12 B ULK D ISTRIBUTOR
Product Transfer Technology
July/August 2018
The oil-free reciprocating piston compressor is often the best choice for the transfer of a wide range of industrial gases, from ammonia to vinyl
chloride, thanks to a design (left) that protects the commodity being handled while controlling leakage
Transfer
policy
Reciprocating piston compressors are ideal for use in many
industrial gas transfer applications, but only if the best
solution is selected for the specific operational parameters.
Glenn Webb offers a guide to that selecting process
Suppliers should ask customers to complete a Data Sheet that details the specific operational conditions
O
il-free reciprocating piston compressor technology is just
like any other. It only achieves its desired affect if it is
used in the proper applications and, then, only after the
proper amount of consideration and study has been
performed before the final choice is made.
In other words, there are no cookie-cutter solutions for any
applications that involve the handling and transfer of industrial
gases. Therefore, making assumptions based on past experience, or
what the other guy is doing, can only get you in trouble.
In order to help ease the burden of selecting the proper
compressor technology for the handling of industrial gases, this
article lays out a general framework that can be used to help the
end user identify and select the proper solution for all of his unique
applications.
Know your application
When a customer calls and says he has an application where he
needs to move some product – which, in the industrial realm, can
easily mean anything from ammonia to vinyl chloride – the first job
of the equipment supplier’s application engineer, and his overriding
priority, is asking the most obvious question: is this even a
compressor application?
Attempting to define the application requires the operator to
explain what needs to be accomplished through the product
transfer process. Only after the parameters of the operation are
established will the application engineer know if a compressor is an
appropriate technology for use in completing the process.
Generally speaking, there are typically three product transfer-based
applications that will fit into the sweet spot for compressors.
• Vapour recovery: This process involves the capture of gases that
remain in a storage vessel that would, in years past, have been
vented to the atmosphere. Today, these gases must be recovered
due to stricter environmental and safety regulations or economic
considerations since gases that escape into the atmosphere can
also be quite valuable. Typical examples where vapour recovery is
used are for liquefied gas vapours remaining in a vessel after the
liquid has been transferred out, natural gas vapours in stock tanks,
sulphur hexafluoride in electrical transformers, seal leakage from
process compressors in larger plants and the emptying of storage
vessels prior to their maintenance, reconditioning or replacement.
• Pressure boosting: This consists of moving a gas from one location
to another. This is accomplished by boosting the gas pressure to a
level that allows it to be transferred to another storage tank
location or process for use at that higher pressure. A simple
example of this would be a nitrogen boosting system that lifts the
pressure of nitrogen gas that is stored at 125 psig (8.6 barg) to a
boosted pressure of 300 psig (20.6 barg) in order to meet a
customer’s process demands. Pressure boosting can also be used
for the transfer of refined natural gas from a low pressure
distribution line into a storage tank that feeds a burner in a heat
treating process. Compressors excel in the pressure-boosting
process because they can handle a wide range of pressure-
boosting conditions.
• Liquefied gas transfer: This operation generally takes place during
the loading, unloading or transloading of railcars and can involve
both liquid transfer and vapour recovery. Common produc