Proper Orientation of Needle Valves Installed On Sampling Assemblies


As industrial production processes become increasingly complex, the standards for sample analysis grow more stringent, with a greater emphasis on safe sampling. Consequently, sampling systems have evolved from simple, rudimentary methods to safe and reliable grab sampling techniques. FITOK sampling systems are classified into two types based on the sample container: bottle configuration and cylinder configuration. Bottle configuration sampling systems collect samples into containers under normal pressure, while cylinder configuration sampling systems collect samples into containers under process pressure. Sampling assemblies are a crucial component of cylinder configuration sampling systems, designed for the sampling of liquefied gases, liquids, and gases that are characterized by high temperature, high pressure, corrosiveness, toxicity, high volatility, and environmental harm. They are widely used in various fields such as chemistry, petroleum, pharmaceuticals, and environmental protection.


FITOK Sampling Systems


Most Proper Orientation for Installing Needle Valves on Sampling Assemblies



Sampling assemblies primarily consist of sample cylinders, needle valves, and quick-connects. They can be customized to meet specific customer needs. Needle valves are typically installed at both ends of the sample cylinder to control the flow of media in and out of the cylinder. Generally, needle valves are installed with the inlet connected to the cylinder and the outlet connected to a quick-connect (i.e., with the flow arrow pointing away from the cylinder). Therefore, some people may wonder why needle valves are installed in a direction away from the cylinder (indicated by the flow arrow), instead of pointing towards the cylinder or in another direction.


The Assembly Structure of the FITOK Sample Cylinder

The Structure of FITOK Sampling Assemblies


Before answering this question, let's first understand the basic structure of a needle valve. The flow of fluid is controlled by the opening and closing action between the stem tip and the seat, with the stem tip and stem rising and falling as the handle is rotated. In this process, the most vulnerable point for fluid leakage is the stem seal. Therefore, to ensure that the valve does not leak, structures such as washer, O-ring, backup ring, and packing bolt are installed between the stem and handle to achieve maximum sealing effectiveness. However, even with these measures in place, when the valve is in a closed state, compared to its inlet section, there is still a higher likelihood of leakage in the space connected to the stem (i.e., its outlet section). When pressure exists on the bottom surface of the seat (inlet section), valves are typically most effective at containing pressure while minimizing stem leakage.


The Structure of FITOK ND Series Needle Valves

The Structure of FITOK ND Series Needle Valves


Now let's go back to the original question: why is the installation direction for a needle valve (the flow arrow) directed away from the cylinder? First, we need to understand that the main function of a sampling assembly is to transport collected samples to the laboratory safely and without leaks, with cylinder valves remaining in the closed position after sampling systems have collected the samples. In other words, sampling assemblies should store medium under certain pressure for transportation. Therefore, the needle valve connected to the cylinder must have excellent sealing performance to ensure that the medium inside does not leak. From our understanding of the basic structure of a needle valve mentioned above, we know that in its closed state, the sealing performance in the inlet section is optimal. Consequently, for optimal installation, it is recommended that the inlet be connected with the cylinder, with the flow arrow pointing away from it.


FITOK Sampling Systems and Sampling Assemblies



FITOK boasts extensive experience in designing and manufacturing sampling systems. We offer a wide selection of series and models, as well as customizable designs tailored to customer needs and specific working conditions to meet customer needs as much as possible.


Highlights of FITOK Sampling Systems


  • With a wealth of experience in sampling systems, we provide customizable designs tailored to customer needs and actual working conditions, as well as one-stop solutions including system design, assembly, training, filed service, and spare parts supply, etc.
  • Key components, such as sample cylinders, needle valves, quick-connects, fittings, hoses, tubing, and coolers, are all manufactured and tested in FITOK’s factory. Superior product quality ensures reliable and safe sampling systems.
  • With sufficient inventory of raw materials and finished products, FITOK ensures swift delivery.
  • Material options include 316L stainless steel, 2507 super duplex steel, Hastelloy and Inconel, etc. Materials that meet NACE MR0175 standards are available for sour service.
  • Welding procedure (WPS/QPR/WQT) has received approval from Lloyd's Register.
  • Fittings used for FITOK sampling systems, such as 6D series tube fittings, have passed all standard tests and supplemental tests under ASTM F1387 standards.
  • FITOK sample cylinders are designed and manufactured in compliance with 49 CFR regulations issued by the U.S. Department of Transportation, ensuring excellent safety, reliability, and extended service life. TPED and DOT cylinders are also available, with factory test reports provided for the complete set of sampling assemblies.
  • Internally sandblasted cylinders provide smooth inner surfaces, reducing impurity residues and facilitating cleaning.
  • SilcoNert® 2000 (Sulfinert®) coated cylinders are available, offering a stable passivation layer that withstands ppb-level sulfides and mercury in petroleum samples for extended storage periods.

