Compressed gases can be toxic, flammable, oxidizing, corrosive, inert, or some combination of these hazards. In addition to the chemical hazards, the amount of energy resulting from the compression of the gas makes a compressed gas cylinder a potential rocket. Appropriate care in the handling and storage of compressed gas cylinders is essential. The following are six general recommendations.
The following is an overview of the primary hazards to be avoided when handling and storing compressed gases. (Note: Cryogenic liquids and cylinders are covered under the Cryogenic SOP).
Only persons familiar with the hazards should handle compressed gas cylinders.
All cylinder movement should be done with a compressed gas cylinder cart. Always secure the cylinders when in storage or use.
Cylinders secured with a chain or strap must have the
chain or strap attached 2/3 of the way up on the cylinder.
Compressed gas cylinders should not be subjected to any mechanical shock that could cause damage to their valves or pressure relief devices. Cylinders should not be dropped, dragged, slid, or used as rollers for moving material or other equipment.
Cylinder caps perform two functions. First, they protect the valve on the top of the cylinder from damage if it is knocked over. Second, if gas is accidentally released through the valve, the cap will vent the gas out of both sides, minimizing the likelihood that the cylinder will topple. Cylinder caps should not be removed until the cylinder is secured in place and ready for use.
Check the regulator before attaching it to the cylinder. Be sure you are using the proper regulator for the particular gas that is inside the cylinder. If the regulator connections do not readily fit together, the wrong regulator is being used. Do not force connections to fit, as you may permanently damage the threads. See Regulator Selection, Installation, and Operation
Several precautions should be taken during storage of compressed gas cylinders. Full and empty cylinders should be stored separately. Cylinders should be stored upright and secured at all times.
| Gas Category | Other Gas | Unstable Reactive, Class 2, 3, or 4 | Corrosive | Oxidizing | Flammable | Pyrophoric | Toxic or highly toxic |
|---|---|---|---|---|---|---|---|
| Toxic or Highly Toxic | --- | 6.1 m (20 ft) | 6.1 m (20 ft) | 6.1 m (20 ft) | 6.1 m (20 ft) | 6.1 m (20 ft) | |
| Pyrophoric | --- | 6.1 m (20 ft) | 6.1 m (20 ft) | 6.1 m (20 ft) | 6.1 m (20 ft) | --- | 6.1 m (20 ft) |
| Flammable | --- | 6.1 m (20 ft) | 6.1 m (20 ft) | 6.1 m (20 ft) | --- | 6.1 m (20 ft) | 6.1 m (20 ft) |
| Oxidizing | --- | 6.1 m (20 ft) | 6.1 m (20 ft) | --- | 6.1 m (20 ft) | 6.1 m (20 ft) | 6.1 m (20 ft) |
| Corrosive | --- | 6.1 m (20 ft) | --- | 6.1 m (20 ft) | 6.1 m (20 ft) | 6.1 m (20 ft) | 6.1 m (20 ft) |
| Unstable Reactive, Class 2, 3, or 4 | --- | --- | 6.1 m (20 ft) | 6.1 m (20 ft) | 6.1 m (20 ft) | 6.1 m (20 ft) | 6.1 m (20 ft) |
| Other Gas | --- | 6.1 m (20 ft) | 6.1 m (20 ft) | 6.1 m (20 ft) | 6.1 m (20 ft) | 6.1 m (20 ft) | 6.1 m (20 ft) |
| Materials | No gas cabinet, gas room, or exhausted enclosure (Unsprinkled areas) |
Gas cabinet, gas room, or exhausted enclosure (UnSprinkled areas) |
No gas cabinet, gas room, or exhausted enclosure (Sprinkled areas) |
Gas cabinet, gas room, or exhausted enclosure (Sprinkled Areas) |
|---|---|---|---|---|
| Corrosive Gas Liquefied Nonliquefied |
68 kg (150 lb) 23 m3 (810 ft3) |
136 kg (300 lb) 46 m3 (1620 ft3) |
136 kg (300 lb) 46 m3 (1620 ft3) |
272 kg (600 lb) 92 m3 (3240 ft3) |
