2011年1月25日星期二

Check valve flow?

which way does the air flow in the vacuum line (under the intake
manifold) that goes from the throttle body to the solenoid valve (over
the air box)?When I replaced the PCV system (Thanks to the information found in this
site) I noticed that the check valve under the intake manifold was
pointing from the EVAP canister to the throttle body (that’s the way VW
built the engine because the line still had those one-time use hose
clamps); though the vacuum line diagram printed on the car says that the
air (vacuum, I don’t know) flow is supposed to go from the throttle
body to the EVAP canister (solenoid valve).



I had a CEL (P0171) that fixed a few days ago; it was a “vacuum line
leak” (in the line before mentioned). I followed the directions on the
vacuum line diagram on the car and put the check valve in the way it’s
supposed to be. Now, I have another CEL (P0441) which is a faulty
solenoid valve (part of the same vacuum line) and I’m wondering if I’m
getting the CEL due to the switch in the flow in this particular check
valve…!

From the originalcheckvalve
.

How to Check Valve Stem Caps

A valve stem cap keeps debris out of the valve stem which could cause
the valve stem core to fail. The cap is removed to check air pressure
and to inflate or deflate the tire. Some caps come with a pin on the top
of the cap that can untwist or At Provoscooter you will find a growing selection of performance and
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From the originalcheckvalve
.

China Crane Wafer Check Valve

The ISA bus was developed by a team lead by Mark Dean at IBM as part of
the IBM PC project in 1981. It originated as an 8-bit system and was
extended in 1983 for the XT system architecture. The newer 16-bit
standard, the IBM AT bus, was introduced in 1984. In 1988, the Gang of
Nine IBM PC compatible manufacturers put forth the 32-bit EISA standard
and in the process retroactively renamed the AT bus to "ISA" to avoid
infringing IBM's trademark on its PC/AT computer. IBM designed the 8-bit
version as a check valve buffered interface to the external bus of the Intel 8088
(16/8 bit) CPU used in the original IBM PC and PC/XT, and the 16-bit
version as an upgrade for the external bus of the Intel 80286 CPU used
in the IBM AT. Therefore, the ISA bus was synchronous with the CPU
clock, until sophisticated buffering methods were developed and
implemented by chipsets to interface ISA to much faster CPUs.
Designed
to connect peripheral cards to the motherboard, ISA allows for bus
mastering although only the first 16 MB of main memory are available for
direct access. The 8-bit bus ran at 4.77 MHz (the clock speed of the
IBM PC and IBM PC/XT's 8088 CPU), while the 16-bit bus operated at 6 or 8
MHz (because the 80286 CPUs in IBM PC/AT computers ran at 6 MHz in
early models and 8 MHz in later models.) IBM RT/PC also used the 16-bit
bus. It was also available on some non-IBM compatible machines such as
the short-lived AT&T Hobbit and later PowerPC based BeBox.
Madge 4/16Mbps TokenRing ISA NIC.
Ethernet 10Base-5/2 ISA NIC.
In
1987, IBM moved to replace the AT bus with their proprietary Micro
Channel Architecture (MCA) in an effort to regain control of the PC
architecture and the PC market. (Note the relationship between the IBM
term "I/O Channel" for the AT-bus and the name "Micro Channel" for IBM's
intended replacement.) MCA had many features that would later appear in
PCI, the successor of ISA, but MCA was a closed standard, unlike ISA
(PC-bus and AT-bus) for which IBM had released full specifications and
even circuit schematics. The system was far more advanced than the AT
bus, and computer manufacturers responded with the Extended Industry
Standard Architecture (EISA) and later, the VESA Local Bus (VLB). In
fact, VLB used some electronic parts originally intended for MCA because
component manufacturers already were equipped to manufacture them. Both
EISA and VLB were backwards-compatible expansions of the AT (ISA) bus.

From the originalcheckvalve
.

On-Off Valve or Control Valve ?

I'm currently working in a Gas Processing design and I'm a little bit confused in one subject.

So here is the case

I
have two Feed Gas Scrubbers (upstream and downstream of Compressor).
The Feed Gas is normally in 100% vapor form (no liquid flashing
expected).

Bottom of these scrubbers will be discharged to close
drain vessel. Each of them have a control valve installed to control
the liquid level in the vessel.

As I mentioned before that the
Feed Gas stream normally contain no liquids, what will be the best
design for the control valve, an on-off valve OR a controlling one ?

The on-off valve will be opened if the liquid level reach HLL, then emptying the liquid until it reaches LLL in 3-5 minutes.

OR

Control Valve that will maintain the level of liquid in the vessel ?
It really depends on your level controller.  If you are trying to maintain the fluid level in a narrow range and have a throttling level controller (like a CEMCO), then you want a valve that reacts to a variable signal (i.e., a control valve).  If you have a snap-acting controller then it is going to send a signal on an event (i.e., the float reaches the end of travel) and you want an on/off valve.

