We recently sat down with Drew Ezell, the Flushing Division Manager within Allied’s Industrial Services Division, to ask him some questions about high velocity oil flushing and more. Mr. Ezell has worked in the industry since 2013. In that time, Mr. Ezell has learned the intricacies with respect to Lube Oil Flushing and Chemical Cleaning. His goal at Allied is to build and maintain lasting relationships with customers and focus on providing quality work, transparency, and communication.

Mr. Ezell can be contacted at or via phone at (816) 474-8040.

What is a high velocity oil flush? HVOF’s are performed to remove contaminants from piping and tubing (welding slag, scale, metal, etc.) on hydraulic and lube oil systems. This process is essential to every maintenance plan to ensure the life of the rotating equipment is extended and that costly downtime due to catastrophic failures are avoided.

What type of flushing services do you provide? High Velocity Oil Flushing, Chemical Cleans, Varnish Mitigation Chemical Cleans, Heat Transfer System Chemical Cleans, EHC Flushing, Deionized Water Flushing.

What are the typical issues you see when communicating with customers? Customers are concerned with the Oil Analysis Reports or possibly a catastrophic failure has occurred and they have decided to ask for our expert input. In many cases, production is slowed and efficiency declines because of the contaminated systems.  

How do you identify what solutions are best, depending on the customer’s needs? Everything starts with the oil analysis. Based off the findings we will ask a variety of system specific questions to narrow down solutions to the problem. Depending on the type of contamination and the oil analysis results, Allied will decide which service to employ. There are numerous situations where multiple services are performed in conjunction to achieve the most efficient results. 

How much lead time do you need to respond to an emergency situation? In most cases we can be onsite at a customer’s location within 48 hours of receiving the call.

What factors do you consider when deciding on recommending an oil flush? When should a company perform an oil flush? In the Oil Analysis, certain metals will show up indicating abrasive wear. If metal is present within the system, it can cause catastrophic failure. There are also several other indicators that show the oil is degrading or system conditions are declining. Additionally, we have to perform an oil flush during an overhaul/rebuild, during commissioning of new equipment (for warranty purposes), or in emergency situations (bearing failures). There are also situations when a flush is needed while changing lubricants to prevent cross-contamination.

What is your target flow rates during an oil flush? We want to at least achieve a Reynold’s Number (The Reynolds Number “Re” is the ratio of inertial forces to viscous forces within a fluid which is subjected to relative internal movement due to different fluid velocities) of <4000 (minimum needed for turbulent flow) or at least two to three times the normal flow rate of the system during normal operation. In many instances, we may achieve a Reynold’s Number of 15-20,000.

Why is turbulent flow so important? Turbulent flow must be achieved for the flush to be considered high velocity. Turbulent flow occurs at a high Reynold’s Number which tends to create flow instabilities and causes the oil to bounce through pipe internals and change directions chaotically. If this velocity is not achieved, then the oil moves through the piping via laminar flow and will not remove the majority of the contamination present within the system.

How do you know you’re achieving turbulent flow during an oil flush? The equipment is sized based off the pre-generated Reynolds Number. The Reynolds Number includes piping diameter, fluid temperature, linear footage, piping schedule and viscosity that are all factored in to ensure the proper Reynold Number is generated. All of Allied’s Oil Flushing Skids come with a Flow Meter installed on each skid to ensure we are achieving our target flow rate. Pump curves are available at customer request.

Flow Rate Meter Monitored While Flushing System

What is the typical process for a high velocity oil flush?  A typical HVOF includes bypassing system pumps by installing high flow external flushing pumps, heaters, and filter skids. All critical internal components such as bearings, control valves, pressure safety valves, etc. are bypassed via temporary hydraulic jumper hoses. All flow orifices within the flow path must also be removed to prevent flow restriction through the flow circuitry. Accumulators are also bypassed to prevent damage via jumper hose or blinds.

External Filtration Skid

What Specifications are you achieving for cleanliness? We base our cleanliness criteria off API 614, ISO 4406 & ASTM D6439. On a typical flush, we are trying to achieve two specifications. A visual cleanliness inspection (100-mesh screens, API 614 standard) and Oil Analysis (ISO 4406). It’s important to install screens and pull oil samples initially to obtain a baseline for the flush. For a successful flush, a screen must be installed for 1hr and at minimum be within API 614, although many customers request completely clean screens. Standard Oil Analysis requirements for Industrial Turbines is an ISO 4406, Class 16/14/11. We have the capability to perform oil analysis onsite with our laser particle counter.

Where do you install the 100-mesh screen checkpoints? In most instances, we will install screens on each of the jumper hoses that bypass all critical components. This way we can ensure all supply lines have been cleaned adequately before completing the flush. There are a few exceptions where screens may be installed on the last connection point before the oil enters the reservoir.

100-mesh screen before cleaning
100-mesh scree after cleaning

What can be done to expedite a HVOF? At Allied, we use a variety of tactics to help expedite an oil flush to include thermal cycling, periodic air purges to agitate flow circuitry, pneumatic vibrators, and soft blow hammers to help remove contamination stuck to piping walls. We also ensure we have accurately calculated the proper Reynolds Number for turbulent flow. Ensuring that our equipment arrives to a customer’s location clean is also very important. All Allied equipment goes through a strenuous cleaning process to ensure all equipment/hoses arrive onsite clean, intact, and ready for flushing.

What do you do as a company to separate yourself from the competition? We are a full turn-key service provider hereby providing all equipment, manpower and fittings needed to complete a high velocity oil flush. Our primary focus is quality service and transparency before, during and after projects. We have a number of locations strategically placed throughout the US to allow us to be more competitive with mobilization/demobilization rates. Our site leadership sends out daily updates entailing progress achieved during that shift, so everyone directly or indirectly involved is on the same page. Additionally, we are a documentation driven company. A unique procedure is created for each project to ensure everyone is on the same page before we arrive onsite.

Allied employees Mark Arellano (left) and Shawn Ellis (right) working on a turbine lube oil system

For further questions please contact Drew Enzell at or via phone at (816) 474-8040.