| Cryogenic Fluid Liquefied Nonliquefied |
0 L (0 gal) 170 L (45 gal) |
170 L (45 gal) 340 L (90 gal) |
170 L (45 gal) 340 L (90 gal) |
170 L (45 gal)*** 681 L (180 gal) |
| Flammable Gas Liquefied Nonliquefied |
114 L (30 gal) 28 m3 (1000 ft3) |
227 L (150 gal) 28 m3 (2000 ft3) |
227 L (150 gal) 28 m3 (2000 ft3) |
454 L (120 gal) 56 m3 (4000 ft3) |
| Highly Toxic Gas Liquefied Nonliquefied |
0 kg (0 lb) 0 m3 (0 ft3) |
2.3 kg (5 lb) |
0 kg (0 lb) 0 m3 (0 ft3) |
4.5 kg (10 lb) 1.1 m3 (40 ft3) |
| Nonflammable Gas Liquefied Nonliquefied |
No Limit No Limit |
No Limit No Limit |
No Limit No Limit |
No Limit No Limit |
| Oxidizing Gas Liquefied Nonliquefied |
57 kg (15 gal) 43 m3 (1500 ft3) |
114 kg (30 gal) 85 m3 (3000 ft3) |
114 kg (30 gal) 85 m3 (3000 ft3) |
227 L (60 gal) 170 m3 (6000 ft3) |
| Pyrophoric Gas Liquefied Nonliquefied |
0 kg (0 lb) 0 m3 (0 ft3) |
0 kg (0 lb) 0 m3 (0 ft3) |
1.8 kg (4 lb) 1.4 m3 (50 ft3) |
3.6 kg (8 lb) 2.8 m3 (100 ft3) |
| Toxic Gas Liquefied Nonliquefied |
68 kg (150 lb) 23 m3 (810 ft3) |
136 kg (300 lb) 46 m3 (1620 ft3) |
136 kg (300 lb) 46 m3 (1620 ft3) |
272 kg (600 lb) 92 m3 (3240 ft3) |
***Gas cabinet required or exhausted directly outdoors or to exhaust hood.
Oxidizers and flammable gases should be kept at least 20 ft. away from combustible materials and/or incompatible gases or substances. Storage areas that have a non-combustible wall at least 5 ft. in height and with a fire resistance rating of at least 30 minutes may be used to segregate gases of different hazard classes in close proximity to each other.
Personnel may move compressed gas cylinders under the following conditions only:
Large cylinders moved by vehicle should follow the guidelines above as well as the following:
Several precautions should be taken to prevent the release of high-pressure gases, fire, and explosion. Compressed gas cylinders should not be exposed to sparks, flames, or temperatures above 125°F. Cylinders should not be places where they could come into contact with any electrical apparatus or circuits.
Smoking and open flames should not be permitted in areas used for storage of oxygen or flammable gas cylinders. Never permit oil, grease, or other combustible substances to come into contact with oxygen or other oxidizing gas cylinders, valves, and systems.
When returning an empty cylinder, close the valve before shipment, leaving 25 psig of residual pressure in the cylinder. Replace the valve cap and any valve outlet caps or plugs originally shipped with the cylinder. If repair is needed on a cylinder or its valve, be sure to mark it and return it to the supplier.
Lecture bottles should always be returned to the distributor or manufacturer promptly when no longer needed. Contact the Chemical Management Center for help with this.
In both cases contact the supplier for proper shipping. Improper shipping can result in large fines and possible prison time.
Most leaks occur at the valve in the top of the cylinder and may involve the valve threads, valve stem, valve outlet, or pressure relief devices. Personnel should not attempt to repair leaking cylinders.
Where action can be taken, without exposure to workers, (if trained) move the cylinder to an isolated, well-ventilated area and contact EHS at 3700. If the cylinder contains a flammable or oxidizing gas move the cylinder away from combustible materials and contact EHS at 3700.
Whenever a large or uncontrollable leak occurs, evacuate the area/building and immediately call YSU Campus Police at 911 from a campus phone or (330)941-3527 from a mobile phone.
