In your COMPANY as per written approved procedures endorse by your bosses,Typically, Whip checks are designed for use on air hoses at pressures of 200 PSI or less. Hydraulic oil is non-compressible and therefore, for the most part, does not induce hose whip during a coupling or hose failure (The real danger in these cases is high pressure oil being injected into a worker’s skin or eyes).
A suitable safety device for these applications is a solid guard between operators and connections). Whip checks are designed with a 5 to 1 safety margin at 200 PSI (meaning they have been tested at 1000 PSI). At 300 PSI that margin drops to 3 to 1. Manufacturers of whip checks have their specific recommendations for how to use their products including product limitations. Whip checks that do not have the appropriate safety factor for a particular pressure system should not be used. To ensure that the correct whip checks are available for your specific project, some key information is needed.
Know the specific size requirements: Typically, this means knowing the inside hose diameter (I.D.) as well as the outside diameter (O.D.) of both ends of the hose. Also it is important to know the overall length of the assembly required. What is the temperature range of the media (product) that is flowing through the hose assembly? It is also useful to having an understanding of the temperature range of the environment that surrounds the outside of the hose assembly. It is important to know how is the hose assembly is actually being used. Is it a pressure application? Is it a vacuum (suction) application? Is it a gravity flow application? Are there any special requirements that the hose assembly is expected to perform? Is the hose being used in a horizontal or vertical position? Are there any pulsations or vibrations acting on the hose assembly? Is the system a hose-to-hose connection or a hose-to-tool end configuration? What is the media/material that is flowing through the hose assembly? Being specific is critical. Check for: Abrasive materials, chemical compatibility, etc. What is the maximum pressure including surges (or, maximum vacuum) that this hose assembly will be subjected to? Always rate the maximum working pressure of your hose assembly by the lowest rated component in the system. Of course it is imperative to know the coupling system for the hose connections. Are they the proper fittings for the application and hose selected? Whip checks come in a variety of materials ranging from natural fiber and synthetic materials (i.e. polypropylene) to stainless steel cables. Similar to all types of controls for worker safety, using the wrong type of equipment can be just as dangerous as if no controls were applied. A false sense of security may result in injury or death when persons reduce their level of caution as they believe they have effective safeguards.
Government Agencies in Canada have standards and use of whip checks base upon
Restraining hoses and piping Hazards associated with hoses or piping and their connections operating under pressure are mainly the result of failures caused by leaks, pulsation, vibration, and excessive pressure. Besides the damage resulting from the release of high‐pressure gases or liquids when a vessel or pipe ruptures, fatal injuries can result from the blowout of gauges and valves, and the uncontrolled whipping actions of pipes, tubing, and hoses. In those cases where failure or disconnection could cause movement that endangers workers, the hoses or piping and their connections must be restrained .
Methods of restraint include wiring together hose connections, clamping or bracketing pipe sections, and securing restraint cables at the ends of hoses or pipe that function as loading spouts. For hoses or piping systems and their connections operating at working pressures of 2000 kilopascals (290 pounds/square inch) or more, an alternative practice is permitted. This alternative requires the employer to ensure that the hoses or piping and their connections are designed, installed, used, inspected and maintained in accordance with the manufacturer’s specifications or specifications certified by a professional engineer. In cases where this provision is used, the employer will be expected to have a copy of the appropriate set of specifications readily available at the work site for inspection by workers or an officer. Inspection and maintenance instructions are expected to include pass/fail criteria for the particular part or function inspected, as well as inspection and maintenance intervals. The employer should be prepared to provide workers and officers with documentation showing that the inspections and required maintenance were performed as required and that any substandard conditions were corrected.
Restraints function to reduce movement of pipe and hoses in the event of a pipe, hose or fitting failure. They are a mitigation tool that can be used to minimize or restrict damage to personnel and equipment from piping, but they are not capable of restraining every fitting that may break free during a failure event. Restraints are not a substitute for good integrity management practices including proper design, iron management, proper pipe support, and pressure testing.
