P&IDs Review by Piping Engineers in an EPC project

What does API 682 mean to a pump and to your process piping?

My answer:
Please check these links:
1.
www.amarinth.com/public_library/ ... system.jpg
This photo is of a standard end suction top discharge pump with API 682 Plan 53A accessories. See that vertical support with the small bottle and small piping. Your piping is in addition to the extra equipment. If your pump engineer requires API 682 accessories for a pump then you have extra piping and must route the discharge piping to clear these items.


2.
www.sundyne.com/cda/ind/pr/0,105 ... 89,00.html
This photo is of a high pressure side suction, side discharge horizontal split case pump with API 682 Pump accessories. Again, see those vertical supports with small bottles and small piping. That is furnished by the pump vendor. You still need to supply cooling water supply and return plus a closed vent to flare and nitrogen purge. In addition the main product suction and discharge cannot interfere with the API 682 items or the access to them.

1) Which side of a valve should a pipe spec breaks be shown and why?
The "Spec Break" (or Line Class change) should be on the down stream side of a higher rated valve or group of valves.
- If you are talking about just a single valve installation and the rest of the continuing line has no other valves, then the "Break" shall be on the down stream side of that valve.
- If you are talking about a control valve manifold where the upstream pressure is very high and the line class is higher than the ongoing downstream piping then: The control Valve must be rated for the higher line class, all other valves in the manifold must be rated for the higher line class, the "Spec Break" shall be on the downstream side of the Bypass valve (if more than one valve in the bypass, then on the down stream side of the last valve) and on the downstream side of the block valve on the downstream side of the control valve.

2) The control valve to control the flow is normally incorporated in a fallowing way (Flow direction is from 1 --> 6):
1) Normal pipe ----2)reducer----3)drain connection

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4) flow control valve

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5) reducer again---6) normal pipe, Why is the drain connection located upstream of CV?
In general the popular thinking is that if the control valve "Fails" in the closed position then the high pressure commodity (gas or liquid) will be trapped on the upstream side of the control valve. Thus with the bleed on the "high pressure" side you will bleed it off before undoing the flanges. Safety!

Why not downstream?
Good question! In my opinion I think there should be a drain on both sides of any control valve.

3) Why should the temperature instrument be '10 pipe diameters downstream of pressure instrument.
Any temperature instrument is a probe that protrudes into or near the center of the line. This probe creates a disruption of the flow and causes a back pressure on the upstream side of the probe and a reduction of pressure on the downstream side of the probe.
The back pressure on the upstream side will distort the pressure gage reading just as the turbulence will on the downstream side.
Does this help?

Why we are bringing valve at higher rated side?
The valve must be the higher rated line class because when it is closed it must "Hold" the higher pressure of the higher line class.

And suppose if we have spec breaks that are of same rating each side, Why yet we indicate it downstream of valve?
If the piping is the same rating on both sides of the valve then you should have the same line class on both sides of the valve and you don't need a "Spec Break".