There are not many workplaces in the USA that do not have an “air receiver”; in fact most have multiple receivers of all different types and sizes. But for the most part, these vessels operate in the dark corners of the facility – out of sight and out of mind. Do these vessels pose a hazard to personnel when they are not “managed” properly? A stark reminder of how dangerous they can be occurred in 2012 at a paper mill when a receiver catastrophically failed killing one worker and injured four others. (See end of this article for more accidents) Most air receivers in industrial service are large pressure vessels with a capacity from several hundred gallons to several thousand gallons and operate at around 125-150 psi. OSHA’s 1910.169 is in place to set the baseline for operating these vessels safely; however, we find very few facilities that even know this standard exist, much less that their facility has receivers that fall within this standard. For those who have a receiver(s) at their facility, here are the requirements:
The standard applies to compressed air receivers, and other equipment used in providing and utilizing compressed air for performing operations such as cleaning, drilling, hoisting, and chipping.
New and existing equipment
OSHA requires the receivers to be ASME Stamped pressure vessels. For those of you already doing PSM/RMP, these terms are nothing new; however, for those who do not work in process facilities that utilize pressure vessels this can be a bit much to swallow at first. Basically OSHA requires all new air receivers installed after the effective date of these regulations (August 27, 1971) shall be constructed in accordance with the 1968 edition of the A.S.M.E. Boiler and Pressure Vessel Code Section VIII, which has been incorporated by reference as specified in Sec. 1910.6. As you can see, the standard is a tad bit dated, as most pressure vessels built before 1968 may not even be in service any longer and I know of not one shop that will build a new pressure vessel to a 1968 edition of the PV Code. But there are a lot of old receivers for sale in the “used market” and they get moved around from facility to facility… so buyer beware!
The standard also requires ALL safety valves be constructed, installed, and maintained in accordance with the A.S.M.E. Boiler and Pressure Vessel Code, Section VIII Edition 1968. Again, we should be using a newer version of ASME Section VIII, 1968 to manage our RVs on these vessels.
Installation
Air receivers shall be so installed that ALL drains, handholes, and manholes are easily accessible. Under NO circumstances shall an air receiver be buried underground or located in an inaccessible place. OSHA does not define or quantify the phrase “inaccessible place”, but I have seen OSHA, as well as other inspection agencies, take issue with a receiver installed in a corner of a facility with the manway facing the wall and the receiver within a couple of feet from the wall. The AI required the facility to rotate the receiver so that the manway was facing outward from the wall so that it was “accessible”. FYI… This was done even though the manway is so small that no one would be able to enter the vessel!
A drain pipe and valve MUST be installed at the lowest point of every air receiver to provide for the removal of accumulated oil and water. It should be noted that the #1 cause of failure for these vessels is corrosion from within due to the accumulation of water inside the vessel. We do NOT get a “pass” on this requirement even when we have “air dryers” installed to maintain a low dew point for our compressed air. I have tried this argument on several occasions and lost each time with different AI’s in different states and territories. The employer has two (2) options to PREVENT the accumulation of water within the vessel:
- adequate automatic traps may be installed in addition to drain valves.
- the drain valve on the air receiver shall be opened and the receiver completely drained frequently and at such intervals as to prevent the accumulation of excessive amounts of liquid in the receiver.
Most of the compressed air systems installed in the past 10 years have automatic drains on them; but this is not 100%! We have to ensure we manage this vessel safely and draining the water from within on a REGULAR basis is a HUGE part of this effort. As I said, the leading cause of failure of these vessels is corrosion from within caused by the accumulation of water.
Gages and Valves
There are two physical items that I look for when I walk by an air receiver:
- pressure gauge that I can read from ground level and
- a relief valve that is either directly on the vessel (near the top if not on the head) and if not directly on the vessel then near the vessel with NO other valves (or restrictions) between the RV and the vessel.
