The WEAKEST LINK: Why Thief Hatch Management is important to your operations
November 19, 2015

A thief hatch is a closable aperture in a tank or vessel.  In the oilfield thief hatches are normally used on low pressure and atmospheric tanks. Thief hatches are used to take samples of the tanks contents, determining the level of the tank and protect the tank from over pressure and excessive vacuum. They are also one of the reasons for the most common compliance violations and operational problems in the Oil and Gas Industry. Let me expand.

Regulatory compliance inspectors are like everyone else, they like the easy pickings of “Low Hanging Fruit” and thief hatches fit that bill. Inspectors will gravitate toward hatches because leaking and unsealed hatches can be easily found and written up. Often the inspector will check hatches first.


A leaking hatch is a failure to control emissions which is found in all enforcement actions. It can be the first “Gotcha” to get the ball rolling for searching for more site violations. Maintaining your thief hatches gives a first impression to the inspector that this site is run properly; it is a basic good housekeeping standard.

EXTRA: If your facility stores hazardous materials or waste (i.e., RCRA), regulatory inspectors will gravitate towards drums not properly closed/sealed; just like thief hatches. Open drums will be cited by an inspector.

Most would agree with the old adage that a chain is only as strong as its weakest link. The weakest link concept applies to the thief hatch and other Pressure Control devices in relation to production equipment. For example if you have an $100,000 vapor recovery and combustor system in place to capture and control emissions and a $25 thief hatch seal fails to allow the gathering tank to pressurize and activate your control equipment, you have a control problem. Once emission control equipment does not function as it is designed, you can be subject to enforcement actions for violating your operating permit. In an enforcement action, you may be required to explain, in great detail to the regulatory agency, where the gas went when the VRU and the combustor were not operating. This makes this issue of maintaining closed hatches and tight seals important.



The number of regulations is increasing and becoming more stringent nationwide. Colorado has been in the news for having very strict compliance rules. The Colorado Department of Public Health and Environment’s (CDPHE) Regulation 7 requires facilities to controlled venting of natural gas from many oil and gas emission sources. The CDPHE has determined that improperly secured thief hatches, visible emissions from a flare, and audible emissions from a thief hatch or pressure relief device (PRV) are violations of Regulation No. 7. The minimum fine by CDPHE for an open thief hatch, visible emissions from a flare or audible emissions from a thief hatch or PRV is $15,000 per day. The duration of each such violation is assumed to be at least one day, unless evidence gathered by the CDPHE and/or provided by the source proves otherwise. Many of the 23 oil producing states (including Ohio, Utah, Wyoming) are looking at the CDPHE rule book as a possible blueprint for their state rules.

Also, the USEPA’s proposed changes to NSPS OOOO (see HY-BON blog) lists storage tank thief hatches as one of the fugitive emission sources that will be required to be periodically checked for leaks using optical gas imaging (OGI).

HatchSense Solution

What if you could know when you thief hatches were properly closed and sealed?

HY-BON/EDI/UNICO can provide its HatchSense system as an intrinsically safe monitoring device retrofitting existing equipment on oil and gas sites, and a remote interface that reports on the position of dump valves and thief hatches on the site. The data could be sent and recorded to corporate/field offices or onsite notification through Bluetooth Gateway venues or site alarm or both. This system will allow producers to prevent/reduce accidental emissions without changing how they operate the site.

There is no sort of intrusive or destructive placement on existing equipment. The HatchSense is a remote, intrinsically safe (Class I Div 1) telemetry system for reporting/alarming on the positions of thief hatches and critical valves on the oil and gas well site. This can help reduce and eliminate the potential of a monetary penalty ($15,000 dollar a day in Colorado) for leaking thief hatches.

HY-BON is currently looking for pilot test sites to implement the use of HatchSense. If interested please call or email Jeff Voorhis at [email protected]/Pd6ma]#[5LS}/|BXwI}q or SiUsHu?y`{LGv9X|fKB]#[=`Ec7^!mwdFOY&G#J7+


Beefing up the “Weakest Link” thief hatch can prevent future regulatory problems and insure better operations.