Many applications that would have been throttling in the past are going to on/off because of fugitive emissions concerns.  A common way to do throttling is to have a continuous bleed that is throttled as the float moves up and down, sending a lower pressure signal to the control valve.  This bleed is not a small amount of gas, so if you are using process gas for your control stream then you are putting that gas into the atmosphere.  On the other hand if you are using control air there is an energy cost to the bleed stream.
Some control valves, often called dump valves are designed for nearly
dry vessels.  Any control valve would require tight shutoff.  Also you
don't want a throttling valve to operate much really near the
seat.  Thus the controller could include gap action that does nothing
until some percentage then opens and throttles until near the seat then
closes.  Several options exist.
From the originalcheckvalve
.

Force main Modification

The lift station consists of a 8' x 40' Wet well containing two
Fairbanks Morse 4" 5435 MV w/ 12.6 Impellers discharging through two 6"
American Flow Control 50-SC Check Valves to a 10" C-900 Force main.There
are 5 separate ARV's located along the 5,600 ft force main at various
locations. The over all elevation change from the pump station discharge
to the discharge into the gravity system is around 113 feet.  


  Good
Morning thinkers :) I wanted to give you some of the technical blah
blah before I got started with the question.  I am currently working on a
project that has experienced 4 separate force main failures. The
failures being broken 10" pipe. The fractures have been along the pipe
and never at the bell. (That's right not the bell) The splits are always
located on the bottom of the pipe. The pipe that was removed was sent
to private labs to test and the pipe is fine. The second thing that was
done was the 3 ARV's located closest to the pump where replaced do to
excessive debris. (Municipality maintained) (sheesh).

A monitor
was placed at one of the ARV manholes and we sat on it for one month.
The measurements never got over 85 PSI. The employer is wanting to have
(GA) soft close check valves installed in place of the AFC 50-SC's and
two additional inline check valves (Also GA. The pumps will be pulled
and new 13.74 Impellers will be fitted. I personally feel like the
Inline check valves are over kill because I feel the issue was located
in the poor maintenance of the ARV's. How ever. My question is do you
think that the addition of the inline check valves coupled with the head
pressure will pose a problem for the pumps even with the New Impeller
size.
You didn't mention the working pressure allowed on the pipe.  Long
splitting would tend to point to radial pressure, rather than
longitudinal stress being the cause, which I would presume would
manifest as joint separation.

If that's true, then one might also
suspect high transient pressure spikes too fast for an unspecialized
pressure monitor to catch.  Well, that's my best guess and I'll stick to
it until proven otherwise.  I would point to a cause by air in the
line, esp. given you've had
ARV problems, the air compressing and
driving water columns rapidly when demand is quickly increased
downstream, perhaps enough to cause high velocity head pressures when
the rapidly moving water colums eventually come to a stop again.

Can
you check to see if the breaks were in conjunction with a pump start or
stop, or a major valve opening or closing quickly, each of which would
also indicate transient pressure causes, but not from air entrainment,
just fast velocity changes in the piping. 

I would tend to think
that inline pressure-balancing check valves would be more effective on
pump starts and valve closings rather than compressed air driven
velocity surges, which in that case, you should think about doing more
maintaining on those ARVs.  
Regarding "Isn't starting and stopping against a slowly closing/opening
shutoff valve much more reliable and cost efficient than taking a 5%
power cut over all operating ranges caused by use of a VFD?"

If
the piping is not designed for the anticipated operating pressures, he
may be forced to use a VFD in order to control the pressure spikes

A
force main is normally pumping sewage not clean water. It will be
difficult to find a slowly closing/opening shutoff valve that is
suitable for such sewage service. Such a vlave is normally used on clean
water service without problems.

I would expect that this installation also has a standby power system.

From the originalcheckvalve
.

Additional Cost for Fugitive Emission Requirment

Any idea about the expected % increase in valve prices as a result of compliance to ISO-15848.  
 please note that ISO 15848 standard consists of two parts: part 1 is about valve design qualification by means of type tests, while part 2 deals with production testing (of valves whose design has already been qualified to part 1).

         Obviously,
maybe you can save money (and time) if you buy valves(ball valve) which have been
qualified already (if they have to type test frome the beginning, they
will try to charge the type testing costs, or part of them, to you...),
so that you may want production tests only, that are much simpler and
cheaper...!
I doubt there exists any such thing before you make it yourself for your
own variabel conditions, every one of them changing constantly over
time.

variabels being such things as:
valvetype
pressure class
fluid
material
location
competition
etc
etc.

I
am not sure there even is a large difference if the valve else requiers
a certain quality level, or if your company has a first class
experienced purchaser....

However I think I see the reason for
your question. Best way would probably be to ask for bidding or
preliminary pricing for full qualified valves and a possible discount,
if any, for valves without this issue. A full test certificate point for
each valve less could possibly be part of such a discount, but you will
have to ask!
From the originalcheckvalve
.