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Liquid and Gas Sampling  

Sampling Hydrofluoric Acids (HF)

Hydrofluoric Acids Sampling (HF) Diagram
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At Biar Inc., we design and manufacture valves for pure or concentrated aqueous hydrofluoric acid sampling applications. Hydrofluoric acid is used in the production of numerous products such as pharmaceutical compounds, as well as in hydrofluoric acid alkylation units that are found in the petrochemical refining industry. With such widespread use, especially in applications within the pharmaceutical industry, precise sampling of hydrofluoric acid streams is imperative. However, hydrofluoric acid is an extremely dangerous chemical and is known to destroy skin, subdermal tissue, and bone, as well as damage eyes to the point of vision loss, on contact. Deaths have been reported as a direct result of acid burns that involved as little as 2.5% of the body surface area. Obviously, when sampling a chemical this lethal, no exposure to the outside environment or operator is to be allowed.

To overcome these challenges, a material with a strong resistance to acids must be selected. For some alkylation solution sampling applications, 316L stainless steel can be used, but for higher acid concentrations, specialty HSLA alloys such as Monel 400, Alloy20, or Hastelloy are typically chosen. The exact material of construction (MOC) is ultimately chosen by the customer based on the nature of their processing stream. For hydrofluoric acid sampling, we recommend a multi-function metallic valve with a bellows type seal, stuffing box and leak detection port.

Multi-function valves are designed for the easy removal and cleaning of the adapter, allowing the customer to clean the valve after every sampling procedure, without the use of. The bellows type seal reduces the risk of leakage and minimizes valve maintenance, while the stuffing box provides a secondary containment chamber as an additional safeguard against leaks. The leak detection port helps the operator identify any potential issues with the bellow before a leak ever occurs. Hydrofluoric acid sampling valves are also equipped with a spring-to-close actuator, called a Magic Hand Wheel, that immediately snaps shut if the operator’s hand slips from the valve. This prevents leakage of the acid into the outside environment if an accident were to occur.

One of the most important aspects of our sampling valve design is that our valves have absolutely no dead space, meaning that no sample material is left in the valve after the sample has been transferred. While in practice, a very minute trace of the material sometimes remains between the valve and container, this material can easily be removed with a bayonet adapter that is fitted with a rinsing connection. Because transporting hydrofluoric acid to the laboratory in its pure state can be dangerous, we offer an optional neutralization chamber design wherein the sample is mixed with a neutralization agent to make it safer for transport. The final safety feature in this design is a safety plug that acts as a secondary containment chamber when the valve is not in use. By taking the properties of this lethal chemical into account, we were able to develop a robust design with several redundant safety features to ensure the safety of the operator during the sampling process. For additional information about the valves we have designed specifically for sampling hydrofluoric acid streams, contact us directly.

Hydrofluoric Acid is a lethal and extremely dangerous chemical. It will destroy skin, the tissue beneath the skin and bones. It will damage the eyes (even loss of vision) upon contact. Deaths have been reported from concentrated acid burns involving as little as 2.5% Body Surface Area (BSA).
We have experienced two types of HF Sampling:

  1. Pure HF or Hydrofluoric Acid, Aqueous (70%) (see PDF document Material Safety Data Sheet (MSDS) - Hydrofluoric Acid)
  2. Hydrofluoric acid alkylation - mostly used in refining

Capabilities Applied/Processes
To sample HF, one has to deal with the following challenges:

  • This is a deadly chemical and absolutely no exposure is allowed.
  • For some alkylation application, we have seen Stainless Steel (316L) as acceptable, but for most application specialty alloy such as Monel 400, Alloy20 or Hastelloy ® are required. The material of construction (MOC) is specified by the customer.

 Recommended Sampling System:

  • Multi-function metallic valve
    • With bellows type seal, stuffing box and leak detection port
    • With spring-to-close hand wheel (Magic Hand Wheel)
  • Bayonet adapter
    • Option: with rinsing connection
  • Container
    • With bellows type seal, stuffing box and leak detection port
    • Option: with neutralizing chamber
  • Safety plug

 Explanation:

  • Both the valve and container are 100% dead-space free and in theory, this eliminates all exposure. (see document No Dead space sampling) In practice, a very small amount of product can be trapped between the outlet of the valve and container. To dispose safely of the trapped amount, the bayonet adapter can be fitted with a rinsing connection (see Sampling into container and bayonet with rinsing connection)
  • Transporting HF from the sample point to the lab in its pure state is dangerous. The container can be manufactured with a neutralizing chamber where HF and neutralizing agent can be mixed together to create a safe sample. See  Sampling into a closed container 2 chamber.
  • The bellows type seal in both the valve and container reduces stem leakage chances and improves maintenance
  • The stuffing box (packing) is secondary containment in case of bellows problem
  • The leak detection port can be used to detect bellows problems before the valve leaks
  • The integrated vent connection fitted on all our valves allows the trapped product between the valve outlet and the container to be vented securely using the bayonet adapter with rinsing connection
  • The safety plug is used as secondary containment when the valve is not in use
  • The spring-to-close hand wheel (aka Magic Hand Wheel) adds security
  • Multi-function means the adapter can easily be removed for cleaning purposes and this can be done after each sample very quickly without special tools
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