Excessive gas pressure?

Bob Harper

Each valve has a rating stated on it--usually 1/2 psi or 14 wci. If you have overpressured the valve, it along with the manifold pressure regulator must be replaced The diaphragm can rupture leaking gas. Test for steady gas leaking at the regulator vent. Still, if you know it got the whammy, it must be replaced whether you detect leakage or not. I would go so far as to Tag Out/ Lock Out until the repair could be made. Then send the bill to whomever did it. I would also followup with a Cer. Letter Ret.Recpt. stating the problem, the hazard, what kind of injuries can result from this hazard, and it's their responsibility to make sure it doesn't happen again. If someone put a 2 psi system onto a low pressure system, that's negligence. BTW, they are required to label high pressure gas systems at the meter, regulators, and entering appliances.
We see this when they add on to a house or esp. adding a 450K pool heater. Instead of replacing existing gas lines with pipes twice the diameter or more, they can use high pressure but you must knock it down with a psi to wci reg. before the appliance unlist that appliance is listed for that pressure and application. Also, check the rules on venting the regulator to the outside away from openings.
ANSI currently allows 235 cc/hr leakage through a valve's operator and 200cc/hr through the seals at 3/4 psi. I heard they just increased the allowable leakage through a vent limiter from 1 cubic foot per hr. to 3.5. Anyone else heard this? Timmie?

Joe_5

Excessive gas pressure?

What happens when residential natural gas fired equipment is exposed to too much supply pressure? Is there a standard that the valves must hold to? After the max what happens? Hugh burner flames or none? Does it differ what occurs after a max pressure event by what type gas control is used? Any stories? Thanks in advance, Joe M

jeff_51

thats what the regulator is supposed tp prevent

excess pressure is supposed to be vented by the regulator if it exceeds what the reg can handle. Any specifics or just wondering?

jeff_51

alot of regs and gas valves are adjustable

an have changebel springs to give you a wide range of options while carrying less product, so a "high" gas pressure incedent may not necessarily do much to anything. We run 2psi gas here into the mechanical room and then pressure down at a manifold. Every once in awhaile you get an illegal hook up, no reg so you have 2psi running directly to the appliance. Not that big a diff in apperance. I'm sure they are putting out scads of monoxide, but when we put in the reducing reg, we have never had to change out any of the controls yet. A big spike should be handled at the gas meter and main reg which around here reduces from around 50-60psi down to 2psi. so they can handle a big spike. in some areas they reduce down from much higher pressures at the meter. Re: valves. we have to run high pressure gas valves before the reg, usually wog rated to at least 400psi, just as an additional precaution incase the meter reg totaly blows out and you have high pressure coming into the house

Joe_5

more on pressure regulators and over pressure events

I'm looking for actual stories of when the utility's regulator failed and overpressured the house piping. I've been on jobs where the equipment shuts down, including standing pilots and non-pilot equipped units. I haven't seen what everyone expects to see on an overpressurization, big flames that shoot out of a furnace and blown out regulators on gas valves.

Dale

Low Pressure

In the old low pressure main cities there is no utility regulator, about 10 years ago in Chicago Peoples Gas sent high pressure into a low pressure system and had fires and explosions in I think about 10 houses. The other time this happens is when an outside utility regulator gets wet internally and freezes, forcing it open. Usually this isn't a real serious problem unless there are devices/appliances that don't have their own regulators and are designed to work at the std. 1/4 pound pressure.

Unknown

Joe I know you work for a utility

so I wonder why you are asking this question???

Different systems require different pressures. Today we have systems that are set up to work on 1/2 lb pressure or less ( most residences). We also have CSST systems in some states that allow 2lbs and 5lbs with reduction at the manifold regulator (usually a Maxitrol) to inches water column for use at the equipment.

We have always had commercial and industrial systems with 2LB and 5LB systems with special metering and regulation. The burners used also had to regulated in accordance with ANSI Z83.3 there is alos special valve trains for these burners with many safeties in place.

Depending on whose gas valve you talk about the ones that have a diaphragm are designed to only have a 1/2 pound or less. Some White Rodgers valves (solenoids) claim to be able to withstand 100 PSI, although I would not suggest trying it. On some redundant valves I have found that when some propane companies in an attempt to not have to run large piping they boost the second stage regulator to 14" W.C. or even 15" W.C. that the gas valve will not open when powered. The pressure on the first valve in the redundant valve series which typically opens upward will just not open.

To answer Joe M's question, I recall a Thanksgiving Day incident in a small town in Pennsylvania the name slips me right now which had both a district regulator and an a backup regulator fail at the same time. With all the ovens going for cooking turkey they had over 100 fires. Flames on top burners were very high. The pressures caused many valve diaphragms to rupture (single seated gas valves). If my memory serves me this was back in the 1970's.

I feel with many of the backups in place today and also the design of controls it would be very hard to duplicate those conditions. However you just never know.

Joe M. if you want to discuss this further give me a call at 401-437-0557 on Friday. I will be tied up in class on Thursday.

Robert O'Connor_7

Joe.

Improper gas pressure can and will lead to lots of, not so nice things if left that way. Most equipment we encounter (with improper gas pressure) soot up. Sooting could clog your flue ways quite rapidly and lead to serious problems such as high CO, blocked chimney and or flue ways preventing the products of combustion from getting through. Don't rely on TFE's to keep you safe. Test the pressure before you continue.


Robert O'Connor/NJ