Critical Maintenance for Closed Loop Grab Sampling Systems(PDF)
Billy Terry, Product Manager SENSOR Sampling Systems
Matthew K. Giunta, Marketing Manager SOR Measurement and Control
Every year, improperly maintained closed-loop grab sampling systems cause preventable injuries, environmental violations, and product quality concerns, all of which come at a cost. Yet these incidents are entirely avoidable. The difference between safe, compliant operation and inconsistent sample results often comes down to understanding and implementing proper maintenance protocols.
This paper examines essential strategies and technical guidance for maintenance technicians and plant engineers to ensure optimal performance, safety, and longevity of closed-loop grab sampling systems.
Maintenance Matters
The stakes are high: In a study conducted by GE, 82% of companies have experienced unplanned downtime in the past three years and 75% of employees recognize they lack knowledge and awareness of when components are due for replacement (Vanson Borne and ServiceMax. After the Fall: The Costs, Causes & Consequences of Unplanned Downtime). For sampling systems specifically, failures can trigger safety incidents, environmental violations, and production quality losses that far exceed the cost of proactive maintenance programs.
Industry leaders recognize that proactive maintenance plans reduce unplanned downtime for sampling system maintenance while achieving fewer defects compared to reactive maintenance strategies.
Safety & Environmental Regulations
Maintenance failures in closed-loop grab sampling systems create immediate safety hazards for operators and potential environmental risks. Within the CFR, Title 29, Standard 1910.119, Process Safety Management of Highly Hazardous Materials, applies to closed-loop grab sampling systems. This standard covers “preventing or minimizing the consequences of catastrophic releases of toxic, reactive, flammable, or explosive materials” (Process Safety Management of Highly Hazardous Materials, 2019) and requires mechanical integrity checks. Failures to comply can lead to hefty fines, with possible criminal penalties when violations cause fatalities.
Environmental regulations create a complex compliance landscape that maintenance programs must navigate effectively. The EPA’s Equipment Leak Detection and Repair (LDAR) requirements under 40 CFR Part 63 mandate quarterly monitoring using EPA Method 21 procedures (National Emission Standards for Hazardous Air Pollutants for Source Categories, 2017), with maximum allowable leak rates triggering repair timelines. Closed-loop grab sampling systems must demonstrate leak-tight operation to avoid volatile organic compound (VOC) emissions that violate National Emission Standards for Hazardous Air Pollutants (NESHAP).
The regulatory consequences of maintenance failures are severe: violating standards of the Clean Air Act (Criminal Provisions of the Clean Air Act, 2025) can result in jail time or fines pursuant to 18 U.S.C. 3571 (Crimes and Criminal Procedure, 1984). Additional state and local requirements introduce further challenges, creating varying inspection frequencies and compliance obligations that facilities must navigate.
Common Failure Points
Most maintenance failures happen in predictable places if you know where to look. Depending on the application, either a cylinder or a bottle is typically used for sample collection. Because the design of cylinder-type and bottle-type sampling systems are very different, the potential failure points are different as well.
Cylinder-type systems are used for collecting samples of vapor or pressurized liquid process media. As such, sample cylinders should undergo annual inspection and pressure testing to the manufacturer’s specifications. The visual examination should focus on the condition of the cylinder container, valves, and quick-connects – these are components that experience high-frequency use and are transported often and handled by multiple personnel. Quick-connects and valves represent the most failure-prone components, with stem damage and worn seals creating leak paths that can expose operators to hazardous chemicals and release environmental pollutants. Quick-connect fittings, with robust double ended shutoffs (DESO), enable safe cylinder removal under pressure and, thus, are the most common replacement point for cylinder systems due to the frequency of coupling and decoupling.
Example of Poorly Maintained Cylinder-Type System
As seen in the upper-left corner of the panel, a leak developed due to lack of maintenance on the quick-connects. The leak continued to worsen until the quick-connects were no longer functional and the system was completely removed from service.
Bottle-type systems should also undergo an annual inspection, but pressure testing is not required as they do not use a pressure-retaining container. The most common failure points are broken or bent needles, sample valves leaking, and missing components. The point at which the bottle connects to the shroud assembly can become misaligned and damage the needles, which can also occur if the wrong bottle size is used. The needles are one of the most frequently replaced components for these systems. The visual inspection should include an evaluation of conditions of the needles to see if they are bent/broken and are still in place. Additionally, one should check for visible leaks or drips accumulating below the system. Evidence of leaking may also be seen on the shroud assembly as the strap sits directly below the needle, making it a common collection point for leaks. Lastly, the inspection should verify that the appropriate sample bottles properly connect to the system and are sized sufficiently for the shroud.
When maintenance plans properly address these failure points through systematic inspection and component replacement, facilities achieve significant improvements in both safety and sampling system performance.
