Pressure switch - time lags.

[RichCor]

2 hours ago, superal said:

     I read that many pumps use compressed air held by a bladder , so why would a nitrogen tank be used as in our case . 

 

According to the "Internet", the Accumulator/Expansion/Pressure Tank is supplied charged with inert nitrogen gas to prevent internal corrosion. 

 

Normal 'air' contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide and between .4 - 1% water vapor; the presence of oxygen is more likely react over time with the steel enclosure. "If you charge it with air it's going to end up as all nitrogen after the oxygen is converted to iron oxides, so why not start with nitrogen and skip the rusting step."

 

Also note that bladder diaphragm membranes are 'permeable' and gas can leak through them over time, requiring the 'tank blanketing gas' be replaced periodically.

[VocalNeal]

12 minutes ago, RichCor said:

According to the "Internet", the Accumulator/Expansion/Pressure Tank is supplied charged with inert nitrogen gas to prevent internal corrosion. 

 

Possibly, but the Nitrogen would only be at the top. The oxygen in the water in the bulk of the tank would be a larger concern if one was worried about corrosion. 

 

If the tank has a valve you add air to 2psi below the pump turn on pressure. From your picture. In this case 29 psi or 2kg/cm. Given the vagaries of pressure gauges, I would say 25-ish psi would be OK. 

[RichCor]

3 hours ago, superal said:

 I read that many pumps use compressed air held by a bladder , so why would a nitrogen tank be used as in our case . 

Let me add: 

In a bladder-type tank, depending on the design, the 'bladder' can be a balloon that entirely contains either the gas or the water charge (isolating it from the bare metal of the containment vessel) -- contrasted by diaphragm-type tank where both the gas and water will come into direct contact with the vessel shell. So, depending on the design, nitrogen may not be of benefit.

 

     

 

                

 

As always, consult the unit manual so see what's recommended by the manufacturer.

[wayned]

I can see no reason  why you would use nitrogen in an accumulator tank for a water pump, however, if you are pumping hydraulic fluid, it is essential that an inert gas such nitrogen be used.  If normal compressed air is used, in certain conditions the hydraulic fluid can react with the oxygen in the compressed air and cause an explosion.  I have three corn combines that have accumulator tanks in the hydraulic system and they must be filled with nitrogen.  The tanks are about the size of the small ones on the water pumps and might even be interchangeable. If they are interchangeable it would be prudent for the manufacturer to fill all of their tanks with nitrogen to avoid possible accidents.

[superal]

4 minutes ago, wayned said:

I can see no reason  why you would use nitrogen in an accumulator tank for a water pump, however, if you are pumping hydraulic fluid, it is essential that an inert gas such nitrogen be used.  If normal compressed air is used, in certain conditions the hydraulic fluid can react with the oxygen in the compressed air and cause an explosion.  I have three corn combines that have accumulator tanks in the hydraulic system and they must be filled with nitrogen.  The tanks are about the size of the small ones on the water pumps and might even be interchangeable. If they are interchangeable it would be prudent for the manufacturer to fill all of their tanks with nitrogen to avoid possible accidents.

What you call an accumulator tank says on my tank        Nitrogen Tank              Water Hammer Eliminator  , sounds more like an air pressure relief valve or air bleeder to me . Does that make sense ?

[superal]

1 hour ago, RichCor said:

Let me add: 

In a bladder-type tank, depending on the design, the 'bladder' can be a balloon that entirely contains either the gas or the water charge (isolating it from the bare metal of the containment vessel) -- contrasted by diaphragm-type tank where both the gas and water will come into direct contact with the vessel shell. So, depending on the design, nitrogen may not be of benefit.

 

     

 

                

 

As always, consult the unit manual so see what's recommended by the manufacturer.

Wish I had been given a manual , have to rely on the appointed local installation tech who does not seem to have your knowledge or that of other replies . Now 24 hours since the pipe mod and all ok .

[RichCor]

8 minutes ago, superal said:

What you call an accumulator tank says on my tank   Nitrogen Tank    Water Hammer Eliminator  , sounds more like an air pressure relief valve or air bleeder to me . Does that make sense ?

Accumulator/Expansion/Pressure tanks have a different role from that of a pressure relief or bleeder valves.

