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Top 20 Checklist For Selecting A Closed Loop Chemical Sampling System

hastelloy sampling system

What is closed loop chemical sampling?

Closed loop chemical sampling is the taking of a sample from the process into a sealed container without exposing the product to the environment, then safely venting this container to a suitable outlet – preventing a build up of pressure in the container.

Sample too hot…? Use a cooler 

When sampling using a closed loop sampling technique all product is contained and no product escapes in an uncontrolled manner all product handled is either returned to the process or vented in a controlled manner. Closed loop sampling of liquids can be achieved using the unique Dopak principle.

When designing a closed loop sampling system the following checklist should be considered:

  1. What is the sample point identity/location/tag number
  2. What is the process liquid
  3. What is the process pressure
  4. What is the process temperature
  5. What is the ambient temperature
  6. How should the sampler ideally operate
  7. Is a suitable vent location available
  8. What is the process connection type
  9. What is the process connection size
  10. What is the required material of construction for the closed loop sampler
  11. Is an enclosure required for weather protection?
  12. Is heating required
  13. Is cooling required
  14. Is insulation required
  15. What is the required sample volume
  16. What type of sample container is required
  17. What size of sample container is required
  18. What material should the sample container be?
  19. How will the sample container be transported
  20. How will the sample be disposed of?

All 20 of these points should be considered by all influencers on a chemical plant design, these include;

  • Project engineering
  • Laboratory
  • Process Engineering
  • Analyser/instrument engineering
  • Maintenance engineering
  • Plant safety team
  • Government

A correctly specified sampling system will ensure:

  • Less product waste
  • Less waste treatment costs
  • Safer sampling for the operator
  • Safer plant operations
  • Less environmental pollution
A chemical plants QA department will also benefit from a correctly specified  sampling system. These benefits may include:
  • Greater customer confidence in the product to be delivered
  • Improved standardization of product
  • Simplifying the business
  • Raising performance of suppliers
  • Improved manufacturing efficiency and profitability
  • Ensures contents labeling compliance
  • Improved employee morale and performance
An effective closed loop chemical sampling system should:
  • Be safe and simple to operate
  • Be representative
  • Minimize pollution and contamination
  • Be available for both pipeline and vessel sampling
  • Be suitable for a wide range of process pressure and temperature characteristics

Typical applications include:

  • Sampling hydrocarbons
  • Sampling corrosive and hazardous liquids
  • Sampling viscous liquids and slurries
  • Sampling high purity liquids
  • Sampling liquefied gases
  • Sampling gases
  • Sampling high vapor phase liquids

How is containment achieved?

The sampler is installed directly into a process line/re-circ line and a sample is drawn from the process into a sample container.

Containment is achieved by using a needle assembly which pierces a self sealing diaphragm (Septum) placed between the bottle and its cap. This sealed bottle can then be taken to the laboratory for analysis.

Even simple closed loop sampling systems minimize or even eliminate dead volumes (old product). Various purge options can also be employed to further ensure representative sampling.

Dead volumes can be eliminated altogether by using the fixed volume closed loop sampling systems.

Specifying a Dopak system

Request and complete a specification sheet to provide all the necessary details to the Dopak engineers. This can be requested via or the UK experts for Dopak – Derwent James Ltd. A representative from Derwent James Ltd can visit your UK site and assess the sampling application and produce a proposal.

Dopak sampling systems are industry leaders in the design of closed loop sampling systems. Dopak sampling systems should be selected for your next closed loop sampling application because;

  • Dopak design innovative sampling solutions, not just valves
  • Dopak have vast industry experience
  • Dopak is accepted world wide throughout the chemical, petrochemical and pharmaceutical industries
  • Dopak has the ability to also custom build a sampler to meet your project specification
  • Dopak have over 25,000 systems installed worldwide and are represented across the globe by industry experts. In the UK Derwent James Ltd have over 15 years experience in the design of closed loop sampling systems.

For further information or to discuss your closed loop chemical sampling applications then contact the exclusive UK representatives for Dopak –

Top 20 checklist for selecting a closed loop chemical sampling system
Article Name
Top 20 checklist for selecting a closed loop chemical sampling system
Checklist for selecting the right closed loop chemical sampling system.
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Derwent James Ltd
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