I can assure you that a well trained CSHO can walk by and look for these two basic items. If either one is missing, that is a sure sign of a problem!
Safety Appliances
Safety appliances, such as safety valves, indicating devices and controlling devices, shall be constructed, located, and installed so that they cannot be readily rendered inoperative by any means, including the elements (i.e. weather conditions). This is another easy item to find during audits, especially this time of year (e.g. winter). Although the vessel may be indoors, a lot of facilities will drain their vessel through a wall to the outside. We have come across several set ups where the drain line was frozen solid. Now this is typically not a significant risk since the freezing is caused by environmental conditions and is temporary at best; however, we have come across freeze scenarios that were caused by the area the vessel drains to passing through a freezer space and this is a concern as the freeze condition was long-term.
NOTE: after thawing the line and draining the receiver, approximately 20 gallons of rusty water was drained!! The vessel was removed from service and underwent a rigorous inspection and it failed with only 20 years of service. Seems that in 20 years the vessel was never drained, nor the RV replaced or tested.
ALL safety valves shall be tested frequently and at regular intervals to determine whether they are in good operating condition. You will notice that in this 1971 standard, OSHA uses the term “frequently” and at “regular intervals” and unfortunately they have not quantified these terms. At best, I recommend facilities follow the same RV Safety Program as we do in PSM… change them every five years and tests them to ensure the five years is satisfactory. Those receivers that operate INDOORS in a climate controlled environment should rarely see issues; however, those receivers operating in non-climate controlled environments have been found to have RVs with some form of deficiency. We also need to inspect these safety valves to ensure they are not being abused! For facilities that are not familiar with these safety devices we see some really scary arrangements and situations. Everything from birds and hornet nests inside the discharge port to caps welded onto the end of the vent pipe on the roof, to an I-beam run over the top of the vent line within 1” of the discharge! When the facility does not understand the hazards associated with these vessels, their use and care often go un-noticed until something fails.
And as an FYI, 1910.169 applies to PORTABLE air receivers as well. So all these units on wheels or have carrying handles fall under the requirements above! Air receivers on “service vehicles” will fall under these requirements, which if you think managing a fixed vessel against these requirements, try managing multiple vessels that are never in the same location! But don’t let someone tell you they are exempt because of their “use”, “size”, or one of my favorites… “if you buy the air compressor and receiver in a package from XXXXX Hardware store, OSHA does not enforce them”. If it is an “air receiver” it falls under 1910.169!
Here are a few accidents involving air receivers:
https://www.osha.gov/pls/imis/accidentsearch.accident_detail?id=202362570
Employee #1 was injured when the 300-gallon air receiver of an air compressor unit ruptured resulting in severe injuries to both his legs The accident was caused by rust inside the receiver that weakened the steel due to the receiver not been drained. The safety valve was inoperative due to corrosion from not being tested. The pressure gauge was stuck on 90 psi. Employee #1 was transported to the hospital where his left leg had to be amputated below the knee and the right leg required several pins. Employee #1 was hospitalized.
https://www.osha.gov/pls/imis/accidentsearch.accident_detail?id=200072809
Employee #1 responded to an air receiver tank explosion that caused a fire in and around the debarker area outside the building.
https://www.osha.gov/pls/imis/accidentsearch.accident_detail?id=674853
A shop-made pressure vessel (air receiver) was overpressurized and exploded. Due to the explosion, two pieces of metal were sent flying. Employee #1 was struck by a piece of metal on the forehead and sustained lacerations. Employee #2 was struck on the hand by another piece and sustained lacerations and broken fingers. The air receiver was being used in conjunction with a glue gun and had no pop-off valve or air gauge.
