• Easytek can carry out a Visual inspection and Hydrostatic Test on most makes and models of cylinders.

• Our volumetric hydrostatic test system is capable of testing cylinders up to 680 Bar (10000 psi).

• We have a range of adapter to fit almost any cylinder thread size. E.g M25, M18, DAN Oxygen cylinders, taper threads etc.

• We keep copies of the latest  Cylinder testing standards on our premises, not just the free Luxfer Visual Inspection Guides. This ensures that we can fully test your cylinder to the correct standard.

• Easytek uses the most advanced cylinder testing tools available when carrying out a visual inspection such as the Visual Plus 3 Eddy current NDT tester and a ultrasonic thickness gauge. (the only cylinder testing station in Thailand to use this equipment).

Cylinder testing the Mythbusters way. 

Reasons why to get your cylinder tested?

1. Safety
2. Safety
3. Safety
4. Detect potential faults early and rectify the cause of the problem before the cylinder fails the test. Preventative maintenance is more cost effective than corrective maintenance.
5. Ensure your customers are using equipment that is being  correctly maintained in accordance with the manufactures recommendations and the law.

Most cylinders fail whilst being filled.

A 200 bar scuba cylinder contains an explosive force that has the energy to destroy your compressor room and maim or kill any one within the vicinity. A visual inspection and hydrostatic test is a lot less expensive than buying new compressors.

The power of Maths.

The force applied to the cylinder valve can be calculated using some relatively simple maths.

force (kg) = pressure(kg/cm2)  x area (cm2).

If we take a 200 bar cylinder fitted with a 25mm (metric makes the maths easier) valve we can work out the force that is being applied to the valve.

Force = (200x1.02) x (3.142 x(1.25 x1.25)) = 100151kg

Therefore it can seen from the maths that there is a one metric ton of force being applied to the cylinder valve.  

Part of the visual inspection process is to ensure that the threads of the valve and cylinder meet the required safety standards by checking the threads with a thread gauge.

Rectify the problem early.

Approximately 80% of the cylinders that fail whilst being inspected at Easytek fail due to internal corrosion. By getting your cylinders  visually inspected regularly it is possible to identify corrosion build up inside the cylinder before it fails the test and rectify the cause of the corrosion. Corrosion inside a cylinder is caused by moisture entering the cylinder; under high pressure the moisture inside the cylinder starts to rapidly cause a build up of aluminium hydroxide. The moisture can only enter the cylinder through the compressor, unless of course the cylinders are stored without valves or any  pressure. 

By regularly getting your cylinders inspected you can not only detect cylinder faults before they become a problem but also possibly detect any potential problems with your compressor which also may be rectified before becoming a problem.

How to determine if your cylinder needs testing.

Most of the major cylinder manufactures recommend getting your cylinder testing if one or more of the following conditions apply.

Visual Inspection.

The visual inspection process is the most important part of the cylinder testing, cylinders rarely fail the hydrostatic test but multitudes fail the visual inspection.

During the inspection the inspector will be looking for any cuts, gouges,  dents, bows and bulges. The inspector will also be checking the cylinder for corrosion, cracks, folds and valleys in the crown.

(crack  propagating from a  fold. Click on the photo for a larger image.)

All cylinder & valve threads are tested with a Go No/Go thread gauge. This ensures that not only are the valve and the cylinder the same thread specification and form but also that the thread is within the required tolerance as per the applicable standard.

It is not the goal of the inspector to fail the cylinder but to ensure that the cylinder is safe for the next period of use.

Easytek  is the only SCUBA cylinder testing station in Thailand to use an Ultrasonic Thickness Gauge when carrying out a Visual Inspection. This allows us to accurately test your cylinder to the standards for a cylinder of known wall thickness. Without an Ultrasonic thickness Gauge the standard for a cylinder of unknown wall thickness must be used.

We are also the only cylinder test station to use the Visual Plus3 Eddy current device when carrying out a visual inspection on aluminium cylinders.

Cylinders made from 6351 alloy are prone to suffer from Sustained Load Cracking in the thread area. It is a mandatory requirement for all cylinders made from 6351 to be Eddy Current tested.

Although 6061 alloy  cylinders are not prone to Sustained Load Cracking they can still exhibit cracks in the thread.  The Visual Plus3 Eddy Current devise is the only device recommended for use on 6061 alloy cylinders. Visual Plus3 report of a 6061 cylinder with cracks in the thread.

Hydrostatic Testing 

Compressed gas cylinders are designed with a safety factor that is measured by testing the cylinders with one of the following methods:

• Non Water Jacket Volumetric Testing

• Water Jacket Volumetric Testing

• Proof Pressure Testing 

Easytek has a volumetric water jacket hydrostatic test system capable of testing cylinders up to 10 000 psi 680 Bar.