Example of Poorly Maintained Bottle-Type System
A leak can be seen above the shroud assembly from a lack of maintenance on the sample valve; the leak is also accumulating on the shroud strap. On the left side of the strap, there is a screw missing that secures it to the shroud. This reduced support could cause the bottle to sink during sample collection due to added weight, which could expose the vent and/or sample needles and release process media, in this case being sulfuric acid (H2SO4).
Proper Usage Prevents Damage
Proper handling and storage practices can prevent much of the mechanical damage that leads to safety incidents. Sample cylinders that are stored improperly or transported in truck beds or golf carts can experience damage that compromises structural integrity, creating pressure vessel hazards during use. Similarly, if sample bottles are mishandled, they can experience damage that cracks or shatters the glass container. Although some sampling systems use coated bottles that contain the sample even if they are dropped, the best solution to avoid damage is through training and proper handling practice.
Training programs that emphasize proper connection and disconnection procedures for cylinder-type systems can reduce stem damage in quick-connects and prevent needle damage on bottle-type systems from misalignment or use of an incompatible bottle. A proper understanding and adherence to procedures can also reduce the potential for sample contamination, stemming from dead volume in systems, cross-contamination between samples, or inadequate purging procedures that compromise analytical accuracy.
Example of Poorly Maintained Cylinder-System
The quick-connects on this system have not been maintained well, as seen by the splattered process media leaking around the fitting. The pressure gauge has been replaced with the wrong type, with the orientation not only making it harder to read but also obscuring the face since it is facing upward.
Technical Specifications Influence Maintenance Decisions
Understanding component specifications enables informed maintenance decisions that optimize system performance and reliability. Typically, sample cylinders are constructed from 304 or 316 stainless steel for corrosion resistance and can withstand working pressures of at least 1800 psig, with higher pressure ratings available for certain applications. Nearly all sample cylinders offered today comply with the standards of the U.S. DoT, Transport Canada, and TPED. These standards ensure pressure vessel safety with consistent wall thickness and smooth internal neck transitions, which minimizes dead volume that could affect sample quality. Sample bottles typically lack a pressure rating and are intended to be continuously vented during sample collection, preventing pressure buildup.
Material selection drives maintenance intervals and component compatibility. Sample cylinders made from 316L stainless steel provide adequate corrosion resistance for most applications, while some process medias require specialized nickel alloys. Specialized coatings can also shield against reactive compounds that would otherwise degrade standard materials. Sample bottles are typically constructed from glass or plastic and may also include an external coating, which help keep the sample contained in the event the bottle is damaged or dropped.
The sealing material used in the system is also critical when determining replacement intervals and maintenance procedures. Primary seals using PTFE™ or other elastomeric compounds may also need to be replaced. Some applications that experience extreme temperatures or significant swings in temperature can lead to PTFE™ deformation creating leak paths around the sealing points.
Components that are incompatible with either the sampling system design or the sampled media experience reduced lifespans, which may ultimately determine the frequency of maintenance activities.
Understanding Through Troubleshooting
Reviewing historical troubleshooting can reveal patterns of where and when issues arise. These clues should be taken into consideration to devise a more comprehensive preventative maintenance program.
Systematic troubleshooting strategies can minimize diagnostic time and ensure effective repairs that prevent recurring failures. Problem identification requires a clear symptom definition, operational data gathering, recent maintenance review, and operator input to understand failure conditions. Information gathering should include maintenance history, system specifications, process media details, recent changes, and performance data to estimate failure timelines.
Common failure points follow predictable patterns that enable proactive intervention. Valve leakage can result from seat damage, worn seals, particulate contamination, or improper installation with symptoms including external leaks or dripping, sample pressure loss, and environmental emissions.
Considerations For Preventive Maintenance Programs
Preventive maintenance programs incorporate time, usage, and condition scheduling based on equipment criticality and potential consequences of failure. The resulting maintenance intervals are adjusted for manufacturer recommendations, historical failure data, and actual operating conditions to optimize reliability while minimizing costs.
Routine maintenance checks typically focus on visual leak detection (which may be seen as pooling on the ground underneath the system, weeping from the mating/connection points on the system itself, or drips from the needle accumulating on the shroud assembly below it), pressure gauge operation and sample container connection integrity.
Less frequent tasks include external cleaning, tightening connections, inspection of the sampling valve and needle integrity, and examination of the quick-connects for damage indicators that could predict future failures.
Other requirements may include complete system and/or cylinder inspection and pressure testing (with recertification per local jurisdiction). Depending on one’s familiarity with the system, this could also include returning the entire system to the manufacturer so they can perform the review. The manufacturer’s evaluation typically includes hydrotesting and functional testing, which are accompanied by a new testing report.
Preventive maintenance programs include safety reminders, required tools, step-by-step procedures, and operator training refreshers. Focusing on the critical components/common failure points prioritizes the sampling valve, seals, and connection points prone to leakage and is used to create flexible scheduling that adapts to actual equipment conditions rather than rigid time intervals.