Related Articles:

This website uses cookies in order to improve your user experience. By clicking "Accept" or continuing to use our website, you consent to our use of cookies as defined in this Cookie Policy. Cookie Notice and Disclosure

Last updated June 16, 2020


Like many companies, FITOK Group, its subsidiaries and its authorized sales and service centers (collectively, "FITOK" or "we, " "us, " or "our") use "cookies" and similar tools on and any authorized sales and service center website (collectively, the "Sites") to facilitate and improve your online experience. This Notice explains how we do that.  
What are cookies?
A cookie is a small file or piece of information which is downloaded to your computer or device when you visit the Sites, and then sent back to the Sites in order to allow us to recognize your computer or device later. Although certain cookies may contain personal data – for example, if you click to "remember me" when logging in, a cookie may store your username – most cookies won’t collect personal data that identifies you. Rather, most cookies collect general information, such as how users arrive at and use the Sites, or a user’s general location. By collecting this information, cookies help to analyze web traffic and allow web applications to respond to you as an individual. The web application can tailor its operations to your needs, likes and dislikes by gathering and remembering information about your preferences.
How do we use cookies?
Our Sites utilize cookies for several purposes, including the storage of information required to determine how to properly deliver content to your computer or device. A cookie is provided to all visitors to, regardless of whether you register with an authorized sales and service center.
For users who do register with an authorized sales and service center, a profile containing the registration information is generated by our website, and used for several purposes:
  1. to match you with content that is associated with your interests and to direct you to additional resources and tools that can save you time;
  2. to enable a fast response for service or follow-up request from our website;
  3. to verify your identity;
  4. to send you an electronic newsletter, other information and content; and
  5. to contact you when necessary.
What kinds of cookies do we use?
We may use cookies for a number of purposes:
  1. Session Cookies These cookies are used 'in-session' each time you visit and then expire when you leave a Site or shortly thereafter.  They are not stored on your computer or device permanently, do not contain any personal data and help by minimizing the need to transfer personal data across the internet. These cookies can be deleted or you can refuse to allow their use, but this will hamper the performance and your experience in using the Sites. These cookies also take time stamps that record when you access the Sites and when you leave the Sites.
  2. Tracking Cookies – These cookies enable us to recognize repeat visitors to the Sites. By matching an anonymous, randomly generated identifier, a tracking cookie keeps track of where a user of the Sites came from, what search engine they may have used, what link they clicked on, what keyword they used and where they were in the world when they accessed the Sites. By monitoring this data, we can make improvements to the Sites.
  3. Persistent Cookies – This type of cookie is saved on your computer or device for a fixed period (sometimes for a few hours, sometimes for a year or longer) and is not deleted when the browser is closed. Persistent cookies are used where we need to remember who you are for more than one browsing session. For example, this type of cookie can be used to store your preferences, so that they are remembered for the next visit to the Sites.
  4. Performance or Analytical Cookies Performance cookies are used to analyze how the Sites are used and to monitor their performance, which allows us to improve your experience in using the Sites. These cookies help us to tailor the content of the Sites to reflect what the Site users find most interesting and to identify when technical issues with the Sites arise. We may also use this data to compile reports to help us to analyze how Sites are used, what the most common issues are and how we can improve the Sites.
Can the Cookies be blocked?
Yes. Most internet browsers are initially set up to automatically accept cookies. You can, however, change your browser settings to block cookies or to alert you when cookies are being sent to your device. There are a number of ways to manage cookies. Please refer to your browser instructions or help screen to learn more about how to adjust or modify your browser settings. Instructions for blocking or allowing cookies in popular web browsing software can be found by clicking the following links:
Internet Explorer
Google Chrome
Microsoft Edge
Please be aware that if you disable the cookies that we use, this may impact your experience while on the Sites. For example, some features and services on the Sites may not work properly because we may not be able to recognize and associate you with your FITOK account(s). In addition, the offers we provide when you visit us may not be as relevant to you or tailored to your interests.