Our hydrostatic test system has a working gauge, a master gauge and calibrated test cylinder.

The working gauge is checked against the master gauge monthly  and a calibration error chart is produced. This chart lists the error that the working gauge is reading and an adjustment is made during test to ensure that the correct test pressure is applied. 

At the beginning of every day the hydrostatic test system is in use the system is checked by hydrostatically  testing a calibrated cylinder. If the test results are not accurate then the system is fully checked for a fault and the calibrated cylinder is retested until the fault is rectified.

By having a calibrated working gauge and a calibrated test cylinder you can be sure that should a cylinder fail the hydrostatic test (cylinders rarely fail the test) it is not due to faulty equipment.

Easytek has a complete range of adapters and tools to be able to test most makes of  Scuba diving and SCBA cylinders. If you have cylinders that need testing and the thread size is not listed here please bring them in and we may be able to make an adapter to fit.

• 3/4-14 NPSM
• 7/8-16 NPSM
• G3/4 -14 BSP
• 25-2 mm parallel
• 18-1.5 mm parallel
• 1/2 inch NGT taper
• 0.6 inch taper
• 0.715 inch taper
• 19.8mm taper

Scuba cylinders.

In Thailand scuba cylinders are required to undergo a hydrostatic test every 3 years in accordance to the Thai testing Standard. As this standard is only written in Thai language and widely unknown most cylinder testers follow the standard associated by the Cylinder manufacturer.  DOT for USA cylinders, and EN cylinder testing standards for cylinders from Europe, both the DOT and EN standards require the cylinder to be tested every 5 years.

 A cylinder that is out of date cannot be filled by law.

SCBA cylinders.

There are a variety of SCBA cylinder manufacturing specifications and the hydrostatic test requirements for each cylinder may vary. For SCBA cylinder testing the manufactures requirements and local standards must be consulted. In Thailand the testing requirements for SCBA cylinders are as follows.

Manufacture	Specifications	Test Period	Life	Test pressure
Luxfer	DOT SP10915	5 years	15	3/2 WP*
Luxfer	DOT SP14232	5 Years	30	3/2 WP*

* Test pressures are based on USA testing procedures, the test pressures vary from country to country.

The Hydrostatic Test Process. 

A compressed gas cylinder is pressurized with water to a pressure that is higher than its normal working pressure (usually 5/3 working pressure but can be different) where the cylinder may: 

A) Do nothing which is the best case, 

B) Stretch slightly within the required tolerance, which is acceptable, 

C) Stretch beyond the tolerance, which fails the cylinder from service, or

D) Explode inside the test jacket. 

The test jacket is designed to safely contain the force of the hydrostatic explosion. The force of a hydrostatic explosion or burst is minimal compared to a pneumatic explosion due to the use of water, not air as a pressure medium. This is due to the minimal compressibility of water vs.the highly compressibility of the gas that the cylinder normally contains.

Cylinders should receive a complete external and internal visual inspection prior to a hydrostatic test as per the cylinder manufactures testing standards.

A typical hydrostatic test at Easytek is comprised of the following steps:

1.      The cylinder is filled with water

2.      It is then placed inside a test jacket that is full of water and connected to the high pressure hydraulic pump.

4.      The lid is closed and the water jacket is filled completely with water until no air is present. (Air is compressible and will give a false readings.)

5.     A zero expansion point is set by allowing more water to enter the water  jacket and the displaced water will rise up the burette. 

6.      The pressure inside the cylinder is raised to the required test pressure (up to 7350 PSI) for a required time, causing the cylinder to grow in size. As the cylinder expands the displaced water inside the jacket is forced up the burette.The cylinder expansion at test pressure is then recorded. 

7.      The pressure is released, and the cylinder should return to a required percentage of its original size. When the de-pressurized cylinder expansion is stable, a permanent expansion value is recorded. 

8.      The cylinder is drained of water and dried.

9.      The cylinder is then re-valved and stamped.

The amount of water forced out of the test jacket as a result of the cylinder's growth during the pressurization is measured in the burette and compared to the amount of water left in the burette when the cylinder is depressurized. The amount of water left in the burette corresponds to the amount that the cylinder was permanently deformed by the test pressure. If the cylinder returns a percentage of expansion as set by the relevant testing standards the cylinder passes the test.

