Reciprocating Machine Protection
Why You Should Be Monitoring the Needle Instead of
the Haystack
By:
John Kovach, President, Riotech Instruments Ltd LLP
Frank Fifer, Director of Operations, Peerless Dynamics, LLC
Jason Hoffman, Reliability Technologist, Enhanced Maintenance Solutions, Inc.
----------- RECIPROCATING MACHINE PROTECTION ----------
Riotech VTU1X
Why You Should Be Monitoring the Needle Instead of the Haystack
1
| Understanding 1X Vibration Monitoring / Riotech / (281) 292-9051
The connection between reciprocating equipment’s 1X levels and
mechanical health, or why 1X monitoring provides the best shutdown
protection available today without the added cost of nuisance trips.
When selecting technology to be used for protecting rotating equipment, the goal of most package designers
and operators is to buy something that will avoid or limit damage to monitored equipment, while minimizing
nuisance trips that reduce revenue and increase labor expenses. This paper will discuss the relationship of a
specific frequency and its association with the various mechanical processes of reciprocating equipment and
why this technology, not only increases the protection of an asset, but also minimizes costly nuisance
shutdowns. For the first time, this same technology offers operators the opportunity to implement procedures
that can catch many different changes in condition before serious damage occurs.
Understanding why 1X vibration and machine health is so integrated
The reason the claims above can be made is that there is one force generated on reciprocating equipment that
is tightly coupled to mechanical condition; the vibration force at the 1X frequency. To understand why the 1X is
so important, it helps to understand the relationship between the mechanical processes of reciprocating
machinery and 1X forces.
When it comes to understanding reciprocating compressor forces, the highest and most limiting force on the
machine is Gas Rod Load. All the components leading from the crankshaft out to the pistons see forces from
10,000 lbs. up to 210,000 Lbs. (depending on the frame size) and those forces are changing direction from 4 to
30 times per second. Those forces are contained and distributed through the cylinders, cross head guides and
frame for the life of the machine. Any changes in how those forces are contained and distributed will affect the
amount of energy in the 1X energy component, at every location on the monitored equipment.
When looking at a cylinder pressure/time diagram of a typical compressor and its rod load, based on gas forces,
the mechanical changes translating from full compression to full tension occur in 360 degrees.