Question 1

What is the difference between standard and constant-pressure sampling cylinders?

Accepted Answer

Standard cylinders are simple sealed containers that hold the sample at whatever pressure results from filling conditions. When volatile liquids (LPG, naphtha, gasoline) are sampled in standard cylinders, the pressure drops as the sample cools during transport, causing light ends to vaporize and corrupting the sample composition. Constant-pressure (piston) cylinders use an internal spring-loaded piston that maintains the sample at process pressure, preventing phase change and preserving the original composition for accurate lab analysis.

Question 2

How often do sampling cylinders need re-certification?

Accepted Answer

Most jurisdictions require hydrostatic re-testing every 5 years for standard steel sampling cylinders. Cylinders in aggressive service (sour/H2S, high-temperature cyclic, corrosive chemicals) may require more frequent inspection — typically annually or biannually. DOT and TPED certified cylinders have specific re-test intervals defined by the certification standard. Always maintain re-test records for regulatory compliance.

Question 3

What certifications are needed for international shipment of sample cylinders?

Accepted Answer

For US shipments: DOT special permit or DOT-3A/3AA certification. For EU: TPED (Transportable Pressure Equipment Directive) 2010/35/EU. For China: GB 5099. For international air transport: IATA Dangerous Goods Regulations compliance. Wanan cylinders carry ASME certification plus DOT, TPED, or GB certification depending on the destination market.

Question 4

Can sampling cylinders be used for high-pressure gas sampling?

Accepted Answer

Yes. Wanan manufactures gas sampling cylinders rated up to 30 MPa (4,500 PSI) for high-pressure natural gas and process gas sampling. These cylinders feature single-end or double-end valve configurations with pressure-rated connections. For gas sampling, always verify the cylinder's design pressure exceeds the maximum process pressure by an adequate safety margin (minimum 1.5x).

參數	Standard Cylinder	Piston (Constant-Pressure)
體積	150 mL - 4 L	300 mL - 1 L
Design Pressure	10 - 30 MPa (1,500 - 4,500 PSI)	10 - 20 MPa
材質	316L SS seamless tube	316L SS + PTFE piston seal
Valve Type	Double-end needle valve	Double-end needle valve + vent
認證	ASME, DOT, TPED, GB 5099	ASME, DOT, TPED
Hydrostatic Test	1.5x design pressure	1.5x design pressure

Sampling Cylinders: Technical Overview

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