure above atmosphere is to be considered as pressure vessel or any criteria is there? Pls. reply. Regards, SSM
From India, Madras
Dear SSM,

Pressure Vessel means, any vessel subjected to or operated at a pressure greater than the atmospheric pressure.

Safety requirments for Pressure Vessels as per Maharashtra Factories Rules 1963 are as follows -

(i) Every pressure plant or pressure vessel shall be fitted with-
(a) a suitable safety valve or other effective device, conveniently located to ensure that the maximum safe working pressure of the vessel shall not be exceeded at any time;
(b) a suitable pressure gauge with a dial range not less than 1.5 times and not exceeding twice the maximum safe working pressure, easily visible and designed to show, at all times, the correct internal pressure in kilograms per square centimetre and marked with prominent red mark at the maximum safe working pressure of the pressure plant or pressure vessel;
(c) a suitable stop valve or valves by which the pressure vessel or the system of pressure vessels may be isolated from other vessels or source of supply of pressure;
(d) a suitable nipple and globe valve connected for the exclusive purpose of attaching a test pressure gauge for checking the accuracy of the pressure gauge referred to in clause (b) of the sub-rule;
(e) a suitable drain cock or valve or a plug at the lowest part of a pressure vessel so as to ensure effective draining of liquid that may be collected in the pressure vessel.
(ii) Every pressure gauge, stop valve, nipple and globe valve, shall be mounted at a height not more than 1.5 metres from the working level.
(iii) Every pressure plant or pressure vessel not constructed to withstand the maximum possible working pressure at the source of supply or the maximum pressure which can be obtained in the pipe connecting the pressure vessel with any other source of supply shall be fitted with a suitable reducing valve or other suitable automatic device to prevent the safe working pressure of the vessel being exceeded. Suitable pressure guages shall be provided close to the reducing valve to show the high pressure and reduced pressure.
(iv) In case of a jacketted vessel in which heat is transmitted by means of steam or other media in the jacket causing pressure rise in the vessel, the heat input in the jacket shall be so controlled by a suitable device as not to allow the safe working pressure of the vessel being exceeded.
(v) To further protect the pressure vessel in the event of failure of reducing valve or the control device mentioned in clauses (iii) and (iv) an additional safety valve having a capacity to release all steam, vapour or gas without under pressure rise shall be provided in addition to the one referred to in clause (1)(a).
Provided that it shall be sufficient for the purposes of this sub- rule if the safety valve, pressure guage and stop valve or other suitable effective device are mounted on a pipeline immediately adjacent to the pressure vessel and where there is a range of two or similar pressure vessels in a plant served by the same pressure load, only one set of such mountings need be fitted provided that those cannot be isolated from any of the pressure plant or pressure vessels.

(4) Ever pressure plant in service shall be thoroughly examined by a competent person,-
(a) externally once in every period of six months;
(b) internally, once in every period of twelve months, and
(c) hydraulic test once in a period of four years.

Explanation -
If however by reason of construction of the pressure vessel or pressure plant a thorough internal examination is not possible, it may be replaced by a hydraulic test, which shall be carried out once in every period of two years

I hope this will help you.

Regards,
Shashikant.


From India, Pune
Dear All

As per IS 14489 : 1998(CODE OF PRACTICE ON OCCUPATIONAL SAFETY AND HEALTH AUDIT) following points comes related to Pressure Vessels... Let's have a discussion on these points to bring more understanding on the topic...

Request to forum members to participate and try to answer...

Pressure Vessels (Fired and Unfired)

1. What is fired & Unfired Pressure Vessels?

2. Give details of the plants, piping and vessels which are operated at a pressure greater than the atmospheric pressure?

3. How is it ensured that the working pressure inside the pressure vessels/pressure plants will not exceed their maximum working pressure for which it is designed?

4. What means of isolating the pressure vessels or means to prevent rise in pressure are installed?

5. What standards/codes of practice are adopted for design, fabrication, operation and maintenance of the pressure vessels and records maintained?

5. How are the pressure vessels tested? Give details.

6. Is there any competent person for testing these pressure vessels? Give details.

7. How are the recorded results verified?

8. Give details of safety devices available for these pressure vessels?

9. Whether log book for pressure vessel and pressure plant has been maintained?

From India
Dear SSM
Why not you tried to come up with your view regarding the above mentioned 9 points regarding pressure vessels... Instead of have a try you start another thread...
All are just wishing for a ready made answer from the forum to thier concerns or issues only... Nobody bother into have a fruitfull discussions...
Friends request you to participate into other threads also which is not initiated by you... Let's try to make this forum alive...

From India
dear all (& Dipil)

i'm sharing some details for your questions. however now i'm not covering all the questions... let me try to answer part by part.