Even with excellent integrity management practices, risks must be identified by each operation prior to starting work, and tools used to mitigate risk must be in place. Where mitigation steps are appropriate to reduce the risk associated with a particular operation or procedure, restraints can be used as part of an overall plan which uses other mitigation tools such as No-Go Zones. The end result of using a combination of tools is to eliminate the risk or reduce it to as low a level as practically feasible. When this practice is used correctly, the following questions should be able to be answered:
· What forces will be generated by a pipe failure and will the force be sustained or momentary?
· What risk level does the operation pose?
· Does the service provider’s track record add additional risk?
· What mitigation steps can be used to reduce risk?
Measure the risks!
Some restraint practices should be avoided completely. They only appear to be safe but do not provide sufficient protection or are not designed for the application. You do not want to create a false sense of security by using the wrong restraint equipment. These include:
· Don’t use whipchecks on pipe, regardless of the pressure. They are designed only for hoses.
· Don’t use stakes only (without pipe clamp) crossed over pressurized pipe. They can easily separate from the pipe in a failure event.
· Don’t use T-posts with some kind of attachment to pressurized pipe. They can easily separate from the pipe in a failure event.
· Don’t use concrete block anchors that do not have a channel for the piping. This results in elevation of the concrete block on wood shims, which negates their restraining effect. If you are using concrete blocks on wood shims, utilize a restraint to secure the block to the piping.
· Don’t stack items on top of concrete block anchors as these items can become projectiles in the event of a line separation.
· Don’t use chains, as they are not designed for use as restraints (exceptions exist, but design of chain for application must be verified).
When restraints are utilized on pressurized piping and hoses, they must be engineered to withstand the anticipated force encountered during a failure. They must also be attached to equipment and/or supports that can withstand the forces that will be put on them. Users of restraints should be careful to avoid assuming that their restraint systems are sufficient merely because they resemble other restraints seen in the oilfield.
Location Requirements: On straight pipe runs, restraints must be installed across each hammer union or other connection. On each 90 degree turn, a restraint must be across each turn, and anchored to the nearest solid anchor point to minimize lateral movement if a failure of the targeted tee should occur. Restraints are permitted to be anchored to the flanged connection on the frac tree or wellhead. Slack in restraints must be minimized as much as practical while still allowing for assembly of the hammer union or other connection covered.
Sling Type (Soft) Sling restraints are intended for use with high pressure systems including energized applications. Depending on the specific design, these restraints include soft slings that wrap around the pressured piping, and anchor points, and may utilize sling connections or spines. The two major types are rib-and-spine or an ongoing link-to-link). Sling restraints are designed to absorb the kinetic energy from moving pipe where rigid systems would otherwise break. Critical aspects include:
· Intended for hard pipe, not for use with hoses.
· Must be specifically engineered for system pressures and forces.
· Correct installation of the system is crucial, and sling slack must be minimized throughout the system. · Maintenance program for sling quality is critical.
· Chemical corrosion of slings should be avoided.
Cable and shackle restraints consist of a “shackle” or clamp located on both sides of a pipe connection, with a cable or wire rope securing the two shackles together . Critical aspects of this type of restraint include:
· In order for the shackle/clamps to work correctly, they must be tightened adequately onto the pipe to prevent the clamp from sliding.
· They are designed for specific force/pressure ratings. If used beyond their rating they actually increase risk by becoming potential projectiles in the event of a pipe or fitting failure. The manufacturer’s intended design must be confirmed in order to use.
· A point for regular tie down is also prefereable, as seen in the pipe bolt down in the picture to the right
Whipsock restraints consist of twisted strands of metal wire that wrap around a pressured hose (like a sock) with eyes hooks on the connection end that secure to anchor points. The sock diameter reduces when the hose is forced away from the anchor points (coupling failure), tightening around the hose and restraining it from movement. Critical aspects include:
· Intended for use with pressured hose lines.
· Require anchor points for the whipsock eyes.
·They can be used on hose to hose connections or hose to pipe connections.
· Whipsocks are preferable to whipchecks as they can significantly reduce the area of potential movement of a hose during failure compared to a whipcheck.
· Whipsocks are preferable to whipchecks as they can restrain a separation of the hose from an end fitting. A whipcheck may not restrain in this scenario.
Whipcheck restraints consist of a steel cable with loops on each end that are positioned on both sides of a hose connection in case of coupling failure. Critical aspects include:
· Intended for use with pressured hose lines. Not intended for use with hard pipe.