https://www.osha.gov/pls/imis/accidentsearch.accident_detail?id=772491
Plant employees had just completed bagging compost products and the bagging line was shut down to refill material dispensing bins. Employee #1, the office manager, came into the plant to collect time cards. While he and a coworker were standing inside a doorway conversing, a non-ASME code air receiver ruptured; its south end plate flew off in an upward trajectory. The plate struck Employee #1’s head, nearly severing the skull and removing part of the brain. The plate continued on, striking and breaking a roof joist. The coworker was impacted by Employee #1’s propelled body and knocked into the building wall; he was apparently uninjured although he later complained of a sore back and psychological problems.
https://www.osha.gov/pls/imis/accidentsearch.accident_detail?id=14400600
Employee #1 was assigned the task of repairing a 16 horsepower gasoline engine, powering a worthington air compressor, at a gas well site. The engine was backfiring excessively and blowing apart an injector gas coupling. The engine and compressor were mounted on top of a roy e. Hanson jr. Air receiver, ser. #186730. Although there were no witnesses to the accident, it appears that the ends (welds) of the receiver blew out. The force of the explosion drove employee #1 into a gas compressor, then up and behind the compressor. Employee #1 was probably killed instantly.
https://www.osha.gov/pls/imis/accidentsearch.accident_detail?id=14550008
A curtis, 20 horse power air compressor had just been shut off by employee #3 because he said it was making a “squeeking noise”. About 30 seconds later, without warning, the tank exploded. No cause of the explosion could be determined.
https://www.osha.gov/pls/imis/accidentsearch.accident_detail?id=200515641
At approximately 11:20 a.m. on May 28, 2012 Employee #1, a 50-year-old male with Verso Paper Corporation was working in the vicinity of the mill air receiver tank when it exploded. Earlier in the day, a leaking water valve was discovered under the Number three Paper Machine and employees were instructed to shut down that machine and supporting equipment so the valve could be repaired. Specific lockout/tagout procedures were not utilized. One of the pieces of equipment that was shut down was the drill well pump, which caused a decreased flow of water to the air compressors. When an employee was told to turn the drill well pump back on, he discovered that someone else had already done it. There are five Gardner-Denver air compressors, with two air receiver tanks (one for Mill Air and one for Instrument Air) and two chiller/dryer units located on the floor above the air compressors. Two coworkers heard a loud air release while they were in the break room adjacent to the Air Compressor Room. The surviving coworker in the tank area, said he saw some smoke or light haze and saw fire shoot up and out of AC Number three approximately three-to-six feet in the air. He turned to run out of the area and had taken three-or-four steps before there was a loud explosion and he went flying. He did not see what happened to Employee #1. The Mill Air receiver tank exploded, causing damage to the building and contents of the building. In 2010, the system for cooling the oil for the air compressors was changed from air cooled to water cooled. Shutting the well water off decreased the water flow to the air compressors, which resulted in AC number-four and number-five shutting down due to high temperatures of 200 and 205 degrees Fahrenheit range. AC number three continued to run and overheated. Company records show that the cooling water flow had decreased (200 gpm to 59 gpm) during the hours prior to the explosion and the oil temperature in AC number three had increased to over 308 degrees prior to the explosion. The MSDS indicates the AEON 4000 Compressor Oil used in the five air compressors had a flash point of 210 degrees F. The explosion resulted in killing Employee #1 and four coworkers being sent to a local hospital where they were treated and released.
MN-OSHA Alert
https://www.dli.mn.gov/ccld/BoilerIncidentsAir2.asp
The tank was not built to ASME code and not registered with the National Board. The drain valve on the tank was removed, probably because it was leaking, and replaced with a plug. The accumulation of water in the vessel caused severe corrosion and thinning of the metal on the bottom of the tank. Ultrasonic thickness testing revealed a thickness of .070 inches. At this thickness the tank should never have been allowed to be pressurized. The safety valve was set at 140 psi and the pressure controls were assumed to be working properly. The purchaser brought home his new treasure, put it in his garage and plugged it in. When the pressure in the tank reached about 100 psi, the tank ruptured and flew across the garage. Luckily, nobody was injured. Make sure you drain your air tanks on a regular basis!