 

The 'accumulator tank' on a water pump is a smaller tank containing a gas blanket allowing it to take on or release water at pressure as the water line pressure changes. Fitted close to the pump discharge, it acts as a pressure buffer, absorbing sharp changed in water line pressure while the pump is running, smoothing the outlet pressure. It also extends the pump life by lengthening the on/off cycle timing of the pump by reserving and releasing water at pressure, preventing premature wear on pump parts.    

 

A 'pressure tank' is a small to larger tank and its general purpose is to hold large quantities of water in reserve at pressure. When a tap is opened water first flows from this reserve tank until it no longer provides water at the line pressure set at the pump. The pump then starts flowing water to the open tap and simultaneously 'recharging' the pressure tank with water. The pump continues to run until the upper pressure level is reached (usually when the tap is turned off and the pressure tank is refilled to pressure).

 

An 'Expansion Tank' or expansion vessel is a small tank used to protect closed (not open to atmospheric pressure) water heating systems and domestic hot water systems from excessive pressure. The tank is partially filled with air, whose compressibility cushions shock caused by water hammer and absorbs excess water pressure caused by thermal expansion.

 

In these instances, you want to MAINTAIN the pressure volume creating the cushion in the containers. 

 

 

A 'bleeder valve' or 'pressure relief' valve are generally only required on hot water systems, to reduce or eliminate the pressure condition.

[superal]

43 minutes ago, RichCor said:

Accumulator/Expansion/Pressure tanks have a different role from that of a pressure relief or bleeder valves.

 

The 'accumulator tank' on a water pump is a smaller tank containing a gas blanket allowing it to take on or release water at pressure as the water line pressure changes. Fitted close to the pump discharge, it acts as a pressure buffer, absorbing sharp changed in water line pressure while the pump is running, smoothing the outlet pressure. It also extends the pump life by lengthening the on/off cycle timing of the pump by reserving and releasing water at pressure, preventing premature wear on pump parts.    

 

A 'pressure tank' is a small to larger tank and its general purpose is to hold large quantities of water in reserve at pressure. When a tap is opened water first flows from this reserve tank until it no longer provides water at the line pressure set at the pump. The pump then starts flowing water to the open tap and simultaneously 'recharging' the pressure tank with water. The pump continues to run until the upper pressure level is reached (usually when the tap is turned off and the pressure tank is refilled to pressure).

 

An 'Expansion Tank' or expansion vessel is a small tank used to protect closed (not open to atmospheric pressure) water heating systems and domestic hot water systems from excessive pressure. The tank is partially filled with air, whose compressibility cushions shock caused by water hammer and absorbs excess water pressure caused by thermal expansion.

 

In these instances, you want to MAINTAIN the pressure volume creating the cushion in the containers. 

 

 

A 'bleeder valve' or 'pressure relief' valve are generally only required on hot water systems, to reduce or eliminate the pressure condition.

So am I correct in assuming that my nitrogen tank is an accumulator type ? and if so what would you have done to cure the rapid on off action of the pressure switch / pump other than the large bore pipe insert ? 

[VocalNeal]

Is the large bore pipe vertical or horizontal?

[Crossy]

1 hour ago, superal said:

So am I correct in assuming that my nitrogen tank is an accumulator type ? and if so what would you have done to cure the rapid on off action of the pressure switch / pump other than the large bore pipe insert ? 

 

Check if the tank has an air valve, if it has, take it off and top it up to the recommended pressure (air would be fine).

 

If not, time to replace the tank.

[RichCor]

As @Crossy initially wrote quite a long bit ago, 

On 6/23/2017 at 3:20 PM, Crossy said:

OK, it's possible that the nitrogen tank has lost its charge,

 

but I would be looking initially at a faulty pressure switch (the thing with the contacts). They are cheap, take it off and get a replacement. Do NOT try to adjust the switch without using a pressure gauge, they are set correctly when new.

 

Given the water pump was surging in 2 second cycles I would have immediately suspected the accumulator tank. But also as @Crossy wrote, it could have also been the pressure switch. Both give similar failure symptoms.

 

So, probably I would have drained the system and checked the pressure at the Schrader "tire valve" with a tire pressure gage to see how the nitrogen pressure is doing.

 

 

@VocalNeal keeps asking if your new 100mm (4") section is place vertical or horizontal ...and as @Crossy already commented, "Sounds like he has created a DIY pressure tank."    Any 'trapped' air in the larger pipe will act as a defacto pressure spring ...well, until it gets absorbed into the water and needs to be drained and refreshed. 

 

[superal]

2 hours ago, VocalNeal said:

Is the large bore pipe vertical or horizontal?

Horizontal