Piping Design, Installation, and Pac...

1. During package fabrication, ensure no grinding dust, weld slag, sand, or rain enter the

compressor. When welding on the skid, attach ground connection close to the weld and

never to the compressor.

2. Design and install piping without low points that could collect liquids between the scrubber and

cylinder; liquid slugging can result in compressor damage.

3. Design and install piping so it does not distort cylinders and/or crosshead guides. To confirm the

piping imposes no distortion, check crosshead-to-guide clearance after connecting the installed

unit to vessels and piping.

a. No forces or moments should exist on cylinder flanges during assembly. Prying to align flange

bolt holes or “drawing down” to pull piping into position is unacceptable. Before torquing,

flange bolts should thread by hand with no flange contact. The flange gap without torque must

not exceed 0.030 inch (0.76 mm) for one gasket or 0.060 inch (1.52 mm) for two gaskets with

an orifice.

b. Thermal studies often require nozzle load limits, which are difficult to obtain for the many

cylinder/guide combinations and skid designs. Contact Ariel for limitations.

c. It is impractical to perform thermal analysis on a compressor with the cylinders considered

rigid. The Ariel bore deflection limit is 0.001 inch per inch (0.001 mm per mm) of bore diameter,

which may be used as a cylinder deflection limit.

d. Most unacceptable cylinder deflection comes from severe pipe/bottle misalignment or

improper guide preloading. It is rare for thermal loads alone to cause significant deflection, but

they can exacerbate these problems. Unacceptably high flange forces can cause:

• Low crosshead-to-guide clearance

• Low piston-to-bore clearance

• Low crankshaft thrust clearance

• High rod run out

• Possible cylinder knock

e. Most piping and nozzle failures are due to piping vibration. It is far better to design “on skid”

bottles, pipe, and bracing as stiff as possible to prevent mechanical resonance at low frequencies

where excitation forces are highest, than to design a “soft” piping system to allow thermal

growth for “on skid” piping. Consider thermal forces if using long runs of “off skid” piping. “Off

skid” piping better tolerates thermal stress limiters (thermal loops, flexible bracing, etc.)

because pulsation and other shaking forces are typically attenuated. Design piping with sufficient

size to provide equal flow to cylinders in parallel.

4. Design piping in accordance with good engineering practice and industry standards regarding

pressure and temperature rating, settle out pressures, flow velocity, pressure drop, and material

compatibility with the gas stream.

5. Provide a blow-down vent to safely relieve system pressure for maintenance purposes. Provide a

back-flow prevention check valve for any vent or blowdown line connected to a common vent or

flare header.

6. Support and clamp piping in accordance with good engineering practice. Directly attach supports

to, or directly support them by a structural member of the skid or foundation. Support from deck

plate or unistrut clamps is insufficient.

7. Use gusseted band clamps with Fabreeka or an equivalent material between the clamp and pipe

to prevent fretting and corrosion. Some engineering study providers may dictate metal-to-metal

contact. Do not use U-bolt style clamps.

8. Ensure piping rests on the support and is not pulled down by the clamp. Shim if needed.

9. Do not block access to the analyzer drive connection at the crankshaft centerline on the crankcase

auxiliary end.

10. Provide visual access to crankcase oil level sight glass and distribution block cycle indicators.

11. Before start-up, install inlet gas debris cone strainers with 100 mesh per inch (150 micron) screen

and perforated metallic backing in a pipe spool between the inlet scrubber and cylinder suction

flange. To protect the compressor cylinder, thoroughly clean any piping or vessels downstream of

the screen of all debris. Clean inlet screens regularly. Monitor inlet debris strainers by differential

pressure and clean them before differential pressure approaches screen collapse pressure. To

protect against screen collapse, use high differential pressure alarm/shutdown switches.