· Installation must minimize the amount of slack in the cable as much as possible.
· Although whipchecks minimize the area which the hose can whip around upon failure of a coupling, they do not completely restrict movement. This may result in injury to personnel located along side it during an event.
· Whipchecks are typically designed with a 5 to 1 safety ratio, which often limits them to lower pressure operations.
· Whipchecks must be used for their designed purpose and rating, and the whipcheck design specification must be documented.
Anchors are intended to be used in conjunction with restraint systems. Common designs include deadmen anchors, clamped-stakes anchor, concrete blocks, and helical anchors. They should be installed and placed based on spacing from engineering calculations or guidelines for the expected forces to be encountered.
Deadmen anchors normally have 3-4 expandable wings with a pointed-end structure that bites into the soil for maximum grip. Deadmen anchors shall be installed in accordance with API and IADC recommendations and applicable state and federal laws.
Clamped-stakes anchors are made of two stakes that are connected together via a clamp fitted around the pipe that is being secured. Stakes alone do not suffice as anchors. Engineering calculations should be performed to ensure they will truly counteract the movement being anticipated.
Concrete block anchors must be designed to straddle or bolt onto the flowback iron and must be of sufficient weight to prevent movement of the anchor in case of a line failure. Because concrete block applications are often not designed but simply mimic other local convention, they may pose a particular hazard. All anchors, including concrete block, must be appropriately engineered for the potential static and dynamic forces in the case of a failure. Don’t use concrete block anchors that do not have a channel for the piping. This results in elevation of the concrete block on wood shims, which negates their restraining effect
Helical anchors consist of one or more helix-shaped bearing plates attached to a central shaft, which is installed by rotating or “torqueing” into the ground. Each helix is attached near the tip, is generally circular in plan, and formed into a helix with a defined pitch. Helical anchors derive their load carrying capacity through both end bearing on the helix plates and skin friction on the shaft. It should be noted that pipe restraint and anchor examples provided above are not all inclusive and other types of systems may be appropriate for use. Any damaged pipe safety restraint or anchor must be taken out of service immediately.
Forces from a failure of a pipe or pipe fitting can be highly destructive, depending on the pressure, line size and type of failure.
· Restraints must be designed and engineered to account for these high forces.
· Generally speaking, the initial rupture forces are very similar for non-compressible and compressible fluids. The forces can be determined using the table below for a number of different pipe sizes and pressures. The depicts total initial forces for a pipe that contains either a compressible or non-compressible fluid. The forces shown include a 1.5 safety factor and are a function of the pressure and inside pipe diameter. [ Pressure (psig) X Area (3.14 x (ID/2)2 (in2 ) ] X 1.5 (Safety) Example: 8,000 psig in a 4 inch nominal pipe – [ 8,000 X 3.14 X (4/2)2 ] X 1.5 = 150k-lbs.
Anyone who has witnessed the failure of an energized pipe (one filled with gas or a gas/liquid mixture) has observed that the line moves for an extended period of time as the fluid jet exiting the pipe whips it around (when unrestrained). In lines filled with non-compressible fluids there is a sudden release of pressure during failure and resulting jerk of the piping, but it almost immediately settles down. After the initial point of rupture, the energy available for continued release in a compressible fluid line is significantly greater than that in a non-compressible line. The force keeps coming. This is why energized fluids need special consideration. · For a line containing compressible fluids it is critical to limit movement of the pipe in the event of a failure, and that the restraint system used is engineered to absorb the energy from line movement. The dramatic difference in stored energy in a line containing a compressible fluid versus a noncompressible fluid. These values are based on change in enthalpy of the fluid from a standard state (atmospheric pressure and temperature) to an elevated state of operating conditions (increased pressure and temperature). This additional energy must be dissipated during a pipe failure, and the restraint system has to hold onto the pipe or hose until it is completed.
Installation of restraints on vibrating piping and hoses can result in unwanted consequences. While these are not reasons to avoid restraints, some care must be taken to learn from the past mistakes of others. In areas of high vibration soft restraint systems are often used to avoid wear or impact points. Further, where concrete blocks are used, they can be padded with foam to reduce movement and impact of the vibrating line in order to minimize wear on exterior of the pipe and degradation of the block.