A cylinder will fail the test if either:

a) The water level in the burette continues to rise while the test pressure is applied. This could be due to a leak from inside the cylinder to the water in the jacket, or to a continual expansion of the walls of the cylinder, both of which are reasons to fail the cylinder.         

b) The cylinder stretched and with the pressure released does not return to its original size (or close to it), it would mean the metal of the cylinder is not resilient enough to be considered safe for use. Depending on the testing standard the burette cannot have more than 10 percent of the displaced water remaining after the pressure is released. E.G. If the expansion displaced is 100 cc of water, after the pressure is released it must have a reading of 10cc or less to pass the test.

Cylinders that pass both the visual inspection and the hydrostatic test may be stamped with the re-qualification marks, and can be filled and offered for transportation for 3-10 years depending on the type of cylinder. 

Different cylinder testing standards have different pass/condemn criteria, this is why at Easytek we hold on our premises multiple testing standards for most makes of cylinders.

 Cylinder Testing  Standards.

Thai

• Thai Industrial Standard 358.2531

DOT

The requirements for visual inspection and testing of cylinders is contained within the Code of Federal regulations Title 49 TRANSPORTATION.

• CGA C-1      Methods for Hydrostatic Testing of Compressed Gas Cylinders
• CGA C-6.1   Standards for Visual Inspection of High Pressure Aluminum Compressed Gas Cylinders
• CGA C6 Standards for Visual Inspection of High Pressure Steel Compressed Gas Cylinders

CGA cylinder testing standards and publications.

EN

• EN1968: 2002  Transportable gas cylinders. Periodic inspection and testing of seamless steel gas cylinders.
• EN1802: 2002 Transportable gas cylinders. Periodic inspection and testing of seamless aluminium alloy gas cylinders.

Cylinder inspection / test costings

Visual Inspection Only.

The visual inspection breaks down into the following processes;

1. Valve removal. Easytek charges for a valve removal /refit as sometimes when the valve is corroded into the cylinder this can be the most difficult part of the visual inspection process.
2. The cylinder is visually inspected.
3. Depending on the outcome of the inspection either of the following conditions will apply:

• Failed cylinders will be rendered unusable I.A.W the relevant testing standards.
• The process will continue as below.
  

4. The valve is refitted with a new pillar valve o-ring.
5. The cylinder is filled to its working pressure and tested for leaks.
6. A current visual inspection sticker is applied to the cylinder.
   

The following are extra processes that might be carried depending on the condition of the cylinder.

• Cylinder cleaning - corrosion removal, oils and other contaminants 
• Paint Stripping 
• Cylinder Tumbling - certain conditions such as excessive corrosion will require the cylinder to be tumbled.

Basic Visual Inspection Charge Estimate.

Valve Removal / Refit *	200THB
Visual Inspection	250THB
Pillar Valve O-ring *	35THB
Air Fill *	150THB
Total  exc. VAT	635THB

Hydrostatic Test

The hydrostatic test consists of the following processes:

1. Valve removal. Easytek charges for a valve removal /refit as sometimes when the valve is corroded into the cylinder this can be the most difficult part of the visual inspection process.
2. The cylinder is visually inspected. It is compulsory for a visual inspection to be carried out at the time of hydrostatic test. If the cylinder fails the visual inspection the process stops here and you are charged only for  processes carried out so far.
3. The cylinder undergoes a Hydrostatic Test.
4. Depending on the outcome of the test either of the following conditions will apply:

• Failed cylinders will be rendered unusable I.A.W the relevant testing standards.
• The process will continue as below.

5. The cylinder is dried.
6. A stamp mark is applied to the cylinder to show that it has had a hydrostatic test carried out. This marking contains the date on which the test was carried out and the test stations unique identifying mark.
7. The valve is refitted with a new O-ring.
8. The cylinder is filled with air and pressure tested.

Hydrostatic test Charge Estimate.

Valve removal / Refit *	200THB
Hydrostatic test & visual inspection	660THB
Pillar valve 0-ring *	35THB
Air fill *	150THB
Total exc VAT.	1045THB

  Note.

    * Cylinders can be brought in for test with out valves fitted.  If the cylinder does not contain a valve then the items listed will not be charged for. Cylinders without valves can not be leak tested and thus cannot be guaranteed leak free.

Cylinders with out valves are subject to a 500THB deposit per cylinder.

Easytek takes no responsibility for the serviceabilty of the valve.

Extra processes that may need to be carried out depending on the condition of the cylinder.

Internal cleaning	50THB
External paint stripping	250THB
Cylinder tumbling 1hr (extra hours are charged at 200THB/Hr)	350THB
Valve service (not including parts)	325THB
Oxygen cleaning of cylinder & valve	1000THB

© Samui Easytek Co., Ltd. (Pattaya)