1. What is fired & Unfired Pressure Vessels?

Fired pressure vessel

Fired pressure vessel is a pressure vessel which is completely or partially exposed to fire from burners or combustion gases or otherwise heated pressure vessel with a risk of overheating.

examples a.Boiler

Boiler is one or more fired pressure vessels and associated piping systems used for generating steam or hot water at a temperature above 120C.

Any equipment directly connected to the boiler, such as economisers, superheaters and safety valves, is considered as part of the boiler, if it is not separated from the steam generator by means of any isolating valve. Piping connected to the boiler is considered as part of the boiler upstream of the isolating valve and as part of the associated piping system downstream of the isolating valve.

b.Thermal oil heater

Thermal oil heater is one or more fired pressure vessels and associated piping systems in which organic liquids (thermal oils) are heated. When heated by electricity thermal oil heater is considered as an unfired pressure vessel.

Unfired pressure vessel

Any pressure vessel which is not a fired pressure vessel is an unfired pressure vessel.

example a.Heat exchanger

A heat exchanger is an unfired pressure vessel used to heat or cool a fluid with an another fluid. In general heat exchangers are composed of a number of adjacent chambers, the two fluids flowing separately in adjacent chambers. One or more chambers may consist of bundles of tubes.

b.Steam generator

A steam generator is a heat exchanger and associated piping used for generating steam. In general in these Rules, the requirements for boilers are also applicable for steam generators, unless otherwise indicated.


From India, Delhi
further to answer How are the pressure vessels tested? Give details.

ASME code requires visual inspection of parts as they are received, after cutting and during fabrication, and after fabrication.

NON-DESTRUCTIVE EXAMINATION METHODS

Of the various conventional and advanced nondestructive examination (NDE) methods, five are widely used for the examination of pressure vessels and tanks by certified pressure vessel inspectors. The names and acronyms of these common five methods are:

1. VT - Visual Examination Test,

2. PT - Liquid Penetrant Test,

3. MT - Magnetic Particle Test,

4. RT - Gamma and X-ray Radiography Test, and

5. UT - Ultrasonic Test.

VT, PT and MT can detect only those discontinuities and defects that are open to the surface or are very near the surface. In contrast, RT and UT can detect conditions that are located within the part. For these reasons, the first three are often referred to as surface examination methods and the last two as volumetric methods.

VISUAL EXAMINATION (VT)

A visual examination is easy to conduct and can cover a large area in a short time.

It is very useful for assessing the general condition of the equipment and for detecting some specific problems such as severe instances of corrosion, erosion, and hydrogen blistering. The obvious requirements for a meaningful visual examination are a clean surface and good illumination.

LIQUID PENETRANT TEST (PT)

This method depends on allowing a specially formulated liquid (penetrant) to seep into an open discontinuity and then detecting the entrapped liquid by a developing agent. When the penetrant is removed from the surface, some of it remains entrapped in the discontinuities. Application of a developer draws out the entrapped penetrant and magnifies the discontinuity. Chemicals which fluoresce under black (ultraviolet) light can be added to the penetrant to aid the detectability and visibility of the developed indications. The essential feature of PT is that the discontinuity must be open, which means a clean, undisturbed surface.

The PT method is independent of the type and composition of the metal alloy so it can be used for the examination of austenitic stainless steels and nonferrous alloys where the magnetic particle test is not applicable.

MAGNETIC PARTICLE TEST (MT)

This method depends on the fact that discontinuities in or near the surface perturb magnetic flux lines induced into a ferromagnetic material. For a component such as a pressure vessel where access is generally limited to one surface at a time, the prod technique is widely used. The magnetic field is produced in the region around and between the prods (contact probes) by an electric current (either AC or DC) flowing between the prods. The ferromagnetic material requirement basically limits the applicability of MT to carbon and low-alloy steels.

The perturbations of the magnetic lines are revealed by applying fine particles of a ferromagnetic material to the surface. The particles can be either a dry powder or a wet suspension in a liquid. The particles can also be treated to fluoresce under black light. These options lead to variations such as the wet fluorescent magnetic particle test (WFMT).

MT has some capability for detecting subsurface defects. However, there is no easy way to determine the limiting depth of sensitivity since it is highly dependent on magnetizing current, material, and geometry and size of the defect. A very crude approximation would be a depth no more than 1.5 mm to 3 mm (1/16 in to 1/8 in).

A very important precaution in performing MT is that corners and surface irregularities also perturb the magnetic field. Therefore, examining for defects in corners and near or in welds must be performed with extra care. Another precaution is that MT is most sensitive to discontinuities which are oriented transverse to the magnetic flux lines and this characteristic needs to be taken into account in determining the procedure for inducing the magnetic field.