Conclusion: Maintenance Saves Money
Financial analysis highlights compelling reasons for systematic maintenance programs. Poor maintenance strategies reduce production capacity, creating opportunity costs that far exceed proactive maintenance investments.
Cost drivers for closed-loop grab sampling system failures resulting from suboptimal maintenance planning include loss of product quality assurance, inconsistent sampling results, and opportunity costs from delayed operations. Environmental and safety costs encompass fugitive emissions violations, cleanup and remediation expenses, safety incident costs, and regulatory penalties that can exceed operational impact costs. Emergency replacement and repair costs include premium pricing for expedited parts and specialized technician overtime rates which are common with reactive maintenance.
Maintenance program benefits extend beyond cost avoidance to operational excellence improvements. Reduced unplanned downtime improves production reliability by minimizing the potential for defects and validating product quality rather than making performance assumptions.
Strategic maintenance investment considers the total cost of ownership including initial system costs, maintenance labor, spare parts inventory, downtime losses, and end-of-life replacement. Through effective maintenance strategies, end-of-life replacement can be significantly delayed by replacing compromised components rather than the entire system.
The investment in comprehensive proactive maintenance programs consistently demonstrates positive returns through reduced downtime, improved safety, enhanced environmental compliance, and optimized operational efficiency. Organizations that implement calculated maintenance strategies position themselves for sustainable competitive advantage in increasingly demanding operating environments where reliability, safety, and environmental performance determine long-term success.
About SENSOR Sampling Systems
SENSOR Sampling Systems is a premier manufacturer of closed-loop grab sampling systems that enable safe extraction of representative samples while managing quality and yield. With universal compatibility across any manufacturer’s systems, SENSOR Sampling offers complete solutions including accessories, spare parts, and consumables – all with off-the-shelf availability. Our comprehensive inventory and technical expertise eliminate the complexity of managing multiple suppliers while ensuring operator safety, sample integrity, and environmental protection in harsh and hazardous applications.
About the Authors
Billy Terry – Product Manager, SENSOR Sampling Systems
Billy Terry is a Product Manager at SOR Controls Group, responsible for product line management for SENSOR Sampling Systems. With over 30 years of experience in sampling systems, Billy has held diverse roles throughout his career, including Field Service Technician, Shop Supervisor, Head Quality Inspector, ISO9001:2008 Quality Administrator, Application Engineer and Lead Sampling Engineer.
Matthew K. Giunta – Marketing Manager, SOR Measurement and ControlMatthew Giunta is a Marketing Manager at SOR Controls Group, responsible for business reporting, data analysis, and product line support for all SOR Controls Group brands. During his 10 years with SOR he has also served as a Product Manager and an Inside Sales Engineer. Matthew is a graduate of the University of Kansas with a Bachelor of Science in Chemical Engineering.
About SOR Controls Group
SOR Controls Group is a global leader in the design and manufacture of measurement and control devices under the brands of SOR Measurement and Control, SSi Temperature Sensors, and SENSOR Sampling Systems. SOR Controls Group actively serves all sectors of the process industry with strengths in oil & gas, petrochemical, chemical, and power generation. We also maintain an engineering and design team capable of providing Engineered-to-Order systems and products with Off-the-Shelf Speed.
With manufacturing locations in Lenexa, Kansas and Houston, Texas, and regional offices in Beijing, Dubai, and Chennai, SOR Controls Group supports a network of sales and service personnel capable of addressing customer requirements in any geographic market worldwide.
References
Vanson Borne and ServiceMax. (n.d.). After the Fall: The Costs, Causes & Consequences of Unplanned Downtime. Retrieved August 29, 2025 from www.panelbuilderus.com/wp-content/uploads/2020/11/After-The-Fall-whitepaper-updated-global-numbers-FINAL-refresh.pdf(PDF)
Process Safety Management of Highly Hazardous Materials, 29 C.F.R. § 1910.119 (2019). Retrieved August 29, 2025 from https://www.ecfr.gov/current/title-29/section-1910.119
National Emission Standards for Hazardous Air Pollutants for Source Categories, 40 C.F.R. Part 63 Subpart A et seq. (2017). Retrieved August 29, 2025 from https://www.ecfr.gov/current/title-40/part-63/subpart-A
Criminal Provisions of the Clean Air Act (2025). U.S. Environmental Protection Agency. Retrieved August 29, 2025 from https://www.epa.gov/enforcement/criminal-provisions-clean-air-act
Crimes and Criminal Procedure, 18 U.S.C. § 3571-3574 (1984). Retrieved August 29, 2025 from https://uscode.house.gov/view.xhtml?path=/prelim@title18/part2/chapter227/subchapterC&edition=prelim