(From Airgas web site; https://www.airgas.com/) The primary function of a regulator is to reduce high-pressure gas in a cylinder or process line to a lower, usable level as it passes from the cylinder to a piece of equipment. A regulator is not a flow control device. It is used to control delivery pressure only.
Since there are numerous hazards and potential for contamination associated with specialty gases—hazards that vary with the gas, the equipment used, and with the particular application—it is necessary to take the proper precautions to assure safety in high-pressure gas control. Contamination can occur during cylinder change out or from an improperly specified regulator or other component in your gas delivery system.
Before performing any operation with which you are not familiar, seek the advice of an experienced individual. In addition to adhering to the safety and operating rules provided here, the user should be aware of the additional safe operating practices peculiar to each piece of equipment and each application.
Note: Never use any regulator for gases other than those for which it is intended.
The following is applicable to pressure regulators used with flammable, oxidant, corrosive, inert, or toxic gases, when it is necessary to reduce cylinder supply pressure to a lower use pressure.
High-pressure media enter the regulator through the inlet into the high-pressure chamber. When the adjusting knob is turned clockwise, it compresses the range spring and exerts a force on the diaphragm, which pushes the valve stem open. This releases gas into the low-pressure chamber, exerting an opposing force on the diaphragm. An equilibrium is reached when the spring force on the diaphragm is equal to the opposing force of the gas in the low-pressure chamber.
In a single-stage regulator, delivery pressure increases as cylinder pressure decays, because there is less gas pressure exerted on the valve stem. Thus, frequent adjustment of the control knob is required to maintain constant delivery pressure. This does not pose a problem, however, with pipelines and liquefied gas products where inlet pressure is maintained relatively constant.
A two-stage regulator functions similarly to two, single-stage regulators in series. The first stage reduces inlet pressure to a preset intermediate pressure, typically 350 to 500 psig. By adjusting the control knob, the second stage reduces the intermediate pressure to the desired delivery pressure.
Like the single-stage regulator, outlet pressure from the first stage of the two-stage regulator rises as cylinder pressure decreases. However, instead of passing out of the regulator, the gas flows into the second stage where the pressure is moderated. Thus, delivery pressure remains constant even as cylinder pressure decays, eliminating the need for frequent control knob adjustment.
Line regulators are typically point-of-use regulators serving low-pressure pipelines. They are also used in conjunction with high-pressure cylinder regulators that limit the inlet pressure to 250 to 400 psig. Cylinder regulators are available in either single-stage or two-stage models for high-purity, general purpose, or special service applications.
High-purity regulators are designed and constructed to provide diffusion resistance and easy cleanup. Metal diaphragms and high-purity seats and seals minimize or eliminate outgassing and inboard diffusion. These regulators should be capable of containing and removing contaminants during cylinder change out. Only bar stock body regulators should be used for these gases.
General purpose regulators are designed for economy and longevity. They are recommended for noncorrosive general plant, pilot plant, and maintenance shop applications where diffusion resistance is not required. These types of regulators are not for analytical or high purity applications.
Special service regulators are specifically constructed for special applications including oxygen, acetylene, and fluorine service and high-pressure, ultra-high-pressure, and corrosion service. To make your selection easier, this catalog lists the proper regulator for almost every gas, pressure, and situation. Simply look up the gas or mixture for your application and you will find the appropriate regulator listed under “Recommended Equipment.” CGA valve outlets are also noted for each gas and gas mixture. The regulator must be equipped with the appropriate CGA connection for the cylinder valve outlet.
With the regulator adjusting knob turned fully counterclockwise, place both hands on the cylinder valve and open it slowly, allowing the pressure to rise gradually in the regulator. Stand as shown with the cylinder valve between you and the regulator. When the high-pressure gauge indicates maximum pressure, open the cylinder valve fully.
Always close the cylinder valve when product delivery is not needed. Do not leave it open when the equipment is unattended or not operating.
Turn the adjusting knob clockwise and establish the required use pressure by referring to the low-pressure gauge. Make sure that the cylinder valve is easily accessible.
REMOVING THE REGULATOR FROM SERVICE
Small propane cylinders and calibration gas cylinders must be given to EHS for proper disposal.
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