RADIOGRAPHY (RT)

The basic principle of radiographic examination of metallic objects is the same as in any other form of radiography such as medical radiography. Holes, voids, and discontinuities decrease the attenuation of the X-ray and produce greater exposure on the film (darker areas on the negative film).

Because RT depends on density differences, cracks with tightly closed surfaces are much more difficult to detect than open voids. Also, defects located in an area of a abrupt dimensional change are difficult to detect due to the superimposed density difference. RT is effective in showing defect dimensions on a plane normal to the beam direction but determination of the depth dimension and location requires specialized techniques.

Since ionizing radiation is involved, field application of RT requires careful implementation to prevent health hazards.

ULTRASONIC TESTING (UT)

The fundamental principles of ultrasonic testing of metallic materials are similar to radar and related methods of using electromagnetic and acoustic waves for detection of foreign objects. The distinctive aspect of UT for the inspection of metallic parts is that the waves are mechanical, so the test equipment requires three basic components.

* Electronic system for generating electrical signal. * Transducer system to convert the electrical signal into mechanical vibrations and vice versa and to inject the vibrations into and extract them from the material. * Electronic system for amplifying, processing and displaying the return signal.

Very short signal pulses are induced into the material and waves reflected back from discontinuities are detected during the receive mode. The transmitting and detection can be done with one transducer or with two separate transducers (the tandem technique).

Unlike radiography, UT in its basic form does not produce a permanent record of the examination. However, more recent versions of UT equipment include automated operation and electronic recording of the signals.

Ultrasonic techniques can also be used for the detection and measurement of general material loss such as by corrosion and erosion. Since wave velocity is constant for a specific material, the transit time between the initial pulse and the back reflection is a measure of the travel distance and the thickness.

CYLINDER TESTING METHODS:

The four main cylinder testing methods are:

• Water Jacket Method

• Direct Expansion

• Proof Pressure Method

• Ultrasonic Testing Method


i will answer one by one at the earliest.......

From India, Delhi
Dear KVS Thanks a lot for your inputs into the thread... It’s really informative... Awaiting for your rest of the reply’s... Whenever get time do share your expertise with us...
From India
Dear Mr.Dipil, Thank you for your thread requiring detailed insight on PVs. Dear Mr.Shashikant Fand and Mr.KVS. Thanks a lot for your valuable inputs on PV. Reagrds, SSM
From India, Madras
Dear Mr.Dipil

I am attempting to answer to few of your questions listed under PVs as below:

3. How is it ensured that the working pressure inside the pressure vessels/pressure plants will not exceed their maximum working pressure for which it is designed?

Your question is answered in TN factories act Rule(56), sub rule(4).

"(a) a suitable safety valve or other effective pressure relieving device of adequate capacity to ensure that the maximum permissible working pressure of pressure vessel shall not be exceeded. It shall be set to operate at a pressure not exceeding the maximum permissible working pressure and when more than one protective device is provided ,only one of the devices need be set to discharge at a pressure not more than 5 percent in excess of the maximum permissible working pressure.

(b) a suitable pressure gauge with a dial range not less than 1.5 time the maximum permissible working pressure, easily visible and designed to show at all times the correct internal pressure and marked with a prominent red mark at the maximum permissible working pressure of the pressure vessel."

4. What means of isolating the pressure vessels or means to prevent rise in pressure are installed?

"(d) a suitable stop valve or valves by which the pressure vessel may be isolated from other pressure vessels or plant or source of supply of pressure. Such a stop valve or valves shall be located as close to the pressure vessel as possible and shall be easily accessible."

6. Is there any competent person for testing these pressure vessels? Give details.

With respect to testing, the external testing of once in every 6 months can be done by Inspector of Factories after making stipulated payment to treasury. Internal and hydrostatic test can be done by competent authorities.

8.Give details of safety devices available for these pressure vessels?

Sub rule(4)

(a) Pressure relieving valve

(e) drain cock

Sub rule(5)

(a) Pressure reducing valve

(b) "To protect the pressure vessel in the event of failure of the reducing valve or device at least one safety valve having capacity sufficient to release all the steam, vapour or gas without undue pressure rise as determined by the pressure at the source of supply and the size of the pipe connecting the source of supply, shall be fitted on the low pressure side of the reducing valve."

Hope these helps you to some extent. If you find answers for rest of the questions pls share.

Regards,

SSM

From India, Madras
Dear Mr.Dipil, Pls find the attached file contains details on pressure vessel testing. This will also be helpful to you I suppose. Regards, SSM
From India, Madras

Attached Files
File Type: pdf Pressure vessel Inspection.pdf (673.1 KB